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.