+++ #157 Subject: The Jig Is Up! From: Russ Erb No, that doesn't mean the party's over. It literally means just what it says! Last night I finished riveting the attach angles on the flap and aileron spars and put up the jig to assemble the flaps. I'm using 2" square steel tubes with 1" steel tube arms welded on sticking out to support the spar. Contrary to what was published either on the newsletter or on this list, I've decided to build the flaps, ailerons, and wings in the vertical position much like the RV builders do. Several reasons: 1) I don't like depending on a table top to define a plane. I prefer using plumb lines and strings to define the plane. 2) Nothing is truly flat on any of these pieces to easily sit on the table 3) My workshop is quite small, and the pieces fit in there better vertically than horizontally. 4) Several thousand RV builders can't all be wrong... Note: If you personally feel more comfortable building yours on a table, that's fine with me! I used a combination of SmartLevel, line level, and laser level (a cool toy! (but be careful you don't look back at it!)) to get the arms of the jig level with the earth and at the same elevation (a challenge since the floor is not flat). I was surprised that it took less than half the effort that I expected. On the ceiling of the garage, I screwed a 2x4 into the rafters. I then hung a 1" piece of angle iron from this 2x4 with a drywall screw through a hole. The top of the jig tube was clamped to this angle iron. The bottom of the jig tube was immobilized by liberally slopping Bondo around it on the concrete floor. When is is time to move the jig, I'll just hammer the Bondo with a screwdriver, and it cracks apart and comes right up (doesn't stand up very well to impact shocks). Much cleaner than screwing into the concrete. Well the Bondo is about cured, dinner is ready, then it's back to work! By the way, Del, you saw the bend radius on 4130 in Bingelis' Yellow Book (Sportplane Construction Techniques) right there at the post-it note (that's page 44 if your's doesn't happen to be marked like mine). 1t still seems awfully tight to me. Remember, just because it's the minimum doesn't mean you have to bend it that tight. +++ #164 Subject: Re: The Jig Is Up! From: Russ Erb > Pardon my cluelessness. I don't yet have a set of plans or newsletters to refer to. What does "build the wings in the vertical position" mean? The plans don't call for anything. The method recommended in the newsletters calls for building it on a flat table. My first concern was actually getting the table "flat." My floor is anything but flat. The second concern was space--didn't have enough. Building it in a vertical jig gives you access to both sides (i.e. top and bottom surfaces). If you know any RV builders, talk to them about how they build their wings. The newsletters call for attaching the ribs to the spars with everything sitting on a table, then putting the wing in the jig leading edge up for skinning. I've just decided to do everything in the vertical position. > Apologies in advance, as I guess I'm asking about stuff that all the actual *builders* on the list already know. < Do you know a better way to learn? No problem. We're an old enough group now that we're going to have people at all different phases of construction. Unlike when we started and everybody was working on forming wing ribs, we should start to expect getting questions that were covered 2-1/2 years ago, since those people weren't building back then. +++ #276 Subject: Re: New Builder (and Rib Attach Angles) From: Float-by Shooter > One thing I'm blessed with is that from my driveway to Bob's strip at > Fincastle is only 125 miles, and it's 75 mph most of the way. Lucky Bastige. > 1. There is an art to figuring out the length of the ribs. There was a post in the archives from way back when (before my time) on how to do this, which I will try to dig out and put in the FAQ. What I did (just like the message said to) was make marks on my forming block where the ribs should end, and mark the rib blanks in the proper places and trim before forming. The main thing is to number each rib with your marker and make a list of how much to trim each one. You have to allow a hair for the thickness of the spar web (.032) and after that it is just a matter of trimming where needed in 1/8" increments. > 2. I have NO clue as to how the rib attach angles are attached > to the spars. How many rivets, and where to they go? Seems > to me the cap strips as well as the 1/4" or 1/2" filler plate > rivets will interfere with the attach angles. On my plans the > rivets all run together as black blobs (grin). My guess is that by the time you have made your ribs and attach angles, you will have spent enough time looking at the plans that you will have found that information.... > If anyone can shed some light on how the attach angles are "attached", > I'd apprecite it! >From memory (my plans are at the shop) they use 1/8" AD rivets. +++ #2050 From: William Johnson Subject: Engine Mount & Wing Fitting Pics N720SF now has an engine mount and the wing fittings are welded to the fuselage. Since the fuselage was jigged in a flight level position for the engine mount work, it was easy to verify the +2 wing setting using a propeller protractor. Here are some pictures: Front Wing Fitting: http://home.fuse.net/wjohnson/Mvc-900f.jpg Rear Wing Fitting: http://home.fuse.net/wjohnson/Mvc-901f.jpg Engine Mount Bottom: http://home.fuse.net/wjohnson/Mvc-904f.jpg Engine Mount Top: http://home.fuse.net/wjohnson/Mvc-905f.jpg Engine Mount Left Side: http://home.fuse.net/wjohnson/Mvc-906f.jpg Engine Mount Right Side: http://home.fuse.net/wjohnson/Mvc-907f.jpg I was planning to write a summary of the process I used to construct the mount and install the wing fittings but time is short. Sun & Fun waits in Florida. However, I did add two tubes to the engine mount (see bottom pic). I did not discuss with Bob so do this at your own risk - the rest of the mount is per the newsletter. Two recommendations: Get a large tip for your torch. I used a smith #5 for all engine mount welds. A smith #2 worked for the wing fittings. Build your own motor mount ring instead of purchasing. Building will give you confidence and a feel for welding the thick material. Shelly, your cables are in the mail. Expect them Saturday. +++ # 2487 Russ Erb Subject: Wingtip thoughts... A couple of weeks ago we laid up the fiberglass on my first wingtip. It seems to have been successful, but we haven't done anything with it since for several reasons. If you wish to recreate what I have done, first find yourself a good friend and fellow builder who has just finished building his composite airplane and is looking for somewhere to satisfy his building urge. You can identify this person as the one who keeps asking you "So when do we get to build your wingtips?". Hey, no one said this was easy. I didn't make any great changes to the wingtip design. (Warning--I may have said some of this before) Wingtips seem to be a favorite area for builders to "improve" the design. Fortunately, there's not a lot of structure there to screw up. People try to change the wingtips thinking they can reduce the size of the tip vortex and thus decrease induced drag. Reasons I don't think it is worth your effort: 1) The size of the tip vortex is primarily driven by the lift distribution of the wing, which is a function of planform, twist, and airfoil selection. In our case, there is no twist and the airfoil is constant (makes it "easy" to build). The rectangular planform carries a good amount of lift outboard on the wing. The low pressure above and high pressure below are going to try to equalize and thus form a vortex pretty much regardless of the tip shape. The tip is such a small part of the planform that it is going to have very little effect. 2) Differing tip designs try to reduce the induced drag. Induced drag is dominant at slow speeds, and becomes almost insignificant at high speeds compared to parasite drag. As Lee Erb has said, most design changes modify the planform. To increase speed, a better idea would be to reduce frontal area (reduces parasite drag). 3) The droop tips on many Cessnas were originally suggested by the designers to try to reduce drag. The flight test guys tried them and found virtually no difference in cruise speed. They were going to toss them, but someone from marketing happened through the hangar and thought they looked cool. As a result, they ended up on the production airplanes. Any gains in performance were mostly in the minds of the owners. For the full story, read Thompson's "Cessna: Wings for the World." 4) Anyone I've ever heard about who changed wingtip design claimed at most an increase in speed of 1-3 knots. That much can also be attributed to flight test errors, wishful thinking, and false claims made so as not to look silly. There's only one reason that I know of that would justify changing the shape of the tips: style (see #3 above). If you want yours to look different or you didn't like the originals, then live it up! The changes I have made fall in two categories: lighting and antennas. Remember I'm setting up for day/night VFR/IFR. Lighting: I could have used one of the Whelen units popular among RVers that scabs onto the wingtip and has a position light (red or green) at the front, a strobe in the middle, and a white position light at the back. There it hangs out in the airstream, producing drag. That probably would have been okay, but my composites friend thought we could make it more elegant. I had seen what he did to his Pulsar and liked it. The forward position light lens is flush with the surface at the front of the tip. After glassing, the section for the lens is cut out and the fiberglass used to help make the form to form the plexiglass lens. We haven't done this yet, so I can't comment more on it. The strobe (basic Whelen lens) will have a hole cut at the outer end of the tip and the lens pushed out it and held in with silicone sealant/adhesive. In the unlikely case of needing maintenance, the silicone will be cut out and the strobe removed. 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 trailing edge of each wingtip, halfway out. I'm using the standard Whelen tail light lens and retainer, which screws into an aluminum plate and nutplates bonded to the trailing edge of the wingtip. The shape of the wingtip has a bulge at the trailing edge to smoothly flow into the light. For position lights, I'm using auto backup lights in sockets bought at the local auto parts store. Much cheaper than Whelen bulbs. Strobes are Whelen units. Antennas: The Bearhawk isn't exactly a fast glass ship screaming for the antennas to be buried in the airframe, but there's no reason to create drag that you don't have to. I talked to Bob Archer of Sportcraft Antennas and came up with an antenna strategy. Inside the left wingtip, I will have his Model 3 antenna. With the appropriate splitter, this antenna will receive VOR, Localizer, and Glide Slope signals. In the right wingtip will be a marker beacon antenna (I haven't worked out the details of that one yet). To make room for the VOR antenna, I extended the span on the wing tip by one inch from what the newsletter said, but it may turn out that the extra inch wasn't needed. It won't hurt anything anyway. Comm signals are vertically polarized, and thus need a vertical antenna. Bob suggested that I attach a vertical, external antenna to the center cluster above the center of the cabin. Grounded to the frame, the frame and wings will help serve as the ground plane. The GPS antenna will be somewhere on top of the fuselage (details not worked out yet). The transponder antenna will probably go on the boot cowl on the bottom of the fuselage. Construction: My composites artiste was having trouble picturing the wingtip, so I made up a full size corrugated cardboard mockup using cardboard where plywood was called for in the Oct 96 Bear-Tracks. Since the wingtips on his Pulsar were all of maybe two feet long, he was surprised at the size. Bear-Tracks describes making a male mold to pull wing tips off of. We thought that a lot of unnecessary work when that would take two molds and we would only be making one tip from each. As such, we decided to go with the sacrificial mold. I bought a large block of blue foam from Spruce, and he proceeded to carve it, first into the shape of the airfoil, fitting it against the end of the wing. After that fit perfectly, he carved the third dimension (cross section) shape into the foam block. I now had a block of foam in the shape of a wingtip. Or a whale--I wasn't really sure. I had made templates to use in the carving from foam core board (art supply), using a half ellipse for the cross section. He never used them, preferring to just sand away everything that didn't look like a wingtip. I didn't argue since it came out so well. Definitely more of an artistic method than a technical method. Over this foam we laid a pile of unidirectional fiberglass at the trailing edge to build it up against hangar and fly-in rash. All of it was then covered in two layers of bidirectional fiberglass cloth. Now it sits until we get to do the finishing work, which may be a long time because the new wing jig blocks access to the tip rib. At some future time portions of the foam plug will be carved out to make room for the antenna and lights. Some portions may be left in for additional strength. One future challenge will be carving the rest of the foam to be a mirror image of the first wing tip. To attach the wingtip, we decided to let the wing skin overhang the tip rib. The foam was carved to fit inside this skin with a small relief for the fiberglass. Later nutplates will be installed in the wingtip with screws going through the overhanging skin into the wingtip to the nutplates. Note that a small additional skin had to be added around the tip rib behind the rear spar. We think this will give a cleaner installation (at least aesthetically) than having the wingtip overlap the skin as suggested in the newsletter. That's all for now. +++ #2488 From: Doug Knight Subject: Re: [Bearhawk] Wingtip thoughts... Russ Erb wrote: I can see it now, the sign on the tent next to muddy grass strip, "Foam Wingtip Carver for Hire." Without tunnel testing it is all Voodoo or is that the Experimental? I have seen some speed mods that brake the rules. Lower stall speeds and and higher top ends. Each little mod has it own unique effect. It will be interesting to see what the numbers are when Bearhawks become flying birds. I think back about Keel Boat Design and a rounded keel bottom just sucked. To much drag. Remember when Australia II whipped Dennis Connors butt. Their keel was just a wing and a modified vortex generator. +++ #2490 From: mailstuff Subject: Re: [Bearhawk] Short-Winged bearhawk Club A little sheetmetal trick to lessen scrap is to always put all of the holes in it before you cut it to length. That way you dont have holes that are too close to the end of your part (centerline of hole should be 2 times the rivet diameter from the edge of the part - minimum). A fan type rivit spacer is well worth the forty bucks for laying out rivit patterns. Drill your two end points with a number 40 bit, and cleco the rivit spacer in those holes with the closest spacing as called out for on the print. Then drill through the spacer and into your part. This gives a nice even layout without having to divide by 32nds of an inch to get the spacing even. +++ #3538 From: Todd Chisum Subject: Wingtip Fabrication Photos Photos to accompany Shelly's recent article on wingtip fabrication are now in the "files" area in the folder "Shelly's Wingtips". They are numbered in sequence from start to finish. +++ #3549 From: Russ Erb Subject: Major Milestone #32 reached! or was it #33? It's hard to tell since I never wrote the Program Management plan, so I don't know where the milestones are... The left wing of #164 has made its way to the airport. We moved it out of the garage tonight. I had to move it out to make room to build the right wing. It is now hanging on the wall of a friend's hangar at one of our local airports. The entire move went nominally. I had been able to anticipate most of the problems that we might encounter and plan around them. For the move, I borrowed a flat bed trailer from a fellow EAAer. This was one of those tandem wheel trailers you've seen for transporting cars around. It had side rails that were about a foot above the bed of the trailer. I stretched 5 tie-down straps across the trailer from one side rail to the other. These straps were what the wing rested on. Remember that the top wing skins are riveted on, but the bottom skins are ready for riveting but have not been riveted on yet. That's so I'll still have access later when I remember whatever it is I've forgotten. I used cheap 1/8" hardware store Pop rivets in each of the -4 holes in the bottom of the main spar at each center rib location. Bob and Mike recommended this to close out the nose section temporarily, because a closed section has far more torsional resistance than an open section, even if it is "almost" closed. The rest of the bottom skins were held in place by several (less than 20) 2-56 machine screws, washers, and nuts. We used 3 people to move the wing because that's how many I could dig up. We primarily held the wing at the ends near the spars. Because the edges of the skins overhang the rear spar, they are unsupported and are not good places to hang on to. The hinge mounts are about the only option. Thus, more than 3 people might not have made much difference. In our case, 2 people carried it and the third mostly stabilized it or temporarily held an end while one of us repositioned our hands. We laid it on the straps across the trailer top side down, because the top side was already riveted and would best handle the primary loads (weight). Additionally, the rear edge of the skin was better supported because of the stiffener in the flap bay and the pocket ribs in the aileron bay. We then used a bunch of other straps to keep it from moving up, sideways, forward or back. For the drive to the airport, the hangar owner drove behind me to keep an eye on the wing. We had FRS radios so that he could communicate any problems. This worked well, with him notifying me of one problem and also one warning about a bad railroad crossing. The hangar wall where we put it had a large girder running horizontally that was a C-channel with the flanges pointing up. This was perfect as we merely hooked three tie-down straps to it, held the wing in position, and hooked the other end of the tie-down strap around the wing and back to the channel. We hung it nose down because the nose skins were much stronger than the edges overlapping the rear spar. For good measure, we made sure that each strap went around the wing at a rib station for additional rigidity. We had transported the wing about 30 to 40 miles to the airport. If I had been going much farther, such as moving or driving several hours or on a crowded highway, I probably would have spent the money to rent a Ryder truck to put the wing in for more protection. The biggest shock was to walk into the garage after I got back and instead of seeing a wing about 4 feet away, I could actually see all of the way across the garage. I'll get started on the right wing sometime, but I'd also like to put that off for a little bit so that I can finish preparing Bearhawk CD Version 2 (BHCDV2). It takes a while to sort through the 1500 or so messages we've had since January. Lots more pictures of my project and all of Bill Johnson's pictures plus more. Stand by for notification. Don't ask when or that will just slow me down. You'll hear it here first. +++ #3568 From: Bion Rogers Subject: Lotsa Questions Well, I've studied the plans and the newsgroup postings and I am getting closer to starting the work. Would some of you answer some questions for me? Most are about the wing. I don't have the wing photo pak yet (I have the fuse pak) and I can't seem to figure these things out. 1. Are the rib attach angles mounted to the spar with the same rivets as the capstrip or with their own rivets? 2. I am assuming that the aileron cable that runs from the belcrank to the fuselage along the rear spar goes to the aileron belcrank on the opposite wing. Is this correct? 3. On plan 11, on the bellcrank drawing, please explain the construction of the hinge and spacertube assembly. I just can't seem to picture it in my mind. What is "AFTER WELD, INSTALL BERG. MRC R- 4FF referencing? 4. How are the ribs and attach angles located (installed) over the middle bolt head for the wing strut attach fittings? ( Web splice area) 5. Bud Davidson mentioned control surface gap seals in the 180 Pirep. Any ideas how it is done? Where can I find more information? 6. Where can I find a good reference book about lofting a fuselage of this type and size? 7. Is the end of the T21 cross tube at the main spar attach fitting flattened to fit or is it rolled down to size? +++ #3942 From: Ken Beanlands Subject: Re: Re: Fabric wings This brings up another question. What is the approximate weight of a completed BH wing with flaps, ailerons, and tanks? I'd like to build a set of BH wings, using the Christavia MK 1 dimensions for my Christavia. That way I could get rid of the rear strut and fabric on the wings while gaining flaps and wing tanks. +++ #3947 From: Del Rawlins Subject: Re: Re: Fabric wings I don't think the Bearhawk is an airplane that was meant to be scaled _down_, even in part! I'm sure there is a market for partially completed Christavia projects, seeing as how you are talking about building a whone new set of wings anyway, it isn't too much of a stretch to build a fuselage to match... 8^) +++ #3948 From: Russ Erb Subject: Re: Re: Fabric wings I didn't measure mine (too inconvenient) but I was guessing that the wing was about 150 pounds. Probably more like 175 with tank and control surfaces. This number guaranteed accurate within +/- 150 percent. +++ #6046 From: Russ and Penny Erb Subject: RE: [Bearhawk] Wing/ Spar Weight From the archives (Jan 99): "2. Weight of assembled main spar: about 22 pounds 3. Weight of assembled rear spar: about 10.5 pounds " I never weighed the (mostly) complete wing when we moved it out of the shop, but I estimated it to be 100 to 150 pounds. We were able to move it with two people but required a third to assist when we needed to reposition our hands. If that doesn't answer you question, tell me what question you're trying to answer. Russ Erb +++ #6163 From: "Collin Campbell" Subject: update on #370 Just thought I would share my excitement with the group as I now have finished my wings! Time to celebrate! This is a major milestone in the project for sure. I have 827 hrs in the project so far to date. This makes me think that Bob's projected completion time of 2000 hrs should be realistic enough. I have been working on the project for 29 months now, it's hard for me to find time every day to work on it. Would be nice if I were retired--didn't have a business to run, grass to mow, "honey-do" projects and other things that keep me out of the shop. Looking forward to getting started with the fuselage. Collin Campbell #370 +++ #6165 From: "Bill Cox" Subject: Re: [Bearhawk] update on #370 Congratulations Collin, Do you have the ailerons, flaps and tanks also finished in that 827 hours ? Bill Cox #303 +++ #6173 From: "Collin Campbell" Subject: Re: completion time From: "Bill Cox" > > Congratulations Collin, > > Do you have the ailerons, flaps and tanks also finished in that > 827 hours ? Yes, that does include ailerons, flaps completed and fitted to the wing. (they aren't covered yet, want to do all that at one time when I do the fuselage) Fuel tanks complete and installed. All the access panels with all those pesky little nut plates done. I have even made the new style wing strut attach fittings that go with the strut Bob is selling. About the only thing left on the wings is the wing tips, haven't decided on whether to make them myself or buy them. Collin Campbell #370 +++ #6178 From: "Mark and Tina Lapierre" Subject: Re: completion time Great progress. Congratulations. I was wondering about the wingtips. Not that I necessarily want to change things from the original plan, not that the bearhawk would have any difficulties with STOL performance in stock configuration, but if I'm going to go through the trouble of making wingtips from scratch, I want to either make a droop tip or a long flat tapered bottom like a Horton STOL design for a fat wing cherokee tip. The purpose of either of these designs is to keep the wingtip vortices from climbing over the tops of the wingtips so as to improve short field capabilities and controllability at low speed by keeping the pressure on the outside top of the wing as low as possible. I suppose at low speed the boundary layer would tend to stick a little better in the abscence of the wingtip vortices reaching the topside. The only negative things I've ever heard about these designs is that the droop tip restricts visibility a little bit and tends to break when bashed (so just don't bash them). The Horton type tip (installed on a cherokee) makes the stall break more suddenly (but a few knots slower) rather than just mush out. Anyone else thought about this? Mark Lapierre +++ #6190 From: Russ and Penny Erb Subject: Wingtips Another favorite recurring topic...The short answer is make the wingtips look however you want, the effect is far more aesthetic than aerodynamic. The drooped wingtip thing was started by Cessna many years ago to see if it would reduce induced drag. The flight test group tried it and decided there was no noticeable effect. Unfortunately, the marketing guys saw them before they got rid of them and decided they looked "cool". Thus, they were retained solely for aestethics and someplace to write "Cessna". What about gliders with drooped wing tips? Certainly they must be on to something...they are, but not what you think. The wings are already high aspect ratio, so there is little to be gained from an endplate. Look closely--you'll see that the wingtip is turned down to mount a wheel or skid to protect the wingtip on the ground. RV's have a form of the Hoerner tip. I've heard some guys claim to have gained a couple knots with a different design of wingtip. I always ques tion claims like that, because a couple knots change unless very carefully measured and corrected, can come from any number of factors, such as a lower density altitude (more engine power). One guy has claimed that the Hoerner tip may make things worse by increasing the camber at the tip, rather than reducing it to zero. The only things that have been shown to be truly effective in wingtip design are reducing frontal area and wetted area, both of which address parasite drag, which is dominant in cruise anyway. My wingtips will be pretty much like Bob designed them, with a slight change in size to accommodate an antenna. Make 'em however you want 'em to look, but don't think you're going to get some huge performance boost that nobody else has been smart enough to figure out in the last 98 years. They just don't matter that much. Russ Erb +++ #6191 From: "Bruce A. Frank" Subject: Re: Wingtips There does seem to be improvement when using ANY tip over the Piper Cub type bow tip. The rounded Cub type actually pulls the vortex around so that it partially blanks part of the aileron. A modified Hoerner ending in a square corner trailing edge seems very effective in leading the vortex away preventing it from rolling up over the end of the wing. +++ #6193 From: Russ and Penny Erb Subject: RE: Wingtips From: W. Shalm [SMTP:shalm@i...] > > For the illiterate and uninitiated could you please describe > exactly what a "modified Hoerner ending in a square corner > trailing edge" is? Is there an aircraft that I could look up > that uses this or do you have access to a sketch of one? Sounds > interesting. Sounds like the tip on a Bellanca Scout or an RV-6. Russ Erb #164, Edwards CA +++#6204 From: charles.k.scott@d... Subject: Wingtips From: "Bruce A. Frank" > > There does seem to be improvement when using ANY tip over the > Piper Cub type bow tip. The rounded Cub type actually pulls the > vortex around so that it partially blanks part of the aileron. A > modified Hoerner ending in a square corner trailing edge seems > very effective in leading the vortex away preventing it from > rolling up over the end of the wing. I'm in agreement with this. Years ago I happened to read an article by Barnaby Wainfan regarding wingtip designs. He confirmed what Bruce said above and went into a description of what various wingtips do for perforrmance. I spoke with him about a design for the Christavia and he carefully asked me what I expected to have happen. I told him I wasn't looking for a magic wand, that I knew enough not to expect dramatic improvements in performance, I just thought that since I was building everything, why not incorporate a wingtip design that was an improvement over the bow type, if for no other reason than what Bruce mentioned above. Mr. Wainfan agreed that keeping the vortices away from the ailerons was possible and made the following suggestion. Keep the wingtip on the same plane as the cordline, don't try anything fancy. Gently curve the outer edge of the planform of the wingtip until it's parallel to the centerline of the airplane, then carry that straight back to the trailing edge. At that point, bring it straight to the aileron paralleling the trailing edge. This leaves the outer trailing corner tip around 6 inches outboard of the aileron, so the vortex departs the wingtip at that point, not right next to the aileron. Simple and easy to fabricate. Making them was interesting. I cut a piece of plywood the shape I wanted and mounted it on the spar stubs sticking out from the wing (I left these long on purpose to anchor the wingtip). So I had to slot the plywood to fit it around these stubby extensions of the spar. I made sure the plywood rested along the centerline of the cord. Then I glued foamboard on top of the form and hacked and sanded it until it conformed to the airfoil shape and the outer planform shape. This included shaping the outer portions of the spars so they'd conform to the inner walls of the fiberlass wingtip, giving me something with which to attach the wingtips. After that I followed conventional procedures to turn the foam into a male form and laid fiberglass over it to make the top half of the wingtip. Once that was done (there's more here, I had trouble with the fiberglass, both removing it and using proper layers to get the right stiffness). But once that was done I destroyed the form and turned the wing over and repeated for the bottom segment of the wingtip. Once I had both halves, I fitted them together over the wingtip and taped them together using fiberglass. Then pulled them off and reinforced them on the inside. Finally, I finished them off using a mixture of resin and microballoons, which required much sanding, once cured. I'm not done of course, I still have to fabricate wingtip lights and strobes. Not sure yet whether I'll use strobes but it's probably a good idea even if I don't fly at night for better visibility under hazy conditions. Corky Scott +++ #6215 From: Budd Davisson Subject: Re: [Bearhawk] Wingtips I've been holding off on the wing tip conversation but, figured it was time to chime in. Russ summed it up nicely when he said it really doesn't make any difference what you use. With all of the extreme experiments with wing tips, the only things which have actually helped are correctly-designed winglets and those would make the Bearhawk look like a Beagle with its head out the window. I once had a friend with those bat-like dro0ped tips on his Cherokee 180 and he got so fed up with tryng to measure their effeciveness, he flew it with only one wing tip installed and couldn't tell the difference. Barnaby had it right: if you're looking for max efficiency make the back edge of the wing tip extend in such a way thta it puts about six inches between the end of the aileron and the end of the wing tip. That'll "help" keep the vortex off the aileron. At the speeds we're traveling, the tire size and tread is more important than stuff like wingtips and surface finish. bd +++ #6523 From: "doug" Subject: Re: What else do I need Here is a trick that I use when working alone with coiled aluminum. Get 4 medium Pony spring clamps, (the ones that look like oversived clothes pins) they are only about 4" long or so. Place two clamps on each side of the coil at 180 degrees, then clip the tape and uncoil the coil half a turn at a time, move clamps as nesessary. Reclamp and retape when through and will still fit back in the box. Doug #433 >>> 2mar02 #7686-9153 +++ #8086 From: Russ and Penny Erb Subject: Kevin's progress >Just finished final riveting of first wing structure. > > Now on to the left. > > Kevin Dudes--I hope you realize the magnitude of this statement that Kevin threw in as just an afterthought. As one of the precious few who have been there, this is a huge accomplishment. I've seen Kevin's work, and this is far from slapped together--I'm sure I'd be happy to have his wings on my airplane (although I still plan to use my own). Good work, Kevin--keep it up! I, for one, enjoy hearing progress reports like this, so I encourage the rest of you to tell us when you make some accomplishment. Don't think yours doesn't matter just because your just starting out. Tell us when you finish beating out those ribs. Shucks, even tell us when you finish the first rib! Russ Erb Currently welding clusters on station E-M, all clusters done from L-F to tail +++ #8088 From: Budd Davisson Subject: Re: Kevin's wings A note on Kevn's wings in addition to Russ's comment: I spent an afternoon going over them with Kevin pointing out all the "gotchas" in the plans. The work is far, far better than factory quality and his subtle little fixes are important. I don't know if he has summarized them and put them on the digest/FAQ or not, but no one should build these wings without the benefit of the cumulative input from guys like Kevin and Russ. There's a regular little check list of "...move this gizmo 1/16" down and the other one up, to clear the inverted framus..." that'll save some serious head scratching and frowning. bd +++ #8089 From: Tim Hickey Subject: Re: Re: Kevin's wings > A note on Kevn's wings in addition to Russ's comment: I spent > an afternoon going over them with Kevin pointing out all the > "gotchas" in the plans. The work is far, far better than > factory quality and his subtle little fixes are A list of "gotchas"? A list of "GOTCHAS"? Now my ears are really open. I have been waiting for at least one shoe to fall, and this sounds like one. Like the guy several weeks ago asking about "design issues" with the Bearhawk, I too am wanting to find out where "oversights, errors, or omissions" are located in this plane. As he pointed out, everything, except possibly the crowbar, and I might even choose to argue with him about that, has gone through some form of "evolution". And to expect that something as complex as an aircraft will not require some type of adjustment, redesign, or clarification, is a bit naive. What is needed is a method to formally let people know when an issue has been uncovered. If I were building a set of wings, and after getting close to the end of construction, discovered that there was a gotcha already built in, something that could have easily been corrected from the get-go, and something that was going to be time consuming, expensive, or difficult to fix, I would be looking to choke somebody. I was hoping that the internet and forms such as these would be a great assist to those of us who build removed from expert help. Perhaps it still can. But what is needed is open and honest discussion about "oversights, errors, and omissions". A cooling problem with an O-540? High rudder break out forces? Some tail mods? Cowl Flaps? Only small problems in the large scope of things, I am sure. But someone in charge of the Bearhawk operation needs, or perhaps should, get public and work on a way to keep everybody up to date. So why do I write this? I am not a Bearhawk builder. I hope to become one when I complete building my next house. Two years, at least. But I have built a Zenith CH-300 from scratch, and I know that information received about an "oversight, error, or omission" before constructing an affected part is well received. Tell me about it after the fact, and my blood pressure goes up. (Offered with positive thought) By the way, Good job, Kevin. Hang in there. Tim Hickey +++ #8090 From: "Del Rawlins" Subject: Re: Re: Kevin's wings > So why do I write this? I am not a Bearhawk builder. Tim, get a copy of Russ' CD and you should find the information you are looking for. There aren't any major issues of which I am aware, and I've been following this group for around 3-4 years now. What you will find, are some minor drafting glitches which have been addressed in the newsletters and here on this list. If you choose to build the Bearhawk, a complete set of the newsletters will be included in the plans, so you will have all of the current engineering notices before you start. The CD also has all of the newsletter archives, if you want to take a sneak peek. Del Rawlins +++ #8091 From: bearhwk272@a... Subject: The Little "Gotcha" List-- And It is Little. Group Attention Please ! Go to bed at peace tonight,all is well. Their are no smoking guns. Budd has let the kitty out of the bag. I will post the condensed Gotcha list in a day or two. I do not take credit for the discoveries. The builders who have past this way before have noted most of them in this forum. My project is the benificiary of other's experiences and observations. In most respects what I have done is to incorporate the "fixes" as part of the building process. I have tried to stay very close to the plans and not deviate from Bob's concept or execution. If you stand at arms length with the plans in hand it is hard to find any difference. Stand By Kevin +++ #8092 From: Russ and Penny Erb Subject: RE: Re: Kevin's wings > > As he pointed out, everything, except possibly the crowbar, > > and I might even choose to argue with him about that, has gone > > through some form of "evolution". > > Absolutely right. No design, as drawn, is perfect. The > Bearhawk is no different, although compared to other designs I > have heard about, it is surprisingly accurate with very few > required changes. > > What is needed is a method to formally let people know when an > issue has been uncovered. If you take the word "formally" out, this is already in place. In fact, Tim, you're reading it. The Bob has covered important changes in the newsletters as Engineering Notices. Any of us builders who have found what we thought were discrepancies have immediately posted them here along with suggested fixes, sometime from The Bob himself or at least confirmed with him. Interestingly enough, one of our builders identified a minor interference between the aileron cable and flap pushrod. The story goes that The Bob checked the prototype and found the same interference. While far from grounding, it could easily be done better. All of these "issues" are contained and conveniently indexed on the Bearhawk CD (as Del mentioned) (info at http://www.eaa1000.av.org/pix/erbpix/bearhawkcd.htm) for the mere pittance of $20. If you're too cheap for that or just too impatient, I'm sure you will find at least some of the issues on Del's FAQs or in Benton's (?) on-line index of the list archives. And finally, there's no substitute for good old fashioned plans study by each builder. And for Kevin, I encourage you to record your list of issues soon, before you forget. It's been long enough for me now that my memory is fading. I'm pretty sure I wrote about everything, but I can't guarantee that. It's pretty embarrassing now when someone asks a question about forming wing ribs and I can't remember what I did way back in 1996-1997. Boy, I'm feeling old... Russ Erb +++ #8093 From: Budd Davisson Subject: Re: Re: Kevin's wings Okay, calm down. What gotchas there are are tiny and already addressed in one form or the other by the group, but it would be nice to have them all condensed into one little check list that everyone has handy. We're talking stuff like moving hinge attach bolts just a tad closer together to make it easier to hinge the ailerons, offsetting little tings here and there. These aren't design errors. These are just those things that make building the airplane easier. And as for "A cooling problem with an O-540? High rudder break out forces? Some tail mods? Cowl Flaps?", lighten up. Bob runs low power on his 540 so never had it worked as hard as it was when I was flying it and it got a little hotter than normal. Plus it was a brand new engine. Big deal, so you change the outlet area or put louvers in the cowl sides. Don't forget, this is basically the same cowl as the 180. As for cowl flaps, that's just a possible option: this airplane has an operating range of 40 to 165 mph and it might, repeat might, benefit from cowl flaps on the bigger engines to cut down on cooling drag at the higher speeds. Most folks don't care whether they get that last 2 mph or not. Personally, I wouldn't add the complexity, even though I'm the one who brought it up. And about my comments about the rudder: go back and read what I wrote. The break out forces in both prototypes are light and Bob changed the size of the balance area on the rudder on all the plans. Both of the other two BH's flying have the smaller balance area but we haven't heard from them about the rudder. Bob is the only person I know who has flown both the prototypes AND the two flying airplanes so only he has a basis of comparison. I keep forgetting to ask him if there was much difference. If you want to know howt the BH flies, go to www.airbum.com and read the pireps in the pilot report section. There is so little about this airplane that isn't close to perfect that you have to sit around thinking about it to come up with something to complain about. Tim, I've flown over 300 totally different types of airplanes, close to 100 of them homebuilts, and it is the overall completeness of the BH package and the way it uses brilliant simplicity to give terrific utility in a great handling airplane that drew me to it in the first place. Back in 1995 I didn't have ten minutes in the airplane before I knew this airplane was something special. So, take a deep breath, finish your house, find a buyer for your CH-300 and start whittling on a BH, you'll never be sorry you did. bd +++ #8094 From: "Del Rawlins" Subject: RE: Re: Kevin's wings > All of these "issues" are contained and conveniently indexed > on the Bearhawk CD The official goal of the Unofficial Bearhawk FAQ is now to concentrate on answering more general newbie-type questions, like where to get plans, links to more information, etc. For more technical questions, I recommend buying the CD, consulting with The Bob and The Budd, and of course asking the list. I will continue to post some technical articles to the FAQ as I get around to it or they are submitted; based upon my current rate of updating the FAQ, I repeat, buy the CD. Del Rawlins +++ #8125 From: "Tim Anderson" Subject: RE: Re:drain holes (was rivet question) In fabric wings aircraft one puts in small water drain holes to get rid of condensation in each bay. I don't recall this topic being addressed before but...any suggestions from the group as to there utility...even in the main wing section if any condensation or leakage occur? otherwise it will pool at the rear spar flange. >>> 4sep02 #9154-11297 +++ #9272 From: Russ and Penny Erb Subject: RE: Wing Weight > Has anyone weighed a finished wing and would you tell us how many > pounds? I've said this before in more detail--I haven't weighed a wing with anything more sophisticated than the forearm scale. By that it comes up around 150 pounds. +++ #9433 From: "miknaitis" Subject: Re: wing aluminum layout Del is right about expecting mistakes and wanting some left-over aluminum, but I think that pattern would be a nice time saver (like we're not already spending thousands of hours on this). If anyone has that file somewhere, it would be great to put it with everything else in the "Files" section of this site. +++ #9436 From: Tim Subject: Re: wing aluminum layout I have a print out of this and will put it up in the 'Files' area later tonight......Also will click the notifiy group email option......My brother Dean is heading out for S&F tomorrow, told him to give my regards to Bob. +++ #9465 From: Tim Subject: Aluminum Rib Cutting Layout Upload to our files area, this info was printed from Tom's ex-website http://groups.yahoo.com/group/Bearhawk/files/Aluminum%20Layout1.jpg http://groups.yahoo.com/group/Bearhawk/files/Aluminum%20Layout2.jpg >>> 20may03 #11298-18250 +++ #14483 From: Budd Davisson Subject: Re: Question about Wing Changes When talking about the wing changes, remember that none of these are absolutely necessary, but would be "nice" if they were done. bd +++ #14492 From: Budd Davisson Subject: Re: Question about Wing Changes Incidentally, one thing that absolutely has to be done is making sure the tanks are high enough in the tank bay to support the hat section stiffeners. In the tests, it was impressive to see how much a little support changed the torsional resistance of that bay. bd +++ #14504 From: Budd Davisson Subject: Re: Question about Wing Changes > That's interesting. Is there any sort of padding material used in > between to keep the hat section stiffeners from fretting against the > tank? Yes, Bob is suggesting almost anything including laying down a heavy bead of silicon before seating the tank. My first choice would be something like a thick (1/8") rubber strip but it can be almost anything. bd +++ #15035 From: Budd Davisson Subject: Re: Results of Wing Test @AviPro > This raises the questions: Where did you THINK it would fail AND > why do you thinkit failed where it did?Planter Bob We all thought it would fail in various places outboard of the strut, which proved to be stiffer than expected and it failed in classic compression mode inboard right where that kind of thing could be expected, if it wasn't going to fail outboard; where the second top spar cap stops 33" from the root and there's an abrupt drop in cross sectional area. By extending that cap to the root the discontinuity is eliminated but the failure mode is shifted elsewhere. Probably outboard of the fitting at something around 7 g's (that's a pure guess). The important point is that with no mods whatsoever it still showed no permanent deformation at 5.7 Gs (maybe even higher because that's the last point it was unloaded) and let go at over 6.4 G's and would have gone higher but we were loading guys on the wing and they jumped up on it in no particular order and screwed up the distribution. Even without any of the mods it would have made 6.6 if we had been a little more careful for that last few hundred pounds. As it was, it was only a little over 1% short of the required utility category weight. With the mods, it's way over the limit. bd +++ #15542 From: Benton Holzwarth Subject: Order of Battle (main wing or control surfaces) I am about to the point where I need to start assembling little parts into subassemblies. I had earlier decided to approach it by building my flaps and ailerons first, as a prelude to getting into the main wing, proper. My photo-packs are out on loan to a friend who wanted to look over the fuse pictures, so I was looking through the Beartracks back issues for info on how to approach jigging up the flaps. What I ran across instead was the suggestion that the flaps and ailerons should be built after the main part of the wing, and be sized (in chord, I suppose) to match the wing. Does that jibe with how other folks have done it? Do I need to abandon assembly of the flaps/ailerons for now, and instead focus on getting the main wing together? Benton +++ #15544 From: "Dan Montee" Subject: Re: Order of Battle (main wing or control surfaces) I recently asked Bob the same question. His answer was that the hinge locations are the critical dimension and that I could build the flaps and ailerons and just not finish to the point that I could not install the hinge nut plates. I haven't started them yet. Still finishing up my rear spars. Does that make sense to those that have finished their wings? Dan Montee # 415 +++ #15566 From: pfflyerz@c... Subject: Re: Order of Battle (main wing or control surfaces) Worst case scenario, you might accidently do what I did, in which case, you would want to build your control surfaces last. I discovered, while riveting the skin on my first wing, that I didn't have it supported adequately enough at the tip. I ended up getting a 1 degree twist at the tip. Luckily the twist was a washout. After crying for days, I called Bob and he said no problem, it would probably fly just fine, maybe even better, just make sure to make the other wing to match. I did make the other wing to match, but then had to make the control surfaces to match as well. Would have been a bummer to already have the control surfaces done, but if I had to redo something to make fit, I would rather it be the control surfaces. Pat (almost a free man) Fagan +++ #15569 From: pfflyerz@c... Subject: Re: Order of Battle (main wing or control surfaces) > I recently asked Bob the same question. His answer was that the > hinge locations are the critical dimension and that I could build > the flaps and ailerons and just not finish to the point that I could > not install the hinge nut plates. I agree that the control surface hinges need to be built to fit the finished/installed wing hinge bearings. I'm not so sure that mearly assembling the control surfaces and leaving the hinge locations for later will necessarily work. You have to establish where the hinge doubler goes on the spar in order to locate the ribs on either side of it. Once the doubler position is set, you don't have much room for error on actual hinge location as the hinge bolt barely fits in the opening as it is. It would be much easier to finish the wing, then clamp the hinges to the bare control surface spar to establish where you want to put the doublers. You won't have a control surface that will fit every other Bearhawk out there, but if you are like me, and despite your best efforts, dimensions don't always work out, at least the surface will fit your wing. Pat Fagan #232 +++ #15575 From: Russ and Penny Erb Subject: RE: Order of Battle (main wing or control surfaces) And now for the opposing, yet similar, view... I built my flaps and ailerons first. However, I did not drill any of the holes in the wing rear spar for mounting the hinges prior to assembling the wings. The holes for two of the hinges were set when flap and aileron drives were installed. After the structure was assembled and the skins clecoed in place, then the other hinges were fitted to the surfaces and the rear spar in the jig. Result: The holes for the hinges are not exactly where the plans say they should be. Some may be displaced as much as 1/4 inch. But they are in EXACTLY the right position to work with the flaps and ailerons I built. Remember that any hole that must be drilled to match two parts together should not be drilled until the last possible moment. Tony Bingelis once said that when building two parts that must fit together, you can build the first part to the plans, but you'd better build the second part to fit the first part. That's how I did it. You can see pictures and commentary on the Bearhawk CD. Russ Erb +++ #16294 From: Budd Davisson Subject: Re: Wing weight > Could you give me the weight of the wings (including or excluding > the fuel tank---dry) I'm guessing about 160 pounds, but Russ can probably come closer. bd +++ #16300 From: Russ and Penny Erb Subject: RE: Wing weight Since you asked, I just weighed my wing using the modified dog-weighing method. Configuration as weighed: Bottom skin in place but not riveted No fuel tank No fuel tank bay cover Several access covers removed No flap or aileron installed No wing tip The wing is pinned to the fuselage and the strut is not connected. I stood on an uncalibrated bathroom scale while lifting the wing at the tip. From that reading I subtracted my tare (my weight without the wing). ASSUMING that the wing is spanwise homogeneous and thus the wing cg is halfway between the root and tip, then the measured weight at the tip would be 1/2 the total wing weight. If you accept these assumptions, then the weight of the wing as measured is 110 lbs (significantly less than my previous guess). Russ Erb +++ #17370 From: "Dave Roberts" Subject: wing tips I have a couple of questions on wing tips. In Beartracks they have a listing for T.Q. fiberglass supplying wing tips. Has anybody purchased these wing tips? I know Russ made his. How big of a job is that? I have never worked with fiberglass so am a little hesitant to try that. If somebody has bought wingtips, were you happy with the fit? I guess I am a little worried that if they don't fit right I might as well give a try at building my own. I appreciate your input, Dave Roberts +++ #17372 From: "t18cox" Subject: Re: wing tips I bought the Wingtips from TQ. The quality and fit was good. Bill Cox +++ #17374 From: Russ and Penny Erb Subject: RE: wing tips If you choose to make your own wingtips, my recommendation is to find a builder in your area that has worked with fiberglass before. To say "I" made my wingtips is a stretch--most of the work was done by a friend who had built a Pulsar. Russ Erb +++ #17380 From: pfflyerz@c... Subject: Re: wing tips I think the price TQ charges for wingtips is an incredible value, when you consider not just the time involved, but also the cost of materials. That said, I made my own wingtips for a couple of reasons. TQ's look great on Bob's plane, but I thought they were a little wavy on Will Graff's. I attribute that to the slight difference in wing profile that might come from "fat ribs" or whatever. I also like the looks of the slight droop of Cessna wingtips and wanted to try to copy that. I decided to buy some foam and try carving the Cessna shape. If that hadn't worked out, I would have happily bought tips from TQ. Pat Fagan +++ #17394 From: "shellybird" Subject: Re: wing tips Check out my photos from the BH files. I enjoyed tip construction! Shelly +++ #17483 From: shell Subject: Wing tips For those scratch builders out there who wish to play with some foam and glass, the wing tip photos are in the file section and the description is at Del's Unofficial Bearhawk FAQ. It can also be found in Experimenter, Sept., 2000. Shelly +++ #17695 From: "Shawn Burns" Subject: aluminum wingtips anyone? I am posing a question to the group- has anyone considered aluminum wingtips? I just reread one of Kent's articles and coupled with Budd's mention of polishing the wings started to think- all AL wings would be nifty and really shiny! I am sure that I would be sentencing myself to a long period of planishing, welding, etc, but I think it could be done and be asthetically appealling. My thoughts were 2 shallow half bowls welded together with a cone section welded in the front to smooth the transition from the leading edge to the knife edge of the joined bowls. One would then need to add a small extended pad to attach the lighting to the wingtip. I see the starting point after determining the shape to build up a male block to shape the halves over. Then weld up the seam, and polish it. I have never done anything like this, but I think it's possible- just will take some time. I would really like to do the fairings in AL as well. I think metal on the fuselage would be going to far, but I am finding that the aluminum is a really friendly material to work. Shawn Burns +++ #17702 From: Budd Davisson Subject: Re: aluminum wingtips anyone? Kent is bound to sound in on this one, but I'd probably go for pounding them into concrete or wood/fiberglass/bondo molds, half at a time. And I love the idea. bd +++ #17708 From: Budd Davisson Subject: Re: aluminum wingtips anyone? I really like the concept of aluminum wings, if not the practicality. Actually, because of the shape, I think even us rag legs could figure out how to do it without too much trouble. I'm dying for Kent to give us his ideas on the right process. I see it as: 1. Make foam plug 2. Cut foam plug in half horizontally 3. Make concrete mold from plug, or as Kent did it in one of his articles, cut wood in various shape to form the concavity, then fill in with Bondo and push plug into it. 4. Make clamping ring around the edges (configuration makes that a little hard to visualize) 5. Pound it down in there first with rubber mallet then use rubber nose on rivet gun at low pressure. For the traditional BH tip, doing half at a time means the stretch really isn't that deep. I know Kent will tell us to free form it on a shot bag and wheel but that takes too long to come up with the skill to make matching parts. The mold method seems easier for us. What about it Kent? A particularly easy way to do it would be to make them as Hoerner tips. They would take much less forming and you could probably use a piece of large diameter aluminum tubing for the edge. The more I think about it the more I like the idea of polished wings. When get get more of these things flying I think we ought to have a competition for the lightest BH. We'd probably have someone in CA doing an interior in unpainted carbonfiber: panel, seat buckets, etc. Carbon nose bowl, on and on. bd +++ #17710 From: "fourthwedge" Subject: Re: aluminum wingtips anyone? > I am posing a question to the group- has anyone considered aluminum > wingtips? Piece of cake! One of the "hands on" workshops I attended at Sun 'n Fun was metal shaping. "I" (that's me and the guy that showed me how, who had been doing this kind of thing for 17 years) made the prettiest little aluminum salad (as opposed to soup) bowl you ever saw, in about 10 minutes. Now I'll admit we did have the help of a rather large gizmo called a power hammer/shrinking machine and an industrial sized wheeling machine that cost about 5 G's, for smoothing and planishing. But, I'm sure a dedicated Bearhawker could turn out a slick pair of wingtips with just a hammer and a few dollies. Key word there would be: "dedicated"! Really, I wouldn't think the shaping would be that tough, even with a small wheel. It seems to me that the hard part would be welding the halves or quarters or however the best way to slice it might be, back together and getting it straight and smoothed out again. How about it Kent, have we got a chance? In this lifetime? I really enjoyed making my little bowl. The cowling should be a snap after doing a couple of wingtips. Whoever tries it, please take pictures of your progress. You're a cinch to make Russ's CD and the BH hall of fame. Dave +++ #17713 From: Russ and Penny Erb Subject: RE: aluminum wingtips anyone? > The more I think about it the more I like the idea of polished > wings. Have you ever MAINTAINED an airplane with polished anything? From a friend who helps maintain a polished Cessna 195, it's like the never-ending finishing job. Unlike a good paint, you can't just polish it once and leave it for years. > When get get more of these things flying I think we ought to have a > competition for the lightest BH. We'd probably have someone in CA > doing an interior in unpainted carbonfiber: panel, seat buckets, > etc. Carbon nose bowl, on and on. My money's on The Bob for that competition. I'll also be that the lightest Bearhawk will be day-VFR only. At some point, reducing weight results in reduced capability... My recommendation on the aluminum tips--if you don't want to make fiberglass tips, by the TQ tips, get your Bearhawk flying, then play with aluminum tips. That's my planned attack for fairings. Those who actually finish their airplanes are those who don't get excessively bogged down in the details. Russ "I'd rather have an essentially stock Bearhawk today than an excessively tricked out one 30 years from now" Erb +++ #17717 From: Budd Davisson Subject: Re: aluminum wingtips anyone? Marlene (AKA the AZ Redhead) and I had a polished 140A Cessna for about four years and it was no big deal, but then we live in Arizona and it was hangared. I think we polished it once during that period of time and that was just a touch up. And you're dead on about getting it flying, then mess with it. As I'm famous around my place for saying, "Perfection is the enemy of completion." bd +++ #17719 From: "Bruce A. Frank" Subject: Polished Aluminum On this subject, after polish isn't wax applied? Or does that interfere with the truly clear mirror finish? Is a polished aluminum surface ever shot with a protective clear coat? I am asking because I don't know. My experience in the metal trades has always been to clear coat to keep bright surfaces bright. How does one deal with polished planes that have stripes and painted on or stuck on logos? Bruce A. Frank +++ #17723 From: Budd Davisson Subject: Re: Polished Aluminum >> On this subject, after polish isn't wax applied? Not usually. At least I don't know anyone who waxes it. >> Or does that interfere with the truly clear mirror finish? Not sure >> Is a polished aluminum surface ever shot with a protective clear >> coat? Most people are afraid of the clear coat yellowing in the sun and/or separating. If it decides to separate, you have a real night mare. >> How does one deal with polished planes that have stripes and >> painted on or stuck on logos? You polish around them as best you can. However, the easy way is to strip the airplane, polish it, shoot the stripe and stick on the decals. From that point on, it's easy to hand polish next to decals and such. Once it's got a good polish, it doesn't take much to bring it back up. It's the first time that such a bear. bd +++ #17727 From: "Kent White" Subject: RE: aluminum wingtips anyone? OKOKOK, Thanks Russ...Budd... I would think that making the tips would not be much trouble, considering that, at that point, the builder would know layout, cutting, bending, basic forming, and riveting. If the tips have no interior ribs, then they are technically considered non-structural. If, like the Swift, they have even a couple of wimpy ribs, then "structural" they are considered to be. I only raise this point for the joining aspect. When I rebuild the Swift tips (structural) I replace the spotwelds (5052 .032 soft) with double-flush rivets on a one-to-one ratio, and they are undetectable 6 ft. away. The leading edge of the clamshell design is butt welded with the torch (factory) and from the midpoint (light mount) of the edge back it is a flange that is spotwelded. So...like the SA article I wrote on making tips, you Do Not Need to invest heavily in tooling, Power Hammer, Shrinking Machine, Wheeling Machine, Air Hammer, etc. You can use your existing aircraft building tools to do this. I am indeed trying to get the homebuilder to grasp and practice fundamental aluminum forming concepts in this exercise. (I have demo'd aluminum forming for several years at SunNFun and packed the tent.) Like Budd says, making a cavity or a pair of cavities, and working the sheet into them is the hot ticket. The whole process of making the cavities, the clamp ring, and whomping the shape is one exercise. Planishing, fitting, and joining is the second. If you wish to rivet only, then the design can cetainly accomodate. If you wish to butt weld and then rivet, why soit'ny, that can be allowed also. This process can be transcribed to Erbster for the CD, BTW. Although it would be fun to do a video.... OK...questions from the class... Mr. Frank...Do Not Clear Coat anything but your trombone, because in the weather, weather or not you hangar, that coat will Peel, yellow, get funky, and will do so far sooner than you would care to rid yourself of the whole project. Think: paint stripper, and lots of joyful hours washing it off. Wax? A really good wax is Highly recommended, as it limits water spotting, smog pitting, and chalking of the paint finish. It makes it easier to wash off da buggers, and if you get a really good wax, you can laugh at the flies bumping and skidding their asses as they land. Rumor has it also that a good wax really does help make the craft slicker through the air. It may come as a shock but none of those shiny P51's, the show stoppers, none have any Alclad left. Not one. They are all so heavily polished that it is long gone, but they Do Use Wax, and I can get the name of their best wax because I know the guys who do that on those planes. Next question....? Kent +++ #17731 From: Budd Davisson Subject: Re: Aluminum wing tip idea Cent, How about this: When making the mold, rather than making, say the bottom half of the right wing tip, you glue the right and left foam patterns together when making the mold, so you're doing both bottoms and both tops at the same time in single molds. That way the stretching is symmetrical across the mold and you don't have to worry about doing something at the root of a single tip mold to accommodate the weird stretching that would happen there. It would be like making the aforementioned salad bowl. Also means you're only making four molds. This looks like a place to use your rivet gun hammer method. I've forgotten what you call it. Does any of this make sense? bd Incidentally, I forgot: these tips are not like a Swift's, with the external flange. I'm used to flying Swifts with Bonanza tips and that's what these are like. +++ #17792 From: "Kent White" Subject: RE: Re: Aluminum wing tip idea BD, I don't know if this makes cents or not. Doing siamesed (sorry, old habit) pairs of parts might be good, depending on design of tip. If I have your concept right, then I would make only one top and one bottom cavity, each producing a joined-at-the-neck (better?) pair of parts that then need be surgically parted into top (or bottom) left and right skins. Right? If so, four molds makes no cents to me, and I am missing something. >From a forming aspect, making four tip skins my way gives distinct "individual" parts, variations in execution notwithstanding. And this is done with four cavities, and one weld-tacking alignment fixture. I would expect students of this to arrive at approximately the same degree of shape, using either "flow forming" or arm-and-hammer. Significant variations in the builder's efforts would be needed to accomplish any major difference in the tips, by either common scrutineering standard or function. I have often though that by a little hybridization, and a digital cogent electrostatic field they could simply be grown in good AK sunlight; fertilized with ripe squaw candy. Kent +++ #17796 From: Budd Davisson Subject: Re: Re: Aluminum wing tip idea Sorry about the Cent(Kent), once in a while I don't catch my spell checker before it takes over the message. Yes, Siamesed parts. Two molds (one top, one bottom). Set it up for butt welding. 3003? Maybe not. It's not a very deep stretch, so might not work harden on first pass so would get sturdier part from other alloy. Does flow forming make it easier to get smoother surface (planishing) than doing it by hand? Start out with .050? I'm really fascinated by the aluminum tip concept. If I were willing to take the time from other projects (notice I didn't say, if I could find the time: we all have the time to do anything, if we want it badly enough) I'd make a set just to see if I could do it. bd +++ #17814 From: Russ and Penny Erb Subject: RE: Re: Aluminum wing tip idea Uh, guys? Let's think about the geometry for a second... Because of the airfoil shape, the top of one tip is NOT the bottom of the other tip. This became quite clear while we were carving my foam. The only plane of symmetry between the tips is the rib plane. There is no way you can take a right wingtip and make it fit (properly) on the left wing tip. You need separate molds for left and right (unless you know some geometry that I'm totally missing here). Unless you're talking about forming the top of both wingtips out of the same piece of aluminum and then cutting it down the middle--likewise the bottom--something like making a whole wing but leaving out the middle 32 feet. Did I just catch on to what you were saying? Russ "Gee, I'd sure like to learn aluminum forming someday" Erb +++ #17815 From: Benton Holzwarth Subject: Re: Aluminum wing tips idea The way I saw it was two molds, each a symmetrical 'canoe' reflected across the 'keel'. Form the boat, then cut into pieces along the keel to form left and right top halves. Repeat for the bottom halves with a different canoe. The idea was that, being symmetrical it'd be easier to get them similar. But someone else pointed out that no one would ever notice anyway -- and they're right, in service they'll be 30 feet apart. Heck, you could make one sheared and the other Hoerner, and most people wouldn't notice. Benton 6may03 +++ #17834 From: Budd Davisson Subject: Re: Re: Aluminum wing tip idea I think the Erbman misunderstood, so the doublespeak is working. If he goes back and reads more carefully, he'd notice we said 1. make foam plugs for each wingtip, glue them together butt to butt. 2. Slice them horizontally so the two tops and the two bottoms are one piece. 3. Use each part to to make a mold that would look a little like a party tray. One mold makes both bottoms, one mold makes both tops. 4. Pound them full of aluminum (or pour them full and mill out the excess :-)) 5. Cut the party trays in half. 6. weld the appropriate halves together. Viola, or fiddle/cello, whatever, two wing tips. bd +++ #17840 From: "Bruce A. Frank" Subject: Aluminum Wing Tips Long time ago I mentioned and drew a rough diagram of a modified Hoerner/Sheared wing tip. This discussion about tips has gotten in out in the shop trying to create a pattern to cut the aluminum for such a tip. Well, well well, trying to wrap poster paper around a rib and then mark it and cut it smoothly to make metal marking cutting pattern has turned into a more difficult problem than I thought it would be. A friend, at least I think he is a friend, has suggested that I turn to my CAD program, lay out the airfoil coordinates, create a solid and insert angled planes to create a printable pattern. To do this I have to become more skilled in my CAD program AND get the coordinates of the USA35B airfoil. Sometime back I saw posted some where, may have been in RAH, a web site that had coordinates of dozens of the more popular airfoils. Does anyone here know where I might find that site? Bruce A. Frank +++ #17848 From: "Kent White" Subject: RE: Re: Aluminum wing tip idea OK, now that erbman is definitely up to speed: New game plan: make molds, cut 1/8 thick blank, attach clever truflate fitting to edge, heat blank, inflate hot blank to fill cavity, trim. Or, make molds, make blank, heat blank, blow blank into mold with hot argon, trim, fit, join. (Aluminum blowmolding is not noo, just misunderstood.) or, make conc mold, seal blank tightly to top of mold, affix suitable rubber pad to blank with small charge attached, toss in neighbor's all-purpose pool, detonate, retrieve part and parts of mold, and hope pool don't leak (this time). Kent +++ #17858 From: "zipppydoggg" Subject: Re: Aluminum wing tip idea OR, 4. Make a stack as follows, upper mold, aluminum sheet, rubber ring that seals aluminum sheet to a second aluminum sheet, lower mold. Bolt generously around parimeter. Inject high pressure water (you do have a new high pressure water washer don't you?)between aluminum sheets. PS don't forget to put small hole in molds to let air out as water enters and displaces aluminum sheets into mold. Made more, sell to friends, buy new glass cockpit stuff, smile :-) +++ #17859 From: Budd Davisson Subject: Re: [Bearhawk] Re: Aluminum wing tip idea Great idea, Bruce! But, I can see a problem in getting enough pressure. What about a variation on the grease gun approach that's been used to form smaller parts? Use a hand pump to pump the water, grease, hydraulic oil, between the sheets (getting it between the sheets calls for an interesting pressure galley capped with a zerk fitting). It would be slower but it would be much easier to produce the needed pressure. Kent, would this kind of set up stretch the aluminum sufficiently or would 3003 still rebound too much? And how much pressure would you estimate? The volume could be a problem. bd +++ #17863 From: "Kent White" Subject: RE: [Bearhawk] Re: Aluminum wing tip idea BD, now we gotta get you up to speed; Our video "Fluid Forming" shows the process of " > Make a stack as follows, upper mold, aluminum sheet, rubber ring > that seals aluminum sheet to a second aluminum sheet, lower > mold. Bolt generously around parimeter. Inject high pressure water > (you do have a new high pressure water washer don't you?)between > aluminum sheets. PS don't forget to put small hole in molds to let > air out as water enters and displaces aluminum sheets into mold." The pressure washer delivers both pressure and volume, way ahead of a hand pump. And no grease to waller in. Really a slick way to make parts, and to ... bend tubing. heheheh Kent +++ #17869 From: "Kent White" Subject: RE: [Bearhawk] Re: Aluminum wing tip idea The $149 pressure washers are running 1500 to 2000 psi. They will ruin the thin aluminum sheet metal in the blink of an eye, but Bearhawkers are known for improving on things. Kent +++ #17883 From: "Kent White" Subject: RE: Re: Aluminum wing tip idea BD, Smoothness comes from tooling and application. I have done 5052 soft wingtips with barely detectable marks, right out of the molds. Polish-able? I think so. Thickness? .032. Just like Swift. Heavier material goes to Waco and Pilatus and North American... It is a slick method. Kent +++ $Id: 2.1-Wing,v 1.12 2003/05/21 14:52:43 bentonh Exp $