I am almost afraid to post this idea... The culvert kiln!

[crtreedude]

I don't know if I have completely lost my mind (tis a definite possibility I will have you know) or I might just have a decent idea.

I am trying to come up with a way to do inexpensive kilns - the expensive ones come later. It occurred to me that I just need to have a heat source, and enclose to maintain the heat and seal up for water. The top needs to have adjustment for vents to relieve excess heat.

So, after thinking for a while, it occurred to me that I can use concrete tubes, i.e. culverts to hold up the wood AND to gently heat it. Our culverts are very thick and have lots of wire in them. Six inch in diameter are readily available.

So, I am thinking of having them every 32 inches or so, which means the test kiln will be about 4 varas long (about 11 feet). Each one will have its own fire pit and chimney, with control on the fire from restriction of air.

We assembly it, and then inclose it. If we do it right, I am thinking we will have enough draft to pull the smoke after we have a good fire going.

Okay, have at it, why won't it work or am I a genius? 

[crtreedude]

One nice thing about independent fire pits is that the middle could be a bit warmer than the ends, helping to dry more evenly.

Okay folks, have at it!

[beenthere]

No idea what just how you are trying to do the drying.....
I'm too slow, I guess.
 

[Texas Ranger]

Most kilns require a steady, low temp, dual cycle to operate.  Not to mention air flow.  I think you would create a new market for honey comb lumber.

[Gary_C]

I don't know if I have completely lost my mind (tis a definite possibility I will have you know) or I might just have a decent idea.

Okay, have at it, why won't it work or am I a genius? 

It's the first part that is right. 

What a kiln needs to provide is;

1. A uniform air flow so that all the ends, sides, and middle of the boards sees the same conditions.
2. Closely controlled and uniform temperature and humidity in the air.
3. Allow carefully scheduled changes in the temperature and humidity as the wood dries uniformly.

If your culverts can do those three things, it will work. If not, you can probably get wood dry, but not uniformly nor straight.

[crtreedude]

Thanks all. It might work, but then again, it might not. What I was thinking of is supplemental heat to something like a solar kiln. As far as air flow, the devil is in the details of making the stack so that the air can flow through, and since hot air rises, it should move - requires ventilation.

Many of our tropical woods are very easy to dry - since there isn't much here like seasons, the wood doesn't normally shift much, but there are exceptions of course.

The key is not to dry too fast, and seal the ends, after that, most things seem to work okay. Nothing like what you have to deal with in oak, etc.

[olyman]

cr--i read of a man--that took a 6 foot dia steel culvert--like what would go under a driveway--he enclosed the ends--then built the firepit---and that was his dryer--said it worked very well--and the price was right--as it was a good used one--he got it for free!!!!!  also--you could use the body of a used school bus--as thats what im going to use---

[Ironwood]

I thought you were going to say that you were using the big black smooth interior walled plastic pipe. I have a 48" x 20'er that appeared at my buddies place after hurricane Ivan flooded these parts of Western PA.  You would not be  able to just throw some fire under it, however you would have solar gain to some degree.

 Ironwood

[Texas Ranger]

Solar powered kiln would seem to be the more practical method, considering where Fred is, at the moment.

[crtreedude]

Solar powered kiln would seem to be the more practical method, considering where Fred is, at the moment.

Solar kilns are wonderful here for 4 months of the year, and then the rains come... Maintain the same basic design, but supplement heat.

Since it is nearly free to try, I am going to give it a go - and load it up with some junk wood. What is life without experiments, eh?

[SwampDonkey]

Depending on how hot those concrete culverts get you might see them crack or bust open with the heat. And others in here know more about kilns than I do, as I know next to nothing on them. I don't envision a happy ending. 

[Radar67]

CR, are you talking about using the culverts as a stove of sorts? To contain the fire and use ducting to transfer the heat to a solar type kiln?

[crtreedude]

yes, we are using the culverts as chimneys, with a slight pitch. The idea is that the concrete will buffer the heat. And, we know that it will survive, people use them as chimneys all the time here, we might have to line them, but that isn't a problem.

Concrete will give us mass to buffer the changes of temperature, we are talking a slow fire, with control.

At the very least, I will have a ready made place for grilling...

[crtreedude]

Depending on how hot those concrete culverts get you might see them crack or bust open with the heat. And others in here know more about kilns than I do, as I know next to nothing on them. I don't envision a happy ending. 

Sigh, they always laugh at genius.... 

[crtreedude]

I don't know if I have completely lost my mind (tis a definite possibility I will have you know) or I might just have a decent idea.

Okay, have at it, why won't it work or am I a genius? 

It's the first part that is right. 

What a kiln needs to provide is;

1. A uniform air flow so that all the ends, sides, and middle of the boards sees the same conditions.
2. Closely controlled and uniform temperature and humidity in the air.
3. Allow carefully scheduled changes in the temperature and humidity as the wood dries uniformly.

If your culverts can do those three things, it will work. If not, you can probably get wood dry, but not uniformly nor straight.

By the way, I was going to say, I can do all these things and I greatly appreciate you listing them.  The key is going to be not to rush it. For optimal speed, you need to have a lot more control, but do it slower, and things go better. We also air dry for a while before putting anything in a kiln. It helps a lot. Rarely do we have problems in the kiln, because whatever was bad, shows up before.

[beenthere]

I'm anxious to see some pics. Maybe then I will comprehend your game plan.

I can't say it won't work. Hope it does. 

Pics...asap   

[crtreedude]

Pics will be - yesterday we ran a test and amazing enough, the overall idea tested out just fine.

An interesting thing, while researching kilns, etc. I found out this is not a new idea. DanG, I thought I could patent it or something.  Using flues instead of steam heat is done by some systems. I was amazed in truth.

One thing, after lots of ready, has occurred to me: don't try to be too fast. What I am going to do is try to simulate a solar kiln, which means heat it up during the day, and let it cool down at night. This means that the wood has a chance to rest and equalize moisture between the inside of the wood and the outside. This is why (from my reading) the quality from solar kilns tend to be so good, so if I do the same, life should be very good, and I personally don't want to tend the fire at night.

Now, for something totally wacko, I am planning on one of the stoves that drives the flue to be something I can cook a pizza in at the end of the day, or roast meat or potatoes... Every see an Adobe oven?

[Cedarman]

Fred, the restauranteur!

[timberfaller390]

Had a chance to get somepics yet?

[crtreedude]

Okay folks, just to force me to take pictures. The kiln LIVES. And, amazingly, shows every sign of being a success. Nice, gentle heat too. By Jove, I do think it is going to work wonderfully.

We are loading up the first test. So far, it appears the temperature goes up to about 120 F and stays there - we let it stop during the night to equalize the moisture between inside and outside in the wood.

So, pictures hopefully tomorrow.