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.

--
------------------------------------------------------------------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-freenet email must have "notspam" in subject or it's returned

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.

--
------------------------------------------------------------------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-freenet email must have "notspam" in subject or it's returned

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.

--
------------------------------------------------------------------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-freenet email must have "notspam" in subject or it's returned

"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

"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.


--
------------------------------------------------------------------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-freenet email must have "notspam" in subject or it's returned

"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

"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

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.

--
------------------------------------------------------------------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-freenet email must have "notspam" in subject or it's returned

I have mixed both epoxy and polyester for 35 years and have never had a
batch go bad. It ain't brain surgery. All you have to do is follow
exactly the manufactures directions. I have to agree with Meindert, if
you can't do that, you might want to think about whether you need to be
building a boat with two part resins! Only an amateur would
extrapolate to broad use the brushing on of catalyst over polyester
resin already applied to glass as described by Johns for one boat.
There is not a poly resin supplier in the word that would suggest such a
thing because there is no way to predict what the final properties would
be.

As to epoxy, I have mixed batches from 1 gal. down to 6 drops. Yes 6
drops (5:1 West) off of popsicle sticks for RC model aircraft building.
For larger batches I use any container of suitable size thats at hand
and mark off the ratio with a rule. Gee I'm glad I passed 7th grade
math.

Allan, the bottom line is that it is historically well established thru
industry testing, both lab and field, that epoxy is superior to
polyester in most ways except price. No amount of anecdotal evidence or
backyard observations as put forth by the polyester crowd will change
that.

Regards, Ron

PS. Meindert, I learned to measure epoxy in the lab at GE a long time
ago and was doing it on a balance scale until a couple of years ago I
was corrected by Kern of System Three and several other chemist here.
They all said that now the published ratios for the formulated resins
are for volume only as the weight ratio can be different. I never had
any trouble that I could detect but I do by volume ever since to assure
max mech properties.

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