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drying 1/4 sawn white oak

Started by xlogger, February 24, 2018, 05:06:50 AM

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xlogger

I've got a few hundred feet of white oak in kiln now 5/4. I air dried it to around 18% and put in the Nyle. I check it last night showing around 9.5% and still dripping very little. Where would I dry it to before turning up the heat?
Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

WDH

I would go ahead and turn off the compressor and ramp the heat up to 150 degrees and hold for 24 hours.  I would open the doors to check the water in the wet bulb bottle after 12 hours and leave the door open for about 2 minutes.  This will dump water vapor from the kiln.  Then close the doors and run for another 12 hours.  I do this until the wood has been exposed to 150 degrees for a total of 24 hours.  The higher heat will help evaporate that last bit of water which is so tough to get out of white oak.  Opening the doors will dump that vapor, and when you are done with the sterilization cycle, you should be below 9% moisture.  In Georgia, that is good enough for me. 
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

xlogger

Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

scsmith42

Quote from: WDH on February 24, 2018, 07:47:31 AM
I would go ahead and turn off the compressor and ramp the heat up to 150 degrees and hold for 24 hours.  I would open the doors to check the water in the wet bulb bottle after 12 hours and leave the door open for about 2 minutes.  This will dump water vapor from the kiln.  Then close the doors and run for another 12 hours.  I do this until the wood has been exposed to 150 degrees for a total of 24 hours.  The higher heat will help evaporate that last bit of water which is so tough to get out of white oak.  Opening the doors will dump that vapor, and when you are done with the sterilization cycle, you should be below 9% moisture.  In Georgia, that is good enough for me.
Great advice from Danny.
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

Glenn1

Quote from: WDH on February 24, 2018, 07:47:31 AM
I would go ahead and turn off the compressor and ramp the heat up to 150 degrees and hold for 24 hours.  I would open the doors to check the water in the wet bulb bottle after 12 hours and leave the door open for about 2 minutes.  This will dump water vapor from the kiln.  Then close the doors and run for another 12 hours.  I do this until the wood has been exposed to 150 degrees for a total of 24 hours.  The higher heat will help evaporate that last bit of water which is so tough to get out of white oak.  Opening the doors will dump that vapor, and when you are done with the sterilization cycle, you should be below 9% moisture.  In Georgia, that is good enough for me.
Danny,
Since you have turned off the compressor to reach higher temperatures, why would you care about the wet bulb at that time?
Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer

GeneWengert-WoodDoc

Basically, you can turn up the heat whenever you are under 20% MC without risk, if the air drying has been done correctly without damage to the wood.

You monitor the wet-bulb or humidity in order to achieve the low MCs you require.  If the humidity is 65% RH, you cannot dry under 12% MC.  If 50% RH, 9%% MC.  At the same time, using humidities under 30% RH can over dry hardwoods.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

WDH

Glenn,

At the high temp and low humidity, the water bottle can get low, and the wick on the wet bulb probe can start to dry out.  I always add water to the bottle once per day since I don't like to change out a crusty wick.  I could get away with opening the doors and adding water less than I do, or go with a bigger water bottle, but it is now part of my routine, like feeding the dog.  

Another reason, blamed on Yellowhammer.  He told me he likes to open the doors and check things out at least once per day just to monitor what is going on inside, plus you can dump some of the water vapor in the kiln air at the same time when you open the doors.  So, basically, it is his fault :D.    

Another thing.  With my L53, when I get a cup or less of water after 24 hours, the load is dry 100% of the time, you don't even have to put the meter on it, with ONE EXCEPTION.  White oak.  Getting the last bit of water out of that stuff is like pulling hen's teeth (old saying) ;D.  
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

YellowHammer

What a softball, it's killing me not to make a somewhat crude remark about daily hot air kiln dumps.   :D :D

YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

xlogger

Done deal. cut off heat yesterday afternoon, check it by sticking it in sides of boards with my delmhorst J2000 and mostly read a little over 7%. That's the way I check it over 9% putting it in. So it drop around 2% during heat cycle, is that normal?
This is my first time drying ¼ saw oak.
Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

WDH

With white oak, I don't know what normal is unless it is the hair pulling. 
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

YellowHammer

That's typical, a sterilization cycle drop of a percent or maybe two, although as Danny says, white oak usually balks a bit.  Its important to anticipate the drop so it settles where you want it, and doesn't go down too far.  A little Kentucky windage.  

Its also a useful technique if you really need to push a load with high temps at the end, too high for the compressor to operate, because although the air is being dumped, the mass of the wood and kiln is still hot, so the environment will recover very quickly.  Its possible to walk a load down down doing this, compressor off, heat on.  
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

GeneWengert-WoodDoc

Did you make the appropriate temperature corrections?  What temperature did you use, versus the conditions in the kiln?  If the kiln is 150 F for 6 hours or longer, the core will be at that temperature for hours even though the air temperature drops.

Did you drive the pins, when going into the edge of a piece, at a depth of 1/4 of the thickness, or 1/2 the thickness- -the core MC?  The core can lose moisture with heat, but overall the average MC of the piece changes very little.  However, if you have a very low RH, then the shell will lose moisture as well.  This is the idea behind the open door- -it lowers the RH dramatically without running the compressor.  Outside foggy air will drop under 30%RH if heated over 30 F warmer, so with a kiln at 150F that heats outside air maybe 80 F, you will easily get under 10% RH and under 3% EMC.  This dries the shell quickly and core.  Note that the shell of oak machines more poorly anytime you go under 6 % MC, even if you subsequently add some moisture back.  Chipped grain will increase, plus more cup on wider pieces.  So, a short open time is likely better; monitoring TH will make sure you are not too dry from opening the door too long.

Overall, 1/4 oak rakes about 18% longer than flatsawn to dry.

Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

xlogger

I did double check it after out of kiln for a couple days going about 3/4" deep and it read a little over 8°
Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

WDH

Perfect.  Can't do any better than that. 
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

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