3)Once you use epoxy and knitted glass, you will never consider
polyester again.

Lew

Thanks Lew, I have worked with epoxy before, rebuilding a hatch for my
son's 24-foot sailboat.

I don't know why I though that polyester would be an option, just
ignorance I suppose.. Thus my question..

Best wishes,
-Koos.

On Aug 21, 1:26 am, "Meindert Sprang"
wrote:

Ian Oughtred's Puffin?

Seewww.customware.nl/boats
And that one is entirely glued with epoxy.

Meindert

That's a beautiful dinghy!

Perhaps I should make one like that, for the experience. I'm doing
this as a prelude to making a hard dodger on my sailboat. It won't be
a lapstrake dodger, but perhaps the skills will be beneficial. I don't
know if I need to invest so much time into woodwork skills.. Perhaps I
do?

I really plan to make a fiberglass hard dodger and bimini, with smooth
lines, hard windows, and some wood trim.

-Koos.

On Mon, 20 Aug 2007 19:43:45 -0000, wrote:

What are the relative merits of polyester resin vs epoxy resin?
I think epoxy is somewhat stronger, and kayaks are famous for hitting
rocks. For a dingy that may not matter as much. I heard epoxy costs
more, but if you end up with a lot of work in it, why end up with
something second rate.

Casady

On Mon, 20 Aug 2007 17:18:24 -0700, "Lew Hodgett"
wrote:

wrote:

Did you know that you seem to have posted three copies of the same
message? I don't really mind all that much, but I thought you might
like to know.

Casady

"Richard Casady" writes:

Did you know that you seem to have posted three copies of the same
message?

After the fact, yes.

It was my problem.

Lew

"Lew
Polyester/roving produces a rather brittle, heavy laminate.
Epoxy/knitted glass produces a more ductile, lighter weight laminate.
Pound for pound, polyester and woven roving cost less per pound, but
you use more pounds, so the cost differences tend to disappear.
Epoxy, knitted glass and a 1/2" Airex foam core would produce a very
light weight, bullet proof, dinghy or kayak.
Just remember three things.

1)You will buy a commercial dinghy for less money than you will spend
to build one.
2)You build one because you want to do it.
3)Once you use epoxy and knitted glass, you will never consider
polyester again.


Lew is right on every particular.

Lew is right on every particular.

Yes... but. Lew's Knitted glass - when bought in 'roll' quantites is
about a dollar-a-pound more expensive than woven roving. Traditional
thinking is that woven fabric is used primarily with fiberglass 'mat'
in a polyester layup, one between the other. The basic reason for
this is that the woven, i.e. "over, under, repeat" nature of the w.r.
causes "hollows" where the 'high' strands cross-over the 'low' strands
of glass. The mat (in addition to providing significant bulk, and
sucking up a lot of resin) is thought to "tie" the woven layers
together, by bridging these 'hollows.'

Now, in a large epoxy resin layup one can significantly reduce the
cost, while maintaining adequate strength by continuing to use woven-
roving. The mat is forsaken in favor of a slurry of milled fibers and
a little cab-o-sil mixed to a 'light cream' consistency. That is,
layer of w.r. wet out with straight epoxy. Squeege. Trowel in a
slurry of epoxy / milled fibers / cab-o-sil, then next layer of w.r.
Finish wet-out with straight epoxy. Squeege. Repeat.

The milled fiber + cab-o-sil slurry is filling the hollows and
providing a tie for the next layer of woven fabric. A 10 lb bag of
cab-o-sil is like way cheap, and will last the entire project. A 50
lb bag of milled fibers is similarly inexpensive.

And, becuase we've eliminated the mat, resin-to-glass ratio's of 50 /
50 are easily achived.

So, in a large project where cost is a concern my belief is that one
ought not write-off woven roving as being a suitable material.

MW

wrote:

Lew is right on every particular.

Yes... but. Lew's Knitted glass - when bought in 'roll' quantites
is
about a dollar-a-pound more expensive than woven roving.
Traditional
thinking is that woven fabric is used primarily with fiberglass
'mat'
in a polyester layup, one between the other. The basic reason for
this is that the woven, i.e. "over, under, repeat" nature of the
w.r.
causes "hollows" where the 'high' strands cross-over the 'low'
strands
of glass. The mat (in addition to providing significant bulk, and
sucking up a lot of resin) is thought to "tie" the woven layers
together, by bridging these 'hollows.'

Now, in a large epoxy resin layup one can significantly reduce the
cost, while maintaining adequate strength by continuing to use
woven-
roving. The mat is forsaken in favor of a slurry of milled fibers
and
a little cab-o-sil mixed to a 'light cream' consistency. That is,
layer of w.r. wet out with straight epoxy. Squeege. Trowel in a
slurry of epoxy / milled fibers / cab-o-sil, then next layer of w.r.
Finish wet-out with straight epoxy. Squeege. Repeat.

The milled fiber + cab-o-sil slurry is filling the hollows and
providing a tie for the next layer of woven fabric. A 10 lb bag of
cab-o-sil is like way cheap, and will last the entire project. A 50
lb bag of milled fibers is similarly inexpensive.

And, becuase we've eliminated the mat, resin-to-glass ratio's of 50
/
50 are easily achived.

So, in a large project where cost is a concern my belief is that one
ought not write-off woven roving as being a suitable material.

About the only thing missing from the above is a little spit and some
baling wire.

Lew

On Mon, 20 Aug 2007 20:31:45 -0000, wrote stuff
and I replied:

That;s not quite correct. Polyester dissolves some foams; notably
styrene. PVC foam and urethane foam are not affected. PVC foam is the
best for strength and longevity, but not cheap. It can also be used to
make compound (smooth) lines with a little effort.

Epoxy resins don't dissolve foam but I believe polyester resins do.
Your options would seem to be a small boat or a puddle of foam goo.

paul oman
progressive epoxy polymers


Very good! That's helps me with that question.

Anyone with suggestions on alternate plans, dinghy or kayak with
smooth lines?

Thanks,
-Koos.

Human bevaviour: Bestiality with a brain

On Tue, 21 Aug 2007 11:58:39 -0700, "Lew Hodgett"
wrote stuff
and I replied:


"Richard Casady" writes:

Did you know that you seem to have posted three copies of the same
message?

After the fact, yes.

It was my problem.

Lew

Hey! If you mean what you say, get out there and _say_ it, man! G
Human bevaviour: Bestiality with a brain