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Using Fans for the initial Air Drying

Started by Glenn1, October 18, 2014, 03:10:59 PM

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Glenn1

I have 400 bf of walnut and plan on getting green 4/4 in cherry, maple, and anything else that looks good.  My question is about air drying for the initial stage (the kiln will come later).  I don't get too much air circulation due to all the trees on the property.  Scott in NC suggested that I pick up a couple of box fans which is what I have done.  Will air drying with fans give a similar result as conventional air drying or will the fans dry the wood too quickly?  Originally the center of the walnut was + 50% MC and now one month later, it is 33%.  The edges are now 16%.
Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer

beenthere

How did you measure or calculate those MC readings?
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

Glenn1

I have a Lignomat meter with 12' cables and 6 probes place at various depths. 
Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer

jdonovan

Quote from: Glenn1 on October 18, 2014, 03:10:59 PM
  Will air drying with fans give a similar result as conventional air drying or will the fans dry the wood too quickly? 

Fans will accelerate the drying. Depending on local conditions temp/humidity/fan speed/air volume, it might create too rapid a drying rate.

QuoteOriginally the center of the walnut was + 50% MC and now one month later, it is 33%.  The edges are now 16%.

If you are using a standard pin type moisture meter, you can't accurately be measuring 50%. Really above 20-25% is not accurately measurable with most pin meters.


WDH

I do it all the time.  With those species that you mentioned, you are good to go.  With the oaks, especially white oak, the fans can hurt you by too rapid drying and the resultant defects like honeycombing. 

So, it is species dependent.  You are OK with most species as long as it is not one of the oaks.  Maple, walnut, and cherry will dry faster with the fans, and in my experience, they tolerate it fine.  In fact, here in the deep South, you need fans on maple IMMEDIATELY after sawing to avoid sticker stain in the spring/summer/fall.  Forum member Yellowhammer and I have talked about this issue a lot.  Sticker stain can be a real problem down here, especially with maple and pecan. 
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

GeneWengert-WoodDoc

I would "second" WDH's comments.  I would add that you do not need to run the fans at night when the RH is high, so use a timer...on about 2 hours after sun rise and off about two hours after sunset.

The fans will be most effective when above 40% MC, so no need to use them a lot after the first couple of weeks or month.

You should achieve under 20% MC easily.  For interior uses, the wood needs to be at around 7% MC, so you will need some additional drying.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Glenn1

Thank you!  That is exactly what I needed to know.   8)
Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer

Banjo picker

I have used fans on tulip poplar as well.  Built a tunnel out of some concrete forms  and put a couple of fans on one end.  It pulled it done pretty fast, I didn't know any better and just left the fans on 24/7.  Banjo
Never explain, your friends don't need it, and your enemies won't believe you any way.

YellowHammer

Fan drying certain species of wood is very fast and saves lots of kiln time.  Also, as mentioned, fans are so effective in eliminating sticker stain in certain species of whitewoods that I won't even saw them unless I have at least a couple big fans ready and on standby.  Kudos to WDH for helping me experiment with this, and once you get the feel for it, it's simple, although there is a little bit of a learning curve as to which species of wood can tolerate the effects, but it works exceptionally well in the right situations.

This photo shows a couple big barrel fans sandwiched between pallets of wet maple prior to going into the kiln.  The fans are on "high" and run 24/7 for maple, but I use the speed selector on the fans based on the the species.  As imagined, these fans are putting a lot of air over the wood and evaporating a tremendous amount of water, so that on hot summer months, we'll sit on the downwind side of the stacks to catch the cool breeze.


Same thing, fans placed between stacks of wet poplar.  It's hard to see in this photo, but I have the fans tilted up to cover the upper boards in the stack.


The general idea is that above 40% MC wood will dry faster as the air velocity increases.  Below 20% MC wood will not dry appreciably faster as air velocity increases.  Between 40% and 20% MC the effects of air velocity diminishes.  At higher air velocities drying is more uniform.

So, in other words, immediately after sawing, when wood is very wet, the fans will have the maximum effect in drying, but as the wood dries, the effects of the fans decrease.  So you don't have to keep the fans on the wood very long, maybe two or three weeks at most.  Most of the drying is done the first week, then it tapers off as the the effectivness of the fans diminish. In the hot summer months, I find it is essential to put sticker stain prone wood in front of the fans for at least week, which draws off excess moisture and keeps the wood cool by evaporation, before I put it in the kiln.  Before I started using the fans, I wouldn't saw several species of wood in the dog days of summer because of the problems of sticker stain.

Some hardwoods such as oak will not stand high air velocities without creating significant defects while certain whitewoods and softwoods actually need much higher airflows to force rapid drying and reduce or eliminate sticker stain.  Referencing the published maximum moisture removal rates of woods species will give a good idea which ones will tolerate fast fan drying.

YH


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

mrector

Hey I live just right up the road from you! Anyways I use two cheapo box fans on my lumber after cutting green. Works wonders and I run them 24/7 until they stop losing moisture. Then go into the kiln or stacked for finish air drying. Mostly black walnut and cherry.
Mikey
Woodmizer LT35HD25 brand new!
Stihl 044 and my favorite: ms260 pro
Homemade logging arch
Homemade hitch log picker-upper
DanG Deadheader log loading trailer.

WDH

Black walnut and cherry behave very nicely.

White oak is a delinquent. 
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

Glenn1

Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer

mesquite buckeye

Quote from: WDH on October 20, 2014, 07:41:07 PM
Black walnut and cherry behave very nicely.

White oak is a delinquent.

Not delinquent, independent and free thinking. ;D :snowball: :snowball: :snowball:
Manage 80 acre tree farm in central Missouri and Mesquite timber and about a gozillion saguaros in Arizona.

WDH

It is acting slovenly in my kiln right now  :).
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

Denny

I'll save everyone some Googling time...

slov·en·ly adjective 

: messy or untidy
: done in a careless way
Full Definition of SLOVENLY
1:  untidy especially in personal appearance
b:  lazily slipshod <slovenly in thought>
2:  characteristic of a sloven <slovenly habits>
— slo·ven·li·ness noun
— slovenly adverb

Examples of SLOVENLY
He dressed in a slovenly manner.
<for the sake of their image, the band members transformed themselves from clean-cut lads to slovenly rockers>
First Known Use of SLOVENLY
circa 1568

And then there's this...
http://slovenly.com/

WDH

I pulled the plug on the slovenly white oak.  Going into the sterilization cycle and heat those slovenly acting boards to 150 degrees for 24 hours.  That should teach them a lesson ( and any bugs, too)  :).
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

Quote from: WDH on November 07, 2014, 08:59:53 PM
I pulled the plug on the slovenly white oak.  Going into the sterilization cycle and heat those slovenly acting boards to 150 degrees for 24 hours.  That should teach them a lesson ( and any bugs, too)  :).
That will certainly make them sweat. ;D
YH
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

Magicman

Knothole Sawmill, LLC     '98 Wood-Mizer LT40SuperHydraulic   WM Million BF Club Member   WM Pro Sawyer Network

It's Weird being the Same Age as Old People

Never allow your "need" to make money to exceed your "desire" to provide quality service.....The Magicman

OneWithWood

Danny, will you flood your kiln or somehow add moisture during the last few days?
One With Wood
LT40HDG25, Woodmizer DH4000 Kiln

WDH

The 8/4 white oak is still not dry.  I gave up on it.  I have more important fish to fry.  I will dry some sycamore, walnut, and red oak.  The white oak will have to wait on stickers.  8/4 white oak is awful stuff to dry  :).
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

Den Socling


OneWithWood

I have more trouble with the red oaks, especially black oak, than I do with white oak.  One thing I have learned is you cannot rush the oaks.  4/4 is going to take 28-30 days and 8/4 will take 56-60 days.  I go from mill to kiln with very little air drying so your times will vary.
One With Wood
LT40HDG25, Woodmizer DH4000 Kiln

Denny

Quote from: OneWithWood on November 09, 2014, 12:43:16 PM
Danny, will you flood your kiln or somehow add moisture during the last few days?

Yeah I've been wondering if you guys condition/de-stress your lumber and how you go about conditioning in a solar or dehum kiln.

WDH

OWW,

No, I don't add moisture for conditioning. 

Den,

12/4  ???.  Now I will have nightmares  :)
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

Quote from: Denny on November 10, 2014, 03:24:30 PM
Quote from: OneWithWood on November 09, 2014, 12:43:16 PM
Danny, will you flood your kiln or somehow add moisture during the last few days?

Yeah I've been wondering if you guys condition/de-stress your lumber and how you go about conditioning in a solar or dehum kiln.
I tried dumping water into the kiln and other such techniques at the end of a drying cycle because I used to have a lot of stress in my kiln dried lumber, and fought it for a while.  Somewhere along the line I heard about "making the boards sweat" at the end of a drying cycle, which involves increasingly heating the boards to a point where the remaining core moisture is driven out through the case and eventually to the outside of the board without the kiln dehumidifier running so as not to remove the moisture from the atmosphere.  Since the dehumidifier is not operating, the moisture driven out of the boards just stays in the kiln chamber and is recirculated, significantly raising the RH, pretty much the same as if moisture was introduced into the kiln externally for equalization. Coincidentally, this happens naturally in a DH kiln during the sterilization cycle when the temps are driven up significantly over the normal drying schedule maximum allowable temperature and the dehumidifier is turned off to protect the compressor against overheating (at least in my kiln model).   There may be some other factors at work here, but it is very rare for me to have lumber come out of the kiln with any appreciable case to core differential moisture content and very rarely will I have any stress in the boards anymore, and I try to dry them on the fast side of the drying schedules, which normally induces drying stress.  So for me, the high temperature dehumidifier off sterilization cycle serves multiple purposes, and is a step I never skip.  I hadn't thought about it before, but happy, relaxed boards coming out of a sauna is a pretty good description. ;D

As far as a solar kiln, it gets equalized every night.
YH 
     
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

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