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Author Topic: Snowballing wood kiln build  (Read 1474 times)

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Offline dougan2469

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Re: Snowballing wood kiln build
« Reply #20 on: November 28, 2017, 12:16:17 PM »
Hello all!

I recently loaded up the kiln with around 140 BF of fresh off the saw cherry. I got the average moisture content down to 20% without much if any degrade.

I am using Table (T8-B4) from the kiln schedule manual with my kiln settings at 109DB, 83WB 30%RH and temp are rock solid with only the heat running.

My question is... Am I being to cautious after hitting the 20% range or keep doing what I am doing? I am not currently running my compressor because of 1) possibly being over cautious and 2) The compressor has practically stopped putting water in the collection bucket.

My belief is (correct me if I am wrong) there is not enough moisture in the chamber due to the very small load of lumber.... And the water is evaporating out of the drain pan and drain tube before it can reach the collection bucket.

Also I am not to sure how much I trust my DIY redneck wet bulb probe. LOL It is keeping the probe wet at all times and I have it positioned for optimal CFM across the probe.


Offline dougan2469

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Re: Snowballing wood kiln build
« Reply #21 on: November 29, 2017, 10:59:41 AM »
I should have been more detailed in my process.

I am using (T8-B4). I cant achieve the temperatures listed in the chart so I am changing my relative humidity to match the moisture content in the wood and using (T8-B4) to tell me when to change.


I went ahead an turned the heat up to 115 last night. Doing so raised my wet bulb to 87 and I left the relative humidity at 30 percent.

With these settings I should eventually get my final moisture content in the mid to upper 5% range. If I am doing my math correctly LOL

Offline YellowHammer

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Re: Snowballing wood kiln build
« Reply #22 on: November 29, 2017, 10:32:11 PM »
Hello all!

I recently loaded up the kiln with around 140 BF of fresh off the saw cherry.

My question is... Am I being to cautious after hitting the 20% range or keep doing what I am doing?

Also I am not to sure how much I trust my DIY redneck wet bulb probe.
(Image hidden from quote, click to view.)

All different species have a maximum allowable moisture removal rate before they start to degrade.
There are tables available, but 4/4 cherry is generally around  5.8% per day, white oak is about 2.5% per day, and soft maple is about 13%.  The only sure fire way to know where you are on the drying rate is to use the oven dry method for calculating moisture loss rate and compare it to your kiln conditions.  I did this for severa species when I first started, to get a true feeling for the kiln schedules, the behavior of the wood, and the actual moisture removal rate.  Also, it's very useful to have a calibrated catch container under your condensate hose to physically measure how much moisture was removed each day.  I graphed these values in a spreadsheet and got a much clearer understanding of what was going on.  From there, I was able to tailor my kiln schedules as necessary to stay very close to the maximum moisture removal rate curve, while not ruin a load of wood.  It also led me understand under what conditions I could trust or distrust my moisture meter and chamber probes. 

It's a useful exercise, and one that has been paying dividends for years. 

 
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Offline dougan2469

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Re: Snowballing wood kiln build
« Reply #23 on: November 30, 2017, 05:09:16 PM »
Thank You YellowHammer,

I tried the scales I have available and they are definitely not up to the task.
Adding a bit of salt to the wound, the new moisture meter I purchased up and vanished... Hope it left me for someone more attractive. smiley_furious3

I have been checking the load daily with my old meter but I can definitely throw it farther than I trust it.

After Christmas I will get another meter and a set of good scales. The wife thinks spending money for the kids Christmas is MUCH more important than my hobby science project. ::)

I am guessing at this point but I think I will over dry the hell out of some of this cherry just to see what happens. I don't have much money in it and I would like to know how low I can get the moisture using this kiln.

I will continue lurking till after the first of the year so... :christmas: and  :new_year: TO ALL!!!!!

Offline YellowHammer

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Re: Snowballing wood kiln build
« Reply #24 on: November 30, 2017, 05:44:52 PM »
Why wait?  A suitable set of scales can be had at Wal Mart for $25.  A nickel weigh exactly 5 grams, so it's easy to check their accuracy. 
Here's a link to a previous post in the subject.  Once you do it, you will be surprised how easy it is to check the moisture levels. 

If you want to speed dry, then use the oven dry "microwave" method, it works fine, just don't stink up the house.  A regular oven will also have the sample board dry over night or a little longer.

If you over dry cherry it will get very angry and buck up, curl, and otherwise start to display significant poptatochip-itis.  Straight boards will become not straight at about 6%.  So I like to dry cherry to 8%, then sterilize and the boards will lose about another percent to land on 7%.  There is some Kentucky windage to be accounted for. 

This is one reason moisture meters can really get someone in trouble, the lack of true accuracy, or overconfidence in the device.  For example, with white oak, it's a game of percentages.  Over dry the wood to 3.5 % per day and the load is ruined.  Dry at 2% and that will result in a good end product.  Underdry at 1% per day, you will still have a good product, but it will take twice as long to dry.  So a board at 40% will take 40 days to dry vs 20.  That's a long time when drying for production, like we do.  So what if the moisture meter is misreading by a single percent?  Either a dead load of white oak, or double the drying time.  One percent is big.   

Don't get me wrong, a good moisture meter is worth having, but only after it has been proven to be trustworthy.   


Hobby Hardwood Alabama.com
LT40 Diesel Hydraulic, Stihl 028, MS440, MS660, 2 Kilns

Offline dougan2469

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Re: Snowballing wood kiln build
« Reply #25 on: December 22, 2017, 12:15:34 PM »
I couldn't take it... I had to put something in the kiln LOL

I took your advice Yellow Hammer...This is my first oven dry load test and although it sounds like a royal pain in the bum. It's not as confusing as it sounds once you do it. I will be getting a better scale in the near future but this is a very good learning experience for me.

I tossed a 400 BF load consisting of walnut and white ash cut to 4/4+ 1/8" in to see what it does. This is how it is coming along...


I am trying to stay at or below 3% in 24 hrs because of the mixed load.

Does my calculations look correct?  Oven dry weight is 2.447 KG on the top left of the board.

If I haven't messed things up with my calculation I believe I will be drying loads this way from now on.  ;D 

Offline AlaskaLes

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Re: Snowballing wood kiln build
« Reply #26 on: December 22, 2017, 01:19:19 PM »
We've got the Mini-Ligno DX/C kit that you gave away to a needy individual and it works well.

I had a hard time finding a quality scale that would provide the fine resolution and also the large payload to weigh any sample board I was inclined to use.

Ended up buying a Mettler Toledo XTC-4001 from a scale store in town.
It will weigh 50lbs with .5 gram resolution.   I couldn't be happier.
Compared to the other options in this quality and range it was a good price at about $250.00.
Not cheap, but a fair price and it is very accurate!!
I'd buy it again in a second.

Our most recent kiln purchase was a box full of new/stronger draw latches for the loading doors.
The first set just wasn't strong enough and they're showing the strain.
These are rated for 250 lbs each or so.
Still cost almost $200 for a dozen latches...kilns done right are not a cheap tool...lol.
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