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Question on solar kiln drying

728 views 4 replies 4 participants last post by  WDHLT15 
#1 · (Edited by Moderator)
Hello all,

I received a commission of building a 14'x5' conference table out of 8/4 white oak slabs. They were felled years ago but not sawn nor painted on the ends. Ah well.

They're sawn now, and each slab is 8' long and between 20"-30" wide. Initial moisture content checked out around 25%.

They're now stacked inside a solar kiln a friend of mine built, and they've been in about 3 weeks. I'm not sure if all solar kilns operate on the same principle, but this is one with an angled clear plastic roof, it's painted black on the inside, and has fans and vents placed according to a common online design.

Anyway - time to get to the point. I ran b there today to check the moisture content, but I was reluctant to rip a slab all the way down the center to test for it. Instead, I took one of the 4' slabs and ripped a piece off the edge, about 2" in. The moisture content read 15%.

So: guys with experience, do you think that's fairly representative of the lumber all the way through, or does lumber dry quickly from the edges out (towards the bark)?

I'm on vacation for a week starting Saturday, then I'll come back and most likely rip a piece in half. I just want to avoid doing this more than I need to, so doing it too early could possibly end up wasting usable lumber (maybe not, maybe I'll need some ripped pieces anyway, but I haven't drawn up plans yet).

Thanks
 
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#2 · (Edited by Moderator)
If you cut into the slab and checked the core reading, then it's a representative sample of the moisture content. Make sure to put the moisture meter probes at the center of the slabs thickness, and take several readings.

As to weather the slabs all dried the same, that may be a question of how good the air circulation is in your friends kiln. For mine I use 4 ceiling mounted attic fans so there are no dead spots in the kiln. 15% is pretty good for a slab. 12% is even better. For milled lumber I'm looking for 6-8%.
 
#3 ·
So that's a good measure, despite only ripping 2" into the long edge of the board? Excellent.

And can you clarify your comment regarding 15% being good for a slab? Do you mean that you find it acceptable to be sold a slab at that content, and then you dry it further, or are you suggesting that you would begin working with a slab at 15%?

Thanks
 
#4 ·
If you cut into the slab and checked the core reading, then it s a representative sample of the moisture content. Make sure to put the moisture meter probes at the center of the slabs thickness, and take several readings.

As to weather the slabs all dried the same, that may be a question of how good the air circulation is in your friends kiln. For mine I use 4 ceiling mounted attic fans so there are no dead spots in the kiln. 15% is pretty good for a slab. 12% is even better. For milled lumber I m looking for 6-8%.

- pintodeluxe
Pinto, why don't you give him a link to your article on solar kilns.
 
#5 ·
Patience. 8/4 white oak will dry slow. 3 weeks is probably not enough time starting from 25% from my experience. Your 2" slice off the edge is likely not representative of the core moisture in the slabs. For my thick slabs, I shoot for 10% or less.
 
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