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Another Solar Kiln Build

Started by Josef, June 11, 2016, 10:33:14 AM

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Josef

Hi Guys,

In 2014 I had the pleasure of sitting thru a seminar with Gene Wengert in Ohio, where we learned about lumber grading, drying and the VT solar kiln he helped design. I left with lots of new knowledge, several descriptive handouts and a goal to build a solar kiln.

Since I have actually gotten something accomplished on my solar kiln build I though I'd try to document the build here. I was able to build it almost completely with scrounged materials, lumber from my sawmill and bartered parts.

Starting with the frame. I built the frame upside down to bolt together the joists and runners. The joists are 3 x 7 ash on 24 inch centers and the runners are 6 x 10 ash. I chose to bracket and bolt the frame base to get the strongest joint possible. The base frame is 19' x 10', the chamber is 18' wide. The bottom is skinned in 1/2 inch osb from a barn demo. Flipping it over was a challenge, could lift it with my small forklift, but then had to steady it and move over to the other side to let it down.





Since I'm a one man show I am always getting creative and pray a lot. Next it got stuffed with fiberglass left over from a steel frame build, odd pieces but they worked. Plastic vapor barrier over that (left over from a garage build) and 3/4 t&g plywood underlayment floor (from the barn demo). The wall frame was made of 2x4 and 2x6 from my mill, and 1" shiplap hemlock left over from my barn residing, and more left over fiberglass insulation to fill the voids.



Over that I attached two layers of staggered 1/2 inch foam board insulation ( salvaged from a chicken house demo), with the joints sealed with alum tape. Then to add a wear surface I skinned it with 26 ga painted galvalume (left over trim blanks from a mfg co I had) and added a coat of black absorbent paint in the collector area and white gloss in the lumber stacking area.



The outside collector material is 1/4 in greenhouse panel (left over panels scrounged from a greenhouse refit in town this winter, I had to line up my frame to hit the screw holes in the panels), 9' x 18' in area, at a 45 degree slope. All the exposed material under the collector is metal skinned and painted in flat black except the top of the rafters and the purlins.



The flat roof frame is a box beam made of two 8 inch 14 ga Z purlins (left over from a build in Va) , with 2x6 rafters bolted between them. The fan shroud housing is 2x4 framed, osb skinned and steel stock covered. The collector frame hangs from the bottom of the fan baffle and is supported by a 2 ft high knee wall at the base. The collector material is painted roof sheets (salvaged from a roof repair).



The 4 fans are rated at 1300 cfm each, and are controlled by two thermostats, outside fans coupled together and two inside fans coupled together. One set to come on at 90 degrees, the second at 110 degrees (for now). Both sets will have isolation switches to override the thermostats. All wiring in conduit, two led floods to be able to see inside the chamber with the door closed.



Fans are directed to pull from the load and discharge downward over the collector, and back thru the load. The flat roof area over the load is covered with a metal curved diffuser that holds up the roof insulation and helps with the change of direction of the air at the top of the chamber. Probably not necessary but it was easier than measuring and braking angles in the interior skin panels.



Receptacles at each inside front corner to plug in dehumidifiers, with that supply on a thermostat and relay to shut off the dehumidifiers when chamber temp reaches 110 degrees and then back on at under 90 degrees.

The access door is 2x4 framed, foam insulation filled, painted to seal against moisture, with a latch but no lock and a latch catch that will breakaway with minimal pressure from inside.



The loading opening is 18' wide and 7' high, the door is 18'04" wide and 9'06" high, hinged in the middle horizontally to form a bifold hanger type door. The door frame is welded 1 1/2" square 16 ga tubing, has a stiffening truss at the base, 3" hinges top and middle, vertical frames on 36" centers, and opens to clear the entire opening, both vertically and horizontally.





The door is skinned on the outside with tin roof panels, aligned so that the lap joint is over the door hinge joint, the top hinge joint is covered with a strip of left over rubber roofing spliced together and secured to the roof and door top. The interior of the frame is filled with foam panels and is skinned inside with alum sheet trim material (0.032 white alum coil left over from a gutter job). A flat weatherstrip between the upper and lower panels seal the center joint.



The door is raised by an 880 lb hoist from HF, 110v, mounted in the flat roof frame, thru a system of cables/pulleys/blocks that effectively reduce the lifting load by 50%. The 90 degree cable run change at the top is done with a roller fabled from two left over blade guide rollers changed out in my last mill service. Opening time is about 15 seconds.





Door seals are compressed pipe insulation secured to a backing piece, that the door is pulled into and sealed with pressure from door guides at the bottom and with turn buckles at the center joint.

The vents will be covered with an aluminum door, opened and closed with 120v 4 inch linear actuators, wired to a timer relay that also interrupts power to the dehumidifiers when the vents are open. Not sure if it is a prudent control mechanism but we'll see how it works. I'm going to experiment with a plc or arduino controlled humidistat / thermostat relay to open and close them automatically after I get the first load in the kiln and have time to play with it. See, thats my problem, I can't seem to quit messing with the design and it never gets completely finished. I hear there is a 12 step program for that.

I've got quite a few stacks of air dried QS sycamore to put in there and way too many stacks of 8 and 10 quarter slabs as well so I can't wait to get this thing operational.

I'm hoping I get the picture posting procedure correct, we'll see. Thanks for reading this, I had a lot of fun building it and I'm almost done, just the vents to mount and the interior canvas baffle to hang. Having an indoor place to build it made life a lot easier but also makes it easier to not get into a rush to finish it, we'll see how easy it  is to drag to it's location and level. Ain't retirement great, I wonder how I ever had time to work.

Joe
In my house I'm the boss, I know this because my wife said so, I only hope she doesn't change her mind!

New to me Timber Harvester that I'm learning to operate, been building a home built mill for a while, should be ready to make sawdust with it someday if I ever quit "modifying" the design.

Ljohnsaw

John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

CedarDude

Double wow. Nice!

I'm finishing a kiln right now, same size. I thought I was doing something unique with the horizontal bifold doors using barn door hardware. Your overhead bifold is over the top! I lose a couple of feet in loading capacity with the manual bifolds. Really impressive.

xlogger

Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

Glenn1

I have just begun building a solar kiln and have the base built.  Your kiln is absolutely fantastic and I hope you don't mind me borrowing a few ideas.

Are you using single or double wall polycarbonate panels? 

Also, how much space did you leave betweem the polycarbonate panels and the metal  sheets to absorb heat?
Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer

YellowHammer

YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

Josef

Thanks Guys,

I always seem to over think things, so if it works I'll be pleased. In any case I figure it will be a good place to start learning how to dry wood.

Cedardude, your horizontal bifold doors sound interesting, look forward to seeing how they turn out.

Glenn1, the panels are twin wall, I made sure I installed them in their original direction, as only one wall layer is uv protected. The distance between the poly and the heat absorber panel is 12 inches, can't say if thats a correct distance as I'm pretty much shotgunning it, but it seemed about right. My concern was having too much heat radiating onto the underside of the poly so 12 inches seemed a good compromise.

Thanks for the kind comments, if anyone has thoughts about the temp controls on the fans, vents and dehumidifier please share them, I've never dried a stick of wood, so I'm all ears. I've read a lot of threads about solar kilns here on the FF but reading about it and doing it is a whole different thing. My goal is to make it hands off operational for part of the cycle until it gets close to finishing a load. But as I said I tend to over think things.

Joe
In my house I'm the boss, I know this because my wife said so, I only hope she doesn't change her mind!

New to me Timber Harvester that I'm learning to operate, been building a home built mill for a while, should be ready to make sawdust with it someday if I ever quit "modifying" the design.

WDH

Exceptionally impressive.  Maybe you should build those and sell them.
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

Josef

WDH, I kept track of the materials, but not the time, I was afraid that I'd find out that I could have bought one cheaper than building it if I included an hourly labor rate.

I see you're located in Ga. Last week my wife and I closed on 18 acres in Woodbine, I'm going to build a small retirement house there. My shop (playhouse) here is 12k sq ft, I'm going to downsize to a 5k sq ft shop in Ga. Trying to figure out what part of all my very valuable stuff (wife calls it junk) I'll have to get rid of for the move. Problem with having room to store stuff, nothing seems to get thrown out. I don't like heat or mosquitos, so why am I moving to Ga.?, been married almost 39 years, wife said we're moving to Ga, so I guess we're moving to Ga. I'm scared the skeeters will like this yankee blood too much.

Hope I can load a 10 ft high 10 ft wide solar kiln on a trailer to take with me. Buddy has trucks and trailers and hauls wide loads al the time, we'll see. If not I guess the next one will be quicker to build.

Joe
In my house I'm the boss, I know this because my wife said so, I only hope she doesn't change her mind!

New to me Timber Harvester that I'm learning to operate, been building a home built mill for a while, should be ready to make sawdust with it someday if I ever quit "modifying" the design.

GeneWengert-WoodDoc

Thanks for your kind words.  However, I must have forgotten to,mention a key point about a solar kiln...it needs to be outside in the sun.  Other than that, it is fantastic.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

WDH

You will enjoy the coast.  Make sure that the shop has air conditioning  :)
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

sandsawmill14

 :o :o :o how much would you charge to build me one minus the electric ??? or you could just drop that one off in TN on your way to georgia ;D :D :D :D very nice build :)
hudson 228, lucky knuckleboom,stihl 038 064 441 magnum

Josef

Gene, I knew I missed something, be sure to include that very pertinent point in your next presentation  :D

WDH, yep, air conditioning is my friend, will love being only a few water miles from the ocean too.

Sandsawmill14, if you'll note the timing, it was in 2014 that Gene lit the fire under me to build this, it's now a year and a half (two winters) later and it's still not quite done, almost but not quite. Family says I have the attention span of a gnat and the memory of a goldfish, so "gettin' er done" can be a challenge. But if I don't take it with me when we make the move you can come get it. You might be jumping the gun a bit though, we don't even know if it works yet.

Joe
In my house I'm the boss, I know this because my wife said so, I only hope she doesn't change her mind!

New to me Timber Harvester that I'm learning to operate, been building a home built mill for a while, should be ready to make sawdust with it someday if I ever quit "modifying" the design.

sandsawmill14

i know what you mean about getting things done :D :D :D
hudson 228, lucky knuckleboom,stihl 038 064 441 magnum

GeneWengert-WoodDoc

We built six kilns at the Marc Adams School in Indy a month ago.  That is the way to go as you have a few other "solar kiln in my mind for the past few years" guys there plus me.  Actually we only did one kiln complete and the rest were all the parts that were cut to exact size so the kiln could be hauled home and assembled there.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Josef

Gene, were the kilns built at Marc Adams School last month the original VT kiln or were they constructed with newer features? Has the technology changed since the original design was adopted. My build was guided by your research as well as lots of reading here on the FF from builders sharing their experience. I love to learn and being an engineer by trade have an innate need to understand how things work. Love you guys and your willingness to share what you've learned making it easier for us newcomers to accomplish our goals.

Thanks,
Joe
In my house I'm the boss, I know this because my wife said so, I only hope she doesn't change her mind!

New to me Timber Harvester that I'm learning to operate, been building a home built mill for a while, should be ready to make sawdust with it someday if I ever quit "modifying" the design.

GeneWengert-WoodDoc

The Marc Adams kiln was a VT design except only 9.5 inside length and holds up to 800 BF.

The design of the VT kiln is based on functional simplicity and low cost. Technology has not changed. You can spend more money and get foam insulation, double wall polyester clear cover, vents that open and close based on interior humidity, etc. All these are small improvements and so may not be worth the cost.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Solomon

I'm going to read your post about 20 more times.   I am getting ready to build a Solar kiln to stand right beside my shop 24 or maybe 26 ft wide,  And I am wanting to locate the doors on the other side to be able to build it next to the shop and still have the sun comming through the glass.
I don't know if it can work that way or not,  I know about as much about building a kiln as I know about Eienstien's theroy of Relativity.  (NOTHING)
  I do know that you've got to have a path to get rid of the moisture and for that you need air flow.
Other than that, I am cluless.  But I'm gonna give it a shot.
I also need to relearn how to post photos on here.  I wish they would make that easier to do.
Time and Money,  If you have the one, you rarely have the other.

The Path to Salvation is narrow, and the path to damnnation is wide.

Josef


When I started this kiln build I knew nothing about drying lumber, now that it's about done I still know nothing about drying lumber but am ready to learn.

Now building is something I can get a handle on, I always maintained to my customers, show me what you want and we'll get it figured out, my job is to build it, yours is to pay for it. One aspect of building a long trapezoidal structure with a large high wall opening is supporting the roof, I was fortunate to have several 25' Z purlins laying around and it worked, with your solid high wall you really simplify the structure framing, but loading thru the end becomes problematic (read labor intensive) but in reality how many times a year will you do that? Maybe 6 or 8?

Smaller end door, easier to seal, easier to hang. I had visions of a layout like you're planning before we decided to shift the farm to Georgia, long sections hard up against the shop wall, and during the winter when drying lumber is iffy I'd just exhaust any heat generated into the shop for additional heating. Gets cold in western Pa.

Joe
In my house I'm the boss, I know this because my wife said so, I only hope she doesn't change her mind!

New to me Timber Harvester that I'm learning to operate, been building a home built mill for a while, should be ready to make sawdust with it someday if I ever quit "modifying" the design.

CedarDude

In a lot of ways our kiln designs are very similar (minus the overhead bifold doors and steel i-beam header!). Roughy the same size and collector design, even the insulated access door. I'm also using metal roofing panels and the same airflow pattern. Installing panels today, in fact.

I'm interested though that it doesn't appear you have any air intakes at the top of the kiln?

Also, I'm putting my baffle (poly tarp) at the bottom of the metal panels (front of kiln). Are you doing this as well?

Josef

My baffle is a canvas tarp hung from the bottom of the fan truss. There are two vents at the top of the door placed just below the header frame when the door is closed as well as two vents at the bottom of the door. I'll get pics when I get it placed on its outdoor pad. I just got the door seals worked out, looks like the foam pipe insulation will work well when compressed in place.

Joe
In my house I'm the boss, I know this because my wife said so, I only hope she doesn't change her mind!

New to me Timber Harvester that I'm learning to operate, been building a home built mill for a while, should be ready to make sawdust with it someday if I ever quit "modifying" the design.

CedarDude

Ahh, in the doors, that makes sense.

I'm debating placement of the tarp. With the metal collector, I think it could go either under the fan shroud near the back of the kiln (as with standard VT design) or at the bottom of the sheet metal near the front of the kiln (if it was draped back over the pile). Not sure. Probably better the traditional way.

Josef

Not sure it makes much difference, the use of the baffle relegates the space under the metal collector to dead space with no appreciable air flow without creating some sort of turbulence in that void. I chose to hang the baffle from the overhead merely to make it's placement over the lumber easier. In most VT designs I believe the baffle serves double duty and acts as a collector as well (like painting the interior black) because it's open to the transparent roof panels. In our kilns we placed the metal collector between them so I'd say securing the hanging baffle high or low depends on how it affects the ease of it's use in your design.

Joe
In my house I'm the boss, I know this because my wife said so, I only hope she doesn't change her mind!

New to me Timber Harvester that I'm learning to operate, been building a home built mill for a while, should be ready to make sawdust with it someday if I ever quit "modifying" the design.

Josef

Hi Guys,

well, I've had a chance to put a couple of loads thru my solar kiln, thought I'd update this thread with my initial observations.

First, in hindsight I may have to build a smaller kiln for "shorter" lifts. I'm finding the combining of short length lifts to get close to the capacity of the kiln and fit in the 18' floor space is a challenge. To address this I'm having to cover a portion of the glazing to reduce the temps in the kiln. The first load was only 800bf and the temp reached over 140 degrees most days. It dried from air dry at 16% to an average of 7% in only 8 days, probably too fast?



The kiln operated well, the door opens easily allowing me to place lifts in with my skid loader. The 4 fans keep the air moving well, the dehumidifier pulls moisture out overnight when temps drop below 90, and the vents operate as expected.



My optimistic rather oversize layout dries lumber quickly and efficiently, but perhaps a smaller unit would be just as effective as most of what I saw is under 12' long. I'm going to try placing a thermocouple within a piece of board to see how hot the interior of the board gets, I'm curious if the time at over 140 degrees is enough to sterilize the load.

The load of QS sycamore planed out well, as did the lift of red oak, in the kiln now is maple and the next lift will be 8 and 10 qtr ash.
In my house I'm the boss, I know this because my wife said so, I only hope she doesn't change her mind!

New to me Timber Harvester that I'm learning to operate, been building a home built mill for a while, should be ready to make sawdust with it someday if I ever quit "modifying" the design.

Den Socling

I don't believe you finished your air dried wood too fast.
Get an RTD instead of a thermocouple and you can use any regular wire. Otherwise you have to mess with thermocouple wire.

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