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Author Topic: Fuel proofing silk  (Read 771 times)

Offline Shorts,David

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Fuel proofing silk
« on: June 19, 2022, 07:18:34 PM »
Hi everyone. I'm revisiting my Black Tiger I hung up two years ago. Problem one is this. I covered it in red silk. The silk has a ton of coats of clear butyrate on it, but still a mostly matte finish, which I don't like or dislike. BUT, as we know, dope is not fuel proof, especially over a coarse fabric like silk.

I've thought of stripping it and going with ultra Cote, or ..what is a good fuel proof top Cote I can spray on it? I have Helmsman Spar Urethane. Is that a good option? I have two part auto clear, but I wanted to see if there were lighter weight options first, like the urethane.

Online Dan McEntee

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Re: Fuel proofing silk
« Reply #1 on: June 19, 2022, 10:26:04 PM »
   Your biggest worry about being fuel proof is the nose area back to the wing roots. Finish up the model in dope like you have been doing. When finished with all dope applications, spray the nose area with an even coat of the two part clear. Even if you wanted to spray the two part stuff over the whole model, it doesn't need to be applied that heavy, just enough to cover, sand out a little bit then rub out. If you have come this far with silk and dope, it would be a shame to strip it all off now. Don't worry about there being an edge or some kind of demarcation line with the two part clear, just spray and even, light coat and it will all blend in, especially if you sand it very lightly and carefully before any rubbing out.
   Type at you later,
    Dan McEntee
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AMA 480405 (American Motorcyclist Association)

Offline Shorts,David

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Re: Fuel proofing silk
« Reply #2 on: June 20, 2022, 01:11:40 PM »
Thanks for the input Dan. I was thinking if I sprayed 2 part clear just on the vital areas it would make it appear very glossy, but with a little sanding maybe I can match the rest of the model. If not, it's on the bottom wing and bottom of the fuselage.

Offline EddyR

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Re: Fuel proofing silk
« Reply #3 on: June 22, 2022, 09:37:08 AM »
  David.      What do you mean “dope is not fuel proof over silk”  Clear silk was the standard building method for years.  Sounds like you do not have enough clear on the wing to seal it . If it looks dull it blushed or it is not finished. I had a clear silk dope model at the 1988 Nats and was in the second row with 18 points. I put over 1000 flights on that model and the clear silk was still good on it. Some people have sprayed thinner on blushed dope to clear it.
Ed
Locust NC 40 miles from the Huntersville field

Offline Shorts,David

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Re: Fuel proofing silk
« Reply #4 on: June 22, 2022, 10:52:25 PM »
  David.      What do you mean “dope is not fuel proof over silk”  Clear silk was the standard building method for years.  Sounds like you do not have enough clear on the wing to seal it . If it looks dull it blushed or it is not finished. I had a clear silk dope model at the 1988 Nats and was in the second row with 18 points. I put over 1000 flights on that model and the clear silk was still good on it. Some people have sprayed thinner on blushed dope to clear it.
Ed

I believe I had about 10 coats of sprayed butyrate on it. Perhaps I spray very light coats. But, on the bottom of the wing and bottom of the fuse, it looks like the silk is soaking up fuel after a flight. I assume if I peeled the silk off, the wood would be greasy. But, not 100% sure of that.

Offline EddyR

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Re: Fuel proofing silk
« Reply #5 on: June 23, 2022, 04:52:32 PM »
 Dsvid are you talking about exhaust or raw fuel. Exhaust will not go through sealed silk. The silk should feel smooth like plactic film. I use to use heavy brushed on coats. Also the brand of thinner will have a effect on shine. Be sure you sre not using asetone marked as thinner. Even half and half will cause problems.
Ed
Locust NC 40 miles from the Huntersville field

Offline john e. holliday

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Re: Fuel proofing silk
« Reply #6 on: June 24, 2022, 07:50:18 AM »
No one mentioned that dope never stops curing.  Also you could have some pin holes too hard to see.   I have several planes that you would think never been doped but show no oil leakage. D>K

John E. "DOC" Holliday
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Offline Shorts,David

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Re: Fuel proofing silk
« Reply #7 on: June 24, 2022, 02:29:01 PM »
So it sounds like you're saying, if I already put on ten coats of dope, the fuel probably isn't really getting to the wood.
I hope to fly it this afternoon or tomorrow, I'll look really closely to see if the fuel is going through or not.

Thanks

Offline EddyR

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Re: Fuel proofing silk
« Reply #8 on: June 25, 2022, 06:48:35 AM »
 10 or 100 it does not matter if it is not sealed. The surface must br very smooth so you can’t feel the weave. It sounds to me you do not have it sealed. It should be smooth like sealed paper. In the 1950-60’s i watched combat guys sit in the sun and apply coat after coat getting it to s smooth glossy finish in 2 hours.
Ed
Locust NC 40 miles from the Huntersville field

Offline Shorts,David

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Re: Fuel proofing silk
« Reply #9 on: June 25, 2022, 08:29:55 AM »
10 or 100 it does not matter if it is not sealed. The surface must br very smooth so you can’t feel the weave. It sounds to me you do not have it sealed. It should be smooth like sealed paper. In the 1950-60’s i watched combat guys sit in the sun and apply coat after coat getting it to s smooth glossy finish in 2 hours.
Ed

There is definitely still weave. I'm just going to shoot the underbelly area where fuel goes with some auto clear.

Online Ken Culbertson

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Re: Fuel proofing silk
« Reply #10 on: June 25, 2022, 10:45:58 AM »
It has been 50+ years since I have done silk so I will ask if it tightens with heat?  I simply cannot remember.  If it does, then a trick I have used on the open bays using polyspan might work. It has a similar pin hole problem.  I first lightly shrink the polyspan after adhering it to the edges.  Then I brush on a full strength coat of non-tauting dope.  While it is still damp I use the heat gun to further shrink the polyspan. When it is dry I do it again.  After two coats it is sealed.  The rest depends on the plane.

Might not work at all with silk, just a thought - Ken
AMA 15382
If it is not broke, don't fix it.
USAF 1968-1974 TAC


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