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Larry,
Thank you for your clear explanation. You are the first
person I know who took such a care to laminate with
polyester. Your high lever of preparation is certainly
the key of your success. Unfortunately most of the people
who have used polyester did it in attempt to save a
wooden boat or to try to waterproof it. And they didn't
wait enough to dry it first. That is why we use to say
that 100% of the boats done with polyester are
delaminating. Now I will say 90%! Pierre
*********** REPLY SEPARATOR ***********
On 2/28/2003 at 9:56 AM wrote:
->Pierre,
->
->The basic problem of covering old wooden boats with
fiberglass is the
->expansion and contraction of the underlying wood with
moisture. Wood
->expands
->more radially, across the planks, than it does axially.
This is what
->tightens
->the seams in a wooden boat when it gets wet. Then the
seam caulking
->compresses shifting the relative position of the planks
to the overlaid
->glass. The Gougeon brothers pioneered the epoxy
encapsulation method for
->new
->construction where the entire plank was saturated with
epoxy sealing out
->the
->moisture. This is impractical in older boats unless you
want to
->fiberglass
->the inside as well as the outside. We achieved a
reasonable degree of
->success
->in covering carvel planked wooden boats by routing out
the caulking, then
->filling with a buttery mixture of polyester and
Cabosil. When this set,
->it
->locked the planks in position. The next step was to
impregnate the planks
->with polyester thinned to almost a watery consistency
with styrene. Sort
->of
->like applying Git-Rot to the entire boat. It converted
the upper layer of
->wood to a polyester/wood composite. Then the boat was
covered with
->fiberglass. If you kept the bilge reasonably dry there
were no problems
->with
->delamination even after ten years. This was in the
early 60s when the
->technique was evolving. With today's high labor rates,
covering an wood
->boat
->for restoration is impractical unless it has a
significant historic or
->sentimental value. Better to use the hull as a mold and
make a new
->fiberglass
->one off boat.
->
->Resorcinol bonding used in older cold molded boats
leaves the outer
->surface
->bare. On the other hand, the expansion problem is much
less. Covering
->cold
->molded boats is just like covering plywood. Surface
preparation is the
->key.
->The first coat of resin must be thin enough to
penetrate the outer wood
->layer. If you don't do the first layer properly, the
bond strength will
->be
->too low.
->
->All this polyester work was done in the days before
room temperature
->setting
->epoxy was freely available to consumers. It is still
too expensive and
->too slo
->w to set to be used for mass produced boats but I agree
that epoxy is the
->choice resin for laminating. Surface epoxy must be
painted to avoid
->sunlight
->deterioration. Vinylester resin is a close second.
->
->Stapling to hold fiberglass from delaminating doesn't
make much sense
->since
->you can pull out a row of staples by hand without much
effort. It does
->help
->when fiberglassing or cold molding in holding the
material in place until
->the
->resin sets. We used Monel staples for this purpose so
we could leave them
->in
->place when putting on the next layer. Steel would
eventually rust and the
->stains would migrate to the surface.
->
->Regards,
->
->Larry Z
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