Blisters above the waterline?

[Tayn95]

Has anyone encountered blisters above the waterline? I have a 1978 Hunter 27 that was sanded below waterline with 5 or 6 coats of Interlux barrier coat four years ago. Everything has been fine and below the waterline still is. This week I removed the shrink wrap to find brown discolored gelcoat and hundreds of bubbles well above the waterline and perfectly aligned with where the bottom of the shrink wrap was. Some have suggested that the heat torch was in one spot too long and damaged the gelcoat, others have told me wicking from the deck but more like from the bottom. Two years ago on the otherside of the boat, I had a 2"x6" section that had very small pin head bubbles in the spring. By mid sailing season they disappeared and to this day you can not find where they were. However, this year the starboard side exploded. Any thoughts on what it could be or cause, as well as hopefully quick and inexpensive (yeah right, never on a boat) fixes?

Thanks

 

[jon hansen]

looks like osmosis blisters to me. educated guess.
great example of why i would never ever ever ever shrink wrap one of my vessels. winter covers need to be able to drain and breath in my opinion.
grew up with dad's wood boats. got let them breath or you got rot.
same with fiberglass. dry dry dry.
this is my opinion, and it is worth only what you paid for it.

 

[jon hansen]

note to your problem: i have seen were osmosis blisters have gone back down. before i spent any money, i would wait 3, 5, 6 months and see what happens.

P.S. you can't see them from the helm chair

 

[Davidasailor26]

You could try to pop one. If smelly water comes out it is some kind of osmotic blister. If not I guess the shrink wrap torch is a possibility. Is the hull cored? I wouldn’t expect water to wick under gelcoat in a solid laminate, but suppose it could through a core.

 

[Knotallthere]

I have the same issue this year on my Hunter 356 after shrink wrapping to the water line. This is the first time I have seen this since wrapping the boat with the mast up. The section with the issue is where the water was trapped/draining. I hope they disappear after the boat sorts in the sun...

 

[jon hansen]

if it comes down to repairing. it's not that big of a job for a skilled glass man/woman. open the blisters. allow to dry, re gellcoat, sand and buff. in six months the sun will blend any slight variations.

 

[dlochner]

Has your boat every been painted? Polyurethane paints need to breathe, covering them with shrink wrap or other plastic will cause small blisters.

 

[thinwater]

I'd stop shrink wrapping the boat from now on. Obviously.

 

[Knotallthere]

Mine is the original gelcoat and I won't be shrink wrapping to the water line in the future...I hope they disappear after the boat sits in the sun. My damage isn't to the same level as Tayn95 but is still very concerning.

 

[thinwater]

Has your boat every been painted? Polyurethane paints need to breathe, covering them with shrink wrap or other plastic will cause small blisters.

This sounds right. I have seen this with other paints. Personal experience?

 

[dlochner]

This sounds right. I have seen this with other paints. Personal experience?

A small example. My mast was made by Hall and painted with Awl Grip. One year I wrapped the base of the mast in a plastic bag to keep if from becoming a bird's nest. When I removed the plastic there were multiple small blisters on the mast. It was a very small area at the base, so it is not noticeable.

Another boater, new to boating, asked about small blisters on his boat after the shrink wrap was removed. His boat had been painted, not sure about the type of paint.

 

[Chenega]

Has your boat every been painted? Polyurethane paints need to breathe, covering them with shrink wrap or other plastic will cause small blisters.

That’s exactly correct... Wrap only to the toenail, don’t cover painted hull - you can see why

 

[kappykaplan]

Wrap only to the toenail,

Toerail? Auto-correct got you!