"Meindert Sprang" ) writes:
"William R. Watt" wrote in message
...

I don't think anyone would recommend polyester as an adhesive.

Noone should, but is happens. I once bought plan for a 15 sailing dinghy.
The building method specified was stich and glue, using glass tape and......
polyester.

I don't recommend it but I've tried but I have used it for taped butts on
a small (virola) plywood boat and its holding up after a couple of
seasons. These butt joins are all above the waterline though, so they
never get wet.

I don't like polyurethane. It needs high clamping force, just like
resorcinol. I tried to laminate a stem once, using PU glue. Didn't work.
It's simply impossible to clamp 10 layers of mahogany around a mould AND
apply a pressure of at least 4 kg/cm2 on ALL layers.

The polyurethane which people use on cheap plywood boats is the thick
construction mastic frequently referred to a "liquid nails". The brand
most often used is Bulldog PL Premuim because its supposed to be stronger.
I've lamainated plywood with PL Premium using weights, and used if for
screwed-and-glued chines, gunwales, and skids. It works fine. There's a
photo on my website under "Boats", "Folding Cabin". I used plastic resin
for my first boat and PL Premium for the other two. Plastic resin requires
a closer fit, more heat (70 deg F vs 50 deg F), and is less tolerant of
repositioning.


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