Osmosis, survey.

[fisherman]

had a survey on my Cygnus F/V 1976 vintage. Osmosis has been present since I bought in 1992, and before to my certain knowledge. The surveyor said broadly the same as the insurance company, more damage done sometimes trying to strip and treat it. I asked if spot treatment was valid, grind out and epoxy fill, he said an angle grinder tends to polish the surface, but slurry blasting would take off the paint and remove and fluff up the blisters. As 99% of the gel is still attached you could paint over it with epoxy, as one F/V owner did about twenty years ago. I didn't know that fresh water causes worse osmosis than salt.

 

[seumask]

If you are trying to cure an osmotic blister without removing the gelcoat and grinding into the affected osmotic layers of fiber glass your barking up the wrong tree. I found that you need to grind out gently with the angle grinder the blister and the surrounding effected layup. This then needs through washing out and dying several times before you fill with appropriate layers of glass and epoxy and filler to get back to the original surface, which depending on its location may or may not need more gelcoat. I would not bother if its below the water line covered in antifoul.

 

[CAPTAIN FANTASTIC]

Is the osmosis getting worse, I doubt it; also, no boat has sunk because of osmosis; its a lot of work for negligible benefit.