iDRY Vacuum Kilns

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DH Kiln capabilities

Started by woodsy, October 03, 2011, 06:19:49 PM

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woodsy

What are the capabilities of DH kilns? Are they capable of successfully drying thick hardwoods from 10/4 through 16/4 and maybe even some 20/4? Species I am interested in drying in these thicknesses are cherry, maple, walnut, ash, pine, and white oak.  The 20/4 may be a stretch for me, but still I am curious to hear about it.  Thanks.   
LT40HDG38, Logrite T36 log arch, 42 hp Kubota, 6 foot cross cut saw, lots of axes and not enough time

OneWithWood

The DH kilns I am familiar with are limited to 8/4 and less.
One With Wood
LT40HDG25, Woodmizer DH4000 Kiln

oakiemac

I have dried 12/4 walnut before but all the wood was 3x3x10 so it dried a little faster. Takes a long time to dry that really thick stuff.
Mobile Demension sawmill, Bobcat 873 loader, 3 dry kilns and a long "to do" list.

zopi

I think there is a point of dimonishing return there...you put so mich time amd energy into getting a thick piece of wood to dry...just not worth it...for stuff like that you might be better off putting it in a solar tunnel or something...
Got Wood?
LT-15G GO chassis added.
WM sharpener and setter
And lots of junk.

Ironwood

That is a tough one, that is pretty thick to REALLY get it dry on the inside.

Ironwood
There is no scarcity of opportunity to make a living at what you love to do, there is only scarcity of resolve to make it happen.- Wayne Dyer

woodsy

Okay.  So how about just 10/4 and 12/4?  Is this something DH kilns can dry?  If not, than what are people and/or commercial outfits using to dry thick woods?  Conventional (steam) kilns?

Perhaps I should start a new thread to ask this question, but what are the differences, pros and cons over a conventional (steam) kiln and DH kiln.  I understand how the two remove water from the wood/kiln and the energy required to do so, but other than that what are the differences.

Most large commercial kilns around me use convention kilns.  Why?  Is this saying something about the quality of the finished product, capabilities, etc? 

Thanks.
LT40HDG38, Logrite T36 log arch, 42 hp Kubota, 6 foot cross cut saw, lots of axes and not enough time

beenthere

Walnut gunstock blanks used to have a 7 month kiln schedule in conventional kilns.

Drying 4/4 is quicker, and laminating to get 12/4 is often a sub for the 12/4 solid.

Am trying to think what wood products are commercially available in 12/4 thickness. ??
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

woodsy

Commercial wood products that are being massed produced from 12/4 and sold in a retail/wholesale setting? I don't know; that is not my area.  I just know there is a call for thicker wood in specialty/custom markets.
 
I typically see Popular, Cherry, Maple, Walnut, Butternut, Basswood, Red and White oak available in 12/4 and in 16/4 (except the oaks in 16/4).  Every now and then I see 20/4 maple. As I understand it places drying 20/4 maple in a commercial/wholesale setting  have basically sold it all before the kiln even starts.  They get buyers lined up ahead of time.

Zopi, what is a solar tunnel?  A solar kiln?
LT40HDG38, Logrite T36 log arch, 42 hp Kubota, 6 foot cross cut saw, lots of axes and not enough time

Tom L

I am going to try to give you an answer from my very, very limited experience that I have had with my small
makeshift kiln in my garage, (holds 500 board ft) I only have been cutting  2" to 3-1/2" thick stock on my mill, white, red cedar and white pine. ( some at 4-5")

after a lot of questions, and some good answers here on the forum, the kiln has been doing a much better job at the thick stuff. my first two loads were all  cedar and with the temp at 100-105 degrees the wood dried to 11%
in a week and a half, I noticed some checking and checking at internal knots. I don't use that material at all so I just cut around the defects. the last load that is in the kiln is a mix of pine and cedar, all the material is 2-1/2" x 6-1/2" to 9" wide, I have now been running the air conditioner in the box along with the dehumidifier, the temp does not go above 85 degrees, what I noticed is that at the lower temp there is almost no checking, and the knots are all tight. no checks in the middle of the boards. it is in it's third week and should be ready after this weekend to come out and get worked on. so I think the lower temp has helped with the quality of wood, and the extra week in there is not killing me. there are three pc in there now that are 4-1/2" thick cedar. and they look great as of yesterday.
I don't know what scale you need to dry too. a lot more than me I am sure. but this setup I have now is working. leads me to believe that the larger manufacturers of kilns that use DH would work even better.

Ironwood

Most pine and cedar dry very quickly and give their moisture up easily. Hardwoods and generally resin impregnated pines are much tougher. Especially hardwoods.


Ironwood
There is no scarcity of opportunity to make a living at what you love to do, there is only scarcity of resolve to make it happen.- Wayne Dyer

Charles

I agree with Tom on the slow drying schedule and 85f temp. I have a very small kiln and dry at around 85-90f and have dried 8/1/4 and like Tom says it does take a long time if you push it is going to check on you.
If you can get the MC of the lumber to 20% or below by air drying the risk of the doing damage to the lumber is very minimal some will say that under 20% the lumber is almost bullet proof

charlie

woodsy

Tom, thanks for the input.  One of my initial thoughts was to create my own kiln that dries slower than normal conventional or Dh kilns but quicker than air drying.  It sounds like you have done the same Tom and with success.

For me it is all about the quality of the end product and not necessarily about how fast I can push a load through the kiln.  Currently I air dry most of my material and I have had good success with the thicker material but I would like to be able to dry the thicker material quicker than waiting for it to air dry.  I would also like to have a little more control over the drying too. 

If it takes me several more weeks or even months to dry wood in a kiln that people want/need and can't buy elsewhere, then what's the big deal about a longer kiln charge in this scenario?  What is the alternative, wait 3 years for 3 inch thick stock to air dry somewhere below 20%?  I can't compete with mills and kilns putting out millions of bf a year but I can compete with hard to find products that big mills don't seem to be willing to produce.   Anyway, thanks for sharing your thoughts on this.
LT40HDG38, Logrite T36 log arch, 42 hp Kubota, 6 foot cross cut saw, lots of axes and not enough time

LorenB

I have no experience with any kind of kiln yet.  (A DH kiln is under construction.) 

I have HEARD that a vacuum kiln is about your best bet for drying really large pieces with minimum degrade.  Even then, you'll have some losses. 

Here's a link to a commercial site that has more information.  I realize that they are in the business of selling kilns, but it is worthwhile to see what they have to say.
http://www.pcsvacdrykilnsltd.com/faqs.html

-- Loren
Loren
Baker 3667D portable sawmill, Cook's edger, Logrite arches & peaveys.  Husky 272XP chainsaw & two Echos.

Den Socling


LorenB

Quote from: Den Socling on October 17, 2011, 09:07:46 AM
Surprise. I own PCS VacDry.

Den,

Is it true that a vacuum kiln gives less degrade, especially for large lumber? 

I'd have to be drying commercially before I could justify the cost of one, but what I've heard about them impresses me.  I wonder how much of that is hype. 

-- Loren
Loren
Baker 3667D portable sawmill, Cook's edger, Logrite arches & peaveys.  Husky 272XP chainsaw & two Echos.

Den Socling

I don't want to sound like a salesman but I love to talk about vacuum kilns. They can dry 12/4 Red Oak in 12 days with zero degrade, for example. They have knocked my socks off.

Most of the commercial mills who want vacuum kilns want them specifically for small orders of thick stock. Notable exceptions are baseball bat billets and hard maple lumber.

When I got into vacuum drying back around 1982, vacuum kilns had a bad reputation. Too much hype and too much destroyed wood. The people delivering the hype weren't completely to blame. Sometimes you would get great results. The problem back then was nobody knew enough about the process to get two good loads in a row.

woodsy

I have read the pcv website and other literature on vac kilns very thoroughly and more than once. They are very convincing and they do in fact appear to be the proper kiln for drying thick material. Unfortunately I think they are cost prohibitive for me.  I have not totally written them off, just for now.  I just don't think I am or will be moving enough material any time soon to make the economics work. I hope that will change in the near future.  Until then I have to stay within my budget.
LT40HDG38, Logrite T36 log arch, 42 hp Kubota, 6 foot cross cut saw, lots of axes and not enough time

logboy

Den, if a guy wanted a PCS VacDry, how much would it set him back? I'm looking to dry slabs mostly. I'm setting up a conventional DH kiln at the moment, but thought I'd check out my options to see if I could even afford it. I'm guessing no from the looks of things.
I like Lucas Mills and big wood.  www.logboy.com

logboy

Never mind, just found the answer. "Prices start at $99,700."  So I can buy a new house, or a vacuum kiln. Guess which one I wont be buying.
I like Lucas Mills and big wood.  www.logboy.com

OneWithWood

 Wow, logboy, your wife will let you give up on the house that easily?  :D :D :D ;D
One With Wood
LT40HDG25, Woodmizer DH4000 Kiln

Den Socling

yeah logboy. I had to put that price at the website. I was tired of shattering dreams. It's better to have the price right there so that the dreaming doesn't get out of hand.

GeneWengert-WoodDoc

A DH kiln basically is only different hardware for controlling temperature, humidity and air flow.  So a good DH kiln will do as well as a steam kiln, and maybea bit better due to lower temperatures.  So, regular kilns with good controls can dry thicker wood, although air drying is often a good predrying choice.  So, a good DH can also.  But, vacuum might do better.  Remember that the overall cost is important when choosing a drying process.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

logboy

Right now I'm concentrating on the slab market since it seems a bit more insulated from the economy than the lumber market. That, and there arent nearly as many people doing it. When I bought my Ebac a few years ago, I bought it with the intention of doing just lumber. After the last couple years of sitting on lumber thats not selling, and having people request far more slabs than I have, I started chasing the niche.  Drying is the bottleneck now. I have some WO slabs that were air dried 5 years and are beautiful after planing, with minimum drying defects. Unfortunately a 5 year slow drying period is a luxury I do not have. Hence the inquiry into the vacuum kiln. I guess I will be learning to dry 10/4-12/4 slabs by trial and error in my DH kiln I'm building.
I like Lucas Mills and big wood.  www.logboy.com

WDH

logboy,

That is a fine woman that you have  ;D.
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

logboy

I have pushed my sawmill business purchases to the limit. My "owe her" list is pretty long at this point.
I like Lucas Mills and big wood.  www.logboy.com

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