On Tue, 01 Feb 2005 19:00:17 -0500, DSK wrote:

wrote:
I just took the hull (waterline down) of my Sea Ray 300 Weekender down
to the gelcoat for a bottom job. The hull was supposed to have been
stripped and painted last time, but all the yard did was sand the
waterline down to make it look like they did the entire hull, and then
just painted over the old bottom. As such, when I pulled the boat
last week, I had 6 old bottom jobs to contend with. This time, I'm
doing the bottom myself.


Are you doing any business with this boatyeard in the future? Did you
take pictures of what you found? I'd at the very least consider politely
talking to the yard office manager (who might not know what goes on out
in the sheds).

I'm putting an epoxy barrier coat on the hull, before the ablative
paint goes on. The question is, how many coats of the epoxy do I
need? I've read anywhere from 2 to 6, so I'm shooting for 3, because
the first coat went on fairly thick.

Any advice would be appreciated........


This is a case where some is good & more is better. Since there is no
real evidence that anybody knows for sure what causes fiberglass
blistering, there's really no way to guarantee a cure for it. If you're
going to do all the work, then it seems like at least two or three coats
would be justified. BTW if you're putting on barrier coat, you don't
need gel coat. In fact you don't want it, it's just a soft porous layer
between the coating and the fiberglass. Might as well grind most of it off.

WEST System epoxy claims to be 99.99% impervious to water, it's not
quite as expensive as some of the other stuff. We put on two coats of
that as a base and then 4 coats of fancy barrier.

http://community.webshots.com/photo/...76567441wgBQws

I agree with Doug on the two/three coats, but I disagree with
stripping the gel coat. Stripping isn't going to improve adhesion
unless there is something that I don't understand. As for osmosis
creep past the barrier via the gel coat that hasn't been proven to be
true. There is anecdotal evidence of such a problem, but it's really
anecdotal - no laboratory evidence of blisters happening that way.

My own opinion is that blisters are caused by temperature differential
in marginal areas of resin thickness, but it's my own hairball theory
and not something provable.

Something that I did on my Contender is I used the same color barrier
coat as the bottom paint. Doesn't look to ugly when I haul it and
blast some of the crud off over the summer. :)

Good luck.

Later,

Tom