The Forestry Forum

Hi all.
   This thread may be a bit premature, but I'm excited about a solar drying kiln that I'm about to start on. The design will be based on pineywoods design. His solar kiln heats up during the day to 160 degrees and cools down at night. This allows the wood to dry with less wood stress, avoiding splitting.
   I plan on making the kiln about 5' wide x 18' long, and bolt on an axle and tube for a hitch that my Norwood lumbermate uses so that I can tow it around the yard. I also plan to have the door panels made in sections that are easy to remove...and possibly hinge one on the end for easy in and out access during the drying process.
  I cut out all the pieces last week out of SYP so it can dry for about a month before I start the assembly. The only big expense will be the translucient panels for the top. I'll post start to finish pictures when I get started in a few weeks. I'm pumped!

If it turns out as well as did all of those doors that you made, it should be pretty nice.

I am really interested in this as well, so I look forward to your experience.  I saw the Pineywoods design, and it is different in how the solar collector is designed (say versus the Virginia Tech design), so that might explain how he gets a much higher temp than others can achieve.

Planman1954 , I plan on starting my kiln in about 30 days. Have had loblolly pine cut for about 3 weeks. Mine will be 6' x 12'. Have bought and recieved 2 gable vent fans for air circulation. Like you said the plastic covering isnt cheap. About $28.oo at Lowes for 12' x 2'. The treated plywood isnt exactly cheap for the interior either. What kind of siding are planning on doing? Good luck and do some good photos as you go. bg

10-4 Bill.
Here's a couple of pics of the lumber I'll use:


(https://forestryforum.com/gallery/albums/userpics/19339/3018/045.jpg)

(https://forestryforum.com/gallery/albums/userpics/19339/3018/044.jpg)
The top pic starting from the right are some 6"x6" cross members for the base beams. Next is 3"x6" stock that I will laminate with bolts and large nails to make the long 6"x6" support beam. Next are 2x4"s for the floor joists, top and bottom plates, and upper rafters. Next are 1"x12"s for the floor. (I wish I had cut them 3/4" thick since they will bear no weight...only keep air in.) Finally, sort of out of the picture, are some 3/8"x8" boards for the interior walls, and 8" lap siding for the exterior. The bottom pic is some 2x4s for the walls, some 1x4s for the door frames, as well as some more siding and interior boards. I think you'll see it all come together when I start the build around the middle of May. Take care.

Planman came visiting and measured, sketched and looked over my kiln. He got it, this thing is nothing but a chicken coop with a plastic roof . His should be an improvement over the original in several ways. Added length will allow drying 16 ft lumber. I welded up my door frames out of 1 inch square tubing, he has figured out a way to make doors from free wood. Planman's location is just about ideal from a solar standpoint, top of a bare hill with un-obstructed view to the south. His place is about 4 miles from me, so I plan to make a pest of myself when he starts construction.  ;D

pineywoods , He may very well put a hammer in your hands so you may not be the pest of the neighborhood that you claim to be. I am going to pick up some treated plywood today for the interior, 1/2" @ $15.00 per sheet.
Planman1954, looks like you have good start on the lumber. bg

Maybe the Grouchy Old Men will make an appearance  ;D.

Are you using the attic vent fans only. I picked up 3-12" all metal fans today at Orshlens and they are 3 speed and cost 24.99 each. I have one in my shop that has ran for years at 8 hrs a day. I wondered if anyone has tried them in a kiln where the temp. will be higher. They also carry a 16" , 3 speed for 29.99 each.

Fil-Dill:
I plan on using 1 or 2 simple box fans mounted facing down, just as pineywoods has done. It works well. If one dies, I'll get another. They're cheap!

How do you get the temp. up to 160 degrees during the day ?
I would to know more about the pineywoods kiln system.

Do you think I can get by with vinyle siding on the outside? It is grey and I have alot of it around.

Vinyl, wood, old roofing metal, construction board, plywood etc. Just about anything will be fine for siding. It's nothing but a small building with a south-facing clear plastic roof. What's different from other designs is the amount and placement of the metal collector panels. Wood is a lousy solar collector. What you need is metal painted flat black. fastening the metal to the bottom of the rafters has 2 advantages. 1. more room to install more collector, about 50% more. 1.. The collector is perpendicular to the suns rays which ups the effeciency considerably. There's pics and drawings in my photo gallery.

Metal collector is nice but not needed. I havent even finished mine and without the doors being painted black yet(about half the sunlight hits them) it already hits 160 sitting in good sun. As long as light isnt reflected back out anything will soak up the same amount of heat. The main heat loss in a solar kiln is the plastic/glass for the sun to come in. That's why doubling up on the glazing is suggested.

For mine to keep the price super cheap I used a green house plastic rated for 5 years. PVC corrugated panels yellow the same, so unless you use glass or fork up for polycarbonate the 6mill greenhouse plastic works just as good.

I've spent several years in DIY solar projects and my solar heating panels at home use a furnace filter for the collector, which actually works better than the metal collector I originally built.

Planman, have fun. It may get frustrating at times since it's a large kiln but it's always worth it. I have to tweak my doors, finish coating, add the fans, and I'll be done with mine.

Problems I ran into:
Trying to fix the doors too tightly. Put a door jam in and move along. The kiln will tweak back and forth with the weight of the huge doors.
Tar. I will never use tar again just because it's so nasty, takes FOREVER to dry, and gets nice an soft again every time it gets hot for a long time. I'd rather spend the money on a elastomeric coating and either tent it black or paint over top. At least then I can spray it on.

Hey pyro....nice post. How bout a photo of your kiln? Also, i plan on doing the access area a little different than just large doors. You'll see...if I can figure out what I'm doing!!  I will post photos as I go along. Pineywoods design dries wood in about 2 to 3 weeks. What do you think yours will do? Again..thanks.

Piney,

Have you dried much oak?  Would 160 degree temps dry the oak too fast and lead to case hardening and honeycomb?  I know pine can take it, but I am concerned about hardwood and oak especially as I cut 98% hardwood.

WDH that 160 deg figure is just a bit misleading. It does get that hot on a good sunny day, but it don't stay that hot. The average temp over a 24 hour period will be much less. Cools off to close to outside temp at night.How much it cools off is highly dependent on species and the size of the stack.  That allows the wood to stabilize and moisture to migrate slowly to the surface. I ran a batch of 4/4 air dried pin oak (really water oak) through mine for about a month. Moisture meter said 6%. I made  tongue and groove flooring from it, nailed it down to a plywood base, NO shrinkage. On the other hand, some 14 inch wide pine wall paneling did shrink a little after I nailed it up.  When it comes to solar kilns, published drying temps and schedules are useless. One stack may dry ok in a month, the next similiar stack may take twice that long. There are just too many variables.

Planman, I don't know about dry time since that varies a lot with load size, location, weather, etc. Looking seriously forward to putting a stack in it though. I'll try to get a couple pics up at work as my computer busted. Look forward to seeing yours.

Piney, do you adjust your vents much during loads or for different species? Hopefully my first bat h of 1000ft 4/4 maple turns out without any issues.

Quote from: pyrocasto on April 18, 2011, 10:12:49 PM


Piney, do you adjust your vents much during loads or for different species? Hopefully my first bat h of 1000ft 4/4 maple turns out without any issues.

There are no vents on either of my kilns. I use a cheap room de-humidifier running at night to take the moisture out.

Plansman,we used box fans,at $10 each than,in our greenhouse for 3 years.They would run steady,24/7  from Feb-March until late June.Never burned one out.I told the wife,they won't last long. Sure was wrong on that.They are stored in the old farm house now.

Will you paint the interior black and if so, what with. I was wondering if the foundation sealer, softens up during the high temps. Flat black paint doesn't seem to be to common in larger amounts.

I'm probably not going to paint the interior at all...except for the top of the galv. metal nailed to the bottom of the rafters. You'll get the idea when you see the progression of the construction...about 2 weeks away!
I do plan on staining the outside though to protect the wood from the elements.

Fil-Dill, I priced some flat black paint made by Anchor Paint Monday and it was $26.00 per gal. Its made in Tulsa, Ok. You can buy directly from them. I bet they sell it also in 5 gal. buckets. The gal. I priced was at a metal selling company. Could be cheaper in Tulsa.
  Set some concrete blocks today to support the four floor beams untill the rain put a stop to that. Hope to finish that tomorrow.
   Plansman, what is going to be the heigth on the front side of your Kiln?

Probably about 8'. I'm not sure of the exact dimensions. The height will be determined by the length of the top plastic panels that I'll buy. I'll determine the length of the rafters first set on a 45 degree angle, then the finished width of the thing (around 5' or so.) It's only 5' wide since I'm putting an axle on the bottom to move it around. After I draw a section out full size on the floor of the kiln, I can then judge how high the thing will end up. Like I said, the front (or tall side) will probably be about 8' high, and the back side about 4'. I guess we'll all see when I get to it...been busy on some plans this week, and haven't been outside much.

I started mine today. Got the blocks and support beams set. Constructed the bottom and will flip it tomorrow, insulate and add flooring. I believe I will go with 3' front or short side and do the back side however it comes out at a 45. Mine is 6' x 12'. I do a lot of figuring on the fly in the dirt. Didnt do a sketch, just build as you see it is my moto.

Thanks for the info Bill. I have my subfloor on, but am trying to figure out how to post pics. Mine is a copy of the Woodmagazine kiln. It is 8'X 18'.

Fil-Dill, You bet, pretty good size kiln. Just keep working on the photo thing. bg

Hello everybody.

Today I got started on rounding up some things to begin construction of the solar dry kiln. Bought some nails, ordered the clear plastic panels for the top, and went by pineywoods house. He did some metal working for me which will allow me to have a trailer base on the solar kiln so that I can move it around the yard.
I pulled an axle off of a wooden teardrop trailer project that I had abandoned a few years ago. It's on the left in the photo. The axle had been mounted under the leaf springs, so we removed the axle and put it on top of the leaf springs to get the kiln closer to the ground. The old bolts were tough, but with a little homemade bolt penetrator and pineywoods impact wrench, it didn't take too long! We also had to install some 7" long bolts for the new 6" deep frame.



(https://forestryforum.com/gallery/albums/userpics/19339/3018/002%7E0.jpg)
The next thing we did was make a bracket out of some leftover steel. I'm going to bolt it onto the 6x6 base of the kiln over a slot cut out to accept the Norwood trailer attachment that's on the right in the picture above. Below is a photo of the bracket. It's 3" stock with 2 pieces 11" long welded to the top. Once the thing is in place, you'll get the idea of the configuration.



(https://forestryforum.com/gallery/albums/userpics/19339/3018/001%7E0.jpg)

Hopefully Monday I'll post some pictures of the base assembly. Hope ya'll have a great weekend.

Today I got a few free hours to start work on assembly of the base of the kiln. Remember that I'm making the base as a trailer to move around. I started by roughly laying out the side and end beams in order to level the 6 piers. The height of the beams from the ground is about 18" to allow me to install the wheels when I get ready to move the kiln around. The side beams will be two 3"x6" beams bolted together to get the length that I need of 18':


(https://forestryforum.com/gallery/albums/userpics/19339/3018/004%7E0.jpg)
Here's a closeup of the axle bolted to the side beam:


(https://forestryforum.com/gallery/albums/userpics/19339/3018/002%7E1.jpg)
Here's an end view of the progress I made today. There's still some more cross beams to fit and install, as well as some end pieces of 3"x6".



(https://forestryforum.com/gallery/albums/userpics/19339/3018/001%7E1.jpg)

I'll hopefully be back on it this Thursday. Take care.

I beleive jason from wi built one on a wagon but I dont remember seeing pictures of it

Planman1954, glad that you have got started. I have my south and north side up. Cut the rafters yesterday is all. The rain kept me from getting more done.
Cleaned up the boat and got fishing tackle ready to head to Lake Fork, Tx in the morning to do a few days fishing.
Excited to get kiln finished and see if it will suck the moisture out of some lumber. bg

here's something ?   http://milwaukee.craigslist.org/mat/2353938473.html

Aww...I thought my idea was original!  :) Anyway, I think mine will be a little closer to the ground and heavy duty than that one. I hope to be able to get 16' material in the thing. I plan on continuing working on the base in the morning. After the as-sem-bull-ly (as Norm Abram says) I plan on spray painting the base beams to protect them a little from moisture.

OK. I worked all day and completed the base. It was a job for one fellow! I can barely type. Anyway, I got the sides and middle supports nailed and bolted together, and the front trailer hitch bracket installed (Thanks pineywoods. Looks like it might work well.) Here's a photo of the completed base:


(https://forestryforum.com/gallery/albums/userpics/19339/3018/001%7E2.jpg)
I used 4 cans of flat black spray paint on all sides (and the entire bottom) of the frame. The next step is to put on the 2x4x16" oc floor joists. I plan on laying felt over the joists before applying the 1" floor boards. That will happen tomorrow or the next day. Stay tuned.

More progress today:

First I nailed on the floor joists...2x4x16" oc:

(https://forestryforum.com/gallery/albums/userpics/19339/3018/003%7E1.jpg)

Next I laid on a layer of felt to prevent air leakage through the floor:


(https://forestryforum.com/gallery/albums/userpics/19339/3018/002%7E2.jpg)

And finally, the finished floor:


(https://forestryforum.com/gallery/albums/userpics/19339/3018/001%7E3.jpg)

Next I'll lay out a section of the kiln on the floor full size so that I can determine the correct length and pitch of the rafters.

Planman- looks fantastic and has got me itching to build one also.... as soon as I finish up a few little projects around the farm, I'll get started... in maybe a year or two.  Isn't it frustrating that "things take time?"  Friend of mine said once: TTT is the thing to keep in the back of your mind so you don't get frustrated, but man, you're going full steam on that kiln!  Love the pictures- proves the old statement about a picture being worth a thousand words... :)

Lj

Finally I have some time to work on the kiln tomorrow. I started on the long box beam that goes over the opening this evening, sort of a jump start on tomorrow. I used 3 pounds of nails on one side. Guess I'll start the day tomorrow at the store to buy about 4 pounds more. This is how many nails this one beam requires! Here's the link to the design I found on the internet:

http://www.apawood.org/pdfs/managed/Z416.pdf

(UPDATE:  OK...it looks like this link doesn't work anymore unless you sign up to become a member) So...the beam is made from 2 18' 2x4's on the top and bottom with 2x4 blocks vertically. The blocks have to be in an exact position, so I guess you need to find another source for the spacing. Plywood is then nailed to both sides using a staggered tight nailing pattern about 1 1/2" apart as seen in the photos.

I'll take photos of it in the morning and hopefully post tomorrow's progress this weekend.Take care.

Ok...here's photos from today's progress. First, I made the beam using the design of the website I showed before:


(https://forestryforum.com/gallery/albums/userpics/19339/3018/004%7E1.jpg)

(https://forestryforum.com/gallery/albums/userpics/19339/3018/005.jpg)
You get an idea of the nailing pattern required. It took me an hour just to nail one side of the 17'-2" long beam. It is also insulated with batt insulation.
Here's the first wall going up:


(https://forestryforum.com/gallery/albums/userpics/19339/3018/003%7E2.jpg)
Here's the beam set in place. I did it myself by first lifting it onto some sawhorses set up on the floor, and then lifted one end up onto the supporting cripple studs, and then the other. I would not recommend doing this alone again. Get help.


(https://forestryforum.com/gallery/albums/userpics/19339/3018/002%7E3.jpg)


(https://forestryforum.com/gallery/albums/userpics/19339/3018/001%7E4.jpg)
The last photo is showing end of the day progress. I set one rafter on...it fit great! take care.

Once you get this one perfected, you can build another one (for me ;D).

WDH , maybe you didn't notice, but it's got wheels and a hitch  ;D

re, lifting the big beam...DanG knucklehead, I'm 4 miles away with a tractor with forks.

Looking good, looks like about the same dimensions as mine except for the extra length, that fixes one of my mistakes..

Planman1954, looking good. Your progressing along real well. Are the goats doing quality control checks? bg

If it's anything new they have to check it out if the goats are like the ones we had.   ;D  I did some work on the goat barn with them in there. They had to be right by my side,checking out my nails and tools. I finally had to lock them out to get anything done in a reasonable amount of time.

Have not posted much but wanted to share my use of a green house for solar drying. Purchased a greenhouse from Harbor freight fo $ 600.00 for my Mom ,  who moved in with my family during the winter of 2009 . She enjoyed flowers so I was trying to give her someplace to do it in the cold . Well she ended up passing away in about a month after erecting it . It sat for a year and I had already installed shelves and tables so alot of room was taken .The dimensions are 10 wide and 12 long. I stacked the pine cants onto the benchs and stickered. I set up boiler temp. gauges cause the cheap ones kept breaking. There are two vents on top always open and I was getting readings of !40 with them open . Have not closed them to get additional temps yet. But its nice to see that its still has a purpose even in the spring with the plants gone. Another note my Mom before passing suggested I get the sawmill .51 years old and she could still make me feal like I was 12. I purchased a Logmaster Lm-1 made here in Texas . The joy I get from making lumber is unnatural . I have a big smile on my face the entire time I making saw dust. Thanks guys for all your posts and teaching me so much lurking on your site . I hope I didn't ramble to much.

Sorry about the loss of your mother.  Its good to see you enjoying the greenhouse/solar kiln so much. That is inspiring.

And here I thought Planman was getting the goats used to being inside so we he fired it up for it's trial run, they would be there... and you get the idea: slow cooked at 160?  Should work pretty good- nice and tender, smokey flavor.  This thread has been entirely too long without mention of food.

So after we haul your beautiful kiln over to my place (I'm volunteering) for a first full load of wood to dry, do I have to block it up front and back to take the load off the wheels?  Just checking in case it magically shows up here one day- that trailer hitch looks to be exactly the size of the ball on my truck.   ;D

Why don't I have a solar kiln yet?  Oh, yeah, because I get distracted by other things to do...

Great job keeping us up to date on your progress, planman- thanks.

Lj

I finished the back wall today...put the siding on the outside over felt...then insulated the inside wall...then put 3/8" thick boards on the inside to hold the insulation in place.


(https://forestryforum.com/gallery/albums/userpics/19339/3018/001%7E5.jpg)

(https://forestryforum.com/gallery/albums/userpics/19339/3018/002%7E4.jpg)
The last picture is me beginning to put insulation in the rear wall. More pics later.

Nice progress on Kiln . Great workmanship . I understand about your Goats . My wife is a Nubian Breeder . Milk and soap making , worth more than a meal .

  If you were to put sheet metal under the rafters like on Piney's, you wouldn't really need to paint the inside black would you? Seems like you could just sheet it with about anything in that case.  Or would the moisture cause waferboard or plywood to de-laminate?

Handy Andy:

You got it. The idea is to create a collector system between the rafter space with openings at the top and bottom for air to flow around the lumber. Therefore the light will not penetrate into the kiln itself...only a small amount maybe. So there is no need to have the inside black...it makes no difference. The metal is necessary to retain heat generated by the black paint. Check out a piece of metal that is black lying in the sun vs. a piece of wood painted black. The metal will burn you...the wood won't. So metal will be used painted black facing up under the rafters. You'll see how simple it is when I get to that point. I wish that I could have done it all in a few days straight...but I have to keep my income going with my REAL job...designing houses.
Oh, and I'll be using a dehumidifier set on the floor for a few days to take the moisture out of the air. This will prevent condensation under the panels. Pineywoods and I had a discussion about condensation, and I decided not to try to deal with it flowing downhill under the panels...just let the dehumidifier catch most of it.
Take care.

Finally got some time to work on the kiln today. I got the exterior siding finished on the 2 ends. Then I ran wire for 2 outlets. One outlet is above the beam for the two upper fans I'll install, and one is on the end to plug in a dehumidifier. The inlet box is below the box on the far end wall. Here's a photo of the 2 plugs and inlet box:


(https://forestryforum.com/gallery/albums/userpics/19339/3018/003%7E3.jpg)

Here's a photo of the inlet male 110 v. plug on the end. I can run an extension cord from my house and plug in the kiln for operation. I'll put a weatherproof cover over it after I stain the kiln.


(https://forestryforum.com/gallery/albums/userpics/19339/3018/001%7E6.jpg)
Here's a photo of insulation being put in one end. Later I put 3/8" thick boards on the interior to hold the insulation in place:


(https://forestryforum.com/gallery/albums/userpics/19339/3018/002%7E5.jpg)

  I also got the interior boards on 1 end wall finished, started on the other until the heat made me stop. I started at 6 am and stopped at 1 pm. I hope to get back on it this week. Take care.

Planman1954, your going to get there soon. This kind of weather sure makes a fellow seek cooler ground. Have you decided on what kind and size of DH you are going to use? bg

Hi Bill. I'll probably get the same model as pineywoods. He got his at sears I think.

Got to work this morning for a couple of hours. I finished the siding on the inside of the kiln and went ahead and put all the rafters on:


(https://forestryforum.com/gallery/albums/userpics/19339/3018/002%7E6.jpg)
Then I cut the old metal roofing panels 5' long and painted one side black:


(https://forestryforum.com/gallery/albums/userpics/19339/3018/001%7E7.jpg)
I cut it to length with a circular saw using a fine tooth blade. It worked great. Use goggles. I bought a couple of fans at Walmart to mount in the top, but took them back this evening after pineywoods said I needed metal blades. The ones I bought had plastic blades. They'll melt with the heat. Anyway, I'll have to find a couple with metal blades tomorrow. I also bought the clear corrugated panels for the top at home depot this weekend. The panels ran about $150.00 with the mounting screws. That's all for now. (UPDATE: I found an 18" fan with metal blades at Lowes for $30.00...so I bought two.)

Finally had some time this morning to get back on the kiln. I stripped the top with 2x4's for the plastic panels, and stained the outside 3 sides. I plan on putting the top panels on in the morning. I'll take a photo and post it tomorrow. Take care.

Here's some pictures of the top installed this morning:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/001%7E8.jpg)

(https://forestryforum.com/gallery/albums/userpics/19339/3018/002%7E7.jpg)

I won't be able to work on the kiln until after the holidays. Happy 4th everybody!

I will go ahead and place the order for mine now.  I prefer the forest green stain  :D.

Lookin good on the kiln. You are almost there. Try and keep cool on the 4th. bg

Planman: looks great; in fact, looks too good to be just an old kiln. You sure this isn't turning into a Southern sauna?  Like we need more heat and humidity as it is.   :D

Lj

LJ,

I have an outside sauna.  Anywhere outside  :D.

Planman,just doing a follow up on your kiln. Have you been able to finish it up lately? Havent heard much from you for a while. bg

OK...back to work on the kiln, after a long hot summer. Sorry for the long delay, but had some other things to attend to. The Kiln is now completed, and ready for a test run.

After attaching the top plastic panels and completing the wiring for the fans and dehumidifier plug, I ran some blocking between the front beam and rafters and made a framed box for the two fans to rest:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-09-05_12-56-51_419.jpg)

After the fans were set in place, I began installing the metal panels under the rafters. Remember, the metal pieces are centered between the top and bottom of the rafters, creating about an 8" space at the top and bottom for air to enter and exit. You can see the first few pieces in place behind the fan above. I used dry wall screws to hold them in place. Of course, the black painted side is facing up. Here's a photo showing the metal installed around the fans:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-09-06_10-33-38_879.jpg)

After reaching this point, my buddy Jimmy came by and took a look and suggested that I seal off the area between the fans to create a plenum, or a mini attic inside to direct the air flow. This shows a picture of the boards filled in between the fans with insulation above:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-10-15_10-33-52_856.jpg)

And then a photo with my camera held really high to show the insulation laid on top of the boards:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-10-15_10-34-08_674.jpg)

After these photos were taken, I filled in the end areas.

OK...finally time to do the doors. As I mentioned before, I decided to use multiple sections in the door area since my opening is about 16'-4" wide. I've seen hinges come loose on too many kilns with even smaller openings, so I decided to hinge a 3' section on each of the 2 ends, and then use removable sections in the center. I ended up with 5 sections, including the 2 doors. Anyway, each section (and door) is a simple rectangular 1x4 frame glued together with biscuit joints. It's pretty flimsy at first, but that doesn't matter. Next, I set the frames in place in the channels I made with the 1x4 trim around the whole opening at the top and bottom. The doors were hinged into the ends, and the center 3 frames were set in place. All 5 frames had about 1/2" between them...no perfect fit here....it isn't necessary. Then I began installing the siding over the frames. By setting them in place, this enabled me to keep the siding straight with a string:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-10-05_14-18-23_964.jpg)

Once the siding was installed, I removed the 3 center pieces and installed some 1" styrofoam insulation. Here's the before and after of that:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-10-12_08-02-26_126%7E0.jpg)


(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-10-12_09-34-35_806%7E0.jpg)

Next, a screwed my 3/8" x 8" boards to hold the insulation in place (being careful not to let the boards interfere with the fit on the channels:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-10-12_09-45-31_726.jpg)

Here's a photo of the completed kiln with the end doors open and the center three panels set in place:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-10-17_12-46-47_174.jpg)

This photo shows the doors open, and one center panel set aside:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-10-17_12-47-26_378.jpg)


And here is a photo of the rear canvas tarp cut to hang down. When a load of lumber is set inside the kiln, the canvas will be laid on top of the stack. This will direct the air flow back up to the rear top of the rafter plenum system:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-10-17_12-47-40_738.jpg)

Here's a photo of the completed Kiln, ready for use:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-10-17_12-46-17_304.jpg)

Mission accomplished!

Looks good. Bet you are glad that job is done and ready to load her up. Tell us what are you going to dry first? bg

Looks great!  It sure is in a nice sunny spot.

 8) 8)

Thanks for all the detailed descriptions and pics. :)

I'm considering building a new kiln and seeing yours complete has inspired me to think about getting started. ;) :D

Well, my brother, a contractor, stopped by today and saw a large stack of beech that I cut into 1" material about 6 months back. He thought he'd ask his cabinet maker if he would like to buy it. If he's interested, I guess I'll load it into the kiln to get it down to 6% mc. Be nice if that works out.
I had planned on drying some cedar logs first in it though. I need to cut them to 1" stock and then stack them inside. Probably will be a few weeks before I have time to though. Right now I'm tearing down some old fencing here at my place. I'm trying to finish one thing at a time completely before moving on. Take care.

Quote from: Planman1954 on October 19, 2011, 07:28:13 PM
I'm trying to finish one thing at a time completely before moving on. Take care.

Don't set an unreachable bar for the rest of us  :D.

Wow, beautiful kiln and what a neat idea- doing one thing at a time.  I've never been able to do that.  Yesterday, working on finishing up plumbing work for the dry wall to go up on the house I'm building, I started with some jackhammer work, laid it down to get a bucket for the chips, saw the door sill plates needed cutting in the closet, picked up a saws-all and did that, then went to get the bucket.  Filled and emptied that, then grandson pointed out that we needed to finish framing up his "portal" window, so cut the pieces for that to make an octagon that will be the frame and nailed those in place.  Then cleaned out some of the tools and left-overs to make room for the dry wall hangers... never did get back to the jack hammer so that's waiting for today...   ;)

Lj

Hello fellers!
Been working outside this past weekend tearing down some old structures, and took some time today to stack a load of beech inside the kiln. I turned on the fans and the dehumidifier. It was great to see the air finally flowing around a stack of lumber. This particular load of beech has been air dried for about 6 months. The moisture content is about 10% right now. I hope to get it down to less than 6% so that I can sell the wood to a local cabinet maker.
I talked to pineywoods today, and he told me that this design doesn't fit any of the established drying criteria of typical dry kiln operations. He told me to let the fans and dehumidifier run continulously until the moisture content is what I want. During the day, the heat releases the moisture from the wood. During the night, the dehumidifier pulls moisture from the air at a higher rate than during the day. Oh, and btw, I bought my dehumidier at a flea market for 5 dollars. Seems like a good place to look for one, since I bought a second one for 10 dollars! The unit I'm using originally cost about two hundred bucks.
I'll try to take a photo during the week and post it showing the wood inside the kiln. I'll also keep ya'll posted on the time required to do the job. Take care. (UPDATE: The kiln seems to be doing a great job on the beech. I emptied about a half gallon of water the first day from the dehumidifier. When I open the door to check on things, it's almost like sticking my head in a warmer oven...I kid you not!)

Hey everybody:
The cabinet guy came by yesterday and said he would buy the load of beech. I showed him the mc was at 6% or below with a meter. It started at 10% when I loaded it, was 8% at the end of the first week, and now is at or below 6% here a few weeks later. I plan on putting the money towards a planer/molder and try to see if I can sell some crown mold and base. I've been looking at the Grizzly. Anyway, I am very happy with the kiln. It's perfect for a small potatos setup like mine!

Pineywoods should sell the plans!  That is a really nice looking kiln.  Post a pic of the beech lumber if you have one.

Planman1954, I like small taters too. Glad you had sucess on your first load. Getting a new toy will be nice. bg

OK WDH. You asked, and now you shall receive:

First off, I remembered that I had taken a photo of the beech before I put it into the kiln. It had air dried for about 6 months:


(https://forestryforum.com/gallery/albums/userpics/19339/3018/2011-10-27_07-53-01_731.jpg)

Here's a photo of the end doors open, with the beech stacked inside:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/2011-12-01_07-37-13_346.jpg)



(https://forestryforum.com/gallery/albums/userpics/19339/3018/2011-12-01_07-37-02_147.jpg)


And here's a closeup of my $5 dehumidier which worked like a champ:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/2011-12-01_07-36-47_986.jpg)

The fellow is bringing his trailer today to pick it up. Next up...a load of red cedar for my brother. I'm cutting it all 3/4" thick (on my saw gauge) and then will surface one face to about 5/8". He's going to use it to line a closet in his home he's about to build. Take care.

Re kiln plans.  Nope, I'm not the least bit interested in sellin plans. Got too many projects now. HOWEVER, I'm gonna let the cat out of the bag... Planman would be the best source. He draws house plans for a living and has the talent and means to do a first class job. Like I've said before, there's not much unique about this kiln. It's really just a modified chicken coop....but it does work quite well...

Speakin' of plans...why do you need um? Just read the post from start to finish...cut some lumber, and start nailin' it together. That's what I did! But heck, ya'll have an advantage over me here by having some real-world pictures and a how-to guide to follow. It's more than I had. Seriously, that's why I documented the progression so that others could build one. Good luck.

I think you will find that lumber dried in a cycle such as yours will produce more resilient lumber that is more machinable...

I have a small building out back that is relatively tight...I think I will move it and put a set of panels on and convert it to a small kiln....

Neat job, well done, very informative , thanks for posting Planman... Play safe..



             Dave

Quote from: zopi on December 01, 2011, 08:04:30 PM
I think you will find that lumber dried in a cycle such as yours will produce more resilient lumber that is more machinable...

I have found this to be correct. Hardwoods in particular are less brittle and easier to work when dried in a solar kiln. I am currently drying a batch of sycamore, supposedly one of the most difficult woods to dry.

Hopefully it won't warp its way out of the kiln before you are ready to unload it. 

I wanted to update a point about the clear plastic panels I used on the top of the kiln. Recently we had a hail storm, and it damaged the panels with about 40 holes. I thought about replacing the panels, and then brainstormed about how to repair them in place. I went to Home depot and bought one more plastic panel along with a bottle of PVC cement. I cut small pieces (about 4"x4") and placed glue on the existing panel around the hole, and then to one side of the new patch and set it in place. It worked perfectly! It took about 2 hours to cover all the holes...problem solved!

I just went out and took a closeup picture showing one of the patches near the  corner:


 (https://forestryforum.com/gallery/albums/userpics/19339/2012-04-21_09-44-03_663.jpg)

That must have been some hail storm!

Hope mine never sees a hail storm like that. But if it does, now I know what to do. Thanks planman for the tip. bg

Planman1954. Thank you for posting this project. As I sat here and read it I thought that would be the answer to a project I need to do.

I have a 16' home built building that is actually 3/4's of the way having me one like that. And I was thinking of tearing down the little shed anyway. A little whittling and I will have one too.

This is why I like this place so much. Stay safe guys.

Great Kiln and writeup,  I am hoping to build one similar someday soon.  Please keep us posted on how it is operating.  Thank you for posting

hey fellas, nice kiln design.  i'm almost finished building one very similar, although i've cut vents into the top and bottom similar to the virginia tech design.  do you think the pineywoods design would work with the vents and no dehumidifier?  or should i plan on closing the vents off and using the air circulation/dehumidifier in the evenings?  fwiw i'm in southern wisconsin around 43 degrees latitude if that makes a difference...

Sounds like you're talking hybrid here, so I don't know about effectiveness. The idea of the kiln shown here is the collector panels on top along with fans to physically circulate the heated air around the unit. The dehumidifier helps to quickly remove the moisture from the circulating air. I suppose any dehumidifier in a kiln would help, no matter what the design.

mikeb, I can only relay our experience. When we first built these kilns,there were no vents and no de-humidifier. SLOW SLOW and difficult to get wood below 12 -15%. The little d-h unit made a world of difference. Lumber bottoms out at around 6%. They are cheap 1 room units from sears.Vents...If you vent out the hot humid air, it has to be replaced with something, ie wet humid air from outside. This limits how dry you can get the lumber. The virginia design lays the metal collector on top of the stack, thus cooking the top layer of lumber. Fastening the collector metal to the bottom of the rafters allow 50% more collector area, plus the fans can pass air along both sides of the collector. Temps of 160 deg + are easily obtained...The optimum slope on the collector is 90 deg to the sun, but that varies by lat, season, and time of day. A good compromise is match your latitude..The only material I bought was the plastic roof and insulation.  Everything else came off the woodmizer..

Someone asked earlier about how well the kiln works. The answer is fantastic. I've gotten readings with a meter of 12% mc in as little as 4 days! For exterior use on my barn/rec room project, that'll work fine for the exterior boards. The interior boards I'll be leaving in for a considerable time, mostly with the fans and dehumidifier off...just to keep them stable. Running the fans during the early drying cycle gets the temperature high enough to kill bugs and larvae.
Here's the latest load I put in today. I still don't have a tractor...I do everything manually. But for me, that's just fine...all the sweat helps get me in shape! I remember my Daddy always wondered why folks would exercise and not just work. He liked having something to show for the effort expended....



 (https://forestryforum.com/gallery/albums/userpics/19339/2012-05-01_09-51-16_46.jpg) 

 (https://forestryforum.com/gallery/albums/userpics/19339/2012-05-01_09-51-28_283.jpg)

What species can you dry in 4 days?

Southern Yellow Pine...remember I said that it lowers the moisture content to around 12%...that's running the fans and dehumidifier night and day...good enough for exterior use on my project. Getting down to 6% mc takes about 2 weeks. It gets sooo hot in the kiln...when you open the door, it'll hit you like a low oven.

Everybody has to note that SYP is easy to dry. Hardwood would take much longer and would still be iffy.

Quote from: Den Socling on May 01, 2012, 11:26:07 PM
Everybody has to note that SYP is easy to dry. Hardwood would take much longer and would still be iffy.

longer,  yes.  iffy, no...Ran a bunch of water oak through mine, made tongue and groove flooring. No problems with the wood, took about 6 weeks to dry...Plannman dried a batch of beech, used to make cabinets.

thanks for the feedback fellas.  i should've been more specific:  i'm definitely using the pineywoods idea of a solar collector mounted under the greenhouse plastic.  i guess my question was more to the venting and need for de humidifier.  sounds like you guys are def recommending a de humidifier but it sounds like i should make my vents closeable so as to control the amount of outside air coming in?

Kiln looks great, just have a couple of questions.How long did you let your construction lumber dry before building the kiln? What is 3/8" x 6" lap siding and do you mill it?

Thanks Frank

As I remember, the pine I used to build the kiln was air dried for a few months before I used it for the kiln. (There is a photo of it on the post.) The thin 3/8" x 8" boards were cut on my mill and used for the inside wall areas. The outside lap siding tapers from about 1/8" to 5/8" and is 8" wide. I think the exposure (or the part that shows) is about 6 1/2". I cut all the lumber on the kiln. I think there is a photo near the beginning of the post showing all of it cut. Hope this helps.

I saw your pictures they look great.Thanks for the info.How do you mill lap siding?
Thanks Frank

Quote from: Planman1954 on May 06, 2012, 09:47:54 AM
As I remember, the pine I used to build the kiln was air dried for a few months before I used it for the kiln. (There is a photo of it on the post.) The thin 3/8" x 8" boards were cut on my mill and used for the inside wall areas. The outside lap siding tapers from about 1/8" to 5/8" and is 8" wide. I think the exposure (or the part that shows) is about 6 1/2". I cut all the lumber on the kiln. I think there is a photo near the beginning of the post showing all of it cut. Hope this helps.

I thought you might ask that! First, I saw a cant 8" wide and stand it up on my mill. It doesn't matter how tall it is. Then I take a few little pieces of 3/8" x 3/8" stock (no more than 6" long) and slip them under the edge of the cant in a few places for support on the infeed side of your bandsaw mill. You've now successfully tilted your cant just right! Drop the blade about 5/16" from the previous flat cut and make a cut. Voila! A piece of beveled lap siding. Take the little pieces out for the next cut and, this time, drop your blade about 11/16". You'll get into a routine of 1" increment drops for the 2 cuts. I just keep going till I get to the bottom and finish off with a flat board of 1" or 1 1/2"...where-ever I end up. That's how i've cut a ton of siding... Have fun.

Vfauto:
I looked back, and I don't think I've shown any pictures of the lap siding I use around here. Here's one:



 (https://forestryforum.com/gallery/albums/userpics/19339/Lap_Siding.jpg)

You can see the tapered profile of the boards from the end view. They nail on easily due to the thickness....5/8" down to about 1/8". Yeah, I know they vary a little, but once they're nailed on, they fit great. Oh, and that's not blood...it's paint. That's the color the recreation/music room/old barn will be soon!

(UPDATE: I decided to start a thread on making and installing 8" beveled lap siding. I guess I'll list it under the General Board category.)

OK...this is a first for me. I've posted a video on Youtube showing the kiln. Here's a link:
http://www.youtube.com/watch?v=wTnvkeDsp7c

Take care.

Thanks for the video Planman. I have most everything now to rework a shed into my kiln. How heavy are the removable doors in the center?

Nice job. Chuck

The center doors are not too heavy. I just lift a little and they pop out, and I lean them onto the hinged doors while I load the kiln.

Quote from: pineywoods on May 01, 2012, 11:38:32 AM
The virginia design lays the metal collector on top of the stack, thus cooking the top layer of lumber. Fastening the collector metal to the bottom of the rafters allow 50% more collector area, plus the fans can pass air along both sides of the collector. Temps of 160 deg + are easily obtained...The optimum slope on the collector is 90 deg to the sun, but that varies by lat, season, and time of day. A good compromise is match your latitude..The only material I bought was the plastic roof and insulation.  Everything else came off the woodmizer..

The Virginia Tech Solar Kiln collector is just a sheet of plywood painted black not metal  . The optimum slope angle should be 37 degrees .

Quote from: Dave Tarheels on May 30, 2012, 02:33:30 AM

Quote from: pineywoods on May 01, 2012, 11:38:32 AM
The virginia design lays the metal collector on top of the stack, thus cooking the top layer of lumber. Fastening the collector metal to the bottom of the rafters allow 50% more collector area, plus the fans can pass air along both sides of the collector. Temps of 160 deg + are easily obtained...The optimum slope on the collector is 90 deg to the sun, but that varies by lat, season, and time of day. A good compromise is match your latitude..The only material I bought was the plastic roof and insulation.  Everything else came off the woodmizer..

The Virginia Tech Solar Kiln collector is just a sheet of plywood painted black not metal  . The optimum slope angle should be 37 degrees .

Dave, could it be that the VT design calls for 37 degrees because Virginia tech is at about 37.5 degrees of Latitude. Therefore, 37 degrees is what would be most efficient at their location. I would not use the same angle for the southern tip of Florida and the northern boundary of Montana. Here, I would use an angle of about 48 degrees, but I am also alot farther north.

Reride82  --   For example Blacksberg , Va is about 37.2 degrees north Latitude and Durango Colorado would be about 37.6 degrees north latitude . This is a year round application . I live on the coast so mine would be a little less than 37degrees , here is a website for you to determine exactly what degrees would be suitable for you , hope this helps .  Reride , I was referring to the guys in the discussion who live on the east coast who had their kiln at 48 degrees , your Kiln should be about 45.99. Thank you for the feed back reride82

http://solardat.uoregon.edu/SunChartProgram.html

Remember the scene in the Apollo 13 movie where the astronauts had to manually align the capsule on a controlled burn towards the earth? That's how I see the alignment issue. Let's try to get the angle as close as possible, and let the chips fall. Pineywoods said at our latitude in Louisiana, 45 degrees was close enough. That's what I did, and it created an oven inside the solar kiln.

All this to say, follow the guidelines, do your best, and it will work! Just build it! :)

A small deviation from the optimum angle is not that big a deal.

Another consideration is whether you will be using it primarily in one season or another of the year. You could optimize it for your primary use.

Also, if you live in a part of the country where some seasons have lots of cloud cover with little sun, you are probably not going to get much drying done in that season. You might want to consider optimizing for the time of year you actually have sun.

A common mis-conception is that solar kilns require direct sunshine to function. Not necessarily true. What makes the heat is infra-red radiation, not sunlight. Infra-red will penetrate cloud cover to some extent. I frequently see temp gains of 20-30 degrees over ambient on cloudy overcast days. The collector angle is a huge bundle of compromises, I picked 45 deg as an easily constructed best guess, seems to work fairly well for a deep south location.

You can build your solar kiln at any angle you wish and it will work,  your still using the same concept . I feel getting your solar kiln at a angle that best suits your location to achieve maximum efficiency is the best way to go . I would take consideration of information available to you from universities, etc,  and implement that info into your design . I have seen charts that show being off 10 degrees can be a significant loss in BTU's . It's a solar Kiln so I would definitely consider ways that allows the most solar energy to penetrate your kiln  .

An update on Planman1954's solar kiln. He took my advice and avoided plastic fans. Couple of weeks ago, both of the metal circulating fans quit. Wouldn't run at all. Rather than get new ones, I took them apart to see what failed. Both fans had a small plastic module with a wire coming out each end. It was wired in series with the motor winding, and was completely open. A little investigating revealed them to be a thermal fuse, somewhat like those in a fire sprinkler. they were marked "75C", in other words they blow at 75 degrees centigrade. That's somewhere in the neighborhood of 180 F. That should forever lay to rest the notion that solar kilns don't get hot enough to kill bugs...

Those are some DanG roasted dead bugs!

Quote from: pineywoods on August 16, 2012, 09:24:30 PM
An update on Planman1954's solar kiln. He took my advice and avoided plastic fans. Couple of weeks ago, both of the metal circulating fans quit. Wouldn't run at all. Rather than get new ones, I took them apart to see what failed. Both fans had a small plastic module with a wire coming out each end. It was wired in series with the motor winding, and was completely open. A little investigating revealed them to be a thermal fuse, somewhat like those in a fire sprinkler. they were marked "75C", in other words they blow at 75 degrees centigrade. That's somewhere in the neighborhood of 180 F. That should forever lay to rest the notion that solar kilns don't get hot enough to kill bugs...

What make of fan are they?
John

It's a 16" feature comfort model from lowes...runs about $30.00:



 (https://forestryforum.com/gallery/albums/userpics/19339/6942630701534xl%7E0.jpg)

Quote from: Planman1954 on August 17, 2012, 08:22:40 AM
It's a 16" feature comfort model from lowes...runs about $30.00:



 (https://forestryforum.com/gallery/albums/userpics/19339/6942630701534xl%7E0.jpg)

Thanks,
John

During Constrution,Could you not place the fan on the outside? with the blades inside.Maybe cover the motor so it won't get wet ?  ???

 :P i like this one.
I didnt see it but did you plumb in a  pvc tube in the catch pan for the dehumid. and run it outside so you didnt have to go inside and manually dump them?

I cut a hole near the top of the water pan and just ran an overflow flexible tube to the ground under the door. Simple...but effective if I don't dump the pan soon enough. You can see it in the video.

My friend, Jimmy Smith, who I mentioned earlier in the thread, died last friday night. He has influenced me in many ways since I've moved up here to north Louisiana to the country. He grew up here, knew all my folks, and even plowed my grandfather's garden with a mule. He got me into milk goats (no longer raising them) and milling. He had a Norwood lumbermate, which he showed me how to use. He went with me to south Mississippi to get my own norwood. Anytime something would come up, whether gardening or hunting, or anything dealing with country life, he would tell me how to do it. We'd always laugh since I'd go to the internet and check it out, since every time, he was right on how it was to be done! I even posted a week or two back about sap in trees going to the roots in the winter...something his father said when he was a kid. I feel like my brother just died! I went by his house yesterday and saw all the boards leaning up on the the barn, ready to be nailed into place that he had just cut on his norwood. I don't know if I can go back there for a while. His hammer was propped up on the boards ready to be picked up. And all the goats yapping wondering where he was! He had about 10 baby goats born last week. He was up, probably all night, tending to them. He overdid it, and fluid bagan to build around his weak heart (He had surgery about a year back...pacemaker, etc.) He didn't make it. I played at his funeral monday. Tough to do. This is my tribute to him. He is with Jesus now...and he KNEW his bible and Savior.

Condolences, Planman.

Planman,.

That was a very moving post about your friend.  I know that the loss will be huge.  I am very sorry to hear this.

Planman, I am sorry for your loss. You and your friend are in my thoughts.

Levi

     Planman, you wrote that well.  My condolences on your loss.

May he rest in peace and may peace be with you Planman. Great friends don't just happen. bg

Sorry to hear about your friend, Planman.  Isn't it great, though, the time that the Good Lord blesses us with with friends and mentors like that.  Sounds like he had a nice long visit here, but now he's home.  Thanks for playing at his funeral ... I'll bet it meant a lot to him.

Pete

Thanks for all the kind words fellas...it helped me to process things to write it down...it's a bonus to know others understand.

I wanted to clarify the angle of the glazing. For maximum efficiency for summer operation, use a roof angle equal to your latitude. To get the most out of year round operation (get the most you can in winter) add 10 degrees to your latitude. You'll find that 37.2 degrees latitude + 10 degrees is 47.2. The amount of loss of efficiency going to 45 degrees is insignificant given the ease of cutting 45. We use a 45.

Brian

, 

Quote from: Dave Tarheels on May 31, 2012, 06:55:50 PM
Reride82  --   For example Blacksberg , Va is about 37.2 degrees north Latitude and Durango Colorado would be about 37.6 degrees north latitude . This is a year round application . I live on the coast so mine would be a little less than 37degrees , here is a website for you to determine exactly what degrees would be suitable for you , hope this helps .  Reride , I was referring to the guys in the discussion who live on the east coast who had their kiln at 48 degrees , your Kiln should be about 45.99. Thank you for the feed back reride82

http://solardat.uoregon.edu/SunChartProgram.html

I am really sorry, man, to read about losing your friend.  In our lives sometimes, we live a time with certain friends or family and then can't believe how little time we had.  I guess we should just make the most of every day.  My best friend died recently, too.  It is horrible.  But somehow we will make it.

Planman, I am in the process of building a pineywoods kiln and had a couple of ?s for you or piney . First are the rafters 2x4s they look bigger in the pic. 2nd how does the tarp in the back work ,do you just drape it over the wood ? Also do you have to put weight on the stacks like you do for airdrying ? This is all new to me so any help would be appreciated .  Guess I should have started a new thread with all these ?s .

QuoteGuess I should have started a new thread with all these ?s .

IMO, I like to see such questions that relate to the thread subject kept in the same thread. ;)  I think you did good, board.   8)

Board: Yes, those are 2x4 rafters. There is hardly any weight on them, so 2x6 is not necessary. The heavy cloth tarp is attached to to top (underside of the 2x4 rafter) with screws, and then I used a 1x4 nailed flatways to the underside of the rafters to hold it really good. The cloth and 1x4 is forward of the back ceiling/rear wall intersection about 6" in order to not cover the metal hole which allows the air to flow up into the rafters (see the construction photos.) The cloth is simply lifted onto the top of the stack after loading. When the attic fans are on, the air is forced through the stack, and the cloth directs the air through the rear of the stack back up into the rafter chute area. Take a look at the video I posted earlier. I show the way it works. Have fun...and build you one. It doesn't take too long. Oh, and I dry pine immediately after I cut it. I don't air dry it at all. I did a load of beech early on which had been air dried for months, and it took only a few days to get to 6% mc. Pine freshly cut, usually can get to 12% in about 6 days running constantly.

Planman, so sorry for the loss of your friend, he and Jesus are making sawdust together now. Very nice build you have there. I have a question about your build. If you were to fill the kiln how many board feet of lumber will it hold, say 1" sticked? I am in the contemplating stage of building one, I am thinking 2-3K board feet.

     Well, let's see...I made it long enough for 16' lumber. I probably don't want to stack it higher than about 4'. If I loaded 12" wide x 1" thick pieces stacked 4 deep, that would be 16'x1'x 4 pieces = 64 bf per level. And if I used 1" thick stickers, that would allow for 24 layers of boards. Soo....24 x 64 = 1536 b.f.
Thing is though, I don't think I've been over about 1000 bf loads yet. I don't max it out, since I'm by myself, and don't saw much more than I'm using at the time.
     Also..thanks for the kind words about my  buddy. I still miss him, though its been a few months now.

Hey Planman

We have really enjoyed having this thread to refer to as we have been knocking together a similar kiln over the last week in between rain rain and more rain! >:( :D

Just a quick question  about the fans you used... Do you have a thermostat controlling them? and did you end up fixing them or swapping them out after they quit working?

Thanks for taking the time to document your build, it's been inspiration to go ahead and build one ourselves! 8)

Thanks

I'll go ahead and answer this, sometimes planman goes several days without logging on.. No thermostat on the fans, just an on-off switch. The fans had an
internal thermal fuse. they blew at 70 deg C . We just wired around them. Don't use plastic fans, they will melt. Fans seem to last longer if you leave them running 24/7.

I ahve not had any problems with my fans, but the fans are not in the direct sunlight and not on a thermal swittch.  ALso my fans are generic box fans with plastic blades.  One thing I did was to remove the plastic grate covering the fan blades, but that was only to reduce the restance of the air flow.  So far I have only max temps of 140 ish..    I am monitoring temp and humidity with a off the shelf remote indoor out door sytem I bought from a "box store".  (cost me $15)  This way I can check it from the shop.  I just posted photos of the kiln I just finished in another post. 

https://forestryforum.com/board/index.php/topic,67753.0.html

Hi Anderson:

Piney was right! I don't log on a lot lately...been busy working on my barn conversion to rec room/music room.

It makes me happy, happy, happy that folks like you take advantage of the thread to build your own kiln! Way to go.

The fans do l ittle good when the RH in the kiln is high.  In fact, if you run the fans 24-7, you will dry during the day and regain at night.  So, we always suggest turning the kiln fans off when the RH gets around 90% RH for wet wood and 70-80% RH for dry wood.  So, an on-off switch is great. 

As we know the RH will be close to 100% RH in the morning (which also means stress relief, or casehardening relief), and it will take an hour or two or three after the sun rises before there will be enough heat to lower the RH, we can also use time-of-day to turn on the fans.  Likewise, two hours after sunset, the RH will again be too high, so turn them off.  Overall, this means you could also use a timer on the fans.  Experience will allow you to fine tune.  Of course, here in WI in the winter, the fans are idle for several months.

Is there any reason you could not mount the fans outside of the kiln?

Thanks
Matt

The pineywoods design shown in this thread is a sealed design. There are no outside vents or openings. The air circulates inside the structure in a circular fashion requiring the use of the INTERIOR fans to initiate the flow. A dehumidifier is used to expel the water (humidity) from the inside sealed area. So no, fans are not used to gain or expel air from the kiln.

Just read through this whole thread again, and it is just excellent information!  It's been quiet for a while, but I'm finalizing sketches of a solar kiln and like the pineywoods/Planman design I think.  Maybe just a couple of questions now that you've had a couple years of experience:

1) Do your fans blow up or down, i.e., up into the plenum or down out of the plenum?  I'm assuming up?  If so, since heat rises, is there any reason you can think of that you wouldn't pull air up the collector, into the plenum, and blow it down towards the pile?  Seems like you might improve air flow just a tad??  Plus, it would be pressing the canvas onto the pile and forcing more air through the pile?

2) I'll probably be drying mostly hardwoods, and I read you can actually dry them too fast (especially if green), so the VT design talks about covering part of the collector for small loads.  Do you guys do anything special for small loads to slow the process down?  Also, the "rule of thumb" is 1 sq ft of collector for every 10 bf -- do you think that also applies for this design?

3) I'm thinking about using solar-powered roof vents for the circulating fans, to save on electricity and be more "environmentally conscious".  (But I only hug trees because they make beautiful lumber!   ;D )  But I have yet to find a solar-powered dehumidifier!  Any thoughts on just using heat and vents?  Especially considering 2) above ...

4) Just a general question: anything you'd change now that you didn't think of earlier?

I'll probably think of more questions, but many thanks for now! 

Sb, check some of the posts about solar kilns by Bill Gaiche. His is strictly solar with solar fans I do believe.

Thanks, will do.

Sawyer, the fans blow downward, pressurizing the plenum formed by the back wall/door, floor, baffle, and one side of the stack. Makes for even airflow through the stack. Not obvious from the pics, the sheet metal on the bottom of the rafters is 6 inches short on the bottom end and another 6 inches on the top to allow an entry point and exit for air flow between the sheet metal and the glazing. There is considerable convective airflow up that tunnel, even without the fans running. It gets dumped into the enclosure just above the fans. I leave the fans running 24/7 and cycle the dh on at night, off in the day, using a thermostat in the dh. Unless you live in a dry climate, don't even think about runnin without the dh. I can just about guarantee it will RAIN inside the enclosure. A few guys are building with a small door on one end and the back a solid wall. To each his own, but I think that is a mistake. That full width back door does nothing for performance, but it will make a huge difference on your back.

piney, thanks, especially the advice on dh. I would like to be off the grid, but sounds like bad idea. Don't need rain in the kiln!

JMoore and I installed the fans(2), 24" 4 blade 1/2hp, into the plenums of our solar kiln today.  When he plugged them in, I was in the kiln and the air was rapidly moving up the short wall and over the collector (was not quite as violent as a hurricane simulator).  Is it possible to have too much air flow?  It seems like the air is moving too fast across the collector to pick up much heat.  I would appreciate any opinions.   
Thanks,
Caveman

Yes, air flow and velocity matter, depends on the species of wood being dried and it's moisture content  Wet oak does best at 200 to 250 fpm.  Pine and other soft woods like a good brisk breeze, 600 fpm or better.  The wetter the wood, the more air flow contributes to drying and also possible defects to sensitive lumber.  As the lumber dries out, the effects of air flow and velocity diminish.  So if you plan on putting in a lot of air dried oak, it may not cause harm.  Pine won't care, if needs to be dried fast.

Big, wide doors are a help, so you can load and unload the lumber charge very easily with a forklift or other such machine. 
YH

Could you put a varible speed switch before the fans? Have one switch for the fans?

Thanks Yellowhammer and Cfarm.  Most of the time we would probably air dry oak before putting it into the kiln.  I had thought about adding a rheostat to the fans. 
Hopefully we can have it ready to go and load it with pine before the end of the summer.
Caveman

Maybe I missed it but has anyone used the spray in insulation yet   I know they have closed and open cell insulation.  I have the stuff in my house and it is excellent. I was just concerned about it over heating or causing condensation. One of my neighbors installs the stuff.  Is it safe to use??? Any thoughts

cost.

DIY spray foam is about $1/sq-ft/1" thick.

from va-tech's plans they estimate roughly 300 sq-ft of interior surface to insulate.

They are using R11 fiberglass batting. Current pricing at my local stores about $120 for that much insulation

To get R11 out of foam we need nearly 2".  $600 if I'm perfect, the first time doing it, and use the 600-foot kit, with no waste. The reality, is I'd probably want to mostly fill the cavity and get the most out of my insulation space, and get closer to a R20. So call it a 3" fill... now I'm closer to $1000 in foam.

Sure I get a better insulated kiln, but is the nearly $1000 more worth it.... only the builder can make that decision.

I am currently building a chamber for my Nyle L200M DH unit and, in the design phase,  they suggested spray urethane foam.  More costly but more efficient and considerably less work to install.  Local pro pricing was $3 per square foot for 2" thick plus .80 per square foot for each additional inch. 

It is not just insulation vs. insulation comparison since the spray also acts as your interior coating and vapor barrier.  You save on interior plywood, corrosion-resistant fasteners, water-resistant paint, time to cut and fit, etc.  When I considered those savings it made sense to go with the spray.  I am adding 2" of rigid foam in the ceiling before the spray is done and going with 3".

I'm not sure I'd forgo interior plywood. I like the damage resistance the ply provides vs having an errant board crush or knock off the foam from inside the kiln. but I completely agree with regard to air-tightness and vapor barrier uses of the foam.

Also in a kiln where you are paying to heat it with electricity, high insulation R value, and air-tightness has direct pay-offs in lower utility bills.

I considered the impact resistance of having plywood but since I will be loading from the end on a cart there shouldn't be any boards moving around inside the chamber. 

I you use foam, urethane foam is stable at the temperatures (160 F) that the kiln will achieve.  However, the rigid foam panels are often better and then use the foam to seal the edges.  Overall, the better the kiln is insulated, the better it will work.

Regarding fans, it is rare that you will have too much fan speed.  An empty kiln will seem to have lots of flow, but when the lumber pile is in place, the speed is reduced to the desired velocity value of 250 fpm through the load. 

Do you know the fan capacity?  The formula for desired cfm Is velocity x (sticker space in inches / 12) x lumber length x number of sticker openings.  Then add 50% more for leaks.

Note that many species, including pine, spruce, aspen, maple, ash and basswood (plus more) will dry with better color using air flow around 500 fpm 6 miles per hour).  Of course the humidity must also be low enough for good color.

Example:  for 16' lumber with 3/4" stickers and 24 layers (25 openings) at 250 fpm, then 250 x (.75 / 12) x 16 x 25 = 6250 and then add 50% and you have almost 10,000 cfm.

Incidentally, block any gaps. 

Also, the VT kiln works best if the fans blow south (down the roof).

Quote from: GeneWengert-WoodDoc on January 22, 2015, 07:49:18 AM
... the VT kiln works best if the fans blow south (down the roof).

Doc, that's counter-intuitive to me ...  Can you elaborate?

What part is counter?  If it is the fan direction, here is the thinking:  The fans are fairly far back and high.  As the solar is converted to heat by the black-painted walls and pile cover, the heated air rises and then the fans pick this heated air up and immediately blow the air through the pile, if the fans are blowing south.  While in the pile, the air picks up moisture and cools, and the humidity increases. The humid air exiting the pile is then sucked up along the north wall, but a little of the humid air goes out the bottom vents.  Fresh air enters through the top vents.

Now if the fans are reversed, the heated air is picked up and blown by the fans to the north wall and some will go out the vents before it does any evaporation.  Cool fresh air will come in the bottom vents and immediately go through the pile.  This is not too efficient, as some heated air is lost before doing any work.

OK now?

Thanks Doc. That cleared it up.

FRank

Since heated air rises, it seemed like it would be more efficient to pull the air up the south wall.  But I understand now about pulling in fresh air before entering the pile.  But then why not put the lower vents on the south wall?  Seems like it would be easier to control the flow through the stack as well as the amount of fresh air. Maybe I haven't thought that through completely ...

Where might I purchase building quality plans. I'd prefer the basic VA tech model.

Google it and you will find the plans.

Hi Planman...Nice job on your kiln build, you did a great job!
I like the idea of the dehumidifier to get that water outa-there ;D

Is there air coming in just under the plexiglass? or is there no vents at all?

Cheers

Quote from: Tree Dan on January 27, 2015, 07:18:47 PM
Hi Planman...Nice job on your kiln build, you did a great job!
I like the idea of the dehumidifier to get that water outa-there ;D

Is there air coming in just under the plexiglass? or is there no vents at all?

Cheers

It's a closed system, no vents at all. Around here, bringing in outside air just brings in WATER. so seal it as tight as possible. Don't try to run one of these without the dh unit. You will literally see it rain in the kiln.

Where might I purchase building quality plans. I'd prefer the basic VA tech model.

Baron - if you google "va tech solar kiln building plans" among the results will be "Design and Operation of a Solar-Heated Dry Kiln" which will allow you to download a file 420-030_pdf.pdf.  That file contains as close to a set of "plans" as I think you will find for the Va Tech kiln.  Pages 7-10 have elevations of each section of the kiln, and a material list.

Good Luck.

Thanks Landscaper,
I Got it and will read up. Might even build one if I can figure out how to keep it going in the winter.
Baron

I live in CT at 41.3° latitude.  Because of small lot, house and trees I can't cut down, at the best spot, a small solar kiln would get only 4-5 hours of direct sunlight in the summer, more in winter when leaves are gone.  What could I get out of a solar kiln under these conditions?   It would be great to be able to kill bugs.  Even 200-500 BF capacity would be great.

So...I had an appointment with a client about an hour away. When I was nearing my home, all the damage was getting worse from a severe thunderstorm that had rolled through had my heart racing a little. When I turned into the driveway, I spotted this first:

 (https://forestryforum.com/gallery/albums/userpics/19339/image~2.jpg)
I have a high deductible, so I'm on my own. And also, it is loaded with lumber I've kept dry for a few months to use in my barn ceiling. It all got drenched. Oh well, it's time to press on...cause...God is good!

That was bad luck! Two nights ago, Patti's Honda was parked outside the garage which was not the norm. We had a hailstorm that left dents all over her car. Ouch! Luckily she has $100 deductible.

Planman
The water shouldn't go deep into the wood. Get it mopped off and protected from more rain. Just the surface would take up much moisture and it will re-dry.

A bummer on the roofing tho, and the insulation which will take some time to dry out again.
A lot of extra work. But life will go on...

Thanks been there. I guess I'll get a tarp and throw over the top. It'll be a week or so before I can replace the panels. There was a lot of local damage around here...they just showed some on the news.

Yeah, the wood wont be ruined. Get a tarp over it, run the fans and open the vents, and it will soon dry out again. If it stays wet then funky mushroom things can happen, but if you get it dried out quickly it's no big deal.

Bummer about the plastic cladding though.

Of course, the tarp should go over the kiln. Not the wood. And like was said, the water on the surface will dry quickly.

Right...that's what I meant...the tarp over the roof of the kiln. Thanks.

Wow, what a mess.  :(   Sorry to see this, PlanMan.  I'm betting you see the rainbow somewhere at the end of this storm, though ... let us know when it comes, will ya?

Sorry to hear that your roof was damaged.  Must have been a bad storm.  Could use some clear plastic until you install the new panels.  Then you would get some heating to start drying the wood.

My brother helped me scrounge around and find some old tarps. We draped them over the kiln...easier said than done!

 (https://forestryforum.com/gallery/albums/userpics/19339/GetAttachment_aspx.jpg)
I had to get the tarp on quickly so that the dried boards inside could begin to dry again. They got soaked last night AGAIN! And more rain is expected. Anyway, all is well. The fans are now on and the dehumidifier is dehumidifying! 8)

Planman, sorry to see your kiln got busted up.  I am sure that you will get it fixed up and the lumber that is in there will have some more history to go with it (remember back in '15 when we had that hail storm....?).  Good luck with the repair.
Caveman

Sorry about the damage on your kiln. I cleared an area where I'm going to build my kiln last week. Hope to get started in next week or two. Two main things I'm thinking about are the length which I'm thinking maybe 18 or 20 feet long to put two stacks of 8 feet lumber in. Scared that 18 might be too tight.
On the doors, I do like the way you (Planman1954) did yours. Are you still happy with them? You said that they are not really air tight which I could see that. Do you think it really makes much difference in gaining heat during the day?

The doors do not have to be air tight, as almost all the time, we do want a little venting to occur.  The more air that comes in through the door leaks, the less air exchange we need through the vents.  In any case, the door should not leak rain water.

The length of a kiln is always an issue, but for each increase in length, there will be an increase in solar input, so that could be helpful, especially in early spring and late fall.  With a small electric chain saw, you should be able to trim any piece of lumber that are excessively long, so 18' is often long enough.  On the other hand, if you have two 8' stacks and are loading by fork lift, you do need at least 18' door space so you can get the second stack in after the first one is already positioned. 

Hope these comments and ideas help with your decisions.

I will be loading with a forklift. I'll just have to do like you said on cutting boards off if too long. Most will be 8' 3 or 4". Probably have to be careful on stacking on skids that I made to dry wood on. I made several skids different lengths that I stack on behind mill, I can move the whole stack with wood on or remove the lumber off and leave the skid alone. My forklift has a side shift that will help somewhat on loading the kiln.  I saw where YH had a picture of his skids and borrow the idea from him. They work great I can move a stack of wood out of the way and not get off forklift to arrange 4 by 4's to stack on.
Planman, how tight did you get your doors? I do plan on a DH in there also to run at night. My skids are 48" wide each to fit on my forklift blades, I believe you said your kiln was 5 ft wide, are you happy with that width?

The doors work fine. I just need new door latches. I'm not too worried about it being super tight, since the temps reach 180+ d.f.   I shut them tighter when drying. I would go for a 20' length if you plan on drying framing lumber. If not, I would go for the 16' length I have, since I can load two 8' length stock, which is suitable for most construction. It is actually 18' long I think, which allows for the few extra inches of clearance for rough lumber. Yes, and the doors work fine for me. It gives access to the interior dehumidifier without a large door to open.
Oh, and the lumber I was storing is now dry agin. I ran the kiln for a couple of days even though the tarp is on top and the dehumidier did its job!

Cut my siding and put on stickers to dry this week, cut 1/2" for board and batton sides. I have all my framing lumber ready also. Going to use concrete blocks on ground and 6 by 6 erc on top of them and go from there. Decided on 20 feet long and 6 feet wide, in case I want to stack an 8 and 10 feet stack in there together. Rain all night here so might have to wait a few days to dig power line out to where I plan on putting it. Digging the line under my garden and its soft there, have to hold off planting till that gets done. I'll go to Lowes today and check on clear panels. I'm going to do a little cheating on this project, got a crew building a house on the next piece of land to me. I've done a few things for them and they are going to come over and help put up all the framing next week or the week after. Not for free but hopefully not much. I'm not going to make this last all summer.
A few questions now.
Planman you didn't insulate floor, do you think you should of?
For an air block you use black paper, and put it on the outside wall, will plastic be just as good?

If you use plastic, always put it on the warm side of the wall.

thanks. I see planman use paper, which would be better?

I like the felt paper (I used 15#, although 30# would be fine.) It has a proven record of almost a hundred years in typical frame wall construction. In my barn (which is now going to be my music room/apt.) I can detect the vapor blocking effect of the felt (which I used on the outside of the walls prior to adding the lap siding) even as you enter the space from the outside. It retains a more constant temperature and a drier feel which can be detected by me after entering so many times as I've remodeled the building.
As I've mentioned in other posts, I'm not a fan of using poly on walls due to moisture buildup, causing mold. I personally saw some homes built here in the humid south with .006 mil. Poly. on the heated side of the wall with Sheetrock on top which had to be removed due to condensation and mold. It was messy. So I'll stick with felt on the outside wall with siding over that and insulation in the walls. If the insulation has a vapor barrier, the paper or foil should be on the heated side.
So, long story short, I used typical old timey house construction for my solar kiln, and the result was very satisfactory. I know others will think differently, and to them I say, GO  FOR IT! Just build it, and by all means, have FUN and enjoy yourself!

In the South, the hot side of a house wall is the exterior side most of the time.  If under the Sheetrock, it is likely in the wrong spot.  In any case, we always need to make sure that there are not two vapor barriers, which will trap moisture between them forever.

You are right there, Gene!!

I'm good to go! Back in the saddle again! Sittin' in high cotton! On top of the Kiln...uhh...world! Yep, yesterday, I climbed on my ladder on a forty five degree angle and bravely climbed to the top of the kiln to screw down the new plastic panels! It was actually pretty easy. I put a stake at the bottom of the ladder each time I moved it to prevent it from moving. I got the new panels at Home Depot:


 (https://forestryforum.com/gallery/albums/userpics/19339/image~5.jpg) Now I'm ready for some new walnut lumber I'm about to cut!

Quote from: Planman1954 on May 07, 2015, 01:41:13 PM
I'm good to go! Back in the saddle again! Sittin' in high cotton! On top of the Kiln...uhh...world! Yep, yesterday, I climbed on my ladder on a forty five degree angle and bravely climbed to the top of the kiln to screw down the new plastic panels! It was actually pretty easy. I put a stack at the bottom of the ladder each time I moved it to prevent it from moving. I got the new panels at Home Depot:


 (https://forestryforum.com/gallery/albums/userpics/19339/image~5.jpg) Now I'm ready for some new walnut lumber I'm about to cut!

Ummm...Plan...Not to be critical but I think you put it on upside down. ;) oz_smiley oz_smiley

Oh well...guess the water will run uphill!👍

It looks like you got plans for Australia instead of North America.

 :D :D

Question for planman or anyone on width of kiln. I was planning on making my kiln 6 ft wide and 5 ft in back but to keep the front 10 feet tall I'm going to have to lower the back side or shorten up the 6 wide to 5 ft to keep the angle at 45°. I made 4 ft wide pallets to stack wood on and plan on putting them into the kiln. Would 5 wide be enough for air flow front and back of stack? Only leaving 6" at most front and back of stack.
I really want to keep the front no more than 10 ft in case it needs to be moved or sold later.

The better spacing between the vertical north and south walls is two feet each.  This means a 5' wide pack needs 9' wide kiln.  The penalty for closer spacing is uneven drying which means longer drying waiting for all the lumber to equalize.  Larger fans would not help.

One option is to make the roof flatter so you can get the needed space, but you will get less solar heat.  So, then add a section in front that will only be a solar collector (no lumber in it, so it would not need to be a huge volume).  The front collector could be at 45 degrees or maybe even adjustable if you want to get fancy.  It would likely be about four feet wide (measuring from the top of the south wall toward the ground), the same length as the kiln, and maybe 10" thick (well insulated).  Normally we do not want more collector area, as the wood, like oak, will dry too fast, but in your case, your roof collector is too small, so this will add the needed area.  Of course, you will need to baffle the kiln so the hot air in this auxiliary unit gets into the kiln easily and uniformly. Clear?  Questions?

You could carry this one step further and make the kiln totally insulated and then use an auxiliary collector for all solar input.  Such kilns have been built, but the cost is more than the VT design without much benefit.  One benefit is that such a design would also allow for efficient DH use, as the kiln could run 100% on DH on a cloudy day or at night, and not have the nighttime collector losses in a kiln like the VT design.  In fact, this totally insulated design would actually be a Standard DH kiln with an auxiliary solar collector.  However, most DH kilns, once started, do not need any auxiliary heat.  In fact many already have enough heat, especially in the summer, so they have small exhaust fans.  The bottom line is that such DH with solar auxiliary kilns often MIGHT cost more to build and operate than going 100% DH.  You would need to check it out.

Thanks Gene, after reading your post I decide to keep it 6 ft wide and run a 45° roof for just 4 ft and just box to rest of the roof with clear roofing material also, keeping the total height at 10 ft. In the last 2 ft I'll make the area to hold probably 3 fans. It will be 20 ft long and probably never much time will have over 16 ft of lumber inside. So maybe I'll have enough panels in the 4 ft x 20 ft for solar collection. Also like I said I'll clear panel the top 2 ft (90° x flat roof) for extra sunlight there also. I see where planman had good results with just a 5 ft wide kiln. The whole idea of keeping it this size is if I want to move it or sell it later I can easy load it on my trailer and move it.

We have had a load of bald cypress in our solar kiln for the past five weeks.  The temperature was above 140° most days that I checked it at 6 p.m.  We ran a dehumidifier in there the past two weeks and it essentially quit removing moisture.  We had 1200 board feet in the kiln and a mantle that was not put in the kiln that was 12"x5"x 8'.  There were a bunch of 12" wide boards in the stack.  Some of the outside boards did not dry straight but most of them were on the top of the stacks.  The guy we sawed them for will use them to finish the remodeling of his house.  The wood he has started with was what we sawed for him in December.

 (https://forestryforum.com/gallery/albums/userpics/22883/image~123.jpg?easyrotate_cache=1471729709) 

 (https://forestryforum.com/gallery/albums/userpics/22883/image~119.jpg?easyrotate_cache=1471728185) 

 (https://forestryforum.com/gallery/albums/userpics/22883/image~121.jpg?easyrotate_cache=1471728225) 

 (https://forestryforum.com/gallery/albums/userpics/22883/image~120.jpg?easyrotate_cache=1471728217) 

 (https://forestryforum.com/gallery/albums/userpics/22883/image~122.jpg?easyrotate_cache=1471728249) I was into my third shirt of the day before 2 p.m. and wearing my warm weather work boots.
Caveman

@Planman1954 (http://forestryforum.com/board/index.php?action=profile;u=9339) or @pineywoods (http://forestryforum.com/board/index.php?action=profile;u=4000) would either of you want to take a stab at roughly how much planman's kiln weighs?  I am thinking of building one about 14' total, so I can dry 12' and under boards and thinking about putting it on a mobile home axle that I have.  I never plan on pulling it down the road, just move it around the place as I need to.  Putting it on an axle is a slick idea.  Banjo

Banjo, most mobile home axles are 7000 pound rated a few might be 5000.
As for actual weight, my kiln is 8X13, built on 2 6X6 timbers, no wheels. I skid it around using an old 40hp massey. Don't sweat the weight, just build it.

I am going to do just that.  I doubt it will come close to 5000 lbs.  Thank you both for the design.  Lots of good info in this thread. Banjo

I use skids, also. I put some close enough together to also use my forklift.  I've moved mine a few times, just remember the tall wall weighs much more than the short wall so the center of gravity is very much toward the tall side, so keep that in mind when lifting or skidding.

Make sure to take the weight off the axle when loading and drying.  One thousand BF of green oak weighs about 6000 pounds.

Will do WoodDoc.  Banjo

Anybody put HDPE black plastic panels as the inside walls of the kiln?Seems like it would be great for moisture and it's already black so no need for painting.

HDPE has a melting point around 220 F.  When used as part of a solar collector, it can get this hot...I measured 200 F air temperature in the peak of a kiln without the fans running, so the surface would be even hotter.  Also, HDPE is subject to rapid deterioration from UV light, unless an additive to absorb UV is included.

The black should be "flat black" rather than glossy.

Noted.  Thank you.

Interesting thread.  I just discovered it, I don't think I saw it originally.  rjwoelk and I have been talking about kilns for awhile and I've come to the conclusion that a solar kiln may be the only one that makes financial sense for me.  

One of my concerns is a windstorm.  I'm wondering how apt it is to blow over especially if it's empty?  If it blew over and was full that would be even worse.  I was thinking of building 2 of them.  I wonder how we'll they'd do with 2.5" or 3" walnut slabs?

I plan to attend the seminar in Blacksburg, Va in may.  I had thought of making one 10 x 20, but was told not to go too wide.  so maybe 8 x 20.  I want to put firewood in it when not drying hardwood.  I think if I use big skids to mount floor too, and with most stack only going up 4 feet or so, that the center of gravity will be fairly low.  although a 12 foot tall wall makes a good sail.  Our wind is from the south in summer and north in winter.  The slant will of course face south, so I would be more worried in winter if empty.  It usually is only  a sudden moment of wind gust that tips something so some anchors in the ground and cable should be an added safeguard.  I am from Kansas!  go Toto!   running-doggy

Mine will be 6x12 and built on skids so that I could drag it around if need be.  The space that I have to put a kiln is nowhere near electric, so solar is my only option.  

FF that sounds perfect for most hardwoods.  most do not want over 8 let alone 12 foot boards.  too heavy.  I may alter mine as well but already got a great deal (clearance) on corrugated polycarb sheets wide enough total for a 20 foot length.

Currently,my mill will only cut 10' 6".  I'm tempted to buy an extension, but I shudder to think about handling longer logs of any size.  I agree on hardwood length.  If I'm bucking logs, I cut them to 8' 6" if I can.  I will only be putting air dried lumber in the kiln, so I don't think I'll have to deal with a whole lot of moisture.

At night, the rh will go up pretty close to 100% even when you start with lumber that's air dried to 20%ish.  

FWIW, mine has taken 50mph wind from the north without turning over or moving.  It was empty at the time.

All in all, anchoring makes for a better nights sleep though.  I just haven't gotten around to installing anchors because it's sitting in "temporary" location.

There are a few members that have had their solar kiln blow over.

Quote from: Brad_bb on April 21, 2019, 10:44:16 AM
One of my concerns is a windstorm.  I'm wondering how apt it is to blow over especially if it's empty?  If it blew over and was full that would be even worse.  I was thinking of building 2 of them.  I wonder how we'll they'd do with 2.5" or 3" walnut slabs?

Brad, I was worried about our solar kiln blowing over last year when Hurricane Irma came through a year and a half ago.  John and I ran some ratchet straps over the frame and attached them to mobile home anchors.  During the height of the storm, I waded out to check on it and to my surprise it was still standing.  The most exciting part of that short walk/wade was that I waded through a floating wad of fire ants in the middle of the night.  


(https://forestryforum.com/gallery/albums/userpics/22883/IMG_0561.JPG?easyrotate_cache=1416869717)
 

They can be quite tippy when they are empty, but mine sits real solid when full.  They excel with thick wood, mine is loaded with about 800 bdft of 9/4 walnut slabs right now.  Its my kiln of choice for these types of loads.

I went through some numbers with Bob on what it would take to pay for an idry.  If we started with a 4 year plan to pay for the idry(not including interest), it would be about $1050 per month.  I figure you'd only be able to do 2.5 load per month average if you're doing 5/4 and slabs that are air dried.  You'd have to keep it loaded continuously.  so 1050/2.5 = $420 per load.  I did some calculations and figured loading 5/4 you'd only get 1000-1200 bf in there. I wonder if the 2000BF advertised size is with 3" slabs? I'm using the advertised kiln dimensions and figuring with stickers as I'm assuming you still need them.  With 2.5 inch slabs you'd get about 1350.  So let's just use 1200 as the average.  420/1200=.35.  So Whatever your labor plus energy costs are you need to add .35 to pay for the kiln capital cost. Let's just assume that loading or unloading is $150 each time (stacking and stickering and material moving might take 2 guys an hour and a half?)= 300 per load, which translates to 300/1200=.25/BF.  So now we're up to .60/BF not including running costs.  Let's assume it's .10/BF.  So that's .70/BF.  In my opinion, a 4 year capitol payoff is not great, but .70/BF is not great either when we have a local DH kiln who will dry for .30-.40/BF.  Plus what if you couldn't keep it filled continuously? That is the basis why I thought it would be too expensive for me.  The only way I can see of matching the local kiln in price is the solar.  Yes it will take longer than both, but maybe that will be ok for me, especially if I build 2 or 3 solar kilns?  I wish I could have and idry, but financially it just doesn't seem to make sense for me, especially since I don't plan on making it a business, at least not a full time thing.  I have lumber.  I've got a decent rate on spray foam....Just my thoughts and some rough calcs.

If I was a younger man, I would jump on the idry like a duck on a June bug.  In my area, kiln drying is in significant demand.

Both DH and Vac kiln drink electricity.  They must be full to be making money, so the power bill is significant.  I have been thinking and mulling over for some time that the best approach for me, especially since I need more space for air drying thick live edge, and since they cost almost nothing to run, is to build a crop of solar kilns.  However, I don't want to build that many, but have been talking to local portable garden shed builders, because after all, a solar kiln is nothing more than an insulated, skid mounted, portable garden shed with wider doors, a single sloped roof covered in clear corrugated plastic instead of metal.  So my strategy is to get the guys to build a few with these slight changes, drive up with one on their little flat bed truck, and push it off in the yard.  Then repeat a few times. 



 

When considering capital equipment purchases, don't forget about depreciation.

I can see it now, "yella Hamma solar kilns"!Not a bad idea!  Brad do you mind sharing the rate you will pay for closed cell spray in insulation.  @Brad_bb (http://forestryforum.com/board/index.php?action=profile;u=6191)   @YellowHammer (http://forestryforum.com/board/index.php?action=profile;u=11488)

I'd try to make sure I sell a lot of them in Hinton, WV.  I'd paint them all bright red with big white letters that instead of saying "See Rock City" would say "Roll Tide" on them.
  
That way every time @WV Sawmiller (http://forestryforum.com/board/index.php?action=profile;u=28064) looked out the window, he'd think of Bama.

   All those red kilns with white letters saying Roll Tide would be very healthy and you could advertise them as guaranteed weight loss devices too because every time I looked at one I'd probably lose my appetite. I think Ruby Falls and Roll Tide go together better anyway. :D :D

So to boil back to the beginning, the point of this thread was pineywoods design using sheetmetal just below the windows to act as the collector, and the assertion that higher temps can be reached by doing this versus the Virginia tech design?  That this is an improvement?  Has anyone talked to anyone connected with Virginia Tech, like the professor who's name is on the design plans, Brian Bond, Assistant professor and Extension specialist?  I ask just to see if they had considered that design?  Is there a reason they wouldn't want the higher temps? Virgina tech's fan placement and direction for airflow also seem to differ from pineywoods design.    I'm not judging either design, just trying to boil down the differences and wondering if there has been any discussion between the parties to see if info was shared?  I know pineywoods has done his own experiments....

This is Planman1954. I am the one behind this thread on solar dry kiln construction. The design I built was Pineywoods. I have NEVER stated that temperatures are higher than the VT design. I have only stated that are in excess of 180 degrees f.

So doc Gene Wengert was there years ago, and Brian Bond took his place.  Brian Bonds is teaching the class at VT May 16th and 17th.  If you are referring to backing the collector with black metal and creating a plenum, this serves in passive solar to create air movement. and if you wanted a combination kiln, the back side can be insulated, and at night the fans go off, and you can have air gates so you can hold some heat or add external heat with out big losses via the collector.  i believe the heat gain is dependent on the collector surface area and does not matter so much what it shines on as long as it is darker color.  I am learning along with you fellas and do not claim to know it all.  I have a bio,chem, physics background.  @GeneWengert-WoodDoc (http://forestryforum.com/board/index.php?action=profile;u=20498) 

I developed the VT kiln in 1978.  When I left VT in 1992, Brian Bond followed my position with the kiln.  He revised the kiln document and did a great job.

The same amount of energy goes into a kiln with a black absorber near the clear cover versus an absorber that is the walls, pile cover, etc.  the exact same solar energy enters the kiln. And with black absorbers, essentially all the entering energy is absorbed by the black surface, wherever they are located. The difference is that the collector right under the cover has less area, so there is more solar Btu's per square inch, which means it gets hotter.  The "away" collector is not as hot but has more area.  Both collectors provide the same amount of heated air inside the kiln.

In fact, if you blow air on one side of the absorber near the clear cover it will get much hotter than if you blow air across both sides.  Even so, the same energy will go into the kiln with one side or two side.

However, with less area convection is less...that is, heat released to the air = area of black surface x temperature difference x convection coefficient.  But, still, the heat released is not any more than the energy coming in. So, it makes no difference if there is an absorber right at the clear cover, or away...the black absorber absorbs the same amount of energy in either location...the energy coming in.  Once the energy is heat, a key is keeping the energy in the kiln until it evaporates moisture...so plenty of insulation for floor and walls, and a clear cover with two or even three layers.

I was typing this and Gene beat me to it, so I might as well repeat what he says.  Collector area drives the energy input into the solar kiln, no matter what the general configuration.  

In my experience, the overall performance of the solar kiln is based more upon its placement relative to the hours of solar exposure, the angle of the collector to the sun, and of course, how much solar there is, from season to season.  In my VA Tech clone, when my power went off, I melted the the plastic roof and blackened the insulation.  In addition the overall thermal efficiency is based upon the air leakage around the roof of other areas where the hot air cannot be driven through the stacks, in essence shortcutting it, and exiting without picking up humidity.  I know from my kiln, it is, in my opinion, a very mature, simple and efficient design.  I love improving things, but I just don't see a whole lot in the Va Tech design that isn't already optimized, and I use my continuously.   

YH has the basic design idea of the VT kiln...simple and very efficient at low cost.  It was designed for oak drying, which in 1978 was about half of the volume of wood dried in a kiln in the eastern and southern U.S.

If you pay 10 cents per kWh for electricity, that is equivalent to 9 amps of 110 v for one hour.  So, check you fan (or any other electric use) for the amperage.  A single kiln fan could be 1.5 amps, so a kiln with two fans run 12 hours a day would cost $0.40 per day.  So, adding an extra fan is not too expensive overall and might help dry faster drying species like pine or yellow-poplar.  However, for air dried stock, two fans are fine for any species.

Quote from: GeneWengert-WoodDoc on April 22, 2019, 11:02:41 PM
... and a clear cover with two or even three layers.

Great info guys.  Gene are you saying to build double or triple pane windows/collector in so that it's insulated and doesn't escape back out through the windows at night as quickly?
I was just trying to understand the difference in pineywoods design versus VT and whether one had an advantage?  Sounds like no advantage from what you guys are saying or do I need more clarification?  Thanks, Brad_bb   I want to make sure I do it the best way possible.  I only do hardwoods by the way.

Brad I think you will have to find your balance of time and cost to build, vs practicality.  As you add layers of glazing you increase insulation value with a dead air space.  but you add to cost and begin to lose transmittance into the kiln, especially with cheaper materials.  Some products will degrade over time and get yellowed and not as efficient.  Gene has written about the net benefit of more layers vs less and you get the most bang for the first, then second and then third.  You could use e rated glass and be very efficient, but high cost and in Ks the first hail storm might be not to good.  since the sunlight is ess. free and hobby folks have more time and or less volume to dry, a simple kiln makes sense to me.  Lowes changed the vendor on the corrugated polycarbonate, so I got 10 twelve foot long pieces for like 2 bucks a sheet.  A guy could prob. get old sliding glass door panes, but they are heavy and often clouded.  I will use my corrugated stuff with maybe a layer of uv protected sheet plastic over it to add to insulation and protect the more expensive corrugated stuff.  Thanks for continuing to throw out ideas and questions helping everyone (myself included) think through the process and design.

Hopefully I am not going to derail the conversation with these questions but I think they fit into this thread nicely.

I have 4 relatively large skylights on my house that are going to be removed. Will these make better translucent panels than the typical plastic being used? They are double pane. I would think the added insulation factor would be very beneficial.

When it comes to fans they can get very expensive. Has anyone ever tried to use a radiator fan from say maybe a ford taurus? Reason I mention the taurus is they are 2 speed fans. I would think these would be very easy to setup and run off a 12 volt battery with a solar panel to keep the battery charged making the kiln a standalone unit that can be moved anywhere without any electric.

Good questions.  I will give my 2 cents.  The skylights are great if the material and frame can stand the heat, and you have enough to get the square footage recommended for the size kiln.  The fans would need enough cfm also for the size of kiln, poss. adjusted for species and or if all materiel will be air dried first.  If you downsize for those criteria, you will then be limited in the future if you needs change.  window with a plastic frame may melt if temps of an empty kiln get too hot, especially with fans off.  If you have four, and they are not cloudy, you can add up the surface area and then size you kiln accordingly.  I think 10 board feet per 1 sq. foot of collector space.  If the skylights are 2 x 4 feet or 8 feet each then for four of them you are looking at 32 sq. feet, x 10 is a kiln that can hold or process 320 board feet.  It could do more if it were oak, or pre air dried.  We can see if Doc W chimes in.  @GeneWengert-WoodDoc (http://forestryforum.com/board/index.php?action=profile;u=20498) 

The skylights will equal 586 sq. ft.

Remember that the original 10 to 1 ratio is for oak hardwoods, which requires slow drying.  

Also, that a solar kiln can easily be temperature regulated by venting air, which costs nothing, so too large a collector area can easily be mitigated.

Some wood species can be dried at a much faster rate than oak and are much more tolerant.

The main drying impacts I have seen are more due to Mother Nature and a distinct lack of solar energy in certain seasons or days.

I have been using $20 Wal Mart fans since I built the kiln, several years ago.  I am on my third set.  So I have $120 invested in fans over the years, which is the price of one good high temp, long service life unit.  I have burned the blades off one fan, but it was during the power outage.

Due to these points, I would endeavor to slightly oversize the collector (roof) to make up for the low solar days.

Now is the time to build one, lots of sun.

Although my solar kiln may be the least expensive piece of kiln equipment I have, I trust it completely, it is virtually foolproof, and I consistently load it with my highest value, thicker wood.    

wow so these are like 12 x 12 foot sky lights?  or do you mean you can dry 586 board feet of lumber?  that sounds great.  more details please if u do not mind.  nice info YH.  if you go solar with 12 v batts, you can go with 12 v fans or invert up to 110.  with every energy change there is a little heat/energy loss.  but the cheap fan would make it worth it I think.  you can buy watt meters to test your fans to see what they pull.  i think glass is much better than plastic, especially if it is low E ect.

Quote from: doc henderson on April 23, 2019, 05:05:20 PM
i think glass is much better than plastic, especially if it is low E ect.

Low E, or low emissivity glass has as coating on the inside of the glass that re-radiates a lot of the heat back to it's source.  So isn't that preventing heat from coming in the collector? I would think that regular glass, double pane would work better as it would let the heat in and the air space between the panes would help insulate to keep that heat from convecting back out too fast?  If I am wrong please explain.

I was wondering same thing brad. thats why I asked the questions. my hope would be the little loss of heat coming in would be made up for how long it holds the heat. I think it is going to be a series of tradeoffs.

Doc I have a total of 586 sq ft worth of glass in the skylights. unfortunately they are all different sizes. But I think it will still work out well for the roof.

the skylights do open so that could make a very efficient vent as well.

We are really getting technical here.  First, about half of the solar radiation is longwave, near-infrared radiation.  So, low e glass will reflect much of this half.  The same is true for glass that is green when you look at the edge.  The sun is hot, so we need transparency of near infrared, meaning near to visible, radiation.  Now, the hot surfaces in the kiln emit longwave radiation, but their low temperature compared to the sun means they emit far-infrared longwave.  We do want this energy, which does not come from the sun but from objects at 100 to 200 F, to be reflected back into the kiln.  This reflection is what many plastics and glass do.

There is no question that clear glass may transmit 92% -  95% of the incoming, so two layers transmit maybe 85-90%.  Two layers mean less energy, but their insulation value makes up for that big time.  Three layers, it is closer to a toss up, depending on the materials.

Thanks for the input and help Doc Wengert.  yes I respect the reduce, recycle and reuse concepts going on.  If we could build the perfect Kiln for no cost, our goal would be realized! :D  My favorite work saying is "we have done so much, with so little, for so long, I now think we can do almost anything with nothing!" :)  

In the past, that saying may have been true. In today's world you aren't aloud to do anything even with everything you need.  >:(

amen brother! and in all fairness, I believe it originated in the military.  like many good things 

I know some have built kilns on trailers.  I'm th8nking the same.  If I can get a cheap enough old trailer, I can save on skids and other framing.  I found this one the perfect size, but I'm worried it's not strong enough to handle the weight.  I would only move it around my place and not on the road.  Still it appears to be just angle iron.  Any thoughts?

(https://forestryforum.com/gallery/albums/userpics/36921/417FFA64-7FD2-411D-8876-33858CE62B9A.jpeg?easyrotate_cache=1557266586)
 

Quote from: firefighter ontheside on May 07, 2019, 06:05:21 PMit's not strong enough to handle the weight.

Thanks Jeff.  Are you saying I answered my own question?  Lol.

what are the actual dimensions.  Looks like 4 hole wheels so prb. rated for around a thousand pounds gross.  We sometimes joke about (not practical) having a kiln that can turn to face the sun.  So a thought came to mind that with a swivel front wheel and a linear actuator or cable system you could "in theory" build a kiln that rotates to face the sun throughout the day.  the reason I asked about the size is, it may be enough trailer to at least be able to move the kiln, but not full of wood.  could put it on blocks or have 6 jacks or so around it to add support.  you still want a flat floor so the wood does not dry un-flat.  just thinking out loud. :)

Thanks Doc.  Yeah, I would only move the thing very rarely and then only empty.  I can get that trailer for maybe $150.  That would save me money over buying 6x6 skids and other treated framing.  I would definitely put a solid floor on it and insulate it.  I would put blocks under it in several places.  The guy said it's 6x14.  I would probably get rid of the springs and bolt the axle right to the frame.  Don't need suspension and lower will be better.

so now you can get a cut list of materials and check weight.  the axle should have a rated weight.  could just put a block above the axle to stabilize he loaded trailer.  the tires and wheels will have a weight that u can take x 2.  but off road can be that pushed a bit.  what is the angle iron size, 2 x 2 x 0.25" ?  the overall size floor plan is good for the solar kiln.  I would not run out and buy it, but does not hurt to explore on paper and on line,   :P  .  Its strength could be augmented with a frame to the floor for insulation.  we had a scout wood trailer and part of the frame was 2 x 4 wood.

It could be great for moving long planks as is.  fix up the lights if going on the road.  prob no brakes.  did the price move down?  Best regards FF.

I hoped you didn't notice.  200 is the asking price, but I would expect to only pay 150,so I changed it.

I use my 18' trailer for moving things, plus my dad has other farm use trailers.  We use those for moving lumber around.

 pc_smiley  I was just backing away from my "do not run out and buy it" comment.  thumbs-up

I'm not in a terrible hurry, so I'll keep looking for something a little better. I do need to build the kiln though.

Firefighterontheside,  keep in mind that currently the frame's load on the axle is spread over a wide area (the spring attachment points), and that attaching the frame directly would concentrate that load at one point on the frame, and that you will be increasing the load several times over the design specifications.

That's very true Tom.  I would have the thing set up with blocks at each corner and probably one on each side in the middle to distribute the weight.  I think that would make up for the change of axle mounting.

by adding the kiln framing that will stiffen the trailer. The axle is probably fine but you will end up with early spindle / bearing failure with the overweight stuff you want to add. my opinion, it will work. Question is how long. no matter what you need to have the same floor design with or without the trailer so as much as I like the mobile idea building on a trailer may not be the best idea.

I think I would look for bigger trailer orget a set of axleless spindles and bolt it to the side of the kiln.

(https://www.amazon.com/Timbren-Axle-Less-Suspension-Capacity-ASE2000S01/dp/B00R6KJ2YC/ref=asc_df_B00R6KJ2YC/?tag=hyprod-20&linkCode=df0&hvadid=316685777931&hvpos=1o5&hvnetw=g&hvrand=16486554115770545699&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9005646&hvtargid=pla-605158604782&psc=1)Trailer wheel spindles (https://www.amazon.com/Timbren-Axle-Less-Suspension-Capacity-ASE2000S01/dp/B00R6KJ2YC/ref=asc_df_B00R6KJ2YC/?tag=hyprod-20&linkCode=df0&hvadid=316685777931&hvpos=1o5&hvnetw=g&hvrand=16486554115770545699&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9005646&hvtargid=pla-605158604782&psc=1)

FF, I went to the amazon link provided by Crusarius.  The air bags also look cool.  could make a frame and 
wheel config that could lay on the ground like a low rider car.  could put blocking under and deflate the bags.  Maybe for movement around the farm, could also add some colored led down lighting!!! :D

Interesting idea.  I could have removable wheels.  When I want to move it I lift up the end with the tractor and put wheels on.  Don't really need a traditional trailer hitch.  

There ya go doc.  When people come to look at wood I could have the kiln jump up in the air!  Lower lighting would just be icing on the cake.

Quote from: Jeff on May 07, 2019, 06:07:43 PM

Quote from: firefighter ontheside on May 07, 2019, 06:05:21 PMit's not strong enough to handle the weight.

That about covers it for that particular trailer

I do like the air bag option better but I was linking for cost :) be very tempting to use those on the next trailer or sawmill build :)

ahh. thats better. apparently the forum didn't want to auto convert that link.

After operating the solar kiln for a while, I can't imagine dealing with it up in the air on a trailer.  Of course that's all individual choice.  If it's on skids there are lots of ways to move it - drag it, load it on a flatbed, attach wheels temporarily - whatever floats your gazebo.  It's best to have it on the ground when you're operating it.  If you build it on a trailer, you'll probably regret it.  Just my opinion.  Lot's of things sound good in the planning stage.  Beware of unintended consequences.  

and remember that you will need really good insulation in the floor at that point. if you have air flow under it, it will pull the heat out.

I considered the raised up situation and was trying to avoid raising it too high.  You may be right on that.  Likely I would never need to move it any way.  Probably just build it on skids like I originally planned.  Definitely will insulate the floor either way.  I found some walk in cooler panels that I may use somewhere....floor, doors, wall.

First post!

I am starting my investigation into the world of solar kilns.  The design in this thread looks very simple and efficient.

I have found some repurposed 4'x8' prismatic skylights
(https://forestryforum.com/gallery/albums/userpics/56054/Prismatic_skylight.JPG?easyrotate_cache=1561253658)


They are double pane and because of the design, they should capture more light in the morning and late evening.

Would they be a good choice instead of greenhouse plastic panels or double pane glass? They are $100 each and I was thinking of using 4 of them for a kiln 18 or 20 feet long.

Thanks,
Clint

Has anyone used the ZIP System OSB sheathing inside their kiln?  Prevents moisture and air infiltration.

Clint 

The skylights shown will indeed collect energy, but the part that is not getting solar input at a reasonable angle will be a source of heat loss, which will make the benefit much smaller or even negative.  

The key collecting area is the area perpendicular to the sun.

So...at 3am Saturday morning, a strong weather front moved through our area. We had major straight line winds at my home...caused my rear door to blow open and scatter pictures, breaking some glass. I thought a tree had fallen on us! Thank God it was just the door blowing open with no real damage. I walked around the next morning and discovered that my kiln had been blown off the piers it has been on since construction. I've needed to move it to another location for a while, and the Lord says it's time. Next week....
(https://forestryforum.com/gallery/albums/userpics/19339/9AD6E763-51ED-499E-AB35-F6E4A09AD9A9.jpeg?easyrotate_cache=1578881571)
 
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Wow, that took quite a wind to do that.  

Guess what?!! Nine years after building the kiln, the day finally came to test the trailer capabilities. It worked like a champ. There was no rot on the main support timber....yes! We jacked it up, and slipped on the tires, which actually held air after all these years. I backed up my '95 Chevy van  to it, and SLOWLY backed it to its new location. It will be fairly sunny in the new area, but not as good as where it was. By moving it though,
(https://forestryforum.com/gallery/albums/userpics/19339/07BF907A-971A-404A-B39F-7B0A93EA6A79.jpeg?easyrotate_cache=1579994366)
 
(https://forestryforum.com/gallery/albums/userpics/19339/75CFFE95-BEEA-411F-9CA0-8245CC09DD4F.jpeg?easyrotate_cache=1579994358)
 it's no longer sitting in the front yard...wife is happy! That makes me happy. We leveled it off and set it on concrete blocks. We then removed the axle and hitch, which was installed to be removed. It is now in it's own little kingdom, out of our way. Here is the new location:

(https://forestryforum.com/gallery/albums/userpics/19339/E841DEC0-4EC2-404E-8DB3-6E3E0687D192.jpeg?easyrotate_cache=1580051995)
 

Well, we're looking into building one now. 

Going back to the fundamental differences between the VT design and the PW/PM design, I think one slight advantage for the PW/PM is that concentrating the heat gathering on panels just below the windows means: You block the sun's UV rays from coming down onto the wood. Many species have the color baked out of them by being hit with UV rays, especially the special colorations we so carefully look for here....pink red cedar, rainbow poplar, ambrosia maple, and flame box elder. We get some very high prices for our wood, so keeping the color visible is important to us.

Also, we don't have to worry about painting the whole interior black if the panels are right under the windows.

You still want to seal the inside, helps keep the moisture from getting into the walls.  I used the aluminum roofing paint, then a coat of flat black.  You cover the top of your lumber pile with black painted sheets to protect the lumber from the sun.  Air dried wood has already lost a lot of moisture, is why some have fewer problems with moisture.  

The suns rays never hit the wood in the VT design.  A few pieces of corrugated black metal roofing is laid on top of the wood stacks to collect the sun and block it out from the wood.  

All kiln dried wood will loose the color on the surface of the top layer of wood fibers, even DH kilns.  However, the fade is only skin deep and a 1/16" pass through a planer will bring it back bright as ever.  

In solar kilns, I've only ever run the VT design, it's pretty much bulletproof.

The other design maybe just as good.  In general, solar kilns are Easy Bake Ovens, not much to do wrong.  I really like them.  

Eventually we hope to have a planer. For now, we have a lot of customers who don't understand that the coloration will come back. Our air-dried wood, carefully shielded from the sun, usually holds its color well, although it does depend what species we're talking about. The box elder holds its redness particularly well through the air-drying process. Not sure how it will do in the kiln.


(https://forestryforum.com/gallery/albums/userpics/22845/Ugly_box_elder_beautiful_flitches.jpg?easyrotate_cache=1604239624)

Recent cherry and rainbow poplar.


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(https://forestryforum.com/gallery/albums/userpics/22845/20201026_175508.jpg?easyrotate_cache=1604241471)

Well folks...I've had the kiln for a number of years. It's dependable to do the job cheaply and quickly. It heats up well and dries, in my case, a load of pine in less than a week. And remember, I built this thing for less than $500, since I used old tin I got for free. It's a great unit to have if you have a portable mill.

I agree.  We pulled a load of Paroda (Monkey Ear Tree) out of ours on Saturday and put a small load of live edged cypress in on Sunday afternoon.  The cypress will be the first green wood we have loaded it with but we expect it to do fine on the cypress.  I appreciate all of the guidance and advice on our kiln build.  On our next one we will use smaller fans and probably make the kiln itself smaller.

Do not forget that a solar kiln is a piece of equipment, so it is a business deduction.

Thanks, Doc.  It rode out another hurricane/tropical storm last night and continued to dry wood today.  I need to clean the poly panels and try to get the heat up.  We have some cypress that needs to get dry, pronto.  

Glad you survived again.  Let's hope this was the last one this year.

Have you started building an ark yet?

This most recent storm was not too bad.  It did not even blow any of the metal off of our drying stacks.  We have started using mule tape across the tops to tie the metal down.  We have some standing water near the mill but I hauled in a little fill dirt since the summer and the water will soak in within a few days (it'll stand long enough for a bumper crop of mosquitoes to hatch).

Thanks to all who have contributed to this thread.

Quote from: doc henderson on April 24, 2019, 01:42:12 PM
Thanks for the input and help Doc Wengert.  yes I respect the reduce, recycle and reuse concepts going on.  If we could build the perfect Kiln for no cost, our goal would be realized! :D  My favorite work saying is "we have done so much, with so little, for so long, I now think we can do almost anything with nothing!" :)  

First, I'd like to thank everyone who has contributed to this thread. I just stumbled onto it a few days ago. A friend and I are in the planning process of some sort of kiln, and I've gained a lot of knowledge here. Our biggest issue, at this point, is no electricity to run the dehumidifier.
But, what I wanted to contribute, is that Doc's saying did in fact originate in the military. At least, that is where I first heard it, back in the late '70s. However, he left out a line, or two. Here's how I heard it: "We the willing, led by the unknowing, are doing the impossible, for the ungrateful. We have done so much,  with so little, for so long, we are now qualified to do anything, with nothing." 

Lately, in our solar kiln, we have not been running the dehumidifier.  The past several loads have been partial loads, so we have only been running the fans for about three hours a day.  The wood seems to be drying flatter under these gentler conditions.

Last week when I took a load of sweetgum slabs to a local retail wood store the proprietor commented several times about how flat the sweetgum slabs were.  We have also started sanding a patch on most of the slabs to expose the color and grain before they go to be sold which is what I was doing this particular evening.

(https://forestryforum.com/gallery/albums/userpics/22883/77A80E4E-4587-443C-97F7-E7FAB1A4A39F.jpeg?easyrotate_cache=1642933772)
 

I have read that a good angle for the collector is equal to the latitude of the location. Some say to add ten degrees to that. Here, that would be about 38 degrees. I haven't been able to determine if that is measured from vertical, or horizontal. My first instinct is that it would be 38 degrees above horizontal, but that seems too flat. So, the more I think about it, I think it's 38 degrees below vertical. Which line of thought is correct?

It changes winter and summer.  so, 45° most places in the US is fine if you do winter and summer.  I think to max. in winter.  Remember what the good olé Doc @GeneWengert-WoodDoc (https://forestryforum.com/board/index.php?action=profile;u=20498) once told me.  "It is just a solar kiln!"  I guess i had a lot of questions. :)

The calc is from horizontal as stated in the second paragraph.  +10 degrees is better for northern latitudes with longer winters.  

The difficult explanation: Horizontal(0 degrees latitude) does not mean horizontal to the sun.  It means horizontal to the equator. As the earth is tilted on its axis, at different times of the year the equator will be a maximum of plus or minus 23 degrees with our center line with the sun.  For each latitude on earth, at only two points during our year is the equator exactly horizontal with the sun and that time is different for each latitude.

From the VA Tech guide to Solar Kilns:

Collector Orientation
A surface will receive the most energy if it points directly toward the sun (i.e., is perpendicular to the sun), following the sun as it rises until it sets. As such equipment to accurately (usually within 5 degrees) track the sun is expensive A simpler arrangement is to adjust the flat collecting surface so that it faces due South in the Northern hemisphere (or vice versa for the Southern) and is slanted at an angle so that at solar noon the surface is pointed directly toward the sun. Such an arrangement would have several adjustments ranging from + to – 23 degrees (winter to summer) around the base angle. The base angle is measured from the horizontal and is equal to the latitude of the collector's location. For example, a collector located at 18 degrees North would be tilted southward 41 degrees on December 21, 18 degrees southward on March 21 and September 21, and 5 degrees northward on June 21. Intermediate days would have corresponding intermediate angles.

Collectors that are not movable or adjustable can be set, for best year-round performance, at an angle (from the horizontal) equal to the collector's latitude. An angle of (latitude +10) degrees (that is, steeper) is suggested for best winter performance; an angle of (latitude –10) degrees (that is, flatter) is suggested for best summer performance.
In all collectors, the area of the top of the collector which is perpendicular to the sun (i.e., the area of the shadow made) is the critical area. It is not the area of the absorber underneath the top of the collector.

Thanks for the clarifications.

I'm thinking we will either maximize for winter (38 degrees plus 10), or just go with the simpler 45 degrees. If my math is correct, 45 degrees would pretty near maximize the winter performance. Gaining heat around these parts in summer should not even be a consideration! Most any building, with no collector at all, should be plenty hot!

We've had ours up for a year or so now. Just loaded it again today. We are still having trouble getting enough heat differential out of it.  It's been around 120° in there lately, but a temp diff of probably not more than about 50° from ambient temps. it is drying wood, though. We've been using it a lot for firewood, in steel baskets. It dries down split firewood in about 2-3 weeks, no problem. We also have done some lumber, with decent results.

Hello you all.
First of all,I wanna thank you for this tremendous Forum,
I have build an hybrid between the VT and Pineywoods and it works like a champ.
at this location RH average 70% and temp about 27°C.
the lat is 20, so we set an angle of 30 or so.
For the ceiling we have use glass in one of the kilns and polycarbonate for the other.


(https://forestryforum.com/gallery/albums/userpics/63824/WhatsApp_Image_2022-03-09_at_3_55_39_PM_28129.jpeg?easyrotate_cache=1646878802)
 

We add one LG inverter minisplit a/C wich has the super dehumidifier function and runs above 23°C


(https://forestryforum.com/gallery/albums/userpics/63824/WhatsApp_Image_2022-03-09_at_3_55_42_PM.jpeg?easyrotate_cache=1646878803)
 
(https://forestryforum.com/gallery/albums/userpics/63824/WhatsApp_Image_2022-03-09_at_3_55_39_PM.jpeg?easyrotate_cache=1646878804)
 
on the bottom vent we add a 10" fan, which runs once the temp is about 7°C higher than the ambient, and stops venting 5°C higher.

(https://forestryforum.com/gallery/albums/userpics/63824/WhatsApp_Image_2022-03-09_at_3_55_41_PM.jpeg?easyrotate_cache=1646878802)
 
the vent on top, opens when the H its 75% or so, depending of the month, and closes when its about 60% (it depends on the month)
by doing this, we allow the DH to work properly, and not to saturate the air, so it keep drying D&Nite.
the EMC Average during the year is 14% and we mostly work Parota. (guanacastle, guanacaste monkey ear tree)
I have had add some pictures, of the system.
im not an expert but it works faster, than a VT Solar Kiln, and a little bit slower than an nyle DH kiln, (we run a 250 model and a 450 aswell) but waaaay cheaper; upfront, operational, and maintenience.

Once again, thank you. and here are my 2 cents.

aromeza
Welcome to the Forestry Forum 
Looks like you are getting the job done. 
Link your pics to your post (you can do that by modifying your post and then click the "Click here to add Photos to post" button). 

Take a moment to read the forum rules at the bottom of every page. That should help out. Some explanation of what is shown in each pic would be great.

Shout out if you have a question. 

Welcome, Aromeza! It looks like you have a nice setup there!

Welcome @Aromeza.  Your setup is a lot like mine.  I don't have a Nyle or pure solar to benchmark against, so glad to hear you do, and can attest to the cost and efficiency of the hybrid kiln.

I took the time to document the original building of the solar dry kiln, along with a cross section that I've put on a blog post. I will not post a link, due to rules here though. I DID post a link to it on the Planman1954 personal website a few days ago...just search for it. Just look for the solar powered dry kiln post.

Interesting thread. Do I need to insulate the kiln being in the tropics, it's never under 20 celcius (68 Fahrenheit)here

Quote from: teakwood on December 04, 2022, 10:28:20 PM
Interesting thread. Do I need to insulate the kiln being in the tropics, it's never under 20 celcius (68 Fahrenheit)here

Don't really know. I've seen some Australian solar kiln designs that weren't big on the insulation. But they also have a drier climate in most areas...  Main thing in the tropics would still be to get the kiln temp up above the ambient, so the RH in there drops below 100%, and the wood starts to dry. Insulation probably isn't AS important because things are naturally warm with temps up in the better drying range already. But then it's also the increased temp that lowers the RH and speeds the drying. ??? :P 
Thinking out loud, drying down to US MC levels is probably going to be a problem without a DH style kiln? I haven't done the maths, but if your ambient is 25C @95% RH, how much do you need to heat that air to achieve an 8% EMC? And if you don't control the moisture when it comes out of the kiln, it's soon going to bounce back up to 15+%

Average temp is 27, at least.

I don't need 8% EMC, our wood stays within 12-16% between dry and rain season. so if i get under 18% i'm already good for outside decks and maybe 14-15% for furniture wood. teak is extremely easy to dry, with some wind and a little dry air it air dries under 25% in no time.

I have some insulation laying around, can use it on the walls, the roof isn't insulated anyways with the plastic sheets on it. does the flor needs insulation?

I will go with the enclosed design where you put a dehumidifier inside, so that thing will suck all the humidity out of the wet air and wood.

you are trying to decrease the surrounding (inside the Kiln) RH so you need the interior to be hotter than outside.  As mentioned, this will drop the RH.  the insulation will allow for a bigger temp difference by holding the heat inside the kiln longer achieving a higher temp and lower RH.  In theory.  the goal is to speed up the process, so a higher temp gradient and or lower RH is what you want.  Adding the DH is not a bad idea since venting to the outside and entraining air from the outside at 95% humidity will slow the process.  Or do the venting during the day when RH is lower, however the water content is prob. the same and lower RH is lower just due to increased daytime temp. outside.

Dehumidifiers do not remove remove moisture from the wood, they remove the moisture from the air.

High local temperatures and high airflow velocities or 600 fpm our above across the lumber stack remove the moisture from the wood, until the air gets saturated.

It's a two step process.  Moisture from wood goes into the air, then the moisture is removed form the air.  Or the air is removed form the control volume and replaced with dry outside air.

The efficient way to remove moisture from air is not through a dehumidifier, it's by removing the air itself through venting.  That's why DH kilns like Nyle that are rated to dry 4,000 bdft of hardwood (slow moisture removal rate) can only dry 1,000 bdft of pine (high moisture removal rate), the dehumidifier gets overwhelmed and is the limiting factor.  In those cases it's more efficient to just turn the DH off and simply open the vents and let the air out.  Instant dry air.     

For highly moisture laden air, the best alternative is to vent the air outside.  That's why a solar kiln is very effective but also very slow unless there is enough solar energy to reheat the incoming air quickly.  For highly moisture emitting wood, with lots of air transfer, the solar collector needs to be resized to be much greater than the conventional Va Tech 10:1 ratio.  Big building, small load size = inefficent.  So increasing the solar collector size allows and increase in airflow and an increase in venting.

At the moisture levels you are talking, you need high heat input, high airflow velocities and increased venting, non of which happen in a solar kiln or even a DH kiln.  Since you are not going down very far in moisture, a lumber pre dryer would be more appropriate than a conventional kiln.  

Solar kilns only dry during the day.  So 50% of the time, they are non functional. 

In order to optimize the drying rate and cycle, the maximum allowable moisture removal rate of the wood must be reached but not exceeded.  Solar kilns are optimized for slow drying wood, so are DH kilns. 

Quote from: Planman1954 on September 16, 2011, 10:52:07 AM
OK...back to work on the kiln, after a long hot summer. Sorry for the long delay, but had some other things to attend to. The Kiln is now completed, and ready for a test run.

After attaching the top plastic panels and completing the wiring for the fans and dehumidifier plug, I ran some blocking between the front beam and rafters and made a framed box for the two fans to rest:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-09-05_12-56-51_419.jpg)

After the fans were set in place, I began installing the metal panels under the rafters. Remember, the metal pieces are centered between the top and bottom of the rafters, creating about an 8" space at the top and bottom for air to enter and exit. You can see the first few pieces in place behind the fan above. I used dry wall screws to hold them in place. Of course, the black painted side is facing up. Here's a photo showing the metal installed around the fans:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-09-06_10-33-38_879.jpg)

After reaching this point, my buddy Jimmy came by and took a look and suggested that I seal off the area between the fans to create a plenum, or a mini attic inside to direct the air flow. This shows a picture of the boards filled in between the fans with insulation above:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-10-15_10-33-52_856.jpg)

And then a photo with my camera held really high to show the insulation laid on top of the boards:



(https://forestryforum.com/gallery/albums/userpics/19339/3018/Resampled_2011-10-15_10-34-08_674.jpg)

After these photos were taken, I filled in the end areas.

I have some questions now that you have lots of experience  @Planman1954 (https://forestryforum.com/board/index.php?action=profile;u=9339) .
the space between plastic roof and black metal is just 4"? would that be more efficient with 6 or 8"?
How do the normal store fans hold up? can they take the heat? the space between wood pile and north and south wall is 1' , 30cm?
thanks 

anybody can help me out real quick with the questions above? i'm drawing some plans for the kiln and need these measurements. thanks @doc henderson (https://forestryforum.com/board/index.php?action=profile;u=41041) 

teak there are plans for the one developed Virginia tech.  usually, the fans go above the wood and have a tarp to create a dam, so the air goes through the pile.  final dimensions can be modified to fit your space needs ect.  

Design and Operation of a Solar-Heated Dry Kiln | VCE Publications | Virginia Tech (https://www.pubs.ext.vt.edu/420/420-030/420-030.html)

@GeneWengert-WoodDoc (https://forestryforum.com/board/index.php?action=profile;u=20498)

fairly detailed plans are at the end of the document.  You could just go all dehumidifier kiln as well.  I think in your unique environment/weather the combination makes sense.  I would set it up with a bucket to tally the daily water output.  to save on electricity you can then limit the DH use when the water drops off.  like run it at night when the kiln RH is higher.

Thanks doc, I will go with the design used in this topic, the one pinewood and planman built. I think the black roofing sheets underneath the plastic panels will heat up to a extreme and should work pretty good. What I can't see anywhere is how much needs the distance between plastic sheet and black metal sheets be? You have the rafter between so what's best, 4,5 or 6" ?

Where do I get a good DH? I only found modern household dehumidifier. 

My understanding is having a black metal under the glaze combined to make a "collector is no better than having all the surfaces flat black that will receive sunlight.  However, the idea that super heating (relative) the wall that is next to the outside temps. seems to make sese there may competing losses out the wall through that insulation.  heat transfer is based on temp gradient vs. insulation.  so, heating a metal "pan" sheet metal under the glaze, and radiate heat to the interior from both sides makes some sense.  If it is fastened to the underneath side of the studs, it can make a plenum and can have convection forces, and well as indirect or direct forced air.  There are plans/ideas where with a plenum, the collector can be turned on and off to decrease losses after the sun goes down.  I recall one where there is a large (made from board foam) flap that creates a one-way valve that is pushed open by the fan that circulates air through the plenum/ducting.  

The best option for a DH is to go all out and get a Nyle DH.  The home ones are ok for a while (especially if used intermittently) to maintain moisture in dry lumber, or to finish off relatively dry (air dried to 12% here) lumber in say a container.  I have used the same Walmart DH (70 L a day rating) for 5 years, but it mostly gets turned on for a few days a month to maintain dry wood in a container.  Home model will also not have the capacity to move lots of water (usually rated in pints or liters) as a pro model.  It gets more complex when you try to do the hybrid style kiln.  As an example, if you will use added heat, a solar kiln loses lot via the plastic glaze.  you could cover at night with insulated moving blankets as an example. or close off the solar heat chamber, but then the underside of the metal pan must be insulated.  Most forms of drying will take some energy and therefore money.  all have advantages and disadvantages.  I would break it down by what you are investing in.  

For the heat component, you need good seals and insulation.  used to mobilize water from the interior of the wood and to lower the relative humidity of the air in the kiln.  Plastic glaze will increase losses when the outside temp is less than the kiln temp.  Heat can come from solar, or a heater that can be electric, gas, or any carbon fuel including wood scraps.  you need heat if you want to treat wood for bugs (sterilization).

Dehumidification requires electricity and good seals to control WB depression or relative humidity.  You could get one to run on LP gas like for a camper, but it would be more expensive up front.  It may have to be a system designed and constructed as a one off by a heating and air guy.  a commercial DH has coils coated to handle the chemical laden condensation it deals with.  you can measure losses via the water output.  It dries the air, so you also need air circulation to allow the dry air to reach the wood surface and change the liquid water to a gas (water vapor).  At over 100% it will rain inside your kiln, and on cooler surfaces like glaze at night you will get condensation.

air circulation is needed for all kilns to prevent mold and facilitate water coming off the boards.  also need good stickering and baffling.  It requires electricity (solar, wind, grid, generator and therefore fuel).  air drying uses the weather.  do you get much wind?

solar kiln is the cheapest and requires little energy input.  If you buy a Nyle dehumidifier, you may as well just build a regular container and skip the solar.  If you have to run a generator for electricity the combined/hybrid, then that cost is also a consideration.  I think your local weather is unique, and I invite anyone else to chime in.  I think the hybrid is good to help with the high relative humidity.  Even though the measured relative humidity is "relative" based on temp., the water content of the air remains the same unless you vent and bring in dryer air.  a DH removes water content and drops the RH.  With a hybrid solar/DH the RH will go up at night when it is cooler and may increase the efficiency of the DH although its capacity could be exceeded.

as far as the gap, it depends on if you want the "duct" effect to force air over the surface.  If you fasten it to the bottom of the collector studs/rafters, then you have to eliminate the bridging, or make it smaller dimension.  you could just suspend it below the rafter to receive the suns energy and let the overall air movement of the kiln take on the heat.  I will stop here, and I hope I addressed other questions you have.  I hope others will chime in.  I do not have a solar kiln, but have studied them for prob. 15 years now, and love the concept.  

(https://weather-and-climate.com/uploads/average-relative-humidity-costa-rica-limon.png)

(https://images.climate-data.org/location/999068/temperature-graph.png)

Heating air to lower RH and EMC in Drying and Processing (forestryforum.com) (https://forestryforum.com/board/index.php?topic=103455.msg1607644#msg1607644)

Temperature change and its effect on wood | Woodworking Network (https://www.woodworkingnetwork.com/magazine/fdmc-magazine/temperature-change-and-its-effect-wood#:~:text=If%20air%20at%20100%20percent%20RH%20and%2050F,and%20at%2030%20percent%20RH%2C%206%20percent%20MC.)

there are many good articles about wood drying.  I think that Gene mentioned that if you can raise temp in the kiln, by 10 to 20°F, you will get a lower RH that will be enough to dry wood.  there is a national hardwood lumber ass. (NHLA) that Gene has webinars on that you can watch.  you will need to vent at night, or your kiln interior will be soaked in the am.  puddles of water on the floor, and leaking under walls and doors, is not good for a wood constructed kiln.  thus, good vapor barrier and sealing wood components, is important.  Is it cloudy most of the time?  I see in the rainy season, it rains every day, if only for an hour.  In December, it is the dry season, but the temp and relative humidity stays about the same, but at least I assume you have more sunlight.  I would guess that your kiln RH will exceed 100% almost each night without venting or the DH.  Do you have cheap electricity on site?  If not, I think a straight solar kiln would be good.

Quote from: doc henderson on December 11, 2022, 10:15:37 AM
(https://weather-and-climate.com/uploads/average-relative-humidity-costa-rica-limon.png)

(https://images.climate-data.org/location/999068/temperature-graph.png)

this is from Limon, that's in the Caribbean, i live in the pacific north, it's warmer here (80, 28celcius average) and it rains less 70% average humidity.  January-May is dry season, very windy and hot, up to 105, 36 celcius with a 60% humidity, it's when you can air dry 1" boards in 2-3 month, the kiln will shine in this conditions. the question is how will it preform in the rain season with warm humid wether, it gets pretty cloudy too   

Quote from: doc henderson on December 11, 2022, 10:45:43 AMI would guess that your kiln RH will exceed 100% almost each night without venting or the DH.  Do you have cheap electricity on site?  If not, I think a straight solar kiln would be good.

The DH will be a must i imagine, good fans at the day and DH at night or 24/7. we have relatively good electrics, i have good conections to the grid, i have 3 services, it's not actually cheap but it's more or less a stable network (10-20 cents/kwh, depends on your consumption) the electricity doesn't concern me, it's just fans and a DH. I make money of this lumber and the kiln will increase productivity and my income so the costs are absorbed.
i have a solar equipment dealing friend, so in the future i could go that route. 

Quote from: doc henderson on December 11, 2022, 10:15:37 AMhe question is how will it preform in the rain season with warm humid wether, it gets pretty cloudy too  

It won't.

Solar kilns need solar to work.  When they get direct sun, they work OK, when they don't they are no better than an air drying shed with fans.

Solar kilns don't work in the rain.
They don't work at night.  
Under cloudy skies, it depends how much infrared radiation is getting through the clouds to the ground, but if the air is already humid and warm, then it will only be marginally better than an air drying shed.

If you want to see how it would work, run a simple test.  Put a black piece of sheet metal outside, protect it from the rain, and see if it gets enough solar radiation to heat up.  If it doesn't heat up, a solar kiln won't either.

I would guess shipping would be high, but a nyle DH would be first class.  I think solar Heat) could add to the process but is slower and no heat at night.  sounds like you have good air-drying conditions other than humidity and the rainy season.  can you get containers easily?  going with the container and a nyle system would set up fast, and prob be faster overall.  I think at your temps the DH would heat the kiln.  you might have a call with Stan (Kguy) and see what he thinks.  I have no personal gain from that.  good luck, it has been a fun discussion.

as I was typing the prev., I had to hit post twice as YH was also typing.  He has solar kilns and Nyle stuff.  A solar might be ok, but the hybrid requires lots of thought (what we have been doing), More complex design, and the solar has net losses at night.  If it is affordable, it may be ahead to go straight DH.  The design by Dr. Gene Weingert is great for the hobby guy and even professionals like yourself.  Nyle has plans for a stick-built kiln for their DH also.  see the sight at the left of course.   :)   I have been watching the 200 level units, and even thought about getting the premade kiln box.  

If you go to the Nyle site.  click on resources, then manuals, then pick a DH like the L200.  it shows detailed drawing and speaks to design.  they can also tell electric use for a load to dome degree so you can be sure that it makes financial sense.  Of course, you got the quarry going so you seem to do well with these decisions.  good luck.  solar is still a neat way to go, but adds complexity, and may slow you down.  As YH mentioned, may not add that much to the process.  You could also do both separately.  

Thanks a lot for all the help, i did the math for a container and a woodmizer 250, same as Nyle 200, it comes to at least 18-20k, that's too steep for me.
have seen a guy here with a 40foot container and a 250 in it and does aprox 4000bft in 22 days, but 500$ electricity bill.
thats too big for me, i can't keep up with felling, sawing, drying, processing, selling and the quarry. i will never have a 4000bft load. if i can get 1000bft per load in a solar that's enough, the rest is airdrying and waiting for the kiln.


you say DH like the Nyle200 but in my understanding they also heat. i just need a dehumidifier for the solar so the water goes out. if i need to add heat in the rain season i do some kind of firewood stove.

but i would love to have a more industrial dehumidifier, nothing big 

decisions only you can make.  good luck.  Nyle has an L53, but they have not been available for some now, unless that has changed.  but that may be better than a homeowner one.  Mine is a 70 L per day from Walmart and was about 300 bucks.

I have two solar kilns with ~1500bf capacity each, based on VT design, with temp-triggered (or phone app triggered) louvered exhaust fans on east and west ends.  I use Honeywell residential DH's, about $350 each.  If your lumber economics are as solid as they appear, going through one or two of those a year doesn't break the bank.  They can wring a LOT of water out of the kiln in the early drying, circa 5-10 gallons per day per DH.  Their operations also throw off heat, which is beneficial, right?  I also use a linear array of 5" computer fans to recirc internally.  Check my other posts for graphs and details on the performance.

wkf94025 (https://forestryforum.com/board/index.php?action=profile;u=54567) that sure would be a kool build to see. Any chance you can do a build thread on your kiln setup?

Kiln heat controller in Drying and Processing (https://forestryforum.com/board/index.php?topic=120021.0)

I'm getting the plans together for the solar kiln. I like this gizmo so I can program by which temperature the fans start. What else do I need? Power vents for exhaust air or just manual? Could be controlled by this controller depending on humidity

https://www.ebay.com/itm/114884966273

No controller necessary for a solar kiln.  The vents are separated, 2 generally on the pressure side, 2 on the vent side, so 4 total with 2 mounted high and 2 mounted low.  I used plastic $20 foundation vents that slide open and closed.  There is no need to do anything other than make manual adjustments.  A solar kiln is the Easy Bake Oven of the kiln world.  If the inside is real hot and muggy, then you are not venting enough moisture so open the louvers a little more, if the inside is cool or only warm then close them a little.  If the inside is hot and dry, then the load is done.  That's pretty much it.  Don't let it get so hot inside that you burn the plastic roofing material, that's about 160F.  Been there done that.  

Once you get the feel for your consistent load size, then the vents need not be adjusted for weeks if not seasonal.  The fans I use are 2 Wal Mart box fans, $20 each, set on high.  There is no need for a vent controller or a temperature controller, a solar kiln isn't rocket science, it's too easy.  It just works, if you have sun.  I've told Gene this, it's one if the most elegant and simple designs possible, and it just works.  It like a bowling ball, it's simple, it works, don't overcomplicate it.  

Remember that a DH kiln works 24/7 and are being used to dry wood right on the maximum allowable drying rate curve, so controllers are necessary.  A solar kiln only works during the daytime so it's duty cycle is already cut in half, and at night the temp drops and the humidity comes up and the wood equalizes and cools.  That eliminates the issues of case hardening, stress relieving and pretty much anything else.  Just copy the Gene's Va Tech design and it will work.  2 layers of transparent plastic for the roof, one outside, one inside.  Paint everything flat black, inside and outside so the kiln itself become a solar collector. Use a plastic tarp dropped down on the wood stack as a baffle.  I use a couple sheets of corrugated roofing metal, painted flat black, laid right on the wood stacks.  Put the wood in it, put the metal on the wood, close the door, crack the vents, and walk away.

During the rainy season, close all the vents and put a $160, 60 quart Wal Mart dehumidifier inside, and set it for continuous on with a drain hose.  I used to put mine right on the lumber stack and plug it in.  It will last a couple years and die, so get the 2 year replacement service contract for it.

Don't get me wrong, you can make a solar kiln very complicated, but Gene designed it for simplicity. I've been running one for 15 years, 24/7.  Well 15 years, 12/7 anyway, unless there is a bright moon.

Seriously, it's no more than a black car parked in the Mall parking lot in the summer heat with a load of wood in it.  So crack the windows a little.  That's pretty much it.....  

As I think I previously mentioned, our kiln does not get as hot now as it did when the poly panels were new and clean/clear but it still does a good job drying wood.  We don't have any vents in ours but when the wood has high moisture content, we leave the doors slightly open.  When the MC gets lower, we close it up and let the moisture get out through the leaks and I generally open the doors for a few minutes in the heat of the day to purge the moist air.  

This afternoon around 5:15 it was still 80° in the kiln and the load of cypress that was put in about two weeks ago is considerable drier. 
(https://forestryforum.com/gallery/albums/userpics/22883/CB9A5384-9AF9-4326-B6C7-C3EF74290FC8.jpeg?easyrotate_cache=1671849782)
  I took this picture after opening both doors for a short time.  The doors are still slightly open, maybe 1/8" gap.  On this load of cypress, we have been running fans continuously.