Ron Thornton wrote:

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.

Not a single one anymore...

Even most of the kit manufacturers have changed over to epoxy.

OTOH, there is a growing use of vinyl ester resin.
It is catalized and works a lot like polyester, but with better
chemical resistance and much better physical properties.

Richard

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.

Ron Thornton ) writes:

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.

no argument there. the question is when do you NEED the superior
qualities of epoxy?

there are other questions about toxicity and so forth but the question
that most interests me is when epoxy is NEEDED. I've used it as an
adhesive in small quantities and to seal seams in some cases. If I used it
instead of polyester and polyurethane on the small boats I've made it
would double the price with no benefit I can imagine. everything has its
place. I don't consider epoxy to be the only product to use. No amount of
anecdotal evidence or backyard observations as put forward by the epoxy crowd
will change that.

--
------------------------------------------------------------------------------
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

No William, the question is are you qualified to make an informed
decision as to whether poly is good enough. I think not because I like
many others here, none of use having any interest in selling epoxy that
I know of, have worked with this stuff professionally for years at a
technical and engineering level and I doubt that any of us would be
willing to just look at all but the most obvious applications and know
whether epoxy was needed instead of polyester. You can say poly is good
enough all you want but the truth is that you don't really know. All we
are saying is that with todays price difference it is more affordable
than ever to go with epoxy and add an additional margin to a repair or
build.

Regards, Ron

PS for the hovercraft guy. Build one correctly out of epoxy and see how
long its service life is compared to the poly craft.

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

I investigated the accident, and cut out a portion of the joint, and it
probably was amine blush, as the tabbing had contamination from sand and silt
glued already on it at the bad joint, unlikely to have been in the joint when
it was first assembled.

I now have builders put a doubler tab on this critical joint, that is 3 times
as wide, a small addition of weight for a lot of idiot proofing.

Subject: Polyester or Epoxy?
From: "David Bosworth"
Date: Sat, Jan 17, 2004 10:42 AM
Message-id:

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





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

BRBR

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

It should be recognized that compared to boat builders, the airplane crowd
really throws money at a project. (Yeah, I know it is hard to believe there is
an easier way to dispose of excess funds than boating.) The cost of epoxy
over polyester is really not a major factor.

While a Sevtec surface effect vehicle (or sev) may cost the builder about $4000
minus for a 4 place, 30mph over water 25hp garden tractor engined machine, the
airplane builders spend maybe $40,000 and way up, more than half of that
sometimes just on the engine.

Also, skins on aircraft are very light, you cannot walk on them. Boats must
have a much more substantial build, due to this and vastly higher point and
overall loading, so the quantity of resin is far more significant. (Sevtec
does use vinyl ester resin on a manufactured craft, though, primarily as it is
claimed (though maybe not proven) that moisture penetration is less than
cheaper resins. Of course, boats use epoxy for the same reason, maybe a single
coat near at and below the waterline.


Subject: Polyester or Epoxy?
From: Richard Lamb
Date: Sat, Jan 17, 2004 11:10 AM
Message-id:

Ron Thornton wrote:

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.

Not a single one anymore...

Even most of the kit manufacturers have changed over to epoxy.

OTOH, there is a growing use of vinyl ester resin.
It is catalized and works a lot like polyester, but with better
chemical resistance and much better physical properties.

Richard

BRBR


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

Longest is still in service after 18 Years, with no problems caused by use of
polyester resin glass skins over 4.5 lb "Clark Foam".

These surface skimmers have been built with epoxy, and appear to be little
different from the polyester, but possibly the elasticity of the panels is a
little greater, (possibly due to inaccurate mixing) bad news when a lot of the
structure is not governed by strength, but by stiffness.

PS for the hovercraft guy. Build one correctly out of epoxy and see how
long its service life is compared to the poly craft.

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

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

Dunno aboput that, Barry.
My new plane cost me about $6k US.
But then I made most all of the parts rather than
buying parts. Makes a difference.

Richard

Barry Palmer wrote:

It should be recognized that compared to boat builders, the airplane crowd
really throws money at a project. (Yeah, I know it is hard to believe there is
an easier way to dispose of excess funds than boating.) The cost of epoxy
over polyester is really not a major factor.

While a Sevtec surface effect vehicle (or sev) may cost the builder about $4000
minus for a 4 place, 30mph over water 25hp garden tractor engined machine, the
airplane builders spend maybe $40,000 and way up, more than half of that
sometimes just on the engine.

Also, skins on aircraft are very light, you cannot walk on them. Boats must
have a much more substantial build, due to this and vastly higher point and
overall loading, so the quantity of resin is far more significant. (Sevtec
does use vinyl ester resin on a manufactured craft, though, primarily as it is
claimed (though maybe not proven) that moisture penetration is less than
cheaper resins. Of course, boats use epoxy for the same reason, maybe a single
coat near at and below the waterline.

Subject: Polyester or Epoxy?
From: Richard Lamb
Date: Sat, Jan 17, 2004 11:10 AM
Message-id:

Ron Thornton wrote:

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.

Not a single one anymore...

Even most of the kit manufacturers have changed over to epoxy.

OTOH, there is a growing use of vinyl ester resin.
It is catalized and works a lot like polyester, but with better
chemical resistance and much better physical properties.

Richard

BRBR

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

Glenn Ashmore wrote:

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


Thanks.
Haven't seen that one on the shelves tho.
Mostly just West 105.

This is an epoxy plane? My first "plane" cost me $10.98, 1960 prices, it would
be much higher in 2004 dollars. Look at the Sevtec website and follow the
links. No epoxy or polyester was in ght, and I used a free engine, gravity.

Subject: Polyester or Epoxy?
From: Richard Lamb
Date: Sat, Jan 17, 2004 4:27 PM
Message-id:

Dunno aboput that, Barry.
My new plane cost me about $6k US.
But then I made most all of the parts rather than
buying parts. Makes a difference.

Richard
BRBR

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