The Forestry Forum

General Forestry => Drying and Processing => Topic started by: CedarDude on June 25, 2016, 11:27:07 PM

Title: Bi-fold solar kiln doors
Post by: CedarDude on June 25, 2016, 11:27:07 PM
Just finishing up my solar kiln. I built it with four bi-fold doors spanning 16 feet. Sliding barn door hardware supports the center corners of the innermost two doors. I guesstimate each of the four doors weighs over 100 pounds. There is absolutely no sag and the doors will open with one finger. Cane bolts on the inside secure them closed.

(http://www.forestryforum.com/gallery/albums/userpics/41183/image~0.jpeg)


(http://www.forestryforum.com/gallery/albums/userpics/41183/image~1.jpeg)

The four ~4 ft. x 7 ft. door sections (actually more like wall sections) were constructed in the shop with 2x4 lumber dried in the shop, trued on the jointer, built flat and squared, insulated with fiberglass and sandwiched with 1/2 cdx plywood glued and screwed to the framing - very strong with little potential for sag or warp. The doors were hung using three 12 inch barn door hinges at each of the sides (with corresponding blocking built inside the doors) and three 4 inch door hinges in the centers. They were hung with 1/4 gap all around, at the most, and then T111 siding was screwed on slightly oversized to the outside to cover the gap top, bottom and between the center of the bi-folds. A 1/2 inch vertical gap in the very center of the two sections was necessary for clearance when opening and closing. A 1x4 was screwed to the back of one door on the inside to close the gap. The doors fit tight enough that any further weather stripping seems unnecessary and the short roof on the back helps keep most of the weather off the doors. The cane bolts on the inside snug them up well against the jamb and make it impossible for anyone to be shut inside while also allowing the building to be secured from the outside with a single lock on the access door.

(http://www.forestryforum.com/gallery/albums/userpics/41183/image~3.jpeg)

The bi-fold doors limit the 16 foot opening to an effective 13+ foot opening which is fine for my purposes. Loaded the kiln today with mostly 12 and 13 foot 12/4 cedar with no access issues.

The kiln is roughly 7 feet by 17 feet inside with a 12/12 collector roof. Glazing is triple wall polycarbonate (double cell) on 2x6 rafters 2 ft. OC with 1x4 horizontal boards at 3 ft. OC. Black metal roofing is screwed onto the rafters underneath as a collector. Four solar powered fans blow out of the plenum (horizontal plywood extends from bottom of fan shroud forward to rafters to create a triangle plenum) down across the roofing and out at the front of the kiln. Air recirculates back through the lumber. Floor is 2x8 and walls 2x4 with fiberglass insulation. A narrow insulated 24" access door is on the side. Fan plenum is just over my height to allow easy access.

All interior walls are 1/2 cdx ply over plastic vapor barrier and insulation. All joints, holes, etc. we're caulked prior to painting for a good seal. Interior walls were painted with 2 coats of aluminum paint and then flat black (in case I ever want to try the kiln without the metal roof panels) Floor is 1 inch signboard ply (has waterproof resin coating) over 2x8 on 16 inch Centers. Floor was painted with 4 coats of aluminum paint. I might put on some type of porch paint or rubberized coating on the floor in the future depending on wear and water absorption.

I still need to clean up a few small details and hang the tarp from fan plenum. I think I spent more time painting than building. But really happy with bi-fold walls. Work really well.

(http://www.forestryforum.com/gallery/albums/userpics/41183/image.jpeg)
Title: Re: Bi-fold solar kiln doors
Post by: ljohnsaw on June 26, 2016, 01:42:06 AM
Wow, really nice job on that kiln!  Great doors, too.  Its nice when the plan comes together :)
Title: Re: Bi-fold solar kiln doors
Post by: CedarDude on June 26, 2016, 01:48:17 AM
Wow, really nice job on that kiln!  Great doors, too.  Its nice when the plan comes together :)

Thanks! Yep, I overthought those doors for many hours and still wasn't sure they would work right. Came together though!
Title: Re: Bi-fold solar kiln doors
Post by: GeneWengert-WoodDoc on June 26, 2016, 06:36:53 AM
Looks great indeed.  One caution...if the wind catches a door, you should have a stop, like a post in the ground, to catch the door before it puts torque on the hinges.
Title: Re: Bi-fold solar kiln doors
Post by: scsmith42 on June 26, 2016, 11:11:07 AM
That's the nicest looking solar kiln that I have seen! Excellent attention to detail and craftsmanship!  I like how you mounted the doors.

The stickered lumber inside the kiln appears well done too.

Thanks for sharing.
Title: Re: Bi-fold solar kiln doors
Post by: CedarDude on June 26, 2016, 12:52:51 PM
I forgot to mention the floor. I've seen where people build the floor framing, screw on the plywood and then flip the whole thing over. At 8' x 18' that seemed a bit much. Instead I used joist hangers to put a few 2x4s between the 6x6s (that sit on posts at 4' OC). Then I put down my 1/2" ply and the floor joists on top of that. I did have to crawl under later to screw the ply up into the bottom of the joists but better in my mind than trying to flip the whole assembly.

(http://www.forestryforum.com/gallery/albums/userpics/41183/image~4.jpeg)
Title: Re: Bi-fold solar kiln doors
Post by: stanwelch on June 27, 2016, 07:24:54 AM
Very nice solar kiln !!  Excellent attention to detail.  8)

What solar fans did you use ?
Title: Re: Bi-fold solar kiln doors
Post by: CedarDude on June 27, 2016, 03:50:36 PM
Wish I could recommend a fan. I bought five in a package with panels online. Stainless shrouds, pretty flimsy, had to resolder a couple of connections but they work well enough, the ones that work. One brushless motor was broken on arrival and the 5 year warranty is only good if they will reply to your emails, which they won't. Still trying. Company name rhymes with "sand."
Title: Re: Bi-fold solar kiln doors
Post by: CedarDude on June 27, 2016, 05:37:49 PM
With 1100 bf of 12/4 western red cedar at 11-15% MC, temp of air exiting the pile reached 120f by 1pm (40 degrees over outside air temp). I opened all 6 upper vents and it maintained that temp. Still over 100F at 8pm. Nice and cool by morning.
Title: Re: Bi-fold solar kiln doors
Post by: flatrock58 on July 03, 2016, 08:57:31 AM
Looks like you did a great job.  I like it!  When I finally build my kiln I will be copying your design.
Title: Re: Bi-fold solar kiln doors
Post by: jim blodgett on July 03, 2016, 11:06:13 AM
That looks really nice, CedarDude.  I looked on a map and Matlock is pretty close to us, certainly similar climate/solar gain potential. I'm really looking forward to reading in the coming months/years how your kiln performs.

If you don't mind me asking, where did you get the polycarbonate (I think that's what you said) glazing material for the solar collector side of your roof?

Thanks.
Title: Re: Bi-fold solar kiln doors
Post by: CedarDude on September 13, 2016, 10:04:36 AM
Sorry for the late reply! Yep, you're just down the road.

I bought my panels through an agricultural supply company in Auburn called McConkey's. Really good price.

Kiln has performed really well. Max temp reached was 135F in the middle of the pile. Cedar dried flawlessly but I had to slow things down since the 3" stock was drying too fast on the outside. Reached a consistent 7 percent MC in 8 weeks. I've milled it with no issues showing up.

Also, since I used metal roofing panels under the glazing the temp in the kiln does not heat up much with the fans turned off. This works well for me since I'm only drying for my own woodworking biz and am now using the kiln as lumber storage (and there is never enough of that). When my supply gets low, I'll pull out what's left, store it in the shop and put in another load.

The cost savings from the first load (buying air dried versus kiln dried, which is even tough to find in 3" thickness) paid for the cost of constructing the kiln, and I have control over the drying.