On Sat, 24 Jan 2009 19:56:30 -0800 (PST), Frogwatch
wrote:

My S2 sailboat is 27 yrs old and the gelcoat is badly chalking. Today
when we went to clean her, the water all round her was milky with the
stuff from the gelcoat. The gelcoat has numerous tiny stress cracks
and thin spots. Over the years, I have tried various polishes with
very little luck. I think that with a lot of work, something could be
done to remove the oxidation and then cover the surface with some sort
of wax or other barrier but this is an extreme amount of work. I have
considered re-painting her topsides but I have never seen this work
well, often it flakes or soon looks worse than the original. The new
coat rarely covers the old stress cracks either. Is there a solution
to this?
I have used a water or alchohol thinned two part epoxy primer on my
home built boats and it adheres very well and I wonder if this stuff
will work as a deck paint over gelcoat.

Having had this problem with both cars and boats I can tell you that
once the coating, be it paint or gel coat, begins to craze the only
solution is to sand it all off, right down to solid material,
fiberglass in the case of a boat. Patch any dings and spray on a
couple of coats of high build epoxy primer. Sand smooth and wash clean
and paint with 2 part polyurethane (NOT epoxy).

I can also assure you, from experience, that any band-aid "fix" that
doesn't include sanding off all the damaged coating is doomed to
failure, either sooner, or later.

Cheers,

Bruce