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Sorta solar kiln

Started by OlJarhead, September 23, 2019, 12:37:22 PM

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OlJarhead

The real fun begins when my router slabbing jig and new 3.25hp Makita router shows up with 3" slabbing bit! :D  I'll have to make a table for it and get it set up for the first slab...and figure out how to secure the slab to the table....

But all that after the kiln/drying gets the wood to an decent level.
2016 LT40HD26 and Mahindra 5010 W/FEL WM Hundred Thousand BF Club Member

OlJarhead

Did some changing in the 'kiln' today which I really ought to call drying tent ;)

First I moved the fan to the top of the stack in the hope that it will move air around the tent better and push warm air down etc.  Then I moved a small 1500 watt ceramic heater into the tent on the opposite end of the dehumidifier.  I had contemplated this as it's been down to freezing at night and only in the 60's during the day and I thought if I could raise temps to the 80's or better on sunny but cold days it might help.  My wife actually commented that the camper was 80F inside with this heater on fairly low and that it might boost the temp in the 'kiln'...so why not?

Then I drove some finishing nails into the wood and wrapped some wire on them (I have yet to pick up any clips) and stuck the wire out of the tent so I could check more often and without opening the tent.  Lastly I stuck the temp logger in and checked outside air temps (52F) before sealing the tent.  This way I can see what the low temp was when I started and track daily outside air temps for a week and see what happens with the heater in there.



Checked a pice on top of the pile and it was at 12.7% about 1" into a 2.25" piece.




Jammed the pins into a 1.25" piece and saw this



I should recheck this one as it seems a tad low.  It's on the bottom of the pile and a 2.25" piece with finishing nails driven about 1" into it.



Original test piece measuring 12.2% vs the original 12.7%.  Not sure why that is unless the length of the wire has something to do with it.

Still, I'm thinking at this MC I could if needed, flatten these out on my new router jig (I bought the The Stone Coat Countertop Slab Jig and a 3 1/4hp Makita router for that purpose :D )
2016 LT40HD26 and Mahindra 5010 W/FEL WM Hundred Thousand BF Club Member

Nebraska

Thanks for doing this thread, I'm a little behind you in the process, I've got a few slabs air drying for the time being. A solar kiln is on next summers to do list. A router sled will be a good December/January project when it's too cold to do much outside. I probably won't run a bit bigger than an inch and a half, or so at least til I  manage to free the magic  smoke in my old craftsman.
I hope you get healed up miss the milling thread. 

GeneWengert-WoodDoc

It is important to take the first reading that you see rather than waiting for a ten seconds or longer.  Do not apply the voltage for a long time.

From time to time, disconnect the wires from the nails and see of you get a reading...any reading means that the wires are leaking current.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

OlJarhead

Thanks guys.  I hope to get back to milling again myself!  I do have one job I've agreed to do and hope the weather allows it since I was snowed out last time.  A new shot in the elbow may help (had a special one a few days ago)...now we wait.

Thanks for the note on taking readings and the wire.  I notices the readings drop for a bit then stabilize.  Usually don't drop more than about 0.5 though.  So perhaps the 12.7% reading is the accurate one and the 12.2% was me fiddling too long trying to take a pic and holding the voltage on.

Going to drop to 25F in a couple nights so probably will have to kill the heat and dehumidifier since the water will free in the hose anyway....either that or disconnect the hose and see what happens.
2016 LT40HD26 and Mahindra 5010 W/FEL WM Hundred Thousand BF Club Member

OlJarhead

Checked both today and saw 12.4% on the one that was 12.7% before and 10.1% on the one that read 9.7%

I'm guessing it doesn't mean much other than a couple days makes little difference. 

I do however, plan to move it all inside soon and will have to decide how to drive it down further then.  After all, it's getting VERY cold in the next couple days and no likelihood of any good warm weather left which this type of contraption really needs I think (at least to get it hot enough inside to evaporate the moisture out of the wood).

So, I'll move it inside and once I haven arrange the room will set it in a smaller box with the dehumidifier and fan and a heat source and see what happens then.

But I may flatten some of it out before trying to push it down further.
2016 LT40HD26 and Mahindra 5010 W/FEL WM Hundred Thousand BF Club Member

doc henderson

Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

GeneWengert-WoodDoc

It is common to have plus or minus 1/2% MC due to temperature, loss of contact with a nail, different depths, etc.

Regarding nails used as probes, predrill a hole that is a tiny bit smaller in diameter than the pin so the pin is snug.  Drill the hole about 1/4" shallower than the desired depth. using a sharp drill bit.  Then pound the nail in the last 1/4" of the way into fresh, undrilled wood.  Note that the desired depth for the average MC is usually 1/4 of the thickness, so you would not predrill 4/4 or thinner, and the predrill for 5/4 would be no more than 1/16"; for 8/4, predrill 1/4" deep and then pound the nail into the 1/4" deep hole and then 1/4" solid wood; etc.

Remember that end grain dries about 20x faster than face grain, so end grain readings are not too useful for estimating the MC of the entire piece.

P.S.  VERY IMPORTANT.  Remember to pull the nails out BEFORE running across the planer, jointer, router, etc.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

btulloh

For precision, you need correct the reading for species. Temperature is a factor also. Just throwing it out there . . .
HM126

OlJarhead

Hmmmm.....took readings and saw over 14% on the one that was showing 12.4% last and over 11% on the one reading 10% last....I'm wondering if this could be because I put the heater in there and the fan on top of the stack?

Shut it all down due to the cold coming tonight (22F for a low) and not wanting to pump 1500watts non stop into the kiln and have the dehumidifier freeze up.  Pulled the temp logger and saw that the little heater was keeping things VERY warm indeed.  Despite days in the low 60's the kiln was reaching as much at 110F during the day and remaining in the high 50's or low 60's at night.  Humidity at night was rising to just above 40% and at the hottest below 28%.

I'm thinking that might actually have been working pretty well for me (and I was seeing more water escape the line than before) but am also thinking it's time to bring it inside and perhaps have more warmth longer.
2016 LT40HD26 and Mahindra 5010 W/FEL WM Hundred Thousand BF Club Member

OlJarhead

Those readings were early in the morning, yesterday after a pretty good day of warming up the kiln (with sunlight only) the readings were back to 12.4% and 9.x% (can't remember that one and didn't record).

I removed the fan, heater and dehumidifier from the box and opened it up so any moisture could escape and plan to move the wood inside this weekend (have to move it anyway because I have a big shed coming and need the room for the shed to travel to it's new home).

My plan now is to reconstruct the box in my garage but with insulation and a heat source.  My thought is to use a couple 500 watt halogens to heat the box and to keep the box small as possible.  Here are some questions I have:

1.  Would it be worth planing down the lumber to flatten it out before re-stacking and drying it more?  I had a lot of movement in some of it during the air drying (my guess is it dried too fast in this dry climate).
2.  Would two of those halogens heat up a box hot enough (box would be approx 4x4x11).
3.  Would it be best to put the fan facing down and drive the air down onto the pile instead of on the end opposite the dehumidifier?  I'd assume I'd need to place a baffle of some sort on top of the wood so the heat is driven to the sides and not the top pieces.

My thought is to place two halogens on cinder blocks at one end of the box about two feet from the end of the stack and place a baffle in front of the wood with an air gap to reduce hot spotting the end of the wood, then place the dehumidifier at the other end of the box so the wood is in the middle.  With the fan hung above the wood driving the heat down around the wood I might get the best circulation.

Once running I could turn off the heat at night and allow some cooling so the DH could do it's thing perhaps and I'd have to watch temps to ensure I don't get hotter then I want (I'm thinking 140F ought to do it but am uncertain as I recently read 150F is better for killing bugs (which I have no idea if I have or not).

Thoughts?
2016 LT40HD26 and Mahindra 5010 W/FEL WM Hundred Thousand BF Club Member

GeneWengert-WoodDoc

Moisture readings taken before noon are often higher than afternoon readings as the conditions in the kiln are cooler and more humid from perhaps midnight to 6AM and so the shell picks up a little moisture, that is evaporated in a few hours.  The higher moisture in the shell affects readings taken with nails or any uninsulated probes.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

OlJarhead

 

I had a pretty badly warped piece of the walnut (5/4) that started splitting and cupping and doing all manner of silly things before I got all the lumber stacked and stickered.  So, that piece I left in the garage and eventually split it in half, then split it the other direction (so quartered) and finally cut it into roughly 12" pieces that I thought I could flatted in the planer.  I then did just that and finally after cutting some a little more, tested MC and found 8% in the middle of the cut off one and 8% straight down into the face.  Funny that, but then the stuff I had outside was measuring around 6% (the 5/4 stuff) so the difference is there.

Anyway, I was able to flatten these in the planer and while they might not be very big at only 12" long they are all usable somewhere :D  I've restacked and stickered the now flattened pieces so they can maybe dry more but I also now feel confident that doing the same with all the big stuff will be better before final drying :)
2016 LT40HD26 and Mahindra 5010 W/FEL WM Hundred Thousand BF Club Member

doc henderson

lots of character just like the harvester!!!    8) 8) 8) :)
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

OlJarhead

Yup, pretty nice figure (the board, not me) :D ;D

Added some comments

2016 LT40HD26 and Mahindra 5010 W/FEL WM Hundred Thousand BF Club Member

doc henderson

that much figure is going to warp and create tension with drying in any wood.  very nice!
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

OlJarhead

Quote from: doc henderson on October 12, 2019, 03:08:32 PM
that much figure is going to warp and create tension with drying in any wood.  very nice!
That I did not know!  It makes sense and explains the challenges I've had with this wood.  I figured it was just tension in the tree/logs that I was fighting and perhaps drying too fast in our high desert climate.
2016 LT40HD26 and Mahindra 5010 W/FEL WM Hundred Thousand BF Club Member

doc henderson

after dry, may have to joint one side, then plane the other.  the plastic is the mechanism by which you try to control the humidity and rate of drying.  more dry is not always "more better"  lol.  you can allow for more planning in thick slabs, and or just plane until you have erased the defects in the wood.  that has a ton of grain running all over from a branch.  not gonna be straight no matter what you do, but sure is interesting and pretty.  just like you @OlJarhead .   :) :) :) ;)
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

GeneWengert-WoodDoc

If you would like a technical explanation...
Wood is made mainly with woody cells (hollow, miniature, skinny tubes with length 100 times the diameter) that run vertically in the tree and carry liquids to the leaves.  These cells shrink and swell in diameter (thickness and width of lumber) as the moisture changes between 0% MC to around 30% MC.  Their length does not change an appreciable amount usually.

When you have swirly grain, it means that the cells (sometimes called the grain) are no longer vertical in the tree but run different directions.  Along with this swirly orientation, it means that the shrinkage and swelling of the cells in diameter cause a particular swirly region to have shrinkage and swelling along the lumber's length.  Different grain angles mean different movement characteristics- -warp- -within a piece of wood.  

The bottom line is that beautiful swirly grain in lumber means warp variations are likely.  Control is extremely difficult or impossible.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

OlJarhead

Thanks Guys.  My plan, with luck, is to plane all of what I have down until it's flat :D  I did manage to work the small pieces I have down to 'pretty darn' flat ;) but those were tests.  Now they can wait for use as bow ties or whatever I can find for them being so small, but the big stuff I will plane down with the router sled.  I can remove about 3/4" from them, maybe a full inch if needed.  Then, if that's not enough I'll have to cut them smaller but I do have pieces that remained fairly flat so we shall see.
2016 LT40HD26 and Mahindra 5010 W/FEL WM Hundred Thousand BF Club Member

alan gage

Quote from: OlJarhead on October 14, 2019, 09:36:45 AMMy plan, with luck, is to plane all of what I have down until it's flat


Just remember that you can't plane bow or twist out of a board. You can make it thinner but it will still be bowed and/or twisted. Sometimes it's even hard to plan cup out of a board when the rollers keep pressing it flat.

Alan
Timberking B-16, a few chainsaws from small to large, and a Bobcat 873 Skidloader.

OlJarhead

It's been a while!  I've cleaned out the shop after getting a new storage shed to give me a place to put crap I don't want in the shop ;) and got my router planing jig and table set up.  Then finally started planing.

The walnut is down about 11% and as I mentioned before I decided to plan it flat and continue the drying from here (and possibly using some that won't need to be down at 8% or better).


 

 

 

 
It's taken some work to get the jig set up well and the right bag on the vac filter with the right dust mask etc etc but at this point most of the fine dust is going into the vacuum and not past my cheap mask (because I got a better one too) and some of these have a lot of movement and require more material to be removed but so far this is working.

Now let's hope they stay flat!  Only three done so far but I'm getting the hang of it.
2016 LT40HD26 and Mahindra 5010 W/FEL WM Hundred Thousand BF Club Member

doc henderson

@OlJarhead the  jig will get it flat and at low MC hope it stays that way.  what @alan gage is saying is that running it through a traditional planer will make both side follow the other but may not take the twist out.  if your slabs are fastened or shimmed so they cannot move, the top side should be flat when done.  then if you had a big enough planer it would work fine for the second side.  or just flip it over and use your router sled again on the second side.  by definition you are really jointing the surface with a sled, not planning which is i think the point Alan was making.  looking good.  lots of hard work.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

OlJarhead

Aha!

That makes sense, thanks!  I shim the underside, 'joint/plane' the top until it will sit flat and flip it over and do it all over again.  Once both sides will sit flat without shimming I then go back and forth doing enough on one side to make a difference, then the same on the other...sorta like milling.  The idea being to limit movement or 'mill' it out.  I had not noticed any though so decided to make one side completely flat and then flip and see how that goes.  So far so good.
2016 LT40HD26 and Mahindra 5010 W/FEL WM Hundred Thousand BF Club Member

doc henderson

yes, just do one side until flat with shims under it, when you flip it over, it should sit flat without shims. and then do the second side.  
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

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