High Moisture Readings / Old Boat

Here are a bunch of articles on blistering and repairs (if needed).
<a style='text-decoration: underline;' href="http://www.yachtsurvey.com/blisters.htm" target="_blank">http://www.yachtsurvey.com/blisters.htm</a>
<a style='text-decoration: underline;' href="http://www.marinesurvey.com/yacht/BlisterRepairFail.htm" target="_blank">http://www.marinesurvey.com/yacht/BlisterRepairFail.htm</a>
<a style='text-decoration: underline;' href="http://www.hotvac.com/" target="_blank">http://www.hotvac.com/</a>
<a style='text-decoration: underline;' href="http://www.osmosisinfo.com/" target="_blank">http://www.osmosisinfo.com/</a>
<a style='text-decoration: underline;' href="http://www.daviscoltd.com/nams/Documents/Blister_Report.html" target="_blank">http://www.daviscoltd.com/nams/Documents/Blister_Report.html</a>

--


Keith
__
The smoothness of your docking varies inversely with the number of people
watching.
"Geri @earthlink.net>" <izmack<delete> wrote in message
news:Mao%d.1867$Vi3.969@newsread3.news.atl.earthlink.net...
 > Phew! Thanlks everyone for your responses. I can honestly say I'm now
 > more
 > educated on the matter, yet still pretty indecisive on the purchase.
 >
 > Cheers!!
 >
 > Geri
 >
 >
 > "Izmack" <izmack.RemoveThis@earthlink.net> wrote in message
 > news:1111333838.399894.273960@l41g2000cwc.googlegroups.com...
  >> Hi Everyone,
  >>
  >> We are looking at at late 80's Trojan F32 with very high moisture
  >> readings in the hull, but zero signs of blistering either currently or
  >> in the past. Our surveyor, who was VERY thorough, said the following:
  >>
  >> "Bottom was found in above average condition, having no signs of
  >> blistering,crazing or delamination. High moisture levels were noted,
  >> ranging between 80-100 and some crusty deposits were noted, indicating
  >> laminate hydrolysis. Recommendation to dry store vessel each winter off
  >> season to maintain current good condition. If vessel is left overboard,
  >> some blistering or delamination could be expected over time."
  >>
  >> I know I'm asking for a barrage of opinions, but, considering it's a 16
  >> year old boat and the fact we are first time boat buyers and that the
  >> rest of the survey was above average, what do you all think? And -
  >> will future buyers balk at resale?
  >>
 >
 ><!-- ~MESSAGE_AFTER~ -->

On Mon, 21 Mar 2005 04:38:53 -0500, "Eisboch" <eisboch.DeleteThis@nowhere.com>
wrote:

~~ snippage ~~

 >Whatever floats your boat. Actually, I was trying to recall what limited
 >knowledge I have with ultrasonic nondestructive testing and how it may (or
 >may not) apply in the moisture testing. Ultrasonics are used to test for
 >flaws or inclusions in welds, but can also be used for other materials to
 >measure thickness and changes in the density of the material. My bag was
 >thin films for optics and we but used many of the same laws (Snell's law and
 >others) although we delt with the refractive index of a material rather than
 >it's density. I donno ... just a thought.

Just so that I'm not missing something (which is possible - I'm not
the brightest bulb in the drawer), allow me to explain my thought
process here.

For one thing, water is relatively transparent to ultrasound under
normal conditions. It will reflect hard returns like thermoclines for
example and that is a density change I admit, but the distance from
the surface or transducer, the water is transparent. So in one sense,
yes, it does measure density.

However, when you are dealing with the presence of internal water in a
dense material, how to you measure it? To strain the bowl analogy a
little, what are you measuring for - the presence of a bowl or the
presence of water? If you reflect ultrasound into the bowl and get a
hard return, does that indicate that the entire bowl is solid or that
there is a hard bottom indicating the presence of a bowl?

To my simple mind, to test for the presence of water in any material
you start by measuring resistance to electrical signals (and the
argument can be made about density there also, but there is a subtle
difference). The more water, the less resistance and vice versa.

If you take a uncompromised piece of fiberglass as a base line, flip a
signal through it and use that as zero or base line, any changes have
to be due to decreased resistance to the signal.

Right?

Later,

Tom<!-- ~MESSAGE_AFTER~ -->