Hull covered in blisters - how to proceed?

[rajjes]

I have owned my 1984 Moody 36S for 13 years and lifted out for 6 weeks every 2 years. The last few times I hauled out I noticed a few blisters but decided to postpone the problem due to other personal priorities. This year was the year to tackle the problem so I hauled out last week and yesterday the yard soda blasted below the water line to expose what is going on. This morning I am still reeling from the shock of what I saw when I went to the yard after the blasting! As shown in the attached pics, the entire hull is covered with blisters. Thankfully not large in size but too many to tackle individually. I am thinking of asking the yard for a full gelcoat peel, but with their rates it will likely not be viable....what options do I have? Is it doable to grind the gelcoat using 40Grit on a foam pad with a variable speed grinder? Appreciate your thoughts....and encouragement

 

[Stemar]

I've no claims to expertise, but my guess is that, yes, it is the "dreaded osmosis", and the blisters are between the layup and poorly adhered gelcoat; blasting has thinned=weakened the gelcoat, allowing the bubbles to swell. I reckon that the only way to cure them is to take the gelcoat down until all the bubbles have gone, allow the hull to dry, with regular fresh water rinses to get the styrene off, fair, epoxy coat, prime & antifoul.

Then there's the lazy man's option, which is to ignore them and go sailing. You'll lose a bit of speed, but probably won't notice, and you'll lose money when you come to sell, but she won't sink under you.

 

[Concerto]

If the blisters do not smell of vinegar when you burst them, then you do not have osmosis. On my 1980 Fulmar I have small blisters every time she comes out of the water. The surveyor when I bought her said they are trapped air bubbles in the gel coat due to poor brushing out as the mix was applied to the mould. This was later confirmed by my local glassfibre expert. Looking at your photos, I suspect your blisters are the same. If so then just burst a section and scrape some Teroson Gel Coat Filler into then and sand smooth. Do this every time you come out of the water and eventually they will all get filled. Minor cost but a little effort.


This was what it looked like when I bought Concerto in 2013.

 

[Bobc]

Paint it with antifoul, put it back in the water, and ignore it. Having it peeled is just throwing good money after bad.

 

[Mark-1]

Buy a copy of Fibre Glass Boats by Hugo Du Plessis:

Amazon.co.uk

Read the section on 'so called' osmosis.

Then sail it for a few more years while you decide what you want to do about it, if anything.