William R. Watt wrote:
Note that the weigth of fibreglass and resin together is 96 lb per cubic
foot (Skeen's Elelments of Yacht Design, 30% fibregalss, 70% resin), and
a 1/4" thick layer is 2 lb per square foot. That makes 1/8" layer 1 lb
per square foot, and 1/16" layer half a pound per square foot.
snip

The above applies ONLY to polyester, mat and roving.

It definitely does not apply to knitted glass and epoxy where the
glass/resin ration is about 50/50.

Also, epoxy/knitted glass laminates are much thinner and lighter weight
than polyester/mat/roving for equal strength.

HTH

Lew