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USNA81 07-02-2015 01:08 PM

Moisture behind fiberglass on hullsides
A moisture meter and tapping indicates some moisture bind the fiberglass on the side of my boat just below the rub rail. I suspect the screws holding the hull side rub rail have lost the silicone seal or bead when originally installed. Does anyone have any experience with this this issue know how to remove the moisture or repair it?
Thank you

kulas44 07-02-2015 01:35 PM

Well, to begin with, if its silicone you have more problems than that. It possible that it was never sealed at all, and if it was it was an afterthought. You didnt say if the hull sides are cored but I assume they are. What is the coring material ? Can you access the bolts from the inside, is the rub rail removable ? Saturated coring can be a major problem.

Larry M 07-02-2015 08:04 PM

Can you describe the construction of the affected area? How thick and what is on the inboard side? Pictures? Any info will help. :)

Blissboat 07-02-2015 11:39 PM

According to a reviewer, the hull of the Cutwater 28 is solid fiberglass, with no coring:

However, the decks are cored with Divinycell PVC foam. Is this rub rail right at the hull-deck joint?

USNA81, are you confident that moisture is staying where it shouldn't? Any visual evidence, on the inside or outside of the hull?

The CW 28 is a relatively recent design with lots of interesting features.

bglad 07-03-2015 04:38 AM

Depending on the type meter it could be giving a fall positive. Cutwater hulls are solid fiberglass so it should not have moisture in the sides and hulls that are cored usually don't have core to the edge where the hull deck joint would be. If the inner liner is against the hull there could be moisture trapped between the two. Anything conductive will trigger a moisture meter so wiring, tanks, antifouling paint, etc can give false positives for hull moisture intrusion.

FF 07-03-2015 05:35 AM

Moisture in GRP is a fact of life.

If it does not cause blistering (which it will not on a properly built hull) removing it is not a big worry.

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