Osmosis..Q&A for daysailors.

[Skippercanuck]

Problem: A 1980 O'Day 23 arrived here with a lot of old antifouling build up to be removed. Scraping and sanding down to the gelcoat revealed a small number of micro-blisters were found within a 4 square inch area, right where the boatyard jack-stands had been placed, during summer and winter, for several successive years. Answer: Since the blisters had not yet developed all the way through the gelcoat they were simply sanded out, then epoxy paste-faired and then the whole bottom was re-coated with 5 coats WEST system 105/206/422, and then 2 coats of Interprotect 2000, following mfr directions, and then overcoated with 2 coats Petit Unipoxy anti-fouling. Problem solved, overkilled, even. Cost was 350 bucks and 50 hours labour.Questions: Do trailered boats that do not usually stay in salt or fresh water for prolonged periods usually get osmosis blisters? Is the practice of leaving a boat on a boat stand for years in the rain and freezing weather an issue that contributes to the probability of osmosis occurring? Do most trailersailor owners need to go to the trouble and expense of barrier-coating their boats at some point?

 

[Skippercanuck]

Problem: A 1980 O'Day 23 arrived here with a lot of old antifouling build up to be removed. Scraping and sanding down to the gelcoat revealed a small number of micro-blisters were found within a 4 square inch area, right where the boatyard jack-stands had been placed, during summer and winter, for several successive years. Answer: Since the blisters had not yet developed all the way through the gelcoat they were simply sanded out, then epoxy paste-faired and then the whole bottom was re-coated with 5 coats WEST system 105/206/422, and then 2 coats of Interprotect 2000, following mfr directions, and then overcoated with 2 coats Petit Unipoxy anti-fouling. Problem solved, overkilled, even. Cost was 350 bucks and 50 hours labour.Questions: Do trailered boats that do not usually stay in salt or fresh water for prolonged periods usually get osmosis blisters? Is the practice of leaving a boat on a boat stand for years in the rain and freezing weather an issue that contributes to the probability of osmosis occurring? Do most trailersailor owners need to go to the trouble and expense of barrier-coating their boats at some point?

 

[Dave K.]

Blisters on Trailered Boats?

I. too, don't have a definitive answer to your question but can pass on a little bit of personal experience. The previous owner of my 192 kept the boat in the water for two or three years continuously behind his houseboat. The hull had some sort of a black coating applied over the gel coat and ablative bottom paint over that. During it's stay in the water a number of blister developed, the largest of which might have been as big as a dime. I approached a yard about rectifying the situation and they suggested, since I was going to sail the boat of it's trailer, to wait a while and see what happened. As time passed, the blisters were fewer and fewer and within a year there were none to be found. There are still a few pock marks in the bottom where blisters, like those in contact with the trailer bunks, had burst but the rest of the bottom looks like nothing had ever occured.So, since storing a frequently sailed boat on it's trailer between outings has allowed a blistered hull to recover, I would think that a trailer-sailed boat would not normally need any bottom treatment at all.

 

[Dave K.]

Blisters on Trailered Boats?

I. too, don't have a definitive answer to your question but can pass on a little bit of personal experience. The previous owner of my 192 kept the boat in the water for two or three years continuously behind his houseboat. The hull had some sort of a black coating applied over the gel coat and ablative bottom paint over that. During it's stay in the water a number of blister developed, the largest of which might have been as big as a dime. I approached a yard about rectifying the situation and they suggested, since I was going to sail the boat of it's trailer, to wait a while and see what happened. As time passed, the blisters were fewer and fewer and within a year there were none to be found. There are still a few pock marks in the bottom where blisters, like those in contact with the trailer bunks, had burst but the rest of the bottom looks like nothing had ever occured.So, since storing a frequently sailed boat on it's trailer between outings has allowed a blistered hull to recover, I would think that a trailer-sailed boat would not normally need any bottom treatment at all.