I would be real interested inknowing how you would apply 1/4 oz of MEKP
to 6 or 8 square feet of cloth. ;-)
I use polyester for molds and things like shower basins and grey water
tanks but compared to epoxy it is a PITA. A quart of resin requires
something between 5 to 10 ml of MEKP depending on the temperature, the
hunidity and the phase of the moon. A ml to much and it turns to gum
before you can get the glass laid tight. If you don't mix it extremely
well it forms jelly beans in the pot. If you are an ounce short you
still have to mix a pint because it is almost impossible to measure that
small amount of MEKP.
With epoxy you just get a squirt of resin and a squirt of hardner and
you have about half an ounce. If it is hot you use a slow hardner. If
it is nice out you use a normal harnder. If it is cold you use a fast
hardner. But it is always a squirt of each.
IF you need a lot the hardware store sell graduated mixing pots for
about $.75 that are good for several sessions.
IF you don't glas very often, epoxy has a shelf life measured in years.
I have never had a can of polyester make it past 9 months after it is
opened.
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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Glenn Ashmore
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