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Forum topic by gfadvm posted 04-03-2014 01:58 AM 1027 views 0 times favorited 25 replies Add to Favorites Watch
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gfadvm

11543 posts in 1442 days


04-03-2014 01:58 AM

Topic tags/keywords: air drying lumber

I recently posted a question on the Forestry Forum that may be of interest to LJs:

How dry can I expect properly stacked and stickered sawmilled lumber to get in NE Oklahoma? (indoors in an unheated,well ventilated building) The answers I got indicated that 15% is all I can expect.

I would have been waiting forever for it to get to 8-10%!

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm


25 replies so far

View Monte Pittman's profile (online now)

Monte Pittman

15508 posts in 1090 days


#1 posted 04-03-2014 02:02 AM

In theory, it shouldn’t go below your normal humidity level. Mine can get to 8%-10%.

-- Mother Nature created it, I just assemble it.

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pintodeluxe

3570 posts in 1566 days


#2 posted 04-03-2014 02:04 AM

Yes, it takes a kiln or a very dry climate to get lumber below 10% m.c.
However lumber that is air dried to 15%, and then kiln dried is very stable. It is not as prone to warping and checking as green lumber that goes straight in the kiln.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View Monte Pittman's profile (online now)

Monte Pittman

15508 posts in 1090 days


#3 posted 04-03-2014 02:07 AM

We could turn that back room in your storage building into a kiln!

-- Mother Nature created it, I just assemble it.

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firefighterontheside

5895 posts in 609 days


#4 posted 04-03-2014 02:24 AM

This calculator tells you what the theoretical equilibrium moisture content would be at a given temperature and RH. Trying it out a few times it looks like it gives lower values than you have been told, but this calculator assumes constant conditions. Obviously in reality the conditions will change constantly and the average over the accepted one year of drying for one inch of wood will be quite low.
http://www.csgnetwork.com/emctablecalc.html

-- Bill M. I love my job as a firefighter, but nothing gives me the satisfaction of running my hand over a project that I have built and just finished sanding.

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gfadvm

11543 posts in 1442 days


#5 posted 04-03-2014 02:25 AM

According to the FF guys our average daily humidity here is 60%. Odd that wood will dry to 15% but I’m glad!

Monte, Nah, that’s where the new planer is going!

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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firefighterontheside

5895 posts in 609 days


#6 posted 04-03-2014 02:34 AM

Wood moisture content is a comparison of the woods actual weight to its oven dry weight, whereas RH is a measure of the amount of water in air at a given temperature compared to what it could hold at that temperature. Similar methods, but the numbers don’t compare.

-- Bill M. I love my job as a firefighter, but nothing gives me the satisfaction of running my hand over a project that I have built and just finished sanding.

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Blackie_

3667 posts in 1265 days


#7 posted 04-03-2014 04:03 AM

Andy 15% is all I’ve seen down here in TX as well, that’s even on trees that have been dead for years, it’s been worked fine for me so far.

-- Randy - If I'm not on LJ's then I'm making Saw Dust. Please feel free to visit my store location at http://www.facebook.com/randy.blackstock.custom.wood.designs

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Wildwood

1245 posts in 887 days


#8 posted 04-03-2014 10:35 AM

Drying wood is a water removal process we all know moisture leaves wood through evaporation. Have you thought about using fan or fans to increase air circulation to help bring down MC?

Would think if brought some boards into your shop and let it hang out for a few months before use will also bring down MC.

-- Bill

View WDHLT15's profile

WDHLT15

1215 posts in 1228 days


#9 posted 04-03-2014 11:43 AM

I have air dried tens of thousands of BF of hardwood. Once it gets air dry, and if I bring it into my unheated and uncooled (no climate control) shop, it will lose a % or two from the air dried moisture content. If the shop was climate controlled, the change would more likely be in the 5 – 6% moisture drop from the air dried state.

Humidity limits how dry wood can get because at some point with the given amount of water in the air with a given humidity, the air cannot hold more moisture at that given temperature, and there will be no additional evaporation of water from the wood. Lower the humidity from that point, and the air can hold more water, so evaporation of water from the wood will resume. Increase the humidity, which means more water vapor in the air, and the wood will increase in moisture content as it picks up moisture from the air.

Because the ambient humidity changes over the course of the seasons, wood will gain and lose some moisture as the humidity changes. This results in wood movement as the wood will shrink or swell a bit as it moves to equilibrium with the humidity. Being a good woodworker means understanding, planning for, and managing this seasonal wood movement.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT15 Sawmill. Nyle L53 Dehumidification Kiln. hamsleyhardwood.com

View Broglea's profile

Broglea

669 posts in 1843 days


#10 posted 04-03-2014 12:16 PM

Good topic.

Why worry about reaching 8% MC? If I build a dresser with wood that is 8%, won’t after a number of years of sitting in a house (Non climate controlled) the wood in the dresser increase MC to 12%-15%?

Why not just air dry it to 15% to begin with?

View gfadvm's profile

gfadvm

11543 posts in 1442 days


#11 posted 04-03-2014 01:36 PM

Wildwood, I neglected to mention that I have a fan running in this building 24/7 with open gable vents.

Danny, Thanks for weighing in. Your input is always appreciated as I’m pretty new at this sawmill thing! But I am having way too much fun!

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View Bluepine38's profile

Bluepine38

2954 posts in 1837 days


#12 posted 04-03-2014 03:20 PM

I looked at the weather for Jenks, OK and it indicates average temps of 93 degrees in July and August. If
you used a solar kiln or just a building with an exhaust fan, I am sure the moisture content would get way
down for two months, of course it would just go back up the rest of the year. Sorry, just could not resist
because I know how dry the wood gets in my shop in heat of the summer.

-- As ever, Gus-the 76 yr young apprentice carpenter

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gfadvm

11543 posts in 1442 days


#13 posted 04-03-2014 07:34 PM

Bluepine, I’m interested to see what it does this summer as it does get hot but the humidity is often 80% during that time. We’ll see…....

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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AandCstyle

1485 posts in 1009 days


#14 posted 04-03-2014 11:27 PM

Andy, I am in the NM high desert. I will be happy to store all the wood you care to send me! ;)

-- Art

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gfadvm

11543 posts in 1442 days


#15 posted 04-04-2014 02:16 AM

Art, Come to Tulsa and I’ll load you up with some native Oklahoma lumber. The blackjack is spectacular and I have never seen any for sale.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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