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this stuff starts out like dry playdoh and you mix in a tiny bit of the liquid activator (100 to 2.5) and it becomes more pliable... but wow, it is really nasty smelling.

you may notice that i ran a light coating of proseal on the floor to stiffener connection.... having read about a somewhat common issue of high frequency vibration being transmitted through the floor i decided to try adding some damping by prosealing the stiffeners. i do not know if this will actually help anything, or if there will be anything in need of help, but it is clear from building the tanks that prosealing flanges provides some level of attenuation and harmonic dampening, so we shall see...

 

[rvbuilder2002]

My opinion is that any material that is thick enough to roll into a ball in a gloved hand should not be used between riveted skin surfaces. I would expect the high viscosity to restrict it from squeezing down to a very thin sealing layer.

 

[HEGASIS]

It is common practice to place proseal between all faying surfaces on jets. You do the same thing with the tanks.

 

[mcencula]

Thinning works

I just did the sealant around my firewall yesterday. I tried to apply a thin bead by masking off on both sides of the bead, applying the sealant, then peeling the masking tape off. Low and behold, the sealant came right off the flange of the firewall when I peeled the tape.

This thick stuff peeled right off with the tape:

Take 2:
I mixed up some more of the CS-1900, then thinned it out very agressively with lacquer thinner until it was roughly the consistency of Proseal. It worked great. I noticed today that this stuff seems to harden hard, though...not rubbery like Proseal.

Here's the mix in a pan after thinning with lacquer thinner:

A layer smeared over the tape:

Nice, uniform bead after peeling the tape:

Good luck, and happy building!