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Question on solar kiln drying

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Forum topic by Mark posted 10-04-2018 04:40 PM 316 views 0 times favorited 4 replies Add to Favorites Watch
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Mark

56 posts in 696 days


10-04-2018 04:40 PM

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


4 replies so far

View pintodeluxe's profile

pintodeluxe

5951 posts in 3233 days


#1 posted 10-04-2018 05:07 PM

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%.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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Mark

56 posts in 696 days


#2 posted 10-04-2018 05:29 PM

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

View RobS888's profile

RobS888

2604 posts in 2265 days


#3 posted 10-04-2018 05:51 PM



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.

-- I always knew gun nuts where afraid of something, just never thought popcorn was on the list.

View WDHLT15's profile

WDHLT15

1816 posts in 2896 days


#4 posted 10-06-2018 12:28 PM

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.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT40HD35 Sawmill. Nyle L53 Dehumidification Kiln. hamsleyhardwood.com

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