Moisture content in marine grade ply

[Karol]

Just yesterday I got my hands on a moisture meter, and out of curiosity I measured the moisture content of the wood I'm using in my stich-n-glue boat. I was surprised to find that my marine grade ply (stamped BS 1088, i see a lot of discussion about BS1088 on the forum...)was anywhere between 14% to almost 20%. All the solid wood that was used in construction is between 8 to 12. I thought that it might be because the wood i standing outside (but covered), but even the plywood that is stored in the garage is also 14% to 20%. Should it be that high? I'm using epoxy glue, and I hope it will not cause any problems. Anyone knows the reason or has similar experience?
Thanks

[Ron Williamson]

Karol
Moisture meters lie.
Did you also get your hands on the manual?
Did you correct for the species density?Most read red oak accurately.
Did you correct for the temperature?Most will read accurately at 70F
If it is a pinless meter,it may be reading the MC of whatever is underneath or the conductivity(?) of the glue.
These differences can be a couple of percent each.
How long has the material been sitting around?Dry wood will pick up moisture from the atmosphere until it is at equilibrium.
This time of year the equilibrium relative humidity (and therefore moisture content)can be quite high.
Since the difference in MC are consistent inside the building vs.outside and the solid wood is between 8 and 12% inside the building,I would say that the density difference is the culprit.
Have fun
R

[This message has been edited by Ron Williamson (edited 10-03-2001).]

[Paul Brooks]

Yes, I bought a moisture meter before epoxy coating the inside. (Last Winter was very wet here and I thought the cedar would have taken up quite a lot of moisture, even thought the garage is watertight. I got the same result as you though. The cedar was bone dry, the ply had quite a high % (from memory the 14%-20% sounds about the same as I measured). I didn't know about correcting for density and just assumed ply was "different". I did heat the garage for 24 hours but it didn't make any difference to the moisture content, so I went ahead anyway, with CPES as a primer and then epoxy - no problems and very good adhesion. If you can afford it, I'd recommend the CPES though.
Good Luck
Paul

[Ed Harrow]

Or, as one of my coworkers says, "People tend to rely too much on answers that come out of computers."