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Apr 22, 2019, 12:41 PM
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Discussion

dope compatibility


Afternoon everyone,

I'm in the middle of restoring a GeeBee Model E. It was designed by a friend for scale competition and was built in about 1978. It got four flights before one of the landing gears broke. He stripped it and put it under his workbench. I have it now and am in the process of re covering it. It was a good flying plane he says and I have a ton of documentation. While I don't plan any competition with it I'd like to get it back to original as closely as possible. I have the dope color codes for Randolph colors. The plane is now covered and has Sig clear dope. Sig says they do not make either of the two colors, green and a cream color, any longer. Since I have the Randolph color codes it should be easy to get them to mix up something very close. The question is, are Sig and Randolph dopes compatible? The Sig is butyrate, is that true for Randolph? The full scale E was also originally done in red and white which are available from Sig but I'd like to paint it as originally done if possible. Thanks.

Rick H.
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Apr 22, 2019, 07:57 PM
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I've used both Sig and Randolph dopes together with no problem. Randolph is cheaper too.

carl
May 07, 2019, 11:57 PM
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Yes, they’re compatible but you will want to apply a top coat of SIG clear if it’s glow fuel powered. Randolph stands up to gasoline but glow fuel makes it get sticky and then it gets dirty.

Learned that the hard way.
May 08, 2019, 10:36 PM
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I’ll keep that in mind, accurate Randolph colors are on the way. Not fuel proof? Hhhmmm...

Rick H.
May 21, 2019, 08:20 PM
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Quote:
Originally Posted by 308jockey
I’ll keep that in mind, accurate Randolph colors are on the way. Not fuel proof? Hhhmmm...

Rick H.
Randolph is formulated to be used on gasoline powered aircraft; they aren't concerned with resistance to hot alcohol and nitromethane. I painted a Super Sportster that was covered with Solartex with Randolph clear. After a few flights the cope started getting sticky and dirty. It was years ago so I don't recall if the fuel was 10% or 15% but most likely 10%. I cleaned it with nail polish remover and then sprayed SIG clear over the Randolph. Problem solved. I also painted a clipped wing Cub with Randolph and had to clear coat it with SIG clear for the same reason.

As an aside, I just thought of Stits Poly-Tone. They say it's fuel proof but it isn't dope. It's a polyester vinyl.

http://www.stits.com/store/faq.html

Is Poly-Tone fuel proof?
"Yes, the methanol in our fuel isn't a strong enough solvent to affect a polyester vinyl. Neither is nitromethane in reasonable amounts either. What may be a problem is if you spill gasoline with ethanol mixed with it. Gasoline isn't a problem, ethanol is. We have tested Poly-Tone with 20%nitro with no ill effects, over 20% and you're on you're own. "
Last edited by David2011; May 21, 2019 at 08:31 PM.
May 21, 2019, 08:43 PM
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Sent an e-mail to Stits to get their opinion of the fuel resistance properties of Randolph butyrates.
May 26, 2019, 08:01 PM
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All dope finishes, whether they are SIG, Randolph, or brand X should have several clear coats over the color coats to completely fuel proof them. I have Randolph doped airplanes that run on glow fuel and the dope is non the worse for wear after many years and tons of flights.

carl


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