: Using Allan's drawing, doesn't one get the 10 1/2" between 9 & 10 if
: using 3/4" thick forms? Assuming the distance "between" two
: forms is measured surface-to-surface.

Keith,

Yes, you would get 10 1/2" using 3/4" thick forms. I was assuming 1/2".

If you haven't already started making the forms you might consider 1/2". I found it useful to be able to move the kayak around from time to time. It gets pretty heavy with 1/2" forms, so 3/4" is only going to make it worse. If you're committed to 3/4", and want to keep the weight down, you could drill a bunch of lightening holes in the forms, which would also provide additional clamping opportunities.

Len Thunberg