Normal Humidity on a Hull? - SailNet Community

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Old 12-31-2011
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Normal Humidity on a Hull?

Wishing everybody a great night and a great new year, I need the answer to a question:

What is the normal humidity tax on a 5 year old hull of a boat that is out of the water for about 6 months , I mean a fiberglass cored hull?

What is a good percentage, a normal one and a bad one?

Regards

Paulo
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Old 01-01-2012
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come on guys, I need the correct answer to that question!
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Old 01-01-2012
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Reading on wood scale of 10 - 12 % is normal. That means 1 - 1.2 % of humidity in fiberglass. Up to 17 % is acceptable. Below 10 % is dry. 7% on wood scale (0.7%in fiber) is the accepted for application of protective coats such as epoxy. Appliying epoxy to more humid hulls can cause problems later.
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Old 01-01-2012
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I am of no use to you on this question Paulo old friend, but I do hope all is good for you for 2012.

Salute

Andrew
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Old 01-01-2012
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Quote:
Originally Posted by celenoglu View Post
Reading on wood scale of 10 - 12 % is normal. That means 1 - 1.2 % of humidity in fiberglass. Up to 17 % is acceptable. Below 10 % is dry. 7% on wood scale (0.7%in fiber) is the accepted for application of protective coats such as epoxy. Appliying epoxy to more humid hulls can cause problems later.
Thanks,

I am only interested in fiberglass and particularly cored hulls.

For what I understand from what you say, a very dry fiberglass hull will have 0.7% of humidity in the hull, the normal would be between 1.0% and 1.2% and more than 1.7% is not acceptable?

Can you provide some links that permits me to learn more about the matter?

If not can you send me some paper about it by email. I am not doubting you just this is very important to me right now.

Thanks again and a good new year to you.

Paulo
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Old 01-01-2012
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Quote:
Originally Posted by tdw View Post
I am of no use to you on this question Paulo old friend, but I do hope all is good for you for 2012.

Salute

Andrew
A great year to you too.

Maybe you can. I guess you have your Malo surveyed before you bought it. Can you see what were the values of humidity the surveyor found on the hull? You can send the information by private message or email.

Regards

Paulo
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Old 01-01-2012
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Understanding the Moisture Meter / Electrophysics CT-33 Photo Gallery by Compass Marine at pbase.com
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Old 01-01-2012
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The little "moisture meters" marketed for such purposes are fine for giving one an idea of the relative differences in moisture in various locations of a particular hull, but are essentially worthless for determining the absolute water content. In other words, if most of the hull (below the waterline) gives you a fairly tight range of readings and one area (or a few areas) has higher readings that is something about which you should be concerned. However, the "percent moisture" indicted has little or no relationship to the actual amount of moisture in the fiberglass. The little "moisture meters" on the market just can't make that analysis with any reliability across different fiberglass resins, bottom/barrier treatments, etc. Anyone who tells you otherwise registers a pretty high "percent BS" on my patented "BS meter".
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Old 01-02-2012
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Thanks,

The humidity scale that they show in the article confirms what Celenoglu had said about the subject. The surveyor used a bigger and more complex instrument and he says he is going to use an even more powerful one (from another surveyor).

Thanks

Paulo
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Old 01-02-2012
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These figures are generally accepted by the surveyors. You might check "osmosis treatment" or "humidity meters" or combination on google. The figures are from my humidity meters users manual.

Only humidity is not the only measure for osmosis. A good surveyor will check the hull with the meter and by a small hammer.
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