DH & thick hardwood

[Den Socling]

F.A.O. Don Lewis

Don,

A Nyle salesrep told a forum member that a L200 would do well at drying bowl blanks. Would you agree? What would you say are the limits of thickness in a DH kiln for the common hardwoods like Cherry, Oak and Walnut? How long would the kiln charge take?

Den

[old3dogg]

Den.
I have had the chance to "work" with some 8/4 RO dried in a DH kiln.60% of it went to the boiler.
I heard that it took 3.5 months to "dry"
Oven samples said the final MC was at 12%.
A long way from dry!
Dont know a lot about DH drying but............
Mike.

[sawwood]

 I had Larry dry some 2" thick oak in his solar kiln. it was
 just a few boards and the rest was 4/4 oak. Seem like it
 took 3 months to dry and it didn't do to good. I still used it
 but there was a lot of waste. Most bowl turners i know use
 a old icebox with a light bulb and fan to dry there rough out
 bowls.

 Sawwood

[WoodChucker]

So are you guys suggesting that a DH kiln can't dry 2" lumber? I'm getting ready to build one and this is disappointing news if thats the case. Thanks!

R.T.

[old3dogg]

WC.
You can dry 2" lumber in a DH kiln.Its just a slow process.
What species are you going to dry?
Mike.

[WoodChucker]

It's mostly red oak, ash , maple and some poplar.  I'd say about 75% is red oak. So lets say 1" red oak took 45 days to dry (I'm guessing) , how long would it take for 2" to dry?  Thanks!

R.T.  

[Don_Lewis]

Nyle has a number of customers drying bowl stock. Some do softwoods and some hardwoods. There is a substantial risk with drying bowl stock. Much depends on how it is sawn, or shaped and then dried and how much the person doing it really understands about what happens to wood as it dries. . Factors that are out of the control of the kiln operator can create lots of problems. I don't think one method of drying is significantly better than others.  

[Den Socling]

Don,

When I think about bowl blanks, I'm thinking 4" or more square. Can a DH kiln do 4" or more (hardwoods)?

The question drifted to 8/4. I know a DH kiln can dry some 8/4. Give us some basic times for the common species. WoodChucker, for one, needs this info.

Den

[Don_Lewis]

Yes, a dh kiln can dry 4" squares. We had one customer that filled two kilns with 50,000 BF each of 4" Red Oak Squares. Big bucks at risk and it took 6 months to dry. He did two loads a year, 200,000 BF which sold at a substantial premium.

[Den Socling]

6 months is considerably longer than the 14 days that the 4" squares would take in a vac kiln but forget that thick stuff. What can the average guy with a little DH kiln expect when drying 8/4 Red Oak, White Oak, Cherry, Soft Maple, Hard Maple, etc.

[WoodChucker]

Holly jingles, 6 months just to dry 4" squares? I sure hope it doesn't mean it takes half that time (3 months) to dry 8/4 red oak? I thought maybe at tops it would be 45 to 60 days.

Den how much does a small vac kiln cost? Say something that would do around 1500 to 2000bf of 12 foot lumber? Is it even something a small fry like me would even consider?  :-/

R.T.  

[old3dogg]

WC.
But Don said the guy dried 100,000BFT of 4" Red Oak in 6 months.Thats a lot of wood.
Could a small fry like yourself use 2000BFT of 8/4 RO every 2 weeks?This is the question you need to ask yourself when considering a vac kiln.

[WoodChucker]

Yeah your right, I didn't think about it that way. All I really need is a system thats going to dry wood in 4 to 8 weeks. Seems like a DH kiln should do that, wouldn't ya think? Thanks!

R.T.

[woodhaven]

Another thought to consider. When a DH unit fails you can run to your nearest air conditioner contractor and get a part. Can you do this with a specialty system?

[old3dogg]

Sounds like the "hardest" wood that you want to dry is the 8/4 RO.The Ash,Cherry,Maple and Poplar should be fairly quick and easy in a DH kiln.
Den is the only vac kiln company that I know of here in the USA and knowing Den,he can get you parts in a hurry.
Da Man got connections!

[WoodChucker]

woodhaven, I couldn't tell ya, I'm pretty stupid when it comes to kilns of any kind.  

old3dogg, I think I got excited to quick, hey? lol.  

Thanks guys!

R.T.

[woodhaven]

WoodChucker
So that sounds you need to dry 100,000 BF

[Den Socling]

I should add that we have customers who run Nyles and DryLines and they are drying 8/4 hardwood successfully. I just don't know how long it takes.

And six months IS half the time that it might take for 4" RO squares in a conventional kiln, I'm told. I can't imagine starting a year-long kiln charge.

[old3dogg]

I was told 10 weeks to dry 8/4 RO in our DH kilns but the results werent that good.A lot of honey comb.

[Tom]

I have an Ancsots kiln and every load I start will be a year or better. :P

[Den Socling]

WoodChucker,

I'm not selling vac kilns here and I'm not telling you how much they cost because I don't know how to do CPR through the internet.  :D

Den

[WoodChucker]

WoodChucker,

I'm not selling vac kilns here and I'm not telling you how much they cost because I don't know how to do CPR through the internet.  :D

Den

lol, that bad hey?

Well I'm getting more confused now then I was before. A few months ago just about everyone I talked to said a DH kiln was the way to go. I'm just about finished with my building site and getting ready to order insulation for the kiln. But now I don't know if I should or not.

Lets get back to basics here for a second, about how long would it take to kiln dry a load of 4/4 red oak that has been air dried for a few months? Say 2000 bf. I'll be using a Nyle L50 DH kiln and most of my lumber is 8 to 12 feet long.

And if anyone is drying 8/4 red oak under like condition, how long does that take you? Thanks!   :-/

R.T.  

[Don_Lewis]

8/4 Red Oak (and Maple etc) should ALWAYS be dried from green. Low temp (120F) kilns will take about 80-90 days and 160 F DH kilns will take about 65-75 days. Vacuum kilns will dry in about 1/10th the time, but loads are smaller so at the end of 2-3 months, for the same investment you will have about the same amount of wood dried.  Operating costs are not much different and there is debate about the relative quality but we have had really good success with DH kilns and 8/4 Red Oak. When there are problems with quality, it has almost always been related to stock that was air dried first but that would be the same with both DH and vacuum

[Den Socling]

Thank you Don.

I created this discontinuous vacuum monster specifically for people who want to dry small quantities of heavy stock. I suppose it could be scaled to do some lumber but I never intended for it to be competition for DH. And the idea was for people who have a lot of do-it-yourself capability.

Den

[DanG]

Don, you said 8/4 RO should always be dried from green. I assume the same is true for 4/4 stock. Can you expand a bit on that?  What sort of problems occur from pre-drying?  Is there a known reason for it, or is it just a "statistical" rule?

I guess the other thread I started was redundant to this one. :

[WoodChucker]

Thanks Don,

appreciate the info and like DanG, I'm curios as to why 8/4 red oak needs to be dried from green and if the same rule would apply to 4/4?

Ninety days is not that long for 8/4 if drying it from green, maybe a little harder on the pocket book to operate the kiln for that long. But not having to wait the extra few months air-drying would really be nice. Anyone else doing it this way? Thanks!

R.T.

[Don_Lewis]

8/4 must always be dried from green. 4/4 can be air dried and then finished in a kiln but that is not as good as drying from green. One mistake many people make drying Oak after air drying is to dry too slowly. People say, "I want to be careful and not rush it.' Big mistake. The key to drying green Oak is to be sure that the EMC at the beginning is at or below the MC of the outside surface of the lumber. Slow drying can do lots of damage and it just the opposite of what most beginners think.

[Brian_Bailey]

I think that a lot of problems encountered in air drying lumber esp. oak is that not enough attention is paid to monitering and controlling the air flow thru the pile.

The folks that seem to have the most problems just stack and forget about the pile until its time to put it in the kiln.

A warm afternoon and a sudden increase in wind speed will spell doom on your freshly cut oak.

Another factor in air drying to watch out for is how much dust is blowing around your lumber stacks.
Dust, small as it is, can act as a wedge in those small surface checks that should close up in the later stages of drying.

I don't saw enough 8/4 to justify tying my kiln up for 3 mos., so I'm forced to AD and then finish in the kiln.
With a little care up front I get a decent product on the other end, but not always. DanG, white oak anyways!

Certainly the controlled enviroment of a kiln would be best.

[WoodChucker]

Don, thanks again!  Unless you have a pretty big operation with several kilns or at least a very large kiln, I would think most of us would be forced to air-dry lumber just because of the time factor, or we wouldn't be milling much lumber.

So, if I had a load of red oak drying in my kiln and another load waiting to go in, is there anything I could do that would help to preserve the lumber waiting to go into the kiln? Is it better to try and slow down the air-drying process or dry it as fast as possible?

Sorry for all the stupid questions, I'm sure one day it will all click and I'll understand this stuff a little better, but I'm not there yet and really appreciate being able to, not only pick your brain, but the other forum members as well. Thanks guys!

Brian_Bailey, what you say makes a lot of sense, thanks for your input!

R.T.  

[Don_Lewis]

If you have to air dry 8/4 Oak, just do it in the winter. Not during warm weather. Make sure it is protected from sun and rain and use something like Shade Dry

[WoodChucker]

Thanks Don, I should have been more clear, I wasn't talking about 8/4, I meant to say 4/4. But I guess it would be treated the same, right? Anyway, thanks!

Oh, I do have one other question in regards to insulation,if you don't mind?  Is it OK to use the fiberglass rolls of insulation between the studs if you cover it with the rigid foam insulation and a VB?  And would I want to have the rigid foam on both sides of the studs (inside & out)? Thanks!

R.T.

[Tom]

It's a AuNatural-Cylindrically-Supported-Open-Tin-Shed

[Jeff]

Tom, whats an Ancsots kiln? ;)

[Tom]

I'm glad you asked that Jeff :D

In anticipation,  the explanation above. ;)

The delay must have something to do with our being so far back in the woods.  It takes two days for electricity to reach us here.  It makes it kind of hard to keep a thread in order ;D :D

[Jeff]

I need to know more. I'll take this off of here and ask you in a personal message if the roof is tin. Sorry! Back to topic fellers.

Now Tom, is.... ;)

[WoodChucker]

Tom, I'm sure I'll be sorry I asked this, but why is it round? Are you trying to dry the whole tree at one time ?  ;D

R.T.

[Jeff]

WoodChucker yer off topic!   :D

[old3dogg]

well darn it! Now you got me wondering!

[Tom]

Naw, Man!!   the supports are round, The roof are square.  Kinda like Pi.  You know Pi are round. :-/

[WoodChucker]

Yeper, I can cipher that.  ;D

R.T.

[Den Socling]

gee I had a reply to make but I guess it's time for a new thread  ;)

[Tom]

Naw, there's  room, Den.   Jump in.  The water's fine. :D  A reply here would make it fun trying to figure out what it went to. :D :D

[Den Socling]

Ok.

Mike,
Your DH kilns are pretty old, aren't they. What were they? Anklesocks?

Den

[Den Socling]

Oh yeah. I was going to say that we should build a vacuum predryer for 8/4 RO. We should be able to get down to 28% in about 4 days.  :D :D :D :D :D

[Tom]

 8) :D :D

[old3dogg]

Den.
I have no idea how old the DH kilns are.You know?Its kinda weird but all of this time at BWP and Ive never been up to see those kilns.
I dont think its so much the kilns that give the bad 8/4 RO results but more the person they have operating them.
I have 3 vacuum predryers!You guys can have them!
Mike.