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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 09-28-2004
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Hull Moisture

I recently purchased an old boat that had been out of the water for two years. The bottom, which had 20 years of paint on it, tested "dry" by a surveyor with a moisture meter - except for the rudder and the skeg area of the hull. High moisture was also detecte on the aft areas of the deck around the cockpit. The sounding hammer indicated no delamination.

I have since had the hull sandblasted. No blisters underneith. I drilled several small holes (3/16") along the top and bottom of the the rudder and into the skeg area. In all cases, the rudder/skeg material came out dry. Over a period of a week, I got a brown "ooze trail" out of one of the holes on the skeg. I also have put little "windows" of freezer bag secured to rudder/skeg/deck area and taped with electrical tape. The ones I put on the deck showed condensation. Those on the rudder and skeg have not.

If the material from inside the rudder is not damp and I get no condensation under plastic - does that suggest the areas are "dry" (perhaps the moisture meter was influenced by moisture in the surrounding paint)? I''m also thinking about drilling up into the deck area from inside the sail locker and see if the coring comes out damp. Should it be damp to the touch to indicate I hava a problem? Is it conceivable that core and laminate material that feels "dry" to the touch actually still has too high a moisture content and must be dealt with?

Thanks for your answers in advance.
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Old 09-28-2004
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Hull Moisture

Moisture meters are finnicky things. We had our boat surveyed before purchase. The surveyor said the hull was wet all over the place. He also found no delamination. We figured that if it was as wet as he claimed, the water should have frozen and caused delamination in the severe freezes we''d had that winter. We went to get another opinion. The second surveyor placed his meter inside the hull, where there was no paint. It showed no moisture. We''ve had the boat seven seasons now, and have come across a couple of spots that we''ve been suspicious about which are definitely wet and which finally, are starting to delaminate. We''ll see how big they are this fall when I''ll be routing them out (from the inside) and repairing them. Water is insidious, but if you want a really dry boat, you''ll have to trailer it to Arizona and leave it parked behind the house.
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Old 09-29-2004
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Hull Moisture

I had a boat surveyed and the surveyor said the moisture meter pegged everywhere on the hull. The owner was irate, saying that the conductivity of the old layers of copper paint caused the moisture readings. We never followed up on this because we declined the boat due to reported significant delamination from the core in the hull.

But that brown ooze would worry me.

Chas.
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Old 09-29-2004
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Hull Moisture

Not a lot of brown ooze...just a "tear" of it. Inside the hole looks clean and dry as a whistle.

I understand that it is not uncommon to get some brown stuff if there is hull moisture...chemical release and the like....

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Old 09-30-2004
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Hull Moisture

Brown stuff is generally tanic acid. It is produced as a byproduct of the original polyestewr cure in combination with moisture. It will attach the bond between the fiber and the cloth and will permit an accellerated deterioration.

Jeff
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