douglas fir plywood is know to check (split into surface cracks). I've not
used it but read that it is worse if the boat is left out in the sun. Even
the marine grade will check since it's all from the same tree. The
solution is to cover withe fibreglass and resin to a certain thickness
which I'm afraid I don't know. That would mean starting with thinner
plywood and building up thickness and strength with the fibreglass.
Fibreglass being heavier than wood, you have to allow for the extra weight
in the design.

meranti, another cheap plywood related to lauan, doesn't check like
douglas fir.

the poster asked what kind of plywood is used. a popular marine plywood is
okume. it weighs the same as lauan underlayment, about 1 pound per square
foot for 1/4 inch thick plywood (the lauan is metric and is actually 1/5
inch). as far as weight calculations go they can be substituted in design
calcualtions. I belive okume is the least expensive marine plywood after
douglas fir. I can't be definite because I've never used marine plywood of
any kind. I just looked into it a few years ago. One sheet was $50 in this
area. A sheet of lauan underlayment was $13. That's Canadian dollars.

"Dave W" ) writes:
I built an 18 ft skiff out of CD-X, the cheapest of the cheap. I glassed
the outside and have been slowly glassing all of the inside. Sure would
have been easier earlier. The inside checked looked pretty sorry before
glassing.
Dave
"Ted W Lee" wrote in message
...
What's the current "favorite" for building boats?
Ted in Mich.





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