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. I don't
know how thick the various weights of cloth are, Perhaps you could find out.
The cloth has to be more than filled out to it's thickness with resin to
cover the thread and have a smooth hull. There's also the matter of getting
enough glass and resin on the fir plywood to keep it from developing little
surface cracks (checking) which it does from chages in temp and humidity.
I don't know how much is needed, Storing the boat in the shade is said to
help.

I don't know if you've started to build but meranti (luan) plywood is
cheap, rot resistant, and does not check. I assume because you are using
lumberyard plywood, as I do, that you are interested in a cheap boat. I've
built in lauan and virola (not rot resistant) and just painted. I've also
fished from cheap painted (fir and spruce?) plywood punts. You can't get
spruce plywood any more as far as I know.

Dave Allyn ) writes:
I am building a S&G canoe. I am going to use fiberglass cloth on the
entire outside for extra strength, and to prevent any checking in the
plywood. I'm useing 1/4" BCx plywood.

What weight of cloth would I want to use for this aplication? And the
next question, how would I decide that on future projects? Is there a
general rule of thumb for weight?

One last question, I know I need to tape the inside and outside with
fiberglass tape on the seams, but If I cover the whole outside with
cloth, do I still need the tape on the outside of the seams?

Thanks,

dave


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