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William R. Watt
 
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Default Using exterior instead of marine plywoods

yes. you have to look for good sheets with no or few gaps in the in the
interior plys. they usually show up along the edge. and with few
imperfections in the face plays. good sheets can be hard to find.

if you are using douglas fir exterior plywood which is what we have here
in Canada (or marine grade for that matter) it expands and contracts with
changes in temperature and humidiy, particularly direct sunlight, and the
surface cracks ("checks"). you either live with it or you put on 2-3
layers of resin soaked fiberglass to prevent the checking.

if you can get exterior grade meranti which seems to be what amateurs use
for small boats in the USA, it would be better than fir.


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