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Thread: Wing Inter-Rib Bracing...What to do???

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    Buzzcola777's Avatar
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    Wing Inter-Rib Bracing...What to do???

    Gents,

    Still in the process of ordering items for the covering. Looking at the drawing #12451, Piper shows the method of inter-rib bracing.
    I've looked at a bunch of pictures on the Web and some wing have them some don't...

    AC43.13-1B / Poly Fiber and other reading materials instruct you how to zig zag this between the ribs and how to knot them at each crossover point. The bracing is designed to keep the ribs from deforming during the fabric shrinking process.

    Was this inter-rib bracing done only for the old piper wings? Do I need it or not? What do you guys do?

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    mike mcs repair's Avatar
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    Only do it on wimpy or bowed old ribs


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    Buzzcola777's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    Only do it on wimpy or bowed old ribs


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    That's what I thought!
    Thanks Mike!
    Dan

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    Hardtailjohn's Avatar
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    I always do it. It's a matter of maybe 3 ounces on the whole airplane? It wont hurt anything at all. Cheap insurance. We recommend it in the manual as well. https://stewartsystems.aero/wp-conte...essed-copy.pdf
    John
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    I am with Mike. On a Cub, after shrinking, you can reach in with a needle and move a rib straight.

    However, on the Taylorcraft I am working on, a needle pressure would break a rib, so I used the newer synthetic stuff. Still didn’t get it perfect. I can get a Cub wing dead straight without them. In fact, I bet I couldn’t move a rib under the cover if the tapes were in there.
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    Steve Pierce's Avatar
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    Yea, you can move it but can you keep it straight while you stitch it. Why wouldn't you use the inner rib bracing tape?
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

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    If I were buying a plane and didn't see it i'd wonder what else didn't the builder do
    Staying alive in an airplane has a lot more to do with mastering ourselves than mastering the aircraft.

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    Once the ribs are dead straight and the fabric shrunk, that first coat of dope will capture the ribs, making stitching mindless. You can still snap it loose if you see a crooked rib.

    MT - don't buy mine when I croak. Dead straight ribs but no bracing. Buy the new Cub - it came covered with bracing. I have threatened to recover the wings just to get those ugly curves out of the ribs, but instead I just fly the socks off it.
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    Buzzcola777's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    Yea, you can move it but can you keep it straight while you stitch it. Why wouldn't you use the inner rib bracing tape?
    Steve,
    Not that I don't want to use it, I was just wandering why some people use it and some don't... On the Smith Wing the cover is extended about 24'' from the LE...Is it still required?
    Dan
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    Buzzcola777's Avatar
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    Quote Originally Posted by Hardtailjohn View Post
    I always do it. It's a matter of maybe 3 ounces on the whole airplane? It wont hurt anything at all. Cheap insurance. We recommend it in the manual as well. https://stewartsystems.aero/wp-conte...essed-copy.pdf
    John
    Thanks for the manual John!
    Nice videos BTW! Look like Smith Wings?
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    Your ribs look the same as mine from Backcountry. If so? They're way more rigid than old Piper ribs. You shouldn't need to stabilize them, especially with extended LE metal.
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    Steve Pierce's Avatar
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    Quote Originally Posted by Buzzcola777 View Post
    Steve,
    Not that I don't want to use it, I was just wandering why some people use it and some don't... On the Smith Wing the cover is extended about 24'' from the LE...Is it still required?
    Dan
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    I doubt you need the rib bracing from looking at your ribs and the extended leading edges.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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    Hardtailjohn's Avatar
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    Quote Originally Posted by Buzzcola777 View Post
    Look like Smith Wings?
    Yes they are. I sent you a PM.
    John

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    skywagon8a's Avatar
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    Dan, A tip when covering your wings. Put the covering on the bottom first, shrink it enough so that it won't move when the final shrinking is done, then stitch the ribs forward of the aft edge of the extended top leading edge. Then cover the top, shrink and do the full rib stich. It's easier to get your hands in there to stich the bottom under the leading edge.

    I agree with Steve, the trailing edge of the extended leading edge is attached where the X bracing is placed. The whole idea of the X bracing is to hold the high portion of the rib from sliding sideways when the pressure of the shrinking fabric wants to pop the ribs sideways. With that extended leading edge there are no unsupported high spots on the ribs.
    N1PA

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    mike mcs repair's Avatar
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    Quote Originally Posted by skywagon8a View Post
    , then stitch the ribs forward of the aft edge of the extended top leading edge.
    There’s no use stitching just the bottom of ribs.

    Some planes have no bottom of rib,or any fabric attachment

    There’s really zero reason to stitch bottom at all...

    you usually skip it when replacing a bent rear spar in a covered Piper wing.

    Unless you plan on flying inverted.....



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    skywagon8a's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    There’s no use stitching just the bottom of ribs.

    Some planes have no bottom of rib,or any fabric attachment

    There’s really zero reason to stitch bottom at all...

    you usually skip it when replacing a bent rear spar in a covered Piper wing.

    Unless you plan on flying inverted.....
    Then why is the fabric sewn to the ribs under the gas tank? It is to stabilize the fabric to prevent wear from abrasion and flexing. It also helps to stabilize the ribs, reducing their ability to flex and crack. Stitching the bottom of the ribs is easy, takes very little time and just makes the fabric and ribs a bit more secure.
    N1PA
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    Steve Pierce's Avatar
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    I also saw someone drill holes in the extended leading edge so they could easily stitch the ribs under them. There is also a way to cross stitch them as well.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  18. #18

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    My
    Ext leading edges are drilled for lacing.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Buzzcola777's Avatar
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    Quote Originally Posted by skywagon8a View Post
    Dan, A tip when covering your wings. Put the covering on the bottom first, shrink it enough so that it won't move when the final shrinking is done, then stitch the ribs forward of the aft edge of the extended top leading edge. Then cover the top, shrink and do the full rib stich. It's easier to get your hands in there to stich the bottom under the leading edge.

    I agree with Steve, the trailing edge of the extended leading edge is attached where the X bracing is placed. The whole idea of the X bracing is to hold the high portion of the rib from sliding sideways when the pressure of the shrinking fabric wants to pop the ribs sideways. With that extended leading edge there are no unsupported high spots on the ribs.
    Thanks Sky! Very good tip!!

  20. #20
    mike mcs repair's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    I also saw someone drill holes in the extended leading edge so they could easily stitch the ribs under them. There is also a way to cross stitch them as well.
    That’s how I do it


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    Buzzcola777's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    I also saw someone drill holes in the extended leading edge so they could easily stitch the ribs under them. There is also a way to cross stitch them as well.
    Steve, are you referring to the blind stitching method ?

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    mike mcs repair's Avatar
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    Quote Originally Posted by Buzzcola777 View Post
    Steve, are you referring to the blind stitching method ?
    no, normal stick top to bottom

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    Click image for larger version. 

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    I am doing the Poly Fiber "Island/palm tree/rabbit" stitch now. It works under the tank, using the curved needle, if you can't get to the inside for some reason.

    I have seen experimental airplanes with no rib stitching. I assume it works, but we need to put the stitches in or get a field approval. I personally cheat on the vertical fin; no more stitches there. Well, I will put them in, but they break right away.

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    Steve Pierce's Avatar
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    Quote Originally Posted by Buzzcola777 View Post
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    That is how I like to do it.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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    I’m with Steve on this technique.
    Though I have found it best to fabricate your own needle for this operation.
    piece of welding rod (or coat hanger) pound one end flat and drill a hole for thread.
    Most commercially avail needles are really stiff and won’t bend.
    Its often necessary (or helpful) to be able to tweak and tailor the needle to your particular situation, stitch space, obstruction etc..
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    Hardtailjohn's Avatar
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    Yep, blind stitch the bottom and run them together just like a normal stitch, then when you get past the leading edge, start a normal stitch. Works great and pretty quick.
    John
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    Quote Originally Posted by Buzzcola777 View Post
    Steve,
    Not that I don't want to use it, I was just wandering why some people use it and some don't... On the Smith Wing the cover is extended about 24'' from the LE...Is it still required?
    Dan
    Click image for larger version. 

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    So you're not drilled for lacing through the extended metal? Are you planning to? If not, are you comfortable with all that lift area being secured by a thimble full of #4 PK screws and glue?

    What are other guys doing with extended LE metal? The reason I prefer metal is for how lift works the fabric in that area as the plane takes off and lands. I'm pleased that the area is laced on my wings.
    Last edited by stewartb; 01-09-2021 at 06:07 AM.
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    cubpilot2's Avatar
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    Mine is drilled and laced. Just make sure that the holes are large enough and positioned over the cap strip by about 1/3 to eliminate a sharp edge that could cut into the lacing.
    Ed
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    It looks like Buzzcola's metal is one piece outboard of the tanks? I've never seen that. No 90° flange over the upper spar cap. Maybe I just can't see it?
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    mike mcs repair's Avatar
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    Wing Inter-Rib Bracing...What to do???

    Quote Originally Posted by stewartb View Post
    It looks like Buzzcola's metal is one piece outboard of the tanks? I've never seen that. No 90° flange over the upper spar cap. Maybe I just can't see it?
    I’ve always wanted to do it like that.. then add a l angle backwards from spar top and rivet to top skin


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    Quote Originally Posted by stewartb View Post
    It looks like Buzzcola's metal is one piece outboard of the tanks? I've never seen that. No 90° flange over the upper spar cap. Maybe I just can't see it?

    Here is a better photo of the extended Leading Edge Cap from inside.
    Click image for larger version. 

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    I'm not really planning to drill it.
    Dan

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    Quote Originally Posted by Oliver View Post
    I’m with Steve on this technique.
    Though I have found it best to fabricate your own needle for this operation.
    piece of welding rod (or coat hanger) pound one end flat and drill a hole for thread.
    Most commercially avail needles are really stiff and won’t bend.
    Its often necessary (or helpful) to be able to tweak and tailor the needle to your particular situation, stitch space, obstruction etc..
    Exactly with I did today with 3/32'' brass rods. Thanks for the tip Oliver!
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  34. #34
    mike mcs repair's Avatar
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    Quote Originally Posted by Buzzcola777 View Post
    Here is a better photo of the extended Leading Edge Cap from inside.
    Click image for larger version. 

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    I'm not really planning to drill it.
    Dan
    I would tie top of spar to leading edge with a L angle. That gives allot of strength to wing.

    Compare a uncovered PA-12 wing with partial wrap leading edge to a full wrap -18.


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    When enlarging the tank bays for Atlee tanks in a -12 you add full-wrap leading edges. The angle sounds like a good idea.

    FWIW. Cessna ribs are about 18" apart and the flush rivets affixing the skin average approx 1" centers. My Cub wing ribs are approx 14" apart and the lacing in approx 3" centers with the LE metal's PK screws dividing that in a few rows. There's a lot of tug on top of a Cub wing in slow flight. Think about your screw spacing if you're not lacing through the metal.

  36. #36
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    Quote Originally Posted by mike mcs repair View Post
    I would tie top of spar to leading edge with a L angle. That gives allot of strength to wing.

    Compare a uncovered PA-12 wing with partial wrap leading edge to a full wrap -18.


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    Mike,
    How would you do this? By adding and L angle between the ribs?
    The ribs are already braced to the spar and Leading Edge...
    Dan

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    Quote Originally Posted by stewartb View Post
    When enlarging the tank bays for Atlee tanks in a -12 you add full-wrap leading edges. The angle sounds like a good idea.

    FWIW. Cessna ribs are about 18" apart and the flush rivets affixing the skin average approx 1" centers. My Cub wing ribs are approx 14" apart and the lacing in approx 3" centers with the LE metal's PK screws dividing that in a few rows. There's a lot of tug on top of a Cub wing in slow flight. Think about your screw spacing if you're not lacing through the metal.

    On this wing the Pop rivets (not screws) are spaced 3 inches apart...Is it good enough?
    Dan
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  38. #38

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    I don't know the answer to that. I have an overhead video of a Cub with slats landing. How the wing fabric flips from scalloped down to pillowed out as it transitions from flight to ground is surprising. That video reinforced my preference for extending LE metal but made me wonder how much force is trying to separate the wing surface from the ribs. I have no idea how to determine when enough is enough but I'd prefer to err to the safe side. No criticism of your wings, just sharing a thought.
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  39. #39
    mike mcs repair's Avatar
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    Quote Originally Posted by Buzzcola777 View Post
    Mike,
    How would you do this? By adding and L angle between the ribs?
    Dan
    yes, and screw to spar with the AN530 screws, and normal screws or (pop?)rivets to top skin
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  40. #40
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    [QUOTE=mike mcs repair;794305]I would tie top of spar to leading edge with a L angle. That gives allot of strength to wing.

    Compare a uncovered PA-12 wing with partial wrap leading edge to a full wrap -18.


    I think that this is a very important point.

    IMHO
    With the extended leading edge installed without any other anchoring other then with screws to the ribs; damage to the ribs will eventually occur.

    A PA-12 wing is very easily twisted due to the design of the leading edge. This allows it to flex more in response to turbulence then a PA18. Pick up one end of a bare PA12 wing and you will quickly see how easy it can twist and you will also see buckling of the leading edge skins as you do. You will learn to handle it with care.

    A PA-18 wing with the majority of the leading edge locked to the spar, is much more rigid. Enough so that the “wash out” needs to be preset when building. This almost creates a type of “box spar” which is highly resistant to torsional or twisting forces.

    Extending the leading edge without this support will leave the wing with same ability to flex or twist when in turbulence or heavy loading. This twisting action with the extended metal will cause similar and more pronounced buckling of the skins and over time, could cause the screws or rivets at the cap strip to loosen or tear out completely. I think that this will be even more accelerated if the stitching to the fabric is not present.

    My opinion is that locking the leading edge to the spar is vital at a minimum, especially with the heavy gross weights which we often experience.
    I also feel that the stitching is well worth the time. The only problem is that the skin for this particular project needs to be loosened from the ribs to drill the holes, which need to overlap the cap strip.

    I like the extended leading edge and have it on my 180 cub.
    It is installed as an addition to the standard piper skins; which lock to the spar along with stitching.
    I have just completed recovering them after 20 plus years in service. There was no looseness or damage observed.
    Ed
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