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Author Topic: Snowballing wood kiln build  (Read 841 times)

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Offline dougan2469

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Snowballing wood kiln build
« on: October 30, 2017, 03:22:00 pm »
Hello all. I am a long time lurker first time poster. I have been a hobby woodworker for going on 25 years now and was always interested in the idea of drying my own lumber. I am finally in a position to build a kiln of my own and though I would share the process with everyone here. Before I get in to it, I would like to say I am aware of many of my mistakes some are correctable others I will have to live with. What I am looking for is the "OMG" DON'T DO IT THAT WAY!!!" comments.  ;D

This project started on paper as an 8' long 3'X3' plywood box with a heat lamp, small dehumidifier and $10 box fan... EASY SELL to the wife.

After 30 or 40 revisions and quite a bit of pestering by other woodworking friends this is what I have some up with. Good bad or indifferent.


Picking the spot to build the kiln. I chose this location for easy loading to and from a trailer.


Framing up the concrete pad and insulating it underneath. I dug the 2X8 in by hand... NOT something will be doing again under a 40 year old gravel driveway... UGH!!

 

 
FRESH MUD!!!


Kiln Cart


Had to call in reinforcements... He is a better welder but don't let him know!!!



Rails and cart finished and painted. I used tractor paint with an extremely nasty rust inhibitor primer.


Originally I was planning on 2X6 walls and roof but a friend of the family donated some used walk in freezer panels... Not ideal but, THE PRICE IS RIGHT!!! Plus for what I have in them... I can afford to tear the thing down and rebuild the walls. 


Built a roof over it with CCA plywood making the top of the kiln and a snazzy 12-12 pitched lean-to roof covered in corrugated white metal.


Installed the plenum and fans. 3X3000CFM running off DC so I can fine tune my CFM from wide open to hardly moving any air at all and can reverse the fans without opening the kiln doors.


First try for the control wiring... Smoked the power supply on the right trying to operate 2 fans off one supply. On paper it should of worked... If you decide to go down this path. Go big or go home... and don't use switching power supplies if you can keep from it. I seriously thought about setting up a 200 amp single wire alternator and spinning it with a 120 Volt motor and belt.


This picture is of the dehydrator / dehumidifier  I built mounted in the plenum (The big aluminum box in the middle) and to the left of it you can see the bottom of a 220 Volt heater. The heater is temporary until I can get a line set ran from my outside wood boiler.


Finally got everything wired up and found a box big enough for all the wiring. I am using cheepo Chinese controls until they blow up. Cant afford nice controls yet but planning on calling in a few favors to people much smarter than myself to write me a data logging program I can use on a laptop. The 3 knobs on the left side of the box control fan speed (center knob is for the fan on the dehumidifier). The left control is strictly temperature controls for the 220 heater. The controller on the right controls the compressor in the dehumidifier.The controller is very accurate (for now) and extremely sensitive but will only give me a relative humidity reading not a wet bulb reading.

I am not to sure how accurate it is but I have a slide rule left over for my days of HVAC I can use to convert relative % of humidity to wet bulb.


I tried to off myself over the weekend. It was 20 degrees outside when I kicked everything on to try it out. Had all 3 fans running full blast the heater on and the dehumidifier compressor running. I thought I would warm it up and finish sealing all my seams with silicone. By the time I came out (maybe 1-1.5 Hrs.) I was green around the gills from the silicone fumes and most of my clothing had been removed.  As a side note that much CFM pushing very dry air will wind burn your lips to the point of cracking in no time. ;)


Offline Crusarius

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Re: Snowballing wood kiln build
« Reply #1 on: October 30, 2017, 03:49:42 pm »
That is looking great. Your log cart should never fail. What size angle is that?
I knew what I thought I meant.

Offline dougan2469

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Re: Snowballing wood kiln build
« Reply #2 on: October 30, 2017, 04:00:44 pm »
3X3X3/16 I was planning on using 1/4" thick angle but had to get what the wallet would allow lol I am planning on making some aluminum powder coated stickers semi-permanently attached for the first row of lumber to ride on.

Offline Crusarius

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Re: Snowballing wood kiln build
« Reply #3 on: October 30, 2017, 04:01:39 pm »
That will still be more than you'll ever need. especially with the bracing.
I knew what I thought I meant.

Offline dougan2469

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Re: Snowballing wood kiln build
« Reply #4 on: October 30, 2017, 05:25:03 pm »
I plan on painting the interior and exterior white with the same paint used on the cart as soon as my wife stops threatening to divorce me. Should I go black exterior or do you think I would run the risk of to much heat?

I also need to cut my concrete slab where the insulation stops and figure out a way to separate the two pieces so the slab will not suck all the heat out of the kiln chamber then brace the two so they don't move.

And get power to the back of the kiln for my plainer. Then I can plain strait off the kiln cart and onto my trailer.

Am I over thinking this?

Offline YellowHammer

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Re: Snowballing wood kiln build
« Reply #5 on: October 31, 2017, 12:39:09 am »
What is the width of the chamber and what width pack of wood?  There should be enough air space in the front and rear of the pack to get good top to bottom airflow.  Too narrow a plenum and the pressure drop at the bottom layers of the pack will be too high and the air will shortcut through the top layers, resulting in uneven drying.  There are formulas to calculate optimum plenum size, but typically 18" is considered good and 12" is absolute minimum. 

The solution is to adjust the lumber pack width to allow proper airflow.
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Offline dougan2469

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Re: Snowballing wood kiln build
« Reply #6 on: October 31, 2017, 12:25:56 pm »
What is the width of the chamber and what width pack of wood? 

The solution is to adjust the lumber pack width to allow proper airflow.
THANK YOU Yellow Hammer!!!!
The ID of my kiln chamber is 54" wide 84" tall and 184" long. My wood cart is 34"X 12'6" I have 9" from the back wall to the cart and 14" to the front. I was planning on 20" of space from the wall to the cart on both sides but that changed when I got the cooler panels.

My lumber package max size would be 34" wide 57" tall and up to 150" long

I can center my cart to the doorway and get 11.5" on each side without reworking much. Could also leave the cart a bit proud of the lumber stack on both sides if need be.

What do you recommend? and whats a good guess as to how many board ft will fit in this thing when its finished?

I have 300 BF of 4/4 Honey Locust air drying in the shed at around 20% moisture content and plan on using it as my test load. Also have some Hickory and Walnut that have been air drying for a few years I can play with.

Offline YellowHammer

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Re: Snowballing wood kiln build
« Reply #7 on: October 31, 2017, 09:38:34 pm »
Sure, glad to help.
Your max load size is about 990 bdft.
11.5 inches will probably work, especially if you are using mostly air dried wood. 
baffling the ends will be very important to force air through the wood.
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Offline dougan2469

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Re: Snowballing wood kiln build
« Reply #8 on: November 06, 2017, 10:52:20 am »
I got ambitious over the weekend and got the kiln up and running to test it out. I moved the kiln cart and rails so they where centered in the chamber as YellowHammer suggested. I put the air dry honey locust in for my test batch. I don't have much money in this wood so if it turn in to future sticker material I wont be to upset. Also realized I had a little over 200 BF not 300 of Honey Locust. ::)



It was warm this weekend and threatening to rain. This is what I started with.


I was accomplishing nothing most of Sunday morning until I realized I had forgotten the baffles on my plenum. I used a piece of boat seat vinyl screwed to the bottom of my plenum and attached to an oak 2X2 that runs the full length of the kiln. This way I can simply roll the vinyl up or unroll it to accommodate each stack of lumber. It worked much better than I had expected. To get the best deal I had to buy an entire roll of vinyl so if anyone needs some I have over 300 yards left over :D



I am still need another contractor to control my heat. At 11 PM it was over 100 degrees so I had to kill the auxiliary heat for the night. With just the heat of the fans and the dehydrator running I woke up to this----> 86 degrees and 31 percent relative humidity...I am stoked!!!


And around 2-3 pints of water in my collection bucket.

Offline dougan2469

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Re: Snowballing wood kiln build
« Reply #9 on: November 06, 2017, 11:49:34 am »
Thinking about this meter but wanted to get some input before pulling the trigger. Or save my money for actual kiln controls and quit screwing around LOL?

http://www.lignomatusa.com/product/packages-mini-lignos-dxc-work/

I like the remote pin option so I can quit open my kiln door. Any other options out there in that price range that will monitor remotely?


Offline ChugiakTinkerer

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Re: Snowballing wood kiln build
« Reply #10 on: November 06, 2017, 01:05:50 pm »
Alrighty then, I now have something else to add to my when-I-retire workshop wish list!

I live in a rather cold environment, and one of the things I'm looking at for my ideal workshop is a heated slab.  I mention this because I've been looking into slabs and heat loss, and it turns out that insulation under the slab is often recommended even when the slab isn't heated.

Typical around here is at least 2" of extruded polystyrene foam panels.  If you only use the kiln occasionally it probably would have been just an extra cost with limited economic return.  But for a kiln that runs 24/7 it strikes me as being a great way to minimize heat loss through the slab.
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Offline GeneWengert-WoodDoc

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Re: Snowballing wood kiln build
« Reply #11 on: November 06, 2017, 04:50:44 pm »
An insulated floor and even insulated perimeter footing walls make sense in all climates, as concrete and wet soil conduct heat very well.  Why waste heat if the heat is costly or, in the case of solar, limitedin supply.

In a solar kiln, with a concrete floor, the insulation should be on the kiln side of the floor, as we do not want to use the floor as a heat sink, as this will mean cooler kiln temperatures.

A cold floor or wall will condense moisture, which can shorten kiln life.  There are other issues with a steam kiln, as the coldest floor temperature will limit the wet-bulb to that value.  Actually, the coldest spot anywhere will do that.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline GeneWengert-WoodDoc

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Re: Snowballing wood kiln build
« Reply #12 on: November 06, 2017, 05:02:54 pm »
Because the final moisture content must often be quite precise, remote pins often do not fill the requirement.  They do work between 28% MC and 7% MC fairly well for determining when to change conditions in the kiln.  Also, the MC values for changing do not need to be precise.

You can simplify the system by buying the probes and wires from Delmhost, but then use a portable moisture meter and have the wires come out to a central spot and then Hook the wires to the meter for each sample with clips.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline dougan2469

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Re: Snowballing wood kiln build
« Reply #13 on: November 07, 2017, 12:45:50 pm »
Have a Mini-Ligno DX/C on the way to the house. Currently I am using a "General" brand moisture meter and desperately needed a descent alternative. Anyone care to voice there opinion on remote pins and wiring potential pitfalls optimal location for pins in lumber stack ETC...

This is new to me so any tips or pointers will be greatly appreciated.

Offline GeneWengert-WoodDoc

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Re: Snowballing wood kiln build
« Reply #14 on: November 07, 2017, 04:11:47 pm »
One key is using well insulated wires.  Another is to take a reading after the kiln has been stable for a few hours; otherwise, a brief damp period can give you higher readings from surface moisture.   With wetter lumber, we use probes that have two different depths...see Delmhorst.  For drier lumber, you could even use nails.  Usually we do not drive the pins or nails to the core, but about 25% deep instead to get the average MC.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline dougan2469

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Re: Snowballing wood kiln build
« Reply #15 on: November 08, 2017, 05:11:26 pm »
Thank's for all the info Wood Doc!!!

This showed up at my door this afternoon... I love new toys  ;D



Wood Doc, After you just said you have used nails previously I feel silly asking... But... Can the insulated pins I got in this kit be used with a wire attached for an in kiln reading? Use the slide hammer to set the spacing. Then... either remove the slide hammer and replace the pins or drive the pins in with a hammer?

I could solder or braise the wire leads on if voltage drop would be a problem through clamps or alligator clips. I guess I would need to re-insulate the pins after that though.

Offline GeneWengert-WoodDoc

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Re: Snowballing wood kiln build
« Reply #16 on: November 08, 2017, 11:59:10 pm »
When drying wood, the wettest spot will be at th nd off the pins, so insulated pins are not needed.

Because of condensation in the meter or case, we usually do not take the meter into the but run the wires into an office or control room.  The resistance of wires is so small that their length is not. Rita also.  Transient currents can be an issue.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline dougan2469

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Re: Snowballing wood kiln build
« Reply #17 on: November 14, 2017, 05:36:20 pm »
My experimental load of Honeylocust was a SUCCESS!!! EMC is averaging around 5-8% after resting so out with the proof of concept and on to spending some money to automate this sucker =). I am planning on changing my capillary metering device to a TXV valve on the dehydrator this weekend. ;D

I have been looking through previous posts here at the FF and I am having a hard time finding an answer. So...

What type of probes are you all using for your wet bulb readings? Is there a probe that is readily available as prefab or should I be looking in to making my own probe out of a waterproof thermal couple and a muslin sock?

I would not be against making my own setup but would prefer something finished I can mount in the kiln and have wired up. I am currently using a 2 wire probe but if I have to I will convert to a 3 wire probe.

Any help would be greatly appreciated!!!

Offline dougan2469

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Re: Snowballing wood kiln build
« Reply #18 on: November 14, 2017, 05:49:44 pm »
Oh Yea!!!

And what type of scale is used for weighing samples? I have a refrigeration scale for weighing freon and a nice RCBS beam scale for weighing powder for making bullets.

I doubt the freon scale will be perceive enough and the black powder scale may not have enough capacity. I am putting together a wish list for X-Mas

Yet again... Any Info would be greatly appreciated.

Offline GeneWengert-WoodDoc

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Re: Snowballing wood kiln build
« Reply #19 on: November 14, 2017, 11:00:15 pm »
It would be best to have two balances...one with a maximum of around 1000 grams with resolution of 0.1 grams for the moisture section, and the other to weigh samples that can be 12 pounds or so.  You can buy these through Amazon, etc., or many kiln supply companies have such equipment.  Make sure to get a brand that can be serviced promptly...probably USA.

Example.....OHaus H5853 and NV 5101
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more