old threads never die, they just unravel ....

in small boat projects by amateurs on the Internet you'll find lots and
lots of references to brushing a coat of epoxy on plywood panels to seal
them. paint and varnish are much cheaper, they are designed to dry smooth
unlike epoxy, and they are just as waterproof as a coat of brushed on
epoxy. epoxy has some sort of religious hold on amateur boatbuilders. they
assume baptizing their boats with a coat of epoxy blesses the boats with
impermeability and longevity.

how's that kayak design going?

Brian Nystrom ) writes:
"William R. Watt" wrote in message
...

The owner of an epoxy sheathed plywood (okume marine) kayak was showing me
today the deterioration in the surface ply on the inside of the hull. The
builder had let the boat sit outside over the winter mistakenly assuming
epoxy was impervious to H2O. Snow accumulated in the cockpit, melted,
froze, melted again, and by late spring there was 6" of melt water inside
the hull. The epoxy sheathing on the inside of the hull did not stop the
water from getting at the plywood and starting rot. Accept the claims of
epoxy purveyors and promoters at your peril.

How about a few more details? How was the hull sealed? Was it simply a thin epoxy sealer coat or was the inside glassed as well? It makes a huge difference in permeability. Was the epoxy damaged (cracked) by the freeze-thaw cycles?

Let's also remember a couple other points:

- A coat of varnish or paint over the epoxy would have eliminated the problem.

- Simply covering or inverting the boat to prevent water accumulation would have prevented the problem.

The issue here is not any deficiency of the epoxy, but rather a deficiency on the part of the builder.

--
Regards

Brian



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