Here are a bunch of articles on blistering and repairs (if needed).
http://www.yachtsurvey.com/blisters.htm
http://www.marinesurvey.com/yacht/BlisterRepairFail.htm
http://www.hotvac.com/
http://www.osmosisinfo.com/
http://www.daviscoltd.com/nams/Docum...er_Report.html

--


Keith
__
The smoothness of your docking varies inversely with the number of people
watching.
"Geri @earthlink.net" izmackdelete wrote in message
nk.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" wrote in message
oups.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?

On Mon, 21 Mar 2005 04:38:53 -0500, "Eisboch"
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

"Short Wave Sportfishing" wrote in message
...
On Mon, 21 Mar 2005 04:38:53 -0500, "Eisboch"
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



No, actually I consider myself a middle of the road .... oh .... sorry ... I
forgot we were actually talking boats here.
Seriously - I don't know. I just never stopped to think about how a
non-invasive "moisture" meter worked.

Eisboch

Keith wrote:
Meter readings should only be used to measure relative
differences,
Absolutely, what's the controversy in this thread? (not that you're
creating it) Meters do what they purport to do, and as long as one
recognizes that it is a qualitative, relative measurement i.e. comparing
moisture presence in a portion of the hull high above the water line to
sections below -with the anti-fouling removed first of course- the
values given do provide useful information IF it's interpreted correctly.

On Mon, 21 Mar 2005 22:03:14 -0500, prodigal1 wrote:

Keith wrote:
Meter readings should only be used to measure relative
differences,
Absolutely, what's the controversy in this thread? (not that you're
creating it) Meters do what they purport to do, and as long as one
recognizes that it is a qualitative, relative measurement i.e. comparing
moisture presence in a portion of the hull high above the water line to
sections below -with the anti-fouling removed first of course- the
values given do provide useful information IF it's interpreted correctly.

There isn't any controversy - it was initiated by somebody taking
offense at some definitions - got a little huffy about it.

Of course, once asked some questions just for clarification, that
person disappeared, but hey...

No controversy all.

Later,

Tom

One has to remember that a meter only measures *surface* moisture

In article , prodigal1
wrote:

Keith wrote:
Meter readings should only be used to measure relative
differences,
Absolutely, what's the controversy in this thread? (not that you're
creating it) Meters do what they purport to do, and as long as one
recognizes that it is a qualitative, relative measurement i.e. comparing
moisture presence in a portion of the hull high above the water line to
sections below -with the anti-fouling removed first of course- the
values given do provide useful information IF it's interpreted correctly.