Blisters on 1991 Beneteay 41s5

[georgetheleo]

I just bought a 1991 Beneteau 41s5 sloop. It has about 100 blisters mostly just above the keel on the hull they are about 3/4 to 1 1/4 dia and 1/16 to 3/16 high. A complete removal of all bottom paint and adding a barrier coat plus repairing the blisters is very expensive-- however it is time for a bottom job but I dont want to spend $8000 for everything. A knowledgeable friend says that a barrier coat may not solve the problem because the blisters may be from air bubbles entrapped during layup and not osmosis or irregular mix of the polyester material. If that is true then a barrier coat will not solve the blister problem. Plaese advise --Thanks Make that 300 blisters!

 

[Davidasailor26]

“Pop” one of the blisters and see if foul smelling water comes out. If so then it’s likely a traditional osmotic blister.

 

[sail sfbay]

1. Break open each blister.
2. Grind away the broken dome of the blister.
3. Scrub until squeaky clean with a stiff brush.
4. Paint the inside of each cavity with epoxy resin.
5. Trowel the filler into the cavity, smooth it, and then fair it.

 

[nightowle]

7. Paint with Interlux, Petit, or similar barrier paint. Then cover with regular bottom paint of your choice.

 

[dlochner]

1. Break open each blister.
2. Grind away the broken dome of the blister.
3. Scrub until squeaky clean with a stiff brush.
4. Paint the inside of each cavity with epoxy resin.
5. Trowel the filler into the cavity, smooth it, and then fair it.

And allow ample time to dry the laminate. Ample meaning months out of the water. If the laminate is wet, simply filling the blisters will not make the problem go away.

A knowledgeable friend says that a barrier coat may not solve the problem because the blisters may be from air bubbles entrapped during layup and not osmosis or irregular mix of the polyester material. If that is true then a barrier coat will not solve the blister problem. Plaese advise --Thanks

If the problem is from air bubbles in the layup, then I would be very suspect of the construction of the boat, especially if there are blisters larger than 1 inch. Air between the laminate and the gelcoat is not uncommon in areas where there is a tight radius. Glass does does not like to make tight bends and sometimes pulls away from the gelcoat in the mold. This is only cosmetic when the gelcoat cracks, there is no air between the layers of the laminate.

Did you have the boat surveyed before purchasing? If so, what did the Surveyor say? Were moisture readings taken?

 

[shemandr]

I think blisters in that area (Corresponding to the bilge) are from fresh water standing in the bilge. The osmotic gradient favors freshwater moving into the laminate. That's why you have to let the hull dry. Months may be necessary. Plenty of time to grind off the bottom paint. I agree with above only treat the afflicted area. Barrier coats mostly work - when directions are followed and the laminate is dry. Make friends with someone who has a moisture meter and start monitoring. You'll need a start point to measure drying progress. Do your best to keep fresh water out of the bilge.

 

[georgetheleo]

I had a boat yard fix all the blisters -cost $8000 they did a superb job

 

[jssailem]

Money well spent. Looks like you put your Covid relief money to a good purchase.

 

[georgetheleo]

Nah, I gave that money to Salvation Army and Humane Society. Its stupid for any Government to give other peoples money away to those who do not need it and cause inflation-, raise the national debt so that their chidren and their children must repay------really really stupid.