Builders' Forum Archives
Re: fiberglass thoughts
Posted by Laszlo on Oct 16, 2005
One quick rule of thumb is that an experienced worker doing everything right will end up with about an optimum 60/40 weight ratio of glass to epoxy. So if you're using 4 oz glass, that translates into 2.7 oz of epoxy, giving you 6.7 oz per square yard of weight for the sheathing. Mere mortals can expect more :-)
Another way to estimate it is that a good layup will weigh right about the same as water, about 8 lbs/gal. (Charlie's number is for the epoxy only, the glass lightens things a bit.) This means that once you get the boat in the water, the extra layers of outside glass won't affect how it floats since by Archimedes' law they'll be weightless. But they will affect acceleration (starting, stopping and turning) since the mass will still be there.
Finally, if you want more exact numbers, System 3's epoxy book has tables that give weights and coverage amounts for layups and coatings. But it all comes down to what Charlie said - keep the epoxy under control.
In Response to: Re: fiberglass thoughts by Charlie on Oct 15, 2005