On 10 Jun, 21:39, wrote:

I've heard of using fiberglass with
an epoxy/resin that will drastically increase the strength of whatever
you put it on.

Fibreglass is generally used with polyester resins, not epoxy. Epoxy
is used for the really high-end stuff, but it's expensive and a pain
to work with. Unless you've tried GRP already and found it wanting,
then you're best sticking with the cheap stuff.

Although this stuff is easily available, the prices for small
quantities in car spares places are ridiculous too. Any reasonable-
sized city will have a fibreglass specialist selling it far cheaper.

As to the "adding strength" issue, then you have to think carefully
about what "strong" means in your case. 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. However for real strength
in bending, and especially stiffness and resistance to bending, then
you're more likely to make a double-layered fibreglass beam with two
strong surface skins and a weak filler material between them that's
there as a former, not for strength. You can make surfboards and
airplane wings with just a foam core, so you don't need to be using
heavy plywood any more. You might well find yourself going from "GRP
as an addition" into a full-blown GRP structure design, using a core
that's just the lightest wood (or foam) you've got.

There's an awful lot already published about this stuff. Search for
boat or surfboard building advice.

Plan to make several. Most people find it quicker to get it right
second time around, after some pratice. 8-)