Blisters revisited

[CDB101]

My yard finally got around to removing bottom paint on my 36c and after two test sections they found lots of blister. I didn't look at it in person, so I'm going off the pics. They appear small in size and depth, but man there is a lot of them! I've read past posts so I've convinced myself this is only a cosmetic thing. Since its approaching spring I think I'll just fill and fair these areas and make it thru this next season. But for next fall what should I do to remove bottom paint? Maybe the sandblasting is too aggressive? Given the value of the boat I don't really care to fix but since the bottom paint was starting to peel in a few sections I figure I needed to take off the old.

 

[Avenger]

Looks exactly like mine.

We used sand, and it worked very well for us, pretty much negating the need to grind any of the blisters. However, that really depends on the skill of the guy operating the gun.

Then we filled with West epoxy and 407 filler. Sanded, barrier coated and painted. Three seasons ago and no blisters yet.

 

[dsharp]

It depends on what they used to remove the bottom paint. Sandblasting with #3 sand will open blisters or cut through the hull depending on how long you stay in one spot. You can use a less aggressive method to remove the paint then see what you have or keep going like they're doing it and fair and barrier coat like previously stated. It's hard to say from a picture.

 

[saltshaker]

I wouldn't put her back in the water without addressing the blisters. The blisters are usually fine if left alone. Problem is they opened them up when they sand blasted those spots. I'd fix it before a non issue becomes a significant one.

 

[hromberg]

Blisters. How significant are they for performance? On my old sail boat I would pop and fill the big ones but left the little ones be, figuring the only thing looking at em would be the fish. Seems like drag is a bigger deal on a planing hull though.

Anybody got a story about how much performance you gain from a perfectly fair hull alone? Seems like most of the folks that spring for a full osmosis mitigation job do other stuff at the same time, so nobody's ever been able to give me a straight answer.

Understand that hull weight goes up a bit from the added liquid, and that delamination can happen in extreme cases. It's always been my impression though, that if the blisters weren't weakening the structure of the boat they didn't matter that much beyond cosmetic concerns.

 

[Avenger]

We saw a slight speed increase, but as you say it's hard to establish how much of it was bottom texture. While we were doing the bottom we not only stripped off the old paint we also pulled off two dead transducers and their fairing blocks and added a fairing to the strut bases.

So, was it the rough, chipped texture of the 30+ years of old bottom paint, the giant mahogany canoes or dragging the fronts of those strut bases throught the water?

I guess the best answer is D: All of the above.

Is it worth the cost to gain a half a knot? Probably knot... uh, I mean not.

There's more significant losses in fouled running gear than there were gains in our bottom work.

 

[jim rosenthal]

Best treatment for this is to soda or walnut blast the hull, dry it thoroughly, which may take weeks or longer, fill and fair, and barrier coat the bottom and then new paint. Use compounds made for the purpose, don't skimp on the drying time, and follow all the directions carefully. And don't peel the boat. There's debate about this, but I don't think anyone looking at your photos would opine that the bottom needs peeling.

 

[rwappleton]

This is what glass beading looks like. As you can see there are some good blister repairs that are already there. About 250 new ones. They have been ground out and hull is drying now. We are doing a full barrier coating job and it is not cheap but I am told when done paint every three years (three coats ablative) and maybe 5 blisters a haul out.

 

[bobk]

When I did my trawler, I faired with vinyl ester and used 0.035" vinyl ester for barrier coat in three coats. If I recall right (some CRS setting in) there were less than a dozen blisters when I sold it 16 years later.

Bobk

 

[rwappleton]

Our plan is to own the boat for at least 15 years so we feel it will save in the long run. The boat had not been out of the water in 8 years prior to our purchase