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Old Apr 15, 2014, 09:55 PM
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WW1 Flying Ace's Avatar
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Koverall and dope problems

Hope you folks can help with where I went wrong on a Balsa USA 1/4 scale WWI plane - using Koverall and dope. I prepped the framework with about 3 coats of unthinned nitrate on the edges where I expected to fasten the fabric. The fabric went on the wings, fuse and tail fine. I then brushed 2-3 coats of 50-50 thinned (was probably closer to 70-30 as I got toward the bottom of the can) on all the fabric, with a light sanding between coats. All looked good until I sprayed on my color paint. I was using Krylon out of a can, and had intended to shoot a coat of clear polyurethane over that.

Ugh! Pinholes everywhere. And - places where there was wood structure underneath looked awful - pitted and 'rough' - like the wood had soaked up the dope from below - leaving clear outlines. It looks awful, and I'm about to run the whole project through the saw.

Can you guys recommend what I did wrong? More clear dope coats? Prep the entire framework (not just the perimeter edges) with dope?

I'm using Randolph non-tautening dope and their thinner. Thanks for taking the time to help. - Bob
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Old Apr 16, 2014, 12:48 AM
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aeronca11AC's Avatar
Kirkland, WA
Joined Sep 2007
157 Posts
PInholes are from the solvents not being gassed off before the second coat. They escape and create the holes. Sanding is the usual treatment. Then waiting a longer time between coats. Orange peel is also another danger of two coats being sprayed too close together.

I don't know about Krylon being compatible with dope. Usually you keep the process all the way to the top coat. Changing from one process to another makes you experimental... and sometimes the experiment doesn't work! Pinholes and orange peel can be the result.

Final color coats with Randolph can be really nice if you put retarder in the mix rather than thinner. It allows the dope to flow out better.

That's my Chief in the photo and I did the whole thing in Randolph lemon yellow and newport blue metallic.
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Old Apr 16, 2014, 04:10 AM
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United States, MD, Elkton
Joined Oct 2011
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I had the same problem with the same products,except I used thinned Nitrate from the beginning (about 20% thinner initially), then 50 - 50 for the "primer" coats.

The Koverall has fewer threads per square inch than Stits 'lite', that I use exclusively now.

I was lucky enough to put paint on the rudder first, and saw the pinholes of which you speak. I brushed a coat of sanding sealer, mixed with retarder, then sanded that..I thi nk a couple more coats of 50 -50 would have done the same thing..

I do put several coats of dope on the wood surfaces to seal them, before applying the covering...
I think you just didn't put enough coats all over to close the tiny pin holes-not a criticism-just being helpful.

Stits lite is 60" wide, by any length you want, about $8 a running yard. It fills easier,and saves the difference in cost by using less paint.

This 1/3 scale model is Stits, Nitrate Dope, and Rustoleum rattle cans.
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Old Apr 16, 2014, 05:52 AM
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md6364's Avatar
United States, MN, Park Rapids
Joined Feb 2014
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You do want to put the nitrate over everything that will touch the covering. I have no experience with Koverall; but, have not heard any bad things about it. It does look like it would takes a few more coats to fill, than Coverite or other types of fabric covering.

I would experiment with a Krylon primer, put a coat or two on to see if it fills, then try the color again.

I don't see there being a problem with your process (Nitrate, with Krylon over, sealed with a clear) I think this is qute a popular method of finishing.
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Old Apr 16, 2014, 06:39 PM
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United States, KY, Taylorsville
Joined Mar 2010
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The process I use is to 'Stix-It' the airframe and apply fabric with same. Then, to fill the weave of the fabric, 50% thinned nitrate dope for about three or four coats applied with a fuzzy roller. Lightly sand between dry coats. Spray the color. Since you have put the color on you will have to use a compatible product as per md6364's suggestion. Don't give up! Next time you will know how to 'look' for the pinholes. I really like Koverall but would like to try the Stits (tighter weave) when I run out of my current fabric supply. It isn't issue enough for me to give up on Koverall since, as I said, I like it so well.
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Old Apr 16, 2014, 07:32 PM
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Joined Dec 2012
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Thanks. I think I'll have to seal all the wood as md6364 suggests - otherwise even 3 coats of dope seems to be absorbed by the raw wood underneath the fabric and an ugly outline shows through. I'm also thinking of a little talc in those last coats of dope. And maybe latex outdoor house paint....
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Old Apr 17, 2014, 09:17 AM
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San Diego, California
Joined Dec 2004
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Seems like when I was doing that sort of thing, I doped the wood until I had a glossy surface. Then I knew the grain had been filled.

Les
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