Cody Colston
05-08-2011, 11:22 PM
This was more carpentry than woodworking but it is woodworking related and was definitely a project, just completed today.
Late last year I was gifted with some Walnut trees from a friend (they had died) and I had them milled into 4/4 lumber...about 600 bft. I decided to build a solar kiln to not only dry the Walnut to 8% - 9% MC but also to dry future wood that I have milled or even purchased wood that is not sufficiently dry for furniture building.
I based the design loosely on one from American Woodworker Magazine http://americanwoodworker.com/blogs/projects/archive/2009/09/29/solar-kiln.aspx?T=Outdoor&id=v0_2 which was in turn based on one of Dr. Gene Wengert's kiln designs. Mine is sized for 300 bft of lumber and loads from the front.
I framed in the base with landscape timbers and dumped gravel into them to form the base for the kiln. I used the gravel vs a concrete slab so that if I moved the kiln in the future, I could simply scoop up the gravel and re-use it vs the slab which is semi-permanent. The base frame is 2 x 6 PT lumber with wire mesh installed to hold the insulation above the ground. The base framing is covereed with two layers of 1/2" PT plywood with a sheet of 4 mil plastic in between.
194038 194039 194040
The framing was all 2x4 PT lumber. The roof will slant 37 degrees which is the latitude here (32 deg) plus 5 degrees as a compromise for winter drying.
194041
I sheathed the outside with 3/8" Plybead siding and framed the hinged roof with 2x2's to reduce the weight. The clear, Suntuff solar panels were from Home Depot. They are supposed to be UV resistant. I used the corrugated foam (painted black) to seal them top and bottom. Later, I added an unpainted strip on top of the plenum to seal it off for air circulation.
194049
The iside walls are covered with 1/2" PT plywood. The walls are insulated with R-11. The plenum, which holds the fan, is placed 10" from the rear wall and there are 2 upper and 2 lower vents. Everything inside got a coat of flat black paint for heat absorption and I stained the outside with a slate-gray stain. The walls need to be able to breath to get rid of any moisture that gets in the insulation.
The fan is from Nasco and is rated for 1500 cfm. There's a formula to determine needed air flow, depending on the kiln capacity. The 1500 cfm is more than sufficient for the 300 bft kiln .
194052
Loaded with 300 bft of Walnut...30" deep stack x 10' long x 12 layers at 25 bft/layer.
194056
I had intended to use some leftover black naugahyde that LOML was gonna toss as a curtain on the bottom of the plenum but it wasn't long enough to span the width. So, I substituted with some leftover Plybead. At some point I'll have to get a black tarp or something to make the kiln more flexible as to capacity. The plybead only works with this size stack or taller. It's purpose is to force the fan air through the stickered stack vs just returning over the top of it.
I placed a couple pieces of 1/2" PT plywood on the top stickers and set three cinder blocks on top of it to weight the stack. I ran out of black paint and will have to paint the cinder blocks later.
194057
Late last year I was gifted with some Walnut trees from a friend (they had died) and I had them milled into 4/4 lumber...about 600 bft. I decided to build a solar kiln to not only dry the Walnut to 8% - 9% MC but also to dry future wood that I have milled or even purchased wood that is not sufficiently dry for furniture building.
I based the design loosely on one from American Woodworker Magazine http://americanwoodworker.com/blogs/projects/archive/2009/09/29/solar-kiln.aspx?T=Outdoor&id=v0_2 which was in turn based on one of Dr. Gene Wengert's kiln designs. Mine is sized for 300 bft of lumber and loads from the front.
I framed in the base with landscape timbers and dumped gravel into them to form the base for the kiln. I used the gravel vs a concrete slab so that if I moved the kiln in the future, I could simply scoop up the gravel and re-use it vs the slab which is semi-permanent. The base frame is 2 x 6 PT lumber with wire mesh installed to hold the insulation above the ground. The base framing is covereed with two layers of 1/2" PT plywood with a sheet of 4 mil plastic in between.
194038 194039 194040
The framing was all 2x4 PT lumber. The roof will slant 37 degrees which is the latitude here (32 deg) plus 5 degrees as a compromise for winter drying.
194041
I sheathed the outside with 3/8" Plybead siding and framed the hinged roof with 2x2's to reduce the weight. The clear, Suntuff solar panels were from Home Depot. They are supposed to be UV resistant. I used the corrugated foam (painted black) to seal them top and bottom. Later, I added an unpainted strip on top of the plenum to seal it off for air circulation.
194049
The iside walls are covered with 1/2" PT plywood. The walls are insulated with R-11. The plenum, which holds the fan, is placed 10" from the rear wall and there are 2 upper and 2 lower vents. Everything inside got a coat of flat black paint for heat absorption and I stained the outside with a slate-gray stain. The walls need to be able to breath to get rid of any moisture that gets in the insulation.
The fan is from Nasco and is rated for 1500 cfm. There's a formula to determine needed air flow, depending on the kiln capacity. The 1500 cfm is more than sufficient for the 300 bft kiln .
194052
Loaded with 300 bft of Walnut...30" deep stack x 10' long x 12 layers at 25 bft/layer.
194056
I had intended to use some leftover black naugahyde that LOML was gonna toss as a curtain on the bottom of the plenum but it wasn't long enough to span the width. So, I substituted with some leftover Plybead. At some point I'll have to get a black tarp or something to make the kiln more flexible as to capacity. The plybead only works with this size stack or taller. It's purpose is to force the fan air through the stickered stack vs just returning over the top of it.
I placed a couple pieces of 1/2" PT plywood on the top stickers and set three cinder blocks on top of it to weight the stack. I ran out of black paint and will have to paint the cinder blocks later.
194057