[C320-list] Moisture and vinylester

[Jack Brennan]

Google moisture meter and fiberglass hull, and you will find plenty of opinions by knowledgeable surveyors discounting the seriousness of this “problem” on uncored fiberglass hulls.

Polyester resin, which includes gelcoat as well as laminate, normally absorbs some water. So does bottom paint. This is why a good yard allows your hull to dry out for days before doing a bottom job.

So, a high moisture level means little. At best, it’s a sales pitch for an expensive barrier coat, which is not needed unless you have blisters breaking out all over.

Blisters are the recognized sign of problems with fiberglass that is underwater. Even then, blistered gelcoat is not worth worrying about. Only when the blister is into the laminate do you need to start worrying.

Forty years of sailing, I’ve never heard of a fiberglass hull rotting or deteriorating from high moisture with no blisters.

Jack Brennan
Sonas, 1998 Catalina 320
Tierra Verde, Fl.






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From: Graeme Clark<mailto:cg at skyflyer.co.uk>
Sent: Thursday, September 8, 2022 3:19 AM
To: Catalina list<mailto:C320-List at Catalina320.com>
Subject: [C320-list] Moisture and vinylester

Does anyone have any experience or information on moisture ingress testing below the waterline?
Our 320 is up for sale and the prospective buyers surveyor says that the entire hull below the waterline is showing a high reading.
Given that it was lifted out the same morning after four months afloat, that seems obvious, but the outer appearance of the antifouling paint was dry and the surveyor got the same readings from small areas where he had removed the paint
It also appears that the PO had had the bottom epoxy coated, something I thought was unnecessary on a vinylester hull? Or does ours (#366) pre-date the use of vinylester.
Obviously the buyer will be looking to negotiate based on this and I’d like to be able to counter his arguments - fairly - if possible!
Thanks
Graeme
#366, 1966

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