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Mixing species when kiln drying?

Started by oakiemac, November 27, 2003, 09:35:15 AM

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oakiemac

Does it harm anything to mix different types of wood in a DH kiln? I'm taking some Cherry to a guy with a Nyle kiln up the road and he wants to dry it in with some Maple and Oak. I have some money invested in the Cherry so I can't afford to have the lumber come out bad. Also what about different thickness's-say 5/4 and 8/4?  ??? Thanks.

Oakie
Mobile Demension sawmill, Bobcat 873 loader, 3 dry kilns and a long "to do" list.

Brian_Bailey

oakiemac,  

Without getting into the techs of drying, you can mix cherry & maple but not oak. Its best not to mix thicknesses,esp. 8/4. If this kiln operator is putting all this in one load I would recommend finding another kiln.
WMLT40HDG35, Nyle L-150 DH Kiln, now all I need is some logs and someone to do the work :)

Den Socling

Cherry and Maple will be OK together. Cherry could be OK with Red Oak. White Oak would not be a good choice.

There are a couple reasons people like the professor say don't do it. Because of difference in beginning moisture content, the schedule for one might not be right for the other. Green Cherry is about 58% water by weight. Hard Maple and Red Oak are about 70%. Soft Maple can be 100%.

Different species need to be dried at different rates. Maple and Cherry are similar. You have to take it easy with Red Oak or it will crack. You have to go so slow with White Oak, your Cherry might be petrified wood when you get it back.

When you double thickness, you can increase drying time by 250%.

Despite all of this, people mix species and thickness and usually get away with it.

Frank_Pender

From my experience here in Oregon, I have had great success  in mixing species such as Cherry, Oak, Maple and even Cottonwood.  I have found that the key might well lay with the begining moisture content.  I let all of the lumber I dry, air dry for at least 60 to 90 days before they are introduced to the kiln.  Most all species are at about 20% MC at the time of introduction.
Frank Pender

oakiemac

Thanks all. I think I'll have him keep the Red Oak out of the load-just to be on the safe side. I might have enough Cherry now to fill the whole kiln because a customer just dropped off a load of Cherry logs. 8)
Mobile Demension sawmill, Bobcat 873 loader, 3 dry kilns and a long "to do" list.

iain

i,m afraid i mix and match all the time in my DH kilns, but stuff like oak and chestnut always go on the bottom, with clean non dripping stain type woods on the top,
thickness? i try to stay close to 50% through out,
 i also use differant sticker thickness's/old sheets or blankets  to get the air to go where i want it
i've looked through the log's and the last time i dried all the same was 14 load's ago

Don_Lewis

If everything is below 25% (everything means all the boards right to the center, not averages) then mixing is okay and you need to start the cycle agressively, with an EMC equal to the surface MC of the lumber. Otherwise, stick to keeping thicknesses and "groups" together. The groups are species that dry well at similar schedules. For eample, never put AD Oak in with any green wood or wood that is not below 25% and don't add green lumber to a kiln charge of Oak when it reaches 25%. Plenty of people do that but it is too risky for the amount of money involved.

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