Quote:
Originally Posted by Walt
I've never used the Flamemaster, I've always used PRC Desoto "ProSeal" and have used the AC Tech for repairs with no issues (it is also dark gray). For building tanks I personally would only use PRC (this is what I've used/seen used my whole career) with good results (very rare to get a bad batch). We would seal a tank and put fuel on it 8 hours later with no problem. Using B-1/2 we would put fuel on it after just a few hours if we were in a rush.
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The jury is out on tank sealant IMHO.
My QB tanks built in 2002 were done with Proseal, no question of it. But they leaked a gas around rivet shanks causing paint blisters forever. I finally built new tanks last summer using Flamemaster from Vans. So far they are OK. No blisters as of this date that I know of.
I kept some of the paper plates used to mix the stuff for a while to see how it would set up and cure. In every case it cured quite firm in a few days.
A couple weeks ago I decided to use some of the remaining Flamemaster (out of date) in the rudder and elevator skin bend area as called for in the build plan. I did not weigh the mixture this time but just mixed it until the color looked about right, it too cured very firmly in a couple days.
Technically, I believe Proseal and Flamemaster meet the same military specs. The only difference is the price and that's why Vans uses Flamemaster.
I don't have a clue what is going on with the tanks precipitating this thread. There was a report a while back where the sealant on the exterior of the tank became soft when fuel leaked through to it suggesting there was something going on when oxygen is present with fuel and the sealant. I never heard an explanation as what did cause the sealant to go soft beyond that speculation.
The brown stuff in the tank is suspicious. My first thought was residual matter from fuel that had evaporated. But it could be sealant breaking down. If so, there is something really wrong with that batch. These sealants are designed to withstand fuel.