Blisters on fiberglass hull?
 

I have a 12' x 50' Catamaran Cruiser Houseboat, probably best described as a
"camper" or "trailer" sitting on catamarans. Guess you might call it a
"poor mans houseboat" as it's not in the same league as the fancy $250k
jobs.... but suits our purpose beautifully, and we LOVE it.

I was told when we first put it in the water to watch for "blisters" in the
fiberglass hull a few years down the road. Well... here I am a few years
down the road (3 years to be exact), and I DO see some half-dollar sized
places on the hull that must be the aforementioned blisters (3 or 4 down
each catamaran). Nice, smooth bulges about 1.5" in diameter that protrude
about 1/8" off the surface of the hull, almost looks as if there was a
carriage bold head under there that was glassed over.

Is this "blisters"?

What to do? Is this something I could fix myself, or does it need
"professional" work?

Some have said painting the glass hull with an anti-fouling paint will help
prevent this, but I didn't think painting a glass hull was a common
practice.

Any and all suggestions are greatly appreciated.

Thanks in advance...

cricketman

On Mon, 6 Dec 2004 22:25:47 -0500, "cc0080793" wrote:
I was told when we first put it in the water to watch for "blisters" in the
fiberglass hull a few years down the road. Well... here I am a few years
down the road (3 years to be exact), and I DO see some half-dollar sized
places on the hull that must be the aforementioned blisters (3 or 4 down
each catamaran). Nice, smooth bulges about 1.5" in diameter that protrude
about 1/8" off the surface of the hull, almost looks as if there was a
carriage bold head under there that was glassed over.

Is this "blisters"?

Might be. Are they below the waterline or above? If below they are
probably classic gel coat blisters. Yours are moderate in size and
few in number so no cause for panic yet. In small numbers like yours
the most cost effective remedy is individual spot repair. Grind out
the blistered material with something like a die grinder or Dremel
tool, fill with thickened epoxy and sand smooth. The generally
accepted prevention is several barrier coats of epoxy over the entire
hull below the waterline. Antifouling bottom paint is not a water
barrier.

If the blisters are above the waterline they may be "hard spots" where
some structural member inside the hull is trying to poke through.
That should definitely be investigated by a professional. Do you have
a hull warranty from the builder? If so dig it out and give it a
close read.

What to do? Is this something I could fix myself, or does it need
"professional" work?

If you're handy with epoxy work you could probably do it yourself.

Some have said painting the glass hull with an anti-fouling paint will help
prevent this, but I didn't think painting a glass hull was a common
practice.

It's common in many areas to prevent fouling buildup. It will not
prevent blisters however.

cc0080793 wrote:

I have a 12' x 50' Catamaran Cruiser Houseboat....
I was told when we first put it in the water to watch for "blisters" in the
fiberglass hull a few years down the road. Well... here I am a few years
down the road (3 years to be exact), and I DO see some half-dollar sized
places on the hull that must be the aforementioned blisters

uh-oh


Is this "blisters"?

Yep, it sure sounds like it.


What to do?

Are they above the waterline or below?

Either way, the answer is to pop one and see what comes out. If nothing,
then you're OK for now although you'll probably want to do at least a
cosmetic repair at some point.

If you get a slightly obnoxious odor and some colored gunk dribbling
out, then you've got a big problem... the classic hull-destroying
blister pox. What you *don't* want to see is a corresponding dimple
eating into the fiberglass under each blister. They can (and have) eaten
right through hulls. I've seen blisters the size of softballs... even
when repaired that hull wasn't worth much IMHO...


... Is this something I could fix myself, or does it need
"professional" work?

Either way you can fix it yourself if you're handy, and the cures aren't
that far apart. Besides, if you hire a pro to do it, you *still* need to
know how to do it yourself so you can check on him.


Some have said painting the glass hull with an anti-fouling paint will help
prevent this

No, it won't. Painting with a water barrier (usually epoxy) will help.
Antifouling prevents barnacles, not blisters. Starts with the same
letter though ;)

The cure is to grind down each & every blister, fill it with putty, and
then repaint the hull. If you want to prevent the problem from
recurring, even if it's only cosmetic, you'll sand the whole hull and
paint on a "water barrier" type paint and then a nice refinish job over
that. The barrier coat will add to the life of the boat anyway and not
all that much (3 ~ 4 hundred$) to the cost of the job.

Good luck
Doug King

If there are not too many spots to repair I'd rather chip them open with a
screwdriver and let the water out (start with the nastiest looking one as a
test). Blisters can cause local fiberglass layers separation and form a good
entry point for water to start "working" your hull. If they are wet inside
chip the separated layer away, dry it with a towel and a hair dryer, apply
epoxy filler putty and gelcoat locally, sand it and polish out. Before
gelcoat you may apply a thin coat of ester-vinyl resin (cheaper then epoxy)
which is a superb if not the best water barrier. Your problem may be due to
manuf. gelcoat defect (3 years is nothing for a good gelcoat, unless there
are some accelerating factors like a poor original finish quality). I own 3
boats, 2 BR's and a cruiser (15 year old Bayliner, used in salt water as
well) with no single blister on any of them so far (in water for 4
mths/year). Painting the whole bottom with epoxy barrier will most likely
prevent the problem form spreading just like a thin coat of vinyl-ester (did
that 4 years ago on one of my previous boats, after application with a
roller it looked like an automotive cleat coat layer - good gloss,
spray-gun-like flow, minimal yellowing, do the test to see if you like the
results visually, water-barrier properties of vinyl -ester are just superb).
I prefer this over epoxy as you can put a gelcoat over vinyl-ester barrier
layer (this is what I ultimately ended up doing) as opposesd to epoxy which
has to be the top coat (gelcoat will not hold well).
Hope this helps.



"cc0080793" wrote in message
...
I have a 12' x 50' Catamaran Cruiser Houseboat, probably best described as
a
"camper" or "trailer" sitting on catamarans. Guess you might call it a
"poor mans houseboat" as it's not in the same league as the fancy $250k
jobs.... but suits our purpose beautifully, and we LOVE it.

I was told when we first put it in the water to watch for "blisters" in
the
fiberglass hull a few years down the road. Well... here I am a few years
down the road (3 years to be exact), and I DO see some half-dollar sized
places on the hull that must be the aforementioned blisters (3 or 4 down
each catamaran). Nice, smooth bulges about 1.5" in diameter that protrude
about 1/8" off the surface of the hull, almost looks as if there was a
carriage bold head under there that was glassed over.

Is this "blisters"?

What to do? Is this something I could fix myself, or does it need
"professional" work?

Some have said painting the glass hull with an anti-fouling paint will
help
prevent this, but I didn't think painting a glass hull was a common
practice.

Any and all suggestions are greatly appreciated.

Thanks in advance...

cricketman