Fiberglass vs. Fabric

I BOILED some samples for 24 hours with no degradation other than a bit
of
color change. Add light fiberglass over that...

Did you compare bending strength before and after? What is the
glass transition temperature for WEST system epoxy?


Well, actually I made up a long sample with 2 1" wide strips glued (with
fillet) together at a 90 degree angle. Then
I cut this into samples, each about 1" long. Then I took these little "T"
shaped samples, and subjected them to all sorts of things.

They were made of Finnish Birch 3 ply (3mm thick, but quite dense.) It
looked like it had penetrated to me - and they sure stayed together fine. I
boiled several of them, and broke them afterward. The wood gave before the
glue in all cases.

I've also tried this with 1/8" Okume. Same result, but that stuff is porous
enough that I'm pretty sure it soaks all the way through. I've been meaning
to try it with that unfinished mahogany indoor plywood. If that "soaks all
the way through" stuff works, it would be usable as a core, so I could use
much cheaper material (for boats at least).

As for the glass transition temperature, I think most epoxies are in the
140F range. After they cool they will return to much the same condition they
were before though. The extra cure may even be beneficial. That's just a
dull memory though. Correct me if I need it, but the boiled samples really
did stand up fine (I'm looking at one now).