On Sun, 09 Nov 2014 13:46:11 +0700, John B. Slocomb
wrote:



The WEST Systems people have done tests of epoxy and common chopped
mate, see:
http://www.westsystem.com/ss/chopped-strand-mat-epoxy/
and while they don't suggest it as a first choice they do say that it
is usable.

OK, I had a few minutes and read that link. That's the one I thought
it was; WEST published it over a decade ago.

The stitched mat he mentions is the stuff made for use with epoxy.
That's not the mat we buy that's made for use with polyester. The
stitched mat has no binder.

The author wrote sbout his experiments and said regular mat "should
work fine" on gently curving projects.

Maybe. If the curve is too much, you can have one hell of a mess. The
fibers start to pull away as you work it; some stick to whatever
you're bonding to, and the rest tend to tear loose as you keep working
it, trying to get around the bend or curve.

Unlike polyester, you don't get that sharp initial gel stage with
epoxy. In tends to just keep getting thicker. With polyester, if the
project isn't too large, you can mix it a little hot and just keep
poking it with the end of a brush, or rolling it, until it takes the
shape you want. It will still adhere in the early stages of gelling
(so will epoxy). That will take only ten to fifteen minutes, at most,
with a moderately hot polyester mix -- one that isn't too hot to
produce good finished properties.

Getting cloth around a corner, with no mat, can also be difficult with
epoxy. In general, it's much harder to work with, if there is any
complexity to the shapes you're trying to cover, than polyester. If
the surfaces are flat, or nearly so, it's no problem.

--
Ed Huntress