"William R. Watt"writes:

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.
snip

Stop by your handy dandy restaurant supply house and buy some plastic and/or
paper cups.

I use, 1 oz, 2 oz & 4 oz to mix small quantities of epoxy.

It's simply NBD.



--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
Visit: http://home.earthlink.net/~lewhodgett for Pictures

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

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Glenn Ashmore wrote:

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.


Absolutely.

I've done a bit of aircraft fiberglass work, but I've bever built a
glass hull.
http://home.flash.net/~lamb01/cowl.htm

I use large syringes from the vet for mixing.
My resin mix is 6:1 by volumn.
60cc of resin in the big shot.
10 cc of hardner in the little one.
Its easy to double that with two shots of each.
But that's about as much resin as I mix in one cup.
For large layups, I premix 140cc in baggies and put them in the fridge.

I don't mean to step on any toes, but since this is a boat building
forum...

West is a commonly recognized epoxy but imho West is NOT a sutable
laminating
resin for making fiberglass parts.
It's fabulous with wood.
But the mechanical properties are low and glass parts tend to be
brittle.

I've used Dow 330 for years, but can't get it any more.
Now I mostly use AeroPoxy.

There are several inexpensive laminating resins listed in Aircraft
Spruce.
There are some expensive resins listed too!

Glassing wood? West is best.
But for glass or carbon parts, there are much better resins.


Richard

Just my opinion, I could be wrong.

"William R. Watt" wrote in message
...
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 use the pump set from West. The easiest way to mix. One push on each pump
and you have a smal dose of the perfect mix.

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.

You can also mix by weight. I have used a digital scale for that. You pour,
for instance, 100 grams of epoxy, followed by 20 grams of hardener. Easy.

I would think that counting drops is a very unreliable method. the drop size
would be very dependant on the viscosity of the calalyst, right?

Meindert

Richard Lamb wrote:

I don't mean to step on any toes, but since this is a boat building
forum...

West is a commonly recognized epoxy but imho West is NOT a sutable
laminating
resin for making fiberglass parts.
It's fabulous with wood.
But the mechanical properties are low and glass parts tend to be
brittle.

I've used Dow 330 for years, but can't get it any more.
Now I mostly use AeroPoxy.

There are several inexpensive laminating resins listed in Aircraft
Spruce.
There are some expensive resins listed too!

Glassing wood? West is best.
But for glass or carbon parts, there are much better resins.


That is correct. That is also why West has a sister line called Pro-Set
which is a laminating epoxy.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Glenn Ashmore ) writes:

I would be real interested inknowing how you would apply 1/4 oz of MEKP
to 6 or 8 square feet of cloth. ;-)

mixed with some resin.


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.

I had a partial one quart can of polyester resin and small tube of
catalyst in the back of the 'fridge from 1981 to 2000 and it was fine. The
twist off cap on the can would sieze up and had to be turned with a pair
of pliers. I've started on another quart can now. From time to time I
still use the small jar of white tinting resin that was with the original.
I still keep it all at the back of the 'fridge.

I wrap opened tubes of PL Premium polyurethane adhesive in plastic and
keep that in the freezer accordign to advice posted in this newsgroup. It
can be months between applications. Works fine.

I let both the polyester and polyurethane warm up to room temperature
before using.
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A number of years ago WEST printed a small article in their 'How To . . .'
magazine. {subscriptions are free, just call them}. It was on just this
subject and included a couple of dimensioned drawings.

The crux of the story/drawings was a method of employing 'stops' or 'steps'
on the pump shafts. By cutting the shapes from some 1/4inch material and
placing the proper 'end' between the pump 'head' and 'base', you can get a
REPEATABLE '50 percent' or '25percent' pump. I used Hardboard and painted
them each a different color and marked them.

With the a 'full pump' discharging approximately 1 ounce of 'mix', I have
the ability to also get 1/2 ounce and 1/4 ounce {approximately} quantities
for those small projects/uses. I use the 5 to 1 formulation . . . and the
set-up works just as well with my 'standard' RAKA epoxy.

Regards & Good Luck
Ron Magen
Backyard Boatshop

"Meindert Sprang" wrote in message
...
SNIP
I use the pump set from West. The easiest way to mix. One push on each
pump
and you have a smal dose of the perfect mix.
SNIP

"Meindert Sprang" ) writes:

I would think that counting drops is a very unreliable method. the drop size
would be very dependant on the viscosity of the calalyst, right?

not so it's noticeable. one drop of catalyst for every 1/2 teaspoon of
resin. the drop squeezes out of a pinhole in a plastic container with a
bit of thumb pressure. works every time for me. I'd be more suspect of the
size of the pinhole but I've had no problems with it.

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Hi Barry

I would have to say that poor skills and bad work practice caused the
failure of the tabbing , not the amine blush of the epoxy.
The first BIG mistake the builder made was not following the designers
specs for construction to the letter.
The second stupid move was not reading the instructions for use of the
product he chose to substitute or being the least bit familiar with it.
I bet he made alot more mistakes too. scary

--
From the rocky shores of the Skykomish river
David Bosworth
http://www.premier1.net/~daveb/
Barry Palmer wrote in message
...
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

Hey Richard, just out of curiosity for the polyester crowd, how many
aircraft builders, hobby and commercial do you know of that ust
polyester?

regards, Ron

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