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Best Practices For Drying Large Slabs + Solar Kiln Design Details

Started by Mulekicker, March 09, 2016, 02:06:16 PM

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Mulekicker

Hi Everyone,

I'm very new to the milling and drying world, just purchased an LT-15 last fall and have been working pretty hard milling  fir, cedar, elm and soon a bunch of red alder. Several thousand BF is stacked and stickered and I've decided its going to be worth my while to build a kiln.  The location of my mill site has no power, so solar is the only viable option.  I'm buying the shell of a DH kiln from a friend, which consists of insulated freezer panels.  I'm going to modify the design to accommodate a double wall polycarbonate solar collector, add solar panels and DC fans, and possibly mount the entire thing on an old trailer frame I have to make it portable. That's another story though and I'm going to post a separate build thread on that once I pick up the panels in a couple weeks.

I'm trying to decide how big to make the kiln right now and although I've been reading quite a bit on drying, there were a few points that I wanted to clarify, and some ideas to get feedback on.

1.  I feel like I've read comments here that state the sooner you get a log from the stump to sawmill to the kiln, the better quality wood and yield you will achieve.  I also have read that the best way to avoid defects and degrade losses for lumber is to dry it slowly, especially with thicker boards/slabs. I feel like there is truth to both comments, and the specific species, size and location where the air drying is happening, and type of kiln are all variables that come into play. Is there a specific "best practice" method for drying large slabs? Or are there just too many variables to make a broad statement like that?

I am located in southern oregon, which has cool, humid winters (and most of spring and fall) with very hot, dry summers. I am also concerned that even if I had the slabs under a covered shed, the hot summers might dry them out faster than is ideal...

2. I have a number of large 3" thick tabletop slabs milled in the last several months, with some more on the way, and I'd like to accelerate the drying process beyond basic outdoor air drying if possible. My thought is that a solar kiln would be ideal because I could control the venting and allow the slabs to dry pretty slowly, thus keeping the RH quite high both day and night. I would need to size the collector to BF ratio so it would draw out less moisture than some of the typical solar kiln designs and I realize this would take a long time. However, I am thinking about making the kiln large enough to accommodate a large stack of thick slabs on one side, and another stack of 4/4 boards on the other.  Once the 4/4 boards dry completely, I would replace them with another stack of the same, thereby allowing me to work through the boards I have coming off the mill, but still having space for the slabs to sit there and continue to dry. This would break the "rules" of not mixing sizes and species, but I also thought it would be pretty easy to just hang a tarp or canvas between the two stacks and be able to adjust the venting separately, which would basically make it function like two separate kiln chambers. Thoughts? Comments? Concerns?

As always, thanks for reading and advising!

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