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Author Topic: 12 inch wide oak  (Read 3392 times)

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Offline YellowHammer

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Re: 12 inch wide oak
« Reply #20 on: May 03, 2018, 10:43:07 PM »
All that, or...... put it in a solar kiln and wait it out.  

When the board is ripped down the neutral axis it will in effect be a full size prong test, and could end up like this.

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Offline GeneWengert-WoodDoc

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Re: 12 inch wide oak
« Reply #21 on: May 04, 2018, 04:35:17 PM »
If you set in out for air drying in January, around 6 months to get under 25%MC, depending on the weather.  Set in in April and then maybe 90 days.  

Actually, if air dried to 25% MC, there will minimal casehardening stress as the high humidity every morning will remove the stress.  Also appreciate that when most pieces are 25% MC, there will be a few drier and a few wetter pieces.

As the outer shell of the wood will be accustomed to an air drying condition of 12% to 13% EMC, if you put it into the kiln at 95% RH (which is very difficult to obtain and hold as it is just 1 degree F away from condensation and even at 95% RH mold grows well), the surface will swell and drive any existing checks deeper.  Plus, at 95% RH, the EMC is around 25% EMC, so there will be no drying.  Further, it is difficult to accurately measure 95% RH with conventional kiln controls.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline scsmith42

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Re: 12 inch wide oak
« Reply #22 on: May 04, 2018, 05:19:24 PM »
If you set in out for air drying in January, easily 6 months to get under 25%MC.  Set in in April and then maybe 90 days.  

Actually, if air dried to
Gene, 6 months to air dry 7/4 white oak from green to below 25%?
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Offline scsmith42

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Re: 12 inch wide oak
« Reply #23 on: May 04, 2018, 05:21:45 PM »
I could air dry them for awhile (6 months?) before putting them in the kiln(I don't have one... but I know a guy).  Any tips on kiln settings for this.  It's a Nyle/woodmizer kiln. . .
. . . . the boards will be around 45% MC, give or take.  If you then load into the Woodmizer kiln you will need to have a system for adding moisture back into the kiln (I use a high pressure fogging system in mine).  You'll need to keep the RH% up around 95%, give or take, for about 60 days at 90F.
8/4 white oak is around a 4 month kiln run in an L200, and that's with a fogging system. . .
The biggest challenge with all of this is getting the thick boards the same MC% in the core and the shell.  If it varies, they will cup after resawing. . . .

So, if I've got this right, 2 months of 95% RH and another 2 months of a 'normal' white oak drying cycle after that? . . . and speciality fogging systems in the kiln?
All to get uniform dryness from core to surface?
Seems like a lot of fussing around.
Suggestion, once you have your lumber milled, air dry for a much longer time (Brad, you said 6 months?).
Stack, sticker and strap with loading straps. As the stack shrinks, ratchet up the strap tension to keep the lumber under pressure and straight.
Air dry as if you were aging whiskey in the cask, until the core and surface have equal MC's.
Then run the kiln cycle to take down the bound moisture in the wood.
Would this work ?
Your method would work if Brad had the time.  Gene doesn't think that the 95% RH would be required after 6 months of air drying so just a couple of months of "normal" WO schedule after that.
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Offline GeneWengert-WoodDoc

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Re: 12 inch wide oak
« Reply #24 on: May 05, 2018, 07:29:50 AM »
I just noticed the message I posted was cut short.  Here is the missing part


Actually, if air dried to 25% MC, there will minimal casehardening stress as the high humidity every morning will remove the stress.  Also appreciate that when most pieces are 25% MC, there will be a few drier and a few wetter pieces.

As the outer shell of the wood will be accustomed to an air drying condition of 12% to 13% EMC, if you put it into the kiln at 95% RH (which is very difficult to obtain and hold as it is just 1 degree F away from condensation and even at 95% RH mold grows well), the surface will swell and drive any existing checks deeper.  Plus, at 95% RH, the EMC is around 25% EMC, so there will be no drying.  Further, it is difficult to accurately measure 95% RH with conventional kiln controls.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline Brad_bb

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Re: 12 inch wide oak
« Reply #25 on: May 05, 2018, 08:46:38 AM »
 Iím doing my best to keep up with this discussion and not get lost. I am not necessarily limited to six months. Would the ideal thing to do be to let it air dry longer?  Are we trying to get to a certain moisture percentage I i.e. 25%?  Is that what I want before going to the kiln?  This will be for the stairwell of my new shop.
Anything someone can design, I can sure figure out how to fix!
If I say it\\\\\\\'s going to take so long, multiply that by at least 3!

Offline GeneWengert-WoodDoc

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Re: 12 inch wide oak
« Reply #26 on: May 05, 2018, 09:59:51 PM »
It is a trade off between the time and costs to air drying (under a roof) to a lower MC (as the outside air is 12 to 13% EMC and with thicker stock, you probably can air dry in year to 18% MC) versus the time and cost in the kiln.  As a rough idea, you will lose about 0.4% MC per day in the kiln.  So, if the wettest  lumber in the kiln is 26% MC versus 22% MC, the drying time will be 10 days longer.  A day in the kiln is around $20 per day per 1000 bf, including profit.  On the other hand, air drying is not free.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline Brad_bb

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Re: 12 inch wide oak
« Reply #27 on: May 06, 2018, 09:45:16 AM »
Gene, the guy close to me here wanted $1/BF for ash that was in the kiln 4 weeks.  I actually don't know if he's done oak.  I seem to remember him saying something about not wanting to do oak.  Maybe he tried once and had a bad experience? Wrong parameters maybe?  That's why I'm trying to get the details for drying to advise him.
Anything someone can design, I can sure figure out how to fix!
If I say it\\\\\\\'s going to take so long, multiply that by at least 3!

Offline Brad_bb

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Re: 12 inch wide oak
« Reply #28 on: July 10, 2018, 09:50:38 AM »
Scsmith42 and GeneWengert-WoodDoc,
I've been re-reading this post again.  Couple questions.
1. What would be the most preferable way to dry the 1.75 thick pieces?  Would it be a long air dry?  To dry undercover, I have two options - in a Morton building that gets about 10 degrees warmer than outside in the summer, or in an air conditioned shop.  I'm worried about case hardening -having tension in the shell.  Would either of these cause that?  I'm thinking the low humidity of the AC shop would dry too fast.  
2. Gene you mentioned humidity in the morning when drying from Jan-June.  I'm in IL, and worried my conditions would be different - colder longer with not enough humidity until June.  This June was very hot and humid, but before was not.

Given the kiln requirements mentioned, I don't know where I'd find a kiln that will really know how to handle the oak/kiln settings.  This job will use about 1400 Board feet.  I'm not sure who'd want to dry this for the long times Scott mentioned?  4 months?  6 months? Is it preferable to air dry for longer?  Given my location, is there a better time of year to cut and start drying?
Anything someone can design, I can sure figure out how to fix!
If I say it\\\\\\\'s going to take so long, multiply that by at least 3!

Offline GeneWengert-WoodDoc

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Re: 12 inch wide oak
« Reply #29 on: July 10, 2018, 10:31:18 PM »
The preferable drying technique would be air drying in an open shed- -roof but fairly open walls.  For thicker oak we might use burlap to slow air flow if the building is too open.  Does your building have a large door so you could put the lumber in the building near the open door so you would get some, but not too much, air flow?  You would also get no rain or sun, which is good.  We would not want the door open for times when the RH is much under 60% RH for the first month.  Air speed and RH work together.  An I-phone weather app gives current RH for its location.  I would watch closely for any afternoon checking (checks close when the RH increases evenings and mornings) and would expect 100 days minimum drying time to achieve around 22% MC. 

Casehardening is removed every night when the outside approaches 100% RH.

Kiln drying time would be around 30 days.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline YellowHammer

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Re: 12 inch wide oak
« Reply #30 on: July 11, 2018, 08:22:59 AM »
1.75 thick oak pieces can be dried successfully with controlled air drying, especially in the summer.  Typically, I place these types of stacks in the center of my air drying area shed, covered, out of the wind, with locally higher MC stacks surrounding it.  As they start to dry out, I rotate them more to the outside.

Winter is best, but it can be done other times with care.

My typical process for this thickness of oak is careful air drying, then overloaded into a solar kiln, then finished and sterilized in the Nyle.  Works fine this way.  

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Offline scsmith42

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Re: 12 inch wide oak
« Reply #31 on: July 11, 2018, 08:43:06 AM »
My typical process for this thickness of oak is careful air drying, then overloaded into a solar kiln, then finished and sterilized in the Nyle.  Works fine this way.  
This is how I do it as well.  ďOverloadingĒ the solar kiln reduces the drying rate.  
Geneís original guidance to me on collector size when I built my solar kilns was to maintain a 1:10 ratio in collector size for 4/4 oak; ie 100 square feet of collector for 1000 board feet of 4/4 oak.  
When I dry 8/4 oak, Iíll block off 60% of the collector initially or increase the load size by a similar amount at the start of the solar drying process in order to reduce the drying rate.
As the wood dries down Iíll gradually remove some of the collector blocking until Iím back at 1:10.
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Offline Brad_bb

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Re: 12 inch wide oak
« Reply #32 on: July 11, 2018, 05:15:54 PM »
Out of Curiosity, how do you block the collector?

So If we are interested in slowing down the drying initially, wouldn't my Morton shed be good for that?  There would be very little airflow.  The temp wouldn't be as much as a solar kiln, but 8-10 degrees or so above the outside temp.  There is some air exchange I'm sure with the cracks/openings in the sliding doors.  You can sometimes tell when you go to shut the walk in door there's a slight pressure.  

I don't have a solar kiln.  I'm seriously considering building one or three.
Anything someone can design, I can sure figure out how to fix!
If I say it\\\\\\\'s going to take so long, multiply that by at least 3!

Offline 1938farmall

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Re: 12 inch wide oak
« Reply #33 on: July 11, 2018, 06:52:31 PM »
Sounds like you might also be ready to build a machine to put circle saw scratch marks on your resawn boards :)
aka oldnorskie

Offline YellowHammer

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Re: 12 inch wide oak
« Reply #34 on: July 11, 2018, 11:03:24 PM »
Any structure can be used as a kiln or controlled drying area as long as it has the characteristics of a proper drying area for that particular wood species, thickness, and current moisture content.  It should have the correct airflow velocity for the species being dried, proper air venting to maintain proper WB and DB levels, proper flooring and proper temperature control.

For most red oak the maximum general safe moisture removal rate is about 3.5% per day, and for white oak, itís about 2.5% per day for 4/4 wood.  I generally divide those numbers by the multiple of the thickness so 1.75 inch thick red oak can tolerate about 2% per day, max, and white oak about 1.4% per day.  Also, for oak I like to have no more than 150 feet per minute airflow through the stacks.  So any box, shipping container, garage, shed, etc that can meet these properties will work.

Green oak will give up its moisture readily, in fact too readily, and will blow through these max allowable moisture removal rates pretty easily, even when air drying, or if left uncontrolled in an enclosed space.

So with thick green oak, itís about slow drying and control.    
 
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Offline GeneWengert-WoodDoc

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Re: 12 inch wide oak
« Reply #35 on: July 12, 2018, 12:19:10 AM »
We do need air flow, proper RH and some warmth.  To achieve the proper air flow is difficult in a building without fans, so putting the lumber near an open door will help.  Also, as the water is evaporated into the building, the RH will rise, so you need some venting to the outside.  With thick oak, we do not like any temperatures over 100 F.  So, all three environmental variables need to be correct and they work together.  To help us, we monitor the daily drying rate of the wood.
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Offline scsmith42

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Re: 12 inch wide oak
« Reply #36 on: July 12, 2018, 04:15:26 PM »
Out of Curiosity, how do you block the collector?

So If we are interested in slowing down the drying initially, wouldn't my Morton shed be good for that?  There would be very little airflow. 


Brad, I block part of the collector with either a tarp or a piece of landscape fabric.
Airflow is important to drying and prevention of mold growth.  Even if you put them in your Morton shed you would need some air exchange (to get rid of the humidity) and some gentle airflow across the stacks.
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Offline Kindlinmaker

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Re: 12 inch wide oak
« Reply #37 on: July 16, 2018, 11:47:25 PM »
Flat sawn may not make it to the resaw without a fair amount of damage. We needed a few oak boards and didnít have any in our stash.  Grabbed a 28Ē x 6í white oak log off the firewood log stack that we knew had flaws in it. Flat sawn at 5/4 and then retrimmed sides into a few boards. Stacked the balance of the flat sawn slabs on a pallet by the mill. 2 weeks later I notice a couple of the slabs look decent for boards but cracks had already started in the center ends. Grabbed a couple and ripped down the center to save if possible. Those boards had a good 1Ē bow after center rip. No doubt they would have self destructed if stickered and air dried as slaps. I have a major slab experiment in my basement. 10/4 of various species air drying for the last year with stickers and weight. Red oak is actual behaving better than white oak, sugar maple, silver maple and cherry.  Most have some degree of center splits and the cupping on slabs near the pith of some (especially cherry) is lifting hundreds of pounds of slabs and weight stacked on top.  Slabs are a trick; I may never figure them out but I sure am learning as I try. (And living up to my name making lots of kindlin). 


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