What is the difference in the following paints for the optimal barrier
coating for a fiberglass hull:

1-one part epoxy

2-two part epoxy

3-LPU

4-somethin' else

What would be the most effective sequence for barrier coating for a boat
that has had nothing done beyond Awlgripping [over 5 yrs ago] ?

Appreciatively,

Courtney Thomas

--
s/v Mutiny
Rhodes Bounty II
lying Oriental, NC
WDB5619

"Courtney Thomas" wrote...
What is the difference in the following paints for the optimal barrier
coating for a fiberglass hull:

1-one part epoxy
2-two part epoxy
3-LPU
4-somethin' else

What would be the most effective sequence for barrier coating for a boat
that has had nothing done beyond Awlgripping [over 5 yrs ago] ?

You probably want something purpose-made as a barrier coat, like the 2-part
Interlux Interprotect 2000E (or follow-on). As for applying over Awlgrip,
follow instructions on the can of whatever you decide on. It will probably
require sanding and a prep wash at a minimum.

First of all, barrier coats should be applied from the boot stripe down
so 2-part LPU is definitely out. Most brands say on the lable that they
are not for use below the waterline.

I did quite a lot of research on permiability and cost before I decided.
I ended up with 4 coats of West 105/205 with about 4lb/gallon powdered
copper. I don't know that the particular brand of epoxy matters other
than it should be 100% solids.

Courtney Thomas wrote:
What is the difference in the following paints for the optimal barrier
coating for a fiberglass hull:

1-one part epoxy

2-two part epoxy

3-LPU

4-somethin' else

What would be the most effective sequence for barrier coating for a boat
that has had nothing done beyond Awlgripping [over 5 yrs ago] ?

Appreciatively,

Courtney Thomas


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Courtney Thomas wrote in message ...
What is the difference in the following paints for the optimal barrier
coating for a fiberglass hull:

1-one part epoxy

2-two part epoxy

3-LPU

4-somethin' else

What would be the most effective sequence for barrier coating for a boat
that has had nothing done beyond Awlgripping [over 5 yrs ago] ?

Appreciatively,

Courtney Thomas

Dont bother. It is my understanding that nearly 80% of all osmotic
blister repairs including overcoating and gelcoat shaving fail. I
have asked several marine surveyors if they have ever seen a case of
hull failure due to osmotic blistering and they have all said "No".
It seems to be primarily an aesthetic problem that hardly affects the
sailing ability of the boat.
It seems that if the glass was not fully wetted with resin, you will
get blisters regardless of what you do. This is the case even on very
high quality boats. The have no effect on hull strength.

Here's what I applied after peeling and drying with the hot-vac system:

3 sessions of 1.5 oz. fiberglass mat with vinylester resin
2 coats Interprotect 1000 - High build epoxy primer
2 coats Interprotect 2000 - 2 part epoxy barrier coat
1 heavy sweep Interprotect VC tar2 - Watertight 2 part epoxy putty
3 coats Interprotect 2000 - 2 part epoxy barrier coat
2 coats antifouling - Petit Trinidad SR (4 gallons).

No blisters after 9 months or so... will continue to report.

--


Keith
__
"All that we do is touched with ocean,
yet we remain on the shore of what we know."
- Richard Wilbur
"Courtney Thomas" wrote in message
...
What is the difference in the following paints for the optimal barrier
coating for a fiberglass hull:

1-one part epoxy

2-two part epoxy

3-LPU

4-somethin' else

What would be the most effective sequence for barrier coating for a boat
that has had nothing done beyond Awlgripping [over 5 yrs ago] ?

Appreciatively,

Courtney Thomas

--
s/v Mutiny
Rhodes Bounty II
lying Oriental, NC
WDB5619

Parallax wrote:
Dont bother. It is my understanding that nearly 80% of all osmotic
blister repairs including overcoating and gelcoat shaving fail.

From what I see around boatyards, that's kind of an overstatement.
Maybe half "fail" but some failures aren't significant. Most of the time
I think it's due to poor prep & not following procedures. Boatyard
workers, and boat owners, are like everybody else in that they do the
things the way they 'think' is right, instead of scrupulously following
instructions.

... I
have asked several marine surveyors if they have ever seen a case of
hull failure due to osmotic blistering and they have all said "No".
It seems to be primarily an aesthetic problem that hardly affects the
sailing ability of the boat.

Probably so, but then how bad would blistering have to get before it
would lead to structural failure of the hull? I have seen "blisters"
that were easily the size of softballs, eating well into the hull
laminate. Is it your contention that this has no impact on the boat?

It seems that if the glass was not fully wetted with resin, you will
get blisters regardless of what you do. This is the case even on very
high quality boats.

??? I'd suggest that "high quality boats" are built with enough
attention to detail that you won't find air bubbles in the laminate. And
I have heard many many explanations for why blisters occur, I don't
think anybody really knows.

... The have no effect on hull strength.

See above. They do if they're bad enough.

Fresh Breezes- Doug King

On Sunday 13 June 2004 1:19 pm in rec.boats.building DSK wrote:

Probably so, but then how bad would blistering have to get before it
would lead to structural failure of the hull? I have seen "blisters"
that were easily the size of softballs, eating well into the hull
laminate. Is it your contention that this has no impact on the boat?

There are no recorded cases of sinkings or structural failure caused
by osmosis. OTOH it is unlikely that any sensible person would put to
sea in a seriously damaged hull to tempt such an event.

In general the repair of small osmosis blisters has more to do with
maintaining resale value than with safety.

--
My real address is crn (at) netunix (dot) com
WARNING all messages containing attachments or html will be silently
deleted. Send only plain text.

Courtney,
I noticed most of the answers to your query focused on 'blister repair'.

I didn't {and still don't} have blisters. My idea was to 'prevent' them, and
to 're-enforce the gelcoat 'skin' of the underwater component of the hull.
First, I applied some thin glass cloth to selected areas that I thought
might need protection from 'impacts'. I then applied 3 coats {about 15
mils} of epoxy . . . the last coat with WEST's 'Barrier Coat Additive'. I
then applied two coats of Pettit's 2-part 'Barrier Coat' . . . adding the
blue 'tint' to the last coat {as a 'flag'}. I then applied Interlux's
'VC-17' bottom paint.

I have since removed the VC, applied a 'Hard, Modified Epoxy' by Pettit,
removed that, and am now using the West Marine 'house brand' ablative . . .
because now she is kept on a mooring. After all this, the bottom is still
'smooth & solid'.

My personal feeling is that the time to apply a 'Barrier Coat' is BEFORE
the first time you apply paint. For what it's worth, I'd call Awlgrip and
see what they recommend. My 'gut' tells me that if the bottom is intact
after 5 years, the best thing may be to simply apply an ablative
anti-fouling and carefully inspect it every year at haul-out. Then give
another coat to replace what has worn away.

Regards & Good Luck,
Ron Magen
Backyard Boatshop



"Courtney Thomas" wrote in message
...
What is the difference in the following paints for the optimal barrier
coating for a fiberglass hull:

1-one part epoxy

2-two part epoxy

3-LPU

4-somethin' else

What would be the most effective sequence for barrier coating for a boat
that has had nothing done beyond Awlgripping [over 5 yrs ago] ?

Appreciatively,

Courtney Thomas

--
s/v Mutiny
Rhodes Bounty II
lying Oriental, NC
WDB5619