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Loose Fabric

cub yellow

FRIEND
North Central Wa.
I have an experimental supercub that was covered with poly fiber about 10 years ago and has aerothane applied as a finish. Aft of both fuel tanks it looks like the fabric was not properly attached to the sheet metal.

Under the tank covers it looks like the fabric is firmly attached at the front of the problem area.

I've owned the airplane for 3 years and it was like this when I bought it. It isn't getting worse but I'm wondering what, if anything I can do to tighten up the fabric in this area. Ideas appreciated.

Brad





Sent from my VS988 using SuperCub.Org mobile app
 
I have an experimental supercub that was covered with poly fiber about 10 years ago and has aerothane applied as a finish. Aft of both fuel tanks it looks like the fabric was not properly attached to the sheet metal.

Under the tank covers it looks like the fabric is firmly attached at the front of the problem area.

I've owned the airplane for 3 years and it was like this when I bought it. It isn't getting worse but I'm wondering what, if anything I can do to tighten up the fabric in this area. Ideas appreciated.

Brad





Sent from my VS988 using SuperCub.Org mobile app
Photo of problem area.

Brad1217201254_Burst01.jpeg

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Not much now. If you heat gun it the tapes will shrink and leave bad areas

Those areas are hard to shrink, because the metal under there expands as you heat the fabric. Then when it cools it’s loose again. Same for leading edge area. Alonso why I do leading edge area FIRST for final shrinking


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I've got a somewhat similar issue on my S-7S, Poly fiber/Polytone. Not over metal though, and at this point it doesn't really matter why (probably misuse of the iron by the original builder, he may have missed the area on the last iron hi temp pass, that'd be me.....) and is only visible in cold weather. AND, not all the time, even when it's cold but parked in the sun, it goes away in a few minutes. If I knew the issue was caused by initial lack of enough heat, that'd be one thing, and maybe I'd try the heat gun approach (scary) but maybe the looseness is because of initial excess heat (doubtful, I know how to calibrate my iron, and never use a heat gun).

I've put up with it because no one else has ever noticed and commented on it, at nearly 2700 hours now its maybe better to just not mess with it and possibly make it worse. But being that it's a Poly-Tone finish, do I possibly have a way to hit the area with an iron, maybe with a thin layer of cloth between the iron and the paint? It's not like I'm worried about the glossy finish, ain't one. I could take a picture, but it's not as bad as the one pictured here, and like I said it only shows in cold weather, and sometimes not even then. I must be right on the thin line of having the proper tension in that area
 
I don't believe there's any tapes in the area, can't recall right now but if so I'll avoid them. Parchment paper, that sounds about right...what is it exactly and where can I get some?! I do have some sheets of heavy grade stationary, bought for something I needed to look important, that may qualify as parchment paper I guess.

Never mind, googled it, my local Bed Bath and Beyond store has some in stock, $4.99! I will give it a shot, thanks! [h=2]Parchment paper[edit][/h]Modern parchment paper is made by running sheets of paper pulp through a bath of sulfuric acid[SUP][1][/SUP] (a method similar to the way tracing paper is made) or sometimes zinc chloride. This process partially dissolves or gelatinizes the paper. This treatment forms a sulfurized cross-linked material, with high density, stability, and heat resistance, as well as low surface energy — thereby imparting good non-stick or release properties.[SUP][2][/SUP] The treated paper has an appearance similar to that of parchment and, because of its strength, is sometimes used in legal documents for which parchment was traditionally used.[SUP][3][/SUP] (However, parchment paper is manufactured with acid, and has a low pH, making it inappropriate for archival documents where acid-free paper is the better choice.)
 
If that all fails, and it bothers you....cut it out and glue a nice patch in there...if you have a decent place to work on it
 
I don't believe there's any tapes in the area, can't recall right now but if so I'll avoid them. Parchment paper, that sounds about right...what is it exactly and where can I get some?! I do have some sheets of heavy grade stationary, bought for something I needed to look important, that may qualify as parchment paper I guess.

Never mind, googled it, my local Bed Bath and Beyond store has some in stock, $4.99! I will give it a shot, thanks! [h=2]Parchment paper[edit][/h]Modern parchment paper is made by running sheets of paper pulp through a bath of sulfuric acid[SUP][1][/SUP] (a method similar to the way tracing paper is made) or sometimes zinc chloride. This process partially dissolves or gelatinizes the paper. This treatment forms a sulfurized cross-linked material, with high density, stability, and heat resistance, as well as low surface energy — thereby imparting good non-stick or release properties.[SUP][2][/SUP] The treated paper has an appearance similar to that of parchment and, because of its strength, is sometimes used in legal documents for which parchment was traditionally used.[SUP][3][/SUP] (However, parchment paper is manufactured with acid, and has a low pH, making it inappropriate for archival documents where acid-free paper is the better choice.)

Any store has it in the baking isle.

And thanks to whoever it was on here that told us about using it with stitts!!! Was a game changer.

But one warning, after heating, let it cool FULLY before Trying to remove the paper or you will pull the paint and subsurface layers with the paper.


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Did not know that "let it cool" trick. Also, when shrinking yellow, at least, don't freak out when it turns orange. Goes back to yellow when cool.

if you don't have an accurate iron, try it on a test panel first.
 
I’ve heat gunned that area on multiple Cubs- no tape shrinking if you’re careful. It doesn’t take much shrink to remove the wrinkle- but before you do, make doubly sure that the wrinkle isn’t a result of a failed glued edge. The butt rib area under the fairing fan come loose and cause this issue too- check that and the tank bay TE closely; if an edge is loose, your wrinkle will just reappear.
 
Beware the parchment paper idea. By the time you get adequate heat to the fabric the polybrush and polyspray layers have softened but the Aerothane hasn't. The result looks like krinkle paint. You'd be better off leaving it alone.

That there's a pirep!
 
With Aerothane there's no sticking that I've detected. I have teflon fabric for a vinyl welder. I never thought about using it. The paint crinkle would happen either way.
 
Don’t overthink it, No iron, Just tease it with a heat gun, go easy at first, you’ll see effects right away, take your time.
that’s a funny area to work with when covering, if the aluminum is a little dished the fabric will pull away and not stick to the panel, my guess is it wasn’t shrunk enough.
 
A calibratable heat gun, like is specified for Oratex might be just the ticket. Just dial in the desired temp.
 
I would first remove the gas tank cover and maybe the gas tank, to see if the fabric glue has pulled.
 
I agree with Olibuilt, remove the cover and see if the glue joint at the tank opening has let go. I have seen that before. Have also seen the fabric get loose when there is a big temperature and humidity change. Discussed with Poly-fiber/Consolidated and they get cases of it. I have carefully and slowly taken wrinkles out like that with a heat gun holding it way back and sneaking up on it slowly and backing out quickly holding my hand on the surd=face to check how hot it is getting and watching from an angle where I can see the fabric get taught.
 
I had one wing that the fabric would sag pretty bad in damp or cool weather, I spoke with Dan at Dan’s Aircraft and he told me to bring it over when the outside temperature reached around 15 F.
He came out with a heat gun and slowly shrank the fabric on the entire wing, I watched as the heat hit the leading edge fabric, looked like there was a dent in the leading edge and he slowly worked the entire leading edge with the heat gun and I never had any problem with loose fabric after that. Fabric was stits, I believe with aerothane.


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