Fabric tension warning ????

[pmanton]

Don't take the fabric above 300 degrees. These Champ wings are flimsy as can be , they are not Citabra construction. All the systems that use Dacron shrink in 3 levels 250,300, 350. The Champ wing will not take 350. It is to be treated like the Ultralites

I found this warning on another board. There were no comments about it.

I have never heard of this. Can this be true? The wings have withstood tightening dope in past years, especially with the newer heavy ribs I can't imagine that 350 degrees would be a problem.

Comments please.

Thanks

Paul
Salome, AZ

[MikeB]

My L16 (Champ) wings were rebuilt with new .032 ribs, spars and new leading edge (.022 ??) I'm pretty sure I took it up close to 350 degrees. The only problem that I had was the butt rib got bent in a little which appears to be a normal problem due to lack of support in that area but the wing farings cover it anyway. If I had to do it over again I'd try to stiffen the butt rib up a bit. Might be a different story with .020 ribs and .016 (original) leading edge. The other problem area seems to be the tip rib on the aileron bay. I've seen all kind of fixes on there to try to keep them from bending in. Originally I think they came with a wood support screwed to the rib. I wound up using wood plus a piece of aluminum angle iron...that helped a lot.

Mike

[Paul Agaliotis]

Paul,
I don't believe the statement is accurate. The fabric needs to be installed to allow the heat shrinkage. Generally the fabric is too tight before shrinking, this comes from habits when installing cotton. It shrinks only about 10% and is bidirectional, Dacron shrinks about 30% and is omnidirectional. If installed correctly the shrinking of the fabric is the same. The Citabria might tolerate over-shrunk Dacron better than the Champs, but it's never been an issue.
Paul

[Champ Dreamer]

I don't believe this is correct. Polyfiber reminds us that the untreated fabric should be installed loosly. I saw a homebuilt wing where a guy stretched the fabric nice and tight, then glued it. When he shrank it, it bent the trailing edge beyond use. After he ripped the fabric off and fixed the trailing edge, I helped him lay up the fabric and shrink it. 2 final passes at 350 and no problem. I had no problems with 350 on my Champ. Personally, I would follow the manufacturer's specifications before relying on an internet post.

Brian Walker
'46 7AC/DC flying daily !!!!

[pmanton]

That agrees with what I thought. PolyFiber specifically mentions that their STC requires 350 degrees for certified aircraft.

Paul
Salome, AZ

[MikeB]

If I remember correctly Poly-Fiber says to leave a 'pull up' of about an inch loose or at least certainly not tight. The Superflite manual says a 'snug fit' but not tight (whatever that means). I suspect if you have a real weak member: the outboard of the rudder fin is a good example and you installed it too tight it would probably deform the light tubing. The rest of the aircraft is pretty substantial other than the aileron bay tip ribs. There is a brace available for that but it still takes some additional bracing to prevent the tip from bowing in as the fabric is tightened. Also if you look at a lot of Champs and Chiefs, the butt end of the horizontal stabilzer usually has a outward bend. I guess it probably makes them look 'original' .

Mike

[dikholder]

I am using Stewart Systems on my Sedan. The Stewart manual refrers to using lower temps on the lighter fabrics 101 ect which they say are often used on experimentals, aerobatic aircraft and antiques. I went 350 on my Sedan with 102 fabric, my iron is cheap, so anything hotter than that scares me.

Dik Holder
N1441H The Queen of the Berry Patch

[brink]

This post is about 5 years old, I am in the process of recovering my Champ-control surfaces,and fuselage. Polyfibre, when you shrink it, I let if set for a few days and let the weave relax, then shrink it again, let it set, I say the longer the better, I’ve done that for up to a week. Then do a reshrink, let it set, if you see a shiney spot, you got it too hot! Try not to do that, and it can be prevented by just keeping the Iron moving,do not use a heat gun if you melt the fibers, it will eventually ring worm. I thin my poly brush and moderately press on the brush to get a good weave penetration on my first coat, using the poly brush will also shrink the fabric just a little bit, let it set for 24 hours then finish it out, I also use the light weight tapes, they lay down really well and fill nicely. Then I spray 2or3 coats of polybrush. Cannot sand polybrush, I’ve tried just balls up, polyspray sands really well. If you follow the manual it’s pretty hard to over tension the fabric, the key is to keep you Iron Moving. Great posting, really enjoy the reading

[brink]

Been sleeping on this fabric issue being reported that when finished the fabric bows up in flight on the top of the wing. Not to offend or criticize,but something was done wrong, I’ve never seen that and flown with guys in formation and never noticed an issue a lot of guys are using poly fibre products here in the DFW area, and several of the guys are very talented, but I have noticed in the past 10 years fewer fabric aircraft compaired to the RV family are about 5 to 1 and growing, maybe higher, but their are a bunch of them flying around, I hope every body have a Merry Christmas, and keep on posting great reading!