Ian,

Interesting thread and just thought I'd add some thoughts.

Remember that strength, rigidity and toughness are not the same. You can make a "rigid" hull that could be easily damaged. As an example, most of the canoes I'm familiar with are going to a semi-flexible hull to minimize hull damage, to allow the hull to flex above the rocks so the canoe can slide over.

If your going to be bouncing your boat off rocks, you probably want some "give" in the hull, if the hull is "rigid" (nothing is completely rigid) the laminate will have to be strong enough to withstand the localized forces on it when the hull doesn't give.

Another consideration, be careful of the core strength. On my 1st boat I used the "standard" layup of 1/4- cedar and 6oz glass, with a double layer on the middle.(ie, 12 oz total inside and out). The hull is fairly "stiff". During a misadventure (out of the water), I damaged the hull in several places. It appears that there was a high local load that crushed the wood and caused damage to the glass. The glass/epoxy is dented but the surface not "scuffed".

BTW, on the 2ed boat, I used "George's" method of thiner wood (3/16-) and multiple layers of thin glass (2 oz). (I agree with much of what he has said) Don't know how it will work out but am hoping for a weight under 50 lbs for a 18.5' boat.

Good Luck Dan