Use of a wood moisture meter

[Howard Rice]

Can a wood moisture meter be used on a plywood hull flow coated in WEST epoxy? Or put another way will the meter detect moisture accurately through epoxy?
Thanks.
Howard

[Jim Ledger]

A moisture meter has two pins that need to penetrate the wood in order to obtain a reading, the deeper the better. A reading can be taken off epoxy coated wood, but the pins must be able to penetrate the coating and holes will be left in the surface.


You want to talk to Bob Smalser about moisture meters. Maybe he'll come out of the woodwork.

[john welsford]

The answer is yes, but those pins have to be driven in well. Plywood though is interesting stuff in that the glue film between the veneers impedes transmission of moisture to some degree so in the case of West sealed plywood there is not only a barrier on the surface, but a series of barriers as you go through the thickness of the plywood.
Most moisture meters need a reasonable amount of the probes in contact with the wood, and if you drive the probes well into plywood what you will get is a reading that sort of averages the varying readings through the layers.
But if you were to push them in 6mm or so and get a reading of 20% you'd know that you are in trouble, and below 10% you're ok.
I'm ok with any reading below about 14%
Note that most moisture meters are somewhat inaccurate, they are a quick test only and the best is to take a sample to the lab and do a weight and cook comparison test in controlled humidity.

John Welsford

[Dale Genther]

I have a moisture meter that uses some technology other than the pins that have to penetrate into the wood. You just set the flat bottom of the unit against whatever you want to test and push the button. It then reads the % moisture on a series of LEDS. The unit comes with a table to correct for various wood species. However it works it will read into the wood a certain distance, thus you can use it on wood that has been coated with epoxy or a thin layer of glass. I'm not certain that the percentage readout is exactly accurate but it is very good at giving relative readings. I.E. if you read 12% at someplace you know is OK and over 20% someplace else, you probably have a problem. I forget who makes it , but I'm pleased with it.

[Ron Williamson]

I have a pinless one that works on plywood and fiberglass,but Dale's right,it's really only good for relative readings.
The other thing,and this is big,it's meant for thick material.
If you are checking something that's 1/2",it will also be reading the air, hardware or bulkhead beneath the sensor.
It's also fooled by changes in density,like from heartwood to sapwood or around knots, as well as the difference between flat sawn and quarter sawn.
R

[Mike Vogdes]

I have a pinless unit as well, made by Tremex (sp), I use it to check plywood transoms among other things and seem to work fine on plywood.

[cookie]

......


You want to talk to Bob Smalser about moisture meters. Maybe he'll come out of the woodwork.

Haven't seen much of Bob Smalser since he was flamed by Terry L and PCFord on that bung discussion. I sure hope he has not decided to leave the forum because of that. :(

As for moisture meters, I have seen them for 25 bucks, 90 bucks and a whopping 400$. All of them came with pins. The 25 one was sold a a specialty woodworking store. Could it be any good at that price?

[cookie]

Here is a pic.
http://www.baptist.nl/sitemanager/images/shopimages/prod1_5000.jpg
The description says it reads between 8 and 20%. No info about the accuracy though.

[Ron Williamson]

Yes.
It's just an ohmmeter testing resistance.
But you need to test it against a known,like pine that's been in the shed for ten years vs.pine fresh of the saw.
R

[Howard Rice]

Great info folks. Thank you all.
I would be checking two layers of ply, flow coated each side, bonded with epoxy in between and then then both surfaces (finished half inch flow coated with epoxy as the final encapsulation. Hmmm sounds like I better just keep an eye open for anything odd. Perhaps a thorough tapping test for sound differences might be a good start.
Thoughts anyone?
I am being paranoid, so far so good on this boat with zero problems. An ounce of prevention...........all against the context of how I sail her. I go far offshore as often as possible. Attention to all details, under water, above water, on deck and aloft has kept my hair dry all these years on all boats I sail. The one in question I have been sailing for a mere two years.
Howard

[Mike Vogdes]

[QUOTE=Howard Rice;2324636]Great info folks. Thank you all.
I would be checking two layers of ply, flow coated each side, bonded with epoxy in between and then then both surfaces (finished half inch flow coated with epoxy as the final encapsulation.

Are you saying half inch thick final flow coat?

[Howard Rice]

Hi Mike
My understanding is the finished hull thickness is 1/2" and is encapsulated in epoxy therefore giving a slightly thicker final dimension (1/2" plus epoxy coating both sides).
Thanks
Howard

[keystone17]

So I posted a while back recommending the use of a moisture meter and now, coincidentally, I have my own question about their use. I am working on a huge scale project and I need to find a meter. I did find a place that has a moisture detector (http://www.wagnermeters.com) but I would like a review if anyone has used it, and also I would like to know how to use it! Also, does a detector work the same way as a meter? Thank you for any reply!

[Bruce Hooke]

keystone17, welcome to the forum (since you have only posted twice I am guessing you are new around here)! Your question is likely to get lost here as many people will read the question at the top of the thread and answer that and not even realize that the original question is quite old and that someone dropped in a new question way down on the thread. You really are better off starting a new thread.

-Bruce

[Mrleft8]

I like the Delmhorst meters with the analog scale. For anything thicker than 1-1 1/2" I use the remote probe with the "autobody dent puller" handle, and teflon coated pins.
I just don't trust the pinless meters. and the digital ones are pretty... What's the word.... Broad scoped? They give you a reading with something like 4 degrees of accuracy. 4 degrees is the difference between "It's been a wet summer", and "You have a leak somewhere"...
But I'm old school. I still have a gerbil on an exercise wheel to power the computer.

[Bob Smalser]

I am working on a huge scale project and I need to find a meter. I did find a place that has a moisture detector (http://www.wagnermeters.com) but I would like a review if anyone has used it, and also I would like to know how to use it! Also, does a detector work the same way as a meter? Thank you for any reply!

Perhaps it's better to state exactly what your project is and what you hope to do with a moisture meter. Merely double-checking previously-kilned lumber before using it is an entirely different requirement than drying green lumber on your own, and require different meters.

The best first step is to read up on the three basic types of meter so you insure you ask the right questions:

http://www.delmhorst.com/popups/wood_faq.html

http://www.delmhorst.com/images/indust_faq/page6.gif