+++ #690 Subject: Fuel Tank Fittings From: Russ Erb Questions for you guys who have been doing your fuel tanks: What did you use for welding flanges for the feed lines and sight tubes? The welding flanges in the Aircraft Spruce Catalog are huge. For a 3/8 pipe thread, the flange is 1-7/8" in diameter, which would put the hole unacceptably far from the edge, leaving much trapped fuel. Did you use one of these and cut off one side to get the hole near the edge? What did you use for a fuel cap and mounting flange? How did you vent your tank? +++ #691 Subject: Fuel Tank Fittings From: bearhwk27- I have not quite been there done that all the way yet, but...... Weld fittings for tank fittings. Purchase the previously mentioned fittings. Flat off one area to allow port to be lower to bottom of tank. Keep the remainder of flange at size. Flange size will minimize weld distortion and stress. On tank filler neck I am making a larger version of the above fitting. This fitting has internal threads for MS / SAE straight thread O - Ring boss fittings. Filler cap will be mating thread with O - Ring seal at cap. Cap has blade type fitting about 3 in above top of wing skin.(Blade is attached so as to present minimal surface to airstream.... Duh .) Vent hole runs down thru blade, faces forward for ram air. All is very similar to Bob's setup. Now if you make your funnel with a mating fitting that screws into the tank filler neck it becomes a one man job to hand transfer fuel via cans or solo hand pumping when in remote locations. +++ #695 Subject: Fuel Tank Supports From: Russ Erb I know at least Pat Fagan has done this. Reference the steel straps to hold in the fuel tanks. The newsletter calls for "anti-chafing mat between the straps and tank." For anyone who has already done this or has formed a plan for it, what material did you use for the "anti-chafing mat" and where did you get it? +++ #697 Subject: Re: Fuel Tank Supports From: Gary Danford On my Hatz, I used a rubber anti-chafing that I bought from Afct Spruce. It is about an inch wide channel and snaps over the "1" Stainless Steel I used to mount the tanks. The mounting in the Hatz was the same as in the BearHawk only they used Turnbuckles on the upper straps to tighten the tank in. +++ #698 Subject: Re: Fuel tank support From: Bill Cox Russ, On the T18 I used the same channel Gary mentions and it is nice. Piper used a heavy felt in their rag wing airplanes and on our Piper restorations we have been able to locate felt that weight at a fabric store. the felt is glued on with pliobond and we've never had any problems with it. The channel from Spruce does make a nicer installion & I think I will use it in my BearHawk. +++ #699 Subject: Fuel tank support From: Tim Cramb I did the same as Bill, with my Ercoupe fuel tank. Used some felt and attached it to the metal straps with pilobond (I used the small cans with the brush in the cap). It sticks well to rubber also (as in rubber strips instead of felt). I've used pilobond to attach lot's of stuff over the years....if you get some on your fingers, it rolls up real nice, like the real thing... (booger) and when flicked off your finger, it has trerrific range ;-)....besides the ole saying does apply "sticks like shit, to a Hudson Bay Blanket" +++ #701 Subject: Re: 4130 sheet From: carolfaga- One other thing, has anyone thought about putting flush fuel caps on their gas tanks? I would sure like to, but can't seem to figure out how to make it work. With only about 1/2 inch between the top of the tank and the wing skin, there doesn't seem to be enough room to incorporate a scupper, drain hose, etc, and still be able to install and remove the tanks when necessary. Just wondered if anyone had any ideas. Been catching up on the e-mail and found Russ's latest about fuel tank flanges. I had bought the Spruce flanges, and yes they are HUGE. I ended up turning my own on a lathe, look good, nice size, but haven't welded them on yet. At the moment I am planning to use the Spruce filler neck and vented cap, though I would much rather not have that thing sticking up in the airstream, course then I would have to install a vent system. +++ #702 Subject: Flush Fuel Caps, Vents From: Russ Erb > One other thing, has anyone thought about putting flush fuel caps on > their gas tanks? I would sure like to, but can't seem to figure out > how to make it work. With only about 1/2 inch between the top of the > tank and the wing skin, there doesn't seem to be enough room to > incorporate a scupper, drain hose, etc, and still be able to install > and remove the tanks when necessary. Just wondered if anyone had any > ideas. Funny you should mention that, Pat. I was just having this discussion with some other folks when I had an idea that I thought was original. Hardly so, since I found a similar statement from Tony Bingelis (yellow book, page 79), and now you've mentioned something similar. Norm brought an example of the "Lightweight SPRL Fuel Caps" (page 159, 1999-2000 Aircraft Spruce Catalog) to a Chapter 49 meeting. I was very impressed with what I saw. I don't remember all of the reasons I liked it, but it was lightweight, sealed well, and had several fool-resistant features. The mounting ring is anodized aluminum, and the recommended attachment methods are riveting (with sealant, of course) on RV type aircraft or glassing in (fiberglass tanks). If we assume the material is weldable, would it be possible to sand off the anodizing and weld it in (anybody?)? Otherwise I can install it like the RV guys do (probably best to do that before closing the tank). Of course, with a flush fuel cap, you'll need an easy open (quarter-turn fasteners) access door on the top of the wing. I'm thinking the hinge should be on the front edge so that if the fasteners failed it would stay mostly closed rather than ripping open. As for the scupper, I was thinking about welding in a short dam around the cap and attaching some rubber seals (like used under the cowling) to help seal it. I don't want metal rubbing on metal there. There's not a lot of room, so I can't say how to do that yet. At the low corner in the three-point attitude, I could weld in a tube which would run over the side and then have a polyurethane tube connected to it to some convenient drain location. The key point here is that the scupper would drain (some small amount would probably not drain, just like "unusable fuel" and would eventually evaporate) any small sloshes or overflows. If the line boy goes stupid and pulls the filler hose out of the hole and dumps on an extra gallon, fuel is going to end up on the wing and probably some inside the wing. Even so, remember that the rear spar is open to the air behind the ailerons and flaps, so there is a path for the vapors to leave. +++ #705 Subject: Re: Flush Fuel Caps, Vents From: Bruce A. Frank I am in the process of building fuel tanks for my V-6 STOL. Though my wing is fabric I wanted to make best use of the fuel bay. The top of my tank is the top of the wing, the shape of the airfoil. It kis all welded construction except for the fuel fill cap. I am using flush caps that are the style with an "O" ring that is expanded to fit the opening when the lever is flipped. I have a set of military pop up llever quarter turn types but they do not conform well enough to the airfoil shape. One of the worries of a flush cap is not fuel overflow (it just runs off the top of the wing)but water collection that goes into the tank every time the cap is opened. What I did was to drill a hole (5/32") just above where the "O" ring seals then carefully weld an aluminum tube to the underneath side. That tube goes through the tank, turns slightly and comes out the bottom edge of the sidewall. Any rain or dew that collects round the cap drains through that tube and out the bottom of the wing. So instead of half an ounce of water going into the tank there is only a drop or two. The filler neck ring is mounted from the bottom side of the top surface of the tank with ProSeal and flush rivits. Welding in this area is out of the question due to distortion of the airfoil shaped skin and the filler neck itself. I took careful time welding the drain tube to the bottom of the filler neck using a machined aluminum plug wedged through the neck to control distortion. It worked well enough that there was hardly a reshaping of the neck and the "O" ring sealed perfectly. I have seen a screw in type flush mount fuel cap system that has an "O" ring at the top of the caps flange so there is on area for water collection, but I saw them at SNF a few years ago and haven't seen them since. It seems the Bearhawk would lend its rivited wing design to a similar fuel tank that has an airfoil top that is rivited together like the F. Atlee Dodge Piper tanks(rivited together with a mounting flange). +++ #709 Subject: Fuel Tank Vents From: Russ Erb I forgot to add this in my last post. See page 79 of the yellow Bingelis book. When installing the vent line in your fuel tank, run the vent line inside the tank to the opposite top side of the tank. Look at the pictures and you'll see how this will keep fuel from running out the vent when the tank is full regardless of attitude. This design, plus parking with the fuel selector in "left" or "right" (i.e. not "both) will keep fuel from running out the vent even if you are parked on unlevel ground. +++ #713 Subject: re radials From: stephan pelgar last night i looked at our fuel tanks on the planes.they run the vent pipe from the top front of the tank to the lower aft edge of the wing.they dont use ram air but they also have large fuel pumps on the engine.the vent was flush with the bottom skin and had screening to keep things out of the piping. +++ #726 Subject: Re: Fuel Tank Vents From: pat faga- Thanks for all the replys, perhaps I should have been more specific with my question. I too liked the fuel cap Russ mentioned and saw no problem with welding the flange in the tank. I planned a fuel door also, so rain water through the cap would not be a problem. My problem is how to do a flush cap and still be able to install and remove the tank whenever I wanted. I looked at a fellow EAAr's project where he installed a flush cap fuselage fuel tank behind a filler door. After installing the tank, he built a scupper out of composite flocking that he pressed against the tank and structure, working through the access door. He then ran a drain down through the bottom of the fuselage. Once the flocking dried, he could drop the tank down to remove it. It was a neat idea, but I'm not sure it will work on the Bearhawk, since our tank needs to be twisted into position, instead of just rising up to meet the flocking. The drain tube could be routed above the tank, attached to the rib and dropped through the bottom of the wing outside of the large fuel bay panel. Maybe I'll try putting a scupper of clay on the top of the wing and see if it can still be rotated into position. This leads me to the next question. How scary would it be to simply eliminate the scupper? Since the back of the wing is completely open, would it be safe in the case of an accidental overfill? Is there a compressible, fuel resistant material that could be bonded to the either the tank or the wing skin that would seal out leaks and act as a scupper when the tank is installed? Lastly, the vent, I would design it ala Bengellis, but would like to route it similar to a C182. Cessna has a curved tube exiting the bottom of the wing, just behind the strut. I suppose this provides some ram pressure while also providing some protection for the vent. The problem is again how to run the vent line. Perhaps use an AN fitting on the tank to the vent tube. The overboard vent could then be attached and run outside the fuel bay before replacing the cover? One last thing, since the tank is suspended, and the fuel line is fixed in the fuselage, how do you get from one to the other? Should a rubber hose be used, and where, near the tank or near the fuselage? We have about 10 inches to bridge as we pass through two ribs to the fuselage. Should the fuel tube through those two ribs be rigidly attached or should it pass freely through large rubber grommets? I have enjoyed the radial engine brainstorming. I have no intention of trying to change Bob's design, but man, do I love radials. Wouldn't that be something! +++ #728 Subject: Re: Fuel Tank Vents From: Russ Erb > Lastly, the vent, I would design it ala Bengellis, but would like to > route it similar to a C182. Cessna has a curved tube exiting the > bottom of the wing, just behind the strut. I suppose this provides > some ram pressure while also providing some protection for the vent. Pat--before you try such a design, do some research into the Cessna service bulletins and ADs. Gary Aldrich has a 180 with the type of vent you describe. I don't know the details, but he has said that there are several service bulletins on these vents. As best I remember, the positioning relative to the strut is rather critical and icing can be a problem. I can't really explain why these would be problems, but it sounds like it would be worth some investigation before blindly copying it. As for a fuel resistant, compressible material for a scupper, consider baffle sealing material. Just a thought. +++ #729 Subject: No Subject From: Bill Cox I guess I haven't studied the tank wing relationship close enough because I had assumed it would slide straight up into place. On my T18 the tank has to be twisted in place. I built a small scupper around the filler neck and drained overboard. The scupper seals against the top skin with a foam gasket made from automotive store gasket material. I think I,ve had to reseal twice in 20 years of flying and its just a matter of pulling the old deteriorated gasket material out through the acess door and gluing a new 1 in its place. Since the tank is in the fuselage a good seal is essential. On the T18 it is easy to look into the tank as you fuel so it is almost never run over. On a high wing I find it much easier to run over a little especially on cross country where you're trying to squeeze in all the fuel possible. I would try to develop a system to keep any overflow out of the wing. The vent line could be attached to an AN fitting or the vent tube could be welded to the tank with a short piece of rubber hose connecting to the aluminum vent tube running through the wing. Since this is a high wing tank installation with lots of head, I don't think it is necessary for the vent to pressurize the tank. High wing Pipers (PA 16 and later) are vented through a baffled cap. It is important that the vent doesn't end in a spot that might siphon fuel. Run a 3/8 aluminum tube from the tank to the butt rib. The attachment from the wing to the fuselage is with a piece of rubber fuel line clamped to the aluminum tubes. +++ #731 Subject: Re: Fuel Tank Vents From: Gary Danford Somebody, I don't remember who sells a rubber donut that fits over the fill tube neck and between the top of the tank and the outer wing skin. It works perfect to keep fuel from getting in the tank bay. Fuel particulary auto fuel in a scupper or the tank bay is a BIG mess. +++ #788 Subject: Stiffening Fuel Tank Sheets From: Russ Erb A while back, Pat Fagan posted the following: > 1) Even with careful welding, he still got distortion on the large > flat areas of the fuel tank. He was able to eliminate a lot of it on > subsquent tanks by rolling a bead in the metal along side the rivet > line. I plan to do the same thing, but will also run some V's on the > end panels, and X's (like on a jerry can) on the bottom panel. Now that I think I may have found someone with a tool that can do this, and since I'm working on the tanks now, this caught my attention. Pat and Mike, could you please elaborate. I'm thinking this was done on all surfaces except the top, since the top is not flat. Could you please tell me where you ran the beads and if they were effective? +++ #791 Subject: Re: Stiffening Fuel Tank Sheets From: Mike Meador You can roll a bead on the top also. Bob did this with the last set of tanks that he made for Proto II. It really works great - don't over do it. I'll see if I can find some photos and get them out to you. If I remember correctly, Bob rolled 4 beads on the top along each side of the baffle ribs, same on the bottom. A single bead along each end in the middle (longways). I don't recall what he did to the front and the back. I'll check with him. We might get this in the next issue of Bear-Tracks. +++ #792 Subject: Re: Stiffening Fuel Tank Sheets From: bearhwk27- > In the past when I visited Bob I had a chance to see the tank beading. The beads are about .5 wide X .080 deep, ends are typical full radius spherical. Beading was done parallel to tank baffle on each side. Distance from CL of baffle to CL of beading about 1.25 in. The radius from tank surface to beading depression was "generous". Beading was terminated about 2.0 in from the front and rear of the tank. Beading on top and bottom of tank. Beading was depressed into the tank. Ends of tank I did not take note, above should be typical. All dimensions via eyeball. The beading does an excellent job of minimizing the weld distortion and yields a very professional looking tank. +++ #795 Subject: Don't forget the other two books! From: Russ Erb I've haven't been looking at the Firewall Forward or Tony Bingelis on Engines books lately since I'm no where near putting in the engines. However, I happened to look at Engines last night and noticed it had a section on aluminum fuel tanks. Both books have sections on fuel systems, so it would be good to review them before you get to doing your wing tanks. Just a reminder. +++ #797 Subject: Re: Composite Fuel Tank? From: budd davisson Bob brings up an interesting point for discussion. Glass tanks build much faster, although to give the same strength are probably heavier unless using Kevlar or carbon fiber, in which case they get really expensive fast. When we did the Wedell-Williams racer replica we had two 60 gallon tanks right behind the firewall, which was a little scary. So, we built them up using blocks of fire surpressant foam as the mold and just laid up the glass around the blocks. This was the expanded aluminum type foam which required us to flush them really well, when finished, but they gave us no problems whatsoever in use and they went together like greased lightning. If someone is good at aluminum welding, an aluminum tank probably looks easy. To the rest of us, it's a daunting task. +++ #806 Subject: Re: Tank construction From: Bill Cox Has anyone thought about using rivets and Proseal. As Bob shows it the tank is riveted and welded. There are thousands of airplanes flying with tanks riveted and sealed. My neighbor's RV3 endured over 1100 hours of car gas and aerobatics before it suffered the first small leak in it's riveted and prosealed tank.I am still thinking I will weld the tanks, but after watching an RV tank being completed in one day I might be convinced to change my mind. I know Bob's tank has to be strong with the rivets and welding, but look at a Piper or Cessna welded tank, there are few if any rivets and the weld is on a small flange turned to the outside and welded. Even in 50 year old airplanes they rarely leak. +++ #807 Subject: glass tanks From: dean robert cramb I built my tanks in my Montana coyote from glass. I have a fab shop with all the equipment to build alum. tanks but decided to use glass for two reasons. To utilize all the space available for fuel,and use the tanks as a structural member.I also built a Draggonfly and know all the problems with foam-fiberglass tank construction,and did not use that method. It's not cheap but makes a good tank that is easily modified. I built race cars for 20 years and would not recommend a beginner welding something as important as fuel tanks.I know that there are lots of people out there that have more than enough talent to accomplish the welding, but to weld thin alum you should have a good ac machine with high frequency and a foot regulator.Not a buzz box. If anyone is interested I photographed the glass tank construction and would be happy to share. +++ #808 Subject: Re: Tank construction From: Float-by Shooter > I know Bob's tank has to be strong with the rivets and welding, but > look at a Piper or Cessna welded tank, there are few if any rivets and > the weld is on a small flange turned to the outside and welded. Even > in 50 year old airplanes they rarely leak. I may have misinterpreted Bob's instructions, but my understanding is that the rivets serve mainly to hold the tank together while it is being welded. And since the rivets themselves are welded, what you will have in effect is a series of spot welds holding the baffles in place, and with the welded seams the rivets are probably overkill on the end plates. My guess is that piper and cessna each probably had some sort of permanent jig to hold the pieces of aluminum for their tanks together while they were welded, so they wouldn't have needed the rivets. +++ #810 Subject: Re: tanks From: budd davisson Anything is possible, but you'd never find one with the right shape to utilize all the space in the wing. George Evans in Scottsdale, AZ has specialized in making aluminum aircraft tanks for decades. Just for the heck of it, we should send him a drawing and ask what he'd charge if he was making three or four sets at a time. Is there anyone out there who can shrink the drawing via Xerox and fax it to him? If there is, I'll call and give him a heads up. > Would it be out of the question to modify a small aluminum auto gas > tank? +++ #811 Subject: Re: tanks From: Bob Romanko > Would it be out of the question to modify a small aluminum auto gas > tank? I imagine the odds of finding one that would be the right size and shape are about a million-to-one. By the time you reworked one, you probably could have built a tank from scratch. I'm still leaning toward glass, although I'm a long ways off from my fuel tank. +++ #817 Subject: Re: tanks From: Float-by Shooter Does anyone know how much David Spencer charges for a set of Bearhawk tanks? +++ #822 Subject: Re: tanks From: budd davisson Tanks and all that. The best tanks available are the ballistic kevlar jobs made in NJ (I forget the company). They do most of the race car stuff. I visited them when we were building the Wedell racer and learned a lot. We patterned a lot of what we did after them. Including flexible connections. with the tanks in the wings of the 'Hawk I don't know that I'd worry about quick disconnects, but if an aux goes in the fuselage, it would sure as hell get quick disconnects. +++ #837 Subject: fuel tank build estimate $ From: robert gaddy I took up Budd's suggestion and gave George Evans, in Scottsdale AZ a call. He will make an estimate for fuel tank construction. In our initial conversation he pointed out that there is no drain in the tank. I don't know if one is needed with the water trap at the low point. By the way, how do you access the water trap, get on your hands and knees? +++ #838 Subject: Re: fuel tank build estimate $ From: budd davisson George Evans is one of the top craftsman of our time and stands behind his work. I recommend him highly. +++ #840 Subject: fuel tank build estimate $ From: Russ Erb > I took up Budd's suggestion and gave George Evans, in Scottsdale AZ a > call. He will make an estimate for fuel tank construction. In our > initial conversation he pointed out that there is no drain in the > tank. Wrongamundo! In the April 96 Bear-Tracks the drawing of the tank is very specifically labeled "1/8 NPT on bottom corner for quick drain" Yes, you need a drain in the tank. It's best to get it out before it gets into the fuel lines. If it wasn't a good idea, why does every production airplane have a drain on each tank (some have several on one tank). +++ #841 Subject: Fuel System Drains From: Russ Erb Okay, I'm surprised. Below is the text from Part 23 concerning fuel drains. Yes, homebuilts are not required to conform to Part 23, but it's generally a good idea. Note that only one drain is REQUIRED. I still think a drain on each tank is a good idea. Forgot to say before, on the prototype the gascolator drain extends through the bottom fuselage skin. Sec. 23.999 Fuel system drains. (a) There must be at least one drain to allow safe drainage of the entire fuel system with the airplane in its normal ground attitude. (b) Each drain required by paragraph (a) of this section and Sec. 23.971 must-- (1) Discharge clear of all parts of the airplane; (2) Have a drain valve-- (i) That has manual or automatic means for positive locking in the closed position; (ii) That is readily accessible; (iii) That can be easily opened and closed; (iv) That allows the fuel to be caught for examination; (v) That can be observed for proper closing; and (vi) That is either located or protected to prevent fuel spillage in the event of a landing with landing gear retracted. [Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as amended by Amdt. 23-17, 41 FR 55465, Dec. 20, 1976; Amdt. 23-43, 58 FR 18973, Apr. 9, 1993] +++ #846 Subject: Re: fuel tank build estimate $ From: zippydog- I stand corrected on the drain on the fuel tanks. It is called out on the tank plans. It is noted in an area that I didn't expect to see it. The arrow on the call out appears to be pointing to outlet #1, but is rather pointing to an undrawn feature. +++ #1052 Subject: composite tank pics From: Float-by Shooter For anybody who might be interested, I just added pictures of Dean's composite tank construction to the FAQ webpage. +++ #1279 From: Bruce A. Frank I thought the group might be interested in the welded aluminum tanks I am building for Corky Scott for his Christavia MKIV. The tanks will have a flange extending two inches beyond the edge visible here. That flange will allow the tank to be screwed down as if it were a tank cover on a Piper short wing. There will also be tabs added to the sides and bottom to allow bolting and standoff to the spars and the shelf under the tank. The filler cap is flush. To overcome the tendency of dumping an ounce or so of water into the tank every time the cap is opened I designed a drain tube that is welded into the filler neck from the underside just above where the "O" ring seals. A small drain hole goes through the filler neck into the drain tube which goes into the tank and exits the end of the tank . This does a couple of things, it gives the drain for rainwater buildup, it helps to carry away over filling fuel rather than running it out on top of the wing, and it prevents the filler cap scupper from being a low pressure area that might siphon fuel out of a loose cap. The top of the MK IV closely matches the USA35B airfoil of my wing on my V-6 STOL. Several years ago I made a 1/2 inch steel template for the ends and baffles for a tank I wanted to build for myself. This tank is built from .065" 5053 aluminum sheet cut to be 1/2 inch larger than the pattern. The shaped piece is clamped between a hardwood plywood blank and the steel template then the edge is folded over, with a soft hammer, to form a flange. (similar to the way the Bearhawk wing ribs are formed) The bottom, front and back are one bent piece. The top sheet has been rolled slightly to give it a little crown to help it follow the shape of the tank ends (the airfoil shape). All the edges are clamped with Visegrips and C-clamps then tack-welded about every 1/2" to 3/4" with the TIG torch. A fine diameter filler rod was held in stand-by incase the edges did not want to flow together when they started to melt. 99% of the tacks were done without filler rod. (this required careful scrub cleaning with a fine stainless steel brush and wiping with acetone). All the flanged edges were welded by melt down only under the TIG torch. The inside corners of the ends of the tank were then welded closed as they were notched to allow the flange to be hammer formed in the template. The filler neck was not welded so to prevent warpage of the top airfoil. The filler neck was installed (from the underneath side before the tank bottom was welded on) using Pro Seal with flush pulled rivets. The tank outlet and water drain were supplied by Corky from Aircraft Spruce. The 2.5 inch diameter pad, visible on the tank's inboard end. is the mounting place of fuel gauge sending unit. This sending unit mounting point was created by drilling and tapping a 1/4" thick piece of aluminum, clamping the tank end to a table and welding around. Some distortion of the end was easily corrected with a body working hammer. The front, bottom and back flange seams were welded after this sending unit pad was welded. +++ #1282 Subject: Welded Aluminum Tanks From: Russ Erb Is the tank you describe as designed? At least two things you mentioned seem to go against "established" practice, i.e. what is written by Tony Bingelis. To wit: The tanks will have a flange extending two inches beyond the edge visible here. That flange will allow the tank to be screwed down as if it were a tank cover on a Piper short wing. There will also be tabs added to the sides and bottom to allow bolting and standoff to the spars and the shelf under the tank.< Sportplane Construction Techniques (Yellow), page 83: "It might seem like a good idea but forget it, amigo. Aircraft tanks never have tabs welded to them for bolting directly to the aircraft structure. Vibrations will usually terminate such an installation with leaky cracks or broken lugs as your reward. Fuel tanks, you will find, always are suspended or cradled in padded straps..." > All the flanged edges were welded by melt down only under the TIG > torch. Tony Bingelis on Engines, page 142: "Every instance of a cracked fuel tank seam (of those I have seen) happened because the seams were improperly welded. The welder had, in most instances, merely melted and fused the flange edges with little or no addition of filler rod. The welds generally looked beautiful with their small uniform beads..." I bring this up for your consideration. You, of course, will decide what is right for your situation. +++ #1283 Subject: Re: Welded Aluminum Tanks From: Bruce A. Frank > Is the tank you describe as designed? At least two things you > mentioned seem to go against "established" practice, i.e. what is > written by Tony Bingelis. To wit... I have all of Tony's books and am well aware of the problems of which he speaks. Tony's information is not new and, as he states it, is absolutely true. I have repaired many a tank sold by commercial operations built just as Tony described. +++ #1286 Subject: another tank question From: Float-by Shooter I was wondering if any of you with completed fuel tanks (built to Bob's design) have weighed them? I was thinking about the tanks Bruce made for Corky out of .065, and thought I might be able to roughly calculate the weight difference if one went from .050 to .065 for ease of welding. +++ #1287 Subject: Re: another tank question From: Bruce A. Frank I have done the calculation on Corky's tank. The weight of the .065" (actually it mics at .0641) tank is 11.75 lbs. The tank built of .050" (mics at .0507) weights 2.35 lbs less. +++ #1406 Subject: rib form block From: Collin Campbell By the way does anyone know of a source for the fuel caps and filler necks for the Bearhawk? Aviation Products was recommended in the newsletter, but I contacted them and they no longer sell the caps. +++ #1410 Subject: fuel caps From: Russ Erb > By the way does anyone know of a source for the fuel caps and filler > necks for the Bearhawk? Aviation Products was recommended in the > newsletter, but I contacted them and they no longer sell the caps. I highly recommend the lightweight SPRL fuel caps in the Aircraft Spruce catalog (1999-2000, page 159) They are very well made, have many cool features, and are very light compared to metal caps. They come in flush or with the threaded standpipe. Just don't ask me what SPRL means... +++ #1721 From: Russ Erb Subject: [Bearhawk] fuel tanks > What I need to know is just this: What about vent lines such as those > shown in Bengelis's Sportplane construction techniques page 79? Are we > supposed to use the cap ram air vent or the overboard vent line with > ram air or do we need ram air at all? and if so where does the line > penetrate the lower wing surface, how far below the lower surface? I'm > thinking that the overboard vent line is neater and doesn't dirty up > the upper surface. So am planning a flush filler cap as shown on pg > 78. The cap ram air vent is the easiest to construct, but you have to constantly watch that it is put on properly. Study carefully the drawing on the page you mentioned. See how the vent line exits the tank on the opposite side from where the end is. VERY SLICK way to keep fuel from pouring out if parked on a sloping ramp (a problem many production airplanes have). I'm thinking of having the open end of the vent tube at the forward upper outside corner (the highest point) of the tank (right by the fuel cap). Staying inside the tank, the tube would run spanwise toward the inboard end of the tank along the inside top of the tank, then turn back and run toward the rear lower outside corner of the tank, where it would exit the tank straight down through the bottom and out the bottom wing skin. The tube will be supported by the baffles and welding to the inside of the tank as required. Sound complicated? It is. But it has a few advantages that I like: 1. Running from the outboard end to the inboard end and back keeps the fuel from draining through the vent at virtually any attitude. See the page mentioned above to understand why. 2. Running it back to the outboard end lets the vent come out of the wing outboard of the door window. I don't want fuel possibly dripping on the door. 3. Only a small portion of the vent tube is outside the tank, so only a small portion is subject to damage. 4. It is relatively easy to make a hole in the skin for the vent tube. No additional support for the tube is required. On the question of ram air: No, you don't NEED ram air pressure. While it may help with the fuel flow, that's not the reason for it. What you don't want is reduced pressure (i.e. suction). If the vent is facing the rear, the lower local pressure will siphon fuel out of the tank (qualitatively BAD!). That's why you have to watch those vented fuel caps. Sure, you might be able to get away with something pointed sideways, but you might as well point it forward and get some help from the ram air pressure. Note that Tony recommends a screen in the vent tube to keep out the bugs that like to collect there. Another option (which fits in with my plans) is possible with a vent tube that exits the bottom of the wing straight down. I first saw this on the Piper Traumahawk that I learned to fly it. Don't bend the tube forward, but cut it at about a 45 degree angle facing forward. The angle helps to pick up positive pressure, or at least avoids negative pressure. Any bugs that come along hit it and then just fall away rather than being driven into the tube. +++ #1722 From: Collin Campbell Subject: [Bearhawk] fuel tanks I like Russ' idea about fuel vent lines. Plan to do mine in similiar fashion. I don't like the idea of venting through the fuel caps for two reasons. 1. Like was mentioned before, the chance of getting them on backwards is a real possiblility. ( I know no one would ever miss this on a proper preflight right?) 2. In flying in rain, there is a possibility of water entering this type of vent. With the vent pointing upwards and forward, makes it easy for water to flow right in. With the vents exiting the bottom of the wing, water would have to travel up to get into the tank, not very likely. The other thing I like about venting the way Russ described it is the ability to "fine tune" your system once you begin to fly the aircraft. There may be a tendency for one tank to feed at a faster rate than the other. This can be easily remedied by changing the angle of one tube. The degree of the angle controls the amount of positive pressure on the tank, the steeper the angle, more pressure. In this way you can get both tanks the exact same. An old trick passed on to me by a fellow builder. +++ #1724 Barry Schutt Subject: [Bearhawk] fuel tanks A big thanks to Russ and Collin. I have now updated my plans to include the extended vent tube per Russ's direction. I hadn't thought about the aircraft attitude when the wing tip is lower than the fuselage (sort of like that never happens---duhh!), so running the vent tube to the inboard end will solve that problem. Thanks for the quick response. +++ #1727 From: Russ Erb Subject: [Bearhawk] fuel tanks > A big thanks to Russ and Collin. I have now updated my plans to > include the extended vent tube per Russ's direction. I hadn't thought > about the aircraft attitude when the wing tip is lower than the > fuselage (sort of like that never happens---duhh!), so running the > vent tube to the inboard end will solve that problem. Thanks for the > quick response. My comments about fuel running out the vent on the ground were not from conjecture--they were from experience, albeit other people's experiences (+5 points, using "albeit" in a sentence). I've heard of planes parked on sloping ground that lose a good amount of their fuel through the vents. A buddy with a Cessna 180 says that if he takes a turn too fast on the ground, the fuel sloshes to the outside of the turn and then starts siphoning out the vent. He has to get out and shake the wing to break the siphon so that it doesn't all just run out. Not to mention having to deal with the EPA or OSHA... +++ #1728 From: Shelly Subject: [Bearhawk] Re: fuel tanks Some considerations on fuel tank venting. I would suggest you vent the R tank to the L - this is a consideration during turns. Also, consider an outboard vent for each tank. Then, when you route the fuel system down toward the firewall, consider all your angles - where does the fuel exit the tank? - is it in the back, front , or middle of the tank? What is your landing attitude? - nose down, nose level or nose up? Is there sufficient head pressure to get fuel to the engine to get it started? Do you need a small header tank close to the firewall to assure that you have enough fuel to land, no matter what your landing attitude is, (as in fuel drain aft), landing attitude nose down, or vice versa). If you do add a small header tank, don't forget to vent it back up to the fuel tank. Bruce is a good source for some of this info! And of course, the plans - if you deviate, consider the consequences, give it a lot of thought and check it out! Been there, done that! +++ #3194 Subject: Fuel Tank Filler Neck, Change 32 From: Russ Erb I can't be accused of changing the design since what I've been doing was not included in the plans. Even so, it can still be a pain... The subject at hand is how to integrate the fuel filler neck on the fuel tank with top skin of the wing. I've been through several iterations and I think I'm converging to (blundering onto?) a solution. I was trying to avoid a big cylinder hangin' in the airstream with a big honkin' cap on top of it, not to mention trying to figure out how to cut the hole for the filler neck in the right place in the top skin. For a long time I have been charging down the path of using a flush filler cap on the tank, building a scupper wall around it with a drain tube, and then using some sort of quick release door on the top skin of the wing. I have now abandoned this idea for one reason: limited space. The tank installed is about 3/8" to 1/2" from the top skin. This is not enough room to install Hartwell latches, because they would strike the tank upon opening. What about quarter-turn fasteners? Maybe, but there is not enough room for Camlocs. Dzus might work, but now you have extra things sticking up in the airstream, especially if you use the wing nut versions instead of the ones that require tools. Do you put it on a hinge (the hinge would probably make another bump where you don't really want it) or make it removable? If it is removable, how do you keep up with it? Then of course there would be the ongoing hassle of trying to explain to the line boy the non-standard procedures to get to your fuel tanks. It all just started to be too hard and too inelegant for me. Of course, I am somewhat limited in my options since I am well into buying and making parts (hard to replace a wing skin that is riveted on just because you don't like the way the hole is cut). I'll skip past the various ideas that I rejected and straight to the one that I think I'm using now. I wanted to keep the tank all aluminum if I could, using composites only for the scupper wall. I need to fill the gap that is about 3/8" to 7/16" to bring the flush fuel cap up under the wing skin. Bob Barrows used a machined part to fill this space, but I was looking for something that didn't require a $400 tool and a $50 block of aluminum to do. A doubler under the wing skin (0.032) will take up part of the space. This is primarily to strengthen around the hole, with the extra benefit of filling part of the space. The welding flange for the fuel cap will take up 1/8" of the space. For the majority of the rest, I used the leftover 1/4x0.049 5052-0 aluminum tube (from the vent tubes) bent into a circle at the diameter of the fuel cap welding flange. This tube will form the spacer and be welded to the tank and to the fuel cap welding flange. All of this should push the cap up to right under the wing skin. Any additional small gaps can be filled in with Super-Fil or micro as required. I think this will work. I won't really know until I can actually start welding pieces together. Added benefit: The fuel caps will be at the surface so I don't have to do a lot of explainin' to the line boy. A perfect seal to the skin is not required, since overflow fuel that gets down around the cap will fall into the scupper and be drained away. If the cap flange was sealed to the wing skin, that seal would have to be broken to remove the tank (if required). +++ #3437 Subject: fuel tanks From: Tim Anderson I seem to recall this subject coming up once before but it never hurts to re-hash. I know some of you have completed your fuel tanks. Did you follow Bobs gameplan closely or make changes as to flanging and welding? I am concidering flanging the end caps to the outside (rather than inside) to aid in riveting, and a long-time RV builder stated at our EAA meeting that he recommended just riveting and pro-sealing, rather then welding. He stated that welds often develop small seaps. I guess welding and pro-sealing would work but is over-kill in his mind. Flanging to the outside will limit the capacity slightly (gal or two). If one installs the aux wing tanks, Does anyone know why you would need the added vent line from aux to main tank, as Bob drew on his newsletter?. If one vents all the caps, it would seem that the vent from tank to tank is not needed. If one does not vent the aux tank cap then a vent line is needed. I'm still debating the aux tanks. More weight, more complexity, but out-and-back trips will cut ones range by half. Refueling with a can, out in the boonies without a ladder, or on floats can be a challenge sometimes. A 5 gal can is my limit, if bigger, it is too clumsy. Steps to get up on the wing to refuel for us height-challenged folks are a must (that's another subject matter). I don't plan on flush caps, good old vented caps are fine with me. KISS is my motto. Any thoughts? +++ #3438 Subject: Re: [Bearhawk] fuel tanks From: Kent White Re: tank seeps from welds That's far enough, cowboy! Piper tanks are legendary for not leaking, unless crunched---and some keep soldiering on after a crunch! They are welded and, (nontrivial point here)... of a good design. Many others also do not seep, leak, or drip. However, designs vary, and weld-joint designs vary with them. Some designs are notorious for weld-seam leaks. Including some FAA -approved mods which leak right after installation. I'd trust a well-designed welded tank buried and sealed in a wing (Hughes H1) far more than a riveted and sealed unit, anyday. ......Hmpf..... (chuckle.....) +++ #3439 Subject: RE: [Bearhawk] fuel tanks From: Bob Romanko Kent's right on (as usual...grin!) with this one, Tim. Years ago I helped restore quite a few rag and tube planes, all with welded aluminum tanks. One thing all the restorations had in common is we had to do NOTHING with the tanks with the exception of a good cleaning and exterior corrosion control. Nada, nilch, zippo, nothing. Void of activity. No muss, no fuss. A yawner. A veritable "non-issue". We're talking "sittin' on the sofa, drinkin' a beer, feet propped on the coffee table, watching The Spirit of St. Louis" nothin. And this non-activity was on tanks that were OLDER than any of us workin' on them! If fact, now that I think about it, back then they were double my age. Nuff said. The only rivets I need in my tank are to hold it together while I weld it. I'm buying Kent's video on welding aluminum when I get to that point. Kent's brilliant, and I can watch his fuselage video a thousand times and still learn something new. I love this guy, and he writes right. If people don't have Kent's video on fuselages, they may as well turn in their torch. It's THAT good. +++ #3440 Subject: Re: aux fuel tanks From: Rod Smith > If one installs the aux wing tanks, Does anyone know why you would > need the added vent line from aux to main tank, as Bob drew on his > newsletter?. If one vents all the caps, it would seem that the > vent from tank to tank is not needed. If one does not vent the aux > tank cap then a vent line is needed. I'm still debating the aux > tanks. More weight, more complexity, but out-and-back trips will > cut ones range by half. Refueling with a can, out in the boonies > without a ladder, or on floats can be a challenge sometimes. Wow, gone Moose hunting for 11 days and come home to 160 e-mails, most from this list including the one about Bob's widow, that was a scare! I will be installing the aux tanks. My pilot friends tell me it is getting increasingly difficult to find fuel north of Fairbanks or west of the Alaska range, especially when on floats. I also do not see the need for the vent line between tanks if you vent the caps. I may keep the tanks separate, ie separate fuel lines to the fuselage to prevent the aux tank from overrunning the main tank when parked on uneven ground but I haven't thought through all the implications. My wing struts arrived while I was away,they look more aerodynamic and stronger than the Cessna struts to my untrained eye. There certainly is no better deal on struts anywhere in sport aviation. +++ #3451 Subject: [Bearhawk] fuel tanks From: Russ Erb I'm doin' my tanks like Bob recommended, rivets and welding. Rivets on about 1-1/2" spacing, which is probably way too close. Will have lots of fun welding around those. Pro-seal is installed during the riveting, so welding afterwords would burn it out! RV guys are stuck on this idea because they have wet wings and it's about the only way to do it. I don't care for sealant since I've heard way too many stories about trying to get F-16s to stop leaking. I suspect some of those fuel tanks are full of sealant by now. Flanging to the outside reduces fuel capacity (more than you might think) and also weakens the joint because the load paths are different. Instead of being in shear (good for welds) they are loaded in peel or tension (bad for welds). See Tony's books. If you install the aux tanks, keep the vent tube and only vent the aux tank. Even without the vent tube, fuel will flow out of the aux tank and possibly out the vent in the main tank cap unless you made it rather tall. Even worse on a sloped ramp. I came up with a venting system for each tank that won't leak regardless of the attitude of the tank. I've talked about it before. Pictures on CD V2 when released. +++ #3457 Subject: Re: [Bearhawk] fuel tanks From: Donald Schindler Tim, Look at how it is done on the J-3 Cubs and make it like that; flanged to the outside, beaded, and is strong. Ive seen plenty of tanks leak that are "welded over the rivets". They do fine until a few hard landings and then a leak sets up over a rivet that wasnt quite perfectly welded. The acro guys(how bout it Budd) usually have some good advice on tanks cause they go through alot of em(all those G's) Soldier on... +++ #3459 Subject: Re: [Bearhawk] fuel tanks From: Kent White Re: Welding rivet heads in fuel tanks: OOps: I erroneously mentioned 470 as the old style while meaning 455, truss-heads. Kent White +++ #3460 Subject: Re: [Bearhawk] fuel tanks From: Kent White Re: Welding rivet heads in fuel tanks: Tony B recommends welding over -4 rivet heads (1/8 dia.) for tank construction and yet I never see this on vintage/traditional workmanship. These rivets are just too small to get a good weld onto---AND--- (nontrivial point here) the shank will not be of sufficient thickness to bear the load after welding stresses have been introduced. For this reason "we" have come to accept the traditional usage of -6 (or -5) shank rivets, in the 1100 alloy, and with the old 470 head that makes welding fairly easy, if not straightforward. All leaks from rivets that "we" have seen stem directly from insufficient rivet size for the process and NOT from the process itself. Also much fewer rivets are needed, and less welding follows. +++ #3464 Subject: Fuel tanks From: Collin Campbell Just finished my fuel tanks using rivets and Pro-Seal. Flanged everything to the inside as per plans, but changed the way the top and bottom skins were applied. Made a "U shaped bottom (front and rear) all one piece. Ended up with the top to apply last. This gives a good chance to go over everything inside with the proseal before installing the top. I confess I am a former RV builder, main reason for choosing this method. I don't have a particular problem with welding for those who are so inclined, but I have seen a lot of attempts to weld tanks that were not so pretty. Pro-Seal and rivets work well, don't let anyone tell you it doesn't. Main thing is to be sure to keep everything extra clean to ensure a good seal. I cleaned everything with Naptha before hand, and avoided touching the parts with bare hands, as oils in the skin could contaminate the surface. Top skin has to be installed with blind rivets of course since there is no access. I know this will be a problem for some who prefer more "acceptable methods" but there are many RVs flying with tanks built this way that are giving good service. +++ #3730 From: Subject: New file uploaded to bearhawk This email message is a notification to let you know that a file has been uploaded to the Files area of the bearhawk group. File : /fuelcaps.jpg Uploaded by : metalfab@p... Description : Vented Fuel Caps first run! You can access this file at the URL http://www.egroups.com/files/bearhawk/fuelcaps%2Ejpg +++ #3773 From: Subject: Re: Gas caps. > So, those caps look really good! How much per set? I only get into the group a few times a week and have been gone all weekend. So here is the Offocal notice. Last week I called and talked to Bob and he was exctied that I had made a secsussful production run of his vented fuel caps. I ask if he would wanted to see one, and possible to get a digital for the next issue of the Beartracks. Bob gave a final suggestion and set things right and we now have Vented Fuel Caps. I have one more test and I'll get to do that tommarrow, and that is to weld a weld ring into a piece of .050 Aluminum and measuere the distortion. Caps won't be avalible for shipping until Bob has one in his hand for inspection and approvable. Noted feature changes, larger weld flange on the ring, and transition radius at the base of the fin. The standard method for creating the aerodynamic shape of the fin is the approved Bob hack saw and Bob file. Vented Fuel Cap price breakdown. 1.65 hours each @46.00/hr = $75.90 6061-T6 bar and tube stock ea.= $6.77 Viton large and small seals ea.sets = $5.82 So a pair will run about $176.98, plus about $5 for priorty postage and insurance. +++ #4144 From: Russ Erb Subject: Re: [Bearhawk] Re: Stiffening Fuel Tank Sheets > I was going through my "saved" bearhawk emails and noticed > this item. Any thoughts on how to "bead" the tanks? Make a > grove in a wood block and pound it in????? I used a beading roller that a friend had. The sheet is rolled through the roller and the bead is pressed in. +++ #4146 From: budd davisson Subject: Re: [Bearhawk] Re: Stiffening Fuel Tank Sheets These rollers are a standard piece of equipment in most airconditioning or metal fab shops. They'd probably bead the rough cut sheets for little or nothing. +++ #4147 From: "Kent White" Subject: Re: [Bearhawk] Re: Stiffening Fuel Tank Sheets The "bear roller", or "jenny" or rotary machine is a common choice, IF the throat is deep enough to reach across the tank surface. If no beader handy, then yes, groove a block of 2X8 fir or pine. "Beating" in the rib may encourage a slightly rougher appearance than you imagined possible, so we encourage the alternate terms "work", or "hammer", or "drive". If you are happy using the 24 oz claw hammer to accomplish this, well and good. However, another method is fun, too. Go ahead and use the .5" cold-finished mild steel round stock that you would naturally choose for the task, and having the ends nicely rounded to avoid shearing a clean slot at the end of the bead, use the 4X rivet gun to work the round bar into the grooved board beneath the panel. Make long even passes over the bar, watching how much it sinks into the material with each pass. The ends of the "graves" in the wood may be radiused to match, too. Readjust your earmuffs from time to time, listening for the neighbors' cheers from next door. I use a contact spray adhesive to keep board to bench and panel to board, neatly avoiding the fancy curved beads and language common to prewar French racing machines. +++ #4165 From: Russ Erb Subject: And just where do I get one of those! One of my pet peeves for years has been articles that say things like "...to do this operation, use a left-handed smoke shifter...". That's nice, but doesn't help when I don't know what a left-handed smoke shifter is, wouldn't recognize one if I saw it, and haven't a clue where to get one! Recently while trying to figure out how to leak check my fuel tanks, I read in several places in Tony's books that he recommended pressurizing the tank with air to no more than 3 psi. Because serious damage can be done to the tank with a little too much pressure (a little pressure over a big area equals a huge force) and most compressors and regulators are happy working around 100 psi (just a little more than 3 psi), it is very important to use a "low pressure gauge" capable of registering in 1 psi increments. And just where was I supposed to get one of those? Most pressure gauges I had seen started at around 10 psi. Gee, thanks, Tony. Then it occured to me that I've had several such gauges for years. It was not immediately apparent because it was sold as a "vaccuum gauge" for car engines. However, if you look at most vaccuum gauges, the other side of the dial is labeled "fuel pump pressure" and is marked in increments of 1 psi. Pick one up at most any auto parts store. The vaccuum gauge attaches to a rubber hose by a barbed fitting, put this is not a problem, since it would take far more than 3 psi to blow the tube off. By the way, you are going to be asking for trouble if you use one regulator to drop from a line pressure of 100-120 psi to less than 3 psi. The regulator is going to be very sensitive, with large pressure changes for very small turns of the knob. Remember if you get a little too much pressure you'll "blow up" your tank! The solution is to use two regulators in series. Use the first regulator to drop the pressure from 100-120 psi down to about 10 psi. Then use a second regulator to drop the pressure to the required 1 to 3 psi. The second regulator will be able to adjust very fine pressure differences with large rotations of the knob. Remember that the setting of the regulator to get a particular pressure will depend on how many leaks you have. With more leaks, you'll have to turn the knob in more because more volume flow is needed to maintain the same pressure. And don't think that 3 psi is required. I found that all of 1 to 1.5 psi was plenty to generate a healthy flow through the leaks, not to mention all of the pops, creaks, and groans from the tank. I calculated that the pressure of the fuel on the bottom of the tank will be about 0.18 psi, so if the tank will hold air at 1.5 psi, fuel shouldn't be a problem. Those of you who have received BHCDV2 may have noticed that I ran the vent line and scupper drain line out of the tank right next to each other. I'm beginning to think this wasn't such a good idea, and that at least 1/8" between the tubes would have been better. The problem is in sealing the tank in between the tubes. It is not possible (or at least not reasonably doable) to weld between the tubes, leaving a "sizeable" hole. I'm trying to seal it with Pro-Seal. I think I gotten the sealant worked in between the tubes, but we'll see how that goes after it cures. +++ #4167 From: n95mf@a... Subject: Re: [Bearhawk] And just where do I get one of those! > Recently while trying to figure out how to leak check my fuel > tanks, I read in several places in Tony's books that he > recommended pressurizing the tank with air to no more than 3 > psi. Russ and fellow Bearhawkers, the technique most of the RV guys use to check for leaks in fuel tanks is to put a balloon on one of the outlets, either the fuel outlet or vent line. Seal up the other outlet. Then blow enough air in to inflate the ballon. Better to inflate the balloon than deform your tank. Seal where you put the air in and wait to see if the balloon holds pressure. After a day or so, you will notice the balloon will change inflation as barometric pressure and temps change, but if you have any leak your balloon will go limp. Of course, check for location of the leak with soapy water. Easy, quick, and reliable (air is much thinner than fuel). Mark Goldberg RV-8 and Bearhawk #444 +++ $4168 From: Bruce A. Frank BruceAFrank@a... Subject: Re: [Bearhawk] And just where do I get one of those! My son plays soccer and basketball so a couple of years ago I bought a nice compact hand pump with a built in gauge, which reads from 0 to 15 lbs over about a 300 degree sweep. After playing around with regulator setups to try to get my shop air down to 3 psi, several wasted hours, I smacked myself in the forehead again when it hit me that I already had the solution lying on a shelf in my son's closet. Took all of 2-3 minutes to bring a 30 gallon Piper style fuel tank to 1.5 psi. As you said, we are just really looking for leaks and 1.5 lbs is plenty. +++ #4169 From: Russ Erb Subject: Re: [Bearhawk] And just where do I get one of those! Mark--what you say is a good final test that all leaks are sealed. In fact, I started out with a variation on the balloon theme. If you have any leaks (I had several pinhole leaks plus the aforementioned problem between the vent/drain tubes--that doesn't include the distorted fuel filler flange) the balloon will deflate pretty fast. I probably spent half an hour or more identifying the leaks on one tank, because I very meticulously went over every seam and rivet. I don't want to think how many times I would have to blow up a balloon that deflates in 10 to 15 seconds to do that test. To summarize, a constant source of air pressure (compressor dropped through two regulators) is good for finding leaks. A sealed source of air pressure (such as a balloon) is good for verifying all of the leaks have been sealed. If you think that you can weld all of the seams on the tank and all of those rivets and not leave a pinhole leak somewhere, then either you're fooling yourself or you don't understand how the system works. Maybe budd or Kent could do it, but I seriously doubt any of the rest of us could. My point is to do the best welding job you can, and then expect that you will find some leaks. Seal them by either rewelding or applying some Pro-Seal over the leaks. +++ #4170 From: "Lee H. Erb" Subject: 3 psi Fuel Tank Test It probably does not apply to Bearhawks and I do not have the latest copy of the FAA Part 23, 25, 27 or 29 but; The FAA used to require the 3 psi test as a structural test of fuel tanks. The concept was to take care of fuel expansion and clogged fuel vents. +++ #4171 From: Del Rawlins Subject: Re: [Bearhawk] And just where do I get one of those! > One of my pet peeves for years has been articles that say > things like "...to do this operation, use a left-handed smoke > shifter...". Heh, that reminds me of all the times I sent a new recruit looking for just that item in the boy scouts. One time I had a kid waste his whole afternoon looking for a Sky Hook. I told him to find one and promptly forgot about it until he came looking for me several hours later.... > just where was I supposed to get one of those? Most pressure > gauges I had seen started at around 10 psi. Gee, thanks, > Tony. I've got a special 0-8psi guage meant for checking ATV balloon tires, I think I bought it from Dennis Kirk (a motorcycle/atv/snomachine mailorder outlet). > By the way, you are going to be asking for trouble if you use > one regulator to drop from a line pressure of 100-120 psi to > less than 3 psi. The regulator is going to be very sensitive, > with large pressure changes for very small turns of the knob. > Remember if you get a little too much pressure you'll "blow > up" your tank! The solution is to use two regulators You don't have a bicycle hand pump laying around somewhere? 8^) I've got a set of videos on auto restoration and one of the neat tricks they show is how to pressure test a radiator. Instead of a balloon, they use a section of bicycle inner tube which is clamped between the inlet and outlet. I imagine you could clamp a plug in one end of the tube and the other around your filler flange.. This method has the advantage of having the schrader valve built into the section of inner tube. +++ #4172 From: Terry Turnquist Subject: Re: [Bearhawk] And just where do I get one of those! Use a bicycle hand pump to keep from over-inflating. +++ #4175 From: Joel Mayhall Subject: Re: [Bearhawk] And just where do I get one of those! Another and possibly safer way to pressurize your tank is to use a hand tire pump. Put a tire valve in the vent line or gas cap. Place your vac/pressure gauge in the supply line and pump away. +++ #4176 From: Russ Erb Subject: [Bearhawk] 3 psi Fuel Tank Test > It probably does not apply to Bearhawks and I do not have the > latest copy of the FAA Part 23, 25, 27 or 29 but; > > The FAA used to require the 3 psi test as a structural test of > fuel tanks. The concept was to take care of fuel expansion > and clogged fuel vents. Here is the applicable section from 14 CFR Part 23: Sec. 23.965 Fuel tank tests. (a) Each fuel tank must be able to withstand the following pressures without failure or leakage: (1) For each conventional metal tank and nonmetallic tank with walls not supported by the airplane structure, a pressure of 3.5 p.s.i., or that pressure developed during maximum ultimate acceleration with a full tank, whichever is greater. (2)... So, Lee, are you recommending that we test our tanks to 3.5 psi? +++ #4185 From: Leonard W. Molberg mail-to-mo@j... Subject: Re: Low Pressure Gauges Somehow, in the discussion on low pressure gauges, everyone has missed the simple "u" tube water manometer. If I remember correctly, 6-1/2 inches of water differential is about 1/4 psi (I might be a bit off) so 39 inches of differential would be about 1-1/2 psi (plenty close enough), and if you accidently get too much pressure you will blow out the water, thereby saving your tank! It also works in negative pressure situations. Anyway, a few feet of plastic tubing stapled to a board next to a yardstick is really cheap, and most of us probably have some sitting around anyway. Accurate low pressure bourdon tube gauges are expensive. +++ #4196 From: Benton Holzwarth Subject: Re: Low Pressure Gauges > Somehow, in the discussion on low pressure gauges, everyone > has missed the simple "u" tube water manometer. This was my first thought too, but the balloon idea does have a lot of simplicity going for it. > If I remember correctly, 6-1/2 inches of water differential is > about 1/4 psi (I might be a bit off) so 39 inches of > differential would be about 1-1/2 psi (plenty close enough), > and if you accidently get too much pressure you will blow out > the water, thereby saving your tank! Vacuum (~ 15psi) will lift a water column just about 32 feet, so yes about two feet of water / psi. (or 760mm of mercury (?)) A water-level is also a great trick, if you need to, say level a deck around your house, and don't have a laser in your pocket. Get a couple lengths of clear/translucent tubing, duct tape to either end of a garden hose, add water. Attach one end at your reference, and walk the other end around as you mark elevations on the posts. -- Wonder if there's applications to trammeling the Bearhawk. Which rigging measurements would be based upon a 'level'? If the landing gear is level, the wing tips ought to be at the same height. +++ #4199 From: sonny cilley Subject: Re: [Bearhawk] Digest Number 250 Hi guys, all the talk about checking the tanks for leaks makes sense but, the old tech councilors over here say that you can test them all you want and when you put in fuel the leaks will show up,so my though is why not plug the holes,and fill them to be sure. another thought comes from a friend that is building a RV -6A. he is putting some of his anteneas inside his wings,just one less thing to hang out in the wind. I know you will say the Bearhawk doesn't go that fast,but it would be one less thing to bend when getting the ice & snow off the plane. And before I forget, Merry Christmas to all you builders. I have just cut out the nose skin for the ailerons,will get the metal bent next week and skin both of them soon. +++ #4204 From: Tim Subject: Re: Low Pressure Gauges.....water level I scanned my water level apparatus and threw my laser level on the screen bed as well. it is a small file at I used this Garden hose 'water level' system for the notches in my poles that support the doubled up 2x10" x 20' headers...Got accuracy of .5mm (half the thickness of a dime). Using one pole as the master, all notches same height. It worked perfect, but I had to either top up or download the garden hose 'slightly' each time I moved it........The 3 garden hose tube/plastic screw on end attachments (with a on-off valve) cost around $10 bucks. +++ #4241 From: Pat Fagan pfflyerz@c... Subject: Re: [Bearhawk] And just where do I get one of those! In response to Russ's message about leak checking his tanks, I had an amusing story to tell. I took a TIG welding class at the local JC to learn to, hopefully, TIG weld my tanks together. There was one individual perpetually in the shop who was preparing to take his welding certification exams. I didn't much care for his personality, you know how some people just come off as know-it-alls and very obnoxious. When I felt confident enough to work on my tanks, he let me know that I would screw it up and end up with a molten pile or a potato chip. As I came to completion of the first tank he asked me how I was going to leak check it. I told him I would soap bubble it after pressurizing to 3 lbs. He advised me that I would need to pressure it to 150 lbs! I asked him where he got that number. He said 25 gallons at 6lbs per gallon = 150 lbs. I thanked him for his insight, than continued to ignore anything else he had to say. I agree with Russ that at just 1.5 to 2 lbs pressure, the tank makes enough expansion noises to scare you away from adding much more. I too used a vaccum gauge to monitor the pressure, but had no trouble adding minute amounts of air by tickling the trigger on a blow gun attached to the hose. I am now at 4 years into the construction and have been pretty consistent about logging about 600 hours a year. It took me three years to complete both wings, but only one year to just about finish the fuselage. Just finished my cargo doors, they came out fantastic. I have only to build the front doors and windows before I take it off the table for the last time and build the stringers for the top and bottom. I'm looking forward to getting into the finish work that will make the plane uniquely mine. +++ #4251 From: "Bill Cox" Subject: I am building fuel tanks. I prefer sending units and gauges to sight glasses. On many aircraft tanks the sending units are installed in the end of the tank and a common problem seems to be fuel seeps around the sender mounting area. I would like to mount the sender on the top of the tank. The problem is there is just over 3/8" clearance between the tank and the skin. All the senders I've looked at require about 3/4" above the tank skin. I have 2 ideas and would appreciate any input from you thinkers out there. I'm open to other ways of doing this. 1- Form a blister large enough to clear the sender. My thinking was to form the blister from 3003 and rivet it to the wing skin. 2- Form a depression in the tank about 1/2" deep by 3" diameter and mount the sender in this depression. +++ #4252 From: Russ Erb Subject: [Bearhawk] I would recommend option 2. It reduces fuel capacity but it doesn't change the external aerodynamics and thus cause other problems. Then again, I prefer the sight gauges, because it's tough for them to be erroneous. I'll take this opportunity to remind ya'll that a restrictor fitting should be placed in the lower end of the the sight gauge. See Bingelis Firewall Forward, page 229. This is basically a plug in the line with a very small hole to limit how fast the fuel can move in and out of the sight gauge. For the engineers out there, it stabilizes the indication by acting as a low-pass filter. For Planter Bob, the indication of fuel quantity doesn't bounce up and down rapidly as the fuel sloshes around in the tank in turbulence. +++ #4254 From: "Donald Schindler" Subject: Capacitance gauge In regards to my previous post about the fuel unit, I think the name is Skysport.(I think) +++ #4255 From: Benton Holzwarth Subject: re: Mounting of fuel sending units >> I am building fuel tanks. I prefer sending units and gauges >> to sight glasses... > I would recommend option 2. It reduces fuel capacity but it > doesn't change the external aerodynamics and thus cause other > problems. That was my first thought, to actively avoid doing anything to mess up the airflow, especially over the *top* of the wing. It did occur to me tho', that if you could turn your blister into a fairing to clean up the otherwise disruptive fuel fill cap as well, it might be a net-win. Would it be reasonable to mount the sender adjacent to the fill port? Thinking skin stress -- there's already a hole in the skin there for the filler. If opened up a bit to allow access to the sender, the whole thing -- sender and fuel filler -- could be covered over with a raised, flush and tighter fitting to the top of the gas-cap, cover panel. Maybe even a hinged panel with no exposed fill cap. But like Russ, it's sight-tubes for me. My overriding rule is "Keep it simple, get it flying." One of my favorite expressions when a new kid has a clever way to accomplish some detail at work -- "Sometimes 'better' is the enemy of 'good enough'." +++ #4257 From: Joel Mayhall Subject: Re: [Bearhawk] re: Mounting of fuel sending units No type of gas gauge is 100% full proof. I've even had cork floats loose there buoyancy. If you use an electric sending unit, just be sure to have an access panel over it. Then if you have a malfunction or develop a leak, It's easy to fix. Remember, if all else fails you are allowed to look in the tank. +++ #4258 From: Tim Subject: Mounting of fuel sending units...Capacitance Senders Capacitance senders... were popular for ultralights some years back 'Skysports' 'CPS' 'Leaf' have been selling them since inception. The beauty of these if you a purist like Bob Barrows (nay electric's) you may run one of these on a 9volt battery, similar to some intercoms....Of course they are available in standard 12-24 v systems....Current ACS catalog page 152 or much better description in Wicks catalog page 208.... +++ #4260 From: budd davisson Subject: Re: [Bearhawk] Capacitance gauge Thoughts about fuel gauges: None are trustworthy, as has been pointed out. Sending units beg for leaks so you have to be good at it. Sight gauges can also leak, but in an accident can become a major source of a leak. I once saw a little check valve in a sight gauge that came out of the medical industry. If you yanked the sight gauge tube off, the check valve would not let the fuel out. I'm a firm believer in a fuel stick or tube. 'Never had one leak or the batteries go out on one yet. +++ #4261 From: "Bill Cox" Subject: Re: [Bearhawk] Capacitance gauge Thanks for the comments. I'm a big beliver in keeping it simple, but having been at the game for a long time there are some things I want a certain way. I agree if your plan is to get airborne with minimum difficulties in the shortest time build it with no amenities and strictly by the plans. It should also be lighter and light seems to cause nice flying characteristics. I'm also looking forward to seeing all the diehards handpropping their 540s at the Fly Inns. I use a fuel stick in my Pacer, but on cross country the gauge is nice to confirm the fuel flow/hr is what I'm used to. +++ #4262 From: BruceAFrank@a... Subject: Re: [Bearhawk] sight gauge I haven't looked at their web site in a while and it is down right now for maintenance, but McMaster-Carr carries several different kinds of sight gauges that look adaptable to my fuel tank application. The part I'd like to locate is a small float ball to clearly indicate the fuel level. The clearness of the fuel sometimes makes it difficult to read the level in the sight glass (or plastic). Also, if one uses plastic tube for the sight gauge the blue tint of 100LL sometimes stains it and further reduces visibility. Does anyone know of a source of aproximately 1/8" diameter beads that will float forever in gasoline (boyh avgas and mogas)? +++ #4263 From: "David McCarroll" Subject: Re: [Bearhawk] Capacitance gauge I fully agree on keeping it simple. Sight guages are a simple way of keeping up with fuel consumption without the added complexity of wires, electric guages, circuit breakers, power scources, etc. You get my drift... As far as the batteries not going out, that's why I still use an E6B. +++ #4264 From: "Bill Cox" Subject: Re: [Bearhawk] Capacitance gauge In the mid 60's I was flying a nicely restored BC12D Tayorcraft with an A75 Continental. One afternoon I filled it with fuel and took off for a 1 1/2 hour flight to my uncle's farm. About 10 minutes after takeoff I noticed the fuel gauge ( a wire on a cork float visible in front of the windshield) was nearing 1/2 tank. Had the cork decided to suddenly sink or was I losing fuel? I turned and made a beeline back to the airport. When I got in the pattern the wire was almost on the cap. The glass bowl on the gascolator had broken and the last of the fuel leaked out as I shut down and got out to see a small puddle of fuel under the plane. The gascolator on this plane was the same used on tractors of that era, a small glass bowl with a wire bail and a thumb screw to hold it tight against the mounting bracket. Believe me, the replacement had a metal bowl. +++ #4265 From: Russ Erb Subject: Re: [Bearhawk] sight gauge > The clearness of the fuel sometimes makes it difficult to read > the level in the sight glass (or plastic). In the Feb 1995 Sport Aviation (page 101) was an idea to put alternating dark and light diagonal lines (think barber pole) behind the sight gauge. The fuel has a different index of refraction than air, so the lines behind the fuel will appear bent, and the change from fuel to air (fuel level) is far more visible. +++ #4267 From: Steve semcjm@a... Subject: Re: [Bearhawk] sight gauge It might cost you a hydrometer ( battery specific gravity checker) should holdup to fuel. +++ #4268 From: Larry "Hall Brothers" Subject: Re: [Bearhawk] sight gauge I built sight gauges for the fuel tanks in my RV-6. I used ester-based urethane tubing (flexible, tough, fuel resistant and quite transparent) and a small restrictor hole to keep them from sloshing. I experimented with various materials for the little float balls including cork, hollow colored glass balls, hollow brass balls, epoxy and micro-balloon balls and what I ended up using which are balls I machined myself out of the black float material on most automotive senders. I am guessing it is some type of foamed phenolic. It's also used in carburetor floats. Anyway, I took an old float and cut some of it into a piece I could mount in the lathe and machined it into a ball shape. It could also be carved and sanded to a rough ball shape. It's the best stuff I could find and has worked great for several years. (I have some samples that have been floating in hundred octane for 11 years.) Being black, it is very visible in the tube. I also put a white background behind the tube. +++ #4277 From: "Donald Schindler" Subject: Re: [Bearhawk] I have been useing the rod type capacitance sender in my Thorp for many years now. I has never given me a lick of trouble. It can be cut to length to fit and also can be bent to some interesting angles if needed. Calibration is a cinch; fill the tank then turn the little screw till the gauge reads full. Drain the tank to your reserve and turn the other little screw till it reads empty. I would blister it inward, it also has the advantage of recessing the electrical connections a bit. They advertise this sender in Sport Aviation but the name escapes me right now. +++ #4285 From: "Rob Gaddy" Subject: Aux Tank Hook-Up? While sitting here drilling the zillion holes in the spar cap strips, my mind has wandered ahead. I would be interested in some comments about the proper hook-up of the auxiliary tanks. My plans are to not install the aux tanks right away, but to make provision for them if wanted/needed after first flight. I was thinking of "draining" by gravity the aux tanks into the mains after the mains are down to 1/2 or so. I know the level difference is not that great, so a large line (3/4 inch or so) would be needed to get ahead of engine burn rate. I was thinking of a large diameter line between the aux and the main, with a valve operated by rod or flexable control cable between the tanks. Just burn down the mains, them pull the aux tank intercommect valves. Just don't forgett to close before refueling. I was thinking that a in this way electricity would not be needed, the need to manage fuel would be minimized (I don't want to run a tank "dry" as indicated by engine running lean, rough, or stopping!!), and no additional fuel level indicators would be needed. I plan to use a simple sight glass gage for each main. +++ #4286 From: Del Rawlins Subject: Re: [Bearhawk] Aux Tank Hook-Up? > I was thinking of "draining" by gravity the aux tanks into the > mains after the mains are down to 1/2 or so. I know the level > difference is not that great, so a large line (3/4 inch or so) > would be needed to get ahead of engine burn rate. IIRC, this is the system recommended in Bear-Tracks except for the valves. I'm not sure what the advantage is to the valves except that you would be able to leave the aux. tanks empty if you didn't anticipate needing them. The only time I can think of that this would be useful would be to reduce weight for performance reasons, in which case I think I would just put less fuel in using a calibrated stick and avoid the additional complexity (and weight) of the valves. Personally I'm leaning towards installing them the way Bob has them in proto 2, not connected to the main fuel system in any way. That way, I could use them for transporting mogas or 2 stroke premix for outboards, atv's, etc. to my remote camp without resorting to something stupid like carrying fuel jugs in the cabin. +++ #4287 From: Fred, partner with Shelly fmuder@a... Subject: Re: [Bearhawk] I believe the name of the company that sells the capacitance based fuel monitoring system is SkySports in Linden MI. www.airstuff.com or 1-800-AIR-STUFF. Very nice, helpful people. Shelly and I have dealt with them for a number of years and have used their fuel monitoring system on 2 projects. +++ #4291 From: Russ Erb Subject: [Bearhawk] Aux Tank Hook-Up? I think you would be surprised by your results. Since the main and aux tanks are basically at the same level, when you open the valve about 1/2 of the aux tank would flow into the main tank, until they both reached the same level(!). At this point, you still have fuel in both tanks, and will until they are mostly empty. At that point, what's the point of the valve? The aux tank would not just fully drain into the main tank as you seem to imply. Note if the aux tanks were indeed empty and you opened the valve, the fuel would flow from the main tank to the aux tank! In reality, you have one tank per side that consists of two containers. In fact, if you leave the fuel selector in "BOTH" you really only have one tank in the whole airplane, with fuel flowing from the uphill wing to the downhill wing on sloping ground or leveling between sides in flight. +++ #4372 From: "Steven Estergreen" Subject: Re: 3 psi Fuel Tank Test Water is 62.4 lb per cubic foot. 6 inches of water will exert a pressure of 31.2 lb per square foot (unaccelerated) or 0.22 psi. Fuel is roughly 3/4 as heavy as water, or 0.16 psi per 6 inches (typical height of a wing tank?). A 6g acceleration with this 6 inch tank will produce approximately 1 psi. However, the nose tank in our Christavia Mk1 has a sump between the pilot's legs. The total tank depth (I'm not looking at the print and we haven't built it yet) must be closer to 18 inches than to 6. Assuming normal category 3.8g, this would produce a pressure of 1.8 psi. Testing to 3.5 psi would give an additional factor of safety of almost 2, assuming the test didn't damage the tank. I'd be comfortable with that. We've been discussing this whole fuel tank situation lately (this is a group project) and have been wishing we'd designed in wing tanks (in place of the nose tank), for safety rather than capacity. Another option we may discuss seriously is purchasing a fuel cell for the nose. I know that won't be a cheap solution... but 18 gallons of fuel is an awful lot to have in one's lap. Not that quantity makes much difference once you get beyond a gallon or so. Scares the pee out of me when I light a brush fire in my yard using just a cup or two of gasoline. It's hard to throw a match from far enough away to feel safe, and if I don't get the match on it within a couple seconds, I walk away and come back to it after it has a chance to evaporate or soak in, because the vapors spread so fast. +++ #4374 From: Ken Beanlands Subject: Re: [Bearhawk] Re: 3 psi Fuel Tank Test I, and some other MK 1 builders have had relatively good success of extending the range by extending that sump down by a few inches. Also, if you want to build a double walled, fiberglass/foam tank that's twice as resistant to leaks, drop me a line and I'll describe the process. The tank is relatively light and inexpensive. It took no more time to build than an aluminum tank and is almost impossible to build with a leak. Mine survived a 3 psi test with flying colours. However, I did the test a little different than others have suggested. I filled the tank first and then pressurized the tank through the vent fitting. This has a two fold advantage. First, if the tank does leak, you can follow the stream of watter to the source of the leak. Secondly, and more importantly, if the tank ruptures, it will not go POP! It will just leak out. Watter is considered incompressible making it less likely to esplode (fill a balloon with water and another with air and push a pin in both) I'd like to say that this was all my idea, but aircraft manufacturers have been using it for years. These guys test the fuselages of pressurized aircraft to failure. Believe me, you would not want to be anywhere near that balloon when it popped ;-). To solve this, they immerse the fuselage in a giant pool and then pressurize the water inside. The water inside the fuselage is generally dyed so that it is easy to determine where the leaks are and where the rupture occurs. +++ #4386 From: Russ Erb Subject: Re: [Bearhawk] Re: 3 psi Fuel Tank Test > I filled the tank first and then pressurized the tank through > the vent fitting. So Ken, how do you get ALL of the water out of the tank? I've seen other sources specifically say don't ever put water in a fuel tank, presumably because it is difficult to get it all out, except of course when the tank is feeding a running engine in flight... +++ #4387 From: Tim Subject: Re: [Bearhawk] Re: 3 psi Fuel Tank Test How about Gas line anti freeze it absorbs water, handy item up here in the North........ +++ #4394 From: Joel Mayhall Subject: Re: [Bearhawk] Re: 3 psi Fuel Tank Test I thought the drain petcock was there to remove water from the tank. Actually, you can pour alcohol into the tank since it is miscible with water. Also use an air hose or a shop vac to ventilate and remove any residual liquids and vapors. +++ #4402 From: "Kent White" Subject: Re: [Bearhawk] Re: 3 psi Fuel Tank Test I am reluctant to pressure test the tanks I build with water for two reasons. One, as Bud intimates is the whole dryout time and effort being just one more delay in a long building process. And two, water will not test as well as gasoline because of the viscosity differences. This occasionally has caused me much consternation when, after "reliably" testing and installing and filling the tank---it then seeps. I have traditionally pressure tested my stainless tanks to 8psi air (once to around 30, see below), terneplate steel to 10psi air, and aluminum to 6 with air. To avoid seeps, I have simply pressure tested first with air and sprayed the outer surface with dish-soapy water, and then filled the tank with fuel and let it set in the warm sunshine to expand all of the metal joints and seams nicely. After 8 hrs it is then emptied, rinsed with rubbing alcohol (cheap and available) and finally dried outside the shop. I once tried a local high-end radiator shop for testing my latest complex, brandnew, expensive, handmade work of art because they could pressure test under water (hydrotest?). A safe process and reliable---WHEN the danged regulator accurately measures the air pressure inside the valuable tank! For those unwilling to fill with fuel, how about a like-viscosity fluid like the rubbing alcohol? Gallons are cheap, and the leftover makes a wonderful solvent for cleanup on paint and composite projects. +++ #4406 From: "Lee H. Erb" Subject: [Bearhawk] 3 psi Fuel Tank Test > Here is the applicable section from 14 CFR Part 23: > Sec. 23.965 Fuel tank tests. > > So, Lee, are you recommending that we test our tanks to 3.5 > psi? Apologies for the delay in answering. My following opinion is based on what I was taught: Structural Test The 3.5 psi test for the FAA is a Structural Test. This test is to prove a Design. I feel confident that the Bearhawk design is OK and does not need a Structural Test. (This does assume the welding is satisfactory qualiity.) If I were doing a Structual Test I would fill with water and apply air pressure with a hand pump using a mercury manometer for a pressure gage. Using air alone in inside anything for a Structural Test is dangerous. Residual water can be eliminated by (1) setting the tank in the sun and then (2) blowing (very slowly) dry shop air through it. (3) A can of auto gasoline additive that absorbs water (usually pure alcohol) can be poured in, sloshed, dumped, and repeat (1) and (2). DO NOT use Rubbing Alcohol! It contains 70 percent water. I ruined two auto gas (steel) tanks with it. Leak Test From the early e-mail I understood the testing at 3 psi to be a leak check. For a leak check I believe that you do not have to go that high a pessure when using air pressure inside and soapy water on the outside. Using a water manometer about 12 inches high should be sufficient. The final leak test is still filling the tank with gasoline. (Any welding thereafter must be accomplished with the tank full of water.) I do not consider the use of water inside a tank satisfactory for a leak test. Gasoline will go through holes that water will not. Years ago I was told that certain aircraft tip tanks made from Fiberglas passed a water leak test but when gasoline was put in, the gasoline seeped out. +++ #4413 From: Joel Mayhall Subject: Re: [Bearhawk] Re: 3 psi Fuel Tank Test Thats why I usually rinse the interior with alcohol to absorb all the remaining water. I have steam cleaned several gas tanks. After draining them I rinse with what ever alcohol is available i.e. methanol (wood alcohol), ethanol (denatured drinking kind), or propanol (rubbing). Paint stores or Home depot should have it. Actually, since alcohol has a much lower surface tension (it will penetrate small holes) than water it might make a good leak detector especially if a dye is added. After the alcohol is emptied, I vent the interior with air until all liquid is gone. +++ #4450 From: "Mike Eldredge" Subject: hypothetical fuel cap vent ice problem With the fuel cap vents designed the way they are, facing into the airstream, I presume the plane would be susceptible to engine failure due to fuel starvation should the vents become obstructed in flight. Has anyone given any thought to this problem? Aside from the obvious precaution of avoiding flight in icing conditions, what remedy or precaution would be advisable to protect against fuel starvation due to vent obstruction? I would hate to be without power in a situation like that. Any ideas? +++ #4451 From: Ken Beanlands Subject: Re: [Bearhawk] hypothetical fuel cap vent ice problem Cross vent the tanks. If I remember correctly, the Cessna 180 has a vent in each tank and then the tanks are vented to each other. There is a hose that runs between fittings on the inboard of each bladder. Inside the bladder, a hose runs from the same fitting to the outboard end of the bladder. There are check valves to prevent fuel from flowing in the lines, but I don't remember if they are on the ends of the outside vents or the cross vents or both. I can just remember lying on top of the wing with my arm stuck in the tank all the way up to my shoulder trying to replace a stuck vent valve. In April, that fuel was REALLY COLD (of course we didnt drain it first, that would have been the smart and safe way to do it ;-) !! I can get a copy of the 180 fuel system faxed to me from Dad and send it along if you'd like, but it may take a little time as he is visiting my sister in Halifax. Anyone else have a copy handy? +++ #4603 From: Russ Erb Subject: Fuel Tank welding notes My friend with the TIG welder finished welding my fuel tanks yesterday. Even more amazing when you consider he had just come back from Florida house hunting and greets the movers at his door on Monday. Just gotta love these EAA folks. This session was to fix some of the things we had done that didn't work out very well before. One was the installation of a better scupper drain design. Kent would like it because it involved beating a depression into a sheet of aluminum with the back end of a ball-peen hammer (oooooooooooh--actual metal forming!). The biggest issue, though, was re-doing the fuel filler cap. Aluminum heats up so fast in one area and dissipates the heat so fast into the air that one part gets hot and expands while other parts are still cool. Then the weld cools and locks this distortion in. Also, if you don't get the aluminum really, really clean, the welding takes longer, which means more heat, which means more distortion, which means more aggravation, which sends you running around like Planter Bob yelling "AAAAAAUUUUGH!" or something even less polite. When we did the tanks the first round, on the second filler cap flange (yes, that's right, the first one went fine) we ran into problems with the end result that the flange was so distorted that it was unusable. I eventually cut off the fuel filler flange and ground away all (most) of the weld bead. See previous post on the hazards of fiberglass cutting wheels. Bought a new flange, which means I have a spare fuel cap now. This time, we tried it a little different (actually his idea). Instead of welding the flange directly to the tank, which would distort in uncontrollable ways, we welded the flange and its spacer (a circle of 1/4" tubing to hold it up above the tank) to a flat sheet of aluminum (fuel tank material). This gave us more options to control the distortion with bricks, cutting tacks and re-welding, bending, etc. Part of the problem is that the flange is so massive compared to the sheet, so it takes a lot more heat than required to just weld the sheet. After finishing the flange welding, I cut the sheet to a size that would fit in the space available on the tank. After about a half hour of carefully bending this sheet to match the pre-existing distortion in the tank, I blind riveted it into place and my friend welded the sheet in place. Seemed to work out real well, especially since he said the lap welds of sheet-to-sheet were much easier than doing the flange. Just another technique to get the job done, and very convenient for doing "repairs" for you to keep in the back of your mind. By the way (BTW), the Pro-Seal on the outside of the tank to seal those pin-hole leaks seems to be working very well. More as I finish up the sealing. +++ #4607 From: Russ Erb Subject: Re: [Bearhawk] Fuel Tank welding notes > You didn't mention whether or not the hole for the gas tank > flange was cut before or after welding. The hole was cut prior to welding, and I don't think it would make any difference at all. That distortion is driven by a powerful force! +++ #4610 From: Russ Erb Subject: More notes on leak testing... Yep, Erbman's been at it again. Here's the latest thoughts... This time I changed from a vaccuum gauge to a water manometer for pressure measurement. What a change! Highly recommended. To review, the density of water is 1.938 slugs/ft^3, and 1 psi equals about 27.6 inches of water. So for one psi change (plenty to initially check leaks), instead of a pointer moving about 10 to 15 degrees (which would change by 1/2 psi each time you tapped it), I had water moving just over 13 inches each way. Manometers are neat because they don't require calibration and show very small changes in pressure. Now, let's review some concepts that after you think about them lead you to say "Well, DUH!" but may escape you if someone doesn't force you to think about them. First, the better sealed the tank is, the tougher it is going to be to control the pressure in the tank. Huh? Let's try that again. I'm feeding air into the tanks from an air compressor, dropped through two regulators. The first regulator drops the pressure to about 10 psi, and the second regulator drops the pressure the rest of the way. This setup makes the regulator much less sensitive than if it was trying to drop 100+ psi to about 1 psi. How do you cause a pressure rise in a tank if it has leaks? Easy--all you need is to be able to provide air to the tank faster than it will leak out. The higher the pressure in the tank, the faster the air will leak out. Assume the air is coming in at some flow rate at 10 psi. The pressure in the tank will rise until it can push the air out the leaks as fast as it is coming in. As long as the tank is leaking, the pressure in the tank will be less than the source. When the tank is sealed, the pressure in the tank will be equal to the source. Thus keeping 1 psi in the tank may take 20 or 30 psi input if it is very leaky. When it is sealed it will take 1 psi input. Thus, as the tank is sealed up, a smaller pressure has to be input, which requires less turns on the regulator. Thus, it gets harder to adjust it. Second, there is a huge lag in this system, which becomes apparent when using the water manometer because it shows such small changes in pressure. Since the tank has a volume of 25 gallons, it takes a while to pump in enough air to raise its pressure. Thus, I found it best to just crack the regulator and wait about a minute or more for the pressure to stabilize. Sure, you could apply some "lead compensation" by opening the regulator up more and then turning it back when it approached the desired pressure, but that runs the risk of grossly overshooting the desired pressure, with possibly disasterous results. As always, more thoughts to come as they occur to me... +++ #4611 From: bearhwk272@a... Subject: Tank testing and glue Couple quickies. Leak testing tanks, I am thinking that a possible way to do this is to put a balloon or glove on the tank as a safety valve. Pressurize the tank with freon and use a sniffer to check for leaks. The new electronic type, not the old flame thrower, are sensitive to the near molocule level. I bet it is easy to find a tester in the desert, not so easy in Alaska. +++ #4621 From: Russ Erb Subject: [Bearhawk] Tank testing and glue > Leak testing tanks, I am thinking that a possible way to do > this is to put a balloon or glove on the tank as a safety > valve. Pressurize the tank with freon and use a sniffer to > check for leaks. The new electronic type, not the old flame > thrower, are sensitive to the near molocule level. I bet it > is easy to find a tester in the desert, not so easy in Alaska. Kevin,this doesn't sound like a good idea to me. First of all, the EPA and the militant tree-huggers will be all over your case and probably chop up your completed airplane parts for even THINKING of intentionally releasing freon into the air (this is assuming you were able to get some to begin with). Second, having just done mine, I suspect that the sniffer would tell you that there is a leak in a general area, but won't show you exactly where. Also, consider a case where you have three consecutive rivets with small leaks in the welds. The sniffer would probably identify "a" leak in that area, but not show you exactly where. Using air pressure and soapy water will show each leak individually. Just look where the pretty bubbles are forming from. Then there's the fact that your idea would probably cost more to do. Nope, can't recommend it. I do like the part about the balloon as a pressure measurement/emergency release "valve" (one time use). That has potential. +++ #4629 From: "Bill Cox" Subject: Re: [Bearhawk] Tank testing and glue I used the balloon inflated to about 10" diameter and soap solution over all seams and rivets to leak check. Very effective and I believe safe from overpressure. +++ #4635 From: "Kent White" Subject: Re: [Bearhawk] Fuel Tank welding notes Tank necks: You should flange the tank surface up to receive the neck prior to welding. And open the hole first. You may do this by press-flaring, bobsticking, or hand working. Another help to defeat distortion is to either raise or depress the deck around the neck area by 1/ 8" min. using a press or form blocks. Or adding a 1/4"w X 1/8"h bead in a circle around the neck, about 1" out, helps as well. I have tried much foolishness and heresay over the past decades and dozens of tanks built, but indeed you are free to reinvent or speculate as much as you wish. Two nice efforts were aluminum tanks that left no distortion at all, and one was polished. Strictly for skilled persons, those. If you do have practical tested techniques, and wish to share them with the grunting sweaty craftsmen out there, send them on to me, as after two years of prep I am now ready to begin filming "Tanks Alot". +++ #4641 From: Leonard mail-to-mo@j... Subject: Digest No. 282 Subject: More notes on leak testing... "Erbman's" dissertation on the pressure needed to hold 1 psi sure sounds familiar - does engine compression testing ring a bell? Truly, it's not the pressure on the inlet, but a combination of pressure and it's relation to the inlet size which determines the flow into the tank. If the tank is leaky, and you're trying to maintain 1 psi, you might need 30 psi behind a 1/8 inch id hose to the tank to maintain it, but less than 2 psi would probably be more than enough through a 2 inch pipe. +++ #4652 From: "Kelvin" Subject: Re: [Bearhawk] Tank testing and glue I agree with Russ, not only will the EPA types will be all over you but it is illegal to knowingly vent Freon. I forget the maximum possible fines and penaltys, but why mess with it? In my profession, upon occasion, I have a need for leak detection. If you have access to various electronic leak detection equipment, they make a ultrasonic leak detector that has pinpoint accuracy. I only use the electronic stuff when soap and water is not practical, (too cold, too much area to cover, etc.) I sure wouldn't buy it for a gas tank. In my hobbies, I've used a balloon over the gas tank filler neck for a indication of leak. Over the short term it makes a great leak indicator. Over the long term it makes a good indicator of barometric and temperature changes. I've never welded up a tank before so I have no idea of my abilities to weld up a leak. I love the idea of being able to use glue to plug leaks. I do have concerns over the long term stability of using anything but a weld. If you want a painful experience, cut a huge patch of wing fabric so you can get a leaking gas tank out. It hurts! +++ #4658 From: Joel Mayhall Subject: Re: [Bearhawk] Tank testing and glue Freon R-12 refrigeration gas is no longer manufactured (but still available) and was replaced by 134a gas. This new gas is similar to R-12 but supposedly doesn't harm the environment. The electronic detectors will detect a gas leak as low as 0.5 oz per year. I paid $175 for mine. The detector will generally get you within an inch or two of the leak unless the area is flooded with gas. Usually to pinpoint the leak, soap bubbles are used and work ok unless it is a big leak that blows through without making bubbles. (Reducing the pressure will help) There are also dyes which can be seen either visually or with ultra violet light. On the cheaper side, your hand or better yet, your tongue can feel very slight leaks. (best done without bystanders to maintain your reputation) +++ #4668 From: Corky Scott charles.k.scott@d... Subject: Re: [Bearhawk] Digest Number 284 > If you want a painful experience, cut a huge patch of wing > fabric so you can get a leaking gas tank out. It hurts! This is specifically why I've deviated from the Christavia plans regarding the installation of the wing tanks. I felt sure the the best way to guarrantee a leak in the fuel tank was to make it extremely difficult to remove. ;-) So I modified the fuel bay of both wings to accept a fuel tank welded together with a flange around the top of the tank. The tank itself forms the top of the wing with the flange screwed to the spars and ribs that surround it. The fuel bay is stiffened by stiff aluminum sheet underneath the tank so I could do away with the diagonal tube called for in the plans. The tank is not subjected to any twisting or fore/aft movement. If I need to remove it I'll have to drain it, remove the fuel line and sending unit wiring, remove all the screws and yank up. My public thanks to Bruce Frank for accepting the job of welding up these tanks. I spect he wouldn't mind doing a few more for Bearhawks, should it be a similar fit. +++ #4733 From: Doug Knight metalfab@p... Subject: Vented Fuel Caps home page. I'm still alive and choked at the volume that I missed here on the board. Any way I have been teaching myself HTML and put the caps up on thier own page. Other Bearhawk stuff too. Just go back out to the real home page once you are thier. Don't laugh, this is my first effort. http://www.geocities.com/doug_knight_94501/Fuelcaps/Pic1.html +++ #4740 From: Steve Eldredge Subject: RE: [Bearhawk] Vented Fuel Caps home page. Nicely done. A question on the flange however... Is the flange supplied prewelded as shown, or is that just a representation of how the ring would attach to the top of the tank? Also is the price for the seals for a pair of caps or just one? +++ #4751 From: Doug Knight metalfab@p... Subject: Re: Vented Fuel Caps home page. If I supplied them prewelded you could rivet and proseal them to the tank;-). On a serious note, this was the test weld ring to make sure that all the measurements and corrections worked out. I did not have any 5000 series .050 Al, so my test was done with 6061 and an old shop worn piece at that. The original test square was larger than a foot square. The test weld was tacked in six locations and then with a balanced skip welding precess. As it is, this over welded. The smaller piece represents what I had to trim to be able to sent to Bob B. I haven't done that yet and will do it by the end of this next week. On the back side I showed that the tank builder could be a little sloppy just as long the flange was seated hard to the skin. The flange does two things, first it takes the weld away from the inner race, and second it is much easier to stack a small fillet weld against the flange to the skin without distorting the entire flange. Mind you, there is a built in out of round tolerance +/-.025" to the inner race. Sloppy welding is a no-no. Maybe I should put all this on the wed page. O-ring sets are per cap. The Viton doesn't breakdown like other rubbers and has an indeffenent shelf life. I only think one would need to have one spare set, but that's my opinion. With all the fuel tanks that I have done in the past, it might be wise for all that I show how to do a proper and uncomplacated job of building a fuel tank. Would you all like to see this on a Web Page? http://www.geocities.com/doug_knight_94501/Fuelcaps/Pic1.html +++ #4805 From: Doug Knight Subject: Building Status #433 To date I have ALL ribs formed and flanged except the ailerons which I am Bob sticking at the moment. Attach and stiffener angles done. All the Wing Iron is done and I started on some of the spar splice and end plates. Next load will Aluminum will be for the fuel tanks and the spars. Kent White asked to see how I would do a fuel tank, so I will oblige him and also share what I know with all my fellow Bearhawkers. For me, work shut down in early NOV. and I completed my Wing Iron then in the huge now empty shop at work. My bits and pieces where spread out over one end of a large table. But now work, now cash flow and ran the project out materials. Turn around on the horizon. I'm serious need of seat time and the moment. On my home field (CCR) we now have an 8 ft break, lucky me. My EAA Chapter #393 guys here have really been great. I seem to be the only Bearhawk here at the moment, and will expect that will change as I get further along. I have done some unique fixtures and other tooling and will be able to put them up on a the web page soon. Some of the stuff is pretty standard and some is generated by the type of work I do. You'll have to wait and see when I have it up. On another note I completed the run of 10 vented fuel caps and have been seriously dragging my feet. Didn't weld the test ring till a few weeks ago. Basically these caps are at cost and I make nothing off them. The machinist that I work with is in his early seventies and cut his teeth in England during the war as an Aircraft Breaker. I guess only the old farts will know what that is. So if you get a pair of caps you are feeding him. And he wants to do more. And in all this he happily machines parts for me as I need them. So in this partual lull I have been doing some fishing, which is the whole reason to be Bearhawking in the first place. Welder for hire. And no I don't gas weld either. +++ #5260 From: Pat Fagan pfflyerz@c... Subject: plumbing I had been really excited about getting to the point of putting things together above and beyond the plans, but now I am not so sure. I wish Russ was ahead of me so that I could just copy what he does. I love the look and feel of the Andair fuel valve but it took a lot of thinking to figure out how to make it work. I'm liable to go bald from all this head-scratching. I've been contemplating the fuel line attachments between wing and fuselage and studying the photos on the CD. The CD has a picture of the forward fuselage fuel line on Proto 2 where it exits the fuselage fabric just ahead of the window hinge. It looks like Bob slides a flexible hose onto this tube to connect with the wing, but the tube isn't beaded. I've been trying to figure out how to connect everything with the AN hose connectors, but would rather leave all that hardware out if a straight tube is sufficient. Would double hose clamps be recommended? I'ld also like to do a cleaner job of the fuel sight tubes. I ordered the AN bulkhead fittings with hose barbs on each end thinking they would do the job, but they are HUGE. I seem to recall, back when I flew SuperCubs, that they have a very nice looking sight gauge setup. I wonder what hardware goes into their makeup? If anyone has access to a SuperCub and a digital camera, I would appreciate a picture of the sight gauge. I think Kevin D. said he can get hold of both a SuperCub and a Husky. Does the Husky use a gauge like the cub? Might be worth calling Aviat to try and buy the setup. +++ #5273 From: "William & Delinda Johnson" Subject: RE: [Bearhawk] plumbing I have spent 40+ hours looking at the fuel lines and Andair valve. I purchased the larger (3/8 I think) and I did not like the floor position. So, my valve is under the pilot seat on the vertical truss. Andair gascolator right behind the vertical truss so I can drain fuel as I get into the bird. I will post a picture at some point. I am planning to buy a simple capacitance fuel system with gages. Some may find this comment strange, but I think that is simplier in the long run . . . +++ #5283 From: Kevin bearhwk272@a... Subject: Sight gages The Husky fuel sight gauges are mostly un useable and KAKA. They are just made from a piece of Tygon tube that in a year or so became stained and brittle, very hard to see the fuel level. The Supercub has a better system using an aluminum cage around a glass or plastic sight tube. Go to McMaster Carr catalog and look sightglass for some ideas. The type for industrial hydraulic reservior is a good sample. I plan to use this concept which is also similar to the Supercub. Do not know yet if I will buy, make or modify this device. I am sure that it is simpler than a spar fitting. I plan on mounting the sightglass on the root wing rib with a window at the fuselage root to look out at the sightgauge, keeping fuel out of the cabin. little details like a float, tube compatable with fuel, light background, colored level bands need to be figured out. ( Rummor has it that the reason most fuel sightgauges are in the cabin is cause it is too dark in the root to see.) +++ #5285 From: "Bruce A. Frank" Subject: Re: [Bearhawk] Sight gages I haven't bought yet, but the sight gauges from McMaster fit the bill. My intentions is to back-light the gauge with an LED. The Tygon tubing is not actually rated for continuous contact with gasoline. Some vinyl tube is, but it still discolors over time. The protected glass tube gauges seem to me to provide the best setup. They are not inexpensive, that is the ones with shut-off valves top and bottom, but they will never malfunction like the tank senders seem to always do in aircraft. Someone suggested, possibly in this group, that a piece of the expanded foam float used in carburetors can be used to float in the tube to really aid in fuel level ident. +++ #5286 From: "Mark and Tina Lapierre" Subject: Re: [Bearhawk] Sight gages > My intention is to back-light the gauge with an LED. You may want to think about running some fiber optic cable into the wing root and placing the led behind the panel or somewhere away from fuel, kind of like the way fiber-lites work. Hmmm, I wonder if the tube would glow if the end of cable were attached to it... Multimode fiber (the cheap stuff) will carry more light than single mode fiber. Putting the led directly in the wing root will probably work just fine. The conditions necessary to cause a problem would be a leaky sight guage, fuel vapor forming in the wing root, and a short in the led wiring. The fiber optic cable is just a cool way to avoid bring fuel and electricity together at all. +++ #5288 From: Budd Davisson Subject: Re:tank gages Re: tank gages I don't hear anyone talking about the articulated float type gages in the wing root. Is there a reason for that? I don't personally like sight gages for many of the reasons mentioned, plus, in a crash, they are just another place fuel can easily exit. The tanks in the BH kit are set up for sight gages, as per plan, but they also have a panel to be used in putting an articulated gage in. These can be calibrated in a manner of minutes. I supposed a capacitance gage could also be used in the same panel, but some compensation would have to be made for the lead not coming in from the top of the tank. +++ #5292 From: "Mike Carriere" Subject: Re: [Bearhawk) Fuel Capacity #463 and #468 are looking for some help on fuel capacity. We have decided(almost) to use a couple Allisons C17's for power (317HP) turbines. @26 gal per hour we need more capacity. If anyone has experience in getting more fuel capacity we would appreciate hearing from them. We would need 80 to 100 gallons to make sense (4hours) and since they will be float equipped we would rather not be using tip tanks. The projects are coming along fine we have laser cut our ribs, spars etc. and we have made tooling that can press a rib in one shot. A comment was made earlier about laser cutting leaving bad edge. We use argon as a cutting gas and the edges are very clean and can cut bolt and rivet holes. Any help is truly appreciated Mike Carriere. +++ #5295 From: Rod Smith rsmith@a... Subject: Re: [Bearhawk) Fuel Capacity I think the best place to start would be to talk with Bob Barrows as he has more insight on the design of the plane than anyone else. If additional tankage in the wings is not an option, how about a belly mounted external fuel tank. They are quite common on Super cubs and now Huskys in Alaska. Some of them are split with half for fuel and the other half for cargo, probably not necessary in most cases for the Bearhawk. Just out of curiosity, how much do those turbines cost? +++ #5299 From: Pat Fagan pfflyerz@c... Subject: Re: [Bearhawk] Snoozin... Thanks everyone for the info on the sight gauges. Though I haven't seen the McMaster ones yet, they sound like what I was envisoning. Del, I guess I can do without the picture for the time being, thanks for checking on it. +++ #5308 From: "Collin Campbell" Subject: fuel lines Not there yet, but am thinking ahead as to how the fuel system all hooks up, etc. One question I had is about how to connect the lines from the wing tank to the fuselage fuel lines. I noticed in the Jan. 99 Beartracks, that Bob shows a drawing of the fuel system. Fine. No problem. Bob suggests using "MILL-H-6000-6 hose to connect the two lines together. Now I know this must be an acceptable method, I think the Cessna 170, I used to own was rigged this way. Anyway, someone out there must know the secret to doing it this way. I was playing around with a piece of 6000-6 hose and a piece of 3/8 tubing and I don't see any way that this set up will not leak. They just don't fit tight enough and even with hose clamps don't think it would work. Is there a way (simple way) to form a flare or bulge on the tube so it will fit tighter. Or did Bob mean to say 6000-5 hose which is next size smaller and would provide tighter fit? At this point I am leaning towards just using AN fittings in the whole system. Any thoughts? +++ #5318 From: "Mike Carriere" Subject: Re: [Bearhawk] Re: [Bearhawk) Fuel Capacity Thanks, a belly tank is what I was thinking as well. Since the 317 HP turbines are under powered for their original application in helicopters they tend to be available fairly cheap. We have an offer of two for $8,500 each with decent hot section times and we don't know the other component times yet but they would not be (normally) a concern as there are a lot of parts available. They only weigh 120 lbs and that's great but they suck up that furnace oil at 26 gal per hr. We are close to installing a Allison 450 in our C206 so we get to talk to the kerosene burners a lot. The conversion also would give me a free TSIO520M 310HP for the BH hence the quandary > > Mike Carriere. +++ #5376 From: Pat Fagan pfflyerz@c... Subject: Re: [Bearhawk] fuel lines I was concerned about connecting hose to tubing without a bead also. Some time ago, a builder wrote a tip in Sport Aviation on making a tubing beader. I saved the article for just this purpose but noticed when I went to build it that it would be too big to do 3/8 tubing. I thought on it a while and came up with a tool that rolls the slickest little bead you could ever hope to see. I will send Mike Meador a picture and drawings for inclusion in the newsletter. It is just the ticket for our purposes. +++ #5671 From: Russ and Penny Erb Subject: Fuel Sight Gauge Test In Progress Recently on this list we had a discussion of sight gauges for the fuel tanks. While others suggested other ways, I did some research (open the Spruce Catalog) and hatched a plan. It had already been reported here that Tygon tubing was a bad choice. With time it would harden and discolor in constant contact with fuel. The catalog makes no mention of its use as a fuel line. Poly-Flo tubing was listed as unsatisfactory chemical resistance to fuel. Besides, it is rather opaque--sort of defeating the purpose of a "sight" tube Polyurethane tubing is listed as suitable for fuel lines, but is attached to fittings with hose clamps, which wasn't exactly the look I was going for in the cabin. Nylaflow tubing is listed as suitable for fuel lines, but the largest size listed is 1/4". Too small. Lastly was Nylo-Seal tubing. It is listed as suitable for fuel lines with "acceptable" chemical resistance to fuel. I had some in a smaller size and noted that it is mostly transparent. Not as clear as glass, but good enough. I ordered up a foot of 3/8 Nylo-Seal tubing with two 269-N 06 x 04 Nylo-Seal fittings. I put the fittings on either end of the tube, and closed the ends with a couple of brass pipe caps I picked up at the Home Despot. I gave the whole shebang to a friend, asking him to fill it halfway with 100LL fuel from preflight draining his tanks to check for water. I got it back today, and it is hanging outside the house where it will experience sunlight and the temperature extrema typical of the Mojave Desert. I'll report back on how it's doing in a few years or when I notice any change. I figure I've got at least until it's time to install a sight gauge. If it seems to be working, then I'll work on trying to find a way to straighten the tube. It comes naturally bent as though it were still on the roll. Perhaps forcing it straight and then putting it in the oven or using a heat gun on it. Sort of like "normalizing" 4130 by post heating a weld to relieve built in stresses (Please, let's not start the discussion of whether that really does anything again...) Russ Erb #164, Edwards CA +++ #5756 From: "Bruce A. Frank" Subject: Fwd: Re: PRC(Proseal) It certainly would be nice if Pro Seal were available in those dual syringe dispensers sized to give the correct proportions. As expensive as Pro Seal is I have had no occasions where the whole container was needed at one time. Has anyone researched for a really inexpensive two part sealer material that has Pro Seal's resistance to fuel. I have had a side by side test for a year now with Pro Seal and JB Weld applied to a piece of aluminum and immersed in a jar of 50/50 mixture of avgas and premium mogas. So far I have seen no change in either, but I am not yet convinced that I could use JB as a critical sealing material (a line of rivets in a fuel tank). Any thoughts? Bruce A. Frank +++ #5758 From: "Kent White" Subject: Re: [Bearhawk] Fwd: Re: PRC(Proseal) Proseal (PRC/strawberry snot) VS JB weld I would never use JB weld on a tank. Flexibility decreases over time, and flexibility is an issue. I have used Devcon aluminum putty and paste on many jobs for 30 years, incl. engines. While far superior to JB, I would never use either on tanks. Intakes yes, but not tanks, unless....... I wanted leaks. Kent "Tinman" White +++ #5762 From: Russ and Penny Erb Subject: RE: [Bearhawk] Fwd: Re: PRC(Proseal) Spruce does seal "Pro-Seal Type Tank Sealants" in "cartridge" form (page 297, 2000-2001 catalog), but at ridiculous prices. Buy two 3-1/2 oz cartridges (7 oz) and you pay the same as for a pint of Pro-Seal (16 oz). Russ Erb +++ #5800 From: "Dan Montee" Subject: Fuel tank NPT fittings I'm getting started on the fuel tanks. I had assumed that I'd be able to buy the aluminum weld fittings for the various NPT attachments. So far no luck. Does anyone have a source or do I manufacture the fittings? Thanks, Dan Montee #415 +++ #5802 From: "Bruce A. Frank" Subject: Re: [Bearhawk] Fuel tank NPT fittings Aircraft Spruce carries the weld fittings. A less expensive method is to just weld the regular aluminum fittings in place. I pick up surplus fittings at flymarkets for bargain prices. Power wire brush (stainless wire wheel) or sand the anodizing off the fittings before welding. Another source for the regular fittings is McMaster-Carr or any of the speed shops (like Summit Racing) though the prices from them are similar to those from aviation sources. Bruce A. Frank +++ #5804 From: Russ and Penny Erb Subject: RE: [Bearhawk] Fuel tank NPT fittings "Aluminum Welding Flanges" Aircraft Spruce 2000-2001 catalog page 161 P/N AN867-1 through -8 Russ Erb +++ #5812 From: Shelly Subject: Re: [Bearhawk] Fuel tank NPT fittings I have a friend who welds in a piece of round aluminum rod about 1.5 ", then drills and taps! Shelly +++ #5829 From: pfflyerz@c... Subject: Re: [Bearhawk] Fuel tank NPT fittings I wouldn't bother buying the welding fittings from Spruce. I did originally and ended up sending them back as they are HUGE. The fittings for the tank outlets are so big that they would have to be mounted a significant distance from the edge of the tank. I ended up making my own, which wasn't too difficult, although tapping the pipe thread for the large fitting was a challenge. On the subject of tanks, I had originally bought the tank filler neck from Spruce and had cut the hole in the tank and wing to use it. After further thinking I didn't want that huge neck sticking above my wing, but was unable to adapt my holes to Bob's fuel cap when that drawing came out. I elected to install the SPRL flush fuel cap in the tank and figured I would leave it to later to figure out how to make an access door in the wing, there is not much space to play with. I finally installed a tank the other day to see how much room there was and was delighted to discover that the cap nestles against the wing skin perfectly. I just need to enlarge the existing hole in the wing to allow removal of the cap. If I can figure out some sort of gasket to put between cap flange and wing skin I will have a flush cap without need of a door or scupper. Pretty cool. Pat Fagan #232 Pearblossom, CA +++ #5831 From: Russ and Penny Erb Subject: RE: [Bearhawk] Fuel tank NPT fittings Pat and I had this discussion before. My solution was to use the Spruce flanges, but I cut off the excess flange on one side to move the hole closer to edge. Sorry, no pictures made it to the CD. I'll have to go take some. Easier for me since I didn't have the setup Pat used to make his own. I've also used the SPRL flush caps, but have always planned to build a scupper. Have the drains built in. Unfortunately for me, we (me and the guy who welded it--not Pat) had more distortion in my tanks so the fuel cap does not sit perfectly against the skin, but is slightly (1/8"?) below it. I may just leave it and not worry about it. Saw Pat's airplane on the gear yesterday. Most cool. Took lots of pictures. More to come. Russ Erb +++ #5832 From: "Dan Montee" Subject: Re: [Bearhawk] Fuel tank NPT fittings Thanks Pat and all who commented on the fittings. I think I'll go with either Franks option of welding in standard fittings or make my own as you suggest. I liked Russ's logic and approach (thanks again for the great CD!) but in the end opted for the keep it simple principle and I'll go with Bob's design. Pat, I noticed that the SPRL caps are unvented. How did you address the venting problem? >"I elected to install the SPRL flush fuel cap, Pat Fagan #232 Pearblossom, CA" Dan Montee # 415 +++ #5844 From: pfflyerz@c... Subject: Re: [Bearhawk] Fuel tank NPT fittings > Pat, I noticed that the SPRL caps are unvented. How did you > address the venting problem? I ran a vent tube completely around the inside of the tank, similar to what Russ shows on his CD. Pat Fagan #232 +++ #5850 From: bearhwk272@a... Subject: Fuel Tanks Just a partial follow up note. Have just passed a pleasant major milestone. Fuel tank hanging in the left wing. I am very pleased with the tank results. Here is some of what was done / learned. 1. Prepare all the parts per Bob's Newsletter. Change the baffle as follows. Do not cut the corner off. Drill a series of .188 dia holes covering about 1.5 x1.5 sq, the corners should now look like perf plate. This helps minimize distortion of the skins. Make a small corner cut .188. DO NOT CUT ANY HOLES IN THE TANK FOR FITTINGS UNTIL FINISHED 2. After doing the brake work on the top and bottom skins, curve the top skin with some boards and pvc pipe so that the top skin has a curvature that matches the baffle and end plates when just laying free on the bench. This pre curving removes stress from the assembled tank and stops the top skin from trying to return to flat when hit with the welding heat. 3. Assemble the tank with clecos on the baffels every 1.5 inches. Top and bottom About .625 on the front and rear baffle edges. I drilled all holes initially at .093. Attach the end plates at about 6.00" interval. 4. I did not rivet the tank, nor did I use any clecos along the top front, bottom rear long edge lap joints. 5. Fit all the skins so that the edge of the flat plate skin stops at the tangent point of the edge bend radius. Do not fit the skins long so as to create a condition where the skin overhangs the mating part. Stop the skin at the tangent point. Fit is very important. 6. After everything is set, square and flat, take it apart and drill out the .093 hole in the skins to .175 dia. Leave the holes at the ends and midpoint of a row of holes at .093. This will " Lock " in the parts at final assembly. Do Not Drill Out The Ends or Baffels. Drill only the skins. 7. Deburr everything. Wash with soap and water. Etch the tank clean. Wipe dry. 8. Cleco back together. 9. Almost there.... Now for the fixture. Using 2" x 2" square tubing, make a rectangular strongback that is 1.0" smaller front to back than the bottom of the tank and 4.0" wider than the tank. Place the tank on the strongback, clamp the tank to the strongback using 2" x 2" tubing running lengthwise, at the front and back of the tank use threaded rod to lightly hold the clamp bars to the strongback. If you did it correct the tank will be held to a frame that will hold the tank during welding and yet allow the tank to be moved and rotated during welding. The top and bottom long edge weld will be held down by 2 x 2 clamping bar and yet allow access to weld. Make sure the fixture is flat and not warped. 10. Weld the tank. I used TIG. The big issue here is work quickly, slowly. Do not allow heat to build up and radiate all over the tank. Weld sequence went like this. Rossette weld the baffels front and rear first, do a front, do a rear alternate from baffle to baffle hole to hole, do not build up heat. Take a break. Weld the four corner welds, all linear welds were only about 3" long. On the end welds and the long edge welds maximum weld length was still about 3". Skip around the tank, take lots of breaks, do not let the tank get hot. Keep the heat at the welding area. Rossette weld in the baffels. Skip around. Tank was Argon purged prior to welding. Now install all the fittings. Leak test. 8 pin holes in the rossette welds. No leaks in long seams. Hope this is clear enough to help. Kevin Deutscher +++ #5880 From: rsmith@a... Subject: Re: Fuel Tanks Thanks for that very detailed description of how you welded your tanks. Where did you get the idea not to rivit, it seems to have worked out well for you. Using the steel frame makes a lot of sense. I was very surprised to learn that Bob who is allergic to electricity, had his tanks on Proto II tig welded for him (steady Planter Bob!). His reasoning was they can be done that way with less distortion. +++ #5890 From: bearhwk272@a... Subject: Re: Fuel Tanks The rosette welds are comonly used in tank work. I have seen mention of it in one of Tony's books. Bob said that the rivets were non structural and that welds could be used in place of rivets. I think that a rosette weld would be tough to do well with gas. The rosettes ended up about .250 to .312 dia and a height of .050 above the surface. If I cannot get digital photos soon I will do analog and see if Russ can scan and post. +++ #5893 From: Jim Ash Subject: Re: [Bearhawk] Re: Fuel Tanks I've done rosettes with gas on 4130 tubing, to fasten an in-line splice of different-sized tubes together. It takes a little practice, but I didn't think it was really all that difficult. Jim Ash +++ #5897 From: bearhwk272@a... Subject: Re: [Bearhawk] Re: Fuel Tanks You are correct, a rosette weld is pretty straight forward, on the tank the two overlaping skins have a hole thru the underneath member where the cleco perviously resided. So the act is like doing circular edge weld while trying to close up a burn thru. Just an aside, always make sure that the outer member has a hole thru to the inner member, some have tried to do a rosette weld by just penetrating thru the outer member. Stick came loose in flight, oops. Kevin +++ #5898 From: "Kent White" Subject: RE: [Bearhawk] Re: Fuel Tanks Welding tank rivets... I believe Tony B recommends using 1/8 rivets for the tanks and then welding the heads. I never relished welding rivets that small, though and so I recommend 3/16. I can weld the small ones, but prefer to suggest to others something doable and of better strength. This method replaces the rosette method, and gives about the same "knobby weld" size that a TIG rosette will. Ahhhh....yes....I gas weld mine. Also, brazing the rivet heads is another traditional aircraft method. Kent "Tin Man" White +++ #5899 From: Russ and Penny Erb Subject: RE: [Bearhawk] Re: Fuel Tanks So is this a case where brazing is acceptable? Had I known that I might have tried that instead. Russ "My tanks have more distortion than yours do" Erb #164, Edwards CA +++ #5934 From: "Tim Anderson" Subject: RE: [Bearhawk] Re: Fuel Tanks Kent - Could you recommend a good alum brazing rod? I might even attempt this procedure. This approuch could save my tig welder the costly chore of tig-ging all those darn rivets. More money left in the building supply account...a good thing. I am avoiding the $800 estimate for tig welding my four tanks until I can avoid no longer. For those that have welded their tanks, where does the distortion appear? ie, does the entire tank warp or is it just around rivet heads and seams? is it simply a cosmetic thing or does it pose problems in straping down inside the wing? Tim #398 +++ #5935 From: "Kent White" Subject: RE: [Bearhawk] Re: Fuel Tanks Re: Brazing the rivet heads. I have researched the aluminum brazing industry, even going back to WW2 when it was first developed. The original material is still around, but over priced. We supply what Ford Motor Co. uses in their experimental shops for assembling engines. It is a beautiful product. Very high quality. And reasonably priced (yeehaw). The flux and the rod are sold together, and must be used together. Clean rod with scotch brite. Mix flux with clean bottled spring water (Evian). Clean parts first with alcohol, then with SS brush. Flux both part and rod. Heat with soft flame till flux runs wet, then touch rod to part. When temp is right, rod will run like water and vanish into seam/joint. When done well, no great evidence of filler seen, unless closely inspected. Do not overheat, as temp for braze is only 40F less than melting of aluminum. If overheated, the rod stops flowing as the flux is burnt and the aluminum surface is thus oxidized. If this happens, Stop. Clean and scrub back to bright, and begin again. Most distortion comes from surface shrinkage (net change in surface area) as metal contracts to solid from the molten state. Distortion: Limit warp by beading along rivet line on each side. This traps the baffle too, if beads go down. Bead either up or down, even a quarter inch bead will help significantly. Same with bungs/fittings. Press up or down around the fitting area, even to make a platform or mesa (bd) inhibiting the warp of the heated joint. BTW, We are still planning the video on tanks. Kent "tin man" White 18 months on one panel, but not full time. +++ #5951 From: pfflyerz@c... Subject: Re: [Bearhawk] Re: Fuel Tanks > For those that have welded their tanks, where does the > distortion appear? ie, does the entire tank warp or is it > just around rivet heads and seams? is it simply a cosmetic > thing or does it pose problems in straping down inside the > wing? All of my distortion came from welding over the rivets holding the baffles in place. The distortion ended up as ripples and dips on that line. To a lesser extent there was some distortion on the large upper surfaces between the baffle rivets that occurred while welding the baffle rivets. If you could assemble the tank without riveting the baffle, or maybe just braze those rivets, you might eliminate the distortion. I didn't pre-arc the top sheet like Kevin recommended, which might also have solved the problem. Regardless, the tank still fit in the bay fine, the distortion was purely a cosmetic problem. Pat Fagan #232 Pearblossom CA +++ #6848 Date: Sun, 15 Jul 2001 14:49:38 -0700 From: Benton Holzwarth bcgh@ Subject: Fuel Valve(s) Was up at Arlington friday to meet a few more builders and look at all the planes. (Great time, but not enough time.) I'd met Gary and Tim last last, but there was a good turnout this year. Lots of faces to go with names now. Saw something that caught my attention on one of the planes -- I think on a Murphy kit at their demo area. The builder had rigged the fuel shut-off using two on/off valves, one at each wing root, rather than the more conventional, single left/on/right/off valve. Seems like the pros and cons would be: Pros: - fewer fittings upstream of the shutoff - relaxed fuel tubing routing requirements - reduced chance of a valve breaking in the 'wrong' place Cons: - more cost (lots more if using Andair valves) - more weight, offset by relaxed routing requirements - operational inconvenience - increased chance of a valve breaking For operational complexity, I'd think most of the time both valves would be left open. If one were alternating tanks left then right, to switch requires reaching to one value then to the other, hence the inconvenience. On the other hand, if one were to make a practice of opening the closed valve before closing the open value, it would seem like it added to safety, by reducing the chance of getting caught with a single valve breaking at the halfway spot, and leaving one in a world of hurt. It also seems like it'd make fuel line routing easier, since you don't have to route to a 'Y' somewhere on the floor or panel -- it could be deep behind the panel, or forward of the firewall. It seemed like kind of a good idea, which made me wonder why I haven't seen it before anywhere else. Deep thoughts? Benton 15jul01 +++ #6849 Date: Sun, 15 Jul 2001 19:03:55 -0700 From: Russ and Penny Erb erbman@ Subject: RE: Fuel Valve(s) > The builder had rigged the fuel shut-off using two on/off > valves, one at each wing root, rather than the more > conventional, single left/on/right/off valve. Historically it has been important to simplify the fuel system. With the system described, it is possible to shut off fuel when switching tanks if not done in the proper order. This is mitigated by operating in "both" normally (the benefit of a high wing). Unfortunately, to do it at the wing would require four (4) valves, because there is a feed from both the front and rear of the tank that don't come together until well inside the fuselage. Remember the fuel must flow to the engine when sitting on the ground or in a climb attitude. If I remember correctly (IIRC) Lindbergh shut off the fuel to his engine in the mid Atlantic by erroneously switching to an empty tank. Of course, he realized his error quickly, but it was brought on by a very complicated fuel system. Benton--did you get pictures of Bearhawkers as directed? Russ Erb +++ #6850 Date: Mon, 16 Jul 2001 02:57:03 EDT From: bearhwk272@ Subject: Re: Fuel Valve(s) I have been pondering the fuel valve situation also, seems as if I know someone who had a C-210, you know factory stuff and all with optional tanks, CD, Intercom, GPS, fuel return to the draw tank, on, and on and on..... except the one time he needed it the most, the handle came off, and no matter how many tanks he had the selector was now in the OFFposition. Being a cool kind of a guy he just dropped into a near by golf course. Hence the "had one". Time warp to the Bearhawk. The Bob system works well but will not be useable for my I0-470. Hence the following decision, comments are welcome. The fuel lines stay per the plans from tanks to the cross floor run in front of the seat. The two lines Tee together at the fuselage CL and go forward to the Gascolator, then to the engine. The return line from the engine, comes thru a check valve, back to a Tee upstream of the gascolator. Two shutoff ball valves are provided one for the right, one for the left. Location, handles comming up thru the floor just right and left of the fuselage CL. On the floor, easy reach with my right hand. Handles locked into the ON position with a latch or Safety Wire ( Not Lockwire ). The shutoff valves are located upstream of the gascolator, downstream of where the front and rear feed lines join. Notice they are called shutoff valves, not selector valves. Both tanks are ON and can be shutoff if required. A problem noted with this system is that if for some reason the fuel pump bypass is returning air with the fuel it may be picked up in the incoming fuel. ( I hate it when that happens.) Kevin Bearhawk # 272 Need a MVP soon. +++ #6851 Date: Mon, 16 Jul 2001 00:07:40 -0700 From: "Bruce A. Frank" bafrank@ Subject: Re: Fuel Valve(s) Each single valve is a more simple valve than the common multi-position valve. The "con" point that there is an increased chance of a valve breaking is answering the wrong question. If the multi-position valve fails it is possible to have access to no fuel tank. the chance of a failure that stops the engine is higher with a multi-position valve than with two separate valves. Sort of like saying that two mags increase the chance of a mag failure. Two mags reduce the chance of engine stoppage. Two valves reduce the chance of no fuel flow to the engine. After looking at the old valve in the salvaged Piper I have, an old sticky, clunky , imprecise indent setup, two valves was a no brainer. I bought two stainless 1/2" ball valves with 90 deg throw rated for solvents, mounting flange cast into the body drilled and tapped for 10-32 screws, Teflon seals requiring no lubrication for life, with a 10,000 cycle life for $8.00 each at a chemical supply house. Two valves is a better redundancy system than the expensive multi-position valve. Since it is easy to reach both wing roots in my plane I see no inconvenience of operation and with "Inline" and "90 deg across the line". With these two simple valves there is a much lower likelihood of miss-positioning the valve and selecting the wrong tank or cutting off the flow all together. Bruce A. Frank +++ #6852 Date: Mon, 16 Jul 2001 00:11:33 -0700 From: "Bruce A. Frank" bafrank@ Subject: RE: Fuel Valve(s) > Unfortunately, to do it at the wing would require four (4) valves, Why is it not OK to "Y" the front and rear feeds together before the valve, thus requiring only one per tank. Bruce A. Frank +++ #6856 Date: Mon, 16 Jul 2001 22:34:05 EDT From: supermexgarza@ Subject: fuel valves I'm going to show my ignorace, but why do you need valves at all? why does one need to switch tanks? i understand about been able to shut the flow of fuel but why switch betwin tanks ? other than one tank can flow a bit more than the other puting the plane out of balance over a cuple of hours, if one runs a equallizing tube from left wing to the rigth one and remain at the same level allways, and both will run out at the same time did i just answer my own question? Javier Garza # 497 +++ #6859 Date: Tue, 17 Jul 2001 01:32:09 EDT From: bearhwk272@ Subject: Fwd: Fuel Valve(s) I have been pondering the fuel valve situation also, seems as if I know someone who had a C-210, you know factory stuff and all with optional tanks, CD, Intercom, GPS, fuel return to the draw tank, on, and on and on..... except the one time he needed it the most, the handle came off, and no matter how many tanks he had the selector was now in the OFFposition. Being a cool kind of a guy he just dropped into a near by golf course. Hence the "had one". Time warp to the Bearhawk. The Bob system works well but will not be useable for my I0-470. Hence the following decision, comments are welcome. The fuel lines stay per the plans from tanks to the cross floor run in front of the seat. The two lines Tee together at the fuselage CL and go forward to the Gascolator, then to the engine. The return line from the engine, comes thru a check valve, back to a Tee upstream of the gascolator. Two shutoff ball valves are provided one for the right, one for the left. Location, handles comming up thru the floor just right and left of the fuselage CL. On the floor, easy reach with my right hand. Handles locked into the ON position with a latch or Safety Wire ( Not Lockwire ). The shutoff valves are located upstream of the gascolator, downstream of where the front and rear feed lines join. Notice they are called shutoff valves, not selector valves. Both tanks are ON and can be shutoff if required. A problem noted with this system is that if for some reason the fuel pump bypass is returning air with the fuel it may be picked up in the incoming fuel. ( I hate it when that happens.) Kevin Bearhawk # 272 Need a MVP soon. +++ #6861 Date: Mon, 16 Jul 2001 23:03:01 -0700 From: Benton Holzwarth bcgh@ Subject: Kevin's FI plumbing (was: Fuel Valve(s)) > Time warp to the Bearhawk. The Bob system works well but will > not be useable for my I0-470. Hence the following decision, > comments are welcome. Kevin's proposed system (view w/ fixed pitch font): +------------+ +------------+ | | | | | tank | | tank | +----+-----+-+ +-+-----+----+ \ | | / \ | | / ----+ +--- | | | | | | +--V-----+----V--+ | | T---<<<---C---+ | | | | G--->>>------ FI dist V - Valves T - Tee G - Gascolator C - CheckValve My first thought here is that by returning the fuel clear back to the tank, you'll get cooler fuel fed to the engine, less chance of vapor lock below the 'T'. Is that more critical with FI engines, or low-wing planes? And yes, I'd not considered needing to gather two lines from each tank together before a valve on each side. Thanks Russ. I still think there is something to consider there. Benton 16jul01 +++ #6871 Date: Wed, 18 Jul 2001 07:25:40 -0700 From: Russ and Penny Erb erbman@ Subject: RE: fuel valves For a high wing, switching tanks is not required. Most high wing airplanes fly on "both" all of the time. Some such airplanes only have an on/off valve. One benefit of the left/both/right valve is in refueling. During refueling, go to left or right to isolate the tanks. If you stay in both, as you fill one tank, it will be crossfeeding into the other tank. Then you fill the other tank, and the first tank isn't full anymore, so you go back and forth for a while. Isolating the tanks eliminates the cross feed during fueling. It also will prevent a fuel imbalance if you are parked on a slope (i.e. bank angle). Russ Erb +++ #6872 Date: Wed, 18 Jul 2001 07:19:41 -0700 From: Russ and Penny Erb erbman@ Subject: RE: Fuel Valve(s) > I have been pondering the fuel valve situation also,... fuel > return to the draw tank, on, and on and on..... except the > one time he needed it the most, the handle came off, and no > matter how many tanks he had the selector was now in the > OFFposition. I haven't seen one, but you might look for a pair of on-off valves ganged together on a single shaft so that it would be a one step process instead of two steps to shut off the fuel. Russ Erb +++ #6873 Date: Wed, 18 Jul 2001 07:21:21 -0700 From: Russ and Penny Erb erbman@ Subject: RE: Fuel Valve(s) > Why is it not OK to "Y" the front and rear feeds together > before the valve, thus requiring only one per tank. The Y needs to be well below the tank. If it was in the wing, at high pitch angles the Y might get above the level of the fuel, thus stopping the feed or forcing a siphon. +++ #6878 Date: Wed, 18 Jul 2001 11:52:12 -0600 (MDT) From: Ken Beanlands kbeanlan@ Subject: RE: fuel valves > One benefit of the left/both/right valve is in refueling. > During refueling, go to left or right to isolate the tanks. Just remember to "un-isolate" the tanks when you're done. This practice led to $55,000 damage to our C-180 when one tank emptied at about 1000' AGL. +++ #6884 Date: Wed, 18 Jul 2001 20:28:03 -0700 From: Russ and Penny Erb erbman@ Subject: RE: fuel valves An excellent point. That's why part of the preflight checklist (you do use a checklist, don't you?) is to set the fuel selector to "BOTH" +++ #7268 Date: Mon, 20 Aug 2001 11:42:06 -0500 From: "Montee, Dan L." dlmontee@ Subject: I wonder if.......... On welding fuel tanks: Fuel tank # 1 is air tight after more returns to the water tank than I care to mention. I used solid rivets on the seams and the baffles. I used 5052 pop rivets on the ends. All my leaking (and warping) problems came from the solid rivets on the baffles and a few on the seams. The 5052 pop rivet welds sealed on the first pass. If I didn't have # 2 tank all riveted up and on the bench I'd try using the 5052 pops on the baffles. The solid rivets have a lot of mass that requires more heat to weld and result in more warping. I tried getting in and getting out as quickly as possible to minimize the warp and that proved to be the wrong strategy. I am going to shave the baffle rivets on tank # 2 and see if that doesn't help. If I'd had Kevin Deutscher's notes before I closed up the tanks I may have used his approach. I would definitely take his advise on not cutting of the corners of the baffles. Dan Montee # 415 >>> 2mar02 #7686-9153 +++ #8224 From: John Dougherty Subject: size of fuel lines Can anyone tell me the proper size fuel line for a 260 Lycoming engine? I'm building tanks and have made the outlet fittings to the size called for in the newsletter, but I have to wonder if I will get enough fuel thru when I put the finger screens in them. Thanks .......Jack Dougherty +++ #8907 From: Tim Subject: Wet Wing Fuel Tank Sealant > ProSeal, I am told it is hard to work with? I called Loctite > to see what they have to seal my fuel tank. I was given > EA9394 to look at. Has any one used this EA9394, please give > your comment. Dam good question and time to reflect.....; If there is one area/issue in homebuilding that stands out 'Crystal Clear' where the learning curve has demanded a lot of re-thinking, replanning, re-purchasing & re-pair.....It's the sealing and continuity of 'wet wings & tanks'......Over the many years now a lot has been 'hard learned'.....The composite crowd had there own learning curve when it came to the sealing of fiberglass tanks whether polyester/vinlyester/epoxy......... Aluminum tanks with poor prep/bonding & the early discovery of deteriorating sloshing compounds were in some cases first flight heart stoppers.....NTSB reports reflect the % of H/B fuel related accidents/fatalites which seem to repeat themselves......This is one arena in which 'These Forums' are worth there weigth.....There is a S-Load of been-there/done that, experience......From this, modifications, product claims/label promises or super ingredient hearsay doesn't mean diddly........Go with what has worked to date.....Don't be a test pilot for a product and please thoroughly research and think out 'Fully' all fuel mods. In memory of Steve Parkman NTSB Identification: LAX99FA052 Tim C +++ #8923 From: "csdurham81503" Subject: Re: Wet Wing Fuel Tank Sealant Don't know who started with the fuel tank sealant question, but I'll weigh in with a hearty A-MEN to Tim's response. Perhaps Pro-Seal is messy and less than fun to work with but it's also proven. I read this week where Van's expects to see its 3,000th airplane flying this year. They all use wet wings, the majority (if not all) of which are sealed with Pro-Seal. My recommendation would be to find an RV builder in your area and learn how to use Pro-Seal. You won't regret the extra effort in the end. Chris Durham #492 +++ #8928 From: "rmb336" Subject: RE: Wet Wing Tank Sealants The Murphy Aircraft use the wet wing as well. Quite a few of the aircraft that get built end up on floats and so far there hasn't been any problems that I know of. I'm currently building a Murphy Elite (a Rebel on steroids) and don't see any reason to change from their recommendations. Richard Bjorn +++ #8940 From: "Forrest Ferdon" Subject: Pro-Seal Just thought I would add my .02 on pro-seal since I have spent a fair amount of time playing with it: - It comes in different consistancies and working times; spend extra to get the right stuff. - Use a foam nap roller or a rubber ink roller to put it on faying surfaces for a thin even film. - Don't pack rivet holes with it. It will prevent full expansion of the rivet and cause future leaking. - It sticks best to etched and alodined surfaces not primered surfaces. - Avoid cleaning holes and drilling out rivets around the stuff. It is a chip magnet. - Double the recommended mix time. Incompletely mixed PRC is a waste of time. - Extremely humid days have weird effects on pro-seal. - Buy a box of latex examination gloves and change regularly to prevent having to wear it in public for the next month. Barrier cremes work well too. - Don't cut it with MEK, water, or stick it in the microwave. These are tricks of the trade that don't always work as intended. - Visualize your assembly process. Allow double the amount of time you think you will need. Once you mix the sealant, you are committed. - Keep gaps in sheetmetal tight. Pro-seal is not a good gap filler. - Don't even think of sloshing your tanks. Fixing leaks in sloshed tanks are a nightmare. Fixing leaks in properly sealed, non-overdone, tanks are easy to find and reseal. - Pick a day when you patients is very high. - Do it right the first time, repeats suck! Forrest Ferdon +++ #9093 From: "collinc2002" Subject: fuel pump I have been thinking ahead somewhat and am beginning to think about what I want in my panel. One of the questions I had is about whether or not to install a fuel pump. If so I would need a pressure guage, right? I know the Bearhawk has a gravity feed system as do most high wings that I am familiar with. But some high wing systems, such as the Maule, has the fuel pump also. The Cessna 170 I once owned had been converted to 180 hp and the stc required a fuel pump. (if fact required not only the engine driven pump, but an electric backup as well) I am wondering as to why, and what are the groups thoughts about whether or not a fuel pump is needed in the Bearhawk. Does anyone know if The Bob used one on either of the prototypes? I don't see any evidence of one from the photos that I have. Collin Campbell #370 +++ #9094 From: Russ and Penny Erb Subject: RE: fuel pump My guess is you'll find the fuel pump(s) installed with fuel injected engines. Carbureted engines require something like 1/2 psi fuel pressure, which is achievable with just gravity feed from a high wing. Fuel injected engines require something like 15 psi fuel pressure, hence a pump is needed along with a backup. Russ Erb +++ #9101 From: Bob Romanko Subject: RE: fuel pump No need for a fuel pump unless your engine (injected or conversion) requires it. Thousands of Cessna 172's can't be wrong. My thinking is if gravity fails one has many more problems than one would find with the airplane. Frankly, I'd rather not have a fuel pump if I could get away with it. One more thing to fail, one more thing to carry around with me. Gravity probably saves about 15 pounds or so. Then again, if it wasn't for gravity we wouldn't need airplanes. For all the things I have thanked the Big Guy upstairs for, gravity has never been on the list. I think I'll add that tonight..... Planter "Gravity is our Friend" Bob >>> 20may03 #11298-18250 +++ #12732 From: Budd Davisson Subject: Re: [Bearhawk] AviPro Wing Test & newsletter > I also notice that you're quoting a fuel capacity of 52 gallons > instead of 55. My calculations on the tank shape came up with > something like 50 gallons--some day I'll find out for sure Actually, I think you're closer than we are. Bob says 55 gallons, but 50-51 is closer. We measured with a gallon jug but there was a little guessing because actual gallon jugs weren't available and we had to mark a metric jug. Assume 50 and you won't get in trouble. bd +++ #14554 From: Ken Beanlands Subject: More Fuel tanks, So, here's a question. Why not build the fuel tanks out of steel rather than aluminum? I've been trying to weld aluminum with mixed results, but I know that I can do a good job at welding steel. In addition, steel is less likely to fatigue crack than aluminum and is less likely to crack due to poor welding technique. Fiberglass has the issue of breaking down over time and heavier weight, unless using something exotic like carbon fibre or kevlar. Looking at the relative weights, 0.050" aluminum comes in at 0.75 lbs/sq.ft. 0.020" steel is about 0.875 lbs/sq.ft and 0.025" is about 1.1 lbs/sq.ft. Id one were to build the tank out of a combination of 0.020" and 0.025" would come in at about 1.0 lbs/sq.ft. So, for a tank that originally weighed in at 12 lbs, you would end up with a 16 lb tank with steel. So, the only two problems that I would see are how to clean up the inside of the weld after the last plaet is installed and what or how to coat the inside of the tank. This is not an unusual idea as most automotive tanks are made of steel. I'd love to get some feedback on this idea. Has it been done before? if so, wher? if not, why not. Am I missing something? is 0.020/0.025 too thin for a 25-27 gallon tank? Thanks, Ken Beanlands B.Eng (Aerospace) +++ #14555 From: Budd Davisson Subject: Re: More Fuel tanks, Welding .020, if you haven't done a bunch of it, can be a pain and distortion is going to be significant if welding with gas. But, I don't see anything wrong with steel tanks other than the rust problem and some extra weight. Now, I'll float another analogous question: if using steel and nothing but lapped joints (no butts), why not braze it with something like Eutectaloy (spelling?)? Easier to do and, in this application, just as strong with less distortion. As far as that goes, a lot of gas tanks used to be crimped and soldered. bd +++ #14556 From: Tony Dean Subject: Re: More Fuel tanks, I also seem to recall some that were spot welded and solder sealed. td +++ #14557 From: Russell Bell Subject: Re: More Fuel tanks, If you have a bead roller and a break and are willing to compound bend every corner for strength, it should work out. Notice that automotive tanks are pressed sections with center or top seam. That keeps water condensate from collecting inside a compound corner and rusting it out quickly. Make sure all bottom corners are bent, and preferably press the entire bottom to get laps at least an inch up. I've mig welded lots of .035, .020 seems very doable with tig or mig, probably torch weldable if you leave one layer about 1/16 long to melt back for heat sink. I've played with the idea of taking a two-bowl stainless sink, cutting the bowls out, tig welding them face-to-face, plug welding one waste outlet, and adapting the other as a filler. A 28 gauge 5 1/2" deep Home Depot special weighs 9 pounds. Cut to size without mounting flanges, should be under 5. Not much volume, though. (8" deep, about 7 or 8 gallons). If it seems to work out well, my next step would be checking with used restaurant equipment dealers to find a sink with large enough bowls to nearly fill the rib bay. (Don't wait on my experiments. A guy could get old.) Russ Bell +++ #14558 From: Del Rawlins Subject: tanks Since we are on the subject of tanks, I have a question for those of you who have built them already. How much aluminum did the standard tanks require, and if you built the extended range tanks, how about those? Thanks! -- Del Rawlins +++ #14562 From: pfflyerz@c... Subject: Re: tanks I bought 3 full sheets of 5052 to build my tanks because my calculations said I couldn't fit all the pieces on two. I now have two fuel tanks and a full, leftover, sheet of 5052. Pat Fagan #232 +++ #14570 From: "Bruce A. Frank" Subject: Re: More Fuel tanks, Steel fuel tanks used to be made with lead coated steel, which was the rust prevention process. Today everyone is so ridiculously paranoid about lead the tanks are coated with other less effective things. Lead coated steel is very easy to soft solder together and was very strong. Today aluminum coated steel is used in some systems and the tanks are flanged and welded with a rolling spot welded seam. Regular steel or stainless designed with flanged or lapped seams could be assembled distortion free with low temperature silver solder that would provide the strength and, at least on the stainless tanks, be corrosion free. There are quality sloshing compounds that will protect steel tanks for years and years even against alcohol containing fuels. Bruce A. Frank +++ #14572 From: Pat Fagan Subject: Re: tanks > Pat, did you build just the standard tanks or the extended range > tanks as well? I built just the two standard tanks. I built them to the newsletter dimensions and they ended up holding 30 gallons apiece. That was a nice surprise. Pat Fagan #232 +++ #14577 From: "Tim Anderson" Subject: Re: tanks I built both standard and aux tanks. I THINK, I used a sheet and a half. I was able to order a half sheet if my memory is correct. Tim Anderson +++ #14581 From: "rodsmith52" Subject: Re: tanks I was just trying to figure this out myself yesterday. I came up with a little more than 2 4x8 sheets for the four tanks. An extra 2x4 piece should be enough but would leave very little extra for mistakes. Rod Smith #246 +++ #14624 From: Russ and Penny Erb Subject: RE: tanks You probably remember that I did a calculation based on my drawings and came up with 25 gal per tank. However, the only fluid my tanks have had in them so far is air. If Pat says the gas pump charged him for 60 gallons, I'm not going to argue, but I may be a bit surprised. I wouldn't get excited until you build and fill your own tanks. Russ Erb +++ #14650 From: Bob Romanko Subject: RE: tanks Well, the reason I ask is up here range is everything. I'm interested in flying The Trench, and having said that I'm debating long-range tanks. Even 10 gallons matters. I'm wondering what the other folks who are flying Bearhawks are seeing for tank capacity. Budd, what capacity did you come up with? Planter Bob +++ #14652 From: Ken Beanlands Subject: RE: tanks I can't speak to the BH, but I would not hesitate to put in the additional tanks (especially with te monster radial you plan to stick on the nose ;-). The C-180 has about 7-8 hour endurance with full tanks and 65-70% power. Sure, "I bet you're thinking why would you ever want to fly for 8 hours strait, the bladder would never hold out". The reason (especially in your neck of the woods) is simple. If you plan to fly in the country for a fishing/hunting/camping trip, you will still need to come out after. So, a 7 hour endurance only gived you a 3.5 hour range. Now, what happens if the fishin's crap where you ended up. You'll need additional fuel to pop for destination to destination once your in the country. I've found the long range tanks on the 180 to be a god-send. You don't have to carry extra fuel in the floats or the cabin. Ken Beanlands B.Eng (Aerospace) +++ #14658 From: "Bruce A. Frank" Subject: RE: tanks > I can't speak to the BH, but I would not hesitate to put in the > additional tanks (especially with te monster radial you plan to > stick on the nose ;-). My philosophy exactly. Saw what had been intended to be a V-6 STOL in King Salmon about 7 years ago. The builder had quickly figured out that the Ford V-6 did not make the Blanton claim of 260 hp. He replaced it with a 290 hp 0-540 ( and extended the span to 37 ft). In the place of the original Piper fuel tanks (18 gal each) he had installed F.Atlee Dodge tanks of 30 gallons each. Then he created a new fuel bay just outboard of the new tanks and reinstalled the original Piper tanks..total on board fuel of 96 gallons. I have endeavored to duplicate that capacity on my project. Bruce A. Frank +++ #14662 From: Del Rawlins Subject: RE: tanks > Well, the reason I ask is up here range is everything. I'm > interested in flying The Trench, and having said that I'm debating > long-range tanks. For those folks planning to install the long range tanks, I'm curious what you are planning to use for a gauge, since sight gauges will only work for the main tanks in the wing roots. Is there a standard guage and sending unit that will work or is there some other method (other than switching tanks when the engine sputters). -- Del Rawlins +++ #14664 From: Bob Romanko Subject: RE: tanks I'm planning on installing a sight gauge as well as fuel gauges in the panel. Going with cap sensing something line this: http://www.imagineeringezine.com/PDF-FILES/capgage.pdf Planter Bob +++ #14666 From: Russ and Penny Erb Subject: RE: tanks This gets to why I was not interested in the extra tanks--the complexity of the plumbing goes way up. Kind of bucks against the simplicity principle. Russ Erb +++ #14670 From: "Bruce A. Frank" Subject: RE: tanks > For those folks planning to install the long range tanks, I'm > curious what you are planning to use for a gauge, since sight gauges > will only work for the main tanks in the wing roots. Why will sight gauges work only on the inboard tank? Another point about a question asked somewhere a couple of days ago, the top and bottom fittings of the sight gage incorporate valves to allow shutoff if the gauge is damaged. This diagram is crude and doesn't show all the nuances of valving, but you get the idea. The sight gauge of the outboard would be held in a bracket and its height adjusted so that its bottom coincides with the bottom of the outboard tank. Bruce A. Frank +++ #14671 From: "Dan Montee" Subject: Tanker Hawk I recall "the Bob" commenting that the best plumbing solution was not to plumb, just have a drain valve. Since the mains would go long enough that you were going to make a kidney stop anyway, the transfer could be made while on the ground. I thought that was a brilliant idea. Keeps things simple and opens up other possibilities for those outboard tanks for things like premix outboard fuel or potable water. Dan Montee +++ #14673 From: Alan Nauman Subject: Re: tanks > Why not just tie the two tanks together with a fuel ine and a vent? If you isolate the long range tanks, you can only fill up the mains for normal operations. You can also cut out the extra tanks in the event of a leak. Alan +++ #14674 From: Budd Davisson Subject: Re: tanks > Budd, what capacity did you come up with? We still need to do a more definitive study at the gas pump. We filled one with water using modified water jugs (marked in liters) and we're not convinced it was a totally accurate measurement. Our tanks are very slightly smaller (thinner) and we came up with 25 gallons a piece. I have a set made to the plans that we'll actually take to a gas pump some time soon. bd +++ #14679 From: Ken Beanlands Subject: Re: Tanker Hawk Another route would be to just use a transfer pump to pull fuel from the bottom of the aux tanks to the top of the mains. When a main tank drops to 1/4 full, pump in the aux tanks. It's a modification of the same principle. Since it does not feed the engine, there is no need for a guage, correct? BTW, I read that it's illegal to transport more than 20 gallons in the cabin of an airplane in the book I'm currently reading, "Flying the Alaska Wild" (which was quickly followed by the comment that most Alaskan pilots just ignore that one ;-) Ken Beanlands B.Eng (Aerospace) +++ #14681 From: Russ and Penny Erb Subject: RE: Tanker Hawk We took a few laps around the gas pump on this one before. Many people felt the hazards (mostly static discharge and fuel spills) outweighed any perceived benefits. Then again, I added a couple of extra hard points on the belly where I would be able to attach a belly pod if I so chose some day. If I ever decide I need more fuel capacity I may build a belly tank. It will add a little extra drag, but I won't be carrying around the extra weight of additional tanks and plumbing most of the time when I'm not using it. Russ Erb +++ #14683 From: "rodsmith52" Subject: Re: Tanker Hawk I will install the aux tanks but Russ's idea certainly has merit. Someone mentioned using pumps and that is what I will do. Certain models of facet pumps act as a check valve when shut off. I will vent the aux tanks separately and pump them into the main starting when it is down about a 1/4. That worked well on my Maule which used the same setup. Bob showed tying the two tanks together with a feed line and vent line between the two. That might work okay if you topped off the aux tank just before flying, otherwise due to wing dihedral you will have the potential for a lot of spillage out of the main tank. Yes it is a lot of added weight and complexity, but I think highly advisable for float flying in the north for the reasons Ken mentioned the other day. Rod Smith #246 +++ #14685 From: Del Rawlins Subject: Re: Tanker Hawk > Someone mentioned using pumps and that is what I will do. I had thought of using small transfer pumps but wasn't sure if that would be frowned upon or not. One issue that I can think of is the need for some way to keep the pump from running dry once the aux tank is empty. I am pretty sure that I don't want to drain fuel out of the aux tanks manually to fill the main tanks, that could be a real PITA on floats, not to mention the safety issues. I see the extra tanks as being a real plus up here, since they can keep you from needing to fly back to civilization just for more fuel. I'd be curious to know what the actual weight penalty is for an empty aux tank installation. -- Del Rawlins +++ #14688 From: Del Rawlins Subject: Re: tanks > Why not just tie the two tanks together with a fuel ine and a vent? In addition to the spillage problems mentioned by others, it will limit the level of fuel in the aux tanks to the level of fuel in the main tank. Depending on how much effect the wing dihedral has, that would preclude using the full capacity of the extra tanks. -- Del Rawlins +++ #14691 From: "Mark Goldberg" Subject: Re: tanks I guess I'll chime in with how I am setting up my aux tank installation. I am using Bob's vented caps on both tanks. The outboard tank fuel line goes to the wing root where it ties into the main tank fuel line, but with a manual valve that would be opened (from the cockpit) only when the main is at least 10 gallons down from full. The aux tank also has a vent line that goes to the wing root and T's into the main tank sight gauge line. So the aux tank has double venting as does the main. I believe gravity should flow the aux fuel into the main without a transfer pump. No fuel gauge on the aux tank. I will try the aux tank out for the first time when flying above a nice, big runway since this is definately an "experimental" installation. Mark in Austin BH#444 +++ #14697 From: "rodsmith52" Subject: Re: tanks Sounds good to me except for the extra vent line going to the sight gauge. I dont understand the purpose of that line since you will have vented caps. It has the potential of overfilling your main tank. Rod Smith #246 +++ #14699 From: "Bruce A. Frank" Subject: Re: Re: Tanker Hawk Adding additional fuel pumps, adding more complexity than just turning a valve is, to me, just asking for fuel management problems. Bruce A. Frank +++ #14701 From: Del Rawlins Subject: Re: tanks As it just so happens, in fuel systems class (I am an A&P student) this morning we were going through the FARs covering fuel lines and such, so I brought up this discussion about feeding the main tank from the aux tanks. My instructor mentioned that there are high wing installations set up with a pump like we are talking about, the reason being that a high wing plane often doesn't have enough dihedral to reliably feed the main tank from an adjacent aux tank using gravity alone, but a low winger will typically have enough dihedral that with a large enough feed line it works okay. I don't see getting around the complication if using the extended range tanks, at least if you want to keep the systems somewhat separated. Either there will need to be a complete extra set of feed lines going to the main selector valve, or a transfer pump to move fuel from the aux to the main tanks. If it is plumbed as a complete separate system with its own feed lines, then there will have to be another gauge system in addition to the sight gauges for the main tanks (I'm not comfortable running it dry and switching when the engine sputters). My way of thinking, is that with the pumps, there should be a way to make them automatically shut off when the aux tanks are empty, without adding an inordinate amount of complication. Part of the reason for doing it this way, is that other than the pump switches and wiring, the whole aux tank system could be contained in its tank bay, and thus would be removable if you don't need the capacity. If that gets to be too elaborate, I'd rather just run separate fuel lines and add a gauge to the panel. Then again, due to the dihedral issue my instructor mentioned, the flow that way might still be inadequate. -- Del Rawlins +++ #14706 From: Budd Davisson Subject: Re: tanks My take on gauges for the aux tanks is that everyone is making it too complicated. We don't need gauges for the aux's. I've had lots of airplanes with aux tanks and none had gauges. You knew how many gallons they held and how long it took to transfer that much fuel in to the mains by whatever system was used. So you simply flew that much fuel out of the mains, open the feed system and let it run 5 minutes longer than was necessary to get it all transferred, and shut down the feed system. I think we're complicating our lives here. bd +++ #14706 From: Del Rawlins Subject: Re: tanks > So you simply flew that much fuel out of the mains, open the feed > system and let it run 5 minutes longer than was necessary to get it > all transferred, and shut down the feed system. If that is all it takes that is fine with me; I just thought that it would be bad to run the pumps dry. -- Del Rawlins +++ #14707 From: "rodsmith52" Subject: Re: tanks Running the tanks dry never seemed to harm the pumps in my Maule. There is a setup available that will detect when the pumps start sucking air and will automatically shut them off. I will try to find the info and post it. Rod Smith +++ #14709 From: Tim Subject: Re: Tanker Hawk > Then again, I added a couple of extra hard points on the belly where > I would be able to attach a belly pod if I so chose some day. If I > ever decide I need more fuel capacity I may build a belly tank. I've always liked this idea......Kitfox/Skystar had this baggage pod option, so a little work and you are hauling fuel......A guy did this with his M1, carried 10gals in an old radar pod right on his CG...eliminated an Oshkosh stop. 321Tim +++ #14719 From: Budd Davisson Subject: Re: Tanker Hawk Think about all that fuel under you when you loose an engine. Sorenson spray rigs were usually jettisonable for that reason. bd +++ #14722 From: Russ and Penny Erb Subject: RE: Tanker Hawk Everything in flying has a risk associated with it. Each pilot gets to decide how to mitigate those risks. If you know you're going to fly far enough to run out of fuel without the extra tankage, that may be a risk you're willing to take. Besides, remember where all the fuel tanks are on the much exalted Beaver... Russ Erb +++ #14729 From: John Dougherty Subject: RE: tanks I once had a piper colt with dual wing tanks. The proceedure I was taught was to take off on the main tank, then switch to the auxillary tank for an hour, then back to the main for another hour, then back to auxillary till it was dry switching to the main when the engine sputtered. The engine always picked up immediately. This kept the aircraft balanced to a degree and you always had all remaining fuel in the main tank for landing or takeoff. I know some people would have a problem with this approach, but I was taught this by a bush pilot with many thousand hours. He is still flying his homebuilt cub 32 years later and still uses this proceedure.........John +++ #14746 From: "rodsmith52" Subject: Aux tank pumps For those considering the use of pumps to get fuel from the aux tanks to the main tanks. Pillar Point Avionics makes a pump controller that automatically shuts down the pumps when the tanks are dry. It senses this by the change in current when the pump starts sucking air. www.ppavionics.com They also sell the facet pump model that provides fuel flow checking in both directions when the pump is off. All I know about the company is what I read on their website. My friend purchased this setup for his Glastar but he isn't flying it yet. Rod Smith #246 +++ #15547 From: Bob Romanko Subject: RE: Extra fuel tanks (was: P-Bob in the trenches) >>> Mike Vivion explicitly says "(8) Stay away from super big gas >>> tanks: maintenance issues, lessen resolve to fly light, difficult >>> to gauge fuel." >> That's interesting, because every Alaskan pilot I have spoken with >> has told me in no uncertain terms to install the extra tanks. > Well, I tossed it out there to be controversial. I think part of > the point was that extra fuel allows you more options. Too many > pilots, allowed more options to choose from, 'choose poorly.' Something I never really thought of before is the vast majority of neat places where one would want to fly in Alaska does NOT have fuel available. When I lived in Virginia I planned my trips with a three hour endurance. Here I've had to cut it in half, and then some. 'Course, I haven't GONE to any of those places yet, but when you look at a sectional, plot the distance (don't forget that big loop you have to make through a pass or two) and figure for wind, auxiliary fuel tanks seem to be essential. Makes me think more about fuel efficiency than brute power. Then again, once you get to those places and are flying out gear and a quartered moose, it's not a bad idea to have the extra horses...then again that would add even more weight...but then....aww..forget it! Planter "Fuel is a GOOD Thing" Bob +++ #15744 From: Del Rawlins Subject: Re: Fuel Tanks... > I apologize if this has been discussed, but i couldn't find anything > on the primary tanks only aux. in the archives. I was just > wondering what means (wet-wings, bladders etc.) of fuel storage the > bearhawk employs. If anyone has pictures that would be nice. Drawings of the main tanks were published in the Bear-Tracks newsletter, and will be in the back issues included with the plans. They should also be on Russ' CD. If you haven't seen either they are constructed of .050 5052 H-32 alloy, and contain roughly 27 gallons each. -- Del Rawlins +++ #15929 From: "Mark Conover: Subject: Pat's Gascolator Pat, Are you using the Andair Mini Gascolator? If so, did you go that route due to size constraints? http://www.andair.co.uk/gas/mini.htm Thanks, Mark Conover +++ #15934 From: pfflyerz@c... Subject: Re: Pat's Gascolator No I used the regular sized 3/8 line Andair gascolator. The mini is listed to only 150 HP. The larger one fits under the floor just fine. Pat Fagan +++ #16188 From: "Bruce A. Frank" Subject: Re: Longer range Bearhawk? > If you wanted some really long legs, is it feasible to install > another fuel tank in the "baggage" area? Size would depend upon how > many miles you wanted to travel I suppose. Any ideas on max range > that way? Why? If you desire a longer range craft create another fuel bay in the wings just outboard of the existing tanks. Unless you are ferrying a plane why live with the increased danger of an in-the-fuselage fuel tank. Certainly if you stay within the luggage compartment limitations of weight it makes no difference whether it is a tank containing fuel or a rebuilt 0-360 engine sitting there. Other wise it's a homebuilt. Put the fuel tanks where you want. Wing tanks have been shown to be safer in a crash. Wing tanks are on or very near the cg or center of lift. From a W&B stand point there is also no better location than in the wings. Okay, okay, I'll quit pontificating. Bruce A. Frank +++ #16197 From: Budd Davisson Subject: Re: Longer range Bearhawk? If your going to put another aux tank outboard of the existing one the spar caps should be run clear to the tip. Bob has mentioned this but check with him anyway. Wing tanks are free weight until you land. bd +++ #16246 From: Del Rawlins Subject: RE: Longer range Bearhawk? > As I recall, the tank were built for Proto II, but never hooked up. > Other than form/fit/function, I don't think those tanks were ever > used for anything. They may never have even flown. If someone has > newer/better info, feel free to correct me. Wasn't Bob using them to ferry fuel back to Barrows Airfield? I don't think he hooked them up to the fuel system, but it seems like he was flying with fuel in them. -- Del Rawlins +++ #16891 From: pfflyerz@c... Subject: fuel capacity I finally have hard data on the fuel capacity of the standard tanks. I was able to put 26 gallons in each tank. Of that 26 gallons, approximately 1 gallon is not useable. I was able to burn all but 0.6 gallon out of the left tank, but that required having the engine sputter four different times. Also, bumpy air affected how soon the fuel ran out. In a pinch, you could probably get even more out by flying in a slip. When checking the right tank, I switched tanks at the first engine sputter, then drained the remainder and came up with 1 gallon. Pat Fagan +++ #16900 From: Del Rawlins Subject: Re: fuel tank -- was capacity > I'm sure it's in the archives somewhere, I just couldn't find it. > How are the fuel tanks constructed, is it just a wet wing, is it > removable -- how are the fuel pick-ups set up -- is there enough > dihedral in the wing to separate the water to one point -- are there > any questions I didn't ask? The Bear-Tracks back issues contain all of this information. The fuel tanks are welded .050" 5052-H32 aluminum, held in place by steel straps. A wet wing system would be theoretically possible, but you'd have to design it yourself. -- Del Rawlins +++ #16902 From: Pat Fagan Subject: Re: fuel capacity > Another thing to consider, is that when unusable fuel capacity is > determined for certification purposes, they typically use some worst > case situation for the tank being tested, like a climbing turn to > that wing. In that case you had better up the figure for unuseable fuel. I did steep turns and climbs while sucking as much as I could out of the left tank. On the right tank, I wanted to see how much was left when the engine died in level flight. A little turbulence was enough to get the fuel moving and cause a premature sputter. I'm going to use the 1 gallon figure for flight planning and CG purposes. I always use BOTH on the fuel selector for take-off and landing if either tank is low. In a pinch, I will use whatever manuever allows the last few drops to be used. As a side note, I have a fuel flow indicator intalled. I noticed that the turbine wheel starts to cavitate, causing the fuel flow numbers to go crazy, before the engine exhibits its first coughs. That is a convenient little warning that you better switch tanks very soon. Pat Fagan +++ #16923 From: Russ and Penny Erb Subject: RE: fuel capacity That's more in keeping with the volume I calculated from my CADD drawing. I think I had come up with 25 gallons per tank. Russ Erb +++ #17032 From: Ken Beanlands Subject: More thoughts on tanks and floats I was out for my daily walk and my thoughts turned to flying and the Bearhawk (not a stretch there ;-). I was thinking about the fuel tanks (I just picked up my fully welded Christavia tank this morning), more specifically, the extended tanks on teh BH. a couple of things occurred to me that may be of some interest: 1. Extended tanks are only really needed for float ops, wheeled ops usually begin and end at an airfield with fuel available and seldom exceed the 3-4 hour+ endurance available with standard 54 gal tanks. 2. Once on floats, the extended tanks, as designed, are not that useful. Anyone that has fueled up a C-180 while on floats knows that you pretty much have to climb on top of the wing to fuel it. The extended tanks would require crawling WAY out on top the wing and could damage the skins or, worse, tip the plane (especially with the right wind). Remember, not every refueling will be at a nice dock where you can use a ladder. In fact the only time I EVER ysed a ladder to refuel the 180 was when we were on Toronto Island and the plane had been pulled up out of the water. 3. Having that much fuel out in the wing tip could cause some trouble if one of the transfer pumps failed leaving you with one empty and one full tank. 4. Carrying fuel in the cabin is not that appealing and has it's own set of problems. 5. Refueling from fuel cans all teh time is a MAJOR pain in the butt. 6. 54 gallons is not really enough for serious float/bush ops with an O-540 up front to feed (doubtful that you can get awat with the Bob's econocruise settings with 300-500 lbs of draggy floats strapped to the bottom ;-) Given all that, I cam to the conclusion that, for me, the extended wing tanks are not that appealing and carrying fuel jugs either in the cabin or in float compartments is not that appealing either. It occurred to me that the best place for the extended tanks is...in the floats. A pair of 12"w x 20"h x 15"l tanks (15 gallon capicity) could easily be installed in a float compartment in each float and then plumbed back up into the wing tanks. A hatch would need to be installed and the tank shape would have to have a sloped floor so that the front was lowest (most pilots beach their planes with the tails on shore). The tank would need to be placed toward the top and rear of the float compartment with enough room below the tank for a drain sump. There would need to be enough room at the front of the tank to reach down and drain the the sump to check for water. a pair of fuel pumps would be used to fill the main tanks. Fuel caps/filler necks would need to be mounted so that they were not on the deck, probably under a hatch. Vent and fuel lines would be routed up inside one of the float struts with a disconnect at the fuselage. One last thing for you guys planning to install floats. Make life a little easier for yourself and install a sturdy step about half way up the side of the fuselage in front or at the door post station. That, with a step on the front float strut will make it easy to perch yourself to refuel the tank. A handhold on top of the fuselage is also helpful. THe 180 has the liftin gring strategically placed to act as a handhold, the BH could be the same. One other nice feature that I've never seen used would be some sort of fold away step ladder that could be installed in the top of the floats for refueling.... Just some thoughts. Ken Beanlands B.Eng (Aerospace) +++ #17033 From: calbru@a... Subject: Re: More thoughts on tanks and floats I'm not planning on having floats, but having heard some of the options for plumbing the aux tanks, it occured to me--"why not just "hard" plumb the two tanks together with a 3/4 or 1" pipe at the bottom of the tanks." Then, just treat each side as one large 35, or so, gallon tank. Both caps could be vented and fueling could effectively take place with at just one of the tanks. A filler sleeve (tab) or dip stick could be used when fueling if less fuel/weight was desired. My 182 has 88 total gallons (44 per side) and up to the tabs is 33 per side--sounds too simple to be true! Thoughts??? Cal B +++ #17035 From: Ken Beanlands Subject: Re: More thoughts on tanks and floats The real problem is that the tanks are quite far apart. Remember there's about 8'-10' between the main and aux tanks. This will really offset the lateral balance if you spend too much time in an extended bank and present a very complicated plumbing problem for venting and feeding the engine. Keep in mind that with the 180 (and I presume 182 as well), although there are two filler necks per wing, there is only one large L-shaped fuel cell inside the wing itself and that tank only makes up about 3'-4' of span. Having helped replace one, I was quite suprised to find that it was not two tanks. Ken Beanlands B.Eng (Aerospace) +++ #17043 From: "Bruce A. Frank" Subject: Re: More thoughts on tanks and floats The picture I posted on the Bearhawk site of the V-6 STOL on floats (the chain link paint job with the maple leaf on the tail) has no fuel tanks in the wings or fuselage. Mike Hirshfield built the floats to contain the fuel AND a nitrous bottle with heater. The nitrous helps get out of high altitude lakes. Bruce A. Frank +++ #17046 From: Del Rawlins Subject: Re: More thoughts on tanks and floats > it occured to me--"why not just "hard" plumb the two tanks together > with a 3/4 or 1" pipe at the bottom of the tanks." Then, just treat > each side as one large 35, or so, gallon tank. That was the arrangement originally recommended by Bob Barrows when he first published the aux tank drawings in Bear-Tracks. -- Del Rawlins +++ #17090 From: Del Rawlins Subject: RE: More thoughts on tanks and floats > If you fill by an outboard cap, and then open an inboard cap, all of > the fuel above the inboard cap will gush out all over the top of the > wing. Yuck! That is precisely why I want to use a pair of small pumps to transfer from the outboard tanks to the mains. I figure I will worry about fueling the outboard tanks when I get it on floats. Most of the places I will be going, will be out and back situations where I am fueling at a fuel dock which should hopefully have a ladder anyway. Depending on the dock, it may be necessary to turn the plane around to fill the tanks on the other side. I don't know the Beaver all that well, but I've seen it posted here that it carries all its fuel in the fuselage. I suspect that is one of the reasons it makes such a good floatplane. -- Del Rawlins +++ #17092 From: Russ and Penny Erb Subject: RE: More thoughts on tanks and floats Yes, but not all. The primary tanks for the Beaver are three tanks under the cockpit floor. All of the filler caps are together in one panel on the left side just behind the passenger door (assuming I remember correctly). On the Beaver we had at the USAF Test Pilot School many years ago, the wingtips were auxiliary fuel tanks, even if we never used them. They're also a little tough to fill on floats without a dock. DeHavilland designed the fuel system that way precisely so it would be easy to refuel while on floats. Yes, it needs a fuel pump to get the fuel up to the engine, since gravity doesn't work backwards. That's probably why there was a wobble pump in reach of the pilot as a backup. It all makes sense when you remember that floats are the primary landing gear for the Beaver as designed. Wheels are the secondary landing gear. Russ Erb +++ #17204 From: Russ and Penny Erb Subject: Routing Rear Fuel Lines For Pat or anyone else who has run fuel lines-- Could you please describe how you ran the rear fuel lines from the tank to the fuselage and then down the door post? Part of the fun is that it has to get past the flap actuation stuff and around the wing attach point. I think I've figured out how to run it on the left side. On the right side, did you run the fuel line inside the channel between the door and cargo door? If so, where does it enter at the top? Is it below the rear door hinge? Does it go in from the front or back? Pictures would be the ideal way to answer this, but if you don't have those, please try to describe it in words. Russ Erb +++ #17210 From: pfflyerz@c... Subject: Re: Routing Rear Fuel Lines Russ, too bad you didn't ask that question yesterday. I noticed a little fuel stain on the left side so had everything opened up see where it was coming from. Turned out to be the top sight tube hose clamp was a little loose. You're right, it is a little tricky running the rear line around the wing fitting and the flap actuator. I have a rubber fuel line, about 6" long that connects the hard tube coming from the tank to the one running down the fuselage. The original plan was to run the flex line under the flap arm, but I found the room insufficient between the arm and the wing fairing. I tried running the line over the arm, but couldn't get any fuel to flow in the line until I had 5 gallons of head pressure. I went back to the original plan and ran the line under the arm, but protected it with nylon sheet where the arm rubbed against it. The left side tube is the easier of the two to run, just tuck it behind the door jamb. I tried making a single length tube to run from the top of the fuselage, all the way to the T at the front door post, but found it to be too unwieldy, snaking through all the structure. I finally cut the tube and put a junction fitting under the door sill, just ahead of the rear door sill. I have an access panel in the interior to check the fitting. Due to the way I welded the bracket for the front T fitting, I had to make an access panel on the outside of the fuselage boot cowl to have access to the B-nut coming from the rear tank. I highly recommend you design in the ability to not just check the nuts, but be able to tighten them, as they never seem to be tight enough. After much Proto 2 scrutiny and head scratching, I finally realized that Bob ran his right fuel line down the outside of the cargo door piller, in the passenger compartment. You can't see it because he fabriced over it. I did the same, but left it visible. Once you come to that realization, you simply have to deal with the same problems presented by the left side. Although, there is the added fun of having to make a large enough hole through the cargo door pillar/sill junction and through the lower front portion of the door pillar to allow your hardware ( I wanted to say nuts) to pass through. A big file and a lot of elbow grease finally solved that problem. If that isn't clear enough, I'll show you the pictures when you bring your dad by. Pat Fagan +++ #17247 From: "doug" Subject: Re: Digest Number 1246 Sonny, link below is for the fuel caps. I added a flange to faciltated a fillet weld joint to the tank top. The test sample was welded to .050. This eases any distortion on the fill neck and allows for not so perfect hole the tank top. In the spirit of getting the economy going I have deduced the price on my remaining stock.....$100 pair plus $7.50 shipping http://www.geocities.com/doug_knight_94501/Fuelcaps/Pic1.html Doug +++ $Id: 2.5.1-Systems-Fuel,v 1.13 2003/05/22 03:32:05 bentonh Exp $