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Thread: Broken wing tip bow - J3

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    irishfield's Avatar
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    Broken wing tip bow - J3

    Well I've stopped enough to see the monitor!

    Got in a hurry and pulled the cub out to remove a boat from the hangar and then while swatting black flies and pushing her back in I caught the wingtip bow (just ahead of the rear spar while moving backwards) on the door frame and broke it without really tearing the fabric open. The wood? has snapped and is still somewhat joined but in the shape of a V inwards about 1.5 inches away from where it's supposed to be.

    What is the recommended plan of action to repair the tip bow.

    Thanks guys!

    Wayne

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    JP's Avatar
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    Wayne, can you post a picture? It would be interesting to see what the resident experts will recommend.
    JP Russell--The Cub Therapist
    1947 PA-11 Cub Special
    www.bloomerrussellbeaupain.com

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    Broken tip bow

    Tip bows in good condition take will take a fair amount of abuse. Are you certain it has not deteriorated? I've seen a lot of wavy and fractured bows that have simply dry rotted. You can cut the fabric along the centerline of the bow and peel back the fabric and splice the wood. A baseball stitch will close the opening, which is then taped and finished.

    Ron

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    irishfield's Avatar
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    I think it's just that I hit it almost exactly mid span between supports and it cracked it. I had a pretty good pull going on to come off the grass..up a slight incline and into the hanger when I heard the crunch and the airplane ver'd one way. The inside of the wings are like new...with shiny varnish, all steel painted and clean. Would think the bows where similar but of course can't see them.

    I did notice a small patch in the fabric at exactly the spot that broke...wonder if the previous owner cracked it and cut a small hole to look and maybe glue?.

    Thanks for the what to do...any other suggestions...will post a couple shots but they don't show the wood moved as the fabric pretty much popped back into place.

    Wayne

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    irishfield's Avatar
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    Steve Pierce's Avatar
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    You can also go to the aileron bay rib, pull the tape off, cut the fabric outboard of it keeping the stitches intact which should keep your fabric tight. Replace the bow. Depending on covering system you can use a glue joint over the rib and then add a tape and no one will know. I so-called friend pushed my Clipper into a truck and broke the bow worse than yours. I called him when I had the wing ready to come off and he had a hard day and couldn't come help because he was sitting in his Lazy Boy. Needless to say he is no longer my friend. I just painted the tip with dope and rubbed it out and you couldn't tell.
    Steve Pierce

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    Will Rogers

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    irishfield's Avatar
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    Thanks Guys...wish you were closer, as I'd get you to do the repair....it's just making my stomach turn everytime I look at it and I'm not a fabric man. Do have a local AME that just finished covering a set of SC wings, so guess I better get him to bring his 71 yr old eyes over and have a boo.

    Cheers,
    Wayne

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    JP's Avatar
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    Wayne-relax; fabric is not a big deal. Once you give it a go you will be surprised at how uneventful it can be.
    JP Russell--The Cub Therapist
    1947 PA-11 Cub Special
    www.bloomerrussellbeaupain.com

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    irishfield's Avatar
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    Quote Originally Posted by jrussell
    Wayne-relax; fabric is not a big deal. Once you give it a go you will be surprised at how uneventful it can be.
    Thanks JP...I have covered lots of fabric Flaperons for Murphy Rebels...so I'm not totally lost in the situation, just not thinking I want to tackle a "splice" job and trying to match the paint so it looks right. My preference is banging down aluminum and getting someone else to shoot the paint.

    Cheers,
    Wayne

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    Most bows are drilled, and attached to spars with crummy little screws. The screws rust, the holes seep moisture, and the bow falls apart. A good bow can withstand a hit, and is actually designed to spring back. Not legal, since it was not original, but I do everything I can to avoid big holes in a new bow, and put varnish in any necessary holes prior to assembly. Seems like we are always hitting something with the wingtip! Lots more careful with those wings with strobes on them!

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    Quote Originally Posted by T.J. Hinkle
    Wayne:
    I've done a lot of repairs just like yours. Its not a big deal. Just grab a sharp pocket knife, cut the fabric in the center of the bow, CAREFULLY fold it back. Duct tape it in position. Replace the bow. Remove the Duct tape, fold the fabric back in place, glue small strips of fabric on to the top fabric, pull the fabric as tight as you can down to the bow, glue it to the bow. Do the same thing to the bottom fabric, stagger the small strips of fabric from the top ones, glue it to the top fabric. Glue a piece of 3" tape along the cut line. Grab your heat gun, CAREFULLY reheat the fabric to remove the wrinkles. I've done it lots without having to repaint. Watch the color of the paint, it will change, but it will not release, unless you overheat it.
    Remember, God hates a Coward! Go for it.
    Steves idea also works.
    THANKS T.J. !! Wayne

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    irishfield's Avatar
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    BTW...do i have to stand thru the paint/dope? before I start cutting and gluing?

    Wayne

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    I may be wrong but that probably won't stop me from arguing about it.

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    Quote Originally Posted by S2D
    You could remove the tape from the damaged area, carefully slit the fabric enough to allow access to the damage, apply quality wood glue, pull back to proper contour and add aluminum doubler. Hand stitch fabric retapeand paint as necessary. Be back in the air in the time it takes the glues to dry and it will be as as strong as new.
    Brian, would that be the exact verbiage on the 337?...

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    Quote Originally Posted by FlipFlop
    Quote Originally Posted by S2D
    You could remove the tape from the damaged area, carefully slit the fabric enough to allow access to the damage, apply quality wood glue, pull back to proper contour and add aluminum doubler. Hand stitch fabric retapeand paint as necessary. Be back in the air in the time it takes the glues to dry and it will be as as strong as new.
    Brian, would that be the exact verbiage on the 337?...
    I guess I'll have to get out my Canadian repair manuals and see what they call for. Do they use 337's up there?
    Could probably even use the same approved data that people use to replace 1025 tubing with 4130.
    Maybe similiar wording that people use when they repair their cracked fiberglass wingtips.

    dangit cuby now you're gonna make me have to start putting TJ's disclaimer under my posts
    I may be wrong but that probably won't stop me from arguing about it.

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    FlipFlop's Avatar
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    Quote Originally Posted by S2D
    Quote Originally Posted by FlipFlop
    Quote Originally Posted by S2D
    You could remove the tape from the damaged area, carefully slit the fabric enough to allow access to the damage, apply quality wood glue, pull back to proper contour and add aluminum doubler. Hand stitch fabric retapeand paint as necessary. Be back in the air in the time it takes the glues to dry and it will be as as strong as new.
    Brian, would that be the exact verbiage on the 337?...
    I guess I'll have to get out my Canadian repair manuals and see what they call for. Do they use 337's up there?
    Could probably even use the same approved data that people use to replace 1025 tubing with 4130.
    Maybe similiar wording that people use when they repair their cracked fiberglass wingtips.
    Actually, I'm surprised no one has mentioned replacing the wood with thin wall conduit...

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    T.J.'s Avatar
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    Cuby:
    I did mention that in a different thread.

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    There is another thread on that, PVC and CPVC included.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

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    S2D's Avatar
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    I'm surprised no one has mentioned the need to inspect the spar for damage due to the untested side load. especially on a wood spar at the wing attach fittings. The airplane could probably fly for years with a damaged wingtip bow, but if the spar is cracked, it may kill you in a matter of days even with a brand new bow installed.
    I may be wrong but that probably won't stop me from arguing about it.

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    S2D's Avatar
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    Quote Originally Posted by FlipFlop
    Brian, would that be the exact verbiage on the 337?...
    Just curious Cuby- what part of FAR 43 Appendix D (b)(1) covers wingtips?
    AC 43.13-1B Ch. 1 Section 4 Para 1-36 would cover the repair.

    Aren't you glad its snowing like crazy here and I have nothing better to do than find someone to argue with??
    I may be wrong but that probably won't stop me from arguing about it.

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    irishfield's Avatar
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    Thanks Brian, TJ, Flip flop, Steve, Bob and JRussel.

    No 337's up here. Fix her to normal standards and carry on. Even the owner can do 6" patches without a mechanics blessing. Wonder if you can add a bunch of 6"rs together LOL! I'm heading north with my floater docks and airlift for the seaplane on the big trailer. so I'll have to worry about it when I get back.


    Thanks again everyone,
    Wayne

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    FlipFlop's Avatar
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    Quote Originally Posted by S2D
    Quote Originally Posted by FlipFlop
    Brian, would that be the exact verbiage on the 337?...
    Just curious Cuby- what part of FAR 43 Appendix D (b)(1) covers wingtips?
    AC 43.13-1B Ch. 1 Section 4 Para 1-36 would cover the repair.

    Aren't you glad its snowing like crazy here and I have nothing better to do than find someone to argue with??
    Got me there, looks self-explanatory to me, says "fabric and skins"...

    Went and looked at Harold's SC a couple of weeks ago, lookin' real good...

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    FlipFlop's Avatar
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    Quote Originally Posted by S2D
    You could remove the tape from the damaged area, carefully slit the fabric enough to allow access to the damage, apply quality wood glue, pull back to proper contour and add aluminum doubler. Hand stitch fabric retapeand paint as necessary. Be back in the air in the time it takes the glues to dry and it will be as as strong as new.
    FAR 43, Appendix A(b)(1)(xxi), Repairs involving the substitution of material...

  27. #27
    S2D's Avatar
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    I knew I shoulda said doubler and left the aluminum part out.

    substitution - I always thought that meant of the actual part, not the reinforcement.
    I may be wrong but that probably won't stop me from arguing about it.

  28. #28
    FlipFlop's Avatar
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    Quote Originally Posted by S2D
    I knew I shoulda said doubler and left the aluminum part out.

    substitution - I always thought that meant of the actual part, not the reinforcement.
    Brian, you're graspin' at them dang straws again... In this case you're substituting aluminum for wood... You have transferred the strength from the wood to the aluminum, thereby substituting aluminum for wood... The elbow's connected to the knee bone... Or sumpin' like that ...

  29. #29
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    Glue some popsicle sticks to it and duct tape the hole and your done.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

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    irishfield's Avatar
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    Quote Originally Posted by Steve Pierce
    Glue some popsicle sticks to it and duct tape the hole and your done.
    A "Red Green" repair with Duct tape...I can handle that! LOL

  31. #31
    S2D's Avatar
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    Yea Cuby I know
    I may be wrong but that probably won't stop me from arguing about it.

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    I have a friend with a Tiger Moth. He said the previous owner repaired the wings with an electric glue gun and popsicle sticks.

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    Well, two things: First you don't need a 337 if it is a minor repair. I don't believe the bow is structural. Second, if this is hangar rash, then the spar is probably OK, but I'd have a look whilst in there. Expect the end to be about as rotten as the bow - they all seem to get that way. On recover (the whole wing) we usually wind up scarfing new wood out there, with varnish in all holes. The bow is designed to absorb shock - to protect the wing - and the spar is real skinny where it attaches, so it too can absorb a lot of shock.

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