For more than twenty years, we did almost all the fiberglass work that
we did with one or the other kinds of polyester and then a little bit of
vinylester. These were the industries lead materials. Epoxy was
reserved for high temperature and polystrene foam assemblies largely
because of cost.

In that time I did experience several dozen mix failures (where the pot
kicks too soon or does not harden correctly) and all mixing was done on
a balance - no by guess and by gosh.

Also, while working with polyester, we (my father and I ran the boat
shop) had numerous bond failures in the work we had done. We also
repaired a significant number of bond failures in other people's work -
four that I remember were factory jobs. Two of those factory jobs were
conversions to wheel steer that lost cable turning point anchors.

Shortly before my father died in 1980, we started to change to epoxy.
This was mostly driven by the little pumps that could be used measure
the material for mixing. We soon discovered that, except for large
builds where material was a big part of the overall cost, the epoxy jobs
were at least no more expensive because of the lack of lost material.

I have one mix failure (caused by a helper that did not understand the
mix ratio was 1 pump stroke to 1 pump stroke), and have never been able
to identify a bond failure in my own work.

We now do all or clean up with white vinegar and reserve acetone and MEK
for work outside.

Matt Colie www.southpointechandler.com

BruceM wrote:

As one who has need for some poly glassing I have often thought there should
be another news group for "ordinary" people.
My whole boat is poly so why do some alterations in epoxy?
BruceM


"Terry Spragg" wrote in message
...


Michael O'Dell wrote:

In article ,
"Allan" wrote:


Hi. I'll probably get some thoughts on this. I built a 20' Osprey

Triple

kayak using epoxy resin. Nice boat. Now I'm building an 18' Trident

Power

Cat ( johnsboatstuff.com ). He's recommending epoxy for structural

work and

polyester (either orthothalic or the other one, I can't remember right

now,

would have to look at my plans) for glassing up. Anyway it's the

"better"

polyester. I like the price of the polyester, but..................

Anybody have any thoughts on why I should go all epoxy or use the
epoxy/polyester combo??? Thanks for any comments, thoughts.

Amateur 2nd boat builder in the Great White Frozen North,

Allan



build in epoxy - period.

polyester has no secondary bond strength and not
a lot of primary bond strength. epoxy is not
that much more expensive and could well save
your boat. epoxy actually sticks to the glass
where polyester does not; it merely hardens
*around* the glass fibers. that's why a polyester
laminate peels apart along the surface of the
reinforcement when it goes into failure.

-mo

I guess that's why all my 30 year old poly boats just collapsed
into piles of hairy dust in my backyard, eh? Zero strength, eh?

How do you calculate the cost benefit from this supposed longer
life for epoxy, given that the life span is still generally
indeterminate for both types under reasonable stresses? I have
heard of very few poly boats disintegrating in any remarkably
shorter time than epoxy, even in contests involving rocks and
stuff.

Such extremeist statements suggest you must be a berserker stock
market manipulator with interests and positions in the epoxy
chemicals market bordering so extremely on the insane as to
suggest you sell epoxy mainly to be able to continue to dispose
of toxic chemicals added in small amounts to the resins, just
like some shampoo vendors I suspected of doing just that until
your arguement was so strongly stated and foolishly revealed ;-)

Now, as far as skin irritation and developed allergies and
consequent lifetime sensitivities and costs associated with
respirators, deformed babies, etc, I would favour poly quite
strongly for a hobby builder, especially a relatively
inexperienced one, especially for a first build. Commercially,
the evidence is overwhelming. I cannot imagine anyone smart
enough to be able to afford the costs of epoxy being insensitive
to those cost benefit analyses so evidently performed and adhered
to by professional builders.

You just try to get an informed professional to build in epoxy
and then count the costs.

--
Terry K - My email address is MY PROPERTY, and is protected by
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