Hull moisture readings ?

Two of our club members are planning to dry out their Corbins and then do bottom work, including epoxy barrier coatings. I may be a third member to do the same. 1. How much credence do you place in moisture readings? 2. What make and model of meter do you use? [Ed. Note: All fiberglass boats are subject to sea water absorption]. Lester Helmus (s/v #010, Insouciance)

a. I took the hull back to the gelcoat in 2001 and then applied 10 coats of MAS epoxy……Iroquois Marine did the work. Cheers, Jeremy

b. If I remember right, the hulls were laid up with vinyl esther resins.[See A44d below.] This should help prevent osmosis blisters. 5 years ago I stripped my bottom down to the gel coat and did not find any blisters. I did use Interlux 2000 (6 coats) before I put on the anti fouling. As far as I know I never had water intrusion in the hull. Moisture meter did find moisture in the deck however, I had the deck completely stripped and all gel coat removed and the deck completely refinished. Some coring needed to be replaced. This work was needed because of careless placement of a point loaded block mounted behind the mast on a flat portion of the deck stressing the area, letting in water. Plywood is not something that tolerates water intrusion well as it will migrate along the grain. I have noticed that the deck laminate is about 1 1/2 to 2 in. thick with the plywood core. The interesting thing about this deck is that the outside fiberglass laminate is only about 1/4 in. thick where the inside is about 1/2 thick. This means all deck repair if needed is done from the outside, much easier to do. Gene Whitney (s/v #069, JOINT EFFORT)

c. I was around when a number of boats were treated in New Zealand. Every moisture meter can provide a different reading. I saw three meters placed on the same spot and they all came up with a different reading. The trick is to do all the work on a boat with the same meter. the numbers are relative. Most people in NZ and OZ were attempting to get their boats down to about 15 percent. it took them about eight months to get there. #043, Balmacara needs to be treated but I would like to get my numbers down to about 12 percent. Turkey may be the place. It is also important to keep the sun off the glass while it is drying. Richard Bacon (s/v #043, Balmacara) [Lester note: Los Angeles would be the place. Our air is extremely dry, especially in the winter when the temperature is at 70 degrees.]

d. We only used conventional resins, no vinyl esther was used. Osmosis and blisters do not have to do with the type of resin used but with the time spent during laminations to roll the air bubbles out of the laminate. Whereas most builders would pop one hull a day out of their molds, we took 4 to 5 days. Hope this will help. Marius Corbin