|
Original question:
>Are there any problems with using expanding foam sealant
(moisture cure polyurethane foam, such as Great Stuff) against unprotected
aluminum? I've got the belly pan off, and will be replacing all but the outside
8"-12" of the pan with new sheets of aluminum, painted white both
sides. Before I attach the new white to the old (still attached) original
perimeter of the pan, I'd like to shoot this foam into the crack between the ply
floor/steel frame and the aluminum skin. Any problems?
Reply:
Answering my own question, with about 90%
confidence:
I got through to a technical support person at Flexible
Products (mfr.. of Great Stuff Foam), who advised that there would be "no
problem" using this product with raw aluminum. I expressed my concern re:
off-gassing of undesirables like ammonia, and he said that this product is
already "99% cured" as it comes out of the dispensing tube, and
although there are trace amounts of ammonia and MANY other gases given off in
final curing, they are insignificant. He had personal experience using this foam
for components made for buses in which aluminum parts were combined with
expanding polyurethane moisture cure foam with no problems ... ever. In his
experience. He did make it very clear that once stuck to the aluminum, there is
no way of removing the cured foam, other than cutting and sanding.
I think getting this stuff on the outer edges of the ply floor
will be a great deterrent to future water rotting problems. It's the edges of
plywood which really "wick up" the moisture, more so than the
face.
So barring any last minute dire warnings from fellow VAC
members, I'm planning to seal up some cracks between subfloor and skin later
this week with expanding polyurethane foam. From above and below. I do think
I'll use the minimal expanding variety for fear of causing any bulges in skin
along floor line. All advice appreciated.
Bob Harper
'62 Globetrotter in SC |