On Sun, 20 Mar 2005 21:10:48 GMT, "Don White"
wrote:


"Marley" wrote in message
. ..

Believe it or not, MANY surveyors frequently have no clue that this is
the case.

At a seminarduring our local boat show, the speaker, who is president of an
international surveyors association, said the moisture meter is probably the
last thing he uses during a survey.

Interesting. Did he say why?

Just out of plain old curiosity, what group was he with?

Later,

Tom

I knew I'd be opening a can o' worms!

The Tramex reading he go on the cockpit was virtually zero, to give an idea
of calibration. The foredeck was a spotty 60-100, but Trojans have always
been weak in this area. All soundings were good (including the hull),
except for two small foredeck spots w/ compromised soundings.



"Marley" wrote in message
...
Izmack wrote:
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?


You need to better understand moisture meters and readings.

Moisture meters have to be calibrated very carefully.

For example they are used extensively in determining the amount of
moisture in lumber when it is being or has been cut or kiln dried. In
order to make that determination the user first sets the calibration of
the meter against a known standard. In other words, using a piece of
identical lumber of a specific known moisture content that is kept in a
controlled environment.

In the case of a boat, that is not easily accomplished. In fact is
impossible. You don't have a standard upon which to calibrate the
meter. Bottom line, the actual NUMBER read is completely meaningless. I
repeat, it is MEANINGLESS.

The ONLY results that are really valid when metering a boat relate to
the differences in level found at different points on the hull. A
reading like 80-100 is truly meaningless in a non-calibrated environment.

What DOES hold meaning is if your meter reads a level like 80 everywhere
EXCEPT around a through hull or some other fitting where it reads
substantially higher. That might indicate a problem in the hull where
the through hull is bedded. BUT it might also indicate that the glass
surrounding the through hull is thicker (more dense which reads higher)
for increased strength.

You should also do readings with a meter on the deck, in areas where the
deck is not penetrated (middle of the deck for example) and then around
various fittings like cleats, hatches, winches, etc. Assuming that the
deck is cored with a water permeable material (some are, some aren't), a
higher reading relative to a non-pentrated spot might indicate moisture
in the core. It doesn't mean there is moisture for sure...it means
further investigation is appropriate.

Moisture meters readings of hulls and decks are completely subjective in
nature. The only really useful thing they offer is an indication of
possible problem areas where readings are substantially higher than
other areas.

Even then, further investigation often proves a valid reason for the
reason.

Just to give you an examle of what I mean by calibrating a meter: I can
place my meter on my saloon table and adjust the calibration so that it
reads anywhere from 0 to about 200. So if I set it to 200, does that
mean that my saloon table is completely full of water? No it doesn't, it
means that I set it to 200....nothing more.

Believe it or not, MANY surveyors frequently have no clue that this is
the case.

\
This advice is completely wrong and completely backwards.

Did the surveyor mention how extensive the moisture was? Was it
specifically located or an overall condition? What is the rating of
the moisture - 80 to 100% or was that a measuring scale and what
percentage would that reading indicate? Some moisture readers work
on a readable scale - some display direct moisture percentage.

Without calibration (which is IMPOSSIBLE) the "value" read is
completely, utterly meaningless. If you just stop and think about it,
you can not come to any other logical conclusion.


If it's only a local condition at one or two points in the hull, then
I wouldn't worry about it - for a 16 year old boat, that's not bad at
all.


100% incorrect. Bad advice.

If the readings are consistent all over the hull, it's not a bad thing.
If specific areas show higher readings those areas require further
investigation. Period.

If it's an overall condition in the hull, then I wouldn't buy it -
something has gone wrong with the gel coat and the hull is
compromised. You could be looking at future problems which could make
it more expensive than you bargained for.


A reading that is meaningless but consistent through out the entire hull
is a GOD think. Its VARIANCES that suggest that there might be something
going on.

You may not have blisters now, but the it's likely that you will have
them in the future.

Rubbish.

Moisture readings are one and only one tool in the arsenal. If high
readings are found in specific areas, the first thing to do is figure
out why. Frequently there is a simple, logical reason that has nothing
to do with moisture in the hull.

Just to make it really clear, perhaps you didn't know that Moisture
meters don't measure moisture. They measure DENSITY and density
increases with moisture content. It also increases where the hull is
thicker, and where bulkheads meet the hull, and for a hundred other
reasons.

Old wives tales can be very costly.

Short Wave Sportfishing wrote:

On Sun, 20 Mar 2005 15:36:54 -0500, Marley wrote:


Izmack wrote:

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?


You need to better understand moisture meters and readings.

Moisture meters have to be calibrated very carefully.

For example they are used extensively in determining the amount of
moisture in lumber when it is being or has been cut or kiln dried. In
order to make that determination the user first sets the calibration of
the meter against a known standard. In other words, using a piece of
identical lumber of a specific known moisture content that is kept in a
controlled environment.

In the case of a boat, that is not easily accomplished. In fact is
impossible. You don't have a standard upon which to calibrate the
meter. Bottom line, the actual NUMBER read is completely meaningless. I
repeat, it is MEANINGLESS.


~~ snippage happens ~~

The fact is that you can't calibrate a meter if you don't know were
zero is. I can only conceive of one way that a meter measure would be
invalid and that is if zero wasn't zero - as in your illustration.
Why somebody would use a meter that wasn't zero is beyond me.

Your wood sampling example is not calibration, but comparative
measurement. You have a zero meter, you measure the standard, then
measure the test piece and make the evaluation. You just can't walk
up to the standard and test it without having a baseline - which is
zero.

For straight measurement, it is most certainly accurate and it's done
all the time to determine set times for aggregate mixes, core moisture
in building roofs, materials density and many other types of
structural conditions. You walk in with a zero meter, take your
measurement and make your recommendation. What you are measuring, by
what ever method from doppler to resistance, zero has to be zero for
any measurement to be valid.

It is most certainly not meaningless.

Later,

Tom

Tom

You're confused. I'll try my best to help but you can believe whatever
you want in the end. I have a feeling I am wasting my time but I'll
try...JUST ONCE in good faith.

Moisture meters that are non-invasive do not measure moisture, they
measure DENSITY. THAT fact is the most important thing you need to
understand in respect to moisture meters.

They use a form of echo sounding that gives a general indication of
density. Two small (often coin sized) disks on the meter. One sends, one
receives. If you think otherwise, please provide a scientific
explanation as to how those two coins can measure "moisture". Fact is,
they can't.

Different materials are different densities. The only thing you can
measure is the density of a specific material and the only thing that
gives you is it's density relative to another substance or location.

Setting a density meter to zero (presumably by holding it up in the
air?) doen't calibrate it. In fact, moisture meters always read close to
zero when held in the air, even if you fiddle with the calibration knob.
Try it yourself sometime.

In fact, if ZERO is the only thing that matters, why even put a
calibration knob on the meter? Why not just calibrate it to zero at the
factory and leave it that way? Think about that.

Setting it to zero by applying it to the hull sets it to zero in
reference to the hull density. Hence, further measurements measure the
density of the hull relative to the location where you set it to zero.

I hope you'll take the time to reflect upon this in a logical manner.
If not, well... at least I tried. Last post on the subject from me though.

Geri izmack wrote:

I knew I'd be opening a can o' worms!

The Tramex reading he go on the cockpit was virtually zero, to give an idea
of calibration. The foredeck was a spotty 60-100, but Trojans have always
been weak in this area. All soundings were good (including the hull),
except for two small foredeck spots w/ compromised soundings.



The foredeck may be cored, while the hull may be (and should be) solid
below the water line.

Therefore a comparison between the two is fairly meaningless since they
both differ in density.

In other words zero on the deck and higher in the hull means nothing
more than...the hull is more dense than the deck. And that is normally
the case.

Just think about a moisture meter as what it REALLY is... a density
meter. Just doing that one thing will allow you to apply logic and
reason to the results that they give.

I'm afraid I don't have time to debate the matter with those who are
uniformed but stubborn.

Hope this info helps!

Best of luck
M

P.S. - if you are wondering why I know htis it's because I am an
engineer and designed non-invasive "moisure meters" for a living some
years ago.

On Sun, 20 Mar 2005 16:52:00 -0500, Marley wrote:

Short Wave Sportfishing wrote:

On Sun, 20 Mar 2005 15:36:54 -0500, Marley wrote:


Izmack wrote:

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?


You need to better understand moisture meters and readings.

Moisture meters have to be calibrated very carefully.

For example they are used extensively in determining the amount of
moisture in lumber when it is being or has been cut or kiln dried. In
order to make that determination the user first sets the calibration of
the meter against a known standard. In other words, using a piece of
identical lumber of a specific known moisture content that is kept in a
controlled environment.

In the case of a boat, that is not easily accomplished. In fact is
impossible. You don't have a standard upon which to calibrate the
meter. Bottom line, the actual NUMBER read is completely meaningless. I
repeat, it is MEANINGLESS.


~~ snippage happens ~~

The fact is that you can't calibrate a meter if you don't know were
zero is. I can only conceive of one way that a meter measure would be
invalid and that is if zero wasn't zero - as in your illustration.
Why somebody would use a meter that wasn't zero is beyond me.

Your wood sampling example is not calibration, but comparative
measurement. You have a zero meter, you measure the standard, then
measure the test piece and make the evaluation. You just can't walk
up to the standard and test it without having a baseline - which is
zero.

For straight measurement, it is most certainly accurate and it's done
all the time to determine set times for aggregate mixes, core moisture
in building roofs, materials density and many other types of
structural conditions. You walk in with a zero meter, take your
measurement and make your recommendation. What you are measuring, by
what ever method from doppler to resistance, zero has to be zero for
any measurement to be valid.

It is most certainly not meaningless.

I hope you'll take the time to reflect upon this in a logical manner.
If not, well... at least I tried. Last post on the subject from me though.

Obviously you are much smarter than I am and have it figured
perfectly.

But as you seem to have so much more knowledge of the subject than I
do, allow me to ask a couple of questions which I'm unclear on.

1 - What is the meter baseline and how to you set it?

2 - How can you make a content analysis of any material without first
starting at a reference point? If that reference point isn't zero,
then was is it?

3 - If the baseline is not zero, how do you determine what zero is?

I am very interested in your response - I wish to be enlightened.

Later,

Tom

On Sun, 20 Mar 2005 21:34:10 GMT, "Geri"
wrote:

I knew I'd be opening a can o' worms!

The Tramex reading he go on the cockpit was virtually zero, to give an idea
of calibration. The foredeck was a spotty 60-100, but Trojans have always
been weak in this area. All soundings were good (including the hull),
except for two small foredeck spots w/ compromised soundings.

Well, in any case, good luck with it.

And don't worry about the little side track - sometimes it's hard to
get a point across - in particular when you are dealing with somebody
who "designed" something.

Regardless, moisture readings are not meaningless. It's kind of
interesting going through the Tramex site and checking out the meter
specs. It's an education.

The meter I have, by the way, is the Skipper. I kind of inherited it
from somebody who was going out of the survey business. :)

Good luck.

Later,

Tom

"Short Wave Sportfishing" wrote in message
...


2 - How can you make a content analysis of any material without first
starting at a reference point? If that reference point isn't zero,
then was is it?

3 - If the baseline is not zero, how do you determine what zero is?

I am very interested in your response - I wish to be enlightened.

Later,

Tom

Howdy Tom,

I was following this thread with casual interest until I realized that
moisture meter is, as the other poster suggested, really a density meter. I
am curious if it is really a ultrasonic density measuring system. I recall
that they are calibrated using calibration blocks of a material with a know
and certified density.

Eisboch

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 Sun, 20 Mar 2005 19:01:50 -0500, "Eisboch"
wrote:


"Short Wave Sportfishing" wrote in message
.. .


2 - How can you make a content analysis of any material without first
starting at a reference point? If that reference point isn't zero,
then was is it?

3 - If the baseline is not zero, how do you determine what zero is?

I am very interested in your response - I wish to be enlightened.

Later,

Tom

Howdy Tom,

I was following this thread with casual interest until I realized that
moisture meter is, as the other poster suggested, really a density meter. I
am curious if it is really a ultrasonic density measuring system. I recall
that they are calibrated using calibration blocks of a material with a know
and certified density.

Howdy Sir - how's the weather?

It depends on your definition of density. Using a standard definition
of density like the mass per unit volume of a substance under
specified conditions of pressure and temperature, then no, a moisture
can't measure density in that sense.

You measure density by specific gravity - that is weighing the
material in question or determining it's relative hardness (density)
by deforming the surface or the shape of the material in some manner
and measuring the force needed to do so. Then applying some
mathematics, you have density.

As I understand it, and have demonstrated to myself by playing with
the one I have, moisture meters measure resistance. They do this by
using a 1 KHz modulated signal anywhere from 5 to 40 KHz in frequency
across a predetermined distance (centers of the probes or pads).

The presence of water would necessarily mean that there was lower
resistance, but it doesn't mean that the material is less dense.
We're not dealing with a solid block of something - this is woven and
porous fiber. The density of the fiberglass and resins isn't the
issue - it's the water in, through and surrounding the fibers and it's
penetration through the resins.

Think of it this way. If you fill a ceramic bowl with water and put
the meter pads in it, what are you measuring? The amount of water in
the bowl or the density of the bowl?

Yes/No?

Later,

Tom