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
copyright legislation. Permission to reproduce it is
specifically denied for mass mailing and unrequested
solicitations. Spamspoof salad by spamchock TM - SofDevCo ®

"BruceM" wrote in message ...
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

No reason at all! But I still say for new construction, epoxy is just
easier to use, guess I am just lazy and want the boat to come out
right the first time without the unaviodable waste of material,
sanding off early cured material, scraping off material that did not
"like" the ambient temp, humidity, or mixing ratio you have chosen to
address the same.
I did build several boats in poly in the beginning, when I finally
broke down and used epoxy, it was a life altering experience, kinda
like going from a tricycle to a Porche...


"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
copyright legislation. Permission to reproduce it is
specifically denied for mass mailing and unrequested
solicitations. Spamspoof salad by spamchock TM - SofDevCo ®

Bruce,

The "ordinary" people are the ones that can best justify epoxy because
the quantity they typically us is small compared to the production user.

To answer your question about why to use epoxy instead of poly is, that
it makes a better repair.

Regards, Ron

I don't recieve e-mail at this address because of spam. E-mail me
at crtsrATmsnDOTcom.

(Ron Thornton) wrote in message ...
Bruce,

The "ordinary" people are the ones that can best justify epoxy because
the quantity they typically us is small compared to the production user.

To answer your question about why to use epoxy instead of poly is, that
it makes a better repair.

Regards, Ron

I don't recieve e-mail at this address because of spam. E-mail me
at crtsrATmsnDOTcom.

But that is really not even much of a factor anymore. To build a 12
foot skiff with flotation and proper materials, it is going to cost
you $250.00 on materials and hardware alone (assuming exterior plywood
hull), and just for ha ha's, say $25 for a set of plans. If you use
poly instead of epoxy, you might save $25 to $30 bucks max on the
whole build and more times than not, I have seen first time builders
end up using 2-3 times more poly than the plan would call for. The
learning curve for mixing poly is treacherous, (bring a good scale and
a calculator too) especially to the home builder that may be building
outdoors, or in a non conditioned barn, tent, etc.

Let me take a minute for anyone who is not clear about mixing the two
products.
With polyester, you must first calculate your catalyst ratio. So many
ounces of resin, to so many drops of catalyst. This mixture is not
only very delicate, but it changes depending on ambient temp,
humidity, how fast you want things to cure and the required
differences in the catalyst mixtures is very minute, and are based on
the starting formula plus the users best guess or experience of how to
alter that formula to suit the conditions at the time. Any very slight
miscalculation in the mix or even how many clouds will pass over
during the application can cause total havoc resulting in a slimy hot
slop all over your boat that is extremely difficult to remove (think
half hardened plastic mixed with cold roofing tar), that is to hard to
scrape, and to soft to sand, or a fast kick which catches you with
only half of your glass saturated, or just gobs up thicker and thicker
as you try to catch up and save something. In both cases the only
solution is a lot of elbow grease and lot's of wasted time and sand
paper, scrapers, and then a re-application.
With Epoxy, the cure rate is also dependant on the temp and humidity
of the work area, but not nearly as fast or as radical. Mixing is done
with calibrated pumps, something like one pump of resin to one pump of
hardener. If you want a faster cure, substitute a "fast" hardener, if
slower is your style or a bigger area to do in warmer weather, use a
slower hardener, no calculators, no precision scales, no guesswork at
all. If your pumps are working properly, and you don't get lazy
mixing, even mistakes will harden nicely to be ground or sanded off.

One extreme case (admittedly the most extreme I am aware of) was a
couple of years ago when I came in very late by e-mail on a build of
"Diablo", a 15 foot Bolger type skiff. The plan calls for 2 1/2
gallons of resin. This guy had a terrible summer of heat and cold,
never really got the mixtures down in his one build. He spent
literally dozens of hours scraping and sanding and just throwing out
resin that either kicked to fast, or not at all. He ended up using 11
gallons of poly on the build at a total cost of over $200 for resin
alone. Not to mention lost thickeners, thinners, brushes, sand paper,
scrapers, time, time, time, time, time... I will stop now, but he has
since built another boat, but this time he used epoxy, no problems.
Now I don't expect any first timer to build Diablo with 2 1/2 gallons
of resin, but certainly 3-3 1/2 should be the max.

One final comment. I do not know what the original poster should do, I
have no experience there, I don't do restores ;-) I also do realize
that poly has it's place in composite shops where big lay-up is done
or for molded parts, but somehow this thread seemed to get hijacked to
my area so I thought I would chime in here. So this has been my
advice, take if for what you paid.
Scotty from SmallBoats.com

I have had hundreds of my customers using polyester resins on my Sevtec surface
skimmer hulls without difficulty, and a few using epoxy, against my advice,
with difficulty. In one case, amine blush of the epoxy caused the failure of
tabbing that held some hull panels together and the result of using a brake,
Yes, a brake on a surface skimmer, at about 35mph, caused the hull bottom to
peel off, fortunately with no significant injuries, even though one person of
three aboard went through the hole in the bottom and came up treading water
behind the craft.

Epoxy is very critical in mix ratio, and that is why scales or proportional
pumps are used, while polyester catalysis is easily done with a small graduate
cylinder, and variations of mix ratio of 20%, which would certainly spell
disaster with epoxy, are of no concern with polyester.

Some structures do benefit from epoxy, but if the structure strength or
stiffness is governed by the glass, not the resin, epoxy may be a waste, except
in long term exposure to warm climate salt water.



Subject: Polyester or Epoxy?
From: (Backyard Renegade)
Date: Thu, Jan 15, 2004 3:00 PM
Message-id:

(Ron Thornton) wrote in message
...
Bruce,

The "ordinary" people are the ones that can best justify epoxy because
the quantity they typically us is small compared to the production user.

To answer your question about why to use epoxy instead of poly is, that
it makes a better repair.

Regards, Ron

I don't recieve e-mail at this address because of spam. E-mail me
at crtsrATmsnDOTcom.

But that is really not even much of a factor anymore. To build a 12
foot skiff with flotation and proper materials, it is going to cost
you $250.00 on materials and hardware alone (assuming exterior plywood
hull), and just for ha ha's, say $25 for a set of plans. If you use
poly instead of epoxy, you might save $25 to $30 bucks max on the
whole build and more times than not, I have seen first time builders
end up using 2-3 times more poly than the plan would call for. The
learning curve for mixing poly is treacherous, (bring a good scale and
a calculator too) especially to the home builder that may be building
outdoors, or in a non conditioned barn, tent, etc.

Let me take a minute for anyone who is not clear about mixing the two
products.
With polyester, you must first calculate your catalyst ratio. So many
ounces of resin, to so many drops of catalyst. This mixture is not
only very delicate, but it changes depending on ambient temp,
humidity, how fast you want things to cure and the required
differences in the catalyst mixtures is very minute, and are based on
the starting formula plus the users best guess or experience of how to
alter that formula to suit the conditions at the time. Any very slight
miscalculation in the mix or even how many clouds will pass over
during the application can cause total havoc resulting in a slimy hot
slop all over your boat that is extremely difficult to remove (think
half hardened plastic mixed with cold roofing tar), that is to hard to
scrape, and to soft to sand, or a fast kick which catches you with
only half of your glass saturated, or just gobs up thicker and thicker
as you try to catch up and save something. In both cases the only
solution is a lot of elbow grease and lot's of wasted time and sand
paper, scrapers, and then a re-application.
With Epoxy, the cure rate is also dependant on the temp and humidity
of the work area, but not nearly as fast or as radical. Mixing is done
with calibrated pumps, something like one pump of resin to one pump of
hardener. If you want a faster cure, substitute a "fast" hardener, if
slower is your style or a bigger area to do in warmer weather, use a
slower hardener, no calculators, no precision scales, no guesswork at
all. If your pumps are working properly, and you don't get lazy
mixing, even mistakes will harden nicely to be ground or sanded off.

One extreme case (admittedly the most extreme I am aware of) was a
couple of years ago when I came in very late by e-mail on a build of
"Diablo", a 15 foot Bolger type skiff. The plan calls for 2 1/2
gallons of resin. This guy had a terrible summer of heat and cold,
never really got the mixtures down in his one build. He spent
literally dozens of hours scraping and sanding and just throwing out
resin that either kicked to fast, or not at all. He ended up using 11
gallons of poly on the build at a total cost of over $200 for resin
alone. Not to mention lost thickeners, thinners, brushes, sand paper,
scrapers, time, time, time, time, time... I will stop now, but he has
since built another boat, but this time he used epoxy, no problems.
Now I don't expect any first timer to build Diablo with 2 1/2 gallons
of resin, but certainly 3-3 1/2 should be the max.

One final comment. I do not know what the original poster should do, I
have no experience there, I don't do restores ;-) I also do realize
that poly has it's place in composite shops where big lay-up is done
or for molded parts, but somehow this thread seemed to get hijacked to
my area so I thought I would chime in here. So this has been my
advice, take if for what you paid.
Scotty from SmallBoats.com


BRBR

Barry Palmer, for A
HREF="http://members.aol.com/sevtec/sev/skmr.html"Sevtec/A

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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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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homepage: www.ncf.ca/~ag384/top.htm
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"William R. Watt" wrote in message
...
Epoxy is risky to work with because the proportions have to be exact and
the
mix has to be thorough.

Pleeeze guys, can someone explain to me what is so difficult about givin the
resin pump and the hardener pump an equal number of pushes and stirring a
mixture firmly for two minutes????

If one cannot perform such a simple task, I think building a complete boat
is out of the question.......

Meindert

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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"Meindert Sprang" ) writes:

Pleeeze guys, can someone explain to me what is so difficult about givin the
resin pump and the hardener pump an equal number of pushes and stirring a
mixture firmly for two minutes????

If one cannot perform such a simple task, I think building a complete boat
is out of the question.......

I tried buying a small quantity of epoxy packaged in twin pumps and had
all sorts of difficulty with it. It never worked smoothly. It was messy. A
lot was wasted. For the small jobs I use epoxy for I only buy it in the
twin squeeze tubes now.

I find it a lot easier counting drops of polyester catalyst than trying to
measure out equal volumes of epoxy resin and hardener. Only one container
is used for measuring with polyester. Overall easier to work with in my
opinion.


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