Dry out hull before barrier coat

[Alacrity36]

I have a 1982 C&C 37 I recently purchased. The bottom was a little rough, so I went ahead and stripped all the many years of bottom paint off (using Peel Away - it was a lot of work, but beat using one of the many types of sanders I have....they got some use to ensure the hull is bare to the gel coat). The hull was not previously barrier coated. The moisture readings go from 19% just below the water line to 30% just above the keel. They have not changed much at all in the past 3 weeks. I have all the floorboards up, the bilge is bone dry & I keep the boat open whenever the sun's out, I have a fan blowing inside to circulate the air. There's not much humidity in NC this time of year, so I don't have a humidifier going. Does anyone have suggestions to help dry it out ....faster? I'd like to get it fairly dry before applying a barrier coat....at this rate, that may not be until ......late fall

[Minnewaska]

I hate to think its the core that is wet. 30% is very high.

If so, no amount of standing drying is going to bring it down.

[Beersmith]

You need to be cleaning the bare hull frequently. I recommend TSP and hot water with a good brush, or a pressure washer. It will not dry out if the chemicals and whatnot are not rinsed off the hull.

edit: it is all explained here: Boat Hull Blisters : My Wet Hull Won't Dry - by David Pascoe, Marine Surveyor

[Beersmith]

and if you really want it to dry, grind away that gelcoat to bare glass

[rmeador]

IIRC the C&C 37 has a cored hull. Have you checked for delamination? There may be water in the core, in which case you're in for a world of hurt. Did you have it surveyed before buying, and if so what did the surveyor say about the hull's moisture content?

[MikeinLA]

FWIW, when I had a blister job done on my Cat 36 back in the late 80s, there were a ton of people having it done as Catalina used a funky barrier coat for a few years. Anyway, the yard manager was an old timer and insisted on air drying the hull as opposed to the then popular method of tenting the boat and running heaters to speed it up. My boat was on the hard for a few months while it dried out, and that was in relatively dry SoCal. I'm thinking that peeling the gelcoat might allow the hull to dry out better.

Mike

[Maine Sail]

You should see readings like this before barrier coating.



This can take months and months to dry out. A 30% reading is indicative of wet wood as solid glass can't physically hold that much moisture so you'll need to know your meters fiberglass conversion scale. A 30% reading on solid glass, no core, translates to a 3% moisture. Interlux generally wants to see less than 0.30% moisture before applying a barrier coat.


This is the conversion scale for solid fiberglass for the CT-33.

[boatpoker]

17% , 30% .... These numbers mean nothing. Moisture meters can give you a relative reading only in this application. They do not measure moisture !. Unless you are intimately familiar with this specific meter and have seen structures opened up to see what the meter was actually telling you they are of little use.

I have surveyed many of these boats and have yet to see one with dry balsa.
Its time to get a hole saw and see how bad it is. If you barrier coat it now you will be wasting money as the coating will fail within one or two years as all you have done is try to trap the moisture inside.

[centaursailor]

My 30 year old Westerly had what the surveyor described as gel coat blisters, a common failure in this make that rarely goes beyond the gel coat and doesn,t compromise the hull which hull is one inch thick GRP.
He advised I remove a latterly applied barrier coat completely and pop the blisters with a drill point prior to filling and fairing.
The barrier coat was about 2 days work with a scraper and I let the popped blisters sit for a few weeks in the weather ,then covered the boat with a tarp while I filled them with two part filler. Painted them over with International,s micron and anti fouled as normal.
A different surveyor passed the boat last year. He noticed the filling but confirmed the hull was sound with no particular recommendation.
I got a good discount on the asking price due to the blisters and the filler was only about 30 euro, still have half left.
Safe sailing

[paulk]

We had fun with people interpreting moisture meter readings on our hull. The first surveyor told us to run away from what he was certain was a saturated balsa core. Then he proclaimed that he could find no delamination anywhere, despite the saturated cored hull having been subjected to weeks of freezing/thawing cycles. This surprised us, so we brought in a second surveyor, who placed his meter inside the bilge, where there was no bottom paint. It showed dry everywhere the other (from the outside) had shown wet. The outside reading was apparently picking up moisture in the layers of bottom paint... Since then we've had recourse to a hole saw for some more inspections, but overall, the boat's held up well so far. (Knock on wood, if we could find some somewhere around here...)