William,

If what you say in true, why not soak all the laminating schedule in
uncatalysed resin lay it up and then spray or brush on a light coat of
catalyst?

The manufacture's published mix ratio's do not seem to be all that open.

If proximity to catalyst is enough the get the polyester material to
cure, then how is it that I have found uncured resin imbeded in
structures a decade or more after the build date?

Back when we used polyester exclusively, never-cure mixes did seem to a
real possibility as well as the heat up while mixing version.

In our shops we have done eperiments with the procedures you have
outlined and did not have the success that you seen to have had. Infact
we were able to show some remarkable failures on test assemblies.

Matt Colie www.southpointechandler.com

William R. Watt wrote:
Backyard Renegade ) writes:


Let me take a minute for anyone who is not clear about mixing the two
products.


Epoxy is risky to work with because the proportions have to be exact and the
mix has to be thorough. If it isn't done correctly the mistake cannot be
corrected once is it on the hull.

Polyester proportions do not have to be as exact or the mixing as
thorough. If the polyester doesn't cure on the hull you can brush on more
catalyst. I have spread uncatalysed resin onto a small plywood hull and
let it soak into the wood for 24 hours before brushing on second catalysed
coat. After allowing another 24 (acutally 18) hours to cure it was
thorougly cured with a good bond into the wood. Uncatalysed polyester
thickened with whatever can be used for filleting which allows unlimited
time to shape and smooth the fillets. Then fibreglass cloth soaked in
catalysed resin can be put over the fillet and the whole thing will cure.

In my opinion polyester is both easier and safer to work with.

For some reason the last polyester I bought doesn't even smell as it
cures. It may be an environmental thing. In some jurisdictions licenced
boatbuilders are not allowed to let gases from curing resins escape into
the atmosphere which has lead to fans and filters being installed and to a
technique which looks like a dry vacuum bagging setup with injected resin.

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Matt Colie ) writes:

In our shops we have done eperiments with the procedures you have
outlined and did not have the success that you seen to have had. Infact
we were able to show some remarkable failures on test assemblies.

Jaques Mertens wrote much the same in an earlier thread on this
never-ending topic.

From the sound of it you are both working on big boats with large cross
sectional areas, eg solid keels, which may explain the differences. I've
only built small plywood boats I can pick up and put on top of the car,
under 50 lb. TF Jones describes using uncatalysed thickened poylester
resin for filleting on a Dobler 16 made out of polyester/fibreglass panels
substituted for the usual plywood panels. The design being discussed in
this thread is also small.

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