Glenn Ashmore wrote:
Spackling past has absolutely no sear strength. If your plug flexes at all
it will crack. Also remember that any imperfection in the plug will be
reproduced in the final product.

I would think about something other than foam for the base. Possibly narrow
1/4" plywood strips. Sand as fair as possible, cover with 2oz scrim cloth
and skim coat it with a thin coat of fairing putty. Sand it very fair to
about 240 grit and spray a couple of coats of Duratec surface primer. Wet
sand with some 600 grit. Now split the plug down the keel line and mount
your moldboard. You want that parting angle as sharp as possible. Polish
the daylights out of it starting with rubbing compound and ending with
McGuire's machine polish. Once you can see your face in it when it is dry,
wash it down well and let it dry over night. Spray a very light mist coat
of PVA followed by several light coats. PVA is very thin so try to avoid
runs by making several light passes rather than one or two heavy coats. Let
it dry for several hours before spraying the first gel coat layer of the
mould. I would strongly recommend a tooling grade gel coat rather than the
normal stuff.

On the hull lay-up I wouldn't worry to much about the part line if it is
tight. You will get a little gel coat seeping into it. Just sand off the
flash and polish out the gel coat.


Forget plaster. It will crack and will take forever to dry.

Wood strips are the traditional way to make a male plug. Plaster
isn't good. You don't have to use plywood, thin battens will work
too. I don't think you need to cover the wood with a layer of glass
for a canoe plug. But you will need a resin based fairing compound -
something with microballons. Sand this with no less than 80 grit,
then switch to a high build sandable primer.

Yes, shrinkage is an issue for polyester layups. Allow about 1% for
lack of a more detailed explanation.

Evan Gatehouse