+++ #127 Subject: Plans Questions From: Rod Smith On drawing 20 I had not closely looked at the tube sizes. I thought that a larger tube slid over the front horiz stab tube and was welded to it. Now I realize it is two 7/8" tubes of different thicknesses butt spliced together. Is this the intent? For slightly less than 1 pound extra weight, I will make the entire tube out of the .049 material. This will have the added advantage of being more resistant to rock strikes. I had some nasty dings to patch there on the Maule that I rebuilt. Drawing 16 shows the airfoil shaped trim made out of 1/2 by 1/2 .032 channel, I am wondering what method you use to get a smooth bend around the nose of the airfoil? +++ # 128 Subject: Plans Questions From: Russ Erb >On drawing 20... I assume you're talking about the forward root attach point on the horizontal tail. I looked at this and couldn't find a reason for it either. I'm guessing the thicker .049 tube (T14) is used to better support the bolt, although the thickness for a "perfect" fit with the tube it slides over (3/4" diameter) would be 0.062. Of course, I've noticed tubing thickness can vary by several thousandths. I think we'll need Mike Meador to get an answer from Bob on this one for us. Normally I'm against adding weight unless it adds capability. Usually the tail is the worst place to add weight because of it's large moment arm. If it requires ballast in the nose it's bad all around. However, most of us will probably be using larger engines and are already thinking about moving the battery aft of the cabin to compensate, so this little bit of weight that Rod suggests may actually help. Rod makes a good point about this being a primary rock strike zone. > Drawing 16 shows the airfoil shaped trim made out of 1/2 by 1/2 .032 > channel... Again, I'm guessing you mean the part of the fuselage right next to the wing leading edge. Looks like some heavy duty work on a metal shrinker to me. +++ #134 Subject: Re: Plans Questions From: Mike Meador In reference to Rod Smith's question about the 7/8 tubing etc. I ran the e-mail past Bob and he said that the splices are intended that way to save weight and that they are plenty strong enough for "normal" abuse and wear - now to define what you think is "normal" would take more typing than I am prepared to do! Bumping it up to .049 is O.K. - BUT you are adding weight just about as far back as you can go - no matter if you are installing a starter and a power system. There are other ways to protect the tube in an other than "normal" environment - one of note was a bicycle inner tube split open and glued to the L.E. of the horz. stab - this was used on a lot of airplanes in Alaska and was reported to be quite effective at a very small weight penalty (looks tough and butches up the airplane too). +++ #399 Subject: Tail Wire Links From: Rodney Smith I'm apparently stuck on page 21 of the plans tonight. Do not bend all 6 tail wire links like the diagram on the plans. You should end up with 3 sets of two each bent to different angles. Look at the head on view of the plane on page 1. You will see that the tail wires intersect the horiz stabilizer at different angles on the top and on the bottom of the horizontal stabilizers. The sharpest bend is for the ones at the top rudder hinge and is as shown on the plans. +++ #514 Subject: Bending Tubing From: Rod Smith The other night I got to the point on the tailfeathers where I couldn't avoid doing the tubing bending any longer. This turned out to be a surprisingly easy task. I had access to a powered conduit bender with bending forms of several diameters from 12 to 18 inches. I didn't plug it in, just used the forms to bend by hand. With just a little practise it was easy to figure which form to use to get a given radius. Some pointers. As I expected, you want to start out with extra material at each end, both to use for leverage and to be able to slide back and forth if your bend is just a bit off. For instance, an 8' piece worked great to make the 80" piece on the back of the rudder. I found the very gentle curves to be trickier. You need to mark the tube off in even increments, say 1/2" and make a very slight bend then move to the next mark etc. I found that you needed to deflect the tube just to the point where you could feel it yield and then move to the next mark etc. for the very gentle bends. If you bend too much in one spot you can straighten it a little but it is better to bend too little initially and go back over it if necessary. I made the back edge of the elevators and trim tabs in one piece to get one continuous curve and then cut out the trim tabs. By the time I got to the back side of the rudder I was wishing I had a larger radius to make the continuous gentle curve. Then it hit me. All I had to do was walk out in the plant to have a whole range of available diameters. I enlisted the aid of a co worker and we used a 60" diameter pipe to form it on (There's a couple miles of it in the plant) . Came out just about perfect. The 6 inch radius block Bob recommends will work fine using the bend a little and move it technique, but use your imagination and look around to see what you have available. I just watched a video today where a couple EAA Techs were using the bottom of a garbage can as their form (more about that later). One caveat. You need to bend the tubing and keep checking it against the layout until you can lay it alongside it and it is the correct shape. Do not just get it close and then pin it into the form. If you do that when you weld it up you will not have smooth bends, it will end up looking more like a stop sign. +++ #1390 Subject: 023 Update From: William & Delinda Johnson Well, after 5 days of non-stop full time work on the bearhawk, my stabilizers are installed. One elevator is 80% finished (need to complete trim tab) and the other is in the jig. Lots of lessons learned; however, if I have gained wisdom it is go slow and watch for bending of surfaces as you weld. I am convinced welding is more art than science. I finally got the right touch by welding a couple areas, put back in jig, fix any bending, and repeat process. The stabilizer scarf joints need to be done very accurately. Weld the trim tab attach hinges BEFORE welding the tubes to the elevator. Makes drilling to clean out misalignment much easier. Bending the T13 is lots of fun - eat your wheaties. Make sure all surfaces are properly aligned BEFORE drilling any attachment holes in the fuselage stabilizer attachment brackets. Probably lots more I could pass along but fatigue is setting in. I need to sleep. Watch my web site for detailed pictures (some have already been added). Press your browser refresh button to make sure you get the latest pages. I am limited to 100mb transfer per month so it may stop working from time to time (it is a free service from my ISP so I live with the restrictions). +++ #1400 Subject: Re: 023 Update-comments From: Rod Smith > Lots of lessons learned; however, if I have gained wisdom it is go > slow and watch for bending of surfaces as you weld. I am convinced > welding is more art than science. I finally got the right touch by > welding a couple areas, put back in jig, fix any bending, and repeat > process. Isn't it fun when you get one area straightened out, do some more welding and it moves again. > The stabilizer scarf joints need to be done very accurately. I solved that problem by using the .049 tubing for the entire leading edge for better rock protection with Bob's blessing. Costs you 1 lb and with a heavy engine and prop that is the best place to put it. > Weld the trim tab attach hinges BEFORE welding the tubes to the > elevator. Makes drilling to clean out misalignment much easier. I agree entirely. You really need to think ahead. Weld anything where alignment is critical first. > Bending the T13 is lots of fun - eat your wheaties. I got to bend T14 instead and I didn't think it was bad at all. The key is to start out with a long enough piece to give you a good lever. For the first one I left about 30" extra and as I got toward the end I was putting just about all my 155#s into it, not good for precise control. The other side I left 4'extra and it was a snap. > Make sure all surfaces are properly aligned BEFORE drilling any > attachment holes in the fuselage stabilizer attachment brackets. Hmmm. I may have screwed up here. I went ahead and cut the cross tubes for the front and rear stab attach and have everything match drilled while layed out on the shop floor. I figured I would build the fuselage and get it all aligned, then install those tubes last making sure they are installed square and everything would fall into place. The tail sure is impressive when all layed out with the elevators attached! Thanks for all the good info Bill! +++ #1401 Subject: Re: 023 Update-comments From: William & Delinda Johnson As a follow-up (now that I am well rested), I added an additional T1 tube between the most outboard rear elevator rib and the T3 trailing edge (centered in the middle of the bend) to keep fabric cover distortions to a minimum. Look closely at Mike's pictures. Bob did the same thing . . . +++ #1551 Subject: Flying Wires From: William & Delinda Johnson Wow, I just got an estimate. Spruce & Specialty will be calling with the actual price; however, for a streamline wire with fittings price is about $180 PER WIRE! Lead time is 8 to 12 weeks. I asked for a quote for one set of four (2 at 44.375 and 2 37.875 pin center to pin center). I also asked for a quote for 100 sets and 200 sets. Will someone please double check those numbers . . . Will let you know what I find out. Anyone have other ideas on how to lower cost? Other sources? +++ #1553 Subject: Re: Flying Wires From: Bob Marek Bill I checked mine flying wires, the lenghts you gave are with in a few thousand's of mine. +++ #1554 Subject: Re: Flying Wires From: budd davisson Just for the record: every flying wire in the world comes from Bruntuns and their importer in the US is Steen Aero Lab in Marion, NC. Call Hale Wallace there , 828/652-7382. He's not feeling well and may eventually sell the business, so I'd get my wires in the pipeline as soon as I could. +++ #1556 Subject: Re: Flying Wires From: William & Delinda Johnson Bob, what did you pay for the wires? Did you buy from Spruce? Thanks for checking the lengths! +++ #1557 Subject: Re: Flying Wires From: budd davisson Get ahold of Steen Aerolab and hit them with a group purchase. If they get an indication of activity, they may even be willing to inventory some for builders who'll need them in the future. Of course, there's always the alternative: threading 4130 rod. +++ #1563 Subject: Flying wires From: Bob Marek Made my flying wires same as detailed on the plans. +++ #1566 Subject: Re: Flying wires From: William & Delinda Johnson > What sheet number has the wire plans on it, so I don't have scrounge > through them all. Budd, sheet 21. I did not realize we could make the darn things out of 4130 solid round. Is that what you did Bob? +++ #1567 Subject: Re: Flying wires From: budd davisson Without looking at the plans, I'd have no compunction making wires out of rod. If I could keep them aligned, I'd even be tempted to streamline them with something on the trailing edge that has a little flex to it. Maybe profile a heavy bead of silicone and run some tape over it? A round wire has a terrific amount of drag and streamlining the back side would cut the drag by close to 70%. I think it's the Model 12 Pitts guys who use an extruded plastic (probably polypropylene) fairing on the back of the gear legs and it's just glued on. Keeping it aligned into the wind, however would be critical. Pitts wires really sing, if you get them sideways to the wind and I've always been afraid to look back and see how badly they're vibrating as it would scare the whatever out of me. Just thinking out loud. +++ #1568 Subject: Re: Flying Wires From: Todd Chisum That's why I decided NOT to build a bi-plane. Can round wire be used in its place? I know a fellow who built a Hatz and used cable instead of $4K worth of streamlined flying wire. From what I have found, there is only one place in the world that MAKES streamlined wires, they are in Scotland, is this correct?? +++ #1570 Subject: Re: Flying Wires From: Russ Erb I assume that we're talking about the wires on rear spar of the horizontal tail. The forward strut on the tail is a tube (compression and tension). My impression was that these wires were 1/4" rod (4130 I assume) threaded for fittings. It doesn't seem to me that streamline flying wires would reduce drag enough at this location to justify their price, and I don't think they would be any where near as highly stressed as flying/landing wires on a typical biplane. Am I missing anything here? +++ #1571 Subject: Re: Flying Wires From: budd davisson Re: round tailwires The round wires would generate enough drag that their effect on cruise speed could probably be measured. In fact, I'll bet one wire generates more drag than both struts by quite a bit. Would they generate nearly $800 worth of drag (4 x $180)? Not in my book! Rods sound good to me. The loads are low enough that if saving money is the name of the game, I'll bet swaged control cable of the appropriate size with shrink wrap over it to smooth it up would do the trick nicely, although cable is probably more expensive than rod, now that I think about it. +++ #1574 Subject: Re: Flying Wires From: Rod Smith I have planned from the start on using the flying wires because of the significant drag reduction and they just look good. I was afraid they would be quite expensive. I hadn't called yet for a price because I am so far away from needing them. I would buy them now if we could get a group price. If building to plans the variation in length from plane to plane should be less than the adjustment that is built into them. I don't know how many would be willing to buy now, 25?-50? If someone is going to call Steen, let us know so they don't get bombarded with calls for the same item. +++ #1577 Subject: Re: Flying Wires From: Bruce A. Frank I assume we're talking about tailbrace wires. The choice, as I see it, is to use 4130 streamline tube. The 1" X .43" X .035 wall runs about $8.00 a foot, but that beats the heck out of $180 per wire. +++ #1579 Subject: Re: Flying Wires From: Gary Danford Things might have changed but I purchased my flying wires for my biplane from Nick D'Apuzzo, P.O. Box 174, Ambler, Pa 19002 The phone Number was 215/843-7637. Now I know Nick Died a couple of years ago but I understood at the time that his son's kept the business going. They were a fraction of the cost of Spruce and Steen and the wires were of U.S. Mfgr. Their wires were Stainless Steel and could be pruchased streamlined or round. There is a running debate in the biplane community about the wires. Some claim you must have rolled threads and others claim cut threads are ok. Cut threads create a weak spot at the point where the threads stop and vibration particulary at the tail is a cause for concern. Cable with swages scare me and I wouldn't go that way on a bet. At that time I purchased my flying wires Nick had all the wires I needed in stock both for the drag/anti-drag wires and flying/landing wires as well as the tail wires and fittings. I got the above address from an old sport aviation but don't get sport aviation any more so someone should check in a current issue or call and see it they are still a source. At least when Nick was alive they were excellent to workwith and the largest supplier of flying wires in the U.S. +++ #1580 Subject: Re: Flying Wires From: Archie Dunbar > Anyone have other ideas on how to lower cost? Other sources? Help! Steen Aero Labs is the U.S. Agent for Bruton who is as far as I know the only supplier. That is where Aircraft Spruce gets them. I know that Roger Rourke gets a discount from Steen for buying multiple sets for the One Design. +++ #1581 Subject: flying wires From: Bob Marek I used 1/4 1030 rod it was easier to tread, you will have to point them with an lathe to get the threads started before using a die. I talked with Bob he used 1/4 in 4130 and then sized the rod down 50 thousand's to stress relieve the treads. Cost wise $1.50 to $2.00 per wire Compared to $180.00 per . I am sure this is the route I am going, easy to switch no big problem. +++ #1583 Subject: Re: Flying Wires From: Shelly I've used threaded stainless rod on every one of my projects. They are hardly flying wires when used as tail wires! +++ #1585 Subject: Re: Flying Wires From: budd davisson MacWhyte was the traditional maker of flying wires,but they went out of business close to two years ago because of lousy service and rising costs. Another company tried to start up in Denver but couldn't deliver and the owner was recently killed in an airline accident. This leaves Bruntons in Scotland as the only maker of wires (they also bought MacWhytes tooling, which is poetic since MacWhyte bought their original machines from Brunton in the 19teens). Brunton's makes rolled thread wires which are very nice and reasonably priced but still high because that's the nature of the beast. Brunton's is distributed by Steen AeroLab in the US. +++ #1586 Subject: Re: Flying wires From: Steele, David A What if you put the rod inside of a piece of streamlined aluminum tubing? You can get that pretty cheap at a hobby shop (about $2.25 for 3' length in the large sizes) and it wouldn't add a lot of weight. You'd have to look to make sure they go big enough to fit the 1/4" wire inside of it. The hobby shop I called said they also carry an assortment of plastic streamlined tubing that might work. Food for thought, anyway. +++ #1587 Subject: Flying Wire....taper From: Tim Cramb At Arlington 98, I remember Bob pointing out on Proto type 1, how he turned down his flying wires in order to have the 'load' travel under the threads. They way it looked made alot of sense when considering that first thread to be a big bad stress riser. +++ #1591 Subject: Re: Flying Wires From: Bill Cox I am flying a 150 Pacer with 3/16 round SS tail wires. It will cruise about 130 at 2450. It originally had the streamlined Piper wires that were prone to breaking due to nicks or corrosion. With the streamlined wires I remember it being 2 or 3 mph faster. I am on the Gulf of Mexico and corrosion is a real problem, so I plan to use round SS wires. Will the leading edge strut prevent a catastropic failure if a tailwire breaks? I noticed George Jensen offered the tailwires .250 diameter or turned to a smaller diameter in Beartracks. +++ #1592 Subject: Re: Flying Wires From: budd davisson The leading edge strut was put on Pitts after a lot of breakage was experienced in the carrythrough because people (me in cluded) were moving the airplane around by lifting on the leading edge of the stab. The Hawk has a similar situation, I'll bet, because the loads up there aren't that big. As to whether the strut would stop a catastrophic failure if a wire broke, I'm not sure. It would depend on whether the tail fluttered or not. +++ #1593 Subject: Re: Flying Wires From: Bruce A. Frank > The leading edge strut was put on Pitts after a lot of breakage was > experienced in the carrythrough... But the Pipers have gotten along well with no leading strut(so the jackscrew could do its trim adjustment). It doesn't seem likely that anything catastrophic would happen if any one wire broke. I have seen several TriPacers with broken tail wires. In all cases no one was even aware of the malfunction. The broken wires were found on preflight and inspection of the tubes found no cracks or other indication of wear. Before someone jumps on me about the leading edge strut, I am aware that Pipers with jackscrews have had sliding leading edge struts installed when significantly larger engines were installed. There were cases of the tube of the leading edge of the horizontal stabilizer cracking where it entered the jackscrew sleeve. This was caused by the vibration and flexing from the increased prop wash of the higher horse power engine. My point here is that it is not likely that the tail surfaces are going anywhere all of a sudden if all the wires or struts broke. Usual preflight checks are what catches any problem with these tail brace wires. +++ #1594 Subject: Re: Flying wires From: Russ Erb > What if you put the rod inside of a piece of streamlined aluminum > tubing? The only problems I would see with that is 1) figureing out how to attach the streamlined tubing, and 2) keeping it aligned with the airstream. Sounds like an interesting idea to consider. I'm still far from that point so I probably won't be putting any ponders on it soon. +++ #1595 Subject: Re: Flying wires From: Float-by Shooter > The only problems I would see with that is 1) figureing out how to > attach the streamlined tubing, and 2) keeping it aligned with the > airstream. Maybe rough up the rod with sandpaper, slide the tube over, plug the bottom, and find a way to fill it with microballoon thickened epoxy resin? Or you could just use unthickened resin but it would be heavier. +++ #1596 Subject: Flying wires From: bearhwk27- Pondering the posts on the tail flying wires I have a few thoughts. Rolled threads should be used. Many towns have machine shops that can roll the threads, if you have the tool its easy. ( Not Big $$ ) Streamlined tubing, I would avoid it as it is above the horizontal stab in an area that will create lots of drag / turblence in off attitude conditions, ie slips and high angle of attack. The end result is loss of speed in cruise and possible large variations in rudder and elevator authority. Stick with round rod with rolled threads or streamlined wires. Count me in for an ordered set. +++ #1599 Subject: Flying Wired...... From: Tim Cramb My Chinook FLYING WIREs are 316SS small diameter tube which has been squashed.....looks like > 0 <. The ends are drilled and bent at 45 degree's for attachment. The Factory (an hour down the road) creates the 4- 6061T6 Wing struts in the same fashion by squishing round tube in their 12ft V groove press.... Shipping Flying Wires....How bout use small dia black or white PVC pipe with cap ends. +++ #1600 Subject: Tail Brace Wires.. From: Bruce A. Frank A few years ago, when I started looking at the tail brace wires on the salvaged TriPacer fuselage I am using, I thought I could do something better. I contacted a machinist friend to make stainless clevis forks female threaded pairs of left and right hand 1/4-28. I eventually had 50 pairs made expecting to sell them to others interested in similar upgrade to their V-6 STOL project. The move to CA have them still in some box somewhere. Gave a set away but never sold any. +++ #1602 Subject: Re: Flying Wired...... From: budd davisson > My Chinook FLYING WIREs are 316SS small diameter tube which has been > squashed.....looks like > 0 <. > > The ends are drilled and bent at 45 degree's for attachment. The > Factory (an hour down the road) creates the 4- 6061T6 Wing struts in > the same fashion by squishing round tube in their 12ft V groove > press.... Wow! Scary! Making a flying wire (technically known as tie-rods) in that kind of method (the bending and drilling, not the squashing) violates about a dozen basic rules of materials engineering. Don't mean to point fingers or anything, but it's the kind of thing ultra-light manufacturers are famous for (that's the only place where triangulation applies only to navigation, not structures). The right way is to reduce diameter on a cut thread wire or use rolled thread, which is better, but still should have the diamter reduced below the depth of the first thread to eliminate the stress riser caused by the abrupt reduction in cross sectional area. Brunton's flying wires are done that way: rolled threads that stand above the surface. Macwhytes didn't stand up. +++ #1604 Subject: Re: Flying Wired...... From: Russ Erb > The right way is to reduce diameter on a cut thread wire or use rolled > thread, which is better, but still should have the diamter reduced > below the depth of the first thread to eliminate the stress riser > caused by the abrupt reduction in cross sectional area. Okay, I can't stand it any more. I've read several things here about cutting/rolling threads into rods, then reducing their diameter, or was it the other way around? I'm sure a picture here would make it obvious, but I'm not seeing it. budd, could you please expand on what you're talking about here? Are we once again making a mountain out of a molehill (as we are wont to do)? Are these rods really that highly stressed in the tail area? Or are they so oversized that cutting threads into the rod and putting them on still leaves more than enough cross sectional area to handle the loads? I can't say, since I have no clue what the loads would be in this area. I really suspect the loads are no where near what the flying wires (on the wings) of an aerobatic biplane would see. I can't help thinking that these rods are so exposed that they would be easily inspected during preflight, allowing you to notice any cracks or breaks. +++ #1605 Subject: More about wires From: budd davisson Okay, you talked me into it. Here's my opinion (educated or not) about flying wires. Blame Russ for this. Cut versus rolled threads Rolling the threads doesn't actually remove any material but compresses it in so it could be argued the resulting stress risers are less because most of the original material is still there but squashed into a different shape. Also, rolled threads tend not to have microscopic scratches and surface discontinuities caused by the cutting process. Rolled threads also usually have rounded peaks and valleys which further reduces the tendency to crack. fyi: a sharp nosed scratch (if you can feel it with your finger nail its about .003" and worth worrying about, especially on aluminum) raises the local stress by as much as 15 times. Whether there's actually that much difference between rolled and cut threads in this application is highly debatable, but any vibration situation calls for some additional thought. Reducing cross sectional area between threads: If the area between the threads is smoothly reduced down to the level of the bottom of the threads, then the thread run-out of the last thread doesn't act as a stress riser for the rest of the rod because it runs out into the space above the now-reduced surface.Done smoothly, the reduction in cross sectional area gradually transfers the loads rather than localizing the transition and causing fatigue cracks. It's a little like polishing out a scratch: in effect the area of the rod is increased at the peaks, rather than reduced because of the valleys, so the stress risers are reduced. Just to confused the issue, however, it could be argued the increased cross sectional area of the threads is still a discontinuity, and it is, but not a severe one. The most important thing is that the threads and the areas around them be as polished and scratch free as practical. It's those little scratches that eat you up. Okay: someone else's turn on the soap box. +++ #1606 Subject: And Even More About Tail Wires From: William & Delinda Johnson Wow, when I started this discussion little did I know what would result. Anyway, I have read with great interest the thread cutting vs rolling discussion. I agree with the idea of rolling the threads. However, I am still confused about reducing the size of the rod below the threads. Should the rod be cut down .050 or rolled down to size? I discussed with my dad. He suggested using a swaging machine with home made dies to accomplish the rod reduction. Cutting may leave small cut marks which could be a problem. So, swaged flying wires? I already have a swaging machine. Hmm, need to give this some thought . . . Budd, this is clearly a topic for Sport Aviation. Bingelis does not have any information about making these darn wires - to my surprise. With only one global supplier, prices are going to continue north. +++ #1607 Subject: More about wires From: Russ Erb I think I'm almost there--one last (hopefully) clarifying question: So the end result is that the diameter of the unthreaded part of the wire is equal to the minor diameter of the threads, not the major diameter of the threads? I.e. the threads are bigger around than the rod? +++ #1608 Subject: Re: More about wires From: budd davisson That's right. The wires are reduced below the minor diameter and, as Bill said, they are usually swaged in production, but machining with a really good polish job should work. +++ #1610 Subject: More about wires From: Lee H. Erb Good explanation. Most of my design experience had been with helicopters. Cut threads are a definite NO-NO!!! in helicopters. We bought a commercial set of remote controlled actuators for use in a rotor wind tunnel test at Ames 40 X 80 ft tunnel. We lost the rotor down the tunnel because we failed to specify the piston material and rolled threads. (We thought we did not need to because the advertized (static) loads were so far in excess of what we needed.) We also had a supplier of NAS bolts cut some to length, cut new threads, and brush cad plate without bake. They did not tell us what they had done and between the cut threads and hydrogen embrittlement, our customer had a rotor come off in flight with the resulting fatalities. Military and commercial transport airplanes specs will not permit cut threads. Streamlined wires must be highly loaded in tension. Drag tends to bow the wires (catenary) back so obviously the wires want to bend. But they want to bend about the axis of lease resistance, hence the twist and start to flutter (decreasing fatigue life). As you know, the singing one hears (sometimes on telephone wires) may not be flutter but the Strouhal (vortex frequency) effect. On the main wing where streamlined wires are loaded, they are usually okay. For the tail though I believe the round rods are better because they are usually lightly loaded and they will bend without twisting. Their purpose to distribute the loads during control deflections. Main wing flying wires are to support the airplane. Preloading (tightening) the rods help increase the fatigue life. I may have to satisfy myself and calculate the differences in drag. Both are at so low a Reynolds Number that their respective drags may be fairly close in pounds. Yes, Russ, undercut the rod at the threads as Budd has said, and bring the tail wires down from the mountain and make it a mole hill again. Sorry fellows about this tome but, I do get wound up at times. Listen to Budd and I am sure you will be okay. +++ #1639 From: William Johnson Subject: [Bearhawk] Tail Flying Wiren Quote I got a price back from Spruce. 44 3/8 Wire is $145.36 37 7/8 Wire is $140.44 Total for 1 set is $571.60 without shipping or taxes. These are for streamline stainless steel with fittings. Round stainless would be about the same price; however, I would like the extra 2-3 mph . . . Now, if we order 13 sets, the price per set drops to $425.34 - still not cheap but a little better. If I make my own, I still need to buy the end fittings which cost $14.00 per fitting. Need 8 + materials which will cost around $130.00 (If bought from Spruce). I could probably get the fittings cheaper at Sun & Fun. The hassle may not be worth the savings and the stainless would look really nice! Thoughts? +++ #1660 From: Budd Davisson Subject: [Bearhawk] Re: Tail Flying Wiren Quote > I got a price back from Spruce. > > 44 3/8 Wire is $145.36 > 37 7/8 Wire is $140.44 > Total for 1 set is $571.60 without shipping or taxes. don't forget to get a quote for wires from Steen Aerolab. That's where Spruce gets theirs. +++ #1664 From: Rod Smith Subject: [Bearhawk] Better Price at Steens > again. Don't any body buy wires until getting a quote from Steen > Aerolab!!!!!!!!!!! I just did that this morning. Price per one set streamlined with stainless terminals $518. Price for 7 or more sets $360. They may try to sell you a Hoffman prop when you call. When I told them they were for the Bearhawk they said yes we know the plane, Bob stops by with it fairly frequently. Bill I gave them the dimensions you provided as pin to pin length. If that is not correct you can let them know. I am good for a set at this price. I wont try to handle this deal due to my location. They need one order to get the price break. +++ #1665 From: Rod Smith Subject: [Bearhawk] Steens Phone Sorry, forgot to include their phone #. Steen Aerolab Marion, NC 828-652-7382 +++ #1676 From: george velguth Subject: [Bearhawk] Flying wires: Will this work? I'm sorry I don't remember what size material is used for the tail brace wires or their length, nor do I have time to research right now, so I'll just post this and if it is useless, so be it. Wag Aero's 2000 catalog (p. 87) features tail brace wires for the following aircraft: J-3, 4 & 5, PA-11, 12, 15, 16, 17, 18, 20 & 22. If any of these wires happen to be suitable for Bearhawk use, they are priced at $84.25 ea. Wag Aero also has non-PMA'd versons of the above priced at $252.50 per set of four. Additionally, page 107 shows "Round Tie-Rod Wires" size & thread 10-32 in the following lengths: 35", 41.5", 42", 50", 56" & 60". These are sold without hardware and are priced from $15.00 to $19.50. Again, I have no idea whether any of these items are suitable to the Bearhawk, and I'm rushing to get out the door on a 5-day trip, so I just wanted to pass the info along, just in case. +++ #1691 From: Russ Erb Subject: [Bearhawk] Re: flying wires > One more question about the flying wires. When you say they need to be > turned down below the threads, are you talking about for the entire > length of the rod, or are you tapering back out to the full 1/4 inch > diameter? If tapering, over what distance? I asked my Dad (Lee Erb) about this. To summarize, grind/turn/file/whatever the diameter at the end of the threads down to the minor diameter of the threads to remove the stress concentration at the end of the thread. Then you can taper it back out to the full diameter at a 30 degree angle or less (measured from the rod center). Of course, you could turn down the whole thing if you were a glutton for punishment. Remember to polish out any scratches as best you can, or you'll be leaving the very problem this is supposed to fix. +++ #1696 From: Bruce A. Frank Subject: [Bearhawk] Clevis forks When I was making the rod ends for my tail brace wires I could not locate the type of die that swages (rolls) the threads on the ends of the rods. Let me take that back a little, I could find right hand but not left hand. So here is what I did. To eliminate the notch effect of the cut threads I designed the shank of the clevis to fit the rod very tightly (reamed to .253" with a rod that measured .025"). This put the full threaded section of the rod 1/2 inch down inside. Flexing the rod put no bending loads on the threaded section. The only loads seen by the threaded section are tensile. I have attached a rough drawing. +++ #2498 From: Rod Smith Subject: Re: Wingtip thoughts... > For the aft position light (white), I could have put it on the rudder > like Bill Johnson did, but I didn't want to drill holes through the > rudder tubes or try to figure out how to get the wire from the > fuselage to the rudder in such a way that it wouldn't eventually break > from flexing with every movement of the rudder. Therefore, I'll have > a white light on the Just a clarification here. Grimes makes a taillight for the rudder that comes with a steel ring that is welded on as an integral part of the rudder. Best done during the construction process rather than a later add on. It has predrilled holes to capture the screws that hold the base of the light unit. I went back and forth before finally deciding that I would put all my lights in the wingtip. I dont think the wiring issue is a real concern as the wire to the rudder light in my Maule was still in good condition 15 years after new. I thought I would just use the 3 in one Whelen wingtip unit but Russ has some great ideas. Also with the antennas. +++ #2500 Russ Erb Subject: [Bearhawk] Re: Wingtip thoughts... And to clarify the clarification... I guess I wasn't too clear (I knew what I meant...) when I said I didn't want to drill holes in the rudder tubes. Those hole were for the wires to pass through. +++ #2501 Rod Smith Subject: [Bearhawk] Wire to Rudder Tail Light > And to clarify the clarification... > > I guess I wasn't too clear (I knew what I meant...) when I said I > didn't want to drill holes in the rudder tubes. Those hole were for > the wires to pass through. I see what you meant now. I guess an elegant way to route the wire would be to weld 1/4 inch tubes through the tailpost and the rudder spar for the wire to pass through. On my Maule it was just routed back to the tail post. From there it went on the outside of the tailpost and rudder spar, but under the fabric. +++ #2718 From: Barry Schutt Subject: Flying wires William----just wanted to make an inquiry about the purchase of the flying wires and its' status? How's it going? Haven't heard in a while and have been expecting a package on my doorstep anytime now. Thanks sorry if this is the 2nd message but I don't think the first one went????????don't know what happened---you know these #@%&*#computers +++ #2719 From: William Johnson Subject: RE: [Bearhawk] Flying wires I left a message last week for an update and have not heard back yet! I will give them a call to get updated status. Their 12 weeks is almost up! +++ #2831 From: Float-By Shooter Subject: streamline tail brace wires I got my streamline wires in the mail today, they are NICE! Those of you who didn't take part in the group buy really missed out on a good thing. +++ #2833 From: Russ Erb Subject: [Bearhawk] streamline tail brace wires > I got my streamline wires in the mail today, they are NICE! > > Those of you who didn't take part in the group buy really missed out on > a good thing. Tell you what, Del--I'll buy you lunch with the money I saved by not buying streamlined wires. Of course, you'll have to wait for me since I'll be landing 5 minutes behind you thanks to all of that drag from those round wires... +++ #2834 From: Float-By Shooter Subject: Re: [Bearhawk] streamline tail brace wires > Tell you what, Del--I'll buy you lunch with the money I saved by not > buying streamlined wires. Of course, you'll have to wait for me since > I'll be landing 5 minutes behind you thanks to all of that drag from > those round wires... Heh, point taken. If I'd only gotten them for the streamlining, it would have been a stupid thing to do. But I have a nice set of stainless steel brace wires which will never rust (important up here), are probably better made than what I would have produced, and I didn't have to make them. Not to say that I wouldn't have done a good job on them, but they wouldn't be *perfect* like these are. I am pretty sure the threads are rolled, rather than cut too, whether or not that will make any difference in this application. For what it's worth, my brother just bought a set of 4 ROUND stainless tail brace wires for his Citabria, and I am pretty sure he paid at least as much as we did for the streamline ones. Of course he also had to pay the additional cost of printing up those yellow tags. +++ #4371 From: Ken Beanlands Subject: Mountain Goat I believe that Bill is out ther esomewhere on this list. Anyway, I was looking through the Feb Kitplanes and saw the Mountain Goat. I'm interested in what you used for the tail brace wires. It appears that they are straps of some sort. It appears to be a relatively simple method of getinng "streamlined" wires. Are they straps? Whad material did you use? are they adjustable as with threaded cables? This may be a better idea for the Christavis than buying threaded rods. +++ #5217 From: Ken Beanlands Subject: Tail Wires I just had a question on the tail wires. I like the idea of threading the 1/4" cables myself (actually, I want to use it on the Christavia), but I'm wondering about the need to turn the 1/4' rods down. That swwms to be a lot of work for a small weight/drag savings. Am I missing something here? can anyone see any problem with just using threaded 1/4" rod without turning them down? Also, I notice that there is no locking nut employed. Is it needed? The Christavia calls for streamlined rods, but they are way too expensive for my tastes. +++ #5220 From: "DANFORD, GARY" Subject: RE: [Bearhawk] Tail Wires I think I've read somewhere that Bob turned down the rods below the level of the Thread Cut. Apparently that reduces the probably of a fracture at that point?? I don't understand that fully because one thread cut up is again lower that the high point on the previous thread. Rolled threads are suppose to be the answer but its almost impossible to find someone to do that. We seem to be overly concerned about flying fast. I fly for the enjoyment of flying and don't always want to get there that fast. There are lots of hot rod airplanes out there if you want to go fast. I choose the Bearhawk because it has moderate speed and will haul some baggage, 3 to 5 MPH isn't that important to me for the cost. The trip's I fly it would only save 10 to 15 minutes anyway. +++ #5229 From: "Tim Anderson" Subject: RE: [Bearhawk] Tail Wires How about welding a bolt into a peice of tubing???? Probably be a bit big, diameter-wize compared to a rod. Glue some balsa wood farings on it after it is adjusted to the correct length. +++ #5231 From: Kevin Deutscher bearhwk272@a... Subject: Re: Threaded Rods The issue of turning down the rods for the tail wires has been covered before here. Check the archives. The short end of the issue is as follows. Aircraft threads are either rolled or cut with a " J " root profile. A thread is a stress riser, a rolled thread is better because of a formed root radius and the surface is put into compression. Bob's turning of the rod to .250 makes the rod smaller than the minor diameter of the thread, the stresses in the rod section are now higher than in the threaded section. If the rod is going to crack it should happen out where it will be visible and can be detected. +++ #5233 From: Russ and Penny Erb Subject: RE: [Bearhawk] Tail Wires We went around this block a while back too. See the archives or the BHCD. The point of turning down the wires is to smooth out the stress concentration at the end of the thread. If you don't want to do the whole rod, then just taper it gently back out to the original diameter. Some of our members opted to go for streamline wires and made a group buy a while back. As for me, I plan to go with round wires as per plan. The locking nut could be used if it makes you happy, but if both ends have the same direction and pitch of thread, turning the rod will screw it farther in one end and out of the other without changing the length of the assembly. That's why a turnbuckle has a left and a right thread. +++ #5234 From: Russ and Penny Erb Subject: RE: [Bearhawk] Tail Wires Assuming you mean what I think you mean, as in just stick a bolt on the end and butt weld it--bad idea. The weld would be loaded in tension, which is not good for welds. Welds are much happier when loaded in shear. Besides, what's so difficult about turning a die on a rod, then filing down around the end of the thread? +++ #5235 From: Tim Subject: Re: [Bearhawk] Tail Wires Stresses I asked Bob about this taper on the flying wire, while at the Arlington 98 Fly-in. He said, it (the taper) was designed to route the stresses under the threads instead of having them arrive/stop at the first cut/riser.... +++ #5236 From: Corky Scott charles.k.scott@d... Subject: Re: [Bearhawk] Digest Number 332 Old mechanic's trick Ken. Use two nuts and turn them tightly against each other. Then crank the rod as necessary with a wrench slipped over one of the nuts. This is the method I used to tighten the drag anti-drag rods in the Christavia wing. +++ #5237 From: Benton Holzwarth Subject: re: Tail Wires Corky -- I think Ken was talking about lathe-turning the rods, for stress-riser relief where the rod body meets the threaded section. Some people have suggested turning down the entire length of the rod. The more pragmatic suggest just tapering smoothly back to the nominal rod diameter over an inch or two. For turning (or just holding the rod still while turning something else) every tail-wire rod I've looked at on factory planes has a pair of 'flats' pressed into the rod, an inch or two in from one end. I say pressed (vs. ground) since the bulged up material is visible at either edge of the flat. Is grinding or filing actually deprecated due to material loss or something? Also, I'd always just assumed that one end of the rod had a LH thread, and was tightened up 'turnbuckle' style, but of course, they never have safety wire, and someone just pointed out that both ends are RH, so there's no particular impetus for it to come unscrewed. So, question is, is the tension set by adjusting the end fittings, then pulling things tight with the bolt/nut at the outboard end of the stabilizers? (Must be -- I was just a little surprised it was done that way, a bending load on the bolt until the nut and end-fittings are tight against the stab-spar, and the bolt is in shear and tension.) Had another thought regarding the lathe turning of the rods. Rather than start with 1/4" rods, threaded, and turned down to, say 3/16" for the body, could one start with 3/16" rod, and build up the ends in some way to make up the material for the 1/4" die? Maybe attach an inch of some sort of sleeve, or compress the end 1-1/4" down to 1" to expand it out to 1/4" diameter? ( I guess if I had the wherewithall to do that, I'd be doing my own streamlining as well, but I thought it was worth asking, in case there's some easy way to do it.) There's a technique for fastening sleeves, where you cut holes in the outer tube, and weld around the circles (is there a name for this?) -- could something like that be made to work? (Of course, this is in strictest violation of my 'Keep it simple --' montra.) And I'm guessing this area is highly stressed enough that disturbing things with welding and etc is not a good idea. And how about the strength of the sleeve material after all the threads have been cut into it... ___/\/\/\/\ ___________\_____________\ (W)______________________/ ___ / \ \/\/\/\/ +++ #6103 From: Benton Holzwarth Subject: re: fuselage tubing From: pfflyerz@c... > > 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. > > Pat Fagan #232 Pearblossom CA This sparked another idea: the horizontal stab calls for either a squared channel or tubes for the 'ribs'. I'd assumed the channels would be bent up from sheet, but maybe it'd be easier to split some square tube to make the channels... With the right dimension material, you could make two lengths instead of just one for each cut. Benton 24may01 +++ #6131 From: pfflyerz@c... Subject: Re: [Bearhawk] re: fuselage tubing bcgh@a... writes: > This sparked another idea... I am not sure this would be worth the effort for two reasons. It could be done on the vertical and horizontal tails, but you would still have to beat over the small flange. If you have access to a shear it is much quicker to shear and bend the channel than it would be to split the tube. The other problem is that the rudder and elevator use a tapered rib, so the square tube wouldn't work there. Pat Fagan #232 Pearblossom, CA +++ #6196 From: Benton Holzwarth Subject: T-25s (was: re: fuselage tubing) Tim Anderson and I kicked this back and forth a time or two, and I finally pulled together a drawing of what I had in mind. I agree that it's taking the long away around, but I understood that the problem people are having is with forming the little 45-deg lip Bob calls out on the plans. That and getting the taper just right to fit between the two different sized tubes. My idea was to use two separate pieces of channel, either cut from a piece of square tubing, or bought as channel or fold-your-own. After these are fit and welded to the two tubes, intercoastals are tacked on to support the gap. Seems like weight would be at least close to the original, maybe a little heavier -- and behind the hinge-line on the elevator and rudder. There might also be an issue with heat distortion welding the little tabs. Don't know how the loading would work, and how much web you'd really need on the channels. Just a thought. I'm a long way from getting my chance to try Bob's way. Benton Holzwarth 28may01 +++ #6205 From: Budd Davisson Subject: Re: T-25s (was: re: fuselage tubing) Benton, The use of tubing for tail ribs has been discussed before. Lots of airplanes use 1/4 inch round tubing with small intercoastals and this would work here. I think The Bob even said it was okay, but would be heavier. It wold also be more expensive. Cutting square tube and facing the resulting channels towrds each other would work, but you'd have a tough time getting primer/paint up inside the channels to stop rust. bd +++ #6360 From: Russ and Penny Erb Subject: Oh, no! Streamline Tail Wires Again?! Well, not quite, but close... The subject is the fittings at the ends of the tailwires. We've talked about this before, but there's an important connection (pun not intended, but I'll take it anyway) that was never emphasized. budd has made a big deal out of how much he had liked The Bob's low-buck solutions to common problems. If you review budd's PIREP on the 260HP Bearhawk on airbum.com, you'll see a picture of how The Bob made the fittings for the ends of the tail wires out of thick walled 4130 tubes by threading, smooshing and drilling them. I must agree--very cool. I always assumed this was the method shown on the plans. Well, it ain't. As I've been reviewing the tail drawings while getting ready to start that section, I noticed that Drawing 21 calls for AN665-34 clevis tie rod terminals in these locations. There are two reasons I like the way it was done instead of the way it was drawn. As drawn, there is a higher parts count. Second, AN665-34 clevis tie rod terminals run about $14 US, even more in Canadian. Consider that you need at least 8 of them, that makes a total cost of around $112. Compare that against a couple of bucks for a tube and a few more bucks to buy a right and left hand tap. Recommendation: Mark your Drawing #21 to remind yourself that there is an alternate method. While you're there, take note that the design of the tail surface hinges includes tabs welded to the tube on the non-moving side of the hinge. Sort of a flat V-shape. I think this helps support the hinge. This only appears on Drawing #21. You can also see it in http://home.fuse.net/wjohnson/Mvc-762f.jpg near the right edge of the picture. This is another important subtle detail that you should make an extra note on your plans about. Russ Erb >>> 2mar02 #7686-9153 +++ #8229 From: Russ and Penny Erb Subject: To bolt or not to bolt... > From looking at pictures of the prototypes, Bill Johnson's and > Pat Fagan's airplanes, not to mention the plans, it appears > that the rear tube of the horizontal tail just slides over its > support tube without any sort of bolt through the joint. > Between the elevators being bolted together and the support > wires, there's plenty to keep it from coming off. As I type this, it starts to make sense--I can't bolt it at the rear tube or it would be impossible to adjust the tail incidence to adjust the trim. The horizontal tail should be adjusted (by changing the length of the support tube at the front of the tail) to give zero or near zero trim tab deflection in some desired condition, such as level flight at cruise speed. Russ Erb #164, Edwards CA +++ #8277 From: Erb Russell Maj DET 5 AFOTEC/DOB Subject: Coarse or Fine Threads - For Machinists with opinions I'm getting ready to fabricate the tail wires for #164. Since the AN665 clevis tie rod terminals called for in the plans are over $13 a piece, and there's at least 8 of them (over $100), I'm pursuing "The Bob's" low-buck method of making my own tie rod ends by smooshing and threading tubing. budd mentioned this in his Bearhawk 260 PIREP. The proper size of tubing seems to be 7/16x.120, which has a .197 ID. This is slightly smaller than the hole required for a 1/4" NC or NF tap. I'll be using the "high drag" round wires made from "cheap" 1/4" 4130 rods (cheap compared to streamline wires). If you want to see the debate between streamline and round wires, go back to the archives. It was quite entertaining. Since I'll be tapping and die-ing my own stuff, I have to make a few decisions of which I don't feel qualified to make. Here's your chance to state your opinions: Question 1: Is it better to use coarse threads or fine threads? Which is stronger? Question 2: How many threads need to be engaged to develop full strength? Question 3: Should I use right hand threads on both ends or right hand threads on one end and left hand threads on the other? RH-RH requires detaching an end to adjust, but won't change length if the rod turns. RH-LH allows adjustment by turning the rod (like a turnbuckle), but therefore will change adjustment if the rod turns unintentionally. Yes, I already know that the rod will need to be turned down after the last thread to remove the stress concentration. Russ Erb +++ #8279 From: "Bruce A. Frank" Subject: Re: Coarse or Fine Threads - For Machinists with opinions > Question 1: Is it better to use coarse threads or fine > threads? Which is stronger? In 4130 fine is more than up to the job. > Question 2: How many threads need to be engaged to develop > full strength? A minimum of 5 is what the books say, but on a part that literally flaps in the breeze I like to add two or three more for good measure. > Question 3: Should I use right hand threads on both ends or > right hand threads on one end and left hand threads on the > other? RH-RH requires detaching an end to adjust, but won't > change length if the rod turns. RH-LH allows adjustment by > turning the rod (like a turnbuckle), but therefore will change > adjustment if the rod turns unintentionally. I have built adjustment rods both ways; both ends right hand and each end opposite. The left hand/right hand on opposite ends is superior for accurate adjustment in my book. You are going to use lock nuts and that with a drop of Loc Tite makes unintended movement virtually impossible. Russ, if you are interested, I have stainless steel clevises (rod end forks) internally threaded left and right hand 1/4 X 28 with nuts. These are designed to have a threaded rod screwed into them. This would allow you to reduce your rod diameter to 1/4 inch. My intent was to use stainless rod also. Tell me how many lefts and rights you need and I'll send them to you. After your evaluation, if you can use them they are yours. I had these made up over ten years ago and they have been sitting on the shelf ever since. I seem to have misplace the pins, but they are available from McMaster-Carr or you could use a bolt in place of the pin. Bruce A. Frank +++ #8282 From: charles.k.scott@d... Subject: Re: Digest Number 623 > I'll be using the "high drag" round wires made from "cheap" > 1/4" 4130 rods I'll be using round 4130 drill rod too, but it won't be round by the time I'm done with it. I'll either be using snap on type streamline plastic covers or I'll painstakingly create them out of wood and bond them in place. Wood used to be used for years as the method for streamlining round tubing, it would work again. Corky Scott +++ #8284 From: "bearhawk484" Subject: Re: Coarse or Fine Threads - For Machinists with opinions #1 Fine threads are stronger in steels #2 Rule of thumb is ,thread engagement no less than 1.5x the diameter of the thread #3 I agree with Frank. LH RH is the way to go Mike mellor +++ #8374 From: Russ and Penny Erb Subject: Rigging tail tie rods I've just finished installing my horizontal tails and rear tie rods, and have made several observations that were not apparent to me prior to starting but now seem obvious. The issue is the flexibility of the tail post. The tail post above the fuselage (vertical fin) is far less rigid than the portion of the tail post in the fuselage truss. Even though I haven't built the rest of the fin yet, when it is built the problem will still exists. Why do I care? Because all of that work you spent making sure the hinges on the rudder are snug but free moving becomes wasted if the tail post bends. A bending tail post twists the hinges on the rudder spar and adds friction. Friction in a control system will cause problems (actually there are reasons that a very small amount of friction might be useful, but if you make every effort to reduce friction, the residual friction will still be plenty). A while back I asked if tie rods should be threaded right/right or left/right like a turnbuckle. After doing it, I am convinced that left/right is the right answer. Using the tie rods like turnbuckles made this process very easy. The four tie rods must work together to hold the horizontal tails horizontal and not bend the tail post. There is only one solution (set of lengths) that will accomplish this. Here's my method of finding that solution: 1. Level the fuselage laterally using a sensitive level, such as a digital smart level. 2. Install the rudder if you haven't already. 3. Install the upper tie rod on one side, and adjust it until the horizontal tail is level. Note that at this point the tail post may be bent to one side. That's okay, we'll fix it later. 4. Install the lower tie rod on the same side, and adjust it until taut. Make sure the horizontal tail is still level. If you lift on the horizontal tail, it should not move from level without moving the whole fuselage. This part is important, because of the rigidity of the fuselage, this rod will hold the tail in position when adjusting the top rod later. 5. Repeat 3-4 for the other side. 6. Tighten the jam nuts on the lower tie rods. 7. Loosen both upper tie rods until neither one is pushing or pulling at the upper joint of the tail post. The rudder should move freely in this position. 8. Slowly tighten the upper tie rods, checking frequently for bending in the tail post, as shown by friction in moving the rudder. Tighten the rods evenly. 9. At some point the upper tie rods will be tight enough to raise the tails to level. Tightening the rods any more will increase the friction in the rudder. This is the point you want to stop at and tighten the jam nuts. The tails should be level because you didn't change the length of the lower tie rods. I did all of this by turning the tie rods with my fingers. They don't need to be so tight that you need pliers. If you get them that tight, your rudder will probably have too much friction. Next I get to build the struts for the front of the horizontal tails... Russ Erb +++ #8459 From: Russ and Penny Erb Subject: RE: Re: Brake Disks > I have a question about horizontal stab rigging. In 1998 Bob > issued the engineering change to raise the front stab mount > 3/8" to accomodate a wider variety of engines. Does this imply > less than 4 degrees is needed for the larger engines? I think it is just what it says--it allows a larger adjustment range. If anything, a larger engine would cause a more forward cg, requiring more nose down on the stabilizer. Within limits, you will be able to trim your airplane regardless of the position of the stabilizer. It would just take more elevator deflection, causing a little more trim drag. For a given flight condition (usually cruise), there is some optimal position of the stabilizer that produces the least trim drag. I think (but can't prove) that this would be when the elevator was aligned with the stabilizer with zero stick force. I built my tail to the recommended 4 deg nose down. Unless the trim position is really off, I'll probably just leave it unless I'm just looking for something to do. Russ Erb +++ #8493 From: Russ and Penny Erb Subject: Another one to file away... Here are a four more tips that you'll want to file away for future reference. I was reminded of these while visiting Pat Fagan and using his lathe to turn down my tail tie rods. 1. A couple of corrections to Drawing sheet 16A (Fus. Mod. Rear Doors). Near the top of the sheet in the drawing of Section T-T, the note should read "Dim. tapers from point 4 to point 6" instead of "5". Pat said he determined this by inspection of the prototypes. Makes a lot more sense when you see it, too. 2. On the same sheet, the drawing of Section S-S reads "Dim. tapers from 1 to 2 and 2 to 3". I can't reproduce how I came to this conclusion, but I wrote on my sheet that there is no taper from 1 to 2. Since I can't reproduce the reasoning, I'm not as confident of this one. Russ Erb +++ #8496 From: "t18cox" Subject: Tailwires You mentioned turning the tailwires. Did you turn down the full length or just a short section next to the threads? I'm about at that point and was thinking turn down to mimimum thread diameter and then a gentle taper back to 1/4". Bill Cox #303 +++ #8498 From: Russ and Penny Erb Subject: RE: Tailwires On Pat's recommendation, I turned a taper with a 2 degree included angle (compound rest set at 1 deg off centerline). I turned it down to the minor diameter of the threads, and the tapered area is about 1-1/2" long. Works well and was a lot less work than trying to figure out how to turn the entire length, which would probably have taken longer than I had patience for. (Funny thing how when you drive an hour one way to use someone else's tools, you have to finish the entire job in one sitting--it's tough to take more than a short break and come back to it.) Russ Erb >>>20may03 #11298-18250 +++ #11299 From: Russ and Penny Erb Subject: RE: Tail feathers > 1) For each of the T25 channel parts, are they to be made for the > specific location to fit? Are these to be made from sheet? For > those who have done this, did you buy a brake, or have this done > somewhere? As I did it, each T25 channel part is made to fit its specific location. You will note that most of them are different widths at either end since the tubes are different diameters. The channels are bent up from .032 sheet. The two 90 deg bends are fairly straightforward on a brake. The 45 degree flanges are tougher, and have typically been hammered over special forming blocks. It's all shown on the Bearhawk Reference CD! (I can't help notice you haven't ordered one yet, at the ridiculously low price of $20. See http://www.qnet.com/~erbman/bearhawkcd.htm for info. Note: for this specific question, I would encourage you to wait another month or two until Version 3 comes out, since it has more detailed coverage of these operations.) > 2) On the elevator/rudder hinges, there is a V labeles 1/2 wide. > What is the purpose of this? The Vs add support to the sides of the hinges. See the "Typ. Hinge For Elevator & Rudder Full Scale" drawing on Drawing 21. Also shown on the Bearhawk CD! > 3) Since the trim linkage is offset from the elevator hinge point, > won't the trim change with the postition of the elevator? Yep! Very perceptive. Step out to my shop and I'll show you...the tab moves very little relative to the elevator as the elevator goes up, and the tab moves up as the elevator goes down. Is this a problem for flying qualities? Not really. Remember that the elevator moves very little during normal flight conditions, so there won't be much change. The only time the elevator (and stick) move a lot is at low speeds, such as stalls or takeoff/landing, and then you're not too concerned about being in trim. It apparently doesn't change the linearity of the control forces and deflections that much since budd didn't comment on it in either of his flight reports. Russ Erb +++ #16437 From: "Dave Roberts" Subject: Flying wires I have a question about flying wires, round verses streamline. I plan to use the bearhawk for a lot of off field landings. I read somewhere that streamlined wires were more prone to rock damage. Should a person put round wires on the bottom of the stab? Or does it matter that much? Thanks Dave Roberts +++ #16438 From: Russ and Penny Erb Subject: RE: Flying wires That is merely one issue. You'll find that the cost difference is several orders of magnitude. I'd be surprised if you saw more than a couple of knots difference in speed. I'm a round wire kind o' guy. Russ Erb +++ #16440 From: Matt Prather Subject: Re: Flying wires Not as good as streamline wires, but you can put fairings on them which are cheap if you build them yourself, and probably help to protect them. I'll bet round wires aren't that much more impervious to damage, but you don't care near as much when you do because they are cheap to replace. Regards, Matt- +++ #16442 From: "Dave Roberts" Subject: Flying wires Checked with Steen Aero and they said no price difference between round and streamlined. That's why I was wondering about the rocks. I'm kind of a round wire kind of a guy too but I had a Starduster that had streamlined. They sure were pretty. Thanks for the input, Dave +++ #16443 From: Russ and Penny Erb Subject: RE: Flying wires Okay, so we weren't clear in what we were saying. As designed, the tail wires are simply 1/4" diameter 4130 rods that are threaded (left hand one end, right hand the other), with an inch or two turned to taper down to the final thread to remove the stress concentration. There was a lot of discussion about this a long time ago which was captured on the Bearhawk CD. About $10 of material instead of several hundred bucks. Russ Erb +++ #16445 From: "Dave Roberts" Subject: Re: Flying wires I didn't think I could do a good enough job tapering the rod from the threads since the support on my lathe doesn't go down to 1/4". But after looking at the cd again I thought I would try to spin the rod in the lathe and just file it then smooth it up with emery cloth. It worked alot better than I thought it would. Did you put a taper on away from the threads too or just round them to the taper toward the rod center? Thinking of what I can use that other $300 for, Dave +++ #16447 From: "Lee H. Erb" Subject: Lower Flying wires 1. The Reynolds numbers of both round and streamlined flying wires will be so low that the drag is about the same up to 120 knots. 2. If you are concerned about rock and sand damage, put rubber tubing over the wires. Surgical tubing works but doesn't look that good. We used to call out metal for rotor blade leading edges to prevent erosion and neopeme sheet covering to prevent sand erosion. It was very interesting to see the erosion patterns (and holes) in stainless steel leading edges that had been in sandy area for 10 hours. Lee H. Erb +++ #16448 From: Del Rawlins Subject: Re: Lower Flying wires We'll see how the streamline wires hold up to gravel strips I guess. The main reason I bought mine was for the anti-corrosive properties of stainless steel, with the streamlining being a cool bonus. I don't recall them having been super expensive at the group buy price. Since I'm planning to mostly be on floats, I'm not going to get too worried about rock dings, and yes, I know that the floats will slow me down enough that the streamlining won't make a big difference. 8^P This thread has me wondering, if there isn't any reason a builder couldn't make the tailwires out of round stainless steel, and if 1/4" would be strong enough (SS being softer than 4130) or if they would need to be sized up. I'm inclined to think that 1/4" is overkill anyway, since the wires on the Citabria are closer to 1/8" thick. That is a lower gross weight airplane but it is stressed for aerobatics. Tom put PMA'd stainless wires on his and I know they were the same size as stock, because he just powdercoated the old fittings and reused them. -- Del Rawlins +++ #16449 From: "t18cox" Subject: Re: Lower Flying wires The actual diameter of the wire if turned down per Bob is about 0.20. Bob told me it is not necessary to taper if you don't want to turn down full length. Just turn a nice radius at the end of the threads to minimum thread diameter. Bill Cox +++ #16451 From: bearhwk272@a... Subject: Re: Flying wires threads Just a reminder on the thread thing. Preference for threading the rod, assuming thread runout undercut or R. 1. Rolled threads with UNJF thread profile. J = controlled root radius ( Rod ends have this thread.) 2. Cut threads with UNJF thread profile. 3. Cut threads with UNF profile. Kevin +++ #16452 From: "fourthwedge" Subject: Re: Lower Flying wires Budd's got the best article I've read on this @ http://www.airbum.com/articles/Flyingwires.html Lots of good info on flying wires (and landing wires). Dave +++ #16455 From: "Bruce A. Frank" Subject: Re: Lower Flying wires For the strength and the vibration to which the tail brace wires will be subjected I can see no reason not to use 1/4" diameter stainless rod. I know several dozen V-6 STOL's fitted with stainless rod as the main brace on the tail surfaces. Years of flight with no trouble. Bruce A. Frank +++ #16456 From: "Bruce A. Frank" Subject: Re: Re: Lower Flying wires > Are the threads on the wires cut or rolled? Cut is adequate. Cut is one of the reasons for machining the taper or rounded groove at the transition between the threads and shank of the rod. Finding someone to roll threads appears to be difficult. Buying what it takes is very expensive. Selection of a stainless rod of 316 alloy would provide all the strength necessary and reduce the likelihood of work hardening leading to cracking in the threads. Bruce A. Frank +++ #16469 From: "t18cox" Subject: Re: Flying wires I have my flying wires made from 4130 and will probably start flying with them. Here on the Texas coast corrosion is a real problem, so I'd like SS wires. There are companies in this area that fab tiewires for industry. They take a SS rod that is about the minimum thread diameter, upset the end to the needed diameter, then roll the threads. I think this is the same basic process used by companies making flying wires. My neighbor is in the machine shop business is looking for someone who will do me a set of wires. Don't know what it will cost, but he thinks not to much. Unless he runs into someone who is an airplane nut I'm sure we will have to come up with some none aviation related use for the wires. Bill Cox +++ #16495 From: Russ and Penny Erb Subject: RE: Lower Flying wires The forward strut on the horizontal tail is a streamlined tube. As for the tail wires, 1/4" rod is 0.167 lb/ft. 1.012x.428x.035 streamline tube (the smallest in my Spruce catalog) is 0.2687 lb/ft. Rod is $0.69/ft, streamline is $7.75/ft. Consider that the frontal area of the streamline tubing is 1.7 times bigger than the rod, which could well negate any benefit from being streamlined. I just don't see any benefit. Russ Erb +++ #16514 From: "Bruce A. Frank" Subject: RE: Lower Flying wires I don't have the numbers and my plan was to also use round stainless 1/4" rod, but somewhere I believe I read that for the difference in drag, a streamline shape (egg or short streamline shape) can have 3 times the width of a round shape before drag equals that of the round. There was an article in one of the mags a few years ago that stated that a round rotating beacon on top of the vertical stabilizer had more drag than all the rest of the empennage. I haven't played with the numbers in a very long time, but I seem to remember that the difference in drag between round wires and streamline (tail wires) can be 4 mph at 150 mph. Bruce A. Frank +++ #16525 From: Russ and Penny Erb Subject: RE: Lower Flying wires Bruce--there's a Reynolds number difference. It's tough to explain or understand unless you've studied fluids and aero, but here's the general idea. We're used to thinking of air as non-viscous, and at high speeds and over distances sufficiently large it is. But at low speeds and over short distances, air acts much more viscous, like oil or molasses. On items the size of a rotating beacon, the air will stay attached about halfway around, and then separates (doesn't follow the shape) and that creates lots of drag. On items the size of the tail wire, the air stays attached much farther around the wire (more viscous) and thus creates less drag. The frontal area becomes more of an issue than the separation drag. So much for the theory. We'll probably never know (just like the number of licks to get to the center of a Tootsie Roll Tootsie Pop [Answer--3]) how much difference it makes unless someone tries both on the same airplane. Even then, changes in cruise drag of that magnitude are tough to measure, and tend to be exaggerated, especially when it's good for marketing. Russ Erb +++ #16578 From: charles.k.scott@d... Subject: Flying wire covers I have heard of people fabricating streamline covers for wire using balsa wood. It took a lot of work but doing the labor is what saves the money. Then about 5 years ago I heard about a company that was fabricating plastic wire covers that were streamline shaped. They just snapped on over the wire. Haven't heard of anything like that since, but I'd be REAL interested if anyone can point such things out to me. Thanks, Corky Scott +++ #17664 From: rsmith@f... Subject: Flying wires was Bearhawk Muster 2003 A heads up for some of the newer guys on the list. If you are buying the high dollar stainless, streamlined Brunton flying wires, you need to get together and do a group purchase. Several of us did that a few years ago and saved nearly half over ordering them individually. I believe Steen Aero still is the exclusive distributor in this country, so don't buy them somewhere else, you will pay more. Rod Smith +++ #18196 From: "John Haugen" Subject: Re: I come to praise Dan Shilling, not to bury him... > ...of course, I used the heavier tube for the horizontal stab > leading edge too. What is the reason for the heavier tube on the hor. stab? Is that to eliminate the need for a strut on the stab? JH +++ #18201 From: Russ and Penny Erb Subject: RE: I come to praise Dan Shilling, not to bury him... Look at drawing 20. On the leading edge of the stabilizer, the plans call out T14 tube (7/8x.049), which is almost immediately spliced to T13 tube (7/8x.035) for the remainder of the leading edge. As the tubes are the same diameter, we figured that The Bob had called out the thicker tube for more bearing area on the attachment bolt. "Back in the day", namely April 1998, Rod Smith suggested eliminating the splice by using T14 tube for the entire leading edge. Yes, it adds less than a pound way back at the tail (normally very bad), but if you are planning a big engine (O-470, O-540), you're already trying to figure out how far back you can get the battery to balance the engine, so a little extra weight at the tail is actually a good thing in this case. The other benefit was a perceived strengthening against rocks thrown into the stabilizer on the ground. This is what I was referring too. To eliminate the strut on the stab, you would need to totally redesign the attachment to the fuselage. It's all on the BHCD. Russ Erb +++ $Id: 2.2.1-Tail-Stabs,v 1.11 2003/05/21 15:03:55 bentonh Exp $