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Thread: Fabric Airworthiness

  1. #1
    jimboflying's Avatar
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    Fabric Airworthiness

    How is the Airworthiness of the fabric on an airplane usually determined at each annual inspection?

  2. #2

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    A long time ago cotton fabric was tested using a Seyboth or Maule tester. As far as I can tell, the only legal test for Dacron is to cut a strip out, take the dope off, and give it a pull test. Almost nobody does that; you can count on Dacron to last between 25 and 50 years if well cared for and with sufficient silver.

    If the surface looks ok, go out in sunlight and look up through some inspection holes. If you see lots of daylight or lots of all lit up pinked edges, recover.

    I just heard a horror story - brand new mechanic was doing an annual. Took all the bolts out and had them tested and re-cad plated. Bet that was a $10,000 annual. Pick your mechanic wisely. Get references.
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    Richgj3's Avatar
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    I agree with Bob. In fact the check list that Legend requires for the annual condition inspection says inspect for cracks etc. etc. No punch test.


    Rich

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    Steve Pierce's Avatar
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    Polyester fabric is a lifetime fabric and should not fail unless the raw fabric is exposed to UV. The Maule tester will tell you if the fabric is good although not recognized by the FAA. Like Bob posted the only test te FAA recognizes is the test where you remove a strip of fabric and do a pull test.

    I look at the condition of the finish and for exposed fabric. It might look like hell but if it has silver on it should not rot. I dealt with a 90 hp Super Cub that was covered in light fabric back when it was legal. It started tearing at the stringers and longerons. A friend just tore her Super Cub down that was covered in 1980 because it kept tear at the longerons and some places on the wings. She applied tpaes to the tears but finally decided she wanted a nice airplane and tore it down for recover.
    Steve Pierce

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    Will Rogers

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    txpacer's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    A friend just tore her Super Cub down that was covered in 1980 because it kept tear at the longerons and some places on the wings. She applied tapes to the tears but finally decided she wanted a nice airplane and tore it down for recover.
    I put a Maule tester on the fabric in several places before we stripped it. It was good every time, except for the big ringworm the tester left in the dope. The problem was the fabric splitting where it rubbed something underneath. It was 40 year old Ceconite and dope.

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    Steve Pierce's Avatar
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    Quote Originally Posted by txpacer View Post
    I put a Maule tester on the fabric in several places before we stripped it. It was good every time, except for the big ringworm the tester left in the dope. The problem was the fabric splitting where it rubbed something underneath. It was 40 year old Ceconite and dope.
    That is the same thing that was happening on the 90 hp Super Cub. I guess that constant drumming does start working stuff. Where were the problem areas?
    Steve Pierce

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    We lose the back and underneath of the left gear leg first, then see hairline cracks on both gear legs, followed by the stabilizers and wing trailing edge in the slip stream, and finally after a very long time cracks along stringers and longerons.

    Rarely see the fabric split except in the interior. Stearman gives us problems on top in the slipstream and along stringers. None of it is ever an airworthiness issue.

    A neighbor has a PA12 that looks like it has no silver from looking inside the fuselage. I am kinda after him, but it sits outside, and so far no fabric failures. I have seen unprotected Dacron turn into white powder. I wouldn't sign that one.

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    If you have more duct tape on the wing than fabric might want to start saving money for a cover job in a few years. I agree with the others a Maule tester is not appropriate for polyester fabric unless the aircraft manufacture requires it. My cub is starting to split the middle horizontal tape on the left side below the window. I will hopefully get it fixed this year. On a side note I heard that the new Ortex fabric needs a sample cut out and sent in ever so many years for a certified aircraft can any one confirm or have I been misinformed.
    DENNY
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  9. #9
    wireweinie's Avatar
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    Maule tester is actually appropriate for any typical fabric. All fabric must maintain 75%(I believe that's the correct %) or better, strength of old cotton. As long as it passes the Maule punch, it has enough strength left to be legal, unless fabric manufacturer says otherwise. This is assuming common sense, such as no tears, damage, or bare spots with UV damage.

    Also keep in mind that UV rot will be more prevalent on the upper surfaces. Punch testing the bottom of a wing makes little sense unless you have extremely poor landing skills.

    Web
    Life's tough . . . wear a cup.
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  10. #10
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by DENNY View Post
    .... is starting to split the middle horizontal tape on the left side below the window.
    DENNY
    that's always the first part to crack, especially with 180 horse and paddle prop....

    I always silicone the fabric on inside to that stringer top side and bottom to try to prevent that... (after covered, painted and paint has fully cured)

    left side....

  11. #11
    hotrod180's Avatar
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    FWIW a buddy of mine had a Luscombe with old "irish linen" cover on the wings--
    the fabric was fine, even after many many years, but the (cotton?) stitching was failing.
    It (rightfully) made him nervous so he recovered,
    installed a set of wing tanks while he was at it.
    Then bumped it from an A65 to an O200--
    it's quite the performer!
    Cessna Skywagon-- accept no substitute!

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    If I understand it right AirTech system has the UV barrier in the primer therefore silver not required. If that’s the case maybe that’s what they used on the 12 you are talking about.
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    A UV barrier really ought to block sunlight. No, his aircraft was covered using the Ceconite process in the 1970s. I got him to smear some Ekofill in the worst spots.

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    Richgj3's Avatar
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    I owned a modified Fleet 16B, known as the Flaglor Hi Tow. Ken Flaglor built it up in 1957 and covered it with Irish Linen. Around 1980 or later the wings failed the punch test Next year the fuselage was done. When we sold it in the early 90’s the cover on the tail was still good. It was always stored inside when we had it.

    Rich
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  15. #15
    CenterHillAg's Avatar
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    The wings on my Cub were covered in 1968 in Irish Linen, still look good inside and outside today.

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    cubdriver2's Avatar
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    There is a flying 1950 Pacer up here with the cotton it left the factory with.

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  17. #17
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by hotrod180 View Post
    FWIW a buddy of mine had a Luscombe with old "irish linen" cover on the wings--
    the fabric was fine, even after many many years, but the (cotton?) stitching was failing.
    It (rightfully) made him nervous so he recovered,
    installed a set of wing tanks while he was at it.
    Then bumped it from an A65 to an O200--
    it's quite the performer!
    have heard of people re-stiching wings, then taping and repainting... was common in cotton days.... not so practical now....

    but part of an inspection is looking for broken wing stitches and plucking at a few.

  18. #18
    Steve Pierce's Avatar
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    Haven't got the exact hours since recover but probably between 5-6K hours and 28 years. Drummed through the fuselage fabric on the right side, top longeron.
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    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  19. #19
    RaisedByWolves's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    Haven't got the exact hours since recover but probably between 5-6K hours and 28 years. Drummed through the fuselage fabric on the right side, top longeron.
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    Uh oh. Better start putting that spare fuselage together


    Sent from my iPhone using Tapatalk

  20. #20
    Hardtailjohn's Avatar
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    Quote Originally Posted by jimboflying View Post
    How is the Airworthiness of the fabric on an airplane usually determined at each annual inspection?
    The simple answer is that each fabric system has a section in their manual that states how to inspect their fabric.
    John
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  21. #21
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    Haven't got the exact hours since recover but probably between 5-6K hours and 28 years. Drummed through the fuselage fabric on the right side, top longeron.
    Click image for larger version. 

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    that an odd spot.... wrong side, and hidden from the sun even.....

  22. #22
    txpacer's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    Haven't got the exact hours since recover but probably between 5-6K hours and 28 years. Drummed through the fuselage fabric on the right side, top longeron.
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    I don't see a stick, this time
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  23. #23
    Steve Pierce's Avatar
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    Quote Originally Posted by txpacer View Post
    I don't see a stick, this time
    Just used to much when it was new.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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    skywagon8a's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    Haven't got the exact hours since recover but probably between 5-6K hours and 28 years. Drummed through the fuselage fabric on the right side, top longeron.
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    Judging from the appearance of the pinked edges, that fabric and tapes were not installed correctly. The tape is supposed to protect from this type of separation by doubling up the fabric thickness in possible wear areas. That being said, it did last 28 years and it was a pressure/wear location that failed, not the fabric.
    N1PA

  25. #25
    Steve Pierce's Avatar
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    The tape is installed along the longeron unlike the way Piper and Cub Crafters does it. The fuselage fabric wore on the longeron and eventually wore through. They rib stitched both ribs on the vertical which probably pulled the fabric tighter around the longeron. No telling if it had an effect on this or not.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

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    Quote Originally Posted by cubdriver2 View Post
    There is a flying 1950 Pacer up here with the cotton it left the factory with.

    Glenn
    Did someone paint it with enamel to supposedly toughen it up?
    You can't get there from here. You have to go over yonder and start from there.

  27. #27
    skywagon8a's Avatar
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    I put a Widgeon back in service which had been stored in a hangar on Long Island (ISP) for 50 years with Irish linen on it's surfaces. It was still in excellent condition.
    N1PA

  28. #28
    cubdriver2's Avatar
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    Quote Originally Posted by N86250 View Post
    Did someone paint it with enamel to supposedly toughen it up?
    It was bought new from Piper by my friend Roger and has stayed in the family, one owner till 4 years ago when he died at 96. Roger was a friend of Clyde Smith Sr. Roger told me shortly after getting it home that he added a coat or two of the same color dope because he thought that Piper had cheated him on the finish. It has been flown all those years but never left outside. It has lived in a drafty homemade farm hangar with logs as rafters it's whole life when not flying. I flew in it 20 years ago and it looked like new.

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

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