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Thread: Light wing build

  1. #1

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    Light wing build

    Well I have researched SC.org, google, etc. etc. and decided to start a light wing building thread to try and get some of my questions answered. Many of the threads I followed ended without conclusion. IE whatever happened to the carbon fiber wing build? Did it fly? How much did it weigh? I don't really need the answer to that, it was just an example of how some of the threads went along and then no "ribbons on it" so to speak.

    I'm attempting a 1320# gross weight super cub build based on a 1977 totally bare fuse I have. I have built tail pieces (six) from scratch. I have a box of "schneider" stamped ribs (3 piece type for the main wings). Control surfaces will be scratch built. So my parameters are safety, and lite, lite, lite. At this point I'm mainly interested in conventional construction, not carbon fiber etc. I am of course planning the usual "lightning" methods. No electrical at all, 6" wheels (looking for cheap wheels), single puck (I have the cleaveland calipers), bungees, no interior, No rear seat (if thats what it takes), narrow deck o-320 (I have firewall forward <300# measured).

    The wing: Like the tail this will have to be mostly scratch built. I want to base it on the PA-18 with flaps. I'm not interested in speed so minimal ribs would be fine. I'm think 13 ribs/wing. I have purchased D&E front and rear spar blanks.

    Questions:
    1. I would like to make the leading edge skins (other than tank area that would be .025) from .016 2024 T6. Dis regarding dents etc. would this be strong enough? .020 adds about 4# to leading edge. 8# if trailing edge requires thicker. This question comes because of a comment Mike made concernig 2024 being stronger than stock 3003.

    2. How about .016 for the trailing edge? To weak for supporting flap hanger/hinges? If to weak maybe double up for a few inches in that area?

    3. The D&E wing uses a heavy sheet of aluminum under the tank bay as a "drag strut?" to replace the tube going through the fuel tank. Actually in stock wing it's two tubes since there is the "welded to the tank" tube and the actual drag strut tube passing through it. What does everyone think about the concept both strength and weight wise of the torque plate vs drag strut tube? If it wasn't any heavier I would want to incorporate that "torque plate" idea and avoid the more complicated fuel tank construction.

    4.Using the extruded compression (D&E) parts is tempting but it looks to me that the original type square tube compression struts would be lighter. Maybe not with all the extra little parts.

    5. I am looking at Christian Sturms site for diagrams but find some are not there for the PA-18-150 as per the parts book. Does the Northlanmd CD have all those missing diagrams like 14387, 14389 concerning the LE skins?

    Comments? Thanks

  2. #2
    Bugs66's Avatar
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    As far as the D&E style tank bay, it is working well for me and several other D&E wings out there. Ideally you want your tank to rest on top of it for stiffening. My tank is on straps that lay flat on tank plate. Probably overkill but wanted mostly so I have something to cinch down the tanks and immobilize them. My tank takes up the entire profile of the middle rib and is 30" wide. I ended up with 22gal usable. As far as weight difference, not sure what the drag tube and other parts weigh in comparison to tank plate. Might be a wash.

    For the aileron/flap hangers, I really like the way the CC Sport Cub does it. These are also similar to the D&E hangers except D&E are horseshoe shaped instead of CC straight (looks better). I know either of these are lighter than stock steel.

    Go with the carbon fiber tank covers, or you can just fabric over it like some others have done.

    For the LE skins, my web site has drawings 10630 and 10631. That shows you the profile you want.

  3. #3

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    will a 13 rib wing take a 0-320s power? I thought thats why they switched to 16?

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    Quote Originally Posted by tempdoug View Post
    will a 13 rib wing take a 0-320s power? I thought thats why they switched to 16?
    I don't remember who said it but I believe it was one of the "gurus" so I trusted the remark that the ribs had to do with top speed and not gross weight or (and I'm sketchy on this part) "power". If your correct that 150 horse requires 16 ribs then so be it otherwise this is being built for "climb" not speed.

  5. #5
    behindpropellers's Avatar
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    If I were given the task of lightening a set of wings I would change all steel parts to Ti. Flap and aileron ribs would be hydroformed and cut out. The J-5 wings have aluminum bolts going into the compression struts.

    Tim

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    The Carbon Cubs only have 13 rib wings and the leading edge doesn't wrap all the way to the spar on the bottom. I may be wrong but I think the early j-3s had something less than 016 for the leading edge and didn't go all the way to the spar top or bottom.

  7. #7

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    Easy to set the gross at 1320. Not so easy to get the empty weight at 800 or less to make it work.

    I built some wings with 14" rib spacing, ditched he intermediate leading edge rib and used .020 2024T3 leading edge. Stamped ribs are heavier than the ones with aluminum cap strip. Carlson ribs look to be pretty light. You can buy the T cap strip from them and build your own and save $$$. I used aluminum drag

  8. #8
    Roger Peterson's Avatar
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    This is how I am trying for a lightweight wing.
    P1000287.jpg
    Roger
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    Marty57's Avatar
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    I'm with Roger; wood might be lighter. I talked to Tom at Wag this summer and he agreed, the lightest way to go is wood. Now, I know, lots of pros and cons out there but there are a lot of aerobatic aircraft with wood wings. I weighted a wood rib complete; just under 7 0z. Piper advertised Cub ribs at 8 oz and stamped ribs are likely heavier. It will be interesting to weigh a finished, uncovered wood wing vs metal wing. Mine will have flaps but are built exactly the same as Rogers except my flaps and ailerons will be wood. Should be fun to know the weight. I should be done with the wings in a few months less the fuel tank.
    Marty57.
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    For bugs: Did D&E have in mind that the tank would be mounted rigidly to the "tank bay" and contribute strength? I have the D&E wing book and it kind of looks that way. It describes tank flanges riveted to shelf. The bottom sheet is .040 6061. I remember you decided to suspend the tank which I think is a good idea to reduce leak potential and improve crash-worthiness but did you determine that the tank was not a part of the wing structure for sure? I would definently like to build that part of the wing as you did avoiding the strut. How does the 44 gals work out for you?

    Super11: the L21 with 125 horse had .016 3S (modern #3003) al with 13 ribs and I read that 11 rib wings exist on some of the Italian? ones. I believe the L21-125 has LE that wraps from bottom of spar to top with flanges top and bottom that screw to the spar caps.

    Don: I'll be happy with 950# if I can get it. Worst comes to worst I can re-up the medical but I gotta try.

    Rodger and Marty: both of you have beautiful wood wings. Rodger I bet yours will come in under 80#. I plan on the Schneider ribs at this point (falls under the "run-what-ya-brung catagory) and Marty I weighed the 3 pieces making up a "flap" station rib and they came in at 11 oz. This would make my stamped rib wings weigh 6 lbs (total for 26 ribs) more than what you measured for wood. My weights are not totally apples to apples since I still have to come up with 4 little flange connectors and rivets to make my ribs a "whole" rib so prolly be more like 13 oz each.

    behind propellors: I bought some ti for my firewall (.020) and plan on making the firewall part out of it but I can't weld it so using it for other parts is not in the cards unless it's straps or the like. I have a bunch extra. When I went to look it up it was a little confusing. For the firewall it has superior heat specs but I found a lot of differing opinions about it's other uses unless advanced tooling was available.

    As happens often when someone asks a question online I don't think I asked my questions correctly. Reading over everything I think I am looking for comments about the design more than material types. Like buggs tank for instance. Even "lite wing" might be wrong as Piper's original supercub wing seemed in my research to be thought of as the lightest wing going so I'm not really trying to reinvent that, I just want to get as close as I can to that. . Don's idea of the Carlson extruded "T" section as a basis for ribs would be good if I did not already have these that I have. I would still like to hear real life experiences with the .016 LE skin and also if it would be ok for the false spar cove at the rear of the wing??. The pa18-150 used .020 (LE) according to my notes. I noticed that Bill R. did NOT use extended leading edge skins after originally talking about it in some posts so I think those have the thumbs down plus I like the idea of turning LE flanges top and bottom that screw to the spar caps. That seems strong.
    Last edited by qsmx440; 12-24-2010 at 02:34 AM.

  11. #11
    Iflylower's Avatar
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    DW needs to weigh in here on design. Look at his build thread. Although expensive, I think CC has the lightest stamped ribs. DW also did the 13 ribs and lots of lightening holes.
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    Has anyone ever come up with a way to combine the compression strut, flap hanger and wing rib all into one unit? That would reduce the parts count and weight one would think. That is a beautiful wood wing Roger, Wag Aero?

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    Wow. All thats old is new. Followed up on your dw suggestion and I had looked at those posts/pictures in the past but before I was giving much thought to "wings". dw's posts/pictures are very informative. CC ribs, looks like salvage compression struts & other stuff. His final weight 1110 WITH bush wheels, aluminum floorboards and interior and electric on panel? starter/battery maybe? Aluminum prop, 360 (must be heavier than my narrow deck). Weighed my Senenich 74/52 and came up with 30#. Probably have to go wood (12#?) plus if the rest of the fuse/cover is light mine will be nose heavy anyway. I wanted a carbon fiber Powerfin prop like my Quick has, but after talking to the factory they don't want to build one for direct drive engines. Power pulses are more like sledge hammer blows compared to engines running at 6000 rpm and geared down. I remember some discussion about drilling the spars but don't really remember what the conclusion was. The LSA carbon cub did it in a picture at least, spinners spars are not drilled but I think he is building for standard weight or more. If my memory is correct apparently it's ok past the strut attach but not on the cantalever area inboard of the strut (anyone know for sure about that, hole sizes, locations, etc. If I could sell these ribs I have, maybe the CC ribs would be an option but I will probably take the weight hit over other options (wood, Carlson, Dakota, CC etc. ) which would save 6-8 lbs. Nowhere else is the phrase "penny wise, pound foolish" more appropriate than in aircraft construction. For the rest of my life I have to leave a gallon of gas home on each flight because of my ribs! But the trade off is spend another 3000 on ribs (actually have to earn 4000+ more or so to pay the 3k) or another year building ribs (with other obligations) and I would spend the money lightening the nose (CF cowl, electronic ignition, etc. if I were going to bust the budget. Another interesting thing about dw's posts, I think I gathered he did that build in less than two years. I'm trying to do that too. The fuse and stamped ribs go a long way towards making this more like a kit and this time around I'm happy to do that. I won't be having bush wheels. If I didn't say it before this A/C is to be maximized for climb (from 3000' runway with trees everywhere) and not off-runway use. I am trying to bring it in under 21 K and so far with fuse, legs,spars,ribs,FWF forward (narrow deck/hollow crank, 6 tail parts (through tacked), used jack screw, 2 single puck calipers, (the stuff listed below under "weights")I'm at 14k. I'm scrounging while building for other parts. In the end I'll have to spend some real money for cover paint ($3200)

    If anyone is interested:
    Bathroom scale weights so far:
    57 narrow deck/hollow crank with all accys incl carb heat,headers& muffler, including heavy (delco remy?)starter and internav alternator (both to be removed) = 300# (I checked this twice because I didn't believe it)
    bare fuse, single puck clevelands with lines and bolts, 5" cessna 150 nose wheels/spacers/nuts (freebees for hangar use, but looking better and better all the time budget wise ), stock legs, EMT (might replace these EMT shock items cabane and shocks, Unfinished seat base 170#
    Schneider ribs (28 each, 3 piece, w/25 extra nose ribs) 25#
    fwf engine cowl all fasteners & big spinner (salvage painted) 20#
    aluminum prop w/bolts 30#
    struts 40#
    Engine mount (from memory,didn't write it down for some reason) 7#
    That all equals 592 so far which if I have a max target weight of 950 leaves 380 lbs for controls, wings complete, tailwheel, cover. Not much! I can lose alternator,starter, and 20# from the prop from above weights and maybe spend part of the budget on Carbon fiber engine cowl/nose bowl (10#?) for additional savings of 60#? bringing total so far to 532#. Many compromises are in order and mission does not include "running with the big boys".
    Someone said "800#" was max for LSA. There is a max empty weight formula for factory built LSA. I am allowed to set my own gross weight for experimental. Empty weight does not fit into it. Don't think I could fly it if empty weight was 1319 and gross weight was 1320 but it would (I think) be legal under the rules. 370 useful load would do it for me for poking holes in the sky and the occasional $100 hamburger.

  14. #14
    Bugs66's Avatar
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    Those wood wings sure are pretty. Here is a link to the thread on various wing weights for comparsion: http://www.supercub.org/forum/showthread.php?27341
    The problem is some are weighed with covering, or tanks and some without. My left wing panel weighed 88lbs with tank, lid, and square tip.

    The D&E manual called for bolting tanks to floor wich I wasn't fond of. You would have to weld flanges to the tanks. I wasn't into that and preferred straps.

  15. #15
    spinner2's Avatar
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    Quote Originally Posted by qsmx440 View Post


    Questions:
    1. I would like to make the leading edge skins (other than tank area that would be .025) from .016 2024 T6. Dis regarding dents etc. would this be strong enough? .020 adds about 4# to leading edge. 8# if trailing edge requires thicker. This question comes because of a comment Mike made concernig 2024 being stronger than stock 3003.

    2. How about .016 for the trailing edge? To weak for supporting flap hanger/hinges? If to weak maybe double up for a few inches in that area?

    Comments? Thanks
    My Carbon Cub kit uses .016" 2024 T3 for the leading edge skins and 2024 T3 of .025" thickness for the false spar.
    "Fast is fine, but accuracy is everything." Wyatt Earp

  16. #16
    WhiskeyMike's Avatar
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    I've had several modified (Restricted category) J-3's with 135 and 150HP. Stock wings with 18 tanks and full ribs to the end with spill plates. The only issue in high AOA and high powers settings during banner towing was with the inboard ribs near the trailing edge getting beat up, so we added 2 extra behind the rear spar inboard, or used a stronger trailing edge. Same with 600 Stearman. Gotta look at the particulars. Aluminum wing struts?? We also had an aluminum honeycomb floorboard, front only in our 180 J-5 with brake cylinders under the front rudder pedals. J-5 with 180 and big borer prop, no electric weighed 989 without any real though to save weight. Had pretty heavy Stits covering and paint.

  17. #17
    Dave Calkins's Avatar
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    Whatever you do, keep in mind:

    "...worry about the ounces and the pounds will take care of themselves..."

    I would think the first thing would be to get rid of the Schneider ribs. Eliminate a fuel tank. Do Aluminum lift struts, or at least J-3 style rather than -18. Lose the bungees, go to a stiff leg instead. Baby tailwheel. Jerry Burr uses the shortest bolts possible and few washers. ("...ounces....pounds will take care of themselves...").

    also, for sure do a partial wrap of the leading edge skin. For a light airplane, no need to do full wrap all the way to the spar.....even though full wrap screwed or popped to the spar is stronger.

    Also, consider that any "dings" from ground handling or even piloting mistakes will likely destroy a very lightly built wing. CC's stuff is nicely made and very light, but CC-style very-lightweight drilled spars, super-light stamped ribs, aluminum fittings, etc. don't take damage like a stock Cub with an ash wingtip does.

    Always a compromise.

    ".....ounces....pounds will take care of themselves..."

    Always a compromise, so you need to prioritize.

    Maybe you don't want a SuperCub. Maybe something else?

  18. #18
    DW's Avatar
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    I used .016 on my leading edge like the carbon cub and .025 in front of the tank a little extra stength for setting gas cans on, all 2024-t3. With out bush wheels and a stock gear maybe catto prop and every thing else your doing 950 should be no problem. my wing weigh 70lbs complete ready to bolt on. carlson ribs are built very well but they are heavy, I bought a sample rib from most everyone and CC weighs the same as a stock rib no one else came close. mine should be 1070lbs by the time I get to Valdez.

    DW

  19. #19
    Roger Peterson's Avatar
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  20. #20
    Roger Peterson's Avatar
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  21. #21
    Roger Peterson's Avatar
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    I had the wag drawings, but I went back to the orig piper drawings. Had a friend cut out the wood parts on a CNC wood mill. Made my jigs from the orig piper and started from scratch with wood from Wicks. Put Dakota Cub leading and trailing edges on it and put a quit blanket under the leading edge fab. Then covered With SS and really liked it. All I had ever used before was Stits.
    Roger
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  22. #22
    Dave Calkins's Avatar
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    Been flying a Wag-Aero Cuby. Wood Wing. The wing leading edge radius is larger than Piper. The Aviat Husky used the same airfoil section as Cuby/Wag. I can't say anything bad about it.

    This Cuby has 0-290D2 Lycoming. Just got new Exp. pistons and fresh cylinders from Lycon. All reports are that it RIPs! It was pretty good before with tired cylinders and Gurney flaps. about 1000 lbs. empty. on 31's with Baby Buswheel.

  23. #23
    Tim's Avatar
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    Dave, how long are the Gurney flaps. Inquiring minds want to know

  24. #24
    Dave Calkins's Avatar
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    Quote Originally Posted by Tim View Post
    Dave, how long are the Gurney flaps. Inquiring minds want to know
    Non-flapped Cuby. Gurney flap/Wickerbill goes from wing root to aileron Inboard end. It hangs down about 3/4 of an inch. They are presently on the ailerons, too. But...the aileron rigging has to be so tight to keep them rigged for the loads (upward pressure from the Gurney flap loading the trailing edge) that the ailerons are very stiff. So they'll be coming of the ailerons soon:
    Attached Images Attached Images

  25. #25

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    I often fly a 160 Super Cub with 13 rib wings. Its paperwork shows 1050 empty weight, and it is a screamer with a cruise prop. I am going to assume it is legal, because it was cared-for by one of the most careful mechanics on the west coast.

  26. #26
    C-FIJK's Avatar
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    Nice work Roger and Merry Xmas to you and your family
    Gerry Marcil

    Every day spent flying is a great day !

  27. #27
    Roger Peterson's Avatar
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    Merry Christmas to you and your family Gerry. Hope you have a good Christmas. Been watching all your posts of your hunting and looks like you are having fun this winter.
    Roger
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  28. #28
    Steve Pierce's Avatar
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    Quote Originally Posted by Dave Calkins View Post
    Been flying a Wag-Aero Cuby. Wood Wing. The wing leading edge radius is larger than Piper. The Aviat Husky used the same airfoil section as Cuby/Wag. I can't say anything bad about it.

    This Cuby has 0-290D2 Lycoming. Just got new Exp. pistons and fresh cylinders from Lycon. All reports are that it RIPs! It was pretty good before with tired cylinders and Gurney flaps. about 1000 lbs. empty. on 31's with Baby Buswheel.
    Dave, Is that the world famous fish spotter's old Cub you showed me last spring?
    Steve Pierce

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  29. #29
    D.A.'s Avatar
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    I don't have any documentation to prove it but a local Cub old timer told me that a wood spar J3 was 18 pounds lighter than an al spar ship.

  30. #30
    Dave Calkins's Avatar
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    Steve Pierce, yes it is! He is one good guy! Much loved by all! And, wooooohh, that girlie!?!! Sheila, she is!!!

    DAVE

  31. #31
    Darrel Starr's Avatar
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    The Wipaire 2000 lb kit allows 13 rib wings. As I recall hearing, Paul Claas's 160 hp Alpha Cub has one 13 rib wing and the other is 16 rib. I think the point when Piper went from a 138 mph to a 153 mph "never exceed speed" was when the PA-18-150 got 16 ribs.
    Darrel
    Last edited by Darrel Starr; 12-24-2010 at 11:49 PM.
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  32. #32
    DW's Avatar
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    So my new cub does about 85/87 mph so I should have went with a 10 rib wing---Damn to late now.

  33. #33

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    I'm planning on flaps (standard size and fabric covered control surfaces) , solid gear with big soft wheels was mentioned. Has anyone ever tried that? If so did straight gear weight savings offset wheel weight? Where the leading edge doesn't wrap all the way I assume it's only the bottom that doesn't go all the way and the top still has a downward 90* (actually 105* I think)flange attached to the spar cap with 3 pk screws in each bay. I saw in the Stewarts video a wing (Colt? I think) that they covered and some of the LE had a partial wrap. I believe it was the one panel outboard of the strut. So I'm thinking .016 along the leading edge except tank bay 32"? which will be .020 and .025 along the whole trailing edge false spar. The aluminum D&E spars with Schneider ribs will be laid out 13 ribs per wing per buggs site. I will purchase the sheet aluminum for the TE and LE next week and bend it myself. I would still appreciate more discussion about the tank area, strut through the tank or bottom "torque" plate. I know bugs likes it and I like the idea of not having the strut inside the gas tank. BUT spars fail by twisting I have read and since the support is only on the bottom is it as strong as the strut? Also I'm wondering if that big piece of .040 sheet is as light as the strut and pipe thru the tank. I can answer that with a little research. DW if I may ask how did you decide how much material and where to cut out the spar web? When I purchased my spars I had 6' of "H" spar spacer material sent along. I have noticed in several pictures and in the Piper drawings that the spar web attach fitting to the fuse wing hangers looks to be the same "H" spacer aluminum material. Am I correct in that observation? I originally thought there was an outside re-inforcing plate of steel on both sides of the spar web??>
    Here is an interesting wing failure test: http://www.youtube.com/watch?v=Ai2HmvAXcU0 . Whats interesting is it fails almost everywhere simultaniously. That means they are not carrying any extra weight around for the life of the aircraft when there is a weak link. That would be the gold standard. Dave C. I know building light and compromising is less safe and not as strong. The FAA made the weight rules and life established my budget. I figure I'll rebuild wood or CC ribs after I ground loop this thing in the first ten hours after I get my Tail dragger endorsment. Seriously that is why I'm getting as many thoughts as I can on this. I don't mean to dismiss any ideas and am weighing all of them. If I had my druthers I'd be building a CC kit. Thanks for all the participation in this thread and Merry Christmas ...dave

  34. #34
    Dave Calkins's Avatar
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    My point about the CC wing was simply that not everyone is aware that very lightly built stuff is great for flying, but can't take a little 'hangar rash' or ding like the "heavy" stock stuff. And certainly cannot be flipped back rightsideup, re-lift-strutted and propped and reflown like a SuperCub. It is NOT NOT NOT a safety issue, the light airplanes are plenty SAFE!

    qsmx440, consider that every bit of your struggle to save weight elsewhere is offset by the ribs you have chosen.

    What do YOU weigh? Can you save there? How about less fuel, fewer or no interior panels, less floor, fewer instruments, lighter prop, no boarding or fueling steps, fabric seat bottoms rather than wood or composite or springs, no cowling, minimal baggage area, fewer windows, remove the "extra" fuselage bracing diagonals that some folks have added to a Cub.

    The snowmachine racing crowd once echo'ed "...anywhere there is steel, use aluminum..." to save weight. I think we skipped that and have moved right to Carbon Composites.

    The partial leading edge wrap I had in mind is identical to the SuperCub leading edge outboard section. It does not wrap to the spar, neither top, nor bottom..........carbon fiber skin would be great in this location.

    I hope this is food to promote more thinking.DAVE

  35. #35
    Roger Peterson's Avatar
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    Dave, How much improvement did you see with the gurney flaps
    Roger
    Based at O8XS. Sweeny Texas (Winter)
    Finlayson Lake, Ontario (Summer)
    I plan on living forever.......so far, so good !!!

  36. #36
    Dave Calkins's Avatar
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    Roger, they work for this unflapped Cuby.

    I did some testing and posted the data some time ago. The improvements are for real. I'd like to do more testing to get more accurate or precise data.

    D

  37. #37
    Roger Peterson's Avatar
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    Thanks Dave, just read it all. Will try them in the spring on the float plane.
    Roger
    Based at O8XS. Sweeny Texas (Winter)
    Finlayson Lake, Ontario (Summer)
    I plan on living forever.......so far, so good !!!

  38. #38
    cubdriver2's Avatar
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    What about a carbon fiber leading edge, has anybody messed with that or carbon fiber ribs, what about the fuel tank.

    Glenn

  39. #39

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    Quote Originally Posted by cubdriver2 View Post
    What about a carbon fiber leading edge, has anybody messed with that or carbon fiber ribs, what about the fuel tank.

    Glenn
    If you a SC.org member go to photo gallery's and search user name "gander". He has some great pictures of CF work. Ribs and leading edge of carbon fiber. This is kind of an example of what I said in the first post. The pictures are good and I found some of his posts talking about the build but I wasn't able to find out how it flew or the weight or any specs. I think I recall the wings came in at 66# but I really don't remember. Looked strong as heck.

  40. #40
    Bushwhacker Air's Avatar
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    What about a carbon fiber leading edge
    Like this??

    CF Leading Edge Profile.jpg

    It has 45 deg weave sandwich that gives it incredible torsional stiffness, thereby eliminating nose ribs. It can be bonded or riveted, and can be joined to make one long leading edge. Heat the seam to release the bonding tape between pieces to disconnect the for repairs.
    Last edited by Bushwhacker Air; 12-26-2010 at 10:09 AM.
    Chris Hatin
    Bushwhacker Aircraft Company, LLC
    www.bushwhackerair.com
    Properly trained, a man can be a dogs best friend...

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