Mark off ply in 1.5"(40mm)intervals across the end to be joined.Next a
line 2" in with a similar set of measurements along it,so that a regular
zigzag is formed when the marks are joined.Using a hacksaw cut out the
lines.The cut end is then placed on the other part to be joined ,lined
up with reference lines & edges.The zigzag is then traced onto the ply
below using a sharp pencil.Extend the lines to provide a guide and cut
the pencil lines out.Sand off rough edges.Place the pieces onto a smooth
flat surface (a thick piece of glass works well) with a bit a plastic
cling film on top after buttering up the cut edges with epoxy.Tack or
otherwise secure the first piece butter up the other piece and jam it
together securing it with a couple of brads to stop it backing off.Lay
another sheet of plastic on top and another bit of glass (I also used a
bit of leftover granite fire hearth tile which did the trick-the key is
to use something absolutely flat and uniform).Then put some heavy
weight on top to press the whole thing down.I used big plastic paint
pails(the ones with lids) filled with water.These stay on until the
glue cures .The epoxy tends to squish out off the joints and you'll find
it forms a fairly uniform layer across the zig zag joint .Sand it off.
The finished join is very strong and looks fantastic when varnished.The
deck of my boat is 3mm Ocoume and it has 3 of these joins .If you want
you could reinforce the underside with a short piece of fibreglass tape.
I commend this method to you.Its hard to make a mess of the job and the
finished join looks better than even a first class scarf joint.A fine
tooth hacksaw is best to use .Be careful to keep the saw straight and
don't overshoot the lines.Please let me know how you get on.This method
was developed by an amateur boatbuilder in Auckland,New Zealand who has
also invented a way of stiching ply not using copper wire.But thats
another story.