+++ #492 Subject: Re: fuselage jigging From: Rodney Smith Here's how I got the horizonatal measurements for the top and bottom of the fuselage. The tail post is vertical and perpendicular to the centerline depicted on drawing 16 so use that as your reference. Use a square on drawing 16 to bring the horizontal position of the top and bottom crossmembers to the centerline. Then you can see the correct relationship from top to bottom and measure their horizontal distance from the tailpost. Seems like when I did this I found a minor error on drawing 17 which I was going to mention to Bob. Now I cant remember what it was. +++ #493 Subject: Re: TIG From: Bruce A. Frank Has anyone ever thought about how much asbestos dust you inhale while standing on the corner of most any city? The amount of radiation you ingest in one cigarette? The amount or radiation exposure from one dental X-ray? The amount of excess cosmic radiation one receives by living so far north where the earth's magnetic field dips towards the surface, as manifest by the ionization display refered to as the Aurora Borealis? Two percent thoriated tungsten dust presents less hazard than the silica dust you inhale while following a vehicle down a dusty trail or the mold spores you stir out of the everpresent mouse droppings disturbed when you sweep or vacuum your shop floor. The aflatoxin in every jar of peanut butter you've ever eaten will get you before 2% Thoriated tungsten will. Every bottle of beer you drink kills about 10,000 brain cells. Man, the risks are so numerous one should probably stay in bed, but then those dust mites in the mattres.... Do you really know the risks of dying every time you fly?? +++ #608 Subject: Re: Interested builder From: Archie Dunbar >Re: Tubing notchers >Everyone has their own style of putting tubing together and y ou'll >develop yours. Don't get so caught up with gadgetry, however, that it >slows the project. So true, I tried the joint jigger method and the mill method on my lathe. It is not worth it. It is the same as the rib concept. Better to spend a little time and learn the art. I use the dressed grinding wheel and my fuselage is almost complete. I try to rough cut with a metal cutting wheel in my table saw and then fine tune it with the grinder. I also use a die grinder on a limited basis. Just curious, Budd, what is your definition of a rediculous fit? +++ #618 Subject: Re: Notching tubing hint From: bearhwk27- Here is a handy method that will greatly speed up tube fitting and results in accurate fit ups. I will try to describe this but it is in text books on large pipe fitting, maybe at your library. Assume a pair of simple joints. Upper and lower longeron parallel with a vertical upright at 90 deg. Tubing dia and wall thickness same for all elements of the joint. 1. Measure vertical distance CL to CL. 2. Cut the vertical piece 1/16 longer than CL to CL of the longerons. 3. On one end of the tubing make two saw cuts at 45 deg from CL of tube at end of tube. The end of the tube now has an end with a point 90 deg included angle. The tube should now form a saddle that will not quite sit down on the longeron. Grind back the points and relieve the inside edge with a rat tail file. Tubes should now fit snugly without any gap. Repeat on other end, watching orientation. If you do this correctly you will say, so what, yea it works but there is not a joint on the airframe that looks like this! Here is the key..... If you have a joint with two tubes and the acute angle is say 40 deg to the longeron. Measure CL to CL intersections. Cut the tube off square to that dimension. Make your first saw cut from center line at 20 deg off the center line. Make the second saw cut at 90 deg to the first. The first cut is always 1/2 the intersecting angle of the two tubes. The second cut is at 90 deg to the first. There are limits where this starts not to work, extreme jumps in tube size or very low angles but for most of our work this will rough it in. Once you get the hang of it is easy to compensate for various different tube and wall thickness situations. +++ #620 Subject: Cutting Tubing From: Todd Chisum >I try to rough cut with a metal cutting wheel in my table saw and then >fine tune it with the grinder. Another way to rough cut 4130 steel tubing, get a pipe cutter from the local hardware store (the kind that looks like a c-clamp). They cut through the 4130 real easy and leave a smooth edge. No noise either! +++ #671 Subject: Re: BHawk Airfoil.... From: Mike Meador On another note I am trying to gauge the possibility of offering a pre-welded Bearhawk fuselage. Carl Adams is no longer offering them - I think he only sold the one. It is just an idea right now, but I talk to enough builders at the fly-ins and on the phone that I think I might be able to offer one. Like I say it is just an idea right now but if you are interested please reply by private e-mail and we can discuss it. +++ #1083 Subject: Re: fuselage width From: Rod Smith I talked to Bob about this probably a year ago. As I recall he said you can go 1" wider using the 170/172 windshield. I plan on building mine 1 1/2 " wider and using a 182 windshield. My reasoning behind this is the Bearhawk is the same width as my Maule was. I was always cramped in that while winter flying with a friend, both of us in parkas. For most purposes it is probably wide enough. Another option would be installing bubble windows on the front doors, they provide great visibility straight down also. Probably best to call Bob and get his latest thoughts on this. +++ #- [ See -Mods file for more on adjusting fuse width. ] +++ #2173 From: Mike Eldredge Subject: Welding fuse clusters How does one determine the proper order to weld the tubes in the fuse? Of particular concern to me are the diagonal tubes in a square. It seems to me that if a diagonal is left till last, you will have a hard time getting it into place because of its length. Is there a step-by-step welding order for the Bearhawk fuse, or what is the general principle behind it? If I were to come up with the method myself, I would tack the perpendicular members to a longeron, then add the diagonals, then attach the opposite longeron. When doing an 'x' shape in a box, is one cross member whole, and the other cut in two and welded to the middle of the first? Does it matter which is whole and which is cut? (maybe I better get my hands on some books...) +++ #2176 From: bearhwk272 Subject: Re: [Bearhawk] Welding fuse clusters Getting books is a great idea. Check EAA for Tony Bingelis book series on Sport Plane Construction, and Performance Welding (I think Fink). For Bearhawk specific the Russ Erb CD and Bill's website. Fuselage should not have major welding until all tubes are in and tacked solid. The diagonals must go in as the box is built and they go in in one piece. +++ #2627 From: Subject: fuselage welding I just tacked the last structural tube into my fuselage and am looking forward to finish welding it together. I have been scouring the books and archives to find out how to do just that, but am still somewhat confused. Bob says to weld it from the tailpost forward, a station at a time, which is fine with me as I can probably get past three stations with the frame still in the jig, but what happens after that. If you weld the thing on a rotisserie, should you put it back on the table after welding each cluster to check alignment? When welding a station, do you weld a cluster, then move to the diagonally opposite cluster next, or just work around the station in a circle? Some clusters have 5 or more tubes in them. That is a lot of heat being inputted on one side at a time. Should you weld the whole cluster at once, or skip around the other clusters in that station, doing a tube or two at a time? When welding a many tube cluster, do you weld completely around a tube before moving to another, or should you skip around the various tubes? Binghellis has a discussion about order of welding, but it didn't really make any sense to me. Any advice you can provide would be greatly appreciated. +++ #2628 From: budd davisson Subject: Re: [Bearhawk] fuselage welding Pat, all good questions and there are no exact answers as everyone has their own way of doing things. However, you've caught most of the serious questions. My method has always been to work a station at a time in a rotary fixture. Incidentally, make sure your tacks are solid because tube movement can actually break them. I also don't weld the entire cluster. There's usually a logical breaking point in each cluster. If there's a vertical, do everything behind the verticle then move diagonally across the station and do everything behind that verticl. Go around the station behind the verticles then around it in front. Although, I've welded fuselages where I did the entire cluster and it didn't seem to make that much difference. The most important thing is that you don't go down one side of the fuselage and then the other. You'll wind up flyign in circles 'cuz your tail will be so far out of line. Incidentally, the reason Bob says go from the tail to the front is that it puts all your bad welds at the back and all the good ones, when you're really in practice at the front, where they're needed. I don't know what the other guys do, but I also make it a practice when welding on oneside of a longeron, to heat it up on the other side too, almost to welding temperature, which helps limit the shrinkage a little. Them's my thoughts. +++ #3088 Subject: Re: getting re-started From: Rod Smith > I finally bit the bullet and sent in an order for tubing to > Dillsburg. I'm so exited to get started (re-started) on the > project. The aluminum thing just didn't spin my wheels, so I am > holding out for the wing component kit. (wimpy, I know) I have a > question for anyone who may know something about the fuselage > tubing. Dillsburg doesn't and hasn't ever stocked 3/8" .095 wall > tubing according to Mr. Vogelsong. He's asking if I want to order > .083 wall or .120 wall instead. Does anyone know where I could get > the .095 tubing because he makes it sound like he supplies all the > other companies that sell it, so if he doesn't have it, nobody > does. Any help would be greatly appreciated. I appolagize if this > is something that has already been addressed in the group but > after looking through 100s of old posts, I couldn't find anything > specific. Glad to have you back and building Tom. Two sizes that no one seems to have is 3/8x.095 and 9/16x.095. You will want to go with the .120 and for bushings, drill and ream it to the correct size. My trick to keep the holes centered is to use a drill bit that just fits in the tubing to align and clamp the tubing in the drill press. With out moving anything slip the necessary drill bit in the chuck and drill it out. I use the same proceedure with a reamer. +++ #3184 Subject: [Bearhawk] pressurized steel tube fuselage From: Russ Erb > Has anyone out there heard of pressurizing their fuselage tubing? > Maybe Bud has heard, being familiar with some of the aerobatic > planes. The idea here is that the fuselage is a pressure vessel, > charged with aproximately 100 psi of nitrogen. This "vessel" has > a panel mounted gauge that displays any drop in pressure > indicating tubing or weld cracking. My brother has read up a bit > on it in the aerobatics mags and thought it might be worth some > consideration for use on the Bearhawk. I haven't read the > articles yet so I haven't formed a complete opinion on it, but it > does sound like a descent idea for a reletively minimal time and > money investment. Anyone care to comment? I remember going through this discussion within the last year. Maybe I'll find it when I index everything for the CD. As I recall, one of the points made was what were you going to do when you suddenly lose pressure? Let's assume the leak was through a small pinhole which did not threaten structural integrity. To repressurize the fuselage, you would have to track down the leak, remove the covering from a significant part of the airplane, re-weld, re-pressurize, and re-cover. Yuck! On the other hand, if you used line oil in your tubes, the results would be much different. The preparation is the same with drilling all of the interconnecting holes. Line oil coats the inside of the tubes, preventing corrosion. In the case of the pinhole leak, the oil comes out of the hole and congeals, effectively sealing the hole. Possibly the oil would stain the covering, which would have the beneficial effect of alerting you to the "problem" for evaluation of its need for attention. The pressurized idea is popular among the aerobatic community because of the way they operate their airplanes. They regularly stress their aircraft near the limit, which most of us who don't land on gravel sand bars in box canyons won't. But look at their maintenance regimen--I don't know about anyone else, but Sean D. Tucker strips the covering from his airplane EVERY YEAR for complete inspection, repair, and re-cover. Our risk of structural failure is significantly less. For my situation, pressurizing the fuselage with nitrogen has more problems than benefits. I'm going with the line oil myself. +++ #3185 Subject: Re: [Bearhawk] pressurized steel tube fuselage From: Bruce A. Frank Please tell me what you are going to do to your painted and fabric covered fuselage when the pressure drops? An aerobatic plane is a different situation. It is very highly stressed structure. In flight catastrophic failure under such loading is possible if there is a crack in a strategic component. Tube truss structures such as the Bearhawk and all other similarly constructed planes (PA-22, PA-14, PA-18, Bushmaster and so on) are considerably overbuilt for the service they see. They don't "fall apart" even when poorly welded. In this type construction no single, and in this case, even any two points of failure is going to lead to the aircraft coming apart. The structure itself is multiply redundant in all parts supporting the loads. The structure is a mechanical devise designed to handle landing and flight loads far beyond the most careless abuse. It is not a gas pipe line put together with 100% penetration key hole welded beveled-butt joints. When the gauge leaks down are you going to retire the plane? I have used pressure to find pinhole leaks in clusters of my welded structure. I plan to coat the internals of the tubes with linseed oil to plug any pinholes that may open from flexure. I have been contemplating this pressurization procedure for years now and have heard dozens of pro and con arguments. I embraced the idea early on in my project, but after helping to build many welded tube structures and cut apart dozens more, including a Pitts, I don't see that pressurization offers anything except something more to worry about. I have read an article several years ago that debated the quality of homebuilt welded fuselages. The article made a point that essentially full strength of the total structure was achieved with only 20% of each joint welded, another indication of the overbuilt specification of these tube structures. I expect my fuselage, and trust my welding, to last my lifetime (no, there is no gallows humor there) with no methods beyond those used (or needed) by the earliest tube structure planes. Let me know what all of you think or know about the value of pressurization of a tube fuselage in standard flying operation. +++ #3563 From: Tom & Michelle Brant Subject: 4130 welding... again Thanks to everyone who responded to my questions about filler rod and 4130. I will have to discuss the filler rod issue with my brother who's doing the welding but I wanted feedback from those who are building this particular plane. I'm planning to work on the fuse bottom today, filling in the cross-members and diagonals (right now we're just tacking stuff in) so I will get the specifics of the filler rod we're using at this point. As far as heat treating goes. I do plan to "stress-relieve" the welds after they're completed which is recommended for tig welding. Is this the same thing as heat treating? I wish I would have participated in the welding discussion that happened a few years ago. Another question that wasn't answered... For those of you who've already formed the top fuse section are you using the same method with the longerons as the bottom longerons? IE: a smooth radius. As I mentioned before I bent up the longerons at first with a bunch of small bends instead of one long radius and later remembered the newsletter mentioning that it's supposed to be a long smooth radius on the bottom. I haven't seen anything that covers the top longerons though. I have since reformed the bottom longerons. +++ #3564 From: Subject: Re: [Bearhawk] 4130 welding... again I formed my top and bottom longerons with a long sweeping curve. I got them to fit with minimal force required to maintain their position after forming. As for bending the top longerons in the vertical plane, I asked Bob about that, because I couldn't figure out where or how to make the bend to get the right dimension and angle for the door post tubes. He recommended bending the upper framework, on the floor or the table, to get the rise depicted on the plans, which would then automatically put the top frame in its proper alignment when place against the tailpost. Incredibly, it worked just as he said. For everyone's future reference, I am attempting to install my wing spar attach fittings on the fuselage. I was wondering where to check the angle for the 2 degree angle of incidence. My top longeron is at a 3 degree angle with the fuselage level. I checked a sine table and a 1.5 inch rise over a 32 inch length, as depicted on the plans, results in a 2.75 degree pitch. This made me wonder if the rod through the fittings should be set to parallel the top tube, or set at a 2 degree angle. I again asked Bob and he said the important dimension is the 1.5 inch rise. Set the rod parallel to the top tube and with the spars installed, the wing will come out at a 2 degree angle. He also said that the exact angle is not so critical, as long as both wings are set at exactly the same angle. +++ #3897 From: William & Delinda Johnson Subject: 023 Update & Stuff My bearhawk is also going to use aluminum bulkheads under the floor instead of the T3 tubes called for on the plans. I will post pictures in a couple weeks. After having to lift my petite wife into the Bearhawk, I have decided on a step. Once I get the details, I will let the group know. Without a step, I will look like either a gallant man lifting my wife into and out of the plane or a terrible husband for not making a step. It could go either way, so a step will ensure I am viewed as a reasonable and loving husband. The hard core bearhawkers may disapprove but I don't have to sleep with any of you (smile). +++ #3901 From: BRUCE A. FRANK Subject: Re: 023 Update & Stuff > After having to lift my petite wife into the Bearhawk, I have > decided on a step. The Bearhawk gear leg does not lend itself well to an attached step, like a TriPacer, because it is forward enough that the lift strut interferes with the step in. The Cub stirrup style step would be too high to be easily use by many smaller people. What I have seen that works well and is also low drag is fabricated from about 14 inches(or more or less) of streamline tubing. Take approximately 10 inches of the streamline tube and weld it to the lower longeron; pointed at the ground at the same angle as the main gear. I'd locate this along the longeron at about the mid point of the door (roughly a foot to 18 inches from the lift strut attach point). Then take the remaining 4 inches of streamline, coped to fit, and weld it to the lower end of the 10 inch piece. The 4 inch piece should be parallel to the ground and perpendicular to the centerline of the fuselage (sticks out just like the axle on the end of the gear leg. The elliptical shape of the tube should be oriented so that its cord line is parallel to the flying slipstream. Cap the end of the 4 inch step with a flat piece of steel that sticks up about 1/4 inch above the surface of the tube to provide a stop to prevent a foot from sliding off the end. Additional bracing may be added from the attach point on the longeron to another vertical or horizontal component of the fuselage to eliminate worry about the users weight twisting the longeron. This step is mostly in the wind shadow of the gear leg and all components are streamline keeping drag low. I'd glue on a wrap of mineral grit no-slip material to the step tread. (My wife really likes this step: wants one on my fuselage) I have also seen a piece of streamline welded to the aft down leg of the main gear(near the pivot of the gear); kept in the same plane (geometric)as the gear but sloped towards the tail of the fuselage. The step is then welded to the end as was described above. This design looks awkward to me, but to each his own. Some people, trying to reduce drag more, will (instead of the outward sticking streamline 4" tube) weld on a piece of round tube to the aft edge of the down-angled leg making a step that is in-line (pointing aft) with the leg and parallel with the longeron. Many (myself included) find this style step less comfortable to use. +++ #3903 From: Russ Erb Subject: 023 Update & Stuff > My bearhawk is also going to use aluminum bulkheads under the > floor instead of the T3 tubes called for on the plans. I will > post pictures in a couple weeks. Bill--could you tell us your reasoning for this change? What do you hope to gain by it? For once, neither the pros nor cons of this idea occur to me. +++ #3904 From: Russ Erb Subject: Re: 023 Update & Stuff Bruce had some good words. I'll say this to inspire thinking, but I'm not sure the additional weight or complexity would offset the drag reduction. I saw on the factory KIS Cruiser a retractable step. After getting in, you reach down to a handle and pull the step up into the fuselage. I don't immediately see a good way to do this, having visions of a pipe sticking into my ribs... +++ #3906 From: Float-By Shooter Subject: Re: 023 Update & Stuff > I saw on the factory KIS Cruiser a retractable step. After > getting in, you reach down to a handle and pull the step up > into the fuselage. It's interesting that you should mention this, because I was just thinking about a way to do the same thing. Maybe a tube within a tube arrangement, streamline so that it wouldn't rotate? If you wanted to get fancy, a button on top that would operate a locking pin. > I don't immediately see a good way to do this, having visions > of a pipe sticking into my ribs... I think it's probably something that you would need to have the fuselage in front of you in order to work it out. Ideally I'd like to have a large step running the full length between my front and rear float rigging. 8^) +++ #3907 From: Kevin Deutscher Subject: Re: Entrance step Have been also wondering about a step and have resolved it down to two approaches. 1. A fold back and retract step that is either spring retracted or cable activated, the leg pivots up and aft ala C-210 main gear. 2. Widen the fuselage to 56 in, enter thru the modified utility door, stroll forward to the cockpit via the central isle similar to a Staggerwing or Stinson. +++ #3911 rom: Bob Romanko Subject: RE: 023 Update & Stuff Could you please describe "aluminum bulkheads under the floor" a bit more? I'm a long way off from there, but I've been looking at the plans since reading this post of yours, and am lacking clues as to what bulkheads would buy you. Lighter? Stronger? Hmmmm.... I read you're posting pics in a couple of weeks (of your usual fantastic craftsmanship, I'm sure!), but if you can give me a little idea of what you're doing with the bulkheads I'd appreciate it. +++ #3922 From: William & Delinda Johnson Subject: 023 Update I demand a recount! (just kidding). Anyway, the reason for the aluminum bulkheads should be approached with CAAAAAUTION. The process is not for the faint of heart. So read what follows only if your belly can handle the situation (smile). The reason . . . just personal preference. Since my bearhawk belly is a little fatter than the plans (muffler), I just wanted to do it that way. Of course, pictures will follow so everyone can decide on their own which method they like best. I would recommend; however, taking a good look at the rudder pedal arms. The pedal movement is excessive, at least in my view. +++ #3930 From: Bob Romanko Subject: RE: 023 Update The mystery's killing me. If you've already welded all that tubing, why stop midstream and build an aluminum bulkhead? Especially with YOUR fantastic welding skills (not to diminish from your perfect ribs). Heck, you're work overall makes me want to take all my ribs to a recycler! Seriously, the only benefit I can see is it gives you an easier way to change the profile to a more curved shape without having to bend 4130 to accomplish the same. Am I getting warm? +++ #3931 From: William & Delinda Johnson Subject: RE: 023 Update your warm . . . pictures next week! +++ #3932 From: Kevin Deutscher Subject: Bill, Throw another steak on the grill. Great minds think alike? There has to be a reason for tampering with perfect engineering. Could it be.... just maybe, although never justified... that a change of this scope and magnitude could beget a belly cargo pod or oversize glove box. Just think, an area with a volume large enough for sleeping bags survival equipment, skis, your favorite over under. Just right at the CG. Just postulating for now, but when my fuselage is welded and I feel that urge to pound on more aluminum my Bearhawk may just develop a beer gut. Have I got the fire hot enough? Still working them wings pounding rivets. +++ #3937 From: Russ Erb Subject: Bill, Throw another steak on the grill. Some time ago I had an idea which I have not looked at the fuselage plans to see how it would work. I would weld on tabs to strategic points on the bottom of the fuselage and drill them to accept bolts. These tabs would be placed in such a location as to be underneath the fabric. Where the fabric covered these areas, I would bond in inspection rings. Why? To attach a belly baggage pod. Possibly even a fuel tank? Initially, other than a pound or so of extra steel, there would be no penalty for this modification. If at some time I decided to actually build such a pod, I would cut out the fabric in the inspection rings for access to the attachment points. The pod would be conformal to the bottom of the fuselage. If the pod was removed, the holes in the fabric would be covered by inspection covers. Kevin, if you wish to develop a beer gut, aluminum is not the way to go. Everyone knows that the Beer Gut (what some around here, including a kit buyer of same, have been known to call the Berkut) is built from composites +++ #3940 From: Bob Romanko Subject: RE: Bill, Throw another steak on the grill. I wonder how much the addition of a belly pod would change the flight characteristics? Not being an aeronautical engineer, that's about as far as I can go with the question (grin)! I guess as long as the frontal width isn't there you'd be safe, both in the drag and negative lift department. If you gave the Bearhawk a beer gut, seems to me it would make the bottom of the fuselage shaped more like an inverted wing. If you want to have a look, go to http://www.flypass.com/pods.html and see what Flypass did for the CH-801. Just when you thought the plane couldn't get any uglier! What they did was make the front narrower to reduce drag and eliminate the sucking effect a full-width belly pod can give. I really like what Erbman is doing here with his aircraft. The guy thinks enough for all of us, so I'm going to just follow his lead with this mod. I'd have to be drain bamaged NOT to do this mod. What a hassle it be to do this AFTER your fabric's on! Thanks, Russ, for the tip...and thank you Bill for getting the ball rolling. Bill, let me guess, you came across an english wheel and hand formed a pod out of a single piece of aluminum?!? You must be rubbing shoulders with Kent White! +++ #3941 From: Ken Beanlands Subject: Re: Bill, Throw another steak on the grill. On the Christavia I have considered the same idea of a baggage pod under the belly. Even one of those Thule carriers common on cars might work well. However, rather than adding dedicated mounts to the fuselage, I plan to tie into the rear LG mount and the rear float fitting. This way there are no extra fittings to weld on. +++ #3943 From: Tim Anderson Subject: Re: Belly pod I have a belly pod for my Kitfox, works great. They have extra set's of mounting tabs (copies of the landing gear mounts) in front and behind the landing gear mounts. These mounts also serve as float mount brackets. The pod is the same width as the fuselage and wraps around the landing gear inner struts. Made from fiberglass and weights next to nothing. metal straps connect to the mounting points. It has a side access door and a front access door. Air drag seemed to be minimal. When I had the plane on ski's I needed extra room for cold weather gear and "ice fishing equipment". With the ample room available in the bearhawk, the need may not as great but it wouldn't hurt to add the mounting tabs. A pod really comes in handy for light weight stuff that takes up a lot of room (sleeping bags, tents, camping chairs, etc). I did have to cut a hole in the top of the pod to get to the gascolator drain. +++ #3967 From: budd davisson Subject: Re: Fuselage Questions About fuselage Width. there is never enough width, but we've got C-172 width plus about an inch. Widening it out isn't a major deal, but it does mean a lot of your plan measurments don't work any more. Since the width problem is only at your shoulders and butt, why not just bulge the doors, as we mentioned earlier. That can't even be measured, drag wise, but widening the entire airplane can. Also, bulged doors give better downward visibility. +++ #3971 From: BRUCE A. FRANK Subject: Re: Starting on Fuselage The V-6 STOL design overcame just such problems. We start with a salvaged TriPacer fuselage and install the Ford 3.8L V-6 up front. When Dave Blanton came up with the original plans he called for a 24" extension of the fuselage. As it turned out the Ford engine, even though it was heavier, its cg was closer to the firewall. Since that time V-6 STOLs have been build with no lengthening of the fuselage. The only changes made, to handle any cg concerns, has been to move the battery to the bay behind the luggage area. In such a high lift, high load capacity design like the Bearhawk, 20 pounds of battery cable, to me, is a reasonable trade off to allow the use of the higher horse power 0-540. (or an auto-engine) +++ #3989 From: DANFORD, GARY Subject: RE: Starting on Fuselage I was interested in your weight and balance problem with the larger engine. I had the same concerns when I built my Hatz. I put the battery behind the back seat and it worked out ok. However during construction I mentioned to my mentor my concerns over weight and balance and he reminded me that that's why god made bricks. So I made the back 18 inches of the bottom fuselage cover out of alum to allow access to the control cables. I also made a bracket (two tabs actually) for the brick. Easier to add it during construction that after weight and balance and its easier to add a brick than move a battery further back. My D Model C182 had the long cables and always had starting problems. To save weight Cessna used the alum fuselage for the ground cable and used alum battery cables. I replaced the alum cables with copper and that helped but never solved the problem. Anyway, I never added the brick but there was a place for it if I needed it. I thought adding four or five lb! s. that far back might solve the problem if it came up. On another topic, I don't like loose thing behind me when I'm flying. If you've ever seen my aerobatic landings you'd understand, loose things sometimes fly forward. I would suggest some simple tie down's on the luggage floor would help keep that always handy Alaskan snow shovel back there. +++ #4302 From: budd davisson Subject: Re: [Bearhawk] Re: welding position Rotesseries, etc: I usually make up a Dutchman clamp that clamps on to the rudder post inside the fuselage that has a piece of 1" heavy wall tubing attached to it. I drill a hole in a wall stud and put a saw horse at the other end. That way I can rotate it by myself without have to have a big rotary thang to pivot it on. +++ #4335 From: Jim Ash Subject: Re: [Bearhawk] Re: kit welding Are the tube joints drilled for oil, or doesn't anybody do that any more? And have you got a favorite paint/epoxy for the fuselages? +++ #4337 From: budd davisson Subject: Re: [Bearhawk] Re: kit welding > Are the tube joints drilled for oil, or doesn't anybody do that any more? We haven't decided yet, but most production airplanes only oil the longerons and we'll probably do the same. +++ #4389 From: Shelly Subject: Re: [Bearhawk] Re: welding position > I made a very inexpensive "rotisserie" when covering my > kitfox...just would have to be enlarged slightly. Bolt two > 2X4's in each direction... Tim, you may also be interested in a dolly that Fred and I built for easy manipulation without the bulky landing gear in place. It will be published in "Experimenter" in the next month or two +++ #4432 From: Ken Beanlands Subject: Re: [Bearhawk] Digest Number 266 Well, I'm glad to see that I'm not the only one who did not drill all those little holes in the frame. I used the exact mentality that you did, Corky, although I may eventually oil the longerons. Most of the older birds I've seen only have problems in the lower longerons and then, only when there has been a lot of water hung up inthe rear of the fuselage or when the plane has been used in salt water (floats). Considering that many of these planes didn't even use 4130, that's pretty good. +++ #5270 From: Corky Scott charles.k.scott@d... Subject: Re: [Bearhawk] Digest Number 337 Dillsburg in Dillsburg PA usually has the best prices in tubing. They keep a HUGE stock and are generally the supplier for all the other companies supplying materials. As to the tubing notcher, you can have mine if you want. I found it less than useful. I ended up using a shaped rough grit grinding wheel and it worked fine. Remember, you aren't gluing the tubes together, you are welding them. You don't need a perfect fit to have an aircraft grade weld. Rough cutting with the grinding wheel then light touches with a large round file are all you need. In regards making a jig to weld the fuselage, I built the entire Christavia Mk4 fuselage without anything more than lines drawn on the floor of the shop. No matter how careful you are with a jig, you will still end up with an imperfect fuselage because of the amount of heat necessary for welding each joint. It doesn't matter. All you need to do is get it close because it's the stringers everyone sees, including the slipstream. Piper found this out years ago when they discovered that they were wasting their time trying to make their tube fuselages identical. In the air it just didn't matter, they all flew in a very similar manner. If you go to a welding supply store and tell them you are welding 4130, they will supply you with the proper rod. I think it's an E70-4, or you can use a -6. Some people rub off the copper coating, others use it as it comes. It doesn't seem to matter all that much. In the end, the process of welding the joints ends up being so strong intrinsically, that even if you screw up the welding, it probably won't matter all that much. No less a luminary than Tony Bingellis is suggesting in print that none seamless tubing and several of the brazing rods should easily be sufficient strengthwise to suffice. What he meant in this statement is that when you weld a simple or complicated joint, you end up putting a fillet all the way around the joint, every joint and every tube. Even if you miss a spot, it's just one joint in many, all of which support each other. Once the fuselage is finished, it's so well triangulated and so strong that kludging one or two joints simply won't matter. Perfection is a great concept to strive for but when it adds hours and years to a project.... Unless you intend to vie for the top spot at Oshkosh, why put yourself through such agony. I'm not advocating bad work. I've done many a part again because my first efforts simply weren't good enough. What I am saying is that once you start building, you'll find that it's a lot more simple than you thought. +++ #5275 From: "William & Delinda Johnson" Subject: RE: [Bearhawk] Plans, parts lists, construction tips, etc. > How are the plans, well drawn and documented, easy to read? Are > there any material lists for each phase, particularly the > tubing? I hear there's a newsletter for this that I can > subscribe to, who do I see about that? The plans are outstanding. Early builders found some errors, but you should have no problem. With all the pictures, Russ CD (and now he has a digital camera!), and this group, your in great shape. > I've poked around on the web and I saw the fuselage on the > Johnson's website. Looks great, but that must have been a real > bitch to get everything so perfectly aligned for welding. No, it was actually easy. Forget about tubing notchers. A chop saw, grinder with curved wheel, and belt sander with sanding disk is all you need for power tools (on the basic fuselage). A metal cutting band saw, mill/drill and lathe would make your job easier when you get to the plate steel parts. If I could have only one power tool, I would take a lathe. Now before everyone starts talking about cost, I have a 1927 southbend purchase for $100 - yes the one in the pictures. Next would be the mill drill. With those tools, I could make all the other tools for little cost . . . +++ #5421 From: Rod Smith rsmith@a... Subject: Tube fitting I've read pros and cons on using a joint jigger or variant for fitting tubing. I had decided not to buy one and when I told a friend I was starting my fuselage he said I should try his out. He made his (he's a professional machinist). It will cut up to a 28deg angle. I have heard they dont do well at sharp angles but this one does. I now have the lower and upper fuselage ladders tacked and one badly abused 3/4" hole saw ready for retirement. I used it mounted in my drill press, applied gentile pressure and lots of cutting oil. I believe it saved me countless hours of fitting. I measured the angles with a protractor off of the layout table, set them on the notcher and had at it, perfect fit everytime. The tubing comes out of the notcher with wicked edges so I immeadiatly knock the worst off with a file or die grinder so someone (me)doesn't get cut. My wife and daughter flew to Seattle for a 3 day weekend leaving me home alone with de plane. I managed to log 40 hours on the project while they were gone, wondering where I can send them next. +++ #5442 From: Jim Ash Subject: Tubing joint cutters All the joint jiggers I've seen use hole saws and leave this nasty ragged edge like Rod talks about. Is there a reason people don't use end mills instead? +++ #5450 From: Larry "lbhensley" Subject: Re: [Bearhawk] Tubing joint cutters Just a word about hole saws vs. end mills. I don't use either. Instead I use Rotobores. These are fairly expensive but I've had most of mine for about 15 years. These are also called rotary broaches. I even use them to cut and fit all of the exhaust systems I make. This is 321 stainless steel with .035 wall. Works great. +++ #5452 From: Jim Dewberry dewcraft1@a... Subject: Rotobores Source? I read with real interest of your use of rotobores to cut tubing. I have a huge 4000 page MSC catalog but don't see rotobores listed in the index. Where do you get those things? +++ #5454 From: Larry "lbhensley" Subject: Re: [Bearhawk] Rotobores Source? I'll look up the vendor where I bought the broaches and let you know. These all have .750 shank with a live pilot that lets you just center punch and go to cutting. The center just retracts as the cutter is fed. The quality of the cut is exactly as if done by and end mill but doesn't cut all of the center out. (Just like a hole saw!!!) imagine that. If you have any more questions, just drop me a note. +++ #6101 From: pfflyerz@c... Subject: fuselage tubing For those of you looking over the the tubing required, I would recommend that you add 10 to 12 feet of 1/2 X .035 4130 SQUARE tubing. I had been experimenting with making the wing contours that go above the upper longerons with the 1/2 inch channels as per plans, without much success. I noticed in Mike's fuselage photos that Proto 2 used what looked like square tubing for the uprights that support the contours. I bought enough to try making the wing contours, as well as for the uprights. The contours came out very nicely with this material. They bent easily and provided four sides to weld the uprights to. 10 feet would be enough to do all you need to do, but 12 feet gives you a little extra leverage for bending. Pat Fagan #232 Pearblossom CA +++ #6105 From: Russ and Penny Erb Subject: RE: fuselage tubing I thought we heard once that Bob formed the channel to shape by cutting selected notches and rewelding after bending. Russ Erb +++ #6110 From: Budd Davisson Subject: Re: fuselage tubing A note about channel stock: -buy 1 x .50 stock and cut it in half lengthwise. Done it many times. -The stuff on the top doesn't have to be 4130. You can buy 1/2" square 1018/1020 from your local steel yard and cut one side off . It's used in fancy fences and security grates for windows. -bending: don't be afraid to make a mold of the curve from plywood with 2" holes cut in it to accept C-clamps. Either pull it in to shape and "relax" it with a torch, or notch it and reweld it. Yes, the plywood burns like crazy, but you don't care. Just blow it out. Don't do this in the living room. bd +++ #6543 From: "Mike Carriere" Subject: Re: Direct Comparison V-6 STOL to Bearhawk > My mods exceed those in Blanton's builders manual and > incorporate some of the observed features for the BH, along > with my ideas. I have added (above any beyond the V-6 STOL > prints)pilot side door, top hinged doors, widened fuselage at > the shoulders (47"), full skylight, full Plexiglass door > coverings, ceiling to hip side windows in the rear seat area, > large cargo door, ten feet of Fowler flaps on each wing, > Larger rudder, and wider main gear track with a > modified-to-lock Maule Tundra tailwheel. My intent is to > remain with the 3.8L V-6 Ford engine (I have three of them, > two modified for flight). We have planned the same type of door. How are you dealing with the interference with strut? We recently built an aluminum lexan door (gas operated for our super cub and its wonderful. We would like to bow the BH door outward (Bubble Doors) but haven't figured the strut problem out. Mike Carriere #463 #469 +++ #6616 Date: Fri, 22 Jun 2001 19:59:10 -0700 From: "Bruce A. Frank" bafrank@ Subject: Re: Direct Comparison V-6 STOL to Bearhawk Are you sure that the swing up door will actually hit the lift strut? Some plane I saw, I think at Sun 'N Fun, had swing up doors that did hit the strut. What they did was to make a small spring loaded door at the edge of the main door with a small pad of soft rubber on its bottom edge. When the main door was opened upward the edge of the small mouse hole door contacted the strut and folded downward. The strut-clearance door was just large enough to accommodate the strut. Seems this was a modification of a production plane. Now I am going to have to simulate my strut(s) location to see that mine clear (fabric wing so I have to clear two) Bruce A. Frank +++ #6617 Date: Sat, 23 Jun 2001 03:41:01 -0000 From: rsmith@ Subject: Re: Door Clearance I also plan on a one piece swing up door. I took measurements at Sun&Fun, the bottom of the door will need a cutout 1" high and as wide as the strut to clear. Rod Smith #246 +++ #6618 Date: Sat, 23 Jun 2001 21:14:24 -0000 From: jrm_nh@ Subject: Re: Door Clearance How about raising the door sill up an inch, make the door one piece. Would the door need any cutouts then? You know the bh really needs a step anyway, another inch up shouldn't hurt... Jim M # 503 +++ #6619 Date: Sat, 23 Jun 2001 17:38:56 -0700 From: "Bruce A. Frank" bafrank@ Subject: Re: Re: Door Clearance You mean shorten the door an inch? I'd thought about suggesting that, but some people seem highly resistant to any changes in the BH. +++ #6620 Date: Sun, 24 Jun 2001 01:56:01 -0000 From: jrm_nh@ Subject: Re: Door Clearance Well it's not like I would be adding a nosewheel. Small changes should be OK. I will be adding 2" to the width, shortening the door shouldn't be a problem. A one piece door would have an advantage for a floatplane. Jim M # 503 +++ #6624 Date: Sun, 24 Jun 2001 04:03:53 -0000 From: rsmith@ Subject: Re: Door Clearance Yes that would work. Instead of changing the geometry of all the tubing involved (see plans #16 & #18) I would add a channel piece 1" above and parallel to the T11 tube. I will do that or notch the door and weld a corresponding piece of .040 sheet to the T11 tube for the door to seal against. Rod +++ #6730 Date: Mon, 2 Jul 2001 22:22:16 -0700 From: Russ and Penny Erb erbman@ Subject: Erbman's possibly useful trivia... Something that always bugs me is when learning a new skill is when I'm told I'll need something, say a left-handed smoke shifter, that I've never heard of or seen, but no clue is given on where or how to get one. Therefore, in the spirit of education... In Kent White's excellent video on 4130 steel welding (you do have one, don't you?), there is a discussion of using valve lapping compound on parts where a tube slides around a tube. Not being a serious motorhead, I had never seen such a product. I boldly walked into the local auto parts store and asked for such. He handed me a tube of "valve grinding compound" of the Permatex brand. It was over with the form-a-gasket products (RTV), and looked very similar in packaging. If you know where the RTV is in your local auto parts store, you've got a fighting chance at finding the valve grinding compound. In a totally unrelated development, I finally found the MDF (medium density fiberboard) at the local Home Despot while looking for something to build the table jig for the tail sections. I've heard of the stuff before, but had never seen it. I may write about my impressions of using it in the future. Russ Erb +++ #7026 Date: Tue, 31 Jul 2001 22:25:52 -0700 From: Russ and Penny Erb erbman@ Subject: Table of tubing sizes posted I just posted in the files section the file "t numbers.xls" This is an Excel spreadsheet of the table of T-numbers and tubing sizes from the fuselage sheet of the plans. Yea, it's not much, but the point is that I did it and you can download it faster than you could type it. Print a copy and post it on your workshop wall. It will make reading the plans a lot simpler. Erbman +++ #7389 Date: Sat, 25 Aug 2001 08:13:04 -0700 From: Russ and Penny Erb erbman@ Subject: FW: BH doors > I also wanted to tell the BH group that in working withthe > fuselages we looked at the doors and decided it would be MUCH > easier to make them work, if they were made of square stock, > which is unbelievably expensive. Also, you can't do the entire > door in square because the bottom of the front one has a funny > bend in it. So I taked to Bob about it and he agreed with me > that we could do the doors in square MILD STEEL, which is less > than 50 cents a foot and use a round piece at the bottom where > it needs the bend. The square stock makes it easier to make > trim pieces to mount the glass, is cheaper and makes mounting > upholstery panels and the exterior aluminum easier. Vogelson > has 1/2 square in .049 that'll do the trick. (budd's been fighting the Yahoo demon trying to get reconnected with us. He thinks he's got it now, which we'll know if he gets this message. Speaking of steel--On Tuesday I took delivery of my fuselage steel from Dillsburg. Only 275 lbs worth. The package was something like 25 feet long but only about 1 foot in diameter. Erbman +++ #7392 Date: Sat, 25 Aug 2001 12:30:48 EDT From: BruceAFrank@ Subject: Re: FW: BH doors I have been through some of this same process in building doors for my V-6 STOL. The original door on this salvaged Piper fuselage was badly rusted and my desire to create more shoulder room by bulging the door(s) slightly meant building from scratch. My intent was doors covered with Plexiglas top to bottom and hinged at the top as done in seaplane conversions. Since the door is not structural whether mild steel or 4130 is important from the durability of the door only. My first attempt was with 1" .035" wall square 4130. This produced a massive looking and relatively heavy structure that I relegated to the salvageable materials pile. The next try was with mild 1/2" .049" wall square tubing. This tube is relatively flexible requiring bracing at corners and particularly across the curve at the trailing edge of the structure. After building my mild steel doors then testing them in the open position (up against the wing as one might fly with the doors open) I concluded that they were too flexible for my application. I duplicated them in 4130 and was rewarded with doors that did not flex from the expected wind loads in the open position. The perimeter of the door(s) is drilled for 10-32 stainless Nutserts set every 3" to fasten on the Plexiglas with the same treatment at the top to attach the hinge. Bruce A. Frank +++ #7396 Date: Sat, 25 Aug 2001 12:43:11 -0700 From: Russ and Penny Erb erbman@ Subject: Truck Shipments from Dillsburg As I alluded to in a previous message, I received my fuselage steel order last Tuesday. While a lot of people (budd primarily) have sung the praises of ordering from Dillsburg, there were a lot of questions I had that went unanswered. Here's my attempt to answer them based on my experience. First, how to place a large order. I didn't relish reading off 40 different line items on the phone. I wanted to send something in writing. Charlie Vogelsong apparently isn't interested in doing e-mail, so I could have snail-mailed the list. Instead, I faxed the list to him. This worked fine, with only a minor glitch. The fax machine is connected to the same phone as the voice line, so if you're going to send a fax during normal business hours, you should probably call Charlie and warn him. That way you avoid the embarrassment of having him answer the phone but your fax machine just squeals in his ear. Also, if you send a fax, it is a good idea to call back afterwards to see if he has any questions. For instance, the streamline tubing specified for the landing gear is currently unavailable. He told me that he had the same dimensions in a thicker wall, and asked if that was a suitable substitute. Most of my questions had to do with this concept of "truck" shipment. I had never had anything shipped by means other than UPS/USPS/Airborne/Fed Ex etc. The problem with that is that all of those folks are rather picky about shipments over 8 feet long, as in they don't accept them. This is a problem when you need longerons that are 17 feet long and don't take well to cutting and splicing. Since I live close (2 hr drive) to Aircraft Spruce, I had thought about picking up the steel there and driving it back on a roof rack on my full-sized van. While that would have worked, after doing the math, Spruce had enough markup that this route would have cost me more than ordering from Dillsburg. This was the same conclusion that Pat Fagan came to a while back. Strangely enough, by the Dillsburg price sheet I had, I could get the 4130 sheets/plates for less from Aircraft Spruce, so that's what I did. Dillsburg will accept your credit card for payment, including pre-payment of the truck shipping. The cost of the truck shipping for my load was $154.00. Somehow I qualified for a 60% discount on the $281.99 standard rate. The other question I had was how does the stuff get delivered to me? I had visions of a cranky truck driver who had just driven straight through from Pennsylvania to California pulling up in front of the house, banging on the door saying "Get this stuff off of my truck, I've got a schedule to keep". Of course, I wouldn't be at home at the time, so it would stay on the truck winding its way around the country until I could finally catch up with it years later. In reality, the answer made a lot more sense. It seems the stuff is driven first to a warehouse somewhere. Then the local contractor for the trucking company calls and sets up an appointment to put the stuff on another truck and then drive it to you. Now, how do you get it off the truck? Quite by accident, I happened to be at the house when the truck arrived. It was a good thing, because the driver and I were able to muscle the load off of the truck and into the front yard. From there I opened the packaging and moved the tubes a few at a time to a better storage location. If you have any other questions about this procurement system, throw them out and I or someone else will try to answer them. Russ Erb +++ #7405 Date: Sun, 26 Aug 2001 12:10:06 EDT From: pfflyerz@ Subject: Re: Truck Shipments from Dillsburg One other thing to add about truck shipments, as I have had three done, most recently my engine, and no one would deliver to my home do to the dirt road and lack of turn-around room. The first time I arranged to meet the truck at the local airport, the second time we met at my work, and the last time I simply drove to the warehouse and picked the shipment up. Pat Fagan #232 Pearblossom, CA +++ #7422 Date: Mon, 27 Aug 2001 08:36:18 -0400 From: lisankejm@ Subject: RE: Truck Shipments > ...and the last time I simply drove to the warehouse and > picked the shipment up. This saved me about $70 on my aluminum order from Wicks. I was given the option of having it delivered to my door or picking it up at the depot. Pick up at the depot was $35 for shipping and I only had to drive 40 miles one way to get it, so it was the better of the two. Joe Lisanke +++ #7428 Date: 27 Aug 2001 09:47:50 EDT From: charles.k.scott@ Subject: Re: Digest Number 527 > The square stock makes it easier to make trim pieces to mount > the glass, is cheaper and makes mounting upholstery panels and > the exterior aluminum easier. Vogelson has 1/2 square in .049 > that'll do the trick. This is precisely the reason I used square stock to frame the door opening for the Christavia. Should have used it for the windor openings too. Corky Scott +++ #7429 Date: Mon, 27 Aug 2001 06:52:11 -0700 From: Budd Davisson buddairbum@ Subject: Re: Door frames, fuselage, etc. Re: doors Although we're still jigging for the doors, it appears the top/front doors can be all square while the bottom/front need to use a piece of round for the bottom piece and square for the other three sides to take care of the compound bend at the bottom. We haven't looked at the back doors, but they look as if they can be all square. A comment on the fuselage: Now that we're jigged and building the fuselages, I spent most of last week looking at it closely and have one comment to offer: my hat's off to anyone who scratch builds it. It is probably the most complex tubing structure I've ever looked at. I've never seen longerons with so many bends (not intentionally anyway) or so many odd-ball tubing patterns. Much of it is to maximize interior room without making the fuselage too big or to accomodate putting things like the windshield in a better place. Most designers would have said to hell with it and run it straight from the rear spar fittings back as well as ignoring the resulting crowded backseat head room. Not The Bob. This one of many reasons the airplane works so well. Even in a hard-jig like ours (see the photos in Airbum, it works now), however, it's still a challenge. bd +++ #7466 Date: Tue, 28 Aug 2001 15:18:19 -0400 From: "Mike Carriere" mcarrier@ Subject: Re: FW: BH doors > My intent was doors covered with Plexiglas top to bottom and > hinged at the top as done in seaplane conversions. Since the > door is not structural whether mild steel or 4130 is important > from the durability of the door only> We have built and installed in our Supercub a gas operated top hinged door covered with tinted Lexan. The construction is 3/4" aluminun square stock with home made .032 angle around the perimeter to hold the Lexan. My wife opens the door in flight and it is realy stout yet light. A central lever pushes two polyethylene door latches that draws the door in as it locks. Really neat and the only change we will make for the BH is we are going to bubble the two doors outward 4 inches and allow a bottom slot for any strut interference. If there is interest we can put some pictures to this post but I don't know how to get that technical. Mike C #463- 469 +++ #7467 Date: Tue, 28 Aug 2001 16:21:43 EDT From: BruceAFrank@ Subject: Re: FW: BH doors I like that idea. 3/4" sq. aluminum never crossed my mind. Sometimes I'd get intimidated by the rest of the builders in the Ghetto hangar at New Garden. First was the comments about the "massiveness" of the 1" steel and then the "excessive flexibility" of the 1/2" mild steel. The larger dimension of the 3/4" aluminum is exactly what was needed to provide the primary component of the required stiffness. The idea strikes me so well that I am going to scrap my steel frames and start over with aluminum. My forehead is beginning to develop a flat spot. While I am at it, I am going to replace my sheet metal door sill and other perimeter framing with aluminum. My doors have sheet metal around them similar to what is done on the TriPacer, but screwed on rather than welded. And all that steel is heavy. It is good we had this talk. Yes, I would like to see some pictures!! Bruce A. Frank +++ #7472 Date: Wed, 29 Aug 2001 11:51:18 -0400 From: "Mike Carriere" mcarrier@ Subject: Re: FW: BH doors > Yes, I would like to see some pictures!! Bruce: This is my first try at sending photos so if it doesn't work I'll get one of our many young people here to do it. The plane is a supercub certified as experimental, The door seals so well that we have not added a rubber seal. Trick to building the door was to tack weld it in place. Mike Carriere #463- #469 Yea we're building two so far! [ See yahoogroups web site for pictures. BJH ] +++ #7473 Date: Wed, 29 Aug 2001 09:38:24 -0700 From: Budd Davisson buddairbum@ Subject: Re: FW: Door extrusion Your doors look great. It's hard to tell from the pictures but the frame extrusion looks like a commercially available door or window extrusion. Is it? bd +++ #7492 Date: Thu, 30 Aug 2001 12:57:10 -0000 From: t18cox@ Subject: Dillsburg, wings Charlie really runs a tight ship. My tubing was delivered yesterday, a week after it was ordered. ABF motor freight brought it out and the driver helped me drag it 100 feet from the street to the garage. There is about a days worth of work left before the second wing goes into storage, then on to the fuselage for a while. I used Bob's method of Loctite 609 for aligning and securing the rodends in the flap and aileron mounts. It really works well. With the first wing I was a little sloppy with the Loctite and found it will strip Stits Epoxy if runs are not promply wiped up. I was careful to lightly coat the rodends and insert them on the second wing and had no problems. When I started on #303 I decided against keeping a log of work hours. I have done so on every project before and reasoned this is just for fun. After seeing actual times and estimates I decided to keep a record on the second wing assembly. All jigs and tooling had been built during the assembly of the first wing. All parts except the skins were complete when the assembly and timekeeping started. This morning I am at 272 hours with 6 to 8 hours to complete and store. Bill Cox #303 +++ #7493 Date: Thu, 30 Aug 2001 09:13:45 -0700 From: hkeil@ Subject: New Southco hinge design Anyone interested in concealed hinges for their doors, take look here. Especially the "Door Stay" movie. Seems rather clever and if they are too expensive, they look like the could be copied with a reasonable expenditure of time. http://www.southco.com/html/new_concealed_hinges.html Herman Keil +++ #7494 Date: Thu, 30 Aug 2001 12:18:27 -0400 From: "Mike Carriere" mcarrier@ Subject: Re: FW: Door extrusion > Your doors look great. It's hard to tell from the pictures but > the frame extrusion looks like a commercially available door > or window extrusion. Is it? Bud and Bruce: The door sill/frame is .032 broke to form a U channel and then custom fitted to the opening; Tig weld tacked then removed and welded. Final installation with #6 csk SS screws into tubing( only 4 screws required). The frame is 3/4" square stock (sharpe angle) fitted in the installed sill/frame with 1/8 spacers for clearance. The lexan is held in by the fabricated .032 aluminum 3inch angle tig weld and polished. We used a 6" adjustable gas shock tube attached to the steel tubing frame. As mentioned you can open the door in flight and its quiet. The only change I would make is to bubble it out for the BH. Mike Carriere #463-469 +++ #7495 Date: Thu, 30 Aug 2001 12:29:35 -0500 From: "Tony Chisum" tonychisum@ Subject: Re: New Southco hinge design Those hinges are cool. I suppose they are made in different sizes. +++ #7496 Date: Thu, 30 Aug 2001 22:15:01 EDT From: BruceAFrank@ Subject: Re: FW: Door extrusion This is great info! Did you say, did I miss it, what is the wall thickness of the 3/4" aluminum tubing? Bruce A. Frank +++ #7497 Date: Fri, 31 Aug 2001 09:10:28 -0400 From: "Mike Carriere" mcarrier@ Subject: Re: FW: Door extrusion Bruce: The square stock is just a commercial grade of aluminum and wall thickness appears to be in the .025 range or slightly larger. I can get the calibers in to measure. You can buy it anywhere. +++ #7502 Date: Fri, 31 Aug 2001 19:29:50 -0000 From: zipppydoggg@ Subject: Re: FW: BH doors Just curious, I don't see an outside handle on the door. Is there one? I would think that an outside handle is needed to secure the door after leaving the cock-pit, not to mention Emergency Rescue. Rob "my mind often runs without my permission, or direction" Gaddy +++ #7504 Date: Fri, 31 Aug 2001 16:43:28 -0400 From: "Mike Carriere" mcarrier@ Subject: Re: Re: FW: BH doors Rob; No there isn't an outside handle. The pressure from the gas strut holds the door closed fairly firmly but not locked. It would be very easy to install a flush triger lock -same as the ones on the bagage compartment door if security is required. As for opening; no handle is required and my wife hasn't broken a nail yet. Mike Carriere #463-469 +++ #7516 Date: Sat, 1 Sep 2001 22:03:16 -0700 From: Russ and Penny Erb erbman@ Subject: Fuselage finish welding Sorry I can't give you an off-topic subject, so how about one that's on-topic? I just bought the materials to build the special purpose fuselage building table (driven by my ridiculously small work area), so this question will be an issue in a few weeks. We're going to get in the DeLorean, push it up to 88 mph (76.5 knots), and jump forward in time to when I have finished tack welding the top side, the bottom side, and have tack welded in all of the structural tubes shown on drawings 16-18. Question: is this the appropriate time to finish weld the clusters, or should I do it after attaching the various fittings and bazillion attachment tabs? I think I know the answer, but I'm interested in hearing some other opinions. During the finish welding of the fuselage, managing distortion is a big issue. Two things I've heard on this issue: 1) Start at the tail and work toward the front (on the idea the tail welds are less critical so the practice will do you good), and 2) Weld all of the clusters at one fuselage station before moving on to the next station. I've also seen the technique when welding a simple tee to do it in four parts, each time going 1/4 of the way around. If it was a clock face, it would be like welding from 12 to 3 o'clock, then 6 to 9, then 3 to 6, then 9 to 12. Supposedly this keeps things evened out. Next question: When welding around one fuselage station, should I do one whole cluster, then the next, or should I do part of one cluster, then part of the opposite cluster, and keep jumping around? Or does it really matter? I know several of you out there have done this before, so I expect to hear about your methods. Russ Erb +++ #7518 Date: Sat, 01 Sep 2001 22:28:37 -0700 From: "Bruce A. Frank" bafrank@ Subject: BH doors Now that I have gotten home and can look at Mike's pictures more clearly I am even more impressed. One of the differences that caused some problems with my original mild steel door structures is that my doors are not flat as the Cub doors are. My doors have a bend in the center so the bottom leading edge will catch a lot more wind pressure when open than the flat Cub doors. I think the 3/4 sq. aluminum much more rigid with more room to fasten in the glass than my method. Again, I want to say I am glad we had this conversation because this is a better idea. But, it also means I have to re-do these parts again!! Bruce A. Frank +++ #7519 Date: Sun, 02 Sep 2001 06:44:08 -0700 From: Budd Davisson buddairbum@ Subject: Re: Fuselage finish welding I'm certain you're going to get a lot of input on this, as everyone has their own, but this its 0600 on Sunday morning and no one else has answered yet, so I'll toss in my opinions. These are all good questions that everyone will profit from. bd > Question: is this the appropriate time to finish weld the > clusters, or should I do it after attaching the various > fittings and bazillion attachment tabs? I think I know the > answer, but I'm interested in hearing some other opinions. Don't weld any clusters until the top and bottoms are tacked into the complete fuselage or they'll move around too much. > During the finish welding of the fuselage, managing distortion > is a big issue. Two things I've heard on this issue: 1) Start > at the tail and work toward the front (on the idea the tail > welds are less critical so the practice will do you good), and > 2) Weld all of the clusters at one fuselage station before > moving on to the next station. You'll be amazed how much better your welding is by the time you get to the front, where the really heavy/hard joints are. However, even though starting at the back, I'd only do the easily accessable parts of the big cluster at the bottom of the tail post because getting inside of it can be really tough. Also, by starting at the rear, you'll start to appreciate how much more heat is required on the real thing than on practice pieces. the tubing sizes are small but you'll still be using a 01 and 02 tip. Another reason to start at the tail is that the overall effect of the contraction/expansion is less and by the time you get further up, the back will be rigid. You absolutely will not believe how much the rudder post will move back and forth, so keep track of the movement as you weld each station and adjust it accordingly. Weld each station, but don't progress around it in a circle. Progress diagonally: Bottom left, upper right, upper left, lower right, etc. > I've also seen the technique when welding a simple tee to do > it in four parts, each time going 1/4 of the way around. If > it was a clock face, it would be like welding from 12 to 3 > o'clock, then 6 to 9, then 3 to 6, then 9 to 12. Supposedly > this keeps things evened out. I can see where this would help, but a simple Tee progresses so quickly that the heat on once side hasn't had enough time to even cool before the other side is done. What is more important, when you finish a cluster, keep the joint hot and move the torch to the outside of the longeron and heat about a two-three inch section red hot so it is forced to contract right along with the inside where the cluster is. This is especially important when welding tabs and stuff in place. Since just about every station has a bend in the longeron anyway, the normal longeron bows caused by contraction won't be noticeable. It's more important you keep it balanced from side to side to keep the tail post where it's supposed to be. > Next question: When welding around one fuselage station, > should I do one whole cluster, then the next, or should I do > part of one cluster, then part of the opposite cluster, and > keep jumping around? Or does it really matter? Personal opinion here: Once you get a cluster hot, keep it hot and progress all the way through it. Otherwise, coming back to start it again takes a lot more heat and is really aggravating. Basic rule of cluster welding: the heat required will increase sharply, so, when the weld isn't progressing as you'd like and you're at the upper ranges of that tip, immediately change to a bigger tip and do it quickly enough that you don't lose much heat out of the cluster. I'm certain you'll get some ideas that contradict what I've said here, but this is the way I've always done things. Doesn't make it right though. bd +++ #7521 Date: Sun, 2 Sep 2001 08:29:56 -0700 From: Russ and Penny Erb erbman@ Subject: RE: Fuselage finish welding > Don't weld any clusters until the top and bottoms are tacked > into the complete fuselage or they'll move around too much. I knew budd would have good input on this subject. For a little clarification on this one, I think budd is saying what I thought I was saying. Let's try it again. The procedure would be: 1. Tack weld top together 2. Tack weld bottom together 3. Jig up top and bottom and tack weld in vertical pieces and side diagonals 4. With all of the primary pieces in place (i.e. from a distance it looks like a finished fuselage), NOW start finish welding clusters Does that match with what you were saying, budd? Russ Erb +++ #7522 Date: Sun, 02 Sep 2001 11:48:20 -0400 From: Mike mike2799@ Subject: Re: Fuselage finish welding You also want to finish welding all tubing before you start to attach fittings. Once the fuselage is finish welded it is very rigid and you can line up the fittings, tack them in place and not worry too much about how they might line up after you weld them in. A few other reasons to do it this way: 1. Easy to get to the clusters for welding. 2. Easy to inspect afterwards to look for pin holes (and you will have pin holes - have a friend look over your fuselage to find them) 3. Part (if not all) of the jigging process involves strapping the fuselage to the table to keep it over the center line on the table. Tacks would break. 4. It is the way that Bob does it. later - Mike +++ #7523 Date: Sun, 2 Sep 2001 09:31:51 -0700 From: "Kent White" kent@ Subject: RE: Fuselage finish welding > ..."I've also seen the technique when welding a simple tee to > do it in four parts, each time going 1/4 of the way around. > If it was a clock face, it would be like welding from 12 to 3 > o'clock, then 6 to 9, then 3 to 6, then 9 to 12. Supposedly > this keeps things evened out....." This is the method called "quarter-welding". Widely used by Beech and others to balance the stresses in a welded joint. Very effective. The most finicky welder I have known starts at the tail, and moves forward one cluster/station at a time, but rotating 270deg clockwise. Reaching the front, he starts over at the tail (270deg clockwise from the first weld) and repeats, until structure is fully welded. Kent White +++ #7524 Date: Sun, 02 Sep 2001 15:34:21 -0700 From: Budd Davisson buddairbum@ Subject: Re: Fuselage finish welding I like the spiral welding technique Kent describes ALOT. Makes huge sense. The only draw back for the homebuilder is that it assumes a well developed welding skill because you get up to the front much quicker and don't have the skill-building time doing it by-station from the rear. It should do a much better jb of keeping the tail where it's supposed to be. bd +++ #7525 Date: Sun, 02 Sep 2001 20:14:44 -0500 From: Tim Hickey tjhickey@ Subject: RE: Fuselage finish welding. (A question) >The most finicky welder I have known starts at the tail, and >moves forward one cluster/station at a time, but rotating >270deg clockwise. Reaching the front, he starts over at the >tail (270deg clockwise from the first weld) and repeats, until >structure is fully welded. Not wanting to be a smart a**, but just couldn't stop myself from asking, how is rotating 270 degrees clockwise from cluster to cluster in a forward progression any different from rotating 90 degrees clockwise in the same direction? (Seems to me that 270 degrees clockwise is about the same as 90 degrees CCW, but I don't see how CW or CCW makes much difference. The whole idea seems to be to work your way forward and around at the same time to balance the weld distortion.) By the way, I heard a story years ago about a welder who would be used to repair damaged steel tube fuselages. He would weld in replacement tubes as required, and then if things weren't straight enough to suit him he would get two 8 foot 2 x 4's and go to work twisting thing back into shape. Tim Hickey +++ #7526 Date: Sun, 2 Sep 2001 18:25:34 -0700 From: Russ and Penny Erb erbman@ Subject: RE: Fuselage finish welding So, budd, would you recommend it for someone like me who's welding experience is basically limited to building this airplane, or should I stick with station by station? If I have trouble rotating 270 degrees clockwise, is it okay to rotate 90 degrees counter clockwise (or even anti clockwise)? Russ Erb +++ #7527 Date: Sun, 02 Sep 2001 19:46:49 -0700 From: Budd Davisson buddairbum@ Subject: Re: Fuselage finish welding > So, budd, would you recommend it for someone like me who's > welding experience is basically limited to building this > airplane, or should I stick with station by station? Do the station by station thing. The rear clusters can be challenging, but they are all smaller tubes so heat isn't a problem. You want to have the skill well in hand by the time you make it up to the heavy wall tubes in the carry-through. Ditto the motor mount bushings. > If I have trouble rotating 270 degrees clockwise, is it okay > to rotate 90 degrees counter clockwise (or even anti > clockwise)? It's counter clockwise north of the equater and clockwise south of it. Or is it the otherway around? I'd have to flush the toilet and check its rotation to remember. bd +++ #7534 Date: Mon, 3 Sep 2001 12:58:08 -0700 From: Russ and Penny Erb erbman@ Subject: Hot bend/Schmot bend I've been bending the upper left longeron. Bear-Tracks says "The upper longerons will require some heating to bend in the cabin area." I was concerned about burning up the table while bending. Reasoning that I had bent larger tubes cold at least as much, I thought I'd try it cold, first on a scrap, then on the longeron. Worked just fine. Also, because it is difficult to get a longeron in and out of the shop, I came up with a method to bend the longerons on the table. In general, it was a case of nailing a couple of blocks in place on the table, then pulling the tube across the table to get the right bend. Took a while, but worked just fine! I have some other ideas for cold bending the top and bottom assemblies out of plane for assembly. More on that when I get there. Russ Erb +++ #7542 Date: Tue, 4 Sep 2001 08:48:09 -0600 (MDT) From: Ken Beanlands kbeanlan@ Subject: RE: Fuselage finish welding There are probably many good ways to weld a fuselage together. When I did the Christavia, I elected to finish wild the two sides (the side frames are built first rather than the top/bottom) prior to adding the cross members. This ended up distorting the fuselage by quite a bit out of "plane". I built a jig out of 2x4 that went inside the cabin area to hold both sides together and in the right location. The clusters were clamped to the 2x4 structure to pull them back into shape. The whole mess was then welded together using the cross tubes and diagonals. Any cluster that did not have a cross member attached was heated to straiten it out. I built the jig using screws so that it could be removed piece by piece from the frame after welding. This worked quite well and I have a very strait fuselage. All of the finish welding to the frame was done before starting on the fittings for the same reasons that Mike suggested. Ken Beanlands B.Eng (Aerospace) +++ #7543 Date: Tue, 4 Sep 2001 09:38:32 -0700 From: "Kent White" kent@ Subject: RE: Hot bend/Schmot bend > Bear-Tracks says "The upper longerons will require some > heating to bend in the cabin area." I was concerned about > burning up the table while bending. Reasoning that I had bent > larger tubes cold at least as much, I thought I'd try it cold, > first on a scrap, then on the longeron. Cold bending works, if the part is held tightly enough to hold solidly, but not so tightly as to deform it. Wise also is he who considers annealing the "N" tube prior to making the tighter bends. Heat to dull cherry in dim light and let cool slooowly. I do not fill with sand. Rather....nontrivial unpublished point here direct from TinMan labs....I use water. But I lock off one end of the tube with a compression fitting, fill to meniscus max (for all you chemtech sorts) and then lock down the other compression fitting, avoiding any air entrapment. Mercury was the traditional internal die material years ago, back when it was also prescribed as an internal treatment for humans by the Medical Establishment. Neat thing with merc: when the tube is bent and the fitting leaks, the silvery jet is very attractive. Could almost tie a knot in soft copper using this method, tho. Have done 2" .090 wall 4130N for rollbar using the water. Oh...yes...for the persnickety sorts: tap water is fine..... room temp.... any Ph. I know about serrobend, guys, but sheesh, the time...... the cost....... When bending "sharp" bends using an internal filler, be sure to use some sort of a shaped guide for the tube to lay in, as it will help prevent deformation. An electricians' hickey is a good start. Hossfeld benders are good, too. I also use two sand bags, span the gap twixt 'em with the tube, and thump tube with a dead blow soft face hammer. Makes any gentle radius bend you need with no marks...cold....and in plane. Ummmmm...that's about it... Kent White +++ #7544 Date: Tue, 04 Sep 2001 17:40:17 -0000 From: snorttheoneandonly@ Subject: Re: Fuselage finish welding I remember having read this somewhere. It was in Sportplane Construction Techniques by Tony Bingelis(page 66): "Always start to finish-weld a tacked fuselage at the firewall and work toward the tail end, a single bay at a time. Complete welding each cluster before moving to the next bay. This method should minimize the amount of distortion and misalignment resulting from the welding process". And further: "I would advise against installing and attempting to align any fittings until after the basic tubular structure has been completed..." You guys probably have this book anyway and I don't mean to cause controversy by including it. Just curious if anybody's had experience doing it both ways! I'm not sure what that means, but it sounds terrible! :) Snort +++ #7545 Date: Tue, 04 Sep 2001 11:10:23 -0700 From: Budd Davisson buddairbum@ Subject: Re: Re: Fuselage finish welding I've done it both ways and prefer to start at the tail and control the distortion as I go although the difference isn't great. the further you get up the fuselage, the stiffer the back half becomes and the better my welding gets. bd +++ #7546 Date: Tue, 04 Sep 2001 11:46:03 -0700 From: "Bruce A. Frank" bafrank@ Subject: Re: Re: Fuselage finish welding I haven't built my fuselage from scratch, but I have added a significant amount of new tubes and bays while lengthening the structure. My experience is that no fittings or brackets that need to be aligned with other parts should be installed before the basic fuselage is fully welded. I tacked a number of parts into the areas of the fuselage which had only been tack welded first. Every single part had to be taken off and repositioned after I finished welding the 36" extension in my fuselage. An interesting point here, if you have ever looked at a Pacer or TriPacer, that hasn't been rebuilt, from the rear you may notice that the tailpost leans slightly to the left side. Years ago I talked to a worker who had been involved with the factory fabrication of the TriPacer. I was asking if that tilt had any aerodynamic purpose since all the fuselages I saw had it. He chuckled and said that the jig was slightly out of alignment and that combined with the welding sequence brought about that slight twist. It was noted, but conclusions were that it had little to no impact on the aerodynamics of the aircraft and very many fuselages had been made that way so no effort was made to fix the "problem." Bruce A. Frank +++ #7547 Date: Tue, 04 Sep 2001 12:03:22 -0700 From: Budd Davisson buddairbum@ Subject: Re: fuselage accuracy. Re: accuracy in fuselages. Bruce brings up a good point here. There are no fuselages of any kind with the tailpost exactly in the middle. All of them are off 1/4-3/4" and I've flown at least one airplane, the first customer-built Acro Sport on which the tail post was a solid 1" out with a little twist. Although we all desperately try to make it perfect, if it's out a little, it's not the end of the world. Anything in the 3/8" category is probably okay. You can often straighten out a fuselage with heat, but be careful because it's hard to accurately predict the amount of movement you may induce by shrinking tubes on purpose. What IS important is aligning the wing and landing gear fittings as accurately as possible to the tail post. The airplane doesn't really care if the fuselage is straight as long as the tail, wings and landing gear are in the correct relationship to each other and that is done with the fittings. bd +++ #7548 Date: Tue, 4 Sep 2001 13:43:11 -0600 (MDT) From: Ken Beanlands kbeanlan@ Subject: Re: Re: fuselage accuracy. Best of all, there is no way to really tell that you are out without going to the plane with a tape measure. Only EAA judges are that picky ;-). The Christavia is within 1/4". Ken Beanlands B.Eng (Aerospace) +++ #7550 Date: Tue, 04 Sep 2001 19:58:17 -0000 From: zipppydoggg@ Subject: Re: Hot bend/Schmot bend > (edited) I do not fill with sand. Rather....nontrivial > unpublished point here direct from TinMan labs....I use > water. (edited) Good point about the water, I'll try it. However, when I do use sand, I weld one end of the tube closed, and weld a large (3/4 inch or necessary for tube size) nut to the other end. I fill with sand (use funnel), then insert a threaded rod through the nut into the sand to get a good tight pack. Use only dry sand. Rob "looking forward to the blacksmith work" Gaddy +++ #7552 Date: Tue, 04 Sep 2001 20:17:15 -0000 From: zipppydoggg@ Subject: Re: fuselage accuracy. I fully agree with bd. I built 2 steel tube fulelages. After everything is welded, I got a 2X4 and with aid of a torch, straightened out the tail relative to the gear and wing attach points. Everything else can fly in loose formation. By the way, on the two that I built (Sonerai IIs) I should have bent the longerons outward, so that when the fabric gets tight, the tubes will be pulled back straight. As it was, the longerons were slightly bent inward. Only builders (or judges) would have noticed. Rob "another $.02 spend on this project" Gaddy +++ #7553 Date: Tue, 04 Sep 2001 13:37:27 -0700 From: "Bruce A. Frank" bafrank@ Subject: Re: Re: fuselage accuracy. The TriPacer fuselage, as I bought it, never crashed that I could detect by looking at the bare fuselage or the log book, measured 1.5 inches longer distance from the rear wingspar mount point on the right side than from the rear wingspar mount point on the left side (Which I measured 6 inches from the bottom of the tailpost. The top of the tailpost was even further away.) There were several notes in the log book by the AI doing the annuals as to how nicely this plane flew. (This fuselage was salvaged not because of damage but because of the need for a recover...partially completed they stored for more than 20 years). Bruce A. Frank +++ #7555 Date: Tue, 4 Sep 2001 16:53:51 -0500 From: "Collin Campbell" collinc@ Subject: fuselage welding Since I just completed welding up my fuselage and noticed some comments about welding, I thought I may as well throw in my 2 cents. I think Bud did a good job explaining the process. Mostly what I did with maybe a few exceptions. I started welding at the tail, worked forward with everything still in the jig. I didn't try to do the whole cluster at one time, it didn't seem feasible to me since you would have to rotate the whole assembly which would mean shutting down the torch, rotating the whole thing and then relighting the torch etc. By this time I figured the cluster would need reheating anyway so I abandoned this idea. One thing I highly recommend is to always try to weld in a comfortable position. It is so much easier to get good quality welds this way. I tried to avoid all the overhead, vertical difficult to reach positions I could. If you are a professional welder, or course go for it, but for most of us our welds will look better if we do them in as comfortable position as possible. Helps greatly to have something close by to steady your torch hand. Someone suggested using a pair of smooth jawed vice grips to move around to rest on. I didn't try this but think it would work fine. One thing that I feel is important and that is not to get into a big hurry. Take your time, let one cluster cool before going on to the next. If you start welding on a cluster next to the one you just finished and it is still hot--you are going to have a lot of distortion problems. After I had welded all the comfortable, easy to reach places in the jig, I placed it on two sawhorses where I could place it in various positions, where once again it could be welded in a comfortable position. Can't say that enough--COMFORTABLE POSITION!! Some of the clusters had to be heated up 3 to 4 times in doing it this way and I realize it may take somewhat longer, but I was quite pleased with my welds. Some of them even looked somewhat like Bill Johnson's, if I do say so myself! Total time to finish weld the entire basic fuselage (minus any wing--gear fittings) was 35 hrs. I used the Meco torch with #1 and #2 tips. Collin Campbell +++ #7579 Date: Wed, 5 Sep 2001 08:56:57 -0700 From: "Kent White" kent@ Subject: RE: Re: Hot bend/Schmot bend Should you require the sandbox method....remember to pack the sand....tightly. I recommend the sand rammer supplied with the BH tooling: Ye rivet gun. add a straight long set to it and ram away. Kent White +++ #7608 Date: Thu, 6 Sep 2001 17:16:54 -0700 From: Russ and Penny Erb erbman@ Subject: RE: Re: fuselage accuracy. > By the way, on the two that I built (Sonerai IIs) I should > have bent the longerons outward, so that when the fabric gets > tight, the tubes will be pulled back straight. As it was, the > longerons were slightly bent inward. Only builders (or > judges) would have noticed. I've heard this suggestion before, but I've always been skeptical of it. Primarily because how would you know how much to bend them outward and in what direction. I suspect this is more of a problem with dope finishes than the newer covering systems. I checked with Jon Goldenbaum of Poly-Fiber and he said "Russ, NO WAY! Bending longerons outward to mitigate bending from fabric shrinkage is a bad idea. If necessary, the designers should put in more cross structure. Cheers, Jon" Russ Erb +++ #7617 Date: Fri, 07 Sep 2001 15:33:29 -0000 From: zipppydoggg@ Subject: Re: fuselage accuracy. > Jon Goldenbaum of Poly-Fiber and he said "Russ, NO WAY! > Bending longerons outward to mitigate bending from fabric > shrinkage is a bad idea. If necessary, the designers should > put in more cross structure. Cheers, Jon" Russ Erb #164, > Edwards CA Wonder why? Rob Gaddy +++ #7618 Date: Fri, 07 Sep 2001 11:14:28 -0700 From: Budd Davisson >> 2mar02 #7686-9153 +++ #7700 From: "Joe Hemmer" Subject: Re: Wow! More Pix! Russ, I have had good results using cross-braced conduit, fastened to the airframe with hose clamps, and carefully measured and adjusted to square. No jigs at all, just lots of cheap 1/2" electrical conduit and lots of hose clamps. Good luck. Joe Hemmer +++ #7728 From: Russ and Penny Erb Subject: Confessions of a Reformed Blacksmith I've been thinking about writing this for a while. The issue is accuracy and precision of fitting up parts. Specifically, it goes back to a discussion several years ago about pipe notchers, such as "The Ol' Joint Jigger". At the time, there were those, such as bd, who claimed such devices were of little to no use, and those like me, who thought they were cool toys that allowed very precise fits between tubes, and thus would be very useful. Of course, the difference was that bd had actually built a steel tube fuselage and I hadn't. Let's jump to the end and say that my tubing notcher is collecting dust and rusting from non-use. While making the steel parts for the wing, the notcher seemed to work really well. Of course, that was on perfect T's (90 deg joints). On the non-T's, I even found myself using a grinder. Maybe I'll dust off the notcher when I get to the rudder pedals. As I started into the fuselage, it occurred to me that there are virtually zero (count them, 0) pure 90 degree joints (or joints with angles easy to determine). Hence, if I wanted to use the tubing notcher, I would constantly be setting it up to different angles, assuming I could figure out what the proper angle was. Let it be said here that RANS uses a CNC mill to cut their fishmouths, but they're doing PRODUCTION. When you're going to make several hundred or more of a part, it's worth the time to figure out exactly how to machine it. Most of us are doing one-off custom fuselages, and it's quicker to do it by hand as we go along. What budd had said at the time was that it was much easier and quicker to just use a grinding wheel to grind in the needed fishmouth on the tubes. This seemed like it would be hard, but much too my surprise I found that after you just start doing it, it's not that hard at all. Typically I can just mark how deep the fishmouth needs to go, then step to the grinder and I'm done with a tube in about 5 minutes or less. You will quickly develop a feel for what it should look like, such that it doesn't take very many tries to make it fit. I'm actually getting good enough at it that I'm scaring myself. Why? Because I feel myself getting cocky and trying to grind the entire fishmouth before trying the fit. One of these days I'm going to try that and find I've ground off too much. One important key is to realize that the fit doesn't have to be as precise as you are/were used to working with in aluminum. That is, the acceptable tolerances are much bigger. In aluminum, you may have been trying to maintain tolerances from zero to a few thousandths, and probably well less than .020. However, in welded structure, tolerances of 1/16" (.063) or possibly a little larger are perfectly fine. Why the difference? Because the welding closes up the gaps! What a great concept! In some cases, you even want that much gap, so that a tube doesn't bend the fuselage out of position when it expands from the heat as you weld one end. bd has compared it to blacksmithing. My experience is better described in woodworking terms. To wit: Working with aluminum is like building cabinets. The cabinet maker strives for very tight fits. On the other hand, working with steel tubing is more like framing a house, sometimes called rough construction. It's still important to do it right, but a "sloppier" fit is still acceptable (within limits, of course). A 1/16" gap between a stud and joist is considered a pretty good fit. The same gap on a cabinet face would be absolutely unacceptable. (Maybe Planter Bob should frame his house in steel tubing--maybe even cover it in fabric...) Kent White teaches the snip/grinder method of fitting tubing on his 4130 tapes (whadya mean you don't have your own copy yet?). Fitting tubes seems to take on the feel of an artist rather than the technician. Don't worry about being overly precise and "go with the feel". So what's my point? Our friends building RVs or Glasairs/Lancairs or many other airplanes have the luxury of working primarily in one form of construction throughout the project. We have at least two--aluminum sheet metal and steel tubing. The techniques and mindset that work for one may not work for the other. Be ready to make that shift when appropriate. Erbman #164, Edwards CA +++ #7729 From: "Bruce A. Frank" Subject: Re: Confessions of a Reformed Blacksmith This has certainly been a topic of discussion on RAH also. I also bought the Joint Jigger several years ago. I bought it because I had a shyster who wanted me to build gear legs for him as he was going in to production of the V-6 STOL. I built jigs and laid in appropriate quantities of round and streamline tube. The Joint Jigger was a beautiful asset and after several pairs of gear legs I was comfortable with the tool finding it easy to adjust angles quickly even for one-off pieces. The draw back was that the JJ was poorly constructed. While its application was best suited for production it was constructed like a one project tool. I rebuilt it a couple of times finally machining my own replacement parts out of better quality materials. About that time Elwyn Johnson, then owner of Northwest Aero, sent a sample of a "better" Joint Jigger for me to test. A dramatically superior product that has lasted years instead of days. I still use the NWA Joint Jigger though I build only a couple of things a year for which I find it useful. My point is that once the tool is mastered it is easy to use through its full range of angles. BUT, if one is just going to build a single plane, do not buy a Joint Jigger. If you are really fascinated with the tool buy the cheap Harbor Freight version which is 100% equal to the brand "'Ol Joint Jigger." A better setup for grinding fishmouths on the tubes is a pedestal or benchtop grinder that has had the face of the wheel dressed to a radius. My favorite, allowing me to stand right there inside the framework of the fuselage and grind to fit, is a hand held angle grinder with a 4.5" hard rounded-edge wheel. Straying a bit more, a few years ago someone told me about a freeware computer program that drew templates for cutting fishmouths. This was designed for building bicycles, but all you had to do was plug in the angle and diameters of the tubes coming together and the program would print out a wrap-around template for the fishmouth that was absolutely perfect. I loved the program, actually built a three wheel recumbent peddle cycle using it, but I found it impractical for building a fuselage. Bruce A. Frank +++ #7730 From: bearhawk260@y... Subject: Re: Confessions of a Reformed Blacksmith I found a program called Tubemiter. Enter tube size/angles and it will print a template that attaches to the tube. I hope this helps... Go to the files section. file is called tubemiter.exe Bearhawk260 +++ #7731 From: bearhawk260@y... Subject: Re: Confessions of a Reformed Blacksmith Also see TubeMiter.txt, also in the files section. This will explain the program inputs and the output drawing. bearhawk260 +++ #7732 From: Ken Beanlands Subject: Re: Confessions of a Reformed Blacksmith Another point is that if you weld in the longerons, and then the cross members, there is no way to put the diagonals in the frame if you have a tight fit. I had a few occassions on the Christavia where one of the points on teh fishmouth had to be ground away to allow the tube to fit in the frame. It's easy toweld in the 1/4"- 1/2" gap left behind. One other point I'd make is to buy the biggest bench grinder you can afford and then get a 'wheel dresser" to shape the wheel into an arc so that the fishmouthes are circular to begin with. THe Christavia primarily uses 3/4" tubing so I bought a 3/4" wheel for my 8" grinder and shaped that to the half circle. Another tool I found invaluable was a 4" side grinder. It makes short work of cutting tubing and metal. A circular saw with an abrasive wheel is also a useful tool. At one point I tried to mount a cutoff wheel in the table saw. It eroded too fast and also started a fire in some sawdust I had missed in the table saw. It was a little exciting and I chalked it up to the learning curve ;-) Ken Beanlands B.Eng (Aerospace) +++ #7736 From: Russ and Penny Erb Subject: RE: Cutting tube and Hydraulic presses > Why not invest $60 in a 14" cut-off saw from Harbor Freight? > Look like a good deal. Because I can cut the tube on the horizontal/vertical metal cutting bandsaw that I already have? I have become dis-enamored (if that is such a word) with the fiberglass cutoff wheels, typically about 3 inches in diameter. This is primarily for health reasons. Whenever I use one of these, the cutoff wheel seems to slowly disintegrate and throws microscopic pieces of itself everywhere. The problem seems to be these pieces hitting bare skin, such as my arms, and causing irritation. It is the same effect I get when handling fiberglass insulation. The effect can be reduced by wearing a long sleeve shirt, which is typically hot around here. Additionally, breathing the dust results in an irritated throat. This can be reduced by use of a respirator. These are my results--your mileage may vary. Therefore, if I can find another way to accomplish the task, I'll use the other way. Oddly enough, I haven't had this problem with the little fiberglass wheels for my Moto-Tool. Those work great. Russ Erb +++ #7758 From: zipppydoggg@y... Subject: Re: Confessions of a Reformed Blacksmith > One other point I'd make is to buy the biggest bench grinder > you can afford and then get a 'wheel dresser" to shape the > wheel into an arc so that the fishmouthes are circular to > begin with. I've used this technique also, with great success. One small point is offered. I understand that after shapeing with an abrasive wheel, the fishmouth should be lightly dressed with a file to remove any (possible) imbedded grinding wheel material / grains. This material could cause impurities (carbides) in the weld. Rob "didn't do the metalurgy myself" Gaddy BH401 +++ #7789 From: Russ and Penny Erb Subject: RE: TEST Here's my best guess at what Corky probably said. A while back, the word went out that the mills for some reason had decided to stop producing 2.023 x .857 x .049 streamline 4130, which is called for on the landing gear shock struts. I put in an order for my fuselage tubes with Mr. Vogelsong on 9 August. He told me that this tubing was no longer available. His solution was simple--use 2.023 x .857 x .065 streamline 4130, which is readily available. Same outside dimensions, just a little thicker. More weight, more strength. Best part--doesn't require redesigning the whole part. Cancel the panic. Russ Erb +++ #7790 From: "Ted" Subject: Re: TEST It all depends on where you look! I could have over 2000 feet of the 2.023 x .857 x .049 streamline 4130 tubing tomorrow if someone wanted it, but my regular supplier doesn't stock it in .065 wall at all ... Ted Fontelieu +++ #7896 From: pfflyerz@c...> Subject: oiling tubes: was Erbman's wing takes a ride I too drilled #40 holes at all tube junctions in anticipation of oiling the insides when I finished welding. After completing that task, I reread in the Bingellis books that a larger hole size is recommended. I got to wondering if the #40 hole would be too small to allow adequate oil passage, but it is too late to do anything about it. I also drilled large holes in the rudder post, at each longeron, figuring the easiest way to get oil into the tubes would be to simply pour it into the top of the rudder post and let gravity do the rest, but now that the vertical stab is finished I no longer have that hole available. I guess I could drill a 1/4 inch hole in the channel at the top of the rudder post, but what do I do with it when I am done? I could use one of those plug screws in a smaller hole, but I don't relish trying to dribble that much oil through a 1/16 inch hole. Trying to weld over a larger hole sounds like a good way to create a bomb. Anyway, I've done the ground work, but am now leaning towards just oiling the lower longerons for the sake of simplicity. Any ideas on how to seal a large enough hole so I won't spend forever getting oil into, and then again out of the fuselage? Progress report: #232 now has a Barrow's built O540 hanging on the front. I have a mockup instrument panel mounted and a nose bowl and spinner mounted and am fashioning a firewall formblock to fit with the contours of both. This stuff is so much fun. Pat Fagan #232 Pearblossom, CA +++ #7899 From: Russ and Penny Erb Subject: RE: oiling tubes: was Erbman's wing takes a ride I have seen sources recommending hole sizes from 1/8" down to 1/16". It doesn't really matter, as my experience with the wing parts is that the Poly Fiber Line Oil will wick itself through the smallest cracks. It was coming through pinhole leaks in the welds, so a #40 hole is plenty big enough. This oil is amazing--it will wick itself uphill (some sort of capillary action or something) until it has covered everything. It will also eventually congeal in any pinhole leaks and seal them. My plan for filling is a #30 hole near the rear of each longeron (away from the fabric). Shoot in the oil with a syringe like comes with Poly-Fiber Metal Prime (request one when ordering the oil). Seal the hole with a Cherrymax Rivet (CR3213) as listed in the Spruce catalog. If you want a bigger hole, drill #21 and use a -5 Cherrymax rivet. The catalog makes it sound like it needs a special puller but I used my "normal" blind rivet puller just fine. I did this on the wing steel parts and the rivet makes a good seal. I liked it a lot better than a self-tapping screw. Welding over the hole would defeat the purpose, since the oil treats the scale that comes from welding--don't produce more scale after oiling the tubes. It's interesting enough watching the oil that comes on the inside of the tubes from the mill burn after welding. Russ Erb +++ #7900 From: pfflyerz@c... Subject: Re: oiling tubes: was Erbman's wing takes a ride << Shoot in the oil with a syringe >> That is exactly what I hoped to avoid. Unless you are using a syringe sized for a horse you will be at it all day, might even develop carpel thumb syndrome. Of course, with all that wicking action, maybe you don't have to "fill" the tubes with oil, but I think you would be more certain of complete coating if you did. Pat Fagan #232 Pearblossom, CA +++ #7901 From: Mark_Deacon/MSP/M... Subject: Re: [Bearhawk] oiling tubes: was Erbman's wing takes a ride When I was working at Classic Aircraft in Lansing, MI we oiled the entire fuselage. 1/8" holes were drilled at the clusters and the fuse mounted in a rotisserie. Two holes were drilled in opposite corners of the structure, then a pressure pot filed with the old boiled linseed oil was attached and force fed into the tubes. We used an old 2 gl pressure paint tank but one of the old timers had converted a pressure cooker he found at a garage sail for the same purpose. Rotate her 180 deg. a couple of times and then drain all the excess you can. (blowing thru the opposite hole helps) then weld up the holes. Don't sweat the welding we never blew one up, I don't think it's possible. Mark Deacon +++ #7902 From: "Bruce A. Frank" Subject: Re: oiling tubes: was Erbman's wing takes a ride The "bayonet" grease fitting available for hand held grease guns easily fits into a #30 hole. The standard lever pump hand held grease gun will hold a 2/3rds a quart of line oil and mine doesn't leak if I hold and pump it with the hose pointed down. There is also a "hypodermic" style grease gun hose nozzle fitting available in most auto parts stores that will fit even 1/16" diameter and smaller holes. As for closing off the filling hole, if it is a #30 hole a 1/8" closed end pop rivet works just fine...no need for a cherry max. They also make a pop rivet with an "O" ring seal under the flange, but I haven't found them necessary. Any leaks of the rivet itself is sealed by the line oil also. Just place the fill hole high on the fuselage and on the top if the tube. Bruce A. Frank +++ #7905 From: charles.k.scott@d Subject: Oiling tubes This may sound heritical but I decided not to oil the inside of the tubes at all. I thought about it a great deal and decided that the airplane would outlive me by many years, and likely outlive my son, should he decide to learn to fly. If you weld everything properly and paint it properly and keep it out of constant rain, corrosion from the inside of the tubes can't happen anyway. I weighed that against the incredible complexity of making sure you drilled all those holes and then pouring oil into the fuselage and tipping it and turning it and then trying to drain it out. It just sounded like a whole lot of trouble for nothing I really needed to worry about in my lifetime. Corky Scott +++ #7906 From: Russ and Penny Erb Subject: RE: oiling tubes: was Erbman's wing takes a ride No need to fill the tubes completely. The can tells you how much to put in. The stuff is like tea on a tablecloth--it gets everywhere, whether you want it to or not. Erbman +++ #7907 From: Budd Davisson Subject: Re: Oiling tubes I agree with Corky. bd +++ #7915 From: Jimmy Mathis Subject: Re: oiling tubes: was Erbman's wing takes a ride Warm the oil up, pour into garden sprayer, set for small stream and fill tubing. Use caution in heating oil, keep a thermometer (get cheap one at walmart) in the oil as you are heating so you don't get it hot enough to melt sprayer (or use a stainless steel sprayer) You might experiment on some kind of attachment to hook sprayer hose directly to steel tubing. Jimmy 501 +++ #7916 From: pfflyerz@c... Subject: Re: oiling tubes: was Erbman's wing takes a ride Great ideas on oiling the tubes, thanks guys. I appreciate that it is probably not necessary, but I have already done the scut work, might as well follow through to the end. And now, I'm off to see the wizard. Pat Fagan #232 +++ #7973 From: Russ and Penny Erb Subject: 113 lbs That's how much it weighs. I've finished the tacking of all of the primary tubes in the fuselage structure (except for the tacks on the bottoms of the joints--I'm going to do those when I can turn the fuselage upside down) and have removed it from the jig and table. Its weight (minus the various fittings, sheets and channels) was 113 lbs. While building up the fuselage, the tailpost was a tube attached to the table and the ceiling so that it wouldn't move around as the various tubes were added. The best part was that when I cut off the extra length of the tailpost to something closer to its final length, the tailpost didn't move. It stayed right where it was, indicating to me that it was still aligned and not under residual stress. Of course, we'll see how it's doing after the whole fuselage is welded... Next I'll turn the fuselage upside down and do those underside tacks. After that, I'll get started on the finish welding of the primary structure. Russ Erb +++ #7980 From: Russ and Penny Erb Subject: More Erbman Fuselage Pix! After a few more tack welds around the firewall station, my fuselage will be ready for finish welding. It's off the table and upside down in the garage. Whoever it was that said a bigger welding tip would be needed (bd?) when welding around the clusters was right. With all of that extra metal, I'm using the #2 tip on my Henrob 2000. Of course, acetylene consumption goes up as well. I picked up a B acetylene cylinder on Thursday, and it will probably be empty tomorrow. Just a little faster than it's gone in the past. Then again, you should see the size of Pat Fagan's welding tanks--I don't know how big they are, but they're huge! Pat probably welded the whole airplane on one tank. I've posted 3 more pictures on my web page. Below is the links and text for those of you who don't wish to bother with going to http://www.eaa1000.av.org/pix/erbpix/erbpix.htm http://www.eaa1000.av.org/pix/erbpix/10260011.jpg Primary fuselage tube structure tacked together. The fuselage was allowed to escape the garage workshop temporarily while the tables were removed to make more room to do the final welding. At this point, the fuselage still needs to go back in upside down and have the tacks on the bottom side done. http://www.eaa1000.av.org/pix/erbpix/10260012.jpg I had long planned a rotisserie for the fuselage to spin it around to make the welding easier. As the time approached, I realized the workshop wasn't long enough to support such a device. Therefore, I attached 4 2x4s to the engine mounts as suggested in the Poly-Fiber literature for covering the fuselage. Still very effective, and allows a minimum of four positions to choose from. Rotation is done by picking it up and manhandling it to the next position. So far I've been able to do it without assistance. Note that in this picture the fuselage is inverted. http://www.eaa1000.av.org/pix/erbpix/10260013.jpg Also per the Poly-Fiber literature, a simple sawhorse is used to support the tail of the fuselage. Russ Erb +++ #8027 From: Russ and Penny Erb Subject: RE: Digest Number 590 > HI Russ, when you did your airframe, did you do the cargo doors? Yes, I did the cargo doors, or at least the hole for the doors (haven't done the doors themselves yet). The finish (Finnish? Welding east of Sweden?) welding of the clusters slows it down quite a bit. I'm not projecting when I'll be done with that since I know it won't be in the next few days and the answer would be depressing. Russ Erb Consuming Acetylene at a higher than normal rate... +++ #8046 From: pfflyerz@c... Subject: Re: Digest Number 591 > on the cargo doors that are on Proto ll, how did Bob seal the > doors to keep out the wind. I have the cargo doors on my plane and they are sealed the same as the front doors and windows, by the aluminum skin that crosses the gap. It looks as though they will seal plenty tight. It you have the door plans, you will see that Bob drew a door stop for the bottom door sill, but if you look at the pictures of his plane, he didn't use one. The stop wasn't necessary as the overlapping door skins act as a door stop themselves. The cargo doors are nicely designed ( what would you expect) and I would recommend them to everyone. Pat Fagan #232 Pearblossom CA +++ #8048 From: "Float-By Shooter" Subject: cargo door seals/stop Not only is the stop not necessary, it was probably left off so that cargo won't catch on it during loading/unloading operations. I would still personally prefer some sort of weatherstripping along the inside edge of the overlapping door skins, to provide an anti-chafe surface if nothing else. A thin (1/16" -1/8") soft rubber seal glued to the inside of the door skin along the edge should provide a nice seal, and allow the door to close snugly with no rattling. A marine supply place might have something which will work well. Del Rawlins +++ #8049 From: nov222pa@c... Subject: Re: cargo door seals/stop > A thin (1/16" -1/8") soft rubber seal glued to the inside of > the door skin along the edge should provide a nice seal, and > allow the door to close snugly with no rattling. Nice even gap along the mating edges has got to help. I bet a lot of different stuff has been stuffed to stop drafts. Kind of along "How to stay warm" is: I wonder how'd it work, to weld some clips on to hold panels of insulation under the covering? Anything like this work out in the past? Fred +++ #8050 From: Russ and Penny Erb Subject: RE: cargo door seals/stop I've thought about the insulation thing, but have yet to come up with a suitable solution. I thought about just stuffing some fiberglass between the fabric, but I suspect that would collect moisture, with its attendant corrosion and additional weight. This would then suggest some closed cell foam, but I don't think that would be effective unless it was tightly fit into the frame (otherwise the heat would leak out around the edges). I don't know what a suitable foam would be, but it would still add weight. So what do you guys in Alaska and the northern climes normally do? Especially in tube and fabric fuselages? Russ Erb +++ #8052 From: "Del Rawlins" Subject: RE: cargo door seals/stop > So what do you guys in Alaska and the northern climes normally > do? Especially in tube and fabric fuselages? Crank the heat and/or dress warmly. Seriously, my brother took out the stock interior from his Citabria and made some low maintenance panels out of aluminum sheet and some thin (~1/16") plastic panel material. His plane has a very effective cabin heater and I've never heard him complain about being too cold in it (usually the opposite). I don't think I'd bother with insulation unless it turned out that I hadn't built a very good cabin heat system. Of course, if you've got a fabric interior ala The Bob, that might be a little difficult. I'd also be very concerned about flammability of the insulating materials. I think in the winter I'd rather depend on dressing warmly rather than insulating the interior of the plane. In the event of a forced landing where you have to abandon the plane, you'll be far less concerned about hypothermia if you are already dressed appropriately. Of course, I'm skinny enough that the extra bulk of winter clothing isn't going to bother me as much in the cockpit. Del Rawlins +++ #8053 From: "Bruce A. Frank" Subject: RE: cargo door seals/stop > I've thought about the insulation thing, but have yet to come > up with a suitable solution. When I took apart the Piper Colt I salvaged for my project all the cabin and luggage area was paneled with painted thin aluminum sheet. All of the sheeting had 2" thick fiberglass glued to its back side with void areas where it would have come in contact with tubes. The fiberglass did not actually touch the tube in most places. Some places where it did there was a layer of plastic between the tube and the fiberglass (the plastic was bonded to the fiberglass like the paper on housing insolation). This Colt was of 1963 manufacture. The fiberglass was original and there was no rust or corrosion of any kind in the cabin area insolated with the fiberglass. The fiberglass was no more dense than the high quality stuff used for houses. Even the floorboard aluminum had fiberglass glued to the bottom side. Parts of the floor that were not covered with fiberglass were coated with black tar-like material similar to automotive undercoating...apparently to deaden sound and oil-canning. Even the outside skin panels that moved with the suspension attached to the Hydrosorb unit had a fitted layer of fiberglass on the inside. The headliner in the plane was vinyl fabric (sort of a Naugahyde type material). There was a layer of Fiberglas filling all the areas between that headliner and the outside of the cabin. This fiberglass was bonded to a open fabric scrim with a layer of plastic bonded to that. The plastic layer rested on the headliner. The fiberglass insolation in the headliner area was assembled to fit the inside shape of the fuselage. I mean that these were not just bats of insolation cut to fit the space, but sections of batting that were cut and glued together in the shape of the cabin with the scrim glued to the inside layer. The scrim was continuous so it had obviously had been bonded after the fiberglass was shaped. If I had tried to take it out in one piece it would have exactly mirrored the shape of the top half of the cabin. Many places in the roof area of the cabin the fiberglass had been tied with fine wire to the tube structure to hold it in lace and keep it from shifting and sagging. Even the sheet of aluminum that was the back end of the luggage compartment had a layer of fiberglass insolation on the back side. The cabin side of the firewall was covered with bonded pieces of fiberglass that matched the tube pattern of the firewall. The cabin side of the fiberglass had a fabric layer glued to it. Cable routes through the fiberglass were not voids, but it appeared that the fiberglass batting had slits completely through it to give a non-rubbing area for the cables to run. I was told by others in the hangar that this was an optional factory package intended to reduce cabin noise, but also dramatically improved cabin warmth in cold climates. Bruce A. Frank +++ #8055 From: "W. Shalm" Subject: Re: cargo door seals/stop > ... I'd also be very concerned about flammability of the > insulating materials. I agree Del when it comes to foams. Foam insulations are deadly toxic when enough heat is applied to make them smolder. A guy would be in la-la land long before the plane landed/crashed. Warren +++ #8062 From: pfflyerz@c... Subject: Re: cargo door seals/stop Will Graff insulated his Bearhawk, but I didn't discover this fact until he was preparing to go home, so I wasn't able to ask him what he had done and how. I did notice that he had a foil backed insulation blanket on the back of the firewall. I had planned to unsulate mine, not so much for cold, but to cut down on the noise. Since then, I have heard such good things about the Lightspeed headset that I have decided to save the weight and just buy a GOOD noise canceling headset. I will still probably do the firewall blanket and do some sound deadening on the floor boards though. Pat Fagan #232 Pearblossom CA +++ #8141 From: "Chris Vuxton" Subject: Fuselage Construction - sides or botoms and tops Is there some reason the plans lay out the top and bottom instead of the sides? It seems like you could do the bends easier if you did the sides first and then jigged the top and bottom cross members. Chris Vuxton +++ #8161 From: Russ and Penny Erb Is there some reason the plans lay out the top and bottom > instead of the sides? It's easier that way. As is, after building the top frame and bottom frame flat, there are 3 bends to make in the bottom frame and 2 to make in the top (5 total). If you built the sides first, you would have 6 bends to make in each side (12) and they wouldn't be the same at the bottom and the top. When you get a good look at an extant fuselage, you'll see that the sides are far from being flat, while the top and bottom are flat except for bends in one dimension. The idea of building the sides first comes from designs like the Piper Cub where the sides are flat and identical. That let you use the same jig for both sides. Not the case on the Bearhawk. Russ Erb +++ #8163 From: Budd Davisson Subject: Re: Fuselage Construction - sides or botoms and tops Even the top truss isn't flat because of the little "peak" where the tubing is raised mid-truss over the middle of the back seat. "tain't nuthin' straight in a Bearhawk" bd +++ #8165 From: Russ and Penny Erb Subject: RE: Fuselage Construction - sides or botoms and tops > Even the top truss isn't flat because of the little "peak" That would be what I've taken to calling the "vaulted ceiling"... Of course, if you're not careful how you put your "ceiling" in, you can lose some headroom. In case you haven't noticed, about a third of the fuel sight tube on the prototypes is above the fabric ceiling and thus not visible. Russ Erb +++ #8183 From: Russ and Penny Erb Subject: Fuselage Frame Welding Complete! I welded the last cluster of the primary fuselage truss a couple of hours ago. It should be all stiff and (reasonably) dimensionally stable now. Of course, looking at the plans and Mike's fuselage picture book, I see a true example of the 90% rule. The truss looks very much like a fuselage, so it looks 90% complete. Studying what's left shows that it's truly more like 10% done, i.e. 90% to go. So endeth the Major Visual Progress (MVP) for a while...time to start all of the little fittings... Russ Erb +++ #8184 From: "Bruce A. Frank" Subject: Re: Fuselage Frame Welding Complete! Now go back and look at every junction and cluster for the weld that you missed. The one I found (1/8 of the circumference was unwelded) showed up when I was painting the fuselage!!!!! Wouldn't you know it!!!!! Bruce A. Frank +++ #8185 From: pfflyerz@c... Subject: Re: Fuselage Frame Welding Complete! Way to go Russ, you now get to move from MVP to MMP (major monetary progress) mode. Pat Fagan #232 Pearblossom CA +++ #8188 From: rsmith@a... Subject: Re: Fuselage Frame Welding Complete! Way to go Russ! Question: I just finished tacking the top and bottom frames. When hot bending the fuselage frames in the five places did you get a friend over with another torch so you did both sides simultaneously, or just work each side a little at a time. Seems like the first method would help prevent getting some twisting or distortion. Rod Smith #246 +++ #8190 From: "Del Rawlins" Subject: Re: Re: Fuselage Frame Welding Complete! > Question: I just finished tacking the top and bottom > frames. When hot bending the fuselage frames in the five places did > you get a friend over with another torch so you did both sides > simultaneously, or just work each side a little at a time. Seems like > the first method would help prevent getting some twisting or > distortion. Rod, I was just thinking about how I would do it since I normally work by myself and came up with the following: For the bottom frame, I'd get it securely clamped to the table, and then put a heavy screw eye in the ceiling over the tailpost location. Tie a rope to the frame and run it up through the eye, and hang a suitable weight from the end to provide tension. A small bucket that you could add wheelweights to should work fine. Then I'd screw an upright 2x4 to each side of the table and then a crosspiece between them at whatever height you want the frame to stop bending up. Play the torch flame over the bend locations a little at a time moving from one side to the other and it ought to slowly bend (depending on the amount of weight) itself right to where you want it. Move the uprights down to the next station and change the crossbar height for each successive bend. For the top, I'd first build the portion of the jig around the cabin and make it good and stout. Once the top frame is jigged in place, hang your weight from the tailpost location, place the crossbar and repeat the process. That ought to work unless there is some major flaw that I have missed. Del Rawlins +++ #8193 From: Russ and Penny Erb Subject: RE: Fuselage Frame Welding Complete! > Now go back and look at every junction and cluster for the > weld that you missed. You ain't kidding! Actually, I had planned to do that. I already had this experience once--every time I rotated the fuselage, I ended up having to search for what cluster I was working on. It wasn't glowing anymore, and I didn't want to go around grabbing clusters until I got burned. Anyway, one time I saw a cluster in welding position with a 1/4 around one tube unwelded. For some reason, I then realized that it was one station behind where I was working. I thought I had finished that one the day prior. It's tough to fully inspect a cluster when it's glowing at you begging to sear your flesh... Russ Erb +++ #8194 From: Russ and Penny Erb Subject: RE: Re: Fuselage Frame Welding Complete! Rod, it's really not that difficult. In fact, I think Del is concerned about the wrong problem. First, it's not that hard to get the tubes on both sides hot at the same time. I sat on a stool on the worktable between the two longerons to be heated. Using a torch with a fairly large tip (#2 on a Henrob 2000, or as Kent White calls it, the Schwarzenegger torch, because of its weight) I heated one longeron until it started to glow dull red without welding goggles (use goggles to light the torch and adjust it). Then move the torch to the other longeron and do the same. The principle here is that the longeron will not cool down as fast as it heats up. Once that longeron is glowing, move back to the first longeron. It's not glowing right now, but it won't take as long to start. Once it is glowing again, switch. Continue doing this until they are both glowing. The amount of time you spend on each longeron will get shorter with each cycle. The entire process takes about one minute or less. So to answer your question, I heated both sides at the same time with one torch using time division mutliplexing (TDM). Now that you've got the longerons hot, they have approximately the same strength in bending as cooked spaghetti. As such, the real problem is not so much having the strength to bend them as it is STOPPING the bending where you want it to stop. I used blocks cut to the proper height to define how far to bend the frame. On the top frame, the bend at station N is down, and I set up the jig to stop the bending at the right point. I heated the longerons and gravity did the work. As for bending up the bottom frame, I had originally intended to have my wife (who has about zero airplane building skills) do the bending with specific instructions. I ended up having an inexperienced friend help because my wife wasn't home when I was ready to do it. At the request of the government, I spent quite a few hours sitting on commercial airliners, airports, and hotels last week. While doing that, I made some significant progress on the next version of the Bearhawk CD. One of the things I did was the picture pages covering this very topic. Later today, I'll post the applicable portions on the web so Rod will have some additional clues to work with. I recommend getting your favorite beverage to consume while opening the page, because it will take a long time (that's why it's normally on a CD, to save download time). Russ Erb +++ #8198 From: Russ and Penny Erb Subject: Fuselage Clue-Bag Especially for Rod Smith as he gets ready to jig up his fuselage. Fire up your browser, go to http://www.eaa1000.av.org/pix/erbpix/frame/frame.htm, then go do something else while it downloads. This is an excerpt from the upcoming next version of the Bearhawk CD and HAS NOT BEEN OPTIMIZED for downloading from the web--I didn't want to take the several days required to do that. Once you get the page displayed, I recommend you save it to your hard drive, then right-click each picture and save it to the same directory. That way you'll be able reference it again without waiting so long. I'll remove this page at such time in the future as Version 3 of the BHCD becomes available. Russ Erb +++ #8200 From: "Del Rawlins" Subject: RE: Re: Fuselage Frame Welding Complete! > Now that you've got the longerons hot, they have approximately the same > strength in bending as cooked spaghetti. Actually I did take this into consideration in my proposal, but may not have done an adequate job of explaining it. The purpose of the crosspieces between the uprights is to provide a height stop for the frame. That way, the builder is free to concentrate on using the torch while the weights provide the bending force, and the crosspiece stops the bend at the correct location. Del Rawlins +++ #8210 From: rsmith@a... Subject: Re: Fuselage Clue-Bag Thanks Russ, some really great ideas shown. I really like how you left the tail post long enough to attach to both the table and ceiling. Too late for mine and its match drilled to the rudder. Rod Smith +++ #8217 From: "Del Rawlins" Subject: Re: Re: Fuselage Frame Welding Complete! > Way to go Russ! Question: I just finished tacking the top and > bottom frames. When hot bending the fuselage frames in the > five places... Admittedly the Christavia fuselage appears more simple than the Bearhawk (only one bend aft of the passenger compartment to taper to the tailpost) but here's what I did to do the bends alone. I welded both sides seperately, then jigged one of them on sawhorses so that the area of bend was hanging out past support. Then I calculated how much bend was needed, and set up a brace under the hanging part of the fuselage such that when the bend was achieved, the fuselage would stop against the brace. Then it was a simple matter of applying enough heat to the areas that are supposed to be where the bend occurs (I used the cutting tip of the torch, I don't own a rosette tip) and let gravity to it's job. Once the areas to be bent were properly heated, the tail end of the fuselage just sagged down to the brace. I let things cool off and voila, bend achieved. I did the same thing with the other side, only made sure it was flipped over so I didn't bend them both in the same direction. Then I jigged them both vertically and began cutting and fitting the horizontal pieces to connect the two sides together. Corky Scott +++ #8381 From: Russ and Penny Erb Subject: Stringers and such... I'm getting close to installing stringers on #164. I found out why the 5/8x5/16x.032 3003H14 stringers sold in the Spruce catalog are so cheap ($6 for 12 feet). The rectangular section is actually an open C-channel with a very small gap between the edges, and the edges are not welded together. This allows the stringers to be bent up from sheet rather than drawn into tubing, which presumably makes the process cheaper. I know that at least Pat has used these on his Bearhawk with good success. Now for another question for Bill, Pat, or anyone else who has been at this point: How did you determine the contour of the stringers? I can't find details on the plans, and it seems like a guessing game aided by staring at Mike's picture book... Russ Erb +++ #8283 From: pfflyerz@c... Subject: Re: Stringers and such... > How did you determine the contour of the stringers? This is your chance to be an artist. You can get an idea of where they need to begin and end by looking at all pictures. Make up your brackets and weld them to these points. Make up all your standoffs, but make them a little larger than you guess they need to be. Slip the stringer in the saddle of the standoffs, then CLAMP all the standoffs to the fuselage tubes. This way, you can then stand back and eyeball your line for straightness and for a pleasing contour. Once you have it right, you can tack the standoff with the stringer still clamped in place. Trust me, I tried measuring and laying it all out ahead of time, but had to redo it by the above manner anyway. Even the height of some standoffs was different than what I calculated. Do the left side first as the cargo door side is too complex to build first. Do the left, than build the cargo door to match. PS don't forget that the Spruce stringers are shorter than Bob's, so the last saddle will reguire a tube under it. Another do-over for me. Pat Fagan #232 Pearblossom CA +++ #8285 From: "Bruce A. Frank" Subject: Re: Stringers and such... > I'm getting close to installing stringers on #164. I don't know how things might differ from my project, but I just ran strings down the fuselage starting from the high points aft of the doors to the tail. Then I welded my standoffs to touch the string. I am using the same rectangular style aluminum "tube" for the stringers as you are. My standoffs come to a thin edge that actually slips inside the tube so my string line and the outside edge of the stringer tube are in the same position. The stringers in place have exactly the same contour as the string guide lines. I had to splice this tube in several places because my lengths were cut shorter than yours are. Two splice methods worked well. I went to Tap Plastics and found rectangular plastic that fit tightly inside the tube. I slid it into the ends, butted the aluminum together with about 1.5 inches of the plastic sticking down each stringer tube. I then drilled and pop riveted through the tube to hold the plastic in place. Another method also worked well, but was more time consuming. I slightly crimped the sides of the end of one of the stringer tubes and slid it inside the other... like one soda straw inside the other. Made sure things were straight and pop riveted these also. Several pounds of weight suspended from the splice points showed no more deflection than a section of uncut tube so my methods appear to be solid. A piece of cloth tape over the joint makes it completely invisible under the doped fabric. Bruce A. Frank +++ #8291 From: Russ and Penny Erb Subject: RE: Stringers and such... Sounds like good ideas, Bruce. Differences I see: Sounds like your stringers are straight. Bearhawk stringers are curved. Like budd said, "T'ain't nothing straight on a Bearhawk fuselage". I think (haven't checked rigorously yet) that all Bearhawk stringers can be done in one piece from 12' stock. Erbman +++ #8293 From: Budd Davisson Subject: Re: Stringers and such... when we were laying out the hard tooling for the stringer standoffs we found that some of the dimensions in the plans don't work out exactly and don't necessarily flow into the firewall. The firewall leaves some area for interpretation so we did the firewall and door frames first, then pulled strings, holding them into position with external standoffs, sort of like bulkhead frames OUTSIDE of the stringer lines. Once we got what we thought was a pleasing, continuous line, nose to tail, we took measurements and built steel fixtures. If any of the dimensions exactly matched what was on the plans, it was purely coincidental. Pat and others have probably done it already, but I'd advice getting your stringer lines set before you do your door jams, then make the jams to fit the stringer lines. Do the right side first and then duplicte on the left because if you do it on the left side, it's hard to make the right side match. At least that's what we found. It's an eye thang so just make it look good to you. bd +++ #8307 From: "Bruce A. Frank" Subject: RE: Stringers and such... When I sent you that response I hadn't looked at the shape of the Bearhawk fuselage closely. Yes, I see that the sides are curved so my method isn't probably as useful. But, after looking, why can't you just clamp the stringers to the fuselage front and rear and mark location on the vertical tubes at which to weld horizontal tabs for attaching the stringer? Bruce +++ #8819 From: "Collin Campbell" Subject: Mouse Doors I am at the stage of making doors for my project now. The idea of the little "mouse doors" (glad we now have a new name for them) has bothered me for some time. I didn't want to try swinging the doors from the top (seaplane style) since I think opening the top half is rather cool. I like the way the doors on the Maule is set up. It has a similar door arrangement, but the front door hinge axis is sort of slanted. In other words the lower hinge is farther aft, allowing the door to sort of swing out and down at the same time. This allows it to swing open further before hitting the strut. This means giving up 6-8 inches of opening at the lower front of the door. Would have to close off a small triangle at the front of the door with a bulkhead to hinge the door on. This is not a problem in the Maule that I fly, it is hard to swing your feet that far forward anyway, due to the strut. I plan on making my seats so they will slide a little farther back than normal to make entry easier. I talked to "The Bob" about this when I met him at Oshkosh in 2000, and he said that might be a good solution. The Aeronca Champ, Citabria etc have doors that hinge in this fashion. Anyway, this is what I am going to experiment with in the next few days. Any thoughts? Collin Campbell #370 +++ #8820 From: pfflyerz@c Subject: Re: Mouse Doors > The idea of the little "mouse doors" (glad we now have a new > name for them) has bothered me for some time. I kind of like the "mouse doors". They are unique and ingeniously solve a problem. Having made mine I don't really see a disadvantage to them, other than the extra work in creating the cut out in the lower door frame. When shut the mouse door seals as if it was all one piece. Pat Fagan, racking up the hours building engine baffles, #232 +++ #8831 From: "Collin Campbell" Subject: Mouse doors again > If the Lower hinge were further Forward, the door would swing > UP when going forward... I've been experimenting with the door idea for some time now. You really need a fuselage complete with the door posts, sills etc. to be able to visualize how things work. I have made a "temporary" door from cardboard to play around with. To get the door to clear the strut, one would have to move the lower hinge almost halfway to the firewall. This has many problems it would seem to me. No good place to attach the hinge, rear of the door would hit the wing long before it would fold flat against the cowl. (Actually it would hit the upper half of the door, which would be held open against the wing). As for the piano hinge idea, forget it. Piano hinges only work if the hinge is nice and straight. The front door post is curved on the Bearhawk. To change that would not look as nice to me personally. Collin Campbell #370 +++ #8834 From: John Dougherty Subject: Re: Mouse doors again > I've been experimenting with the door idea for some time now. I discussed this with Bob and he suggested moving the lower strut attachment forward would give door clearance, but would require some reworking of the cable pulleys to alow free movement up the strut....John +++ #8842 From: pfflyerz@c... Subject: Re: Re: Mouse Doors A little know fact is that "the Bob" experimented with a tilting lower door on Proto 1. I can't visualize how he did it now, but the upper hinge allowed the door to pivot, raising the back of the door. Mike said they did it to allow the door to open wider for loading engines. I don't know if Bob left that feature off Proto 2 because it wasn't worthwhile or if it just wasn't needed since he already had the cargo doors. Pat Fagan #232 Pearblossom CA +++ #8844 From: Russ and Penny Erb Subject: RE: Re: Mouse Doors This is documented on the BHCD on "Prototype Fuselage Photos Page 2". The lower hinge was in a slot that could be slid rearward so that the rear of the door would be raised up. Mike Meador told me that this was an attempt to get the door to clear the strut. Then again, the strut on Proto I was originally on the forward landing gear attach point instead of the rear. Perhaps when he moved the strut back (for whatever reason), that hinge set up didn't work anymore, hence the invention of the mouse doors, and the plans were changed. Proto II has the door hinges as shown in the newsletters. Russ Erb +++ #9003 From: "Forrest Ferdon" Subject: Tri-Pacer Parts Brought home a Tri-Pacer "Treasure" (a term my wife uses loosely) yesturday. It is a wrecked fuselage with good seats, battery box, overhead trim, good interior, and miscellaneous small parts. I plan on stripping the parts that can be put in to Bearhawk service and get rid of the rest. Anyone need a Tri-Pacer data plate with complete logs back to 1953? How about doors, cowling, trim pieces, or an interior? Let me know. Forrest "spent my spar strap money" Ferdon +++ #9004 From: "Bruce A. Frank" Subject: Re: Tri-Pacer Parts At the chance that I might rub someone the wrong way I am going to say 'again' take a hard look at the fuselage. If you have not built your fuselage yet, the Tripacer, with minor modification, can be converted to nearly the exact conformation of the Bearhawk. PA20, PA22, PA14,....Maule....2+2 Sportsman...Alaskan Bushmaster are all very similar and fall in to a fast build kit arena by taking the salvaged fuselage and making some measured cuts. Then welding it back together. Such a course of action can save years, particularly when it gets down to the detail of pulley and cable guide placement, flanges and nut plates, gear mount points and window frames. Even a fuselage frame that requires a fair amount of repair can be a much faster course that starting with a pile of tube on the floor. Now I know every last one of you is in this for the joy of construction and the fact that you may eventually get to fly it is just icing on the cake. Right? If you don't want to build for nine years of weekends then a salvaged fuselage may be a viable alternative....if you just look at it from the right perspective...and squint a little bit. (grin) Bruce A. Frank +++ #9009 From: "t18cox" Subject: Re: Tri-Pacer Parts John Thorp used to say if you want to fly go buy a flying airplane. Scratch builders do it because they love/hate the process. If they get to fly it someday that is the icing on the cake. Most sucessful scratch builders spend their lives building and restoring stuff. Rods, houses, planes, boats, guns, etc. See yourself on that list? Bill Cox #303 >>> 4sep02 #9154-11297 +++ #9735 From: "Pat Fagan" pfflyerz@c... Subject: Re: Project report > Do any of you have any suggestions or ideas about skylights? I have incorporated a sky light in my Bearhawk and am happy with the way it has turned out. Now that the fuselage is covered it is easy to visualize what it looks like. I will try and get a picture put on the group site in the near future. If you are interested, Collin, I can send you details. +++ #9764 From: "Pat Fagan" pfflyerz@c... Subject: Re: Digest Number 769 I am painting the interior color today. I will take a picture once that is done, but I am still in the film era, so when that film will get developed is anyone's guess. To tide you over, I will try to explain what I have done. My skylight spans the full width of the cockpit but it only comes back as far the as the mid point between the spars. That is sufficient to allow the pilot to look straight up. Putting it back to the rear spar would cause a funky roof line since the wing starts to drop away from that point and would require bending the window. I struggled with what to do with the "hump" until I finally realized that the hump is there to allow room for the large trim wheel Bob used. I redesigned the trim to use a lever actuator which allows the window to span across with the contour of the wing. I have a console built around the trim mechanism ti hide it. It is about 6 inches wide. It blocks some of your view, but it provides another attach point for the window. To box the area for the skylight I added two tubes, running spanwise, to the center of the X member. To this tube I skip welded an almost 3" tall "wall" , from longeron to longeron, which serves as the back wall of the box. This wall has a channel at the top for the rear of the window to slide into. The contours along the sides were built just like Bob's, but I added a lip to each of them for the window to also slide into. At the front, I built the windshield attach channel like Bob pictured, but added another strip to the top of it, with nut plates, for attaching the front of the skylight. The skylight "should" install by sliding it into the side channels and back into the rear channel. I will then screw down a strip at the front which overlaps the skylight and the windshield and spans between the longerons. There will also be another longitudinal strip overlying the trim console box which should prevent any aerodynamic bulging in the center. One unexpected advantage of this design is I get full view of my sight gauges. I didn't realize it until I mocked the design up, but the fuel in Bob's gauges won't become apparent until 1/2 to 1/3 tank remaining because the rest of the gauge is hidden by the ceiling. This all may or may not make much sense to you, but hang on to it and I am sure when I get a picture posted it will be clear. +++ #9765 From: Budd Davisson Subject: Re: Digest Number 769 It's all clear to me and it sounds like a logical approach. Also, since the trim wheel moves such a small distance, the lever makes sense. Make sure your pictures show that too. +++ #10505 From: "rodsmith52" Subject: Fuselage Milestone I now have my entire fuselage frame tacked together, 135 separate tubes if I counted right. 109#s weighed by the questionable method of picking it up while standing on the bathroom scales. I believe you posted the weight of yours at the same stage Russ, do you remember what it was? I reinforced a couple areas, notably the tail for installation of a round tail wheel spring. I highly recommend Russ'es instructions for bending the upper and lower sections of the frame and jigging them together. Worked like a charm and I was able to do it by myself. As Bob suggested in the newsletter, I prefabricated the firewall and section C-S. I believe that was much easier than piecing them together in place. Time to get a rotisserie(sp?) built for final welding the clusters. +++ #10510 From: Russ and Penny Erb Subject: RE: Fuselage Milestone > 109#s weighed by the questionable method of picking it up while > standing on the bathroom scales. 113 pounds, but I weighed mine after finish welding. +++ #10885 From: Budd Davisson Subject: Re: Fuselages Available WE HAVE A COUPLE OF FUSELAGES AVAILABLE! When we brought our first load of kits in last week we had a little extra space in the truck so we tossed in an extra Quick-Build fuselage (complete, w/tail, control system, landing gear, doors, etc, just about ready to cover, $11,750) and a Basic fuselage (welded basic cage w/only wing/landing gear/tail fittings jig-welded in place, $5,650). These are available for inspection in Austin, Texas and ready for immediate delivery. If you're interested, get back to me off line. >>> 20may03 #11298-18250 #12232 From: Russ and Penny Erb Subject: Straightening Steel Tube Structures Here's an idea that I'm surprised is not on Kent White's 4130 videos (I'm tired of your excuses--just buy them!) This comes about in response to a large straightening project I just did on the "X" between fuselage stations D and E. When I welded these tubes in, the tubes deformed ("bent" for Planter Bob) upward into the fuselage interior about 1/2 inch. While this was not a problem structurally, it was going to be a problem when I tried to lay the aluminum sheet floor over it. Therefore I decided I needed to do something about it. Numerous places have talked about straightening a tube by heating one side and letting that side shrink, thus straightening the tube. For reasons I don't fully understand yet, but I think it has to do with how restrained the joint is, that doesn't always work for me. In that case, I add a little more "motivation" to the joint to straighten. There is at least one example of this technique on the Bearhawk CD V3. The idea is to set up the offending part with a pre-load (usually some sort of weight) that will try to straighten or bend the part. The key to this process is not only to have a weight to move the part, but also a stop in place that will stop the part from bending when it gets to the proper shape. The bending is then accomplished by heating the locations where the bending needs to occur. When that location gets hot, its capability to handle the load is greatly reduced, allowing the part to bend to the proper shape. The stop is critical, because otherwise there would be no way to prevent over-bending. The good part is that when doing this there is no noticeable springback. The same basic idea is described on the CD for making some of the bends in the top fuselage frame. More ideas for you when you're looking at that part that didn't come out quite the way you had intended. Russ Erb +++ #12233 From: bcgh@a... Subject: re: Straightening Steel Tube Structures >> The idea is to set up the offending part with a pre-load >> (usually some sort of weight) that will try to straighten >> or bend the part. I've also heard of using a 'come-along' to pull parts or whole frames into alignment. Probably requires more hands than pre-setting weight and stops, but also works in other directions than just down. Benton 24oct02 +++ #12234 From: Budd Davisson Subject: Re: re: Straightening Steel Tube Structures C-clamps and angle iron bd +++ #12235 From: Jimmy Mathis Subject: Re: Straightening Steel Tube Structures Try heating one side and then using a water mist spray bottle. ever so slightly mist the hot area to get the desired result. Jimmy +++ #12237 From: "Bruce A. Frank" Subject: Re: Straightening Steel Tube Structures > Try heating one side and then using a water mist spray bottle. ever > so slightly mist the hot area to get the desired result. This is an excellent method for mild steel. It is not a method that should be used on 4130. Chilling 4130 from a red heat, the softening point, with a water spritz can cause cracking. If it doesn't crack at that moment hardness created can lead to eventual cracking. The 4130 alloy is forgiving, but any chilling with water can cause brittleness approaching that of glass (much stronger than glass but brittle). Reshape 4130 by heating to red heat and moving with weights, clamps, block & tackle, pry bars, or jacks, but not with differential cooling....particularly with water. Bruce A. Frank +++ #12239 From: "Kent White" Subject: RE: Straightening Steel Tube Structures Hmmmm... Straightening bent or lumpy welded joints: "Warm and whack." Warm to dull red (dark room) and smack with 16oz ball pein, taking care to cover area with flat piece of plate to scatter force and prevent denting nice round tubes. Also, you can push/nudge/squeeze/press with C clamp, heat, and piece of plate. Thanks Russ....and BTW...we offer a WW2 Aircraft Tubing Repair training film with the 4130 films, as a special set. Russ...I will forward one to you. Kent +++ #12241 From: Budd Davisson Subject: Re: Straightening Steel Tube Structures An addendum to chilling 4130: I build a lot of rifle stocks from scratch and am always needing thin, sharp chisels for small areas. I make them from 4130 .065, heated dull red and quenched. They are so hard they can be stoned but not filed and the edges are brittle and need to be shaped and used with care. bd +++ #12340 From: Russ and Penny Erb Subject: We make the mistakes so you don't have to... All right, Bearhawkers! Quiet down and listen up! (or is that Quiet up and listen down!?) Go drag out your plans, especially sheets 17 and 28. Do it now...I'll wait... ...Hmm...how can we pull Planter Bob's chain...hmm...use the black iron oxide under the belt sander as fertilizer...hmmm... Oh! You're back! Look at drawing 17. Specifically the T11 tube on the centerline of the fuselage bottom between "B" and "C". Now look at drawing 28. Said T11 tube is the tube that the flap handle is attached to. Note the T4 tube passing through said T11 tube. This is the one with the bolt that holds the bottom of the 1/8" aluminum sector with the notches to keep the flap handle in one of the detents. Now let's go back to drawing 17. Note the two diagonal T11 tubes next to the subject centerline tube. Now try to project yourself into the future when you have a complete fuselage frame done and you are trying to drill the holes to insert the T4 tube. Can you see how those diagonal tubes might be a little in the way of getting the drill in there? It's very obvious when it is actually staring you in the face, as it was earlier tonight! There are at least three options around this problem: 1. Drill progressively larger holes at angles around the diagonals from both sides, go at it with a round file for a while, and exercise that concept that the fit doesn't have to be real tight when you're welding (what I did successfully, but don't recommend) 2. Find a short 3/8" drill bit for your right angle drill (big buck$, assuming you can find one) 3. Make a note on drawing 17 RIGHT NOW(!) to drill the holes for the T4 tube BEFORE tacking the diagonal tubes in place. (HIGHLY recommended) It's your option whether you want to weld in the T4 tube at this point. You can do it now or wait until you're putting in the flap handle. These little integration issues aren't obvious just looking at the plans, but become painfully obvious when you've done things in less than optimal order. Remember--you should learn from other's mistakes, because you won't have time to make them all yourself! We now return you to your normal Bearhawking duties... Russ Erb +++ #12359 From: "rodsmith52" Subject: Re: We make the mistakes so you don't have to... You will save a lot of people grief with this post Russ. I pre installed bushings through tubes everywhere I saw them on the plans. It wasn't because I was smart enough to foresee conflicts like this, but simple lack of skill in drilling centered holes through tubing. I try to do all of that with the tube securely anchored in my drill press. Then the challenge becomes getting the tube you have already welded a bushing into properly fitted with the hole in the right place and orientation(ie horizontal or vertical as the case may be, not at some random angle). I mentioned awhile back that I modified the rear spar carrythrough for two shoulder harness attach points. I milled slots into the tube into which I slid the fittings and welded the fittings top and bottom before fitting the tube into the frame. I have found that I end up doing a much neater job working on small parts than when they are attached to the whole frame. Rod Smith #246 +++ #12889 From: Russ and Penny Erb Subject: Something else not obvious in the plans... Been working on doors. Today I was hanging the rear cargo door. I've been building the doors on the fuselage frame leaving a 1/8" gap per Bear-Tracks. Of course, after welding shrinkage, they end up slightly smaller, but that's not the issue here. In fact, it actually helped. For all of the doors except the rear cargo door, the structure between the hinges is straight. Because of the shape of the fuselage, the structure between the rear cargo door hinges bends out away from the hinge line, which can lead to interference when opening the door. Of course, I figured this out in my standard way, namely after welding the hinges on and the door would only open about 20 degrees. My solution was to cut the hinges off and weld new ones on with about a 1/4" gap at the back of the door. Getting the skin to work will be another interesting problem. Another possible solution would be to move the hinge line farther away from the fuselage. The point here is you should check how this door is going to operate before you start welding the hinges in place. Russ Erb +++ #13401 From: Russ and Penny Erb Subject: Bending Square Tubing? (Note: This message certified on-topic and computer/camera free) To Pat Fagan--in May 2001 you wrote the following: "For those of you looking over the tubing required, I would recommend that you add 10 to 12 feet of 1/2 X .035 4130 SQUARE tubing. I had been experimenting with making the wing contours that go above the upper longerons with the 1/2 inch channels as per plans, without much success. I noticed in Mike's fuselage photos that Proto 2 used what looked like square tubing for the uprights that support the contours. I bought enough to try making the wing contours, as well as for the uprights. The contours came out very nicely with this material. They bent easily and provided four sides to weld the uprights to. 10 feet would be enough to do all you need to do, but 12 feet gives you a little extra leverage for bending. " Based on your recommendation, I procured said tubing. But before I try using it, I have a question: Did you bend the square tubing in the same fashion that you bent round tubing? It seems to me that square tubing might bend differently (more buckling on the compression side) than round tubing. Then again, perhaps the bends are small enough not to matter. Bonus question: How did you handle the sharp bends at the leading edge? I could answer this simply by trying it, but I thought I'd ask before possibly making a length of expensive tubing unusable. Of course, anyone else with experience in this area should feel free to respond. Russ Erb +++ #13403 From: Budd Davisson Subject: Re: square tubing I think this is an excellent approach but rather than spending all the bucks for 4130, why not use mild steel tubing. It's commonly used in security grates, most steel yards have it and it is dirt cheap. Since it's square, not a channel, it'll be just as stiff as 4130 but a little heavier. There are two types, some measure 1/2 ID and some 1/2 OD. bd +++ #13404 From: "Bruce A. Frank" Subject: Re: Bending Square Tubing? I don't know the exact part you are talking about but I can make some suggestions about bending square tube. Square tube flattens slightly when it is bent. If the radius is not too great (such as the curve of the airfoil) there is no noticeable change in the dimensions and .035 wall will work just fine. If you want to bend a sharper radius like the shape of a leading edge the tube will flatten, bulge on the sides a bit and sink down in the center assuming a slight hour-glass shape. You can make a bending mandrel that has a channel into which the square tube fits; a form against which you work the bend. I have used flat washers on a large diameter bolt or welded in place on a piece of tube. Set the width just slightly wider than the tube diameter and lubricate it with oil. As you bend it, the square tube gets wider. The washer groove form helps the tube hold dimension, but it will still flatten and sink in on the outside of the radius. Ripples will also develop on the inside of the radius. If you can use a piece of solid round rod and a hammer to actually help create a uniform depression on both the inside and out side of the radius; making it uniform as possible, you can create a very smooth bend with much less distortion of the sidewalls. That is, they will stay more parallel. On sections of tube where short radius bends were required where full dimension uniformity was needed we, at my previous job, would cut flat strips and arcs out of flat metal and by welding together to create uniform curved sections of square tube. Weld up all four corners then file and sand to look like a die formed piece. You may find that careful bending of the square tube will give you what you want, just be aware that it might not. If you do not use a bending form to hold the sides parallel in a tight radius and plenty of pressure to hold the tube in the groove it will kink. Hope this helps and doesn't turn you off of the idea. Heating can help a little bit, but you will still need the sided form to hold shape and will really have to take your time. Bruce A. Frank +++ #13405 From: "Bruce A. Frank" Subject: Re: Re: square tubing Budd's suggestion is dead on. Mild steel will be less resistant to bending; will stretch and a thicker wall (.065") will actually not distort as much....giving more thickness to flow. Heating methods will also work better on the thicker material. Bruce A. Frank +++ #13407 From: Joel Mayhall Subject: Re: Bending Square Tubing? Prepacking round tubing with sand before bending works quite well, however I have not tried to bend square tubing with this method. Joel +++ #13408 From: "rodsmith52" Subject: Re: Bending Square Tubing? Great info Bruce, thanks. I guess the advantage to sticking with 4130 would be to keep the extra ounces which rapidly become extra pounds off the airplane. I used a brake to make 1/2" channel from .035 steel for those parts. Have not attempted bending it to airfoil shape yet. Rod Smith #246 +++ #13425 From: pfflyerz@c... Subject: Re: Bending Square Tubing? > Did you bend the square tubing in the same fashion that you bent > round tubing? The bend is such a gentle radius, I bent it just like I bent the longerons on the fuselage, slideing the tube under the table legs while pulling upward. the leading edge was made the basicly the same way you made your rear window frames. I made a channel, then notched the legs, made the bends, then rewelded the notches. I survived my EAA inspection on Friday. That was quite an intense experience. Nothing major, but lots of little things to take care of. FAA inspection is scheduled for the 13, just a week away now. Pat Fagan N232PF Pearblossom, CA +++ #13437 From: "t18cox" Subject: Re: Bending Square Tubing? I've been curious, why not use a 3/8 round tube at the front. I think it's just for trim at the windshield cutout. Bill Cox #303 +++ #13444 From: "collinc2002" Subject: Re: Bending Square Tubing? For the leading edge treatment, I simply welded on a couple of tabs and fitted a piece of .025 aluminum to match the windshield. Attached with platenuts and screws. I can't see how this piece is serving any structural purpose such as support of the windshield, it is just a cover. I just finished installing the windshield and was glad I chose to do it this way. You really need to have the windshield on hand to see how everything fits. There were some slight irregularities in the shape of the windshield that wouldn't have fit properly if I had simply deducted the 3/16" thickness from the airfoil shape. I think the simple cover is easier to make and weighs slightly less. Collin Campbell #370 +++ #13453 From: pfflyerz@c... Subject: Re: Re: Bending Square Tubing? > I've been curious, why not use a 3/8 round tube at the front. I > think it's just for trim at the windshield cutout. That's actually not a bad idea. You are running somewhat blind while fashioning that part as the wing may or may not be installed at the time. When I installed my windshield I had to grind away the upper, outer, edge of the C channel, as well as bend in the whole affair a little, to get a good fit with the windshield. The round tubing would not only be easier to form, the round cross section would help with the window fit. On another note, I spent a lot of time trying to get my flaps to come down at the same rate. The left flap always wanted to start down first. I finally decided the problem is because the flap cable is offset from the centerline, so the initial pull on the flap handle pulls the cables at the connecting link to center first, which causes tension to be placed on the left cable first. The solution turned out to be simple. Rather than install the triangular connecting link for the flap cables as it appears to be drawn in the plans, (which is to say symetrically, with the long side attached to the cable coming up from the floor) I turned it so the long side is attached to the left flap cable. This effectively offset the main cable to allow both flap cables to work at the same time. Arnold, what do you mean it looks like "a hands off show plane". I already put two holes in the belly fabric myself, what possible damage could you have done? Feel free to post your pics. Pat Fagan #232 Pearblossom CA +++ #14353 From: Russ and Penny Erb Subject: Didn't think that one all the way through... (I wouldn't have bothered with this except that Kent enjoys these stories so much...) I finally picked up a lock today to put between the cargo doors. I designed a simple bracket for it and fabricated such. I briefly thought about where I should locate the bracket on the front cargo door, but never once looked at the rear cargo door. After all, I knew what it looked like--there were no obstacles to worry about--I could mount the lock any where that didn't interfere with the door latch...(do you see the problem developing yet???) Got the bracket welded on--looking good. Installed the lock--looks great. Was about to walk away from it when I decided to mount the doors on the fuselage just for fun. Doors on the fuselage...close the rear cargo door...close the front cargo door... (Do you see it coming yet???) ...grabbed the keys...put the key in...gave it a turn...uh...make that a "half" turn...try it again...turn...KLUNK!!! What the heck? What's going on? There's nothing there to hit...nothing...I "know" there is nothing...time to investigate... AAAAUUUGH!!!! KRAP!!!! Yep, I had selected the one location for the lock that WOULDN'T work!! The lock bolt swung right into the handle for opening the rear cargo door! KRAP!!! Well, that's not going to work... As always, there is only one solution to this type of problem--cut it off and do it again--correctly this time. Thus I did thusly... As an interesting side note, while correcting this problem, the following thought came to me: "Have you ever wondered how good your welds are? Just wait until you have to cut your mistakes off..." Russ "Maybe I should have stayed in front of the computer" Erb +++ #15168 From: Russ and Penny Erb Subject: Pat was right/Fin Fillet I've been working on the channel on top of the fuselage that matches the wing contour. Although, instead of making a channel, I used a 1/2" square x .035 tube as Pat Fagan had suggested. I was a bit skeptical at first, but I found the square tubing to bend just as easily as the round stuff. The most surprising part was after I had gone the length of the tube putting in a slight bend, I put it up against the wing and it was a 98% perfect fit. I had to adjust one bend and it was ready. Point: The square tube works very well for this purpose. Special Bonus Tip: Concerning the T8 tube on the vertical fin that forms the fillet with the upper fuselage stringers. Turns out that a 3/4" EMT conduit bender is perfect for forming this piece. It has the right bend radius and the 5/8" tube just fits in the bender. Just bend the tube 60 degrees and you'll be golden. Those of you keeping track of this sort of thing will remember that I used the same conduit bender to bend the ground handling handles for the aft fuselage. Russ Erb +++ #15425 From: Russ and Penny Erb Subject: Can 0.3 inches make a difference? Yes, when that means that your longeron is 0.3 inches low and makes a 1/2 degree (or more) difference in wing incidence! Can you say a seriously heavy left wing? For some reason, I decided tonight to check the relative incidence angles of the wing fittings. They were about 1/2 a degree off. After much searching I could see that the tube at the rear spar was not parallel to the tube at the front spar. The low corner was (of course) one of the fittings that was finish welded. (As Kent would say, KRAP!) I determined that the frame at that point must have moved as a rectangle shifting toward a parallelogram (one diagonal slightly longer than the other), even though the front and tail of the upper frame were properly centered. Yes, a 0.3 inch error in the right place can make a major problem. So besides checking to make sure your fittings are square (so you don't add in wing sweep or something), also check the incidence for each wing. It is far more critical that they match than they match the plans. Solution? I'm remaking the fitting at the offending corner, shifting the hole up (and the surrounding material) by 0.3 inches. It will be covered up by a fairing, so y'all will never see it. As a special bonus, I'll get to shift the contour channel on top of the fuselage too! I sure hope I don't find any more problems in critical areas! As a side note, it seems to take as long to cut off a fitting as it does to weld it on. Russ "Whomped upside the head" Erb +++ #15427 From: "t18cox" Subject: Re: Can 0.3 inches make a difference? This sounds familar. After completing the welding of my fuselage and starting to fit the wing fittings I found the right front fitting location to be 1/8" lower that the left. I corrected it as you purpose to do. According to my Smartlevel my wings are at the same angle of incidence. I was also concerned about getting the distance between fittings correct, so I made a jig from a piece of bar stock with a copy of the spar butt fittings to hold things in position until I could get a few tacks in place. Everything went together nicely after the welding was complete. I fitted the wing to fuselage contour in place after the wing was fitted to the fuselage. Didn't trust myself to get it right otherwise. Bill Cox #303 +++ #15631 From: Budd Davisson Subject: Re: Corrosion Protection > I'm interested in a steel tube frame, but worried about internal > corrosion. With the BD-4 the alum angles can be completely primed, > but with tubes the inside must be coated with ?? linseed oil?? If > this correct how do you go about getting the oil into the tubes, and > the excess out? I'm quite clueless in this area, so any advice > would be helpful. Thanks! > > ...also is powder coating a good option for the exterior of the > tubes, or will it be too heavy and chip? The concept of oiling the inside of tubing is fraught with some controversy because very few factories ever did it. And there's a good reason for that. To rust the inside requires both oxygen AND moisture. If the tube is welded tight, there isn't enough of either for rust to damage the tubing. So, what if it has a pinhole in a weld? I personally have cut open structure that was half full of water, but it didn't even have scale on it. The rust that could be found was at the pinhole where it had started leaking and rust apparently quickly sealed the hole cutting off the oxygen. This particular structure was a 1955 Tripacer. At the same time, if someone wants to line-oil the longerons, that's a simple matter of drilling an 1/8" hole near one end (drilling both ends makes it easier) pumping oil in it, taping the hole shut while the structure is rotated enough to get the oil running around and then untaping it to let excess run out. Then a locked-spindle blind rivet (pop type rivet)is put in the hole or it's welded shut. That's it. No, sweat. Powercoating is okay if done by someone who understands the ramifications of doing it on 4130. The cleaning solvent they use after sandblasting absolutely has to be baked off of it for it to be a true moisture barrier and some operations don't take much care on that step. bd +++ #15740 From: Pat Fagan Subject: recommendations ... Second, for those building the cargo door option, don't make your gaps too tight. There is enough flex in the fuselage, at gross weight, that you could have a potential problem with binding at the top if they are too tight. I shot for 1/8 inch all around and don't have any problems, but I do need to enlarge the hole in the rear door for the latch pin in the front door. ... Pat Fagan +++ #16620 From: Russ and Penny Erb Subject: RE: Bearhawk Plans Viewer -- Big Update > Is it me or there is no detail on doors and engine mounts in the > drawings? Do we have any indications or skecth for these criticals > installations It's not you--they ain't there. The engine mount depends on your choice of engine. The doors are built to fit the hole in your fuselage. The only published information from The Bob on these topics is in the back issues of Bear Tracks (also included on the BHCD). As you might have guessed, this isn't a "Put tab A in slot B" type of project. Some of it you have to figure out on your own. Then again, that's why many of us are here on this list...or was it to keep current on the Planter Bob farm report?... Russ Erb +++ #17292 From: Russ and Penny Erb Subject: Open Cockpit Bearhawk? Well, I'm back in the "I hate my airplane" mode. These doors are a major pain in the a**. A Lt Col pain even. Recommendation: Don't make your doors, especially the cargo doors, until EVERYTHING on the fuselage has been welded. I was welding the tabs for the floor in place today, and the shrinkage of the lower longerons was sufficient to warp the door opening such that the doors moved 1/8 to 1/4 inch, such that they didn't line up any more. Now I'll wait until all of the @#$% stupid tabs are welded in before I try to fix the doors, because I'd just be wasting my time doing it now. There will be holes to be welded over and re-drilled. Ugh! Russ "How many more stupid tabs are there to go?" Erb +++ #17293 From: Budd Davisson Subject: Re: Open Cockpit Bearhawk? fyi- We did a little investigating to determine the most commonly available weather stripping and decided to leave1/2" gaps to leave space for the stripping, which also gives a fudge factor. We finish almost all the welding on the fuse and then build the doors. They aren't built in hard tooling for the very reason you point out: everything moves too much for there to be a one-size-fits-all-approach. Incidentally, if you measure it, there is very nearly enough tubing in the doors to build an S-1 Pitts fuselage. bd +++ #17626 From: dlshilling@g... Subject: Station S OK, I'm stuck. I am working on station S and the plans look funny to me. The cross tube that connects the lower door frames looks like it is built in 3 pieces. It says T11 on the outer segments and T19 in the middle. However, looking at Russ' CD, all the pictures look like it is just one tube, assumably T11. Help. I can't figure out what that T19 in the middle of the station S cross tube means. Dan Shilling +++ #17628 From: Russ and Penny Erb Subject: RE: Station S Do your plans look something like the attached figure? This is from the April 1997 Bear Tracks. Apparently the top tube was originally T17 (I'm not sure where you got T19). In this engineering notice, The Bob said that the top tube (the whole thing) could be changed to T11 to save a few ounces. Mine is a T-11 tube all of the way across. Russ Erb +++ #17629 From: dlshilling@g... Subject: Re: RE: Station S Yes Russ, except the T11s are not circled and the T17 in the middle is a T19. Also a center line is drawn vertically. Dan Shilling +++ #17630 From: Russ and Penny Erb Subject: RE: RE: Station S Might be time to call The Bob on this one. If he meant that the center tube was supposed to be thicker (T17 or T19), then I have a problem. Mine is T11 all the way across. Mike Meador--care to fill us in on this? budd, how did AviPro interpret this? Russ Erb +++ #17633 From: Budd Davisson Subject: Re: Station S Without looking at my plans, we took the heavier piece of tubing and ran it straight across. It's not three pieces. And I'm pretty sure it's T17, but I could be wrong. It's what ever the heavier of the two were. bd +++ #17637 From: rsmith@f... Subject: RE: Station S That wasn't how I interpreted the engineering notice. I thought you could substitute T11 just on the outer portions and the center needed to be T17. Otherwise, why would Bob have left the T17 designation on the drawing where it is? With the overlap of the splices I figured it would be easier and nearly as light to just leave the whole thing T17. I think we need a clarification from Bob. Rod Smith +++ #17667 From: Tom Marsh Subject: RE: Station S I checked my plans (#596) & they agree with Dan?s, T19 at the center. Drawing 18 is noted as revised 12/97. Tom +++ #17810 From: Dan Shilling Subject: T19 Tubing Order I am getting close to finish tacking my fuselage together. I made my steel order according to The one Rod Smith worked out and is posted on Dell's site. So far the amounts are great. There is one exception which is probably due to the plans change on Station S using T19 instead of T17. I would advise anyone making an order based on plans since December 1997 to buy 7 feet of T19 instead of 6 feet. As luck would have it, I had just exactly the right amount by being extra careful making my cuts. An extra foot would have given me some breathing room. Dell, you might want to make the change on your site since you otter be done with finals by now. How did you do? Dan Shilling +++ #18141 From: Russ and Penny Erb Subject: I come to praise Dan Shilling, not to bury him... I'd consider burying him for the amount of work he created for me, or at least pointed out that I had created for myself, but considering the possibly ugly landing incident he saved me from, I'll have to praise him. About 12 days ago Dan asked a good but seemingly innocent question about the tubing sizes at Station S. Originally, it was T17 all of the way across. Then The Bob issued an Engineering Notice changing the outside thirds to T11 (optional), but leaving the center at T17. Later the center section was changed to T19. Unfortunately, I had misinterpreted the Engineering Notice to mean T11 all of the way across. Since the discussion quickly showed me to be in the minority, I thought I should probably check with the top authority--The Bob. I sent The Bob a letter with pictures of what I had built along with a proposed fix of lesser workload. On 6 May, I had a chance to look at Ron Wilcox's plans (about #647) and the tubing size callouts were as Dan had said. Today I got the letter back from The Bob. He rejected my suggestion and told me to cut out the center section of the T11 tube and replace it with a T19 tube. Ugh! (This reminds me of a quotation I think I heard once--something like "Sometimes you beat the bear, and sometimes the bear wins." Can anyone give me the correct quote and a reference?) Well, a Bearhawkers gotta do what a Bearhawkers gotta do. Hence, #164 is currently under the knife...er...rotary tool for some major surgery. I'm working on fitting the new tube now, but had to stop when the rotary tool suddenly decided to take a permanent vacation. It's the second such tool (aka Dremel Moto-Tool) that I've had on this airplane, and has probably lasted about 3 years. Not too bad when you consider that using cutting wheels to cut steel is hard work for it, and probably at the top end of its design capability if not beyond. How many Moto-Tools does it take to build a Bearhawk? What's the big deal? Why the large tube here? Well, The Bob confirmed my suspicions. In flight, this tube is virtually unloaded. However, on landing, as the gear struts are expanding (pulling on the bottom of the fuselage), the design of the truss is such that this center section is in compression, and needs to be the heavier tube to give strength against buckling. The outer sections are in tension, hence the T11 tube is adequate. For those of you not there yet, my recommendation would be to use the T19 tube all of the way across and eat the few ounces of extra weight. That will make for a much simpler joint. I believe budd has said this is the way the kit fuselages are being built. Of course, I used the heavier tube for the horizontal stab leading edge too. It's always something, and in this case, hopefully that inevitable hard landing won't result in a seriously messed up fuselage at Station S. Russ Erb +++ $Id: 2.3.1-Fuse-Truss,v 1.14 2003/05/22 03:20:54 bentonh Exp $