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Author Topic: Big Slabs: Sales and handling  (Read 5028 times)

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Offline YellowHammer

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Re: Big Slabs: Sales and handling
« Reply #80 on: July 09, 2017, 11:42:04 pm »
Has anyone put 8/4 white oak straight from the saw into their DH kiln? Say about 400 ft load. How long did it take? I'm looking into my book Nyle sent me and see where it says db 90 wb 86. I don't have any just trying to understand the setting.

No, I have never done it, as it would be painfully slow and inefficient.  For example, generally, 4/4 upland white oak has a maximum drying rate of about 2.5% per day.  If it's 8/4, the max rate would be cut in half, and I generally like to use 1% per day as my target for white oak, anyway.  So a green tree may have at least 50% or 60% Moisture Content.  So right off the bat, it would take about 2 months, at 1% per day, including sterilization and equalization.  Which means under optimum conditions, the kiln is tied up for 2 months.  Now consider the accuracy required to meet that schedule...if the moisture removal rate is misjudged, miscalculated or mismeasured by even a half a percent, the drying time could extend to 4 months of kiln occupancy time, which would be unacceptable to most people. Of course, if it's in error in the other direction, it's a dead load of wood. 

Consider that I try to get a load out every 7-9 days as I try to minimize kiln occupancy time for the finishing and sterilization stage.  So putting green wood, especially white oak, directly in the kiln would cost many lost loads. 

As far as the Nyle settings, they are very conservative and sometime not realistic.  They want the dry bulb at 90 which would be nearly impossible to hit and hold in the the south in the summer, where we routinely exceed that outside air temperature, so venting hot air won't work, as the air coming in is already hotter than what the schedule calls for.  So the kiln schedule is a basic suggestion, and I always figure I will make measurement and suitable adjustments after the first 24 hour cycle after I've measured my moisture loss. 
 
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Offline xlogger

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Re: Big Slabs: Sales and handling
« Reply #81 on: July 10, 2017, 05:04:16 am »
So in your answer on about putting thick oak straight to the kiln is only red oak?
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Offline plantman

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Re: Big Slabs: Sales and handling
« Reply #82 on: July 10, 2017, 06:28:02 am »
I've never dried wood but from a common sense perspective it would seem to make sense that a wood which is permeable like red oak would dry more easily than a impermeable like white oak.

So in your answer on about putting thick oak straight to the kiln is only red oak?

Offline WDH

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Re: Big Slabs: Sales and handling
« Reply #83 on: July 10, 2017, 07:24:55 am »
While still a difficult to dry species, red oak is not as difficult to dry as white oak (one of the most difficult).  Still, I would not put a green load of any kind of 8/4 oak in my kiln because of the very slow and long drying time, tying up the kiln for a couple of months like Yellowhammer points out.  If it is air dried to 20% of less, you can dry it in 1/5 the time, and the wood is not worth enough to me to give up 5 kiln loads for 1 kiln load of oak. 
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Offline Ron Wenrich

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Re: Big Slabs: Sales and handling
« Reply #84 on: July 10, 2017, 11:28:38 am »
I went to a hardwood dimension plant where they had predryers.  Basically it was a shed open on one side with fans pushing air through the lumber.  Most of their lumber was red oak, cherry and maple, at that time. 

I also wonder about getting surface checks in white oak.  I had some that we put on sticks and the buyer was reluctant to buy it because it got surface checks.  It was in the spring, and we had some pretty good breezes and low humidity.  He explained the surface checks came from drying the skin too quick and sometimes they don't seal back up during the kiln process.  Would you have that problem going from green straight into a kiln?
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Offline plantman

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Re: Big Slabs: Sales and handling
« Reply #85 on: July 10, 2017, 11:55:42 am »
I've read a lot about treating wood with antifreeze. The author of a study claimed that he treated the wobbley legs of a chair and they firmed up. He claimed that it would get rid of checks in wood. Maybe everyone doesn't want antifreeze in their wood but it would be nice to simply treat the green wood, stabilize it , and make it ready to use. The author claimed that the color change was not noticeable . Today antifreeze comes in orange as well.

I went to a hardwood dimension plant where they had predryers.  Basically it was a shed open on one side with fans pushing air through the lumber.  Most of their lumber was red oak, cherry and maple, at that time. 

I also wonder about getting surface checks in white oak.  I had some that we put on sticks and the buyer was reluctant to buy it because it got surface checks.  It was in the spring, and we had some pretty good breezes and low humidity.  He explained the surface checks came from drying the skin too quick and sometimes they don't seal back up during the kiln process.  Would you have that problem going from green straight into a kiln?

Offline xlogger

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Re: Big Slabs: Sales and handling
« Reply #86 on: July 10, 2017, 01:18:14 pm »
While still a difficult to dry species, red oak is not as difficult to dry as white oak (one of the most difficult).  Still, I would not put a green load of any kind of 8/4 oak in my kiln because of the very slow and long drying time, tying up the kiln for a couple of months like Yellowhammer points out.  If it is air dried to 20% of less, you can dry it in 1/5 the time, and the wood is not worth enough to me to give up 5 kiln loads for 1 kiln load of oak.
That's what I was thinking but looking at Robert's post #74 threw me off. I guess this should be under the drying topic.
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Offline YellowHammer

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Re: Big Slabs: Sales and handling
« Reply #87 on: July 10, 2017, 11:45:26 pm »
Red oak can tolerate 3.8% at 4/4, half that at 8/4, which is still very slow.  More forgiving than white oak, but generally will still check if thick wood is milled in the summer. I will mill most of my oaks from Thanksgivng to Christmas to get best quality of wood and minimum kiln time.  Slow drying conditions when the wood needs it, slightly faster when the wood can tolerate it.     

Here's why, starting about page six. 
http://sbisrvntweb.uqac.ca/archivage/030108539.pdf
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Offline scsmith42

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Re: Big Slabs: Sales and handling
« Reply #88 on: July 11, 2017, 02:15:04 pm »
When I have dried 8/4 QSWO or QSRO from green in my Nyle, it was a 3-1/2 month kiln run.  I can only do it in the winter because I'm unable to keep the temps low enough to start the load during the summer time.

It was only successful after I added a misting system into the kiln.  During the first few weeks I have to add moisture in to keep the RH% higher than with 4/4; otherwise it will surface check.

Rather than assuming a 50% reduction as thickness is increased, I have had better success reducing the drying rate by 60% per additional inch of thickness over 4/4.  Thus, starting with 3.8% for 4/4, the drying rate for 8/4 is 1.5%, and for 12/4 is .6%.  Since 8/4 QSWO is milled green at around 2-3/8", my targeted maximum daily drying rate is about 1%.

Having said all of that, the only kiln that I'll load with green 8/4 oak is a solar kiln during the fall, winter or early spring.  I have had some excellent success with that.
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