solar kiln idea

[metalspinner]

Hello, everyone!
  Here are some pics of my solar kiln.  I've dryed about seven loads of mixed hardwoods in it over about 3-4 years.  The drying went very well.  There was little to no degrade.  It holds about 1500bf.
 The only problem I have is the amount of time it takes to load.  By myself, it takes at least a full day.  That is unstacking the air-dry stack and moving it to the kiln then stacking in the kiln.  I have no equipment to move a stack of wood at once.  The hardest part is when the stack gets high and I have to climb into to kiln through the little opening with an 8/4 board and not mess up the sticker alignment.  Then, I have to get all that block up there .  What a pain!






  So, this is my idea....
  Can there be a modular system that you erect around an air-drying stack?  Let's say three foot wide interlocking panels.  You would build your stack on a sheet of plastic to prevent ground moisture from entering, then when you are ready to kiln-dry it, you simply erect it around your pile.  When that stack is dry,  just disasemble the kiln and erect it around the next pile.  This whole system can even be stacked onto a trailer and taken to a buddy's place to dry his pile!
  I can't be the first person to have come up with this idea.  Anyone have a working model they are willing to share.

[Ga_Boy]

Nice set up.

Got a question, how do you check moisture content?

I noticed you mix thickness; 4/4 and what looks to be 8/4 material.

As to your question, I have not heard of a modular design, but where there is a will there is a way.  If you do this make sure you position your air dry stacks such that you get goos sun coverage when you put the kiln up.


Mark

[beenthere]

Neat looking system you have there. And your kiln sticking job is superb, and obviously a lot of work as you say.

Maybe a track (rail) system to move the stacked lumber into (and out of) the kiln, or put the kiln on the track and move it.

But if a modular kiln, that is portable and maybe attached to a base that the kiln load is stacked on, could be designed, that sounds intriguing too.

[ronwood]

Might try this link http://my.execpc.com/~tmbrgrn/page50.html. Interesting way to do it.

Ron

[metalspinner]

Well, I was just out driving around which gave me time to think.  I think the portability of the modular design is it's biggest advavtage.  As a foundation, one could use 6x6's leveled up around the perimeter of the pile and staked to the ground.  Then two modules screwed together at  corner, then from there just screw it together all the way around.  If your fans were integrated into a module,,they could be placed where needed and run off an extention cord.
ronwood,  That is cool.  But is way to fancy for what I need.(personal use)

bennthere,  Thanks for noticing.  My wife just roles her eyes at me when I point that out.   I just planed all those sticks to a uniform thickness.  Hopefully it make all the lumber just that much better.

Ga-boy,  The glass panels on each side of the kiln come off.  I ran some wires with alligater clips on each end to a couple of finish nails at several layers within the stack.  I just take the door off and hook up to the clips.   Good point of direction of the air-dry stack.  That wuld have been one of those hard earned lessons.

  I would have rathered put the 8/4 on the top, but they were just to heavy to squeeze in at the top.    Most of the lumber in there is quartered red oak.  It will take a long time for the bottom 8/4 boards to dry!
  One more pic for fun.  This is American Elm.

[jon12345]

Stickers should look 'pretty' in the stack, even air flow = even drying (theoretically)
 

How many stickers/ length of wood do you use?

[Dan_Shade]

i like it.  how hot does it get?

[metalspinner]

Jon,  Two foot centers have worked so far.  I haven't had any wood that was to troublsome yet.  Namely -  Sweetgum.  That should have 16 or 12" centers I've read.

Dan,  My temps are only getting to about 130 degrees.  I think I will add a second roof layer this spring to try and get the temps into bug-killing range.
Some insulation on the back wall may be in order as well.

I built this thing by the seat of my pants.  I wish I had done some research before I jumped into it.  This forum would have made the learning curve much easier.  When I add the second roof layer,  the angle will be steeper to capture more sun.  That should bring the temps up a bit, too.

[Chet]

Painting all the exposed interior surfaces black, will also help raise the temps.

[brdmkr]

Clegaux,

Would you mind sharing the overall dimensions of the kiln.  Looks to be about 4' wide and 16' long, but photos can be misleading.  Also, how long does it take for a load to go from air dry to KD?

Thanks for sharing pictures.

[metalspinner]

Brdmkr,
  The kiln is 16' total length.  I simply went as long as my free windows would take me.  Unfortunately, I can't put 16' worth of lumber in it.  I should have went an extra foot or two in  length to get two 8' stacks in their.  It is four feet wide, six feet in the front, and eight feet in the back.  If you look close at the first pic you can see two attic fans.  Maybe I will add one more of those this sping.(?) 
  The length of time varies, of course.  This year we had very little rain here in TN, so we had Many bright sunny days.  Last years winter load finished in April,  then I dried two more loads by the end of October.
Truth is I have no more room in my shop, so I will not be in a hurry to get the oak out of there.   I'm guessing it will be done by mid-June, though.

[Randy]

Clegaux---------Like your kiln---I was thinking of building a Solar one similiar for my personal usage, you said you wish you had of done more research---any other Ideas you want to pass on about your design other than what you have already mentioned?? I already have idea's on loading from the rear to make it easier, insulate, painting interior black, etc. Would you double your glass??

This question is for everyone---------Is using the glass on the roof and all walls except for the back better than just the roof??

Now, I need help in drying BAD------I have read DR Gene's pages, but it still leaves me with alot of question's. I want to dry on a small scale, like 1000/1500bf, so I don't want to waste my money by over spending, but want products that will work. Some Question's.

1. How is the best way to measure the moisture in the kiln and where to get it--any links??
2. How is the best way to measure moisture in the stack--I know Cleqaux uses nails with wire's attached, but what type of meter is the best for small scale to hook to these wires and where to purchase it--any links??
3. Do most of you watch moisture meter and manually turn on fans/open vents as needed or is there some kind of device for "Home" usage that does it automatically that doesn't cost a fortune?
4. Isn't it better most of the time to allow the wood to air dry before being put in the Kiln--if so to what moisture before putting it in the kiln?
5. I have seen 2 pin moisture meters on E-bay for around $20 to $30 bucks-------Do they work or is it a waste of cash and I would be happier if I buy THIS meter or THAT meter?
6. When lumber is dried-----where is the best place to store it--like Inside a building OR------------also is it better to flat stack once dried or air stack???

Now all this reading on here and like with Dr Gene helps but I am still confussed-------Can some of you that know tell me some simple direction's on how to Solar Dry. Like when the moisture gets to "Here" open vents till it gets back to "Here" Or let the fan's run during "THIS" time----"OFF" during this time--Off at Night ---OR------watch "THIS" --"LOOK" for that----You know Just the Basic's----Then I can work from them directions. I have never been to /or seen a Kiln---So I know nothing.
 I have alot of glass panels from sliding glass doors, have some solar panels, and batteries some 12" 12 volt attic fans-----this kiln will never see Grid Power, so you need to keep that in mind. If I can dry a load every few months--It will be OK.

I feel I don't need much of your time on Building design---------Just some of your time on how to get and set-up meters and operate when I get the Kiln built. Thanks So Much!! Randy

PS If you would feel better you can send me a private message. Thanks

[metalspinner]

Randy,
  It is very difficult to screw up drying wood in a solar kiln.  About the only thing you can do wrong is put in green lumber.  My experience has been that the lower the MC to start, the less defect when dry.  Also, you will not tie up your kiln for longer periods of time if you put in air dryed lumber.
 
  My moisture meter is the Timbercheck.  This meter is mid-range on price and comes with very good directions.  Since I began using the nail and wire method, I haven't had to replace the pins.  That being said, buy extra pins for your meter so you can get on with things when you break the originals.  Also make sure to make your species and temperature corrections when you do your checking.  The timbercheck is calibrated to Red oak.  I believe all others are set to Douglas fir. Check yor MC in the morning before the sun has a chance to warm things up.  This will eliminate one of your corrections.



 The attic fans in my kiln came with a thermostat to turn them on.  Just set them to 30 dergee's above the daily high and they will take care of themselves.  No need to watch the weatherman every day.  A monthly re-set should be good enough.

  The best place to store your dryed lumber is in a conditioned envirornment - inside.  Dead stacked and standing on end is the way I go.

  The sun will control your drying schedule.  During the day  the box will heat up.  The fans will come on.  The air will circulate removing moisture from the board surface and expell that air out of the vents.  At night, the box will cool down, the fans will turn themselves off, moisture will move from the center of the board to the outside of board and the next day the cycle will repeat.  To get down the last cople of percent I close the box up tight to raise the temp to maximum.  This seemed to help move that last little bit along.

  This natural cycle is why it is difficult to mess up with solar drying.  The only downside is if you need lumber in a hurry.  But because it is for your personal use,  you will not need to worry with this.  Soon enough you may have my problem of running out of space in your shop to store it!

  Lumber can be left in the solar kiln indefinately.  It can not be "overdryed" in the solar kiln. One more thing that I added in my kiln is an "indoor - outdoor"  digital thermometer.  $10 if I recall.  Set the unit up high in the kiln out of direct sun and run the wire sensor down to the bottom to get a reading down there.  This lets me know that  I am getting good air circulation from high to low.  This model also tells you the humidity in the kiln.  Pretty cool for ten bucks.





  The one downfall of using Glass for the kiln.  A hail storm is my biggest nightmare.  The rock the did this was the size of a golf ball and shot out of the lawnmower about 120 feet .  Some window tint from the auto supply store was a quick fix.

[metalspinner]

Randy,
  One more thing.... When building the "deck" of your kiln go heavy on the framing.  1500bf of oak with all that block is very heavy.  You may notice mine has a slight sway toward the center.  I will fix this when this load comes out this summer.

[jon12345]

A big concrete foundation might help, as  a heat sink and also support for all that weight   

[Den Socling]

1500 bf of oak at 25% is around 5600 lbs. If wet, it could be 7500 lbs.

[Dale Hatfield]

I read on the Net somewhere Is Wisconson That that have a solar kiln set up with air drying stoarge built with the kiln .It was a very nice set up on concrete and roller carts.Im pretty sure they were sawing cants to make hardwood flooring.
Dale

[stumpy]

Yes Dale, I'm from Wisconsin and spent a day at Timbergreen farms. He has designed a very efficient solar kiln that incorporates air drying sheds. He has 3 huge kilns in operation now. You can see them on timbergreenfarms.com

[Randy]

Randy,
  One more thing.... When building the "deck" of your kiln go heavy on the framing.  1500bf of oak with all that block is very heavy.  You may notice mine has a slight sway toward the center.  I will fix this when this load comes out this summer.

Thanks for the info. I Thought this was neat---I was telling my traveling salseman that I was planning to build a kiln----he said you will need a moisture meter(mm) for measuring the moisture in the wood---I told him I was watching some on E-bay and ask if he was familiar with a kiln---no experience, but he used a mm when he was working with a extermanator(?)-----and said he still had it. He called me the next day---2 states away and told me I could have it and he is UPSing it to me(free)---I should get it monday--------hope it works---he said it worked when it was last used and said he had removed the battery when he stored it and it has 2 probes and get this-------he has had it for 43 years---been stored for 41 years. Wonder if it will work for me.  Randy

[metalspinner]

43 year electronic technology.... I wonder how large the UPS package will be?
I am sure it will tell you a moisture content, but I wonder if he sent the correction tables with it.  Good luck!

[Randy]

43 year electronic technology.... I wonder how large the UPS package will be?
I am sure it will tell you a moisture content, but I wonder if he sent the correction tables with it.  Good luck!

Got it-----leather case and all---it seems to work good, not alot bigger than a pack of  100's cigarettes. It is made by Delmhorst, it is their PC-1 model, but here is the down side---it has 5 LED in ine on the front with a range of 10 to 20 and one LED lower marked LB---low battery is my guess. Do you think I could use this--or do I need one with a wider range--lower than 10 etc? Thanks Randy!!

[metalspinner]

Wood used inside should be dryed below 10% in most cases. 6-8% is usual. A meter that can read in this lower level will be best for furniture grade lumber.  Although, if you are using a solar kiln and are not in a big hurry, just load the kiln and wait.  Weigh a couple of boards along the way and when they stop losing weight, they are as dry as they will get.

[Randy]

Thanks--I been playing with it---I found out if it is fresh cut/wet wood and above 20%---all of the led's will flash fast, also by using two screws--screwed into the wood real close but not touching using wire jumpers-- I can take a board with a barely 10% reading and make it read 13 to 14%--which I realize is throwing the meter off, but could be a way to read at a lower level------I think I am going to play with it on my first load--its was free and I like free---if I can make it work. I don't know how close this meter is to being accurate ---I am getting reading's of app 15% on air dried lumber that has been drying for a year---and those readings were taken sticking the probes into the middle of a board as far as I can get without tearing into a pile and getting boards out the middle. Boards that I got from Lowes and nailed up under a shed two years ago, but not where they get wet--I get mainly 13%, my inside work bench made out of 3/4" plywood will barely light up the 10%. Does it sound close?? Thank Randy

[brdmkr]

I'm with you Randy.  Free is bettter than cheap

[beenthere]

You should get a chance to check its accuracy when you take some samples and oven dry them, dividing the difference in weight green to dry by the dry weight. That will tell you the accuracy of the readings. Sounds close so far. And above 20% is 'wet' yet. Plywood with glue lines may give you odd readings, just like across cracks in the wood.

[SPIKER]

I've built industrial ovens for the past 15 years.   so with this info and the easy is better this is what I was thinking I would do first.
1. get one of the inexpensive car houses, that are made from light weight tubing & covered in plastic/tarp like material, this would be used to cover the pre-stacked pile for air drying prior to completely covering it up for solar effect, there is a zippered end door in them already & are pretty rain tight.   using solar fans (advertized now for green houses & attics.) ( like this one  http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=6029671629&ru=http%3A%2F%2Fsearch.ebay.com%3A80%2Fsearch%2Fsearch.dll%3Ffrom%3DR40%26satitle%3D6029671629%26fvi%3D1 ) or better this one ( http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=6030106312&ru=http%3A%2F%2Fsearch.ebay.com%3A80%2Fsearch%2Fsearch.dll%3Ffrom%3DR40%26satitle%3D6030106312%26fvi%3D1
)



 which run for X hours on the stored suns energy.   place one or more inside the kiln for circulation, then mount more for exhause.   modified one with a thermostat should be easy enough to turn them ON/OFf when sun is hottest or when it colls to shut it off. (not sure they may have this built in)  cost for these are ~30 bucks each. 

the wood can be left in place the drying shead picked up off the top, (or dissassembled) and one with clear sheeting put in it's place.  while it is not glass and would be subject to high winds if not secured well it would be easy to put into place.  and the stack can be checked often.   

I don't know if this would work but it sure would help the air drying process I would think...   

the sliding glass doors would work great if you had access to them...   lots of surface area & could be made with wall sections.  7' high by x feet wide.

the roof could be mounted on one (back side with poles into ground so it stays vertical or made with the floor as a ridgid section to prevent wall & roof movement when roof is raised) so it hinged up/down.   raise the roof up & prop it up for loading & unloading, then put end walls in place & last south side wall in place with screws & lower roof back down on top, air gaps are needed anyhow for air exchange so keeping it really tight is not needed.   sponge rubber could be used to sealing when it is winter out for higher heat in full day light...   the solar vents would be useable year round for free energy after bought first time.   a larger 12 unit could be made with 12 volt battery for days when sun is lower and keep a charger on battery and use the thermostat to turn on/off...


anyhow just thoughts from someone who doesn't know how solar kilns work, only gas fired kilns for pottery that are 2500 degrees F running 10' wide and 100 + feet in lenght and batch ovens in the 250 deg F + range...


mark M
mark M

[D._Frederick]

clegaux

FINE WOODWORKING magazine had an article on using patio sliding door windows to build a kiln simular to what you built. If I remember correctly, it was an early eighties issure. I built one and used it only one time, it ruined a load of ash that I had sawn. I got suckered in on the drying process, the article said that no monitoring was required because of the the equallizing drying taking place between day and nite.

I loaded it up with freshly sawed ash and it was too hot and caused the wood to badly warp. I found out that you want to air dry the lumber first before putting in a solar kiln.

[metalspinner]

D.Frederick,
Yes, I saw that article in FWW.  It is strikingly similar to my set up. I guess when you design around the same size panel,you get simularities.  Sorry to hear about your Ash.  I messed up some lumber by loading green in the kiln as well.  Lesson learned I guess.