Hull & deck moisture readings

I have a question with regards to my new Corbin 39, #042, Blondie Too. It was fairly badly scratched up topsides with Hurricane Katrina. I bought her and had her trucked to my home in Peterborough (ie. from warm to temperate climate). I recently had a friend who was a marine surveyor moisture metre it for me and the results were quite discouraging…it seemed to have high levels of moisture everywhere below the water line and on the deck. I wonder if anyone has had any experience with stripping off the hull gelcoat and recoating it and if so where in Ontario it was done and at what expense. The boat sat in salt water most of its life (it is a 1981) and the surveyor seemed to indicate that the work required wouldn’t be worth the cost in the end and that I should think about scrapping the boat and selling off the new engine, rig etc. I, of course, was discouraged by this and am wondering if anyone has had similar experiences with their vessel. I assume the hull has no wood coring, and that the deck has wood coring…if this is incorrect, I would like to be aware of it as well. Tks. kindly. Best wishes to all in the upcoming holiday season. Bill Swales, (s/v #042, Blondie Too)

a. Bill, Sorry to hear about your experience. Our boat is from 1980 and we are original owners. The hull is cored with 3/4″ Airex (PVC) foam down to about the waterline. Is it possible that this has fooled the moisture meter? The deck is cored with 1/2″ exterior grade plywood. We treated the hull with barrier coating, Interprotect 2000/2001, before launching as a precaution. One way to check for excessive moisture is to drill out a core from the inside skin at the bottom of the Airex zone. Don’t penetrate the outer skin! If you then dig out the Airex you will see if there is visible moisture. I have found that the Airex is well bonded everywhere we have drilled out cores for thru hulls etc. Regards, David Salter (s/v #050, Opportunity) [Ed. Note: Marius Corbin says, ” The hull is cored with Airex down to the turn of the bilge, well below the waterline. Airex is the only core that can be used below the waterline, because it is the only core that is 100 waterproof.”] [Lester, I am sure Marius is right. Our boat is too snowbound at the moment to check but I do recall the double inner skin being fairly well down where I can see it easily, in the aft area. In the attached photo you can see the antiskid tape on the double inner skin stretching down well below the rudder stuffing box base. The latter is slightly below the waterline. David Salter.]

b. Dear Bill: I have worked in boatyards for years, and have owned my Corbin since 1995. My experience is that you shouldn’t worry about the moisture level!!!Surveyors and other boat “professionals” tend to rely on these high-tech gadgets and feel they are the be-all, end-all! If you hang in there and enjoy sailing your new boat, you will soon find that although your boat has been in the water most of its life, you can’t kill a Corbin!!! Marius Corbin, the designer, told me that the reason he went out of business, ultimately, was because he built the boat so tough and strong, it cost more than he could charge. There is NO tougher blue water cruiser, and it is the best suited to cruising, as you’ll find if you research the cruising magazines, who have all voted it the best blue water cruiser over the years, and still do even now! Although your boat probably has blisters under the waterline, as mine did when I first bought her, if you work bit by bit on fixing the problem areas every time you haul out, I think you’ll find, as I did, that eventually you won’t have blister problems anymore (I haven’t seen a blister for three years or more). The hull has a foam core, so there is no problem with wood rotting. The deck, on the other hand, has a plywood core, so you may have some rotting there. However, you’ll probably find that the fibreglass on only one side of the potentially rotten plywood core is probably more than sufficient. I recently cut part of my deck out to add a mini-pilot house, and in the 12-foot cut I went through about 10 saws-all blades, designed to go through nails and concrete. You may have some blisters on the bottom, and you may have some rotten core on the deck, my advice to you is to fix her up so she’ll sail safely, and take her out and enjoy her! As long as the rigging is sound (and the chainplates are attached to solid fibreglass, so no rot there), she will go anywhere! A common problem I’ve watched new boat-owners get into is the addiction to making their boat perfect. I, too, was in this trap, and I found, as did others, that I spent so much money on the boat, I didn’t have any money left to go cruising! Then I met a fellow Corbin owner in Guatemala, who was cruising in an unfinished hull, with his possessions stored in milk crates. I was appalled, until he explained that he bought the boat to SAIL, and he’ll finish it as he goes. I changed my attitude then, too! I have sailed my boat from Ft. Lauderdale throughout the Caribbean and Central America, then on through the South Pacific to New Zealand, back to Fiji, and she now sits in Australia. I did all this in a previously neglected Corbin that was covered with blisters and had a lot of deck rot around the anchor lockers. The total refit started in Mexico in 2000 is still underway, and probably always will be, but she’s a solid, safe vessel that will (and has) gone anywhere. She’s the same boat you have, as are all the other Corbins I’ve met around the world, in various stages of repair. In closing, I don’t ever remember hearing of a boat sinking because of a blister! Repair the necessities and go sailing! Marianne Gardner, (#001, Dolphin Spirit), hull #1 [Ed. Note: Dolphin Spirit was recently sold, Jan. 2010, and sailed from the Barrier Reef to Tasmania, 1500 nm. ]

c. Bill, before we bought our Corbin in 2003, it was abandoned for 11 years, we also metered our boat and found the moisture level was quite high. There were 5 other Corbins in the yard when we surveyed our boat. We moisture metered each and every one of them thoroughly. The hulls all measured quite high on the scale and we were somewhat discouraged. We then tested the hull by lifting each end with the stands, it did not flex anywhere. We then took a core sample and attempted to separate the foam from the glass…good luck with that. It’s tough and will totally ruin the foam before the bond lets go. The boat needed a lot of work, so when we brought it home and needed to do some fairing under the keel, we again lifted the boat with the stands, again no flexure. We would tip the boat forward and aft, lifting the ends of the keel to get to work under them without any problems or flexure. We sealed under the waterline with Interprotect 2000 and are happy with that. That was 3 years ago, we have since crossed the Atlantic and are now in France. Happy to be “out there”. Now my point is this, there could be a meter problem. Different cores give different readings. I don’t know enough about meters to make any more comment than that. But if I were to meter a boat and find it was pure water, but was as strong as steel, and it’s siblings metered the same, I wouldn’t worry too much. The center deck however, was quite wet and we replaced it ourselves. If it doesn’t flex when you jump on it, leave it alone. Have someone stand inside the boat while you bounce on the deck. No flex, no problem! The hull is foam core while the deck is plywood core. Replace the deck core with a proper core material of your choice and sail on. If you’re still thinking of selling your Corbin, write me a note, we may be interested when we get home. Happy Sailing. Paul and Christine Melanson on #058, Quintana. Hull 58, in La Rochelle, France.

d. My Corbin is a 1981. Hull number 101. One surveyor in Ontario, tried to tell me my hull was high in moisture……a second surveyor here in Beaufort NC seems to think it is fine……. I suggest average readings are the thing to go by…and remember the meter will always read high near any metal fittings…..such as the webbing in the rudder…which the first surveyor tried to tell me was highly elevated moisture!!!! #101, Two Pelicans is departing Beaufort NC in 3 weeks time for the Bahamas. Cheers, Jeremy

e. Oh boy, I have to say at first, that I would get another opinion. The deck may indeed have some moisture in it if it has been improperly exposed by drilling holes in it without protecting it from water migration. The deck is cored with plywood, but if it is wet, it can be repaired from the top surface as the top is about ¼ inch frp with ½ plywood core and then the bottom is one half inch in glass. The hull below the waterline is solid glass and above the waterline it is cored with airex foam. If you do not have blisters, I would let the hull dry out over the winter and then strip-off the bottom paint and then apply 5-6 coats of interlux 2001. If there are blisters they may have to be removed depending on how bad they are. Gelcoat stripping can be done, and I would talk to the folks at Bridgeport marina in Sarnia, Ontario to submit a quote; they have done this before. I would not be too discouraged over this, as of now. One of the problems with the Corbin is the gelcoat is too thick. The cracking you may see is from the gelcoat shrinking and it will crack all the way down to the laminate and then go even deeper into the laminate. The good thing is the boat is very heavily built and it has tremendous strength and can be repaired. Good luck on this! Gene Whitney

f. This is my answer to Bill Swales, the lucky owner of a Corbin39. My experience with hull moisture was that in many cases the moisture was in the antifouling paint, not in the core. A second test done after sanding some paint gave much better results. If the boat had been out of the water for a long period of time before the test, it may not be the case. The hull is built with an Airex core fiberglass. Very few boats have that core which is made of pure vinyl, is closed cell and waterproof. Because it is made in a mold, the core was cut in small squares and there is a minute distance between the squares that could form a crack or a bad thruhull, accumulate small amount of water that could trigger a dampness meter. That humidity has no effect on the integity of the hull and I would not worry about it at all. Personally I would not even bother with the epoxy coating. Just do the antifouling paint, put it in the water and enjoy your boat. The core that I mentioned above, Airex together with the thickness of the laminate, is what makes this boat hull so strong. I mean by that, exceptionally strong. For example, a Corbin39 spent 23 days on a coral reef and when it was pulled out, thru the reef (1,000 feet), it had a very small leak that the bilge pump could handle. Three of the engine mounts had broken on account of continuous pounding against the coral reef. Another Corbin39 was hit by a freighter going 14 knots and got stuck on the bulbous bow. It took 20 minutes before the cargo ship slowed down to 5 or 6 knots, so that the sailboat could free itself. The two boats travelled sideways for 20 minutes. Despite this, plus the impact when it was hit, the Corbin39 suffered no structural damage and no leaks. Don’t worry about what the surveyor says. He knows nothing about Corbin 39 sailboats and congratulations on owning one; you can now safely take your family around the world if you want. Marius Corbin

g. Bill, congratulations on your purchase of the Corbin. I purchased my 1982 model in 2002 and at that time it had absolutely no moisture barrier on it. It had been launched each year with simply a coat of wax under the waterline (Lake Ontario). After 20 years the gel coat was pristine. Before I launched it for the first time, I put 6 coats of Interprotect 2000 on it (8 at the waterline). After sailing it one year I decided to haul it and upgrade the systems and the interior. I spent 3 years straight working on this and have learned quite a bit about the Corbins. As mentioned by other owners the hull is indeed a sandwich panel with Airex inside. However, contrary to the advice of some, this Airex core does extend a few feet below the water line. In fact during the retrofit I had to abandon a former thru-hull fitting, and rather than leave it in, I removed it and that was when I learned that the former owner had placed the fitting within the cored area. Upon investigating further, the main water intake fitting was also placed within the cored area. The boat had only these two fittings under the waterline as the former owner was very cautious and limited the thru-hulls to absolute minimum (grey water discharges from a holding tank above the waterline). I took this #050, Opportunity to remove the main thruhull and since I could not practically relocate it I created a solid block of resin by using a 6″ hole saw to cut through the inner fiberglass, removing the Airex core within that 6″ area and pouring in solid resin & mat. I redrilled the main water thruhull and patched the Interprotect. When I was doing this work I discovered a small amount of standing water at the thruhull I was abandoning. The main water intake fitting was completely dry. This concerned me at the time; however despite the standing water the Airex core was not delaminated and was indeed extremely difficult to separate from either layer of fiberglass. I noticed that the core material was in fact cut into small squares as Marius had mentioned which allowed for the water to migrate vertically. My thruhull was only about 5″ from the bottom of the Airex core so I drilled out some 3/16″ holes through the interior layer of fiberglass and let it drain. I left them open for the balance of the year and simply filled them again later with epoxy resin. In total I spent 3 years out of the water after which I had it surveyed for insurance purposes and the surveyor did moisture readings on the hull and deck. Not surprising he found the hull to be well dry and found a few local spots at some deck fittings to be slightly higher. For these deck areas I have drilled from the underside and am leaving them open while I determine if my resealing the deck fittings has elevated the source of the intrusion. From my experience I would tend to believe the advice from the other Corbin owners. I would further recommend you find the lower edge of the Airex core and drill some pilot holes to drain any possible standing water…particularly before the hull freezes. Next year I would remove each thruhull below the waterline and either ensure it is placed in an area of solid laminate or create a solid laminate area and reseat them. This will give you a visual of what is going on down there and peace of mind. Hope this helps & don’t hesitate to contact me if you have any further questions. Jack Verheyden (Hull #127, Kathrian, a “Special Edition”)

h. I recommend that any fiberglass boat intended for use in the tropics be given barrier protection with epoxy. I had a Bristol 29 that had no blister problem for 15 years while in the cool waters of New Jersey. After one year in the Caribbean the entire bottom became full with quarter sized blisters! Lester

i. Re: the deck moisture / delamination: We had high moisture levels at areas where the deck sealant had failed [after drilling holes]. In those areas, holes in the deck core were not sealed at their edges with [epoxy] resin, so if the sealant failed moisture could get into the mahogany deck core. I think moisture meters are good tools but tricky to use. We bought a moisture meter, the same one our surveyor had, so we could monitor the moisture in the deck. Some areas, where he [had] indicated there was high moisture, after we removed that portion of the deck we discovered the mahogany to be dry. We had delamination [in] one of the hatches; it was an easy fix and nothing to worry about. Hope that helps, Stephen Lefneski (s/v #187, Tobaggan)

Category: HULL and DECK