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When should I recommend kiln drying

Started by Minnesota_boy, January 24, 2004, 04:39:13 PM

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Minnesota_boy

Suppose I go to custom saw some red oak for a customer.  Should I have him haul it to the kiln immediately, or let it air dry for a while first.  If he has it kiln dried right away, will this induce more stresses in the wood?  Will kiln dried red oak have more or less stress than air dried?
I eat a high-fiber diet.  Lots of sawdust!

sawwood


 From what i have read and talked to guys that have kilns
 they say you should kiln oak as soon as its cut. The only
 time they might let it air dry it to shorten the time in the kiln.

 I know Larry with his solar kiln he air dry some while he has
 a load in the kiln. This way you can dry more in a year by
 having a load dryed down and it don't take as long.

 Sawwood

 Jeff sure like this new fourm and i will sure will learn a lot.
 Thanks
Norwood M4 manual mill, Solar Kiln, Woodmaster
18" planer/molder

Den Socling

I like to see wood dried as soon as it is cut. When you air dry, you are going to get some degrade. Degrade will probably be end checks and maybe mold or other stains. On the other hand, air drying can remove a lot of the 'easy' water and cut kiln time down drastically. Suppose it takes two months for you to dry a charge of 4/4 Red Oak but you can only earn $250/1000 BF. You have to air dry to keep from going broke.

Stress is caused by large MC gradients. This is what you have when the outside is much dryer than the center. Air drying might produce less stress because, if done correctly, it is slow and doesn't cause a large gradient. In a commercial kiln, time is money so you may be pushing to get the wood dry as quickly as possible. You will end up with stress. But, at the end of drying, you use equalizing and conditioning to relieve the stress.

Larry

MB,
Call the kilns in your area and see what their procedure is first.  In this area  none of the kilns will load with green wood for two reasons.  First they are always running behind and second they want that wood to air dry for 2 or 3 months to save on energy costs.  If you did find a kiln that would dry green wood I'm sure they will charge a premium because it going to cost them more.

Den is right about air drying causing some degrade.  A few steps can be taken to minimize  degrade.  Cover on the top of the stack, end coating, and orientation of the stack to the prevailing winds.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

HORSELOGGER

Awesome new forum... I was talking with a guy a Nyle last week when ordering some pins for my moisture meter , and he had recently been to a drying seminar where they had said that the best results from air drying for a couple of months came from restacking the pile midway thru so that the middle boards would become the edge boards, and equalize the MC thru the pile. Apparantly some guys test the outside boards, get a low reading after a few months of air drying and put the screws to the load as soon as it is in the kiln, resulting in a lot of degrade, because the inner boards were still wet.  I just closed up the kiln today with a load of fresh sawed 4/4 white oak for a flooring order. It was 24 degrees when I turned it on at noon, and by 4 it was 34 degrees. I hope to be dry in about 25 - 30 days, losing 2.5% per day. coming down from 60%. I have vowed to keep better records this year so i am looking forward to this forum to share and receive some good info. ... Oh yeah, I am drying in a Nyle 200, in a chamber I built last year and insulated with spray urethane foam( outstanding stuff ) and most of what I dry is for my flooring shop.
Heritage Horselogging & Lumber Co.
"Surgical removal of standing timber, Leaving a Heritage of timber for tommorow. "

Fla._Deadheader

I will sure be watching for your input, Horselogger.

  We are getting close to sawing a bunch of sinker Heart Pine. Wet and sticky is the term, here ::) ;D
All truth passes through three stages:
   First, it is ridiculed;
   Second, it is violently opposed; and
   Third, it is accepted as self-evident.

-- Arthur Schopenhauer (1788-1860)

HORSELOGGER

Hi Harold, We've been around the zero degree mark with lots of wind for a couple of weeks now. I logged 13 nice old white oaks in the cold and took em home to saw for this order. I noticed that the logs really sawed out nice on the Peterson frozen solid . Maybe you should haul them pines up here for a freeze job and trim!
Heritage Horselogging & Lumber Co.
"Surgical removal of standing timber, Leaving a Heritage of timber for tommorow. "

Kirk_Allen

Although this post may be better on another thread I thought I would start hear since the subject of drying flooring came up.

I have been taking a barn apart for about two years now, board by board.

When I first started the project it was to get enough boards from the grain storage side to install a oak floor in our home.

It was a barn that my Great Grandfather built and by all indications it was built in 1880.  All the wood used was Red and White Oak.   All of the main load bearing timbers where white Oak and the siding and grain slats were red oak.




Now this is a barn that has been exposed to Central Illinois weather for over 100 years.  Both types of oak reflected a 10% moisture count.  I brought the wood home, planed it, sized it, tongue and grooved it and installed it.  

I have found that the first section I did, which was the entry way with a ship lap and screwed down construction has not moved or separated at all.



I have very minor separation on the main floor that was tongue and groove but I think that was because I didn't tongue and groove the ends of the boards, only the sides.











I used the White Oak to build the work bench.  It weighs in at 350 lbs. 8) 8)




Kiln drying I think ensures the killing of any bugs that can be a real problem in some cases.  I have found woodworm's in air dried lumber but most of the time it had been exposed outside for many years.  To date, I have not needed any kiln dried wood for my projects.

ElectricAl

Harold,

That sticky sap will cause you and your customers problems is the sap is not "Set".  "Set" is the highest temp the lumber reached during drying. So any machining of the lumber cannot exceed your "set" point.

Many DH kilns only go to 120 degrees. 120 is to low a set point. If the lumber is sanded on a power sander, heat is generated and the sap will become liquid again and gum up the sander >:(

A conventional style kiln using hot water can get to 145 degrees. A steam kiln will go to 180 or more.

I realize a steam kiln is a little more $ then most can afford, but a Hot Water conventional kiln powered by an Out Door Wood Burner might be affordable.

I have read that standard drying schedules for SYP are to aggressive for sinkers. Drying sinker lumber is more common now and some revised schedules should be available.

Just something to think about.
Linda and I custom saw NHLA Grade Lumber, do retail sales, and provide Kiln Services full time.

Paul_H

The WM DH4000 I'm using has been setting the pitch at 170 F with no problems so far.I had read to hold the temp for 24 - 36 hours.Different times from different sources.

The last few loads have been 36 hours for setting the pitch in Douglas Fir.

Nice job on the floors Kirk 8)
Science isn't meant to be trusted it's to be tested

Plowboy

Larry what do you mean by stacking the lumber for the prevailing winds?  Do you want the wind to blow through the length of the stack or the width of the stack?  Here at our place we try to air dry for a while because there is always a load in the kiln.  This system seems to work the best for us.

Kirk great job on the flooring, looks wonderful.  The corn crib that you took down is like the one that we are air drying some of our lumber in.  

Fla._Deadheader

Thanks Al. Been communicating with Larry Copas, and he has me building a "mini" kiln. That should answer SOME questions. ;D ;D
All truth passes through three stages:
   First, it is ridiculed;
   Second, it is violently opposed; and
   Third, it is accepted as self-evident.

-- Arthur Schopenhauer (1788-1860)

Larry

PB,
During the spring we get a lot of hot and dry wind out of the south.  If allowed to blow unobstructed through a stack of green oak, excessive checking is the result.  To reduce the effect of the wind I build the stack 8' wide with the ends facing north and south.  The orientation also helps to keep wind driven rain out of the stack.

Conversely with an easy to dry white species you could use the wind to your benefit to eliminate stain.  
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

Plowboy

Thanks Larry, I was wondering if we were doing something wrong.  I wasn't sure which way to have the prevailing wind flow over the wood.  Plowboy

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