Author Topic: Solar dry kiln construction (Read 8785 times)

Planman1954 · « **on:** April 13, 2011, 07:44:01 pm »

Hi all.
   This thread may be a bit premature, but I'm excited about a solar drying kiln that I'm about to start on. The design will be based on pineywoods design. His solar kiln heats up during the day to 160 degrees and cools down at night. This allows the wood to dry with less wood stress, avoiding splitting.
   I plan on making the kiln about 5' wide x 18' long, and bolt on an axle and tube for a hitch that my Norwood lumbermate uses so that I can tow it around the yard. I also plan to have the door panels made in sections that are easy to remove...and possibly hinge one on the end for easy in and out access during the drying process.
   I cut out all the pieces last week out of SYP so it can dry for about a month before I start the assembly. The only big expense will be the translucient panels for the top. I'll post start to finish pictures when I get started in a few weeks. I'm pumped!

Jasperfield · « **Reply #1 on:** April 13, 2011, 08:56:34 pm »

If it turns out as well as did all of those doors that you made, it should be pretty nice.

WDH · « **Reply #2 on:** April 14, 2011, 07:51:42 am »

I am really interested in this as well, so I look forward to your experience. I saw the Pineywoods design, and it is different in how the solar collector is designed (say versus the Virginia Tech design), so that might explain how he gets a much higher temp than others can achieve.

Bill Gaiche · « **Reply #3 on:** April 14, 2011, 08:21:09 pm »

Planman1954 , I plan on starting my kiln in about 30 days. Have had loblolly pine cut for about 3 weeks. Mine will be 6' x 12'. Have bought and recieved 2 gable vent fans for air circulation. Like you said the plastic covering isnt cheap. About $28.oo at Lowes for 12' x 2'. The treated plywood isnt exactly cheap for the interior either. What kind of siding are planning on doing? Good luck and do some good photos as you go. bg

Planman1954 · « **Reply #4 on:** April 14, 2011, 11:28:11 pm »

10-4 Bill.
Here's a couple of pics of the lumber I'll use:

The top pic starting from the right are some 6"x6" cross members for the base beams. Next is 3"x6" stock that I will laminate with bolts and large nails to make the long 6"x6" support beam. Next are 2x4"s for the floor joists, top and bottom plates, and upper rafters. Next are 1"x12"s for the floor. (I wish I had cut them 3/4" thick since they will bear no weight...only keep air in.) Finally, sort of out of the picture, are some 3/8"x8" boards for the interior walls, and 8" lap siding for the exterior. The bottom pic is some 2x4s for the walls, some 1x4s for the door frames, as well as some more siding and interior boards. I think you'll see it all come together when I start the build around the middle of May. Take care.

pineywoods · « **Reply #5 on:** April 15, 2011, 10:24:05 am »

Planman came visiting and measured, sketched and looked over my kiln. He got it, this thing is nothing but a chicken coop with a plastic roof . His should be an improvement over the original in several ways. Added length will allow drying 16 ft lumber. I welded up my door frames out of 1 inch square tubing, he has figured out a way to make doors from free wood. Planman's location is just about ideal from a solar standpoint, top of a bare hill with un-obstructed view to the south. His place is about 4 miles from me, so I plan to make a pest of myself when he starts construction.

Bill Gaiche · « **Reply #6 on:** April 15, 2011, 11:53:40 am »

pineywoods , He may very well put a hammer in your hands so you may not be the pest of the neighborhood that you claim to be. I am going to pick up some treated plywood today for the interior, 1/2" @ $15.00 per sheet.
Planman1954, looks like you have good start on the lumber. bg

WDH · « **Reply #7 on:** April 15, 2011, 08:20:55 pm »

Maybe the Grouchy Old Men will make an appearance

.

Fil-Dill · « **Reply #8 on:** April 15, 2011, 08:42:27 pm »

Are you using the attic vent fans only. I picked up 3-12" all metal fans today at Orshlens and they are 3 speed and cost 24.99 each. I have one in my shop that has ran for years at 8 hrs a day. I wondered if anyone has tried them in a kiln where the temp. will be higher. They also carry a 16" , 3 speed for 29.99 each.

Planman1954 · « **Reply #9 on:** April 17, 2011, 12:26:23 am »

Fil-Dill:
I plan on using 1 or 2 simple box fans mounted facing down, just as pineywoods has done. It works well. If one dies, I'll get another. They're cheap!

Woodey · « **Reply #10 on:** April 17, 2011, 09:54:01 am »

How do you get the temp. up to 160 degrees during the day ?
I would to know more about the pineywoods kiln system.

Fil-Dill · « **Reply #11 on:** April 17, 2011, 07:44:10 pm »

Do you think I can get by with vinyle siding on the outside? It is grey and I have alot of it around.

pineywoods · « **Reply #12 on:** April 18, 2011, 10:39:55 am »

Vinyl, wood, old roofing metal, construction board, plywood etc. Just about anything will be fine for siding. It's nothing but a small building with a south-facing clear plastic roof. What's different from other designs is the amount and placement of the metal collector panels. Wood is a lousy solar collector. What you need is metal painted flat black. fastening the metal to the bottom of the rafters has 2 advantages. 1. more room to install more collector, about 50% more. 1.. The collector is perpendicular to the suns rays which ups the effeciency considerably. There's pics and drawings in my photo gallery.

pyrocasto · « **Reply #13 on:** April 18, 2011, 05:50:57 pm »

Metal collector is nice but not needed. I havent even finished mine and without the doors being painted black yet(about half the sunlight hits them) it already hits 160 sitting in good sun. As long as light isnt reflected back out anything will soak up the same amount of heat. The main heat loss in a solar kiln is the plastic/glass for the sun to come in. That's why doubling up on the glazing is suggested.

For mine to keep the price super cheap I used a green house plastic rated for 5 years. PVC corrugated panels yellow the same, so unless you use glass or fork up for polycarbonate the 6mill greenhouse plastic works just as good.

I've spent several years in DIY solar projects and my solar heating panels at home use a furnace filter for the collector, which actually works better than the metal collector I originally built.

Planman, have fun. It may get frustrating at times since it's a large kiln but it's always worth it. I have to tweak my doors, finish coating, add the fans, and I'll be done with mine.

Problems I ran into:
Trying to fix the doors too tightly. Put a door jam in and move along. The kiln will tweak back and forth with the weight of the huge doors.
Tar. I will never use tar again just because it's so nasty, takes FOREVER to dry, and gets nice an soft again every time it gets hot for a long time. I'd rather spend the money on a elastomeric coating and either tent it black or paint over top. At least then I can spray it on.

Planman1954 · « **Reply #14 on:** April 18, 2011, 06:41:12 pm »

Hey pyro....nice post. How bout a photo of your kiln? Also, i plan on doing the access area a little different than just large doors. You'll see...if I can figure out what I'm doing!! I will post photos as I go along. Pineywoods design dries wood in about 2 to 3 weeks. What do you think yours will do? Again..thanks.

WDH · « **Reply #15 on:** April 18, 2011, 08:34:41 pm »

Piney,

Have you dried much oak? Would 160 degree temps dry the oak too fast and lead to case hardening and honeycomb? I know pine can take it, but I am concerned about hardwood and oak especially as I cut 98% hardwood.

pineywoods · « **Reply #16 on:** April 18, 2011, 09:03:45 pm »

WDH that 160 deg figure is just a bit misleading. It does get that hot on a good sunny day, but it don't stay that hot. The average temp over a 24 hour period will be much less. Cools off to close to outside temp at night.How much it cools off is highly dependent on species and the size of the stack. That allows the wood to stabilize and moisture to migrate slowly to the surface. I ran a batch of 4/4 air dried pin oak (really water oak) through mine for about a month. Moisture meter said 6%. I made tongue and groove flooring from it, nailed it down to a plywood base, NO shrinkage. On the other hand, some 14 inch wide pine wall paneling did shrink a little after I nailed it up. When it comes to solar kilns, published drying temps and schedules are useless. One stack may dry ok in a month, the next similiar stack may take twice that long. There are just too many variables.

pyrocasto · « **Reply #17 on:** April 18, 2011, 10:12:49 pm »

Planman, I don't know about dry time since that varies a lot with load size, location, weather, etc. Looking seriously forward to putting a stack in it though. I'll try to get a couple pics up at work as my computer busted. Look forward to seeing yours.

Piney, do you adjust your vents much during loads or for different species? Hopefully my first bat h of 1000ft 4/4 maple turns out without any issues.

pineywoods · « **Reply #18 on:** April 18, 2011, 10:46:32 pm »

Quote from: pyrocasto on April 18, 2011, 10:12:49 pm

Piney, do you adjust your vents much during loads or for different species? Hopefully my first bat h of 1000ft 4/4 maple turns out without any issues.

There are no vents on either of my kilns. I use a cheap room de-humidifier running at night to take the moisture out.

thecfarm · « **Reply #19 on:** April 19, 2011, 07:55:47 am »

Plansman,we used box fans,at $10 each than,in our greenhouse for 3 years.They would run steady,24/7 from Feb-March until late June.Never burned one out.I told the wife,they won't last long. Sure was wrong on that.They are stored in the old farm house now.

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Author Topic: Solar dry kiln construction (Read 8785 times)