Greetings,

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.

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........

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

Fair Skies
Doug King

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

WaIIy wrote:
There are more than a few people who understand why a hull blisters.


OK then, explain it to us all.

DSK

Short Wave Sportfishing wrote:
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.

It will improve adhesion over unsanded gelcoat, which isn't likely to be
the surface anyway after stripping off old bottom paint. I was just
saying that if you're putting on a barrier coat, then the gelcoat is
redundant and no great care need be taken to preserve it.

... 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.


There would have to be gaps in the gel coat for that to happen. However,
the interface between the gelcoat and the glass is vulnerable to
outgassing on relatively new (less than two years) boats and if there is
already water in the laminate then this will aggravate the problem
despite barrier coat's preventing further water intrusion.

I think this explains why some boats that have been barrier-coated but
not stripped developed blisters... on warranty, no less...


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.


That can explan a lot of blistering issues I've seen... I don't think
there is one single phenomenon happening with blistering.


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. :)


There's a good idea.

DSK

On Wed, 02 Feb 2005 07:36:39 -0500, DSK wrote:

Short Wave Sportfishing wrote:
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.

It will improve adhesion over unsanded gelcoat, which isn't likely to be
the surface anyway after stripping off old bottom paint. I was just
saying that if you're putting on a barrier coat, then the gelcoat is
redundant and no great care need be taken to preserve it.

Good point.

... 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.

There would have to be gaps in the gel coat for that to happen. However,
the interface between the gelcoat and the glass is vulnerable to
outgassing on relatively new (less than two years) boats and if there is
already water in the laminate then this will aggravate the problem
despite barrier coat's preventing further water intrusion.

I think this explains why some boats that have been barrier-coated but
not stripped developed blisters... on warranty, no less...

That's also a good point - I hadn't considered outgassing as a
problem.

Interesting.

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.

That can explan a lot of blistering issues I've seen... I don't think
there is one single phenomenon happening with blistering.

Agreed.

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. :)

There's a good idea.

I have that problem on my Ranger - the bottom was barrier coated white
and the bottom paint was blue - it can be VERY ugly after a summer or
two.

Lesson learned.

Later,

Tom

On Wed, 02 Feb 2005 14:33:43 GMT, Short Wave Sportfishing
wrote:
I have that problem on my Ranger - the bottom was barrier coated white
and the bottom paint was blue - it can be VERY ugly after a summer or
two.

Lesson learned.
===============================================

When I was racing sailboats down the road from you in Stamford, I
always made the first coat of bottom paint a contrasting color,
usually blue. The top coats were white so the diver could better see
the dirt when cleaning the bottom. When that started to get thin, the
blue would begin to show through indicating that it was time for new
paint.

It all depends on your priorities.

On Wed, 02 Feb 2005 11:03:29 -0500, Wayne.B
wrote:

On Wed, 02 Feb 2005 14:33:43 GMT, Short Wave Sportfishing
wrote:
I have that problem on my Ranger - the bottom was barrier coated white
and the bottom paint was blue - it can be VERY ugly after a summer or
two.

Lesson learned.
===============================================

When I was racing sailboats down the road from you in Stamford, I
always made the first coat of bottom paint a contrasting color,
usually blue. The top coats were white so the diver could better see
the dirt when cleaning the bottom. When that started to get thin, the
blue would begin to show through indicating that it was time for new
paint.

It all depends on your priorities.

LOL!!

Well, I didn't have much choice - I bought this as a demo boat and it
was already done.

Oh well.

Later,

Tom

On Tue, 01 Feb 2005 19:03:13 GMT, wrote:

Greetings,

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.

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........


I did this 6 years ago on my 25' Tiara, due to the same symptoms you
describe. I used Interprotect 2000, and followed the procedure from
the painting guide on the Interlux website - to the letter. Lot's of
work, but 6 years later you'd need a jackhammer to get the epoxy off -
I know, there is a spot on the hull where the epoxy got under the
masking tape, and dried there. Left a small blot of gray on the side
of the hull. Won't come off, even though that particular spot wasn't
exactly prepped properly :-(. Just remember, cleanliness is next to
godliness when it comes to this!!


BTW, I used 5 coats of Interprotect, which I figured would give the
required thickness. And the first two coats of ablative antifouling
were a different color than the top coats - "telltale coats" they call
it, I think. When you start to see the telltale color showing
through, it's time for a couple more coats of the finish color.

Lot's of luck - this is a dirty, nasty job, but the results will save
you much more work in the long run. I'm in the water 10 months a
year, and have never had any regrets.

Just be sure to wear protective clothing, an approved mask, etc.

On Fri, 04 Feb 2005 09:34:50 -0500, Sir Spamalot
wrote:


BTW, I used 5 coats of Interprotect, which I figured would give the
required thickness. And the first two coats of ablative antifouling
were a different color than the top coats - "telltale coats" they call
it, I think. When you start to see the telltale color showing
through, it's time for a couple more coats of the finish color.

Another good idea.

Thanks.

Later,

Tom