Barrier Coat to Protect Against Osmotic Blistering

[Pacman]

I have noticed an absence of any real discussion of the problem of osmotic blistering and resulting hull damage.

Several members have mentioned that they keep their boats in the water at moorings or at docks during the sailing season but it seems that many of the pictures that members post show nice clean gelcoat on their bottoms and no mention of blistering.

Here in Florida an unprotected hull will be damaged in a relatively short time and most locals who leave their boats in the water use epoxy barrier coat to protect their hulls from osmotic blister damage and anti-fouling paint is applied over the barrier coat to prevent barnacle growth.

I am wondering: Are Com-Pacs less susceptible to blistering than other makes or are members using other methods to protect their hulls?

A few years back I kept a Barnett Butterfly moored in the water at our summer cabin in Minnesota one year and, when I took the boat out it had blisters so I know this can happen in fresh water as well as salt water.

Q: Do you keep your boat in the water?

Q: Have you had any problems with osmotic blisters?

[wes]

When I bought my 1988 CP19 a year ago, the PO had kept it in the water for almost 6 years without a single haul-out. This was in a freshwater lake here in central NC. When I pulled her out, there were patches of old bottom paint, lots of bare spots, and tons of green slime. I assumed that blister repair was in my future. After a good power washing, to my amazement there was not a single blister. I was able to sand off the remaining patches of bottom paint and start refinishing with no repairs needed. I am forced to conclude that these boats are not very vulnerable to osmotic blistering.

That having been said, I did go ahead and apply the full Interlux bottom treatment (Interprotect 2000E epoxy barrier coat and Micron CSC anti fouling) before I put her back in the water. I'm a little bit of a perfectionist.

Wes

[JBC]

From my ComPac Owner's Handbook:  "Boats blister more readily in fresh water than in salt water because the vapor transmission mechanism is not impeded by the larger salt molecules."  The handbook recommends an epoxy coating before applying anti-fouling paint, if the boat is to be kept in the water.

Jett

[skip1930]

"An epoxy coating before applying anti-fouling paint", I believe that's what was on my boat from the factory, in brown. Than some left over waterbase house paint in brown over the top of that brown. And last 'real' antifouling blue boat paint over everything. Life is too short for sanding.

"I might be free but I'm not cheap!" lol.

It's just the bottom of the boat. The fish don't care. skip.

[brackish]

I keep my boat in the water year round.  It is in a fresh water lake most of the time.  It spends 2-3 weeks in the salt water every year.

I have not had a problem with blisters.  The PO had the boat barrier coated in 2008 then coated with anti fouling but did not remember what was used.  I reapplied ablative anti fouling last Spring and am hoping for at least two seasons.

My 23 is new enough that vinylester resin was used rather than polyester resin, so somewhat less susceptible to osmotic blisters.

[Rob]

I had my 16 for 4 years now its a 1979 that's been updated to a MK 3 ,When I bought it it had a bottom paint coat on her that looked bad and the old owner gave me 2 gallon cans of the stuff he had been using .All he had been doing is going out ever spring and putting on another lite coat .The first winter I owned her I was going to clean it all off and start a new ,still hasn't happened .So over the weekend I did what has been happening to her in the spring for many years another lite coat of West Marine bottom paint ,Right or wrong it seams to work but still looks real bad up close ,Its a good thing I don't want  go fast .I keep the Jolly Rio in a slip all summer fresh water and she winters in the garage  .I guess its one of those things that with a old boat all you can do is make her your own while you have her .Maybe this winter it will be time to clean off all the old paint ? But I still have a 1/2 gallon of paint left .Iam hoping to get her to the slip this weekend Ill have my son there to help he says that [ sailing is going nowhere real slow]

[Mark F.]

I kept my CP-16 moored on a freshwater lake in NC for two months last summer and it blistered.  If I ever decide to repair the blisters, I will definitely coat below the water line with an epoxy barrier coat.  I wish I had known about this problem before I chose to moor the boat.

[Salty19]

Pacman, I hope my album didn't mislead you.  Some pics show clean gelcoat which it was as delivered but it is indeed barrier coated and painted for staying the water all season.
Compacs are better than most boats with regards to blistering, but it would be foolish to push it for a season.  I imagine a few weeks with no protection wouldn't be a big deal provided you waxed the bottom first, but only those who have done it can tell if if any problems occurred.

[skip1930]

I wax clean over the bottom paint. Three coats Mother's wax. Last coat of wax never wiped away.
It's not an ablative paint. but rather a hard coat bottom paint.
On the trailer the wax looks like heck but you wanna bet the bottom never 'sees' water?

skip.