On Mon, 11 Jun 2007 17:09:14 GMT, Lew Hodgett
wrote:

Andy Dingley wrote:

Fibreglass is generally used with polyester resins, not epoxy.

Not true.

There are a lot of epoxy/glass laminations out there, including my boat.

I'd suggest that you're unusual in this, being significantly more
experienced than most. Maybe boatbuilders are fussier.

Certainly here in the UK, for "hobby" levels of work or even small
dinghy makers, polyester is _far_ more common than epoxy. Just the price
of resins is enough to swing it.

Epoxy
is used for the really high-end stuff, but it's expensive and a pain
to work with.

Again, I take exception.

Slightly different methods of layup, but it ain't rocket science.

I've never used epoxy that didn't need vacuum and controlled moderate
heat. This has been with either prepreg carbon, or Kevlar. I've never
used a grade of epoxy that wasn't fussy enough to require this -- when
I've been working at that level, with glass, or 20-30 years ago it was
always just polyester. There are certainly such epoxies around that
aren't so fussy (I use West System for general gluing), although I've
never used it seriously for fibreglass.


Glass/Epoxy ratios of 50-50 are quite common. Higher with vacuum bagging.

Glass/Polyester ratios of 35-65 are about as good as you can get.

Glass/epoxy is much less weight for the same strength.

If you have the skill to achieve that sort of wetting out. "Typical" UK
amateur skill levels (I'm coming to this from the kitcar world) are
often distinctly heavyweight, certainly on the first projects.


Simply adding a bit of resin
and maybe mat to plywood will make the surface harder and may make
attachment points less likely to pull out.

Mat is strictly for polyester, not epoxy.

What do you mean by "mat" ? I'm referring to weaves, as well as choped
strand. Maybe this is a local terminology issue?

Incidentally, there's an epoxy thread in rec.knives at the moment. How
do you best attach scales to a metal frame ?