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Author Topic: Sorta solar kiln  (Read 1793 times)

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Online doc henderson

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Re: Sorta solar kiln
« Reply #20 on: September 30, 2019, 05:09:27 PM »
for heat, some just use halogen spot lights.  have you rigged a basin to catch and measure water output?  this can help you predict when the wood will be dry enough.  my ac in my shop puts out about 5 gallons a day.  aux. heat would speed up the process, but with plastic, no real way to hold the heat.  most water should be coming out overnight, with lower temps and higher RH.  if you can peak at the volume produced in am and pm, it will help confirm this.
timberking B 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 12 volt tarp motor

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Re: Sorta solar kiln
« Reply #21 on: September 30, 2019, 05:28:31 PM »
Decided to do a little testing to understand better your points.


First with the end grain (great points made earlier, thank you!) and you can see 8.1%.  This is a chunk of walnut that did not make it into the kiln (and it's hard as bloody nails!  Bent my finishing nails a few times trying to drive them into it!)



Next up on the surface and 8.5% -- guess I hadn't jammed the pins in deep enough in the past.


Finally with small finishing nails driven into the wood (after bending a few -- sheesh!) and 9.2%

OK, so that's 5/4 that was just sitting in the garage for the last few months (hmmm5 months maybe?  I'll have to try to figure that out).
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Offline OlJarhead

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Re: Sorta solar kiln
« Reply #22 on: September 30, 2019, 05:35:27 PM »
for heat, some just use halogen spot lights.  have you rigged a basin to catch and measure water output?  this can help you predict when the wood will be dry enough.  my ac in my shop puts out about 5 gallons a day.  aux. heat would speed up the process, but with plastic, no real way to hold the heat.  most water should be coming out overnight, with lower temps and higher RH.  if you can peak at the volume produced in am and pm, it will help confirm this.
Good point on the heat but I figured with 20F higher than outside air a small heater might increase it just that much more during the day and keep it above freezing at night.  Might be worth a go...I do have some insulation but would have to completely change everything.  In all honestly, I'd hoped for some normal weather with temps into the 90's....didn't happen.
Haven't gotten a hose in there yet that I can check how much I'm getting out of the wood daily.  Only option is to use the internal bucket but that poses it's own problems as I'd have to open the kiln daily which means cutting and retaping it daily....can be done, but not the best approach.
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Online doc henderson

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Re: Sorta solar kiln
« Reply #23 on: September 30, 2019, 07:02:00 PM »
looks like fun.  eventually it will get there.  you could in theory calculate the amount of water removed in gallons needed to get close to the MC you want.  or see when the volume drops off.  the heat will just speed things up, but will be lost at night due to single layer plastic.
timberking B 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 12 volt tarp motor

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Re: Sorta solar kiln
« Reply #24 on: September 30, 2019, 07:21:25 PM »
I used a TSC small forced air fan heater once, in my kiln.  It lasted awhile until the fan motor and shaft corroded and froze up and burned out the heater.  And I really mean burned it out.  Be careful.  
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Re: Sorta solar kiln
« Reply #25 on: September 30, 2019, 07:45:33 PM »
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.
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Re: Sorta solar kiln
« Reply #26 on: October 06, 2019, 02:28:16 PM »
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 )
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Re: Sorta solar kiln
« Reply #27 on: October 06, 2019, 09:26:25 PM »
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. 

Offline GeneWengert-WoodDoc

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Re: Sorta solar kiln
« Reply #28 on: October 06, 2019, 11:23:27 PM »
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

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Re: Sorta solar kiln
« Reply #29 on: October 07, 2019, 12:07:54 AM »
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.
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Re: Sorta solar kiln
« Reply #30 on: October 08, 2019, 03:03:47 PM »
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.
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Re: Sorta solar kiln
« Reply #31 on: October 08, 2019, 05:16:42 PM »
MAKING PROGRESS.   8)
timberking B 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 12 volt tarp motor

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Re: Sorta solar kiln
« Reply #32 on: October 08, 2019, 05:51:55 PM »
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

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Re: Sorta solar kiln
« Reply #33 on: October 08, 2019, 06:08:00 PM »
For precision, you need correct the reading for species. Temperature is a factor also. Just throwing it out there . . .
HM126

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Re: Sorta solar kiln
« Reply #34 on: October 09, 2019, 08:52:28 PM »
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.
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Re: Sorta solar kiln
« Reply #35 on: October 11, 2019, 09:42:21 AM »
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?
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Re: Sorta solar kiln
« Reply #36 on: October 11, 2019, 07:07:26 PM »
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.
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Re: Sorta solar kiln
« Reply #37 on: October 12, 2019, 02:57:52 PM »
 

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 :)
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Re: Sorta solar kiln
« Reply #38 on: October 12, 2019, 02:59:31 PM »
lots of character just like the harvester!!!    8) 8) 8) :)
timberking B 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 12 volt tarp motor

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Re: Sorta solar kiln
« Reply #39 on: October 12, 2019, 03:04:11 PM »
Yup, pretty nice figure (the board, not me) :D ;D

Added some comments

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