fiberglass blisters

[mglyon40]

I paid $1,650 for a survey last Friday only to find out that the boat has blisters. I am getting mix readings from people on the importance of or the lack of importance on the presence of these blisters. There are likely 150 blisters the size of a quarter on the hull of this 1980 34ft. double cabin. My mechanic friend from fishing in Alaska says run away from it. The surveyor and the broker and some articles I've read say it's not a big deal anymore. What say you?

There are also 3 large blisters on one side of the keel about 5" in diameter and 2 on the other side about the same place on the other side. they all are say 7' to 8' from the prop moving up the keel toward the bows. I believe this is a structural problem the question here is can this be fixed?

[Slight Adrift]

i've got small osmosis blisters all over the hull (below the waterline obviously) and it is a bit of a pain. every time i haul out i need a few extra days to grind out the blisters. then seal them then re-fibreglass the holes that need it (which is not all, it depends on how deep i grind out each individual blister), then fair, then after all that, do my anti-foul. Everyone i've asked says on a boat my age (1983) you will almost certainly get osmosis (either a little or a lot) of some kind. it cost big $$ to get the boat proper treated by a company. i plan to do the work myself in the next few years just to sort it out once and for all but the answer to your question is: if your willing to go thru the extra work every haul out, not a massive problem. and the question you have to ask someone who knows (where you are) is, what is the likelyhood of finding a boat (in the age bracket your looking at) without osmosis? hope that helps

[boatpoker]

Once you get to 1" blisters it's likely starting to go deeper than simple gelcoat and skinout mat and starts to get expensive once it goes interlaminate which strongly suggests hydrolysis.

A 5" blister ! I bet some serious money that hydrolysis is well involved in that one and delamination is underway ... move along this one sounds like it's best days are waning.

http://www.pcmarinesurveys.com/Osmosis%20testing.htm

[Emoyeni]

I actually read a report of people circumnavigating with a Beneteau in the 80’s where the blisters developed while the boat was still new and was actually repaired by Beneteau under warranty. So I suspect this is just really common on boats of 80’s and 90’s vintage.

[boatpoker]

Originally Posted by Emoyeni

I actually read a report of people circumnavigating with a Beneteau in the 80’s where the blisters developed while the boat was still new and was actually repaired by Beneteau under warranty. So I suspect this is just really common on boats of 80’s and 90’s vintage.

There was a period in the late 70's - early 80's (google "70's oil crisis) when a lot of boat builders switched to the cheaper orthopthalic resins which were more susceptible to this condition and blisters became more common. they later switched back to isopthalic resins which were more resistant but not impervious and blisters became less common.

It wasn't til' they started using vinylester gelcoats and vinylester resins in the skinout mat in the late 90's that blisters became quite rare.

There were other chemical and manufacturing factors but to explain all of those would require a polymer chemistry seminar that I don't have time for.