Solar kiln for hardwoods part deux

[ValleyCottageSplitter]

Very cool idea. Not too hard to setup either. I wonder how many seasons the material will hold up? Does it need tons of light or could it work in the woods?

 

[Woodsplitter67]

Very cool idea. Not too hard to setup either. I wonder how many seasons the material will hold up? Does it need tons of light or could it work in the woods?

Its run by the sun, so the hotter the better. The plastic does not hold up. You will get 1 summers worth out of the pladtic. Theres better plastic on the market if you want it. Im not going to do a kiln next smmer, also i have changed my kiln size form time to time.if your wooded area has alot of sun it will work. Your about 30 days from the fall equinox, so your sun exposure is getting shorter. These kilns do not work in the winter. The racks that i have are reusable, and have made them shorter or longer depending on my needs
I would set one up in a small area and see how warm it gets.. you a little north. Put a super small one together and check the temp on a sunny day.. that will tell you everything. If it looks good than plan one for early summer..im doing 2 cords right now..

 

[RGrant]

Its run by the sun, so the hotter the better. The plastic does not hold up. You will get 1 summers worth out of the pladtic. Theres better plastic on the market if you want it. Im not going to do a kiln next smmer, also i have changed my kiln size form time to time.if your wooded area has alot of sun it will work. Your about 30 days from the fall equinox, so your sun exposure is getting shorter. These kilns do not work in the winter. The racks that i have are reusable, and have made them shorter or longer depending on my needs
I would set one up in a small area and see how warm it gets.. you a little north. Put a super small one together and check the temp on a sunny day.. that will tell you everything. If it looks good than plan one for early summer..im doing 2 cords right now..

Just kind of reading along as I stumbled upon this today- out of curiosity, why are you not planning on doing a kiln next year? Seems like you're getting the results you're looking for.

 

[Woodsplitter67]

Just kind of reading along as I stumbled upon this today- out of curiosity, why are you not planning on doing a kiln next year? Seems like you're getting the results you're looking for.

I dont need the wood.. im sitting on 14 cords of wood CSS. This is wood that i have had sitting in rounds that was getting some rot on the outside.. i do this more for fun than necessity. One of the reasons i did this in the beginning was to see if i could do it.. if ever i got in a bind I could dry wood for my stove over the course of one summer and have plenty of wood ready for the Burning Season. Or i could purchas the so called seasoned wood as actually season it over the summer. I also have 4 cords of log lenth ready to be cut to rounds and split.. i may wined up with some wood on the racks I may just top cover it or do a kiln and season it for next year. Will see

 

[Woodsplitter67]

I opened up the kiln today.. today markes exactly 60 days
My oak wen fron the lower 30% to 19 % in the 60 days
Interesting though some of the stuff that was a little punkey droped to near 2% in the same time period. Im going to keep the kiln going for another 12 days and then tarp it up untill winter. Ill post back of what the final mc will be.. im shoothing for 17-18%
As a side note... the wood dropped an average of .23 % per day over the 60 days.. i think that this is a lot and quite substantial . As a side note the last picture was a 8in round that was split open that is Beach down to 2% within the 60 days

 

[barnaclebob]

Its run by the sun, so the hotter the better. The plastic does not hold up. You will get 1 summers worth out of the pladtic. Theres better plastic on the market if you want it. Im not going to do a kiln next smmer,

My greenhouse plastic has lasted a several years on our gardens so far. But its only outside for a couple months in the spring.

 

[Woodsplitter67]

My greenhouse plastic has lasted a several years on our gardens so far. But its only outside for a couple months in the spring.

The greenhouse plastic is so much better.. its aldo expensive. I have done 4 different kilns and all were different sizes.. untill i come up with a standard size.. it will be big box store plastic

 

[Coalescent]

Finished my second solar kiln yesterday!

I know these kilns don’t do much during the winter, but I’m going to try it out anyway. I did some Googling and read some posts by folks using more traditional solar kilns for drying lumber who say they can operate below freezing on sunny days, as the sun will heat up the kiln 30-40 degrees above ambient temperature. When it gets cold, I’ll seal the bottom up and only open the top vents at the end of the day for a bit to let out any moisture.

At any rate, reading those posts convinced me to try it out since I’m so behind. Might be able to use some of the wood in the second kiln by Spring. It will be fun to watch the temps and experiment.

 

[Woodsplitter67]

Finished my second solar kiln yesterday!

I know these kilns don’t do much during the winter, but I’m going to try it out anyway. I did some Googling and read some posts by folks using more traditional solar kilns for drying lumber who say they can operate below freezing on sunny days, as the sun will heat up the kiln 30-40 degrees above ambient temperature. When it gets cold, I’ll seal the bottom up and only open the top vents at the end of the day for a bit to let out any moisture.

At any rate, reading those posts convinced me to try it out since I’m so behind. Might be able to use some of the wood in the second kiln by Spring. It will be fun to watch the temps and experiment.

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Thanks for posting this. I see your in NH if you can tell us a couple of things this would be great. 1 what is the MC of the wood right now as you start the kiln. 2 what kind of wood is in the kiln, hardwoods like oak, hickory ect.. 3 please post some temps here and there over the winter.. out side and inside.
I like the build.. how many cords..as a side note your temps inside the kiln may not be as high as you have posted.. the sun angle is going to be getting pretty low, and with such a low angle you not going to get a ton of heating.. it would be nice to see what would happen over the winter though..

 

[johneh]

In the winter just watch the moisture in the kiln
it will condense very quickly on the cold plastic
On a very sunny day with the outside air at -15
the inside of the kiln at 2 pm is close to 30
I have to vent mine by 3:30 to get the moisture out
It works well Oak and Hard sugar maple go in at
over 35% moisture and in the spring will be at 20
to 24 % and will be at 12 to 15 % the first of August
Been doing this for the last 15 years no realy a kiln
just a frame with greenhouse plastic on it dome-type
top so snow will slide off it sitting in a sunny location

 

[Coalescent]

Thanks again for sharing the design and all the info, @Woodsplitter67! I'll answer your questions in a new thread that I'll open soon.

 

[Woodsplitter67]

So here is the end resilt. Sorry havent had time to post and keep up.. I pulled wood out on September 2nd which would have been exactly 60 days my Oak was down to 19% moisture I let the Kiln run until September 29th at that time I pulled the kiln apart I split open a large piece of Oak and it was down to 11% so my wood went from roughly the mid-30s to 11% in less than 90 days

 

[Poindexter]

FWIW I have been using the cheap plastic from the home stores, 6mil clear, about 15 bucks for a 10x20 foot piece to cover one of my units. I get about 18 months out of each piece. I am looking pretty hard at clear corrugated roofing as a buy once/cry once solution. Likely I will do just one or two kiln units and see how it hols up before I spend all that money.

Besides kilning the wood dry in a hurry, these also keep blowing rain and blowing snow off the end grain of my stacks.

 

[Bad LP]

Out of curiosity I gotta ask.

My wood shed is currently in a good spot for sunlight and wind and the wood seasons just fine. I see you guys building kilns using semi clear plastic. I have access to .045 and .06 roofing rubber and could easily wrap the shed up pretty tight.

Would a black rubber wrap work if I was in a bind?

 

[Woodsplitter67]

Out of curiosity I gotta ask.

My wood shed is currently in a good spot for sunlight and wind and the wood seasons just fine. I see you guys building kilns using semi clear plastic. I have access to .045 and .06 roofing rubber and could easily wrap the shed up pretty tight.

Would a black rubber wrap work if I was in a bind?

I dont think so. Basically your making a greenhouse the sun needs to go through and heat the inside, plastic traping in the warm air and creating a cycle of heat building. If you wrap the shed in ribber your kinda just heating the rubber with some heat transfer to the inside. Dont get me wrong.. you will transfer some heat... but i doubt that you will see temperatures inside your shed like a kiln.. try it and post your results.. we can all learn by what works and what doesn't..

 

[Woodsplitter67]

FWIW I have been using the cheap plastic from the home stores, 6mil clear, about 15 bucks for a 10x20 foot piece to cover one of my units. I get about 18 months out of each piece. I am looking pretty hard at clear corrugated roofing as a buy once/cry once solution. Likely I will do just one or two kiln units and see how it hols up before I spend all that money.

Besides kilning the wood dry in a hurry, these also keep blowing rain and blowing snow off the end grain of my stacks.

I built my son a greenhouse this past summer.. using 8mm polly carb.. if i were to do a permanent kiln.. thats what i would go for.. with auto vent openers fo 30 bucks each

 

[Cfran88]

Is it possible to start a kiln too early? I'm CCS now, along with stuff from last fall. Should I wait until all the spring storms or over or cover the wood asap?

 

[Woodsplitter67]

Is it possible to start a kiln too early? I'm CCS now, along with stuff from last fall. Should I wait until all the spring storms or over or cover the wood asap?

No matter what you do your wood will not be ready untill the fall of 20 or beyond. Its best to just process as much wood as you can, and sometime the end of june start the kiln. Id top cover for sure right now

 

[spudman99]

Of course it is possible for an early kiln, but the results will not be fantastic. Kilns raise interior temperatures. Going from 40 deg to 65deg will not remove that much moisture. Also you then have the difficulty of removing humidity from the interior when lower air temps cannot hold that much water. Also you give the kiln that much more UV and exposure possibly breaking down the plastic materials sooner.

I would just wait till May or June, assemble your materials and design now, get the rounds split and nearby the kiln location and then hit it when it gets and stays warm.

 

[Stir224]

What is the advantage of keeping the kiln temperature below a certain threshold? If you have it to hot does it just dry the wood too fast and cause it to shift a lot?

 

[Woodsplitter67]

What is the advantage of keeping the kiln temperature below a certain threshold? If you have it to hot does it just dry the wood too fast and cause it to shift a lot?

I dont see any where is says to keep the kiln under a certain temperature.. can u expand on this

 

[Stir224]

The vents are cut in a u shape and are about the size of a grapefruit on both gable ends. Once cut they are like a flap. The larger the cooler the kiln, the smaller the hotter. What you need to do id make a cut, put the probe in and let it sit for a bit. If it gets to warm open it up more
Example.. if the outside tem is 75 and the temp inside is 120 you should open it up more. If its 75 out and the kiln is at 90 you need to close the vent some to build more heat. You need to base your temp on your average summer temp. I set the kiln for aprox 5 degrees lower than the average temperature.. here at my house the summer temps are 85 to 92.. so if i set the kiln up at 80 on the normal temp days it runs hot. Its dosent take long for wood to dry at 135 degrees ...
Once you have the kiln vent set... dont change it. Leave it alone.
You adjust it by its size.. if you cut it to big.. Gorilla Tape works great to seal the cut and make it smaller..you can tape it open to keep it at the desired opening

I thought I saw it somewhere else but I may just be losing my mind. In any case is there a reason you would want to lower the temperature when it hits 120? I think PD also made a point a few posts back about warping or cupping...

I guess what I'm asking in a round a bout way is what temp do you shoot for? My wood will be stacked for 4 months or so ahead of time so I'm guessing it will have shifted into place by then

 

[Woodsplitter67]

I thought I saw it somewhere else but I may just be losing my mind. In any case is there a reason you would want to lower the temperature when it hits 120? I think PD also made a point a few posts back about warping or cupping...

I guess what I'm asking in a round a bout way is what temp do you shoot for? My wood will be stacked for 4 months or so ahead of time so I'm guessing it will have shifted into place by then

so if you read that specific post it is setting up the vent on the kiln.. It did not say that your not supposed to keep the kiln lower than 120 degrees with an outside temperature of 75.. What this post is saying is that you can lower or raise the temperature by opening and closing the flap.. and at a normal summer time hi temperature if set correctly you can achieve in inside kiln temperature of 130+ degrees..actually the warmer the better as long as your not building moisture with in the kiln.. as the air gets warmer in the kiln its actually makes the air dryer increasing its ability to hold more moisture..and speeding up the drying process..

 

[Stir224]

so if you read that specific post it is setting up the vent on the kiln.. It did not say that your not supposed to keep the kiln lower than 120 degrees with an outside temperature of 75.. What this post is saying is that you can lower or raise the temperature by opening and closing the flap.. and at a normal summer time hi temperature if set correctly you can achieve in inside kiln temperature of 130+ degrees..actually the warmer the better as long as your not building moisture with in the kiln.. as the air gets warmer in the kiln its actually makes the air dryer increasing its ability to hold more moisture..and speeding up the drying process..

Thanks so much for the info! 4.5 ish cords of oak and hickory I'm going to give it a try for this summer.

 

[mcdougy]

Does the wood take on any moisture if you get it down to single digit moisture content? As in the beech that you took to 2% , did it come back up? I'm assuming too low of mc causes wood to burn faster and affects overnight burns?