Proper reinforcement of the centerboard trunk on the INSIDE would be
critical since you don't want the trunk to flex at all and there will be
quite a bit of pressure on the trunk when the board is down. I havn't
seen this design but I think fastening the top of the trunk to a thwart
or seat might be a good way to firm it up.
You might want to radius the edges of the plywood where the board enters
the slot to avoid chipping this edge. I'd coat with glass and tape.
Be sure to make the slot quite a bit wider than you think it needs to be
since the board will swell and you might jam stones up there and a
bigger space seems to keep things open easier. The pivot on the board
should be loose too. I've used an oversised hole with an oversized
nylon bushing that rode on a stub of galvanized pipe threaded on both
ends as the pivot before and it worked well. For a larger boat I'd use
a steel or phosphor bronze pin.

Andrew Butchart wrote:
I'm currently working on a Phil Bolger designed plywood sailing pirogue (the
CSD one). Even though the original design calls for a lee-board, I can't
leave well enough alone and am planning on an off-centre centre-board.

My question is about protecting the hull bottom at the centre board slot.
On previous boats (with a dagger-board), I just added some fibreglass tape
around and overlapping the slot, but I was wondering for this one if perhaps
some sort of shoe would be appropriate, and if so what (inexpensive and easy
to find) materials might be suitable. I'm intending on using this boat in
locations where I will have to paddle up a rocky river to a sailable lake.

Thanks