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Thread: Wrinkles in my fabric

  1. #1

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    Wrinkles in my fabric

    My wings look normal before flying, but wrinkled like this after. The structural integrity has been inspected. Is this the sign the wings need recovering?

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  2. #2
    wireweinie's Avatar
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    Is this a new recover job? Is this a new airplane to you? Is this a 'warm weather' airplane recently moved to a cold weather area?

    Web
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  3. #3

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    It's a newer plane to me. Had it about 7 months. It has been stored in a hanger in my area for last 15 years. Was not flown much. The recover does not have many hours on it but is old.

  4. #4
    wireweinie's Avatar
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    Just from the pics, it looks like the cold shrunk the airframe more than the fabric (cold day?). Did the wrinkles go away once it's back in a warm hanger?

    Web
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  5. #5

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    It was a colder day for sure. Went out in the morning. Yes the wrinkles go away but my hangar is not heated or anything. Next time I go fly they will look normal. I am concerned they could be "flapping" while in flight.

  6. #6
    wireweinie's Avatar
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    Still warmer inside the hangar. One of the real fabric guys on here can talk to you about maybe ironing it again for a little more tension.

    Web
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  7. #7

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    If it’s polyfiber I’ve seen it happen before when someone uses a heat gun to shrink the fabric and not an iron, guys could get away with it using dope because it keeps shrinking as it ages but poly doesn’t.
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  8. #8

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    Thanks for the input gentleman. Maybe I'll try the heat gun.

  9. #9
    wireweinie's Avatar
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    NO!!!! As PA-22 said above, that may be what led to this in the first place.

    Don't use a heat gun on most fabrics. You need to use an iron to shrink it correctly. After it's sprayed with dope, there is a trick or two to put a little extra shrink on it, if needed. Some of the other guys on here can do magic with fabric, so listen to them.

    For you fabric guys, didn't MCS Mike use parchment paper or something between the dope and the iron?

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  10. #10
    stewartb's Avatar
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    The temp range and area of the heat gun makes it difficult to use for large areas, and the likelihood of the finish looking like crap afterwards is high. When the fabric shrinks the coatings don’t, and if it’s Stits? The under coating gets soft. Test it on a small area first. And FWIW? The parchment paper and iron idea sounds good but it’ll blister the coatings, too. My guess is you’ll be re-covering.
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  11. #11

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    .. or didn’t bring the fabric up to 350° per STC.
    What was the ambient temp when you took the photo?
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  12. #12

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    Wrinkles in my fabric

    I used a fabric iron and damp t shirt material to ‘fix’ some paint bubbles on my RV8, worked great and didnt scorch the paint.
    Might be worth a try… go easy on a small area…


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  13. #13

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    Don’t use a heat gun that’s probably what caused the issue in the first place. Not really sure there’s much you could do to fix it.
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  14. #14

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    I can't say for sure when I took the picture. Somewhere around 40-50 degrees.

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    Appreciate all the responses. I don't mind recovering it if that's what it needs. Are there any safety issues with it as-is? The plane seems to fly good.
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  16. #16

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    Could totally be fixed with a heat gun and someone who knows how to do it. I’ve retightened a lot of finished fabric after either not being shrunk properly or glue coming loose. I totally agree about not doing the initial shrink at install with a heat gun, but that’s the only way to fix finished fabric and keep it looking good. That being said, I’d have no problem just flying it as-is other than you’ll probably get cracks in your finish sooner with it moving a bit more than normal. I know of a few planes that look like that every time you roll them in a warm hangar on a cold day...

  17. #17

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    Check and see what process was used to cover the wings. Also check what finish, ie urethane, polytone, etc.
    I think an iron will make a mess no matter we what the finish.
    Heat gun damage is usually from over shrinking the fabric. It appears the fabric is under shrunk. If it tightens up in a warm environment I think it’s pretty safe to assume it’s under shrunk. I had a similar situation with a patch of fabric behind the tank bay, only appeared on cold days . I attributed it to the underlying aluminum pulling heat out of my crappy iron and not maintaining correct temp for a good shrink. Solution was to carefully tease the area with a heat gun. (and get a better iron), solved the problem.
    Yours looks to be a little more extensive.
    Very thoughtful, consistent and careful application of heat with heat gun may be your only solution. The danger of overtheating the fabric it will weaken fibers, probably ruin your paint job as well.
    That said, I’ve intentionally tried to overheat fabric with a heat gun, takes a lot of heat focused on one area for awhile, paint starts discoloring is a clue your overdoing it. Or over done it.
    Last edited by Oliver; 10-21-2021 at 09:19 PM.
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  18. #18

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    Yep- you’ll wrinkle the finish before you hurt the fabric- once it’s painted.
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    Thanks again for the posts. Very helpful. I'll try to find someone who has done this and get some help.

  20. #20
    Gordon Misch's Avatar
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    Maybe a thermostatic heat gun, like prescribed by Oratex? Just thinking out loud - - -
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  21. #21

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    Might have to try that. .

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  23. #23
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    As said before...NO heatgun!! You can't control the temperature. When fabric is over temped, it loses it's tension and never returns. I doubt that's what the initial cause is though. I've seen this situation a few times, and it is usually caused by improper shrinking to start with. Sometimes it's from some "expert" using a heat gun, and once in a great while it can be traced back to a really low quality iron, but very seldom. Even shrunk to 300 degrees, the fabric won't come to bag if it's evenly shrunk to that temp, and I'd lay money that even 250 wouldn't show up like this. What I've seen and been able to trace back to is what follows.
    A lot of people think you're wasting your time when you "sneak up" on your final 350 degree shrink temperature, but you're not. When polyester fabric is manufactured for aircraft, it's heated and stretched, then cooled, thus when a certain amount of heat is applied, you get a certain amount of shrinkage. As each fiber reverts back to it's original length, it also increases in diameter. Going up in temperature a little at a time, moving the iron slowly, as well as the cross pattern that you're supposed to use on the ironing, you give the individual fibers a chance to orient themselves, with their new diameter. If you jump right to the 350 degree setting, they tend to "bind up" in some areas, and as the fabric gets colder, it can't react, and causes wrinkles. I also have seen some people that insist on leaving a bunch of slack in the fabric when they apply it. That's wrong too. Your fabric will shrink approximately 10% in fiber length. Too much slack, and there's no way it can reach the final tension that it needs.
    As was said before, the dope guys usually didn't have much problem with this, as even the so called "non-tautening" butyrate, continued to slowly get tighter for ever. This wrinkling showed up primarily when the stable topcoats were introduced, and the fabric wasn't prepared correctly to start with. I have seen some Superflite fabric over a heavy leading edge, that I had trouble getting shrunk properly, from the heat sink of the aluminum. Moving the iron too fast is a common mistake that can also result in problems when the fibers don't get thorough warming. When in doubt, slow down and go over it again!! With an iron that's set properly, you'll never damage the fabric, even if you let it sit on there all day!
    As far as a fix, you're limited. Of course, recover would fix it, but before I did that, I'd go grab some Teflon heat transfer sheets (get them at a craft store), and start out about 275 degrees with a GOOD iron (such as the new iron that Consolidated Coatings puts out, or a good Ski Wax iron, that will hold the temperature well) and slowly go over the entire wing, keeping the iron on the Teflon sheet (I like to use 2 sheets, and leapfrog them, so I can keep the iron moving slowly along), allowing plenty of time to soak the fibers in heat, in a cross pattern, first chordwise, then spanwise. If it all looked good when I was done, I'd go to 300, and use the same procedure. You might be able to get 350 without any damage to the finish, depending on what it is, so I'd definitely start on a spot maybe under a wing root fairing, so if it discolors the finish, you wont notice it so much. This might gain you some time, before you have to cover the airplane. I'd say it's worth a few hours of trying.
    John

  24. #24

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    Pretty easy to fix in a day compared to a 15 grand recover.
    DENNY
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  25. #25
    Steve Pierce's Avatar
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    Before you do anything find out if it does it again and under what conditions. I had a Super Cub that I had recovered do this after we brought it to Texas from Florida and then it went to the midwest in cold humid air. I know for a fact that the fabric was shrunk to 350 degrees. I called Polyfiber and they see this occasionally. It tightens right back up and only occurs when the conditions are just right. No after effects that I am aware of.
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  26. #26
    Grant's Avatar
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    Happened to me.... Cold and humid in the hangar and we opened the door and it was warm out. I watched it happen. two hours later and it was gone. I only saw it once and never saw it again. it was not this bad and was on the fuselage.

  27. #27

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    I went out today and the wings look perfect. No drooping between ribs or anything. Also feels nice and tight. Based on how they feel and look at this moment I would never try to shrink it. The wrinkling seems to only be there when I get done flying. The picture above was just after landing before putting it in the hangar. It is getting colder now but I have seen this all summer. As mentioned the airplane has been in the same area for a lot of years.

  28. #28
    stewartb's Avatar
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    Buy a cheap optical thermometer and see if/what the temperature relationship is.

  29. #29

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    Still a little concerning, especially if it’s doing it consistently in warmer weather too.
    If you decide to address it, think John’s advise is the way to go (as usual )
    but iron only panels between tapes, stay away from tapes, they’ll shrink first and more and make a mess of things.
    Best of luck,
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  30. #30
    BC12D-4-85's Avatar
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    In flight the fabric stretches...mostly up on the top and bottom between the ribs. If it doesn't lay flat after a flight I'd suspect residual stretching that takes time to recover to normal. Whys if it does is the question.

    Gary
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    Hardtailjohn's Avatar
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    Quote Originally Posted by Oliver View Post
    but iron only panels between tapes, stay away from tapes, they’ll shrink first and more and make a mess of things.
    Best of luck,
    Absolutely correct! I forgot to mention that!!! Good catch, Oliver!!!
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  32. #32

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    Let us know how it turns out!

  33. #33

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    Call Dan at Dan’s aircraft in Anchorage, he fixed one for me using a heat gun outside in 10 degree weather!


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  34. #34
    BC12D-4-85's Avatar
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    If it were mine I'd simply push on the fabric between the ribs. See if it resists or stretches and stays loose. Note how long it takes to recover the original form. Not a big test but might offer info.

    Gary

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    I’ve seen that but in reverse, and not near as bad. aircraft sits outside in high humidity, fabric sags a little, then tightens up when it warms up and dries out (dope process).

    I’m leaning like some posters above that the fabric may have been over heated and lost its strength. You say it sags after flight. Meaning the fabric is weak, gets stretched in flight, then slowly tightens itsself back when it sits again. Like a warn out rubber band.

    Try the tricks listed in the previous posts first, won’t hurt to try. However IMO looks like a recover job to fix it properly.
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  36. #36

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    I had this problem after having the plane recovered with the Blue River process in 1985. Discovered this initially when refueling. Cool moist air resulted in the picture similar to yours. Haul it out in the sun and it returned to "normal". Put up with this issue for over 25 years (drove me nuts) and finally decided to have it recovered using a different (Stewart Systems) process in 2012. Never had the problem again.
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