On 21 Oct 2004 12:49:27 -0700, (Dave Wright)
wrote:

MonteP wrote in message news:

ALL sources say polyester to polyester is not recommended. Use Epoxy
for all repairs of polyester. PERIOD!
I repeat, only idiots and shadetree bubbas (or an
emergency repair) ever use polyester to repaair polyester. I will leave
the details to the jillions of works on the subject.

Monte,

could you provide references for one or two readily available sources
that support your view? I've never had a problem with polyester to
polyester boat repairs. The polyester products I purchased provided
instructions for this type of repair.

So, I'm genuinely curious and open to learning something new.

Thank you very much,
Dave Wright

Here was my experience, for what it's worth:
I have used glass/polyester on old car bodies, in the long-ago.

So without much thought about it, I applied glass/polyester bandaids
to several spots on an older bass-boat, and covered them with
stretched cling-film taped to the hull so as to provide a fair smooth
surface.

The patches looked good, but after several seasons use, I noticed
that the patches were showing a milky interface, and appeared to be
leaking somewhat.

I will try glass epoxy with cling film, next time I need to.

Brian W

Here was my experience, for what it's worth:
I have used glass/polyester on old car bodies, in the long-ago.

So without much thought about it, I applied glass/polyester bandaids
to several spots on an older bass-boat, and covered them with
stretched cling-film taped to the hull so as to provide a fair smooth
surface.

The patches looked good, but after several seasons use, I noticed
that the patches were showing a milky interface, and appeared to be
leaking somewhat.

I will try glass epoxy with cling film, next time I need to.

Brian W


Brian, I like epoxy a lot and never had a problem with epoxy. But I've
also had success with polyester resins too. It often depends on the
type of polyester resin you're using; the isophthalic polyester resins
are better than the ortho-polyester resins. If you attempt the repair
with polyester resin again, maybe after coarse grinding (36 grit),
wash the old laminate down with styrene (folks often seem to use
acetone), it may soften the base somewhat better than acetone and help
to give you a decent secondary bond.

You might find that you can get vinylester resin (5% elong. @ 11,800
psi) cheaper than epoxy (5% elong. @ 12,500 psi). I would guess that
every day knowledgeable technicians evaluate polyester based resin
boats for repair or modification. The goal generally is to produce a
satisfactory repair for the remaining life of the boat at the lowest
cost. It's good to try various materials and methods, especially on
small jobs. If they don't work, try something else. Since all of
these materials are application, process, material, and operator
sensitive, it's sometimes hard to acertain why one individual might
have success and another failure.

Best wishes to everyone in their repair jobs.

Dave Wright