Very small kiln dryer for personal use

Georgia088 · February 01, 2016, 10:46:46 AM

hello all and please forgive me in advance for being ignorant to everything about drying wood.
I built a band sawmill over the past 6 months - year. Now that I am cutting enough useable wood for my own personal use I am curious about drying it.
I am very impatient. When I cut wood I am ready to build something with it.
I am hoping yall can give me some pointers on the quickest and simplest way to dry small amounts of wood.
I would like to use wood for many different things from sheds and barns to cabinets and furniture.
I have cut southern yellow pine, cedar, hickory, oak, and currently pecan.
I have built with cedar and pine being pretty much green. Some things have done good. Others needed "tightening" up once it dried and formed gaps.
I am about to build a table out of some of the pecan slabs that I have cut. Pretty much as green as it gets. No idea how it will do but we will see.
I say all that to ask these couple of questions.

is it feasible to build a simple non expensive small kiln to quickly dry small amounts of lumber?

How long can I expect it to take to dry lumber in a kiln? (Hours, weeks, months?)

Does anyone have experience with building with green lumber?

I have searched the forum and seen some info on these questions. So, sorry if I am being redundant. But, any info you can give me would be greatly appreciated!

Thanks!

Ps I am in middle Georgia. (Hot and humid)

WDH · February 01, 2016, 08:38:50 PM

A solar kiln may be the ticket.

kelLOGg · February 02, 2016, 07:59:07 AM

I read of a guy (on FF, I think) who draped a tarp over saw horses, put a fan, home DH unit and his lumber under it and let it decrease the RH until the lumber was dry. I tried it, too, to see if I wanted to get into drying more seriously. I put air dried hickory in my "kiln" and got it to about 7 -8% MC in several weeks. It is now flooring in my office - that was ~7 years ago. I have since built a walk-in kiln but it is well insulated and operates the same way. I can't achieve high temps in it because a home DH unit can't take it so it has its limitations.

The down side is that you have to load the kiln with air dried wood because green will dry too fast and crack. That's a bummer for oak which may take a year to air dry. Pine may air dry in 2 -3 months, cedar can be used for outbuildings right off the mill. There is a lot more to kiln drying - this is just the highlights.
Bob

Georgia088 · February 02, 2016, 11:23:47 AM

Thanks guys for the info.
So, if I were to take hardwood that was only cut a couple of weeks ago and put it directly into a make shift kiln like you are talking about. The wood would probably crack and be no good?
Do the big kilns and commercial kilns have to air dry their lumber before putting them in kilns?
Have you ever built with green hardwoods such as hickory or pecan?
Thanks again!

kelLOGg · February 02, 2016, 12:43:35 PM

Quote from: Georgia088 on February 02, 2016, 11:23:47 AM
Thanks guys for the info.
So, if I were to take hardwood that was only cut a couple of weeks ago and put it directly into a make shift kiln like you are talking about. The wood would probably crack and be no good?

Right

Do the big kilns and commercial kilns have to air dry their lumber before putting them in kilns?
No. They have plumbing to add water or steam at high temps to slowly bring the temp and RH down so the interior of the wood dries close the same rate as the exterior surface. Putting green wood in the kiln I have would dry the exterior too fast relative to the interior and cause cracking.

Have you ever built with green hardwoods such as hickory or pecan?
No. I think it would be a disaster.

Thanks again!

There are many others on the FF with much more drying experience than I have. I hope they will chime in.

Bob

Ianab · February 02, 2016, 03:23:05 PM

Making a table out of big slabs of Pecan or Oak is going to take some patience. If you try and force the drying too fast, it's going to crack for sure. (if you dry it slowly, it may still crack, but nowhere near as badly. Commercial kilns can precisely control the temperature and humidity inside. It gets set to the maximum that particular type of wood can handle without being damaged. In a simply home kiln you don't have those controls, so you need to be more conservative. A plastic tend with a home DH unit works because it's not subjecting the wood to any extremes. Just a warm dry "room". So you can finish off air dried wood in a few weeks.
A solar kiln works, without fancy controls, because it dries in cycles. It only really heats for ~8 hours, then it cools down and the wood can equalise and recondition each night. But if you can loose 1% of the moisture each day, pretty soon you have dry wood.

There is a reason you don't often see large pieces of wood like that for sale, and when you do, they are expensive. Because the are tricky to process. They might either be air dried for a year so, then finished off in a kiln, or they take up kiln space (and power) for a relatively long time to allow the gentle drying cycle. Either way it's not good economy for a commercial operation to tie up a kiln for months, or wait a year before they can sell the product. They are also likely to loose some wood in the drying process.

Now pine and cedar are much quicker and more forgiving to dry. It's hard to dry them too fast, and they air dry quickly. You can use them green to build a shed or a fence. The wood dries (and shrinks) in place, but as long as you use good construction methods, that's not a problem.

But when you want to build cabinets and furniture, you want dry wood to start with. You KNOW it's going to shrink and move as it dries. Build a table top from green wood and chances are it's going to go pretty wonky as it dries out. Wood doesn't move evenly as it dries, so it can cup, warp, twist in the process. Not what you want for your table or cupboard doors.

I'd suggest you cut your table slabs, stack them up out of the way to dry, and get started in a solar kiln and/or air drying shed. Green pine and cedar will work for that. Then build up a bit of a stock of wood that's drying. By the time you have done that, the table will be part dry, you can finish it in the solar kiln and get started on the table.

You will find woodworking much more satisfying if you have built up 6 months supply of wood and are making furniture with dry wood, whiel the stuff you cut yesterday gets stacked up in the drying shed.

Ian

Georgia088 · February 03, 2016, 05:17:15 AM

Thanks for the great info. As I said before, I know nothing about wood drying. I appreciate the simple explanation.
So, it sounds like the best thing for me may be a solar kiln. Can you explain to me a simple way to build a solar kiln? Or direct me to a site or tread with info on how to build one that would work like it should. Thanks again for all of the help!

I guess I should add that the area where my sawmill is located is very shaded and wooded. How much will this effect a solar kiln?

Thanks.

thecfarm · February 03, 2016, 06:03:18 AM

I build my out buidings with green wood. I cut the trees down and saw and build all in the same day. I use board and batten on one building. I used hemlock. Can almost put my little finger between the boards.
There have been many solar built kilns on the FF. Should be able to do a search. I betcha that will keep you busy for a while. :D
You mention shaded area. Don't know much about a kiln,but we had a greenhouse and I would not want the shade. You need the sun to warm the inside. But should not take to much to open an area up to let the sun in.

Denny · February 03, 2016, 07:41:12 AM

"I am very impatient."
Not a good trait for drying lumber. ;)

pineywoods · February 03, 2016, 09:44:23 AM

Georgia, if you can build a chicken coop, you can build a solar kiln. MUST have direct sun.
click here, pics and descriptions. This guy sells kiln dried hardwood to cabinet shops.
https://forestryforum.com/board/index.php/topic,50281.0.html

Ianab · February 03, 2016, 03:36:21 PM

Plans for a solar kiln, and all the technical info about operating it.

https://pubs.ext.vt.edu/420/420-030/420-030_pdf.pdf

GeneWengert-WoodDoc · February 03, 2016, 11:11:05 PM

How small a solar kiln do you want? The picture in my profile is for lumber 4'9, but it a 1/2 scale model of a kiln that holds 9' lumber...easily 320 BF PF 4/4 and as much as 540 BF of 8/4. It is a Virginia Tech design indeed.

Georgia088 · February 04, 2016, 08:07:23 AM

Thanks! Great Info! I'm not sure what size yet, but I have been checking out all of your pictures. I don't need anything very big, because this is just personal/hobby use.

Georgia088 · February 04, 2016, 08:15:24 AM

Gene do you run fans in yours? dehumidifiers? Something that size would probably do for me. My problem is I have no where on my property that gets more than maybe 3 hours of direct sunlight due to all the trees around. Not sure how this would effect the drying...?
THanks!

GeneWengert-WoodDoc · February 04, 2016, 08:52:58 AM

Three hours does seem a bit low.

Ianab · February 04, 2016, 02:26:54 PM

Wood will probably still dry, but I'd expect it to take 2X as long. Not so good if you are impatient. ;)

On a normal sunny day with 12 hours of daylight, you might expect ~6 hours of "good" direct sunshine on the collector. Cut that back to 3 and you get a lot less drying energy collected.

Fans should run when the sun is out, and there is warm air to circulate. Then off during the night cool off. Some guys have used solar powered fans that only run when the sun is shining, and of course stop at night.

Dehumidifier isn't necessary as you open vents to get get rid of the water. That gives you some control of the drying process. Only venting a little keeps up the humidity in the kiln to slow the drying if needed. Fast drying species you can open up the vents more and let the moisture out.

Waterford Woodworks · February 06, 2016, 04:38:54 PM

Not that I'm a professional by any means but you can build with green or air dried material if you are allowing for wood movement. I will try to remember to get some pictures but I went from log to finished product on my dining room table in four months, log to finished product on my daughters loft bed in 2 weeks, log to finished product on my hunting/sugar cabin the day it was sawed. I have built a lot of furniture and all but one have been built with green or air dried material. My furniture is normally built with mortise and tenon and the draw bore method. I often contemplate building a kiln just to make lumber sales more appealing to the customer but haven't had the need or lumber sales to justify it yet.