Time to start building kilns.

[crtreedude]

I need to start building kilns. Now, be nice to an ignorant ole software engineer...

We of course have sun, lots of it and it is intense. We don't have cold. But, for 8 months of the year, we have humidity - usually runs at 70%.

Question, can we use a solar kiln and how do you get down to 7 to 10 percent when the surround humidity is much higher? Should I even bother making a solar kiln?

We have designs for a kiln using a dehumidifier - of course a bit more expensive to build, but it will be faster production I assume and perhaps better control.

What is everyone's feeling on this?

Thanks

[flip]

OneWithWood has a very slick design for end loading.  I think he is using a DH, check out his thread relating to it.  If I had to do mine over this is what I would do.

[beenthere]

cr
Can you get the humidity down low enough to reach 7-10% mc conditions, and hold it there....

i.e. after dry kilning to say 10%, keeping the piece at that condition while manufacturing into furniture, and then shipping under the same condition would seem to be a tricky problem.

Some local experience may be available, as well as Jim King in Peru might chime in here.

Here is a table for wood equilibrated at a particular mc, and the temp/RH combination...looks like 90° F at 60% will give 10% mc

http://www.csgnetwork.com/emctablecalc.html

[pineywoods]

Question, can we use a solar kiln and how do you get down to 7 to 10 percent when the surround humidity is much higher? Should I even bother making a solar kiln?

 

Thanks

A combination solar/DH works real well under conditions very similar to yours. I've built two that are used to dry cypress (100% moisture content) down to under 10%. They work a little different from what you would think. During the day blowing hot air through the lumber stack picks up moisture from the wood. When the air in the enclosure cools down at night, you get a building full of air that is so humid, moisture condenses out. The effeciency of a small dehumidifier is maximum under this condition. Our DH units are small cheap room de-humidifiers from sears. They will pull out 2 gallons of water a day from 500 bd ft of cypress. Next morning, you have a kiln full of dry cool air, which when heated, becomes even drier. The only problem you might have, too much heat !! Conventional solar kiln texts say to vent the hot air out the top, but I contend this is counter-productive. Venting will cool things down but you are replacing the hot air with somewhat cooler outside air that has 75% humidity ...

Do a search on solar kiln's there's a bunch of threads on the subject.

[scsmith42]

Harold, FRED, one option may be to use your solar kilns are pre-dryers, and then cycle the lumber through a DH kiln.  You could use rolling kiln carts, with kilns that had doors on each end, and simply roll the load from the solar kiln to the DH kiln.

One DH kiln could probably keep 4 - 5 solar kilns busy, because you'd only need to leave it in the DH kiln for a few days to bring it the rest of the way down and sterilize the load.

Scott

[Fla._Deadheader]

 HUH 

[scsmith42]

Sorry Harold - I must be dyslexic cause I'm always calling Fred your name!

[crtreedude]

So, what I am hearing is that to get it down to 10% say, you do have to use a dehumidifier. Is that correct?

I was reviewing a corral we have yesterday - looks pretty good for about 10,000 BF of solar - and then I could make a waiting room of the wood that will be used in the following week and have a dehumidfier there.

The plans I found yesterday say that there isn't a problem in getting down to 10% with a solar kiln here - more than that would be a problem. I am not sure how much more I need to go than 10% - If I am making furniture for a drier climate - where should I go to?

Thanks for all the help - and it was nice to wake up Harold too!

[crtreedude]

So, you would say Scott that one Gringo in paradise looks the same as all others? 

[Fla._Deadheader]

 Except that Fred is "muy Feo".

[LeeB]

No estas feo Senor Herald. Un pocito vieho posible, pero tienes un espirito muy bien.

[pineywoods]

cr, my advice on the kiln would be, go ahead and build a solar unit from plans of your choice. Easy to build and cheap. Try a few loads of your local lumber. If it works, fine, if not, stick a room dehumidifier inside, again cheap and easy. Throw your kin operators books away, solar is a whole different ballgame, experiment...Mine work well enough to dry oak for flooring with just about zero reject boards. And I do like the cost...

[JackLeg]

Hey, Pineywoods!  I've just completed a solar kiln, painted the interior yesterday.  Leaving in a few minutes for the seminar at Virginia Tech. 

Scott Smith tells me you have lots of experience with them.  I'll primarily be drying cypress right off the mill.  Any tips you can offer will be greatly appreciated. 

Thanks in advance.

[pineywoods]

Most of our experience has already been posted on here in various threads. We( that's member arlcon and myself ) have  identical kilns. Mine dries mostly pine, cedar and a little oak. His is almost exclusively cypress. Mine is a hobby operation and his is a comercial business. If you gonna load yours up with wet cypress, I'd advise 2 things. 1- Put a small room de-humidifier inside and run a hose from it outside.Without it, mold is probably going to be a problem.  2- Don't pay too much attention to the "experts". Solar is a different ball game from conventional kilns. Experiment with yours for a few months and you'll probably know more than most of them.

[jim king]

We have finally after looking at all forms of drying possible decided on used kilns from the States.  With everything in the wood industry up there selling at distressed prices we will end up with all the mechanical parts from the States and cement buildings.  It was simply a choice of economics as we will have less than a dollar a board foot invested in the kilns.

That for us is equal to paying for drying 3 kiln loads or another way to look at it is the value added on one kiln  load pays for the kiln.

As for our moisture problems we average close to 90 % humidity daily when it is not raining and we dry down to 6-8" MC and if left unpackaged the lumber will be up over 15% again in a month.

[solidwoods]

First thing to do is study how kiln opn. works.
USDA Forest svc. Kiln operators handbook.
A hard read but when you understand how wood drys you probably won't want all only solar.

I use The Pola egg discloser for a kiln controller $300 I think

You have to have monitoring and control of temp/humidity.
I like wood fired hot water for heat (don't like solar/dehumidifiers,, to many people just build a hot box in the sun).

A neighbor with a solar kiln (a hoop green house)
Hey jim our wood is cupped and bent, can you put it in your kiln and straighten it out?
--No I sure can't, a kiln can't do that.

--Is the wood checked?
We didn't mark anything, just stacked in the kiln.

--Is the wood honeycombed?
Thay aint no bees in our kiln,  we'd run em out if there were.

--What was your wet bulb/dry bulb readings?
We aint got no lectricity jim thats why its a solar kiln, so they aint no bulb.

--So your kiln doesnt have a fan?
No shoot no, were trying to heat the wood not cool it.

--How do you regulate the heat and moisture.
It gets hot in the day Jim and cool at night (Duh)  and if its sweat'in we open a door.

jim

[Left Coast Chris]

Jim,

Arnt you in a pretty severe seismic zone there in Peru? 

Hope you put plenty of reinforcing in the concrete and think safety in the design.  Im sure you have that covered coming from the States....... but just wanted to mention since we seem to have more global disasters lately.

[BBTom]

CR, 

This is what I have learned about solar kilns. 

The way a solar kiln works is by heating the air.  Hot air will hold many times the moisture that cool air will.  The sun heats the air during the day, allowing it to pick up lots of moisture from the lumber.  Fans keep the air moving thru the stack so all lumber is dried evenly, not just the edges of the stack.  When it gets too hot, vents are opened to let the hot VERY humid air out and let the cooler LESS humid air in.  Remember that heating the air lowers its humidity.  After the sun goes down, the cooler temperatures should allow the VERY humid air to condense on the glazing and run down the sides to drain away. 

Hope that helps.

[jim king]

Left Coast Chris:

We live here in the middle of the Amazon and there is no rock under us just mud and clay. When they have a severe quake in the mountains it has a hard time getting this far as the soft soil just isnt compatable with earth quakes.  One advantage to living in the biggest swamp in the world.

[Left Coast Chris]

Thats good Jim,   then maybe you just need to cover vertical loading, wind loading and shirnkage.   

[Meadows Miller]

Gday CRTD

I have an advanced ticket in timber drying for the amount You will be processing Id be looking towards a systym settup like this a handfull of solar predrers followed up by a direct fired gas kiln or wood fired hot water kiln use the predryers to get the timber down to EMC about 20 to 25% then use the med/high temp kiln to finish of to the desired MC % as this will give you the slow start needed on tropical H/woods followed by the high temp needed to finish it off as it gets harder to get the bound moisture out of the cell walls of the timber .

From what Ive seen of DH kilns they can have prolems in hi humidity or cold wet climates as the draw air from outside the kiln aswell like an AC  they have to dry the air from outside aswell before it enters the kiln and they take along time to get the timber down to the 10% or lower mark  .

with Your final MC for shipping You can get a map of the average MC for most areas in most countrys around the world as a genaral rule of thumb coastal and high altitude areas have a higher final MC than inland areas (eg) Melbourne vic aust has an avv of 16%mc compaired to Heathcote 13% 75miles inland to Mildura 250 miles inland at avv 9% mc for timber structures. We just vary the MC to suit the destination overhere

I have a Mate who runs a company called sheppard systems that manufatures some of the largest H/wood kiln opperations in australia I used to run one of the largest H/wood kiln operations in aust for 18 months drying Tassy?Vic Oak at 60000bft every 24hrs 7 days a week . I can ring Ron and ask him if he has setup or supplyd any kilns to dry Teak or any of the other speices that You are sawing as I know He has settup kilns on many of the pacific islands His kiln kits  run from $8000 aud + with an owner built chamber

To start with Id need an oven dry sample where you measure the size/vol and weight of the peice  Green and then put it in a fan forced oven at 300 oF and dry it untill it stops losing weight it might take a few days then measure the final weight .

Reguards Chris