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Charlie,
Do you know if that Flamemaster stuff is okay for composite tanks? Is Van recommending that instead of Jeffco (which I've always heard was nasty stuff to apply)?
I've heard that the pure structural epoxy coating used by the composite builders is pretty safe when you do a good job of it. However, I'm a little nervous about mogas because of its corrosive reputation and have been listening for recommendations of good sealants. In Chicago, I think all the local mogas has alcohol for emissions reasons--at least all the pumps list it.
Because Nat Puffer monitors the Cozy list and hates mogas (and auto conversions), asking about sealants is not a great question over there unless you want the lecture and cold shoulder that go with it.
Also, the latter part of your note mentioned you could recommend some other pourable sealants. What would those be?
Barry Gardner
Cozy/Aerocanard
Wheaton, IL
Charlie England wrote:
1st step would be to check the datasheet on whatever sealant you used in the tanks. The Flamemaster brand stuff Van's sells now is supposed to be immune to avgas and mogas. It seems unlikely that a few minutes of exposure would cause such a major leak, even with the old mogas-vulnerable sealant. Did you use access covers on the aux tank like the mains? If so, did you use the cork gaskets? A LOT of people have leaks around the cork gaskets after months or years of flying.
I'm just about finished with my RV-7 tanks (remember my aux tank questions about a year ago?) & I had to seal a few leaks. I called Flamemaster to ask about a compatible, pourable sealant & they recommended cs 3600, a 1 part pourable compound. I swapped a few emails with their help person because some of the datasheets indicate use as a pourable 'slosh' type sealant, other (later) datasheets omit that use in the product description. In emails, they maintained its suitability for use on top of the 2 part paste that Van's sells. This stuff is not the same as the milky white stuff that caused so much grief in the past. It's a translucent red color & acts about like pourable contact cement. In fact, the datasheet describes it's primary use similar to contact cement application.
I was able to 'inject' it to the problem areas by sucking it into some nylon tubing & routing the tube toward the problem seam before releasing the fluid & then pushing it out of the tube with very low pressure air. I was trying to minimize the unneeded sheeting over large areas of the tank where no holes existed. The tanks now hold air, but it will obviously be a while before I can vouch for long term reliability.
Several folks on the RV-list mentioned that most peeling problems with 'slosh' were probably caused by the tank's interior not being completely clean before sloshing. That makes sense to me, since I very carefully cleaned the areas where I knew I'd be putting sealant but didn't work too hard on the rest of the skin inside the tanks.
I also got a couple of other recommendations on pourable sealants I can send you if you want.
Charlie
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