wrote:
Polyurethane glues are not meant for gap-filling applications.

I always figured that was one of the advantages of that type of glue. It
would expand to fill gaps.

I don't like it because it's quite messy but I've used it anyway just
because of the "gap filling."

Well, one would think so, but surely you've noticed that one the things
that makes it mess it is foams -- the gap is filled w/ the same way --
it's mostly air w/ only a tiny amount of glue making up the bubbles.
So, you really end up with the worst of both worlds -- the gap isn't
solidly filled so it doesn't finish well and (at least in that area) the
joint isn't very strong.

Obviously the best answer is to make well-fitting joints but for
gap-filling, choose something other than the polyurethanes (epoxies w/
fillers, etc.). The only time I really would recommend p-u's is for
locations that really require the fully waterproof nature or for an
application perhaps requiring the long open time during assembly I
_might_ consider it (although w/o the waterproof requirement it would be
pretty far down my list of alternatives probably).

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