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Old 05-28-2011, 09:54 AM
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Default how to use a moisture meter

I am a newbie here and considering buying an older boat.
I have read some threads on avoiding the nightmare of rot in stringers and transom.
I see recommendations on using a moisture meter.
My questions are:
Which moisture meter exactly, are the cheaper ones adequate?
Do they read through fiberglass or do you need to remove a screw or otherwise access the transom and stringers to get an accurate reading?
How is the reading expressed ( %) and what is the significance?
Thanks for your opinions and comments.
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Old 05-28-2011, 10:10 AM
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stick the probe into the wood your testing and read the meter...won't read through fiberglass
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Old 05-28-2011, 10:15 AM
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Most moisture meters are surface reading, which means you lay it against the surface you want to read, and it will give you the moisture content, in either percentage on an lcd/led screen, or in a colored bar. They usually have probes, which allow you to poke in the material, and get a reading that way as well, but poking two holes in the boat isn't what you want to do.

Some are better then others, of course. I use a GE Protimeter, which has both, and is very accurate. I have also used older units, which would be similar to today's 'cheaper' units. They are ok, but typically can't read if the surface is wet, and may not have a surface read (probe only).

When you get one, familiarize yourself with it. Always try and get a baseline for the material you are trying to read, ie., a known dry area, so you can get it's 'dry' moisture level, and can properly assess from there.

Anyway, they're worth owning.
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Old 05-28-2011, 10:16 AM
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Quote:
Originally Posted by bridgeman View Post
stick the probe into the wood your testing and read the meter...won't read through fiberglass
Yes, some will. My protimeter will, as long as there are no voids, a good one will read through it.
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Old 05-28-2011, 10:29 AM
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Lignomat is the best, buy from Amazon. Assembled in Portland OR with componenbts made in Germany.

Mine has two probes about 1/4" long, push into the wood and read the digital. Comes with a page of calibration numbers for different woods. Another model has a slide hammer with two probes about 1 inch long, I would buy this model for testing wood in boats. You can drill two small holes in the fiberglass to match the probe spacing, stick the probs in with a rap from the slide hammer and take a reading.

Not cheap, but accurate. www.lignomat.com

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Last edited by Altamaha; 05-28-2011 at 10:59 AM.
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Old 05-28-2011, 10:31 AM
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Thanks for the quick and knowledgeable replies.

I see the GE protimeters on amazon.com. Some of them indicate they will give a deep reading non invasively. They are a little pricey though. I wonder if you could rent one from an equipment rental business.

The Lingomat is less expensive, and looks accurate. But I am not sure about the owner allowing me to drill small holes to test their boat.
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Old 05-28-2011, 10:35 AM
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You can hire a surveyor for the price of a good meter.
I use an Electrophysics GRP33 pin-less as the go-to and double down with the Tramex pin type when needed.
The GRP33 will read the holding tank against the hull side or moisture in a heavy wax build up. Gotta know what you are doing.
They don't call them deal killers for nothing.
Experiance is key, trust your hammer, these meters will lie or mislead you if you are not careful and well versed in their particular ways.
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Old 05-28-2011, 11:11 AM
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Quote:
Originally Posted by baitkiller View Post
You can hire a surveyor for the price of a good meter.
I use an Electrophysics GRP33 pin-less as the go-to and double down with the Tramex pin type when needed.
The GRP33 will read the holding tank against the hull side or moisture in a heavy wax build up. Gotta know what you are doing.
They don't call them deal killers for nothing.
Experiance is key, trust your hammer, these meters will lie or mislead you if you are not careful and well versed in their particular ways.
I would depend on an experienced surveyor also. He knows what to look for and where to look.

My experience with older boats, especially if they are stored outside, is they have floor rot or stringer rot or transom rot or some combination of all. Just gotta know how to find it!

Deal killer is correct, a guy that knows how to use a moisture meter is worth his price.

My old laminating buddy used a silver dollar and was real good in finding delamination. His backup was a 6 oz ball peen hammer. Water soaked wood behind fiberglass has a different sound and bounce, the hammer tells all.

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Old 05-28-2011, 12:21 PM
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I also use the Electrophysics GRP33 pinless moisture meter in all of my surveys on fiberglass and wood boats. You can also self calibrate these units to insure they are adjusted properly. I also have a pin type digital moisture meter for wood boats or if a section of the stringers or interior fiberglass are painted with anti-fouling paint (yes I get that from time to time). I try to keep all of my testing as non-instrusive as possible. But also sounding the stringers with a phenolic hammer and just plain sight will give an indication that something is wrong. Excess rot in the stringers is a deal breaker unless you are willing to bear the expense of repairing it. As a sailor if I have any doubt in the intergrity of the hull, I would not even chance taking the vessel underway.
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Old 05-28-2011, 05:51 PM
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A reliable pinless moisture meter suitable for inspection of fiberglass hulls will cost $300 to $500. There are cheaper devices, but erroneous information is probably worse than no information. I sold my moisture meter after inspecting a lot of boats taught me that the meter typically only confirmed what was easily detectable by visual and physical inspection. If you're only looking at a few boats, it might be less expensive to hire a surveyor. The hull on an older boat is only part of the picture. The power plant is probably more important and potentially more expensive, and a moisture meter can't help you there.
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Old 05-29-2011, 11:19 AM
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Many surveyors will not stand behind meter results.

http://www.yachtsurvey.com/moisture_meters.htm
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Old 05-30-2011, 07:00 PM
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Another handy tool is an Infrared camera.

If the boat is in a yard w/ appropriate temperature changes, then an IR camera could get decent images showing water. Water will track temperature changes more slowly than dry.

A picture will save a kiloword.
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Old 05-30-2011, 08:51 PM
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Quote:
Originally Posted by wingless View Post
Another handy tool is an Infrared camera.

If the boat is in a yard w/ appropriate temperature changes, then an IR camera could get decent images showing water. Water will track temperature changes more slowly than dry.

A picture will save a kiloword.
True, but for the price of a good IR, might as well just buy 2 boats.
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