Finally got to start my solar kiln

[Coffee_Creek]

 

 
br> Been very busy the last year getting construction on our new house started and moving back home but, finally got to start my solar kiln. Wish me luck.......

[PA_Walnut]

Nice work! However, I've got mini-hoe envy!  :D
I had the opportunity to rent one for a project and wonder where it's been all of my life!! Excellent little machine!

[firefighter ontheside]

Looking good.  Hopefully that'll be me soon.

[Coffee_Creek]

 

 lThanks guy's.
the mini-hoe is a fun machine.
Made a little more progress yesterday......

[btulloh]

Looking good.  Love that mini-ex.  That looks like a nice one.

[Coffee_Creek]

I'm really enjoying it, I purchased it about two months ago, loving the cab with AC.....

[Coffee_Creek]

 A little more progress building the end walls....

 

l

[btulloh]

Easy to love cabs with AC.  All of my stuff is open air.  One of these days . . .

Kiln is coming along nicely.  Looks like a good open location.  I'm enjoying your hard work.  Built mine last summer about this same time.  One thing I learned was that fall, winter, spring are better than summer for building solar kilns.  The work went along pretty well until it was closed in, then I had to start working early or late.  We build when we can, I s'pose.  I'm glad to have the kiln, and building in the heat is a distant memory.  Good luck with the rest of your build.  

[Crusarius]

you keeping track of cost? I want to build one but now on a very strict budget. be very interested in knowing actual cost.

[Coffee_Creek]

Sorry but I can't help much on cost, I used a deck that was on my old house that I demolished for the base of the floor and skinned it with 1/2" treated plywood, all other framing I was rough cut lumber that I had sawed from the SYP that I harvested from my property. The paint, fans and dehumidifiers I've had for long enough to not have a clue what I paid for them, sorry I can't be of any help........

[Coffee_Creek]

 
Made a little more progress today, finished framing the end walls and had my little helper (future daughter-N-law) start painting everything that can be painted prior to installing, ain't she cute a bug in a rug?.......
She is one hard working young lady, a friend of mine is a General Contractor building houses, he hired her for a few days, put her on one of his jobs and told all the other workers, all men, just do what she does, 

[btulloh]

It's good to have good help.  Really coming along nicely.

[Coffee_Creek]

 

 

 

 and a little more today, had a short day because of heat.......

[D6c]

Pretty much exactly what I have in mind to build other than I'm considering building one on skids...or maybe a wagon undercarriage.  What's your floor size and height?
Looks like you'll have nice wide access doors.

[GeneWengert-WoodDoc]

The Va Tech kiln holds 1500 bf which with oak will weigh as much as 9000 pounds.  Then add sticker weight and kiln weight.  You might want to move it when it is empty.

[YellowHammer]

I put mind on skids so I can get my forks under it and move it around, which I've done three times without dropping it once.   :D

[Coffee_Creek]

I made some progress the last two days on the North wall over the door opening.
I'm kind of stumped on the best way to build the plenum for the fans, does any one have pic's of how they built theirs?



 

 l

[Coffee_Creek]

Pretty much exactly what I have in mind to build other than I'm considering building one on skids...or maybe a wagon undercarriage.  What's your floor size and height?
Looks like you'll have nice wide access doors.

Floor is app an 8'X18'
South wall is 3'
North wall 10' (I think)

[btulloh]

I just dropped some verticals down from the rafters and used 3 or 4 sections of 1/2" CDX.  Cleats on the wall on the ends.  Nothing fancy.

Starting to build the solar kiln in Drying and Processing

(That should be the link to some pictures.  It's reply#127 (pg 7) in the thread if this doesn't go directly to it.)

It's not in the pictures, but I filled in the gaps in the rafters with pieces of rigid cellulose insulation board screwed to the fan board.  Once again, not fancy, but effective.  I would have installed blocking at that point if I had though it out in advance.


Add:  I was stumped on the best way to build the plenum also.  So I just did it this way.  No regrets, other than the loss of style points.  

[Coffee_Creek]

Thank you for the info, in the pic's it looks like you're pushing the air down the slpoed front and out the lower vents, is that correct?

[btulloh]

It took me a while to catch on to what's really going on.  The fans are actually pressurizing the collector area and that pressure is released through the stack.  The top vents supply makeup air for the humid air that is being exhausted through the bottom vents.  At the early stages, the vents are open more than towards the end of the drying cycle.  It seems counterintuitive, but i started to catch on when I ran the first load.

[Coffee_Creek]

Thank you guy's for all your help, I really appreciate it......

[YellowHammer]

The fans in the top of the kiln push air to the front, down the angled plastic roof, over the warm collector, down the front of the lumber stack, through the stack to the back of the kiln, against the doors, then back up the inside of the doors to the top and then through the fans again.  Its a circular flow, and the vertical fan deck is high up to seal the roof and sides, and I use a full width plastic tarp attached to the bottom of the fan deck and drop it onto the top of the wood stack.  When things are operating correctly, you can see the tarp billow slightly like a sail.  Opening the top and bottom vents regulate how much air is removed per circular pass of the air.  I use two $20 Wal Mart square shaped box fans in the band deck.  I have to replace the fans every 3 years of so, but they work fine and are dirt cheap.  I use a couple pieces of corrugated roofing tin spray painted black as collectors and just lay them on top of the wood stack after I load it.
  
So I load the wood, lay the roofing tin on top of the stack, unroll the tarp and drop the bottom of it on the wood stack like a shower curtain.  Shut the door, crack the vents and move on.
      

[PA_Walnut]

Yellow, do you put your 9/4 walnut in there green, or give it a while on sticks first?
What's the timeline?
Thx

[YellowHammer]

The cycle time depends on how much "solar" I get, Maybe a few months if green, maybe 6 weeks if I put it in after a some air drying.  It all depends.  Normally, to speed things up, I'll put the thick walnut into the solar kiln after it has had some air drying time, just so it doesn't monopolize things.

Thing about a solar kiln, it works on its own time schedule like an easy bake oven, but its significantly faster, and a pretty much set it and forget kind of thing.

Through the years, I've optimized its placement for drying thicker slabs by putting in a place that gets shade from a big tree until about mid morning, but gets full sun when during the winter when the shade trees leads are dropped.  I've had to move it a couple times, I built skids under it so I could use a forklift, and I've got its placement dialed in now.  I'm seriously thinking of building a couple more, they are very useful, elegantly simple, and even though I have two other DH kilns, I use this for most of my high dollar, slower drying wood.

Remember, I don't use it for any wood that is prone to sticker stain, as its the wrong tool for the job.


   

[btulloh]

I'm seriously thinking of building a couple more,

I wish I'd built the second one first.  After building the first one, I know what I'd do differently.

[PA_Walnut]

Remember, I don't use it for any wood that is prone to sticker stain, as its the wrong tool for the job.

All of my "good" stuff gets air-o-flo stickers...even walnut. I've made a SIGNIFICANT investment in them in order to avoid staining/shadowing. They work great!

[thecfarm]

btulloh, :D   One of my sayings,I have to do things twice,so I know how to do it the second time.

[Coffee_Creek]

I built an airplane a few years ago, sure am glad it worked the first time  :D

[Coffee_Creek]

 

 Made a little more progress the last coe of days installing insulation bats and skinning the walls with plywood, painted the plywood and 2x4's to frame the plenum, I hope to build the plenum and install the fans and wiring tomorrow, ordered timers they should be here tomorrow, I plan to run four fans during the day and two dehumidifiers at night....



 

 

 

 

[btulloh]

Looking good.  Almost ready for taxi tests.

[YellowHammer]

Running dehumidiers in a solar kiln can sometimes become problematic.  It negates the ability of a solar kiln to fully equalize wood at night, and also means the kiln is basically running at 100% duty cycle, which with some wood species may exceed the maximum safe drying rate.  

I sometimes run dehumidifiers, especially in the winter, but for summertime, and with thicker more drying defect prone wood, I actually prefer to dial my solar kiln back to more conservative levels.

 

[farmfromkansas]

Would it make more sense to just run the dehumidifier during the day?

[Coffee_Creek]

That's why I'm posting my intentions so that you guy's that know what you're doing can help me keep from doing this totally wrong and I appreciate your imput. I'm as new at this as I can be never have dried lumber before.
I have a barn full of hardwood such as beech, red oak, white oak, quarter sawn sycamore, syp and poplar that has been air drying for two years. I plan to make T&G flooring from the hardwood and base board molding, crown molding and such out of the poplar.  I also plan to make a lot of outside door and window molding out of the air dried lumber.
I need to get about three thousand board feet of hardwood down to around 7 % MC as soon as I can, we're in the process of building a new house and I'll be making all the T&G flooring.
I had read where a guy used dehumidifiers at night to help the drying process.
Any words if wisdom from you guy's would be very much appreciated.......

[WDH]

If your wood has been air drying for 2 years, you can't hurt it with running the dehumidifiers.  Green wood would be a different story.  Fully air dried wood will do fine. 

[GeneWengert-WoodDoc]

As YellowHammer points out, there are two different circumstances when using dehumidifiers (DH) in combination with solar kilns- -green lumber and air dried lumber.

With green lumber, the high humidity that a solar kiln achieves every night serves to relieve any drying stresses (also called casehardening).  Removing this high humidity with a DH will likely result in dry lumber with drying stresses and may also dry the lumber too fast if the solar kiln is working well in warm, sunny weather.

With air dried, the stresses were relieved every evening with high RH that naturally occurs.  So, DH drying at the lower MCs can help speed drying safely in a solar kiln, although the cost to remove moisture from lumber will be quite high.  However, see the next paragraph...

Appreciate that a solar kiln is not a good thermal device in which to add heat in the non-solar hours.  That is because the collector is thermally not too good.  To fix this, you could cover the collector with a blanket at night.  A DH equipment requires a minimum temperature to work well—70 F or warmer.  In fact, with air dried lumber, it is likely more efficient and more economically beneficial to build a well insulated kiln without solar input and use 100% DH, especially in cooler or cold winter months.  Further, a DH at 120 F or even 130 F 24/7 will dry much faster than a solar kiln.

Another alternative would be to build an insulated kiln and then build a separate solar collector that can be "removed" or isolated from the kiln when the sun is not shinning.  Run DH most of the time and use solar supplemental heat.  Overall, quite expensive.

[Coffee_Creek]

Looks like I lucked out, I have two nice new dehumidifiers for my gun room  8)

[Ianab]

Because the wood is well air dried it's pretty hard to mess up. 

You could use your DH to complete the drying, simply by shutting it in a room with the DH and a couple of fans. If you can keep the humidity in the room down to ~40% RH, the wood will dry to around 8%, probably in a matter of weeks. As long as the temperature is over the minimum for the DH to operate, it's going to dry. Being a bit warmer will speed things up. But because the wood is already "dry", you don't need the more precise control or the "reconditioning cycle" that regular or solar kilns provide. 

The wood is probably around 12% now in the barn, which I could use "As is" in my climate. But I understand you want yours a bit drier to account for the dry indoor winter conditions. 

But it really just needs to be acclimated now.

[GeneWengert-WoodDoc]

Heating the wood through and through to 133 F will sterilize it for,insects.

[Coffee_Creek]

Still at it slowly but surly, built plenum and install fans.......

 

 

 

 

 

     

[GeneWengert-WoodDoc]

I am impressed with the quality you have.  Nice job

[Crusarius]

That is looking great. I am definitely saving this thread when it comes time for mine. 

[YellowHammer]

Nice

[btulloh]

Gettin' close to the finish line.  Nice.  Those fans look good.  Gable fans?

[Crusarius]

I keep thinking when it is time to do my kiln I want to use ford taurus fans. They are 2 speed, 12 volt, and can resist road salt in a car. I would think they would hold up pretty well in the kiln. 

Plus by going 12 volt powering them has a few more options.

[Coffee_Creek]

The fans are cheap Lasko floor fans, I removed the tubular leg and the front grill and used wood screws with flat washers to mount to the plywood.........

[Lawg Dawg]

This is looking great!  Like alot of folks on here, I've been following but not posting, I've been needing one of these for 8 years now.  I saw alot of pine boards, and would like to have one to get the boards under 20 percent quickly, so they don't mold so fast.

[Coffee_Creek]

 

 

 

 

 Thanks Lawg Dawg, I put this build off for 2 years, sure wish I had built it then, oh well......

Had a rain delay but still managed to finish one door and get it hung.....

Thank God for hydrulics and pneumatics......

this is one heavy door, just standard framing, 2x4's on 16" centers, add two extra on each end for hinges and door latches, I nailed a few 2x4's inside the kiln to catch the door as I slid it in place, worked like a charm.....
The two short 2x4's that you see nailed to the outside were to hold it while I moved the skid steer and installed the hinges.

[Coffee_Creek]

Not many pic's but I finished the second door, installed hinges, catches and latches.....


 

 

[samandothers]

Those must be hefty hinges! Where did you find them?

[Coffee_Creek]

They're the biggest Ace Hardware had, we'll see how long they last.....

[YellowHammer]

Unfortunately, one of the biggest risks to the hinges isn't sagging from the weight of the door, its when the kiln is open and the wind catches and slams the doors open.  It only takes a little breeze to grab the big doors and swing them against the frame and bend them badly backward.  So some hooks or props or something to restrain doors when they are open will save some real problems later.  

[btulloh]

I used hinges like that and they're holding up fine so far.  Not the best hinges I ever saw, but they're doing the job.

To keep the weight of the door from being borne by the hinges all the time, I put a couple little hardwood rests on the door sill near the center.  I shaped them with a bit of a hump and fit them to take most of the weight when the doors are closed.  Seems to be working and the doors haven't sagged on the hinges.

Doors blowing around is a big potential problem.  Fought with that for a while and then did this quick and dirty solution to take care of it until I get around to fabricating an elegant version.  Some wise man once said "nothing lasts longer than a temporary fix".  There might be something to that.  

(You can see my temporary electric service is still waiting to be finished.)



 


 

[Coffee_Creek]

Good advice and ideas, thanks guy's.......

[YellowHammer]

Looks pretty elegant to me, I just use little hooks.

I ran my electrical service to mine with an extension cord many years ago and it has long since been overgrown within grass so I guess its permanent, too.  

[btulloh]

Done beats perfect.  

I do have a good excuse reason for that extension cord - I plan to move the kiln to another location.  That was going to happen last winter.

[Coffee_Creek]

due to the heat, it feels like each day is a lot of baby steps, completed wiring and all the vents, no pic's f the wiring, with a little luck we'll finish the sloped front tomorrow.......



 

 

[btulloh]

It's a hot thing to work on.  I had the same problem.  Early mornings then knock off for the day.  I even put up a temporary shade tarp.  It helped some. Once you paint the thing black inside, it's a hot place to work.



 

[btulloh]

I was surprised at how long it takes to get all the little stuff done.  

Your kiln is looking good. 

[Coffee_Creek]

thank you sir, 
I hope to have a load of lumber in this weekend

[Coffee_Creek]

finished the electrical....



 

 

 

[Coffee_Creek]

installed the tarp (baffle) and put some 4"X6" on  the floor, 
First test load of lumber is in the kiln.. 8)
now if I can figure out how to read this Delmhorst MC meter...



 

 

 

 

[Lawg Dawg]

Looking good CC, if you post a picture of that meter, I'm sure someone on here can tell you how to read it.  What kind of temps you getting in there? 

[Coffee_Creek]

with all vents wide open and all fans on high It's hitting around 125, Maybe if I shut the vents half way and slowed the fans down it would get hotter?

[Coffee_Creek]

the average MC of the lumber was 12.4, I'm looking forward to checking again in a few days to see how well it's working, I'll post the results.

[YellowHammer]

Keep the fans running when heating, got to keep the air moving, but shutting the vents will increase temperature and also increase humidity.  The unscientific way to dial in a solar kiln is to open the door in the middle of the day.  If you get hit in the face with hot, high humidity amazon rain forest air, then you need to open the vents some because you are trapping too much humidity.  In contrast, if you open the door and it feels like a hot dry breeze, then you are venting too much air and can close the vents to get hotter and absorb more moisture.  

The scientific way is to get an EMC chart from the Web and use the relative humidity and temperature, to determine the true EMC of the air.  It's a good process to understand and will help you get the hang of the thing.  

You can't do a whole lot wrong, you may just not be drying at the full capacity of the current solar conditions.  

[Coffee_Creek]

Thank you so much yellowHammer, So many good thoughtful people on here like you make this a great site......
I learn something every time I log on......

[GeneWengert-WoodDoc]

If you run the fans 24/7, you will not get below 12% MC.  So, run the fans only when the kiln is heated 20 F or more above the outside morning low temperature to achieve the lower MCs.

At the end of drying, like where you are now, heat is important to get the last bit of moisture out.  So, close the vents almost all the way.  A small opening will vent enough air to keep the humidity down.

[YellowHammer]

You will get a "feel" for it after a few loads.  When the humidity inside drops as the wood starts to dry, you'll know it and as Gene says, start closing the vents down.  At the end of a run, I'll have mine almost closed, maybe just a crack open.  You'll be done when you open the doors and the air is very hot, dry, and you back up so it won't burn your face and you see dead bugs on the surface of the wood looking like black pepper.   :D
If your sunglasses instantly fog up from the heat moisture coming out, shut the doors because it ain't dry yet.  :D

With my solar kiln, I can tell when the wood is dry when I see little white stripes in the black painted exterior siding as I walk by.  It means the wood inside is dry, and the exterior siding is now drying and shrinking, causing the black paint to show gaps.  It's a pretty cool phenomenon.  When I put a load of wet wood in, the humidity given off goes through the walls and causes the siding to swell in a few days, almost hiding the white stripes.  
Solar kilns are the Easy Bake ovens of the kiln world, and one of the best ways to dry wood reliably.    

[Coffee_Creek]

I'm excited about having it going, I have a pole barn full of rough cut lumber that I harvested and a guy close by saw the lumber about two years ago, I purchased a Woodmaster 725 molder and plan to make all the T&G hardwood flooring and all the inside and outside molding including the crown and baseboard molding, I built a new addition to my shop and installed a dust collection system, added a used planer and table saw to my collection, 
I hope that after we're completed with our new house I can make and sell high quality wood molding to make extra money, 
I post pic's of my wood working setup soon.....

[btulloh]

Congrats on getting the first load in the kiln and drying.  Nice job.

[Coffee_Creek]

thank you sir....

[btulloh]

What is that plane in your profile picture?  Hard to see what's going on there at that small size.

[Coffee_Creek]

It's a RV-9A that I built a few years ago, a little two seat sport plane..

[Coffee_Creek]

 

 

[Coffee_Creek]

checked the first load today, MC was at 7.3, removed the lumber and put in the shop ready to mill into T&G flooring,
second load loaded in the kiln, I'm very pleased with how well this kiln is performing.....

[GeneWengert-WoodDoc]

What sort of air flow do you get in your kiln with that gas-powered :D two blade fan?

[Coffee_Creek]

 I don't an instrument to check air flow but, I have a heavy baffle and it has a big bellow in it and you can feel the air coming out of the bottom vents.....
I don't have two bladed fans, they're all three bladed....

[btulloh]

What sort of air flow do you get in your kiln with that gas-powered  two blade fan?

I think he's talking about the red and white one with the wings.

That's an good looking plane you have.  I'm not sure if it's the angle of the photo or what, but it looks like a lot of wing area on that.  What kind of performance do you get out of it?  Looks fun.  You've got a lot of bad habits to keep up with.  :D

Congrats on getting your first load done.  Sounds like your kiln is doing its job.

[Coffee_Creek]

haha, I didn't read the "gas powered" part, the red and white gas powered has a 145 knot air flow with a fuel burn rate of 5.5 gallons an hour when set on 75% power economy cruise.

[btulloh]

That sounds pretty sporty.  Is it configured for inverted flight?

[Coffee_Creek]

not really, no flop tube in the fuel tanks, it can perform most aerobatic maneuvers just no sub stained inverted flight.
There's other RV models that are much more capable performing aerobatics than my RV-9A, 

[WDH]

Put some flat sawn sweetgum in your kiln if you want to see some aerobatics.  :D :D :D. 

[PA_Walnut]

Put some flat sawn sweetgum in your kiln if you want to see some aerobatics.  . 

..or some flat sawn sycamore!

[Weekend_Sawyer]

I have enjoyed this post.

I have a couple of questions. I may have missed this information in the thread.

How are you monitoring the temp and humidity in the kiln?
What did you use for the clear "window" in the kiln?
What is the angle of the window?

Thanks
Jon

[Coffee_Creek]

I'm not monitoring the temp or humidity. I've checked them a few times with a gadget I use for long range shooting, the mid day temp was around 130-140, I can make it a little hotter by adjusting the vents and fans,
I just fill it up with lumber, set the fans and vents and leave it along for a week, come back a week later and the lumber is around 7.5-8 MC
I'm starting to mill the wood into T&G flooring and molding, here's a couple of pic's, any suggestions would be welcomed, and a pic of a yellow jackets nest that was between two boards with stickers, I've never seen a nest like this, it looks like a beautiful piece of art,
I'll start a new thread on milling the T&G/molding,
rough lumber going in.......


 
smooth lumber coming out.....

 
I built a cantilevered metal rack to help separate the lumber, I bring a load from the kiln and put on the lower level, as I plane it I put on a separate level...

 

yellow jacket nest........


 

 

[Coffee_Creek]

I forgot to mention the reason it only takes a week drying time is I harvested my trees two years ago and had them sawed into 4/4, so it's been air drying for two years.

[GeneWengert-WoodDoc]

Do you have any snipe at the ends?  Considering the outfeed side, gravity will be trying to pull the front part of the lumber down, which can push the end of the lumber into the cutter when the chip breaker can no longer hold the lumber against the bed plate; this gives you snipe at the end.  Same effect in the front when feeding.  What is suggested to eliminate all snipe is infeed and outfeed tables that slope upward a few 100s of an inches per foot as you go away from the machine and is long enough to support the lumber the entire time it is in the machine.

The solar kiln, VA Tech design, is suppose to work well without any effort or measurements, except MC, for 4/4 and 5/4 of most species, especially when air-dried first.

Congrats on this load.

[btulloh]

Nice rack Coffee Creek.  I could use about 20 of those.  

Congrats on getting the first load from the kiln.  It'll be interesting to watch your progress on the t&g.

That yellow jacket nest is a piece of art.  Never got to see one that wasn't spewing yellow jackets while I was running as fast as I could.  That's a whole nother perspective.  Glad you didn't find it the hard way.

[Coffee_Creek]

very little snipe, The Woodmaster has fairly large infeed and outfeed tables with a slight tilt to them to help with snipe,  I set up infeed and outfeed roller tables originally but the bending forward to place and remove the boards was tough on my back so, I went with just a single roller stand on each side spaced about eight feet from planner, this allows me to be right next to the boards and not require bending over just reaching down, much easier on my back this way........

[caveman]

The solar kiln, VA Tech design, is suppose to work well without any effort or measurements, except MC, for 4/4 and 5/4 of most species, especially when air-dried first.

Doc and any others who use their solar kilns to dry thick slabs -  Would you expect to get flatter slabs by air drying them down to below 20% MC and then putting in the solar kiln or just going from the mill to the kiln?  We have been air drying first which has worked okay but sometimes one really has to be patient waiting for thick live oak and others to get down below 20%.

I would worry much less about bugs (PPB specifically) if we were to go straight into the solar kiln.  We can sterilize in our hot box but it does not accommodate much more than 8.5'.