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Old 15-06-2013, 09:13   #1
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Any New Osmosis Treatment Techniques

My employer is in the process of buying a boat. the survey however has revealed that the outer and innner laminates have a very high moisture content. there is no signs of blistering though. is there nothing more one can do than removing the entire gelcoat and allowing the boat to stand for several months to dry out? how long should it stand? is there no form of heating that could be used to dry the laminates out quicker? an even greater concern is that hull, which is a composite hull, appears to have moisture inside the foam core - can anyone offer some light on the seriousness of this. As far as I know it is extremely serious, and there's very little one can do.
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Old 15-06-2013, 09:16   #2
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Re: any new osmosis treatment techniques

Hotvac. Problem solved.


How were moisture readings obtained? Be sure this is not a false positive reading on a meter before spending a fortune.
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Old 15-06-2013, 09:35   #3
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Re: any new osmosis treatment techniques

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Hotvac. Problem solved.


How were moisture readings obtained? Be sure this is not a false positive reading on a meter before spending a fortune.
I didn't think that hot vac would dry a wet core. How do you determine that it has a wet core from moisture readings anyway?
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Old 15-06-2013, 09:58   #4
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Re: any new osmosis treatment techniques

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I didn't think that hot vac would dry a wet core. How do you determine that it has a wet core from moisture readings anyway?
You take samples of the core and both skins by delaminating a hole saw disc. Then you compare with readings off the calibration plate that came with the meter.

Hotvac dries wet cores fine. Usually takes a week or two for a medium sized bottom to dry. Not worth doing on balsa, as it will just dry rot and turn to dust after drying.
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Old 15-06-2013, 10:39   #5
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Re: any new osmosis treatment techniques

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Hotvac. Problem solved.


How were moisture readings obtained? Be sure this is not a false positive reading on a meter before spending a fortune.
using a sovereign electronic moisture meter. readings were 23 and 24 - very high moisture. we do not know for sure that the core has moisture, but the surveyor is assuming a high probability of it
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Old 15-06-2013, 10:42   #6
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Re: Any New Osmosis Treatment Techniques

minaret thanks for the reply. tell me about this hot vac method please? how does it work?
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Old 15-06-2013, 10:44   #7
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Re: Any New Osmosis Treatment Techniques

how much cost are we talking here roughly for a 72ft monohull ?
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Old 15-06-2013, 12:12   #8
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Re: Any New Osmosis Treatment Techniques

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how much cost are we talking here roughly for a 72ft monohull ?


Power or sail? Lots of factors. Take a core sample and squeeze it hard between finger and thumb. There should be no detectable moisture. You can also hole saw through the inner skin only and pry it off to obtain core samples that are easy to repair. Be sure you are not reading on bottom paint, this will give a false positive due to copper content. Hotvac is hard to find and not cheap. To dry a core holes must be drilled in the outer skin and then repaired. There are many complexities. Some folks do a home made version. Do a search of the forum to learn more.
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Old 15-06-2013, 12:16   #9
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Re: any new osmosis treatment techniques

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using a sovereign electronic moisture meter. readings were 23 and 24 - very high moisture. we do not know for sure that the core has moisture, but the surveyor is assuming a high probability of it


If you are getting even readings of 23-24 over the whole bottom, it is likely a false positive of some sort. A wet bottom will be all over the place, with some areas reading very high, in most cases. Take readings of the top sides and decks as well for comparison. There is a reason the meter reads "relative" humidity.
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