Fuel Proofing

Clear lacquer will not work for fuel proofing. In addition to that, polyurethane is much heavier for a model that your presenting. If you already doped on the silkspan or tissue and you poly over it, it can cause other issues as well on open bays. Dope is special due to it's flexibility whereas poly isn't the same. Once exposed to the sun, the clock starts and poly over tissue can make your covering like a potato chip.In addition, no repairs can be made via dope because dope and poly are incompatible. One is high solvent and the other is oil based. Poly can go over dope, not the other way around. Polyurethane will work it's just that you need to go super easy with it and not hose it on. It will protect against higher nitro but not for very long. The finish will start to crinkle where it has penetrated.

Sig Lite Coat yields the highest fuel proofing qualities over any dope available. However, dope isn't and never was fuel proof. Generally , most butyrate thinners are compatible with each other. I alternate Randolph butyrate thinner with Sig regulary and I 've done the same with Brodak. The issue is how your applying it and the temperature. Sig thinner was very special as it was the slowest drying thinner available commercially for our use. It enables it to be brushed superior to the others because it has more open time. Brodak is a medium rate thinner and it generally requires a splash of retarder. This is because as a faster drying thinner over Sig, it traps moisture on the surface . I've done some very nice brush finishes with Brodak . It takes a bit of a learning curve to do so though. Sig offered the best finish even for the beginner.

In general, most dopes are good to 10% nitro. So the bottom line is don't spill it or get it onto your dope. This can be prevented a few ways. Build up many many coats around the engine area and wax it prior to seeing fuel. Wipe it off immediately if spilled. High nitro is like pouring thinner on your model and on a 1/2A , high nitro fuels will destroy it.

I have no experience with EZE dopes. I believe it's not a dope but some sort of water based product which claims to be aliphatic. Most of these products are thinned down PVA glues which utilize a alcohol base as a carrier to speed drying and improve flowability. I have never used it but I've been aware of it for years and I hear good results with it. I've just never seen a finish done with it.


I've done many models like your building currently. Because of weight concerns, I use colored tissue for trim followed by Sig Lite Coat. I also use another product with these models called Dave Brown Flex-All which is a plasticizer for butyrate dopes. This keeps the covering as pliable as Monokote and makes it rubbery and puncture resistant. It also prevents the dope from shrinking and crushing the model like the stringers.

I'm assuming that what I see in the pic is a Pee Wee .020? You can run it on 10% which is how I generally use mine for free flight on the dropper. Yes, it is down on power but it offers me a little more time on the ground to set it and it doesn't go out of sight in 10 seconds. I'm limited to space so one thing I do is turn the prop around and lean it up a fair amount on the 10% which offers a nice slow speed but it does the job.

Your model looks terrific , I'm looking forward to seeing it complete and I wish you success. Nicely done. Ken