RE: Rookie needs Help/Advise on fiberglassing a Balsa/Ply Hydroplane
I know this thread is old but the density of water is 800 time that of air, so with that said, 2 oz cloth for the bottom is good but a final coat of .75 to 1 oz cloth over everything including the bottom is a good solid foundation for years of abuse. I like to use west or MAS epoxy resin, think twice before using polyester resin, the cure time is too fast and chances for dryspots or wrinkles is too common. One can of west system has lasted me about 2 years for glassing various planes, for a average small plane it adds about .5 to 1 oz of weight using just .75 glass cloth, for a large aircraft (1/4 scale) it adds about 3 to 6 ozs, but thats using 2 ozs cloth.