"Jim Conlin" wrote ...
I figure it'd be somewhat over $10/ft^2.
Core-cell $4-
maybe 4 laminations of:
12 oz. knitted Glass $10/yd = $.80/ft^2/ply
epoxy $70/gal = $.60/ft^2/ply

paint $1/ft^2
plus abrasives, peel ply, fillers, vacuum bag consumables

Vacuum bagging it would be the way to go for bond strength,
but knitted glass? I didn't think that was all that cost
effective?

One thing I would like to mention is that hardware store
F'glass cloth is NOT worth it. It's actually a bit more
expensive than most mail order, plus it's crappy quality.

John M wrote:
Just wondering do you guys that use epoxy for everything also use titanium
for auto body repairs after all it's better than steel. It seems rather
silly to repair a polyester and glass boat which is old with epoxy and the
latest high tech fabrics. Why not try resin infusion too


Actually, it's not silly at all. Secondary bonding with
polyester is rather iffy... nowhere near as strong and
what's more important, less reliable (more prone to voids,
imperfectly mixed resin, more temp sensitive, etc etc) so
it's less likely to achieve it's best strength. Epoxy is not
that much more expensive (considering the expense entailed
by owning the rest of the boat too) and that little extra is
very well worth it IMHO.

The last boat I did extensive rebuild work on was an old
Lightning... considering that I bought new trailer tires &
bearings (or would you advocate buying cheaper used ones?),
new running rigging, new sails, and fairly nice paint (now
this could have been economised on, but would it have looked
as good), the 2 gallons of epoxy that I used to do
structural work was trivial... and I sailed that boat in 20+
knot winds many times, never broke anything that I'd worked
on with epoxy. The first few times I was nervous, but after
that became very confident in the strength of my work. BTW
this included relamating some patches of deck as well as
installing a new mainsheet bridle & traveller, which comes
under quite heavy strain.

OTOH I have seen other boats suffer structural failure in
strong winds... it doesn't look like much fun, but perhaps
the skippers are telling themselves they're glad they didn't
spend the money as they take the pieces home.

DSK

I presume you are saying that all my secondary bonds like bulkheads, liners,
water and fuel tank supports are about to let go. Epoxy has it's place,
ultrlight racing boats where the same strength can be had at much lower
weight and as a glue resorcinol is a pain. I live e in what used to be the
hub of boatbuilding in Canada and have seen many boats new and old repaired
with the same material they were built in that is polyester none that I know
of have yet disintegrated.
John
"DSK" wrote in message
.. .
"Jim Conlin" wrote ...
I figure it'd be somewhat over $10/ft^2.
Core-cell $4-
maybe 4 laminations of:
12 oz. knitted Glass $10/yd = $.80/ft^2/ply
epoxy $70/gal = $.60/ft^2/ply

paint $1/ft^2
plus abrasives, peel ply, fillers, vacuum bag consumables

Vacuum bagging it would be the way to go for bond strength, but knitted
glass? I didn't think that was all that cost effective?

One thing I would like to mention is that hardware store F'glass cloth is
NOT worth it. It's actually a bit more expensive than most mail order,
plus it's crappy quality.

John M wrote:
Just wondering do you guys that use epoxy for everything also use
titanium for auto body repairs after all it's better than steel. It seems
rather silly to repair a polyester and glass boat which is old with epoxy
and the latest high tech fabrics. Why not try resin infusion too


Actually, it's not silly at all. Secondary bonding with polyester is
rather iffy... nowhere near as strong and what's more important, less
reliable (more prone to voids, imperfectly mixed resin, more temp
sensitive, etc etc) so it's less likely to achieve it's best strength.
Epoxy is not that much more expensive (considering the expense entailed by
owning the rest of the boat too) and that little extra is very well worth
it IMHO.

The last boat I did extensive rebuild work on was an old Lightning...
considering that I bought new trailer tires & bearings (or would you
advocate buying cheaper used ones?), new running rigging, new sails, and
fairly nice paint (now this could have been economised on, but would it
have looked as good), the 2 gallons of epoxy that I used to do structural
work was trivial... and I sailed that boat in 20+ knot winds many times,
never broke anything that I'd worked on with epoxy. The first few times I
was nervous, but after that became very confident in the strength of my
work. BTW this included relamating some patches of deck as well as
installing a new mainsheet bridle & traveller, which comes under quite
heavy strain.

OTOH I have seen other boats suffer structural failure in strong winds...
it doesn't look like much fun, but perhaps the skippers are telling
themselves they're glad they didn't spend the money as they take the
pieces home.

DSK

John M wrote:
I presume you are saying that all my secondary bonds like bulkheads, liners,
water and fuel tank supports are about to let go.

Umm, no

... Epoxy has it's place,
ultrlight racing boats where the same strength can be had at much lower
weight and as a glue resorcinol is a pain. I live e in what used to be the
hub of boatbuilding in Canada and have seen many boats new and old repaired
with the same material they were built in that is polyester none that I know
of have yet disintegrated.

If you're talking about the structural 2ndary bonds as put
in by the builder, consider this:
1- they are made under ideal conditions by workmen who
presumably are expert with the materials
2- they still break often enough that it's not uncommon at
all to see grid work, bulkhead tabbing, etc etc, pop loose
from inside the hull.

I was talking about repairs/upgrades done in a garage by the
home handy-man (who in some cases is more expert & produces
higher standard of craftsmanship than the "pro" in the
boatbuilding shop), of which I have also seen many break
loose. If you hang around boats & sailors that push their
boats in hard conditions for a few years, you'll see it
too... and probably hear more. In some cases, a single such
bond failure provides years worth of amusing stories.

Regards- Doug King

John M wrote:
I presume you are saying that all my secondary bonds like bulkheads, liners,
water and fuel tank supports are about to let go. Epoxy has it's place,
ultrlight racing boats where the same strength can be had at much lower
weight and as a glue resorcinol is a pain. I live e in what used to be the
hub of boatbuilding in Canada and have seen many boats new and old repaired
with the same material they were built in that is polyester none that I know
of have yet disintegrated.
John

Hey, I've seen many boats built with polyester that had the
tabbing pull free from plywood bulkheads. You can use
polyester if you like, but given the amount of epoxy you're
talking about for a 20' deck repair, the cost difference is
trivial. And I think 2 x 12 oz biaxial would be ample
for an inside skin, given typical spans you'd find on this
size of boat and a core thickness of = 1/2".

Evan Gatehouse

Subject

Epoxy is an adhesive, polyester is not.

Next.

Lew