I'm building a mini-cup plywood, screw and glue. I want to reinforce the ply with Fiberglas and wondering how many layers of glass would be recommended?

Thanks!

On Sat, 27 Dec 2014 19:20:25 -0800 (PST), Fred Oinka
wrote:

I'm building a mini-cup plywood, screw and glue. I want to reinforce the ply with Fiberglas and wondering how many layers of glass would be recommended?

Thanks!

Firstly, I believe that boat was designed for plywood so the
fiberglass is probably not a structural necessity.

Secondly, you will be adding weight to the boat, for estimating you
can estimate about two times the weight of the glass cloth. If, for
example, you apply 200 gm cloth then you will increase the weight by
approximately 2 times 200 gm per square meter of coverage. Or 800 gm
for coverage of both sides.

Do you plan on covering both sides of the ply or only one? It is
sometimes easier to apply the fiberglass to the ply before you cut to
finally shape.

My suggestion would be 200 gm cloth both sides or perhaps 400 gm one
side.

The mini-cup is 12 ft. overall I believe and for a dinghy that big I
think I would apply 400 gm both sides for the bottom planking and 200
gm both sides for the top sides. I am assuming that the bottom
planking of a dinghy would have more wear an tear than the topsides,
but if the wear on the inside were reduced ( the mini-cup has a
cockpit) it might be worthwhile to cover the bottom planking in the
cockpit with 400 gm and the protected areas with 200.

While you probably know, I would recommend epoxy, not polyester, resin
for attaching the glass cloth.

Glass cloth here is measured in meters and grams but I believe that
200 gm glass would be 6 oz. (per square yard) cloth in U.S. shops.
--
Cheers,

Bruce in Bangkok