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I can't get the list whittled down to where the solar kiln is at the top, so I'm getting starting anyway.  DanG the torpedoes! Full speed ahead!

It seems like some of this has been covered more than once, but I can't find it searching the forum, so I'm gonna ask:

- Is OSB ok to skin inside?  Someone said it won't hold up in the heat, but that didn't seem to be the consensus.  Would CDX work better?

- Same question for flooring.  OSB, CDX? Skin under the joists with CDX or is PT plywood a must?

- I'm planning to do lap siding on the outside and no sheathing, but put tyvek wrap under the siding.  OK?  Not Ok? 

- I'll be using fiberglass bat for both walls and floor insulation.

This thing is going to be 12'x5' inside.  That should be an appropriate size for now.  I'm trying to keep the costs down, but I don't want to compromise the function too much.  Thanks in advance for any input.

BT

The VT design document recommends plywood such as CDX for the flooring, but only specs PT for the floor joists and blocking.  I doubt there would be any difference between OSB and plywood for sheathing at the anticipated temperatures.  I did find a study that compares the strengths of both after prolonged exposure to heat (ie a house fire) and OSB fares slightly better (see here (http://woodscience.oregonstate.edu/sites/woodscience/files/gupta/pdf/56-Sinha-Nairn-Gupta_WST.pdf)).  Figure 4 shows the strength vs temp curve.  Of course the material used in that study may not be the same as you can buy today.  I'd probably go with OSB and make sure to coat it well with the rubberized paint.

I used OSB on the inside, and its working just fine.
I would go wider than 5' though...If your stack is 4' wide i would build it min. 6'wide inside.
Have fun with the build!

Thanks for the reply.  OSB would certainly be cheaper as long as the glue doesn't fail, the plywood probably uses the same glue, so . . .

I may decide to go wider than five feet, because it doesn't add much material and gives me more flexibility.  I use 32" packs mostly, because it works for me and my equipment and I'm low volume.  Wider still sounds better though and gives me some future options. 

Generally I will be drying stuff that's 8'6 or 10'6 so that's where I came up with the 12 foot length for the kiln.  I have a tendency to over-do the while-your-at-it's on my plans, and that can lead me to building something the size of a gymnasium if I'm not careful.  (While I'm at it, why not make it big enough for 16' lumber?  Gosh, 20' might be nice sometime.  Maybe I should go for 1500 bd ft?)  So that's how it goes.  Just trying to keep this smaller for now.

Thanks. And keep 'em coming.

I believe pressure treated cdx was used in the Virginia Tech Kiln Plans. Moisture is not good on OSB over a period of time.

Use CD-x if possible.  No need to use pressure treated sheet goods.  The plastic goes on the inside with the insulation being to the outside of the plastic.  Keeps the moisture inside from getting into the walls.  OSB will work ok but might not last as long.  The bottom of the joists can use hardware cloth to hold the insulation and keep most critters out.  Ventilate under the kiln and then PT plywood or framing is not required.

Thanks Gene.  Good info.

I'll be keeping an eye out for upcoming classes in my neck of the woods.  (Mid-Atlantic)

For some reason i thought we were talking about the inside interior walls.
Thats where i used the OSB.
There is normaly a marking showing the Outside of the sheet, i would keep that side facing in.
As for the exterior walls I used RS pine - 1x8 , if i ever build another solar kiln I would use plywood with good paint.
Have fun with the build!

Definitely talking about the inside walls.  Sounds like cdx is a better choice for inside.  Easier to paint too, although I'm hoping to find a way to spray whatever I put on the inside.  Planning to use SYP lap siding on the exterior.

Btulloh, checking to see what kind of progress you're making? 

https://sbio.vt.edu/for-the-community/extension/solar-kiln/solarKilnWorkshop/index.html

Btulloh, the link above is from a Va Tech site. Seems you may have just missed this year's session.

Looks like I missed it.  The way things are going I might be on time for NEXT May.

The weather this week is perfect for building.  Reality keeps getting in the way.  I need a dose of Kbeitz.  He gets a lot done. 

Here's where things stand:



 (https://forestryforum.com/gallery/albums/userpics/39962/Solar_Kiln_02.jpg?easyrotate_cache=1498658985)

Not quite ready to run a load.   ;)  I hope to get in a couple hours work today cutting parts.  Many other less interesting things to do this week getting in my way.  Looks like the torpedoes are winning.  (How does Kbeitz get stuff done so fast?)

By the way Jim, what is you're eager to get started on?  Get goin' already!  :)

Quote from: btulloh on June 28, 2017, 10:17:09 AM
Looks like I missed it.  The way things are going I might be on time for NEXT May.

The weather this week is perfect for building.  Reality keeps getting in the way.  I need a dose of Kbeitz.  He gets a lot done. 

Here's where things stand:



Not quite ready to run a load.   ;)  I hope to get in a couple hours work today cutting parts.  Many other less interesting things to do this week getting in my way.  Looks like the torpedoes are winning.  (How does Kbeitz get stuff done so fast?)

I'm retired. I guess I have time to do things.
I don't sleep well at night if I don't get done what I have planed to do.
My problem is that I don't get one thing finished before my mind wants to do another.

Quote from: btulloh on June 28, 2017, 10:19:21 AM
By the way Jim, what is you're eager to get started on?  Get goin' already!  :)

Waiting on delivery of my Norwood HD36, they said it would be 4-5 weeks and that was 10 days ago.  So, I wait and I wait... 

I have to build a solar kiln too which is how I found your thread.  But I have to have a sawmill to cut the wood before I can start the build so in the meantime I'm researching.  I have the same problem as you in that I start out to build an outhouse and end up with a bus station.    :D  I want to be able to dry longer woods so I'm going to have to build something that will accommodate at least 12', maybe even 16. 

I have a killer location picked out right beside where I'm going to put the mill.  Don't want to lug that wood around anymore than is absolutely necessary. 

Ahhh. Makes sense, Jim.  Weeks seem like months in that scenario.  That'll be a nice machine when it gets there though.

Knowing what I know now, it would have been a good idea to build the kiln while I was waiting for the mill.  The lumber is not that big a part of the expense, so sawing it yourself isn't necessarily a big savings.  I decided to use store-bought framing lumber so I wouldn't be building a mold generator. Besides, your first lumber will probably get used for a mill shed, unless you've already got that.

I've been sawing a lot of SYP for framing lumber and I found that in the summer I don't stand a chance of keeping the mold away.  I don't really have a good place to sticker it where I can put fans on it, and I'm not sure that would solve the problem anyway.  Now I've accumulated pallets of sawn SYP and I don't want to dead stack it and put it away air dried.  So that being said, I should have built the kiln much earlier.

Another thing I learned is that I would've been way ahead to get more stuff organized before the mill got here.  Of course I had to learn most of that as I bumbled along, so I'm not sure I could have cheated the curve.  One thing I would definitely do though is build some sticker pallets before I ever started sawing lumber.  Handing the output takes a lot of time and effort.  I found out that sawing is about 10% of the overall work involved.  I think I'm one of those people that had to put their hand on the wood stove to find out what hot meant. :-[

Good luck with your mill - when it finally gets there.

Quote from: btulloh on June 28, 2017, 05:44:35 PM
Another thing I learned is that I would've been way ahead to get more stuff organized before the mill got here.

Yes, I've been doing that as well.  Started to build a mill shed but didn't have enough lumber so I did what I could and will do the rest when the mill arrives.   I have about 20 6X8's (12' & 16') that I'm going to frame it with.  Want some beefy rafters should I decide to install a block & tackle.  Not sure I will need one but better safe than sorry, right?

Cut in a road across the mountain today so that I can bring the trees down without actually crossing any of my good roads.   So yeah, been doing what I can to get ready for when my new toy (um, tool) gets here. 

Quote from: btulloh on June 28, 2017, 05:44:35 PM

Knowing what I know now, it would have been a good idea to build the kiln while I was waiting for the mill.  The lumber is not that big a part of the expense, so sawing it yourself isn't necessarily a big savings. 

It is if you use plywood...

Quote from: 50 Acre Jim on June 28, 2017, 03:56:54 PM

Quote from: btulloh on June 28, 2017, 10:19:21 AM

I have to build a solar kiln too which is how I found your thread.  But I have to have a sawmill to cut the wood before I can start the build so in the meantime I'm researching.  I have the same problem as you in that I start out to build an outhouse and end up with a bus station.    :D  I want to be able to dry longer woods so I'm going to have to build something that will accommodate at least 12', maybe even 16. 

Jim, I decided to make it 160" long like the VT design for the same reason.  I am taking a bit off the width, just to be contrary.  Mission creep: 10' should be enough - well might as well make it 12' - now that I think of it, 16' would come in handy - heck why not 40'?

If I need to dry 16' lumber, I'll have to build another kiln.  But first I need to build this one.  Limited progress this week.  I'm lucky to get a couple hours a day to work on it.  I am getting parts cut though.  Had a small generator issue one day that shut me down.  Now my lower back got tweaked and I'm on restricted duty.  I need to bush hog the edges and roads again.  Grass keeps growing.  And so forth...

Thinking . . .

Would it be beneficial to make a hard plenum structure like this?  Bad? Ok but needless? If it's done like this, is there any reason to paint the lower surfaces black?  Use light colored paint to seal the part of the kiln that's not collecting energy? 



 (https://forestryforum.com/gallery/albums/userpics/39962/Solar_Kiln_Plenum.jpg?easyrotate_cache=1499260007)

It is not necessary to do this with the actual collector surfaces.  It does not help to have them parallel to the roof.  What if you are one or two layers of lumber short?  What if the pile shrinks in height as it dries?  You need to fill the gap so that all the air goes through the pile and not have some go over the top.  What if you have a few extra pieces of lumber--adding them to the top would mean no air flow for them.  If you load with a fork lift, this design makes the job very critical.

As you mention, the only black painted items are the surfaces that the sun "sees."

FYI here is a photo of ff member Pineywoods very effective version of the solar kiln.  He will have to fill in the details as I don't recall, I took this pic years ago.

(https://forestryforum.com/gallery/albums/userpics/18520/2969/Marcel_mini_goat_263.JPG?easyrotate_cache=1283939068)

Tough week for building.  Hi temps and humids.  Feels like fishfighter weather here.  I have been getting materials and cutting a lot of parts and this weeks got started with construction.  Slow going, but making progress.  Once I get the north wall stood up it should pick up speed if I get some time to work on it.

I appreciate all the input from everybody.

(Yellowhammer says he calls his the easy-bake oven.  I think I'll hang a couple pork butts in this thing and see how it comes out when I'm not running a load of lumber. ;) )



 (https://forestryforum.com/gallery/albums/userpics/39962/Solar_Kiln_Floor_and_north_wall_1.jpg?easyrotate_cache=1500144431)

hmm pork Butts now we're talkin' . in all seriousness  I'm really looking forward to the build. I need to start mine but a pole barn is on the list first. keep us updated you know where all addicted to F.F. pics!

Btulloh, you have a heck of good start there.  Won't be long till completion. 8)

Looks like longer to completion than I originally expected.  The weather and competing priorities have just about killed progress this week.  I'm getting a few odds and ends  taken care of, but really very little serious work on the kiln.  Not much is going to change on that until Monday or so. 

The hot weather forced me inside and I used some of the time to work on my drawings and some of the details which can eat up time at the finishing stages.  I also laid out a fairly good timeline for the remaining work and was surprised to find out that I'll need 110-120 man hours to finish this thing.  When I started I figured 40 or 50 for the whole job.  So much for optimism.  It's helpful to have a realistic timeline though.  Keeps expectations in line with reality.

(I think my 120 man-hours is about 30 Kbeitz-hours, but I'm just a mere mortal.)

(( The FF hosting server seems to have broken a drive belt tonight.  Lot's of time-outs)

Any thoughts of elastomeric paint (or coating) for the inside of the kiln? 

I know that's a general category so I'm trying to get the specifics on what is available from an interesting new source I found.  Good prices on all kinds of paints and coatings.  I'd rather not use the asphalt type unless I have to.  I can also get aluminum paint at a good price but then I'd need a coat or two of black on top of that.

Quote from: btulloh on July 24, 2017, 05:38:04 PM
Any thoughts of elastomeric paint (or coating) for the inside of the kiln? 

I know that's a general category so I'm trying to get the specifics on what is available from an interesting new source I found.  Good prices on all kinds of paints and coatings.  I'd rather not use the asphalt type unless I have to.  I can also get aluminum paint at a good price but then I'd need a coat or two of black on top of that.

1/4 diesel and 3/4 tar mix. Takes about one week to dry.
Very cheap and it make a good vapor barrier.

That stuff will work for sure K, but I'm just looking at alternatives.

Finally got some work done today.  Raised the walls, but didn't get all the siding completed like I expected.  Now I'm playing with fire with these evening storms we tend to get every day.  It's not in a good state to get a soaking.  I hope to get the rest of siding and the rafters on tomorrow .  Then Thursday morning I can get a coat of primer on the siding.  Primer and a tarp ought to keep me dry enough.  No showers expected tonight or tomorrow night.  Key word: EXPECTED.

Access to the inside is challenging with the doors fixed in position.  It'll probably be a few days before I'm ready to cut them loose from the header and jambs.  I almost left a couple timber screws in place that went through the jambs and into the door frame.  I caught it before I nailed the siding on the west wall.  That would have been a big issue.  Dodged a big one there. 




 (https://forestryforum.com/gallery/albums/userpics/39962/SK_-_Start_west_siding.jpg?easyrotate_cache=1501011426)

Looking good. You even pick out a nice sunny spot for it. :D

I'm getting kiln dried just working on it.  Next time I'm going to build in the shade.

Thinking again - bad habit. 

Using two layers of polycarb, one on the top and and one on the underside of the rafters - wouldn't it be ok, or even better, to NOT paint the rafters black since that is in a separate air space from the inside of the kiln?  Seems like extra heat gain in the space between the two layers of polycarb would not benefit the kiln and would actually be detrimental to the roof structure.  ??

I left mine unfinished for that reason, or more likely, I was lazy.   :D
Seriously, these kilns will get real hot, to the point shown in my other pictures of melting plastic and and scorching wood.  Get them away from any other building you might not want to burn down.  My first clear plastic tops melted away when we had a tornado nearby, and lost power for days.  The kiln was unloaded, so no heat sink, no moisture from the wood to cool things down, the fans weren't running and the upper vents were pretty much closed, so no circulation and all the heat pooled in the upper corners.  Very bad.  I didn't think to check it as I was more interested in other issues.  I melted the roof, it kind of sagged and folded in on itself.  After that, it was very brittle, it just fell apart in a good breeze. 


If it gets rained on during construction, don't worry, it's a kiln, it will dry out :D
 

 

You can buy polycarbonate panels that are already two layers with the two layers perhaps 1/4" apart. These are ideal.  You do not have to worry much about overheating with them.

Overall, two layers of any clear cover are important as they reduce the huge heat loss from one cover.  It makes a 20 F difference in kiln temperature (or larger) to use two.  I made three kilns with one, two and three layers and measured temperatures in 1962 at the US Forest Products Lab.

I looked at those twinwall polycarb panels.  They look like the perfect solution but I haven't found them locally.  With the high shipping cost, it throws the economics out of whack.  If I found a local supplier it would be pretty much a slam dunk.  I'm still looking for a local vendor but so far, no luck.  They're probably around here, but . . .

I have about a week before I have to commit one way or the other, so I'm still looking.

Thanks - as always you have provided valuable information.

Thanks also  to YH for your input as well.  You always supply a good dose of practical reality.  Lazy is a good thing when it comes to painting.  When lazy and correct coincide, it's a good day.  Anything I can do to reduce the amount of time I'm holding a paint brush is a good thing.  I hate painting.  Especially inside an oven.  Even with no roof this is a hot thing to work on even before it gets its black paint.

Some much good info here. Thanks. I will be using all this good info when I build mine. ;D

All the siding is on and primed.  Two days of heavy weather is coming in and I really don't want to get it soaked.  I know YH said it would dry out, but the T1-11 takes up a lot of water and buckles badly, plus I just don't trust that whole drying itself out thing.  An ounce of tarp is worth a pound of drying, as Ben Franklin said.  So I wrapped it.  I'd rather be lazy, but I think discretion is the better part of procrastination.

Two days off for weather followed by some moderate temps.   

 (https://forestryforum.com/gallery/albums/userpics/39962/01019d04a998c371900643f94f6ee5743a825658cd.jpg?easyrotate_cache=1501193734)

Better safe than sorry!

Quote from: samandothers on July 27, 2017, 09:10:53 PM
Better safe than sorry!

Yep.
My kiln exterior is a black painted board and batten style, and over the years, the interior sealing and paint has given up.  So now when I put a green load in, the moisture will permeate the structure and cause the board and batten to noticeably swell some.  Conversely, when a load gets dry, it's easy to tell by merely looking at the outside of the kiln as a I walk by, because I can see clearly visible white lines where the board and batten has shrunk, and exposed the unpainted surface underneath.  So little white stripes, let it cook some more, big white shrinkage stripes, the load is dry.

For example, this load is dry..... ;D.  Easy bake oven.... :D
(https://forestryforum.com/gallery/albums/userpics/21488/IMG_0328~0.JPG?easyrotate_cache=1501213969)

Quote from: YellowHammer on July 28, 2017, 12:08:52 AM

Quote from: samandothers on July 27, 2017, 09:10:53 PM
Better safe than sorry!

Yep.
My kiln exterior is a black painted board and batten style, and over the years, the interior sealing and paint has given up.  So now when I put a green load in, the moisture will permeate the structure and cause the board and batten to noticeably swell some.  Conversely, when a load gets dry, it's easy to tell by merely looking at the outside of the kiln as a I walk by, because I can see clearly visible white lines where the board and batten has shrunk, and exposed the unpainted surface underneath.  So little white stripes, let it cook some more, big white shrinkage stripes, the load is dry.

For example, this load is dry..... ;D.  Easy bake oven.... :D
(https://forestryforum.com/gallery/albums/userpics/21488/IMG_0328~0.JPG?easyrotate_cache=1501213969)

That's a great MM Robert, cheap and easier to use. Now I've got to paint my SK,  ;D

Thanks to a PM from ditchdoc it looks like there's an obscure vendor nearby where I can get the twinwall polycarb.  The name of the vendor is . . . . . HOME DEPOT (free ship to store). Apparently I overlooked them, so thanks ditchdoc.  This twinwall lexan looks to be a much better way to go.  A much simpler install AND it even has warranty against hail damage and yellowing.  Overall price between the twinwall and the corrugated stuff comes out to be roughly equal if you're doing two layers of the corrugated.  Thanks again for that info ditchdoc.

I googled that yesterday and came across HD. Said that they couldn't ship it to the stores around me.

Yeah ff, I don't know how I missed the easy answer.  Good to have someone looking over my shoulder.

YH - that's interesting about the inside losing it's seal.  I was wondering if these materials could stand up to all the thermal and moisture cycling.  That's one of the reasons I was looking into elastomeric paint, but it's still asking a lot for wood and paint to hold up long term.  It may be a good idea to re-coat the inside now and then.  Speaking for myself, I would probably put that off until too late.  I guess it's unreasonable to expect on of these sk's to last as long as the pyramids.  The whole point of the design was to make it affordable and simple to build, and it sounds like it still works even when it starts to lose some it's mojo.

How long are your roof panels going to be?

8ft. with about 6" overhang on the south side. 

Ordered them this morning.  They'll be here in about a week.

You getting them thru HD? Size wide and total cost if you don't mine telling?

4' x 8' x 1/4"  80.07 per each.  So 4 sheets @ 80.07.  Too bad they don't have 2' wide also or I could have save 40.00.  I have to buy 2 feet I don't need.

http://www.homedepot.com/p/LEXAN-Thermoclear-48-in-x-96-in-x-1-4-in-Clear-Multiwall-Polycarbonate-Sheet-PCTW4896-6MMCL/205202473?keyword=1000299065

They are hard to find sometimes on the website even when you know they are there.  Easier through google actually.

They make some doodads for joining, closing the ends and whatnot.  Like a lot things, the accessories seem to be priced high.  At the moment, I think I'm going to seal the seams where the sheets butt together with silicone and seal the top end with silicone.  The bottom end is still open for discussion since it needs to breath and weep. 

Hey thanks. I will use this when I build. I like this about it that came from the Q&A section.

April 6, 2017


Thermoclear Multiwall sheet has a continuous use temp rating @ 100 degrees celsius (212 F) and a softening point of 145 degrees celsius (293 F).

They sell appropriate fasteners with neoprene washers too.  I wasn't able to find them using the HD website, but they showed up when I googled "fasteners for Lexan Thermoclear".  (My brain always sees "Thermoclear" and as "Thermonuclear".  Just another side effect of growing up in the duck-and-cover generation.)

One other useful note on using the Thermonuclear twinwall - There's a good installation sheet for it but it's not linked from HD website. It's good information.  I have the pdf now.  I'll try to find the link again if somebody needs it.

Maybe the extra two feet could be used as the cover on a tanning booth
(you could charge by the 1/4 hour) or maybe just a small chamber to dry fruits and veggies is a better idea.

 :D  The tanning bed is a good idea.  It might attract some interesting clients.

Any client that would come to your solar kiln for tanning would have to be very interesting  :D. 

Any client that comes to your solar kiln for tanning would probably be good sawmill help  :D

 :D :D :D This tanning bed thing is sounding better all the time.

When I was young, I was told that help comes in many forms.  I didn't realize at the time that it was about sawmill help.

Back at it after the rain left and the good weather came in.  Really nice weather.  Now I don't have anything to complain about.

It's still hot working in the sun so I added some temporary shade.  It's worth the time invested.  I'll really need it when I get to puttin' on that black paint. 

I have a delay in getting the north wall done and doors cut loose, so I made a temporary access on the south side.  East and West walls are insulated, moisture barrier added, and skinned.  Tomorrow I should get the north wall and door insulated and skinned. 

I have a couple pair of special home-made gate hinges that were used on a fence gate - a heavy oak double gate.  They should work well for these doors.  I've been looking for a place to use them since I rescued them a few years ago.  Trouble is -- I can't find them. But they're here somewhere.  (Somewhere is big place when you're lookin' for stuff.)



 (https://forestryforum.com/gallery/albums/userpics/39962/Kiln_-_E-W_Walls_Insul_and_Skinned.jpg?easyrotate_cache=1501528707)

Almost ready for the nasty black paint.  I've got a few items to take care of tomorrow (depending . . .) like putting the hinges on and finally getting access through the doors.  Then I can put the top plate back together on the south wall and finish it up.  Friday or Saturday will be black nasty paint day.  Not looking forward to that, but I'm looking forward to it being done.

HD notified me that my Lexan sheets are in.  They got here pretty fast.  Too fast.  I'll pick them up for safekeeping.  I think I trust me more than HD to keep them from getting trashed. 

I'm surprised at how fast they got here.  They were ordered last Friday towards the end of the day, trucked out of Dallas on Monday, and I was notified by HD this afternoon that the order is ready for pickup.  No bad for motor freight.  Almost Amazon-like.  When the order was processed, they said Aug 8-10 delivery. 

 Lexan is tough. It would take a lot to mess it up...

HD may just be up for a challenge like that . . .

I expect they are up to the challenge.  The way the bang up the corners and egdes of plywood is a good indication of their capability.

Siding and interior are completed now.  Ready for some paint inside and out.  I don't care much for painting.  Especially the black roof paint.  I haven't had too many volunteers to handle the painting for me.  Odd.

Also got a few punch-list items done today before the heat ran me off.  Hinges, opened the doors, trimmed the excess tyvek and plastic sticking out here and there.  Not too exciting, but all part of progress.  I haven't picked up the Lexan twinwall sheets from HD yet.  Still hoping it survives unscathed until I get by there. 

Quote from: btulloh on July 31, 2017, 07:53:17 PMTrouble is -- I can't find them. But they're here somewhere.  (Somewhere is big place when you're lookin' for stuff.)



 (https://forestryforum.com/gallery/albums/userpics/39962/Kiln_-_E-W_Walls_Insul_and_Skinned.jpg?easyrotate_cache=1501528707)

This is so true!

Sounds like great progress has been made!

The original VT solar kiln used three coats of flat black latex paint that was rolled on.  Dried so fast, that all coats were put on in one day.

That's interesting Gene.  Latex paint is much easier to use than the asphalt roof paint for sure. 

The pdf on the VT kiln talks about waterproof paints and shows three examples - aluminum roof paint, a rubberized roof paint, and an unnamed commercial kiln paint.   It seems logical to me to try and stop any transmission of moisture into the walls and floor.  I'd rather use the latex paint, but I already bought the pail of asphalt roofing paint.  I am going to use latex on the rafters and fan support board and the cover sheet that goes on the stack.

Quote from: btulloh on August 05, 2017, 09:01:34 AM
That's interesting Gene.  Latex paint is much easier to use than the asphalt roof paint for sure. 

The pdf on the VT kiln talks about waterproof paints and shows three examples - aluminum roof paint, a rubberized roof paint, and an unnamed commercial kiln paint.   It seems logical to me to try and stop any transmission of moisture into the walls and floor.  I'd rather use the latex paint, but I already bought the pail of asphalt roofing paint.  I am going to use latex on the rafters and fan support board and the cover sheet that goes on the stack.

Mix about 1/4 diesel with that asphalt roofing paint and it will go on easy and dry quick.

Thanks Kb, I'll do a test with that.  How about mineral spirits instead?  Seems like that would do a better job of drying than diesel.

Gene, I saw a comment you made on another forum about the vents.  You were saying that the vents never need to be opened much - just a crack, I think you said. 

I'm working out what to do for vent covers and I was wondering how much actual area is required for the venting.  It makes a difference if I only need a way to allow 10% or 20% or x% of each vent for proper venting.  Or 95%.   Thanks for any input.

I've been trying to take advantage of relatively good weather all week, but that's changing tomorrow evening.  We have some weather coming in for about 24 hours, and the rest of the week is supposed to fairly cool, but high humidity and a good chance of storms in the afternoon and evening.

Today I was able to get a bunch of little things out of the way.  A lot of these details don't make dramatic photography but the closer I get to the finish line, the more details take all the time.  Not unlike any other building project.  And I thought I could knock this thing out in a week or 10 days.  Not exactly.  Probably if I had a decent helper, but I'm working mostly by myself.  (Maybe if I made the tanning bed first, I'd attract some quality help.  ;) That idea sounds better all the time, Gene. 8))

Just a few little chores and then comes the painting inside and out.  I'm trying to figure out how all that's going to go with next weeks weather forecast.  This is an odd thing to build, in that you're not weather tight until the very last step when the rafters and lexan go on.




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Regarding the interior black walls, if there is plastic vapor barrier right under the interior wall siding (plywood siding?), then you do not need a waterproof paint. So, flat black latex will work just fine.

Regarding the vents, with some species, like pine or poplar, fast drying is good and is safe, so the vents might be opened 50%. The idea is to drop the humidity with open vents but also trap some of the heat with closed vents.  So, we do not want the vents too wide open, as we will get very little solar heating before the air is exhausteed.  If the vents are closed too much, then the heat will rise but so will the humidity, meaning slow drying.  Slow would be good for oak and similar, and for some thicker material.  It is true that someone who says there kiln reaches really high temperatures when drying is not using the heat to dry wood efficiently.  If the heat were being used to evaporate water, then the temperature will drop and then the humidity will rise, somwe need to vent.  High temperatures are reached when there is little drying occurring.

Aha.  Thanks.  Little by little I'm starting to understand the machine.  I appreciate your feedback.

I have a plastic vapor barrier, plus the paper-backed insulation.  I may as well go ahead and use the roof paint since I have it already.  Next time I can make better decisions.  The roof paint is not hard to work with.  It does not dry fast or completely.  Using the roof paint plus the vapor barrier will be sort of a belt and suspenders approach.  Can't hurt.

The info on the venting is useful, both for construction and for operation.  Since only 50% of the venting area is required, I should be able to use something that fits entirely inside the opening and allow for 0-50% vent opening.  I've seen hinged doors and simple surface mount sliders as well as foundation vent covers.  I seem to be a bit more concerned than some about getting the north wall to take a driving rain.  The vents and the doors don't want to fit into typical weather-proofing techniques.

These discussions have been extremely helpful.  I've heard from other people that they really benefited from going to the class.  By the time a class rolls around again, I'll be in a good position to learn.  Fortunately I have some easy loads to run in this thing to start.

One note that may be useful to someone in the future:  I used the thin T1-11 on the outside of this thing. (I will probably put lap siding over it somewhere down the road.)  I don't think I'd recommend the cheap version of the T1-11 for much other than a dog house.  It's cheap because it's cheap.  There are issues with the laps not being cut correctly during manufacturing, the edges aren't always straight.  Nailing the overlaps tends to split the lap if you're not careful, and even if you are careful.  It just doesn't go on well.

The bigger problem, and the reason I'm concerned about this thing taking weather, is the stuff really takes up water, especially from the ends and the laps which don't seal well.  It swells and buckles across the width from any water.  It's really hard to see it as decent siding.  I am concerned about it holding up well with all the thermal and humidity cycling this kiln will go through.

So the moral of the story is:  Stay away from the 3/8 T1-11 if you can. 

Taking it easy today so I went to pick up the lexan sheets at HD that arrived a few days ago.  Whoever had their money on NO DAMAGE needs to pay up.  The sheets were in a cardboard box and there were a couple good puncture holes in box.  We opened it to check and found this:



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A pretty good hole in one of the sheets.

It turned out ok in the end though.  I'll just lose a part of one sheet, which works out.  (There goes that tanning bed I was supposed to make with the excess.  ;))

They offered me 15% off (the one sheet) which I rejected, and then they offered to credit back one sheet, which was more than fair.  I was holding out for 50% off the one sheet, but who could argue with their offer?

Anyway, all's well that ends well.

In today's world where customer service is usually just something you read about in the history books, I have to give HD credit for doing a good job.  The customer service guy at the store handled the whole thing well and did a good job on the phone with the mothership.   smiley_beertoast  I told him to take the rest of the day off.

Quote from: btulloh on August 05, 2017, 08:02:09 PM
Thanks Kb, I'll do a test with that.  How about mineral spirits instead?  Seems like that would do a better job of drying than diesel.

I would think both work work, but I have only used diesel . I'm thinking the diesel lets it soak into the wood.

Jeez, they could tear up a brick. 
Glad it worked out. 

Thanks for the head up on the thin T1-11. I wonder if one could use steel roofing on the inside and outside. Of course heavy vapor barrier on the inside and outside first. Seal any and all air leaks. Anybody try that?

Another question. Why does the inside walls have to be painted black? The plate under the sun screen, yes black. I don't see as to why the walls need to be black. The sun will not be hitting that.

I think you could skip the black paint where the sun don't shine.  Even with the collector board on top of the stack and the fan mounting board, the sun gets to a lot of the kiln except for directly under the stack.  I think it's easier just to paint the whole thing black.  The other parts should be painted anyway to help keep the moisture away from the wood inside. 

On the T1-11 - That's the 3/8 stuff I'm using, not the regular 5/8.  On the 3/8 stuff, when they cut the lapped edges there's just not much material in the lapped area of each sheet.  It looks the sheets don't always feed correctly either.  Some of the sheets were skewed at one end.  This plays heck with installation.  Not very appealing visually either.  I decided to live with it and work around it, but probably not the best idea.  I ended up caulking all the seams.  Not a big deal.  It's just not quality siding (the 3/8 version).  It'll do.

As for steel, I'd say sure, why not.  As long as the moisture vapor migration is possible from the interior of the wall toward the outside. Could be hard to work with though to achieve the same result.   

Well the weather here today was perfect.  Unusual for August.  85 and low humidity.  Another good day coming tomorrow and then we get some of Magicman's rain and storms for a few days.

Today was another day of details and odds and ends.  No big exciting picture update.  Trimmed a bunch of tyvek and plastic giblets sticking out everywhere. Worked on vents.  Caulked and spot primed.  Painted the door edges and jambs with the black roof paint just to seal them against water.  Tomorrow I can paint for real.  Outside for sure, maybe a coat of the black inside if I can work up that much enthusiasm. 

I do want to get this thing done while it's still good cooking weather.  Originally I thought I'd be done in early July, then by the first of August.  If I can finish by August 15th I'll consider it right on schedule.

Painted, inside and out, one coat.  Went with dark green for the outside.  Picture was taken before the inside was done.  It's rounding the last turn and getting ready to head for the finish line.

Weather and humidity coming in for the next few days.  We'll see what can get done.



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Looks good. Please send me some of that nice weather. I'm swimming down here. :o Had well over 5" of rain the pass week and forcast is nothing but rain every day for another week or so. :o

Wish I had seen this thread earlier. A heads up btulloh, the poly-carbonate panels that the Homeless Deathspot (Home Depot) sells are garbage. They are about 40% thinner than the one Lowes carries, but guess what, they sell them at the exact to the penny same price. You'd never know it by looking at the description on their website.

Of course, I learned this nearly a year ago. Things may have changed, and Lowes may have switched over to the paper thin panels as well...

Hmmmm ... Are you talking about the corrugated panels or the lexan thermonuclear panels?

For the black, I used BLACK JACK 4.75-Gallon Fibered Waterproofer Roof Sealant.  I would recommend it.  It goes on well, dries overnight, and is economical.  I got it at Lowe's but it looks like a lot of places carry it.  I didn't thin it - it seems to be about right as is.

Quote from: btulloh on August 11, 2017, 10:46:01 PM
Hmmmm ... Are you talking about the corrugated panels or the lexan thermonuclear panels?

The corrugated panels..

Hopefully your warning will keep someone from making a mistake, DJ.  Shop carefully.  Caveat emptor.

I'm using the Lexan twinwall panels which are what they are no matter where you might purchase them.  They look to be a better way to get the double layer of glazing instead of using two layers of the corrugated.  Your mileage may vary.

Right now I'm fighting off some weather and humidity courtesy of our friends along the gulf coast.  Not good paint weather.  I'm still planning to get the roof finished by early in the week.  Then I'll be cookin' those pork butts in the new solar cooker.

Well, I set out today to cut the rafters and blocking and put it all up.  And then paint all the rafters and blocking.  But reality happened, and I didn't get to the painting part of that.  Getting all that blocking in is a pain in the neck, the back, and a few other areas.  No need to go to yoga class tonight.  (Or any night.)  Tomorrow I should be able to paint the rest of the stuff black, even though it's going storm on and off.  That temporary roof has really helped out.  Just for the shade alone it was worth the couple hours to put it up.



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Made some major progress in spite of the oppressive weather.  Yesterday I painted all the rafters and put the 2nd coat of black on the interior.  It was not a fun day, but it was good to check off the list.  Today I got the lexan on the roof.  It's getting close to the end zone now.  1st and goal on the five yard line.

Next up: fans and associated structure.  Then a little wiring, make some adjustable vents, put in some door stops, and start cooking. 



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There are some exterior finishing touches to take care of, but they can happen with a load in the kiln.  I want to make an overhang on the front, plus I need to put some steel plates to connect the band joists to the sills.  Then I'll put some of my friendly asphalt paint on the band joists and sills and it should be ready to photograph for the next issue of Better Kilns and Gardens Magazine.

I'll be glad to get this thing finished, not just so I can start drying some lumber, but I'm getting way behind on the general work around here.  Usually everything is dry and brown by August, but we've had enough rain to keep the weeds and grass growing.  It's past time to bush hog.

It's looking good!

If you can still find the bush hog, you haven't put it off too long. ;D

Hey btulloh, that's looking great!

Thanks guys. 

I still need to put the corner boards on too.

Grouch, I like your thinkin'. 

it's looking great and getting me thinking about doing the same... once all my other projects get finished!

Any estimate of how much you spent on materials?

Looks like around $1500 by the time I'm done.  I shaved some costs here and there with the framing lumber and plywood.  Could have saved a more if I had sawed all the framing myself and used my siding instead of T1-11.  I decided to use store bought lumber because it was just time to get it done.  Some things there's just no getting around, unless you're Kbietz, who seems to have a source of free materials for just about everything.  All in all, I'm happy with the outlay and the result.  Still a little ways to go though.  Today was brutally hot and humid, plus I had other things to deal with, so not much progress.

By the Grouch - I found my bush hog.  It was on a tractor, so it wasn't that hard to find.  It's never to hot to bush hog. 

On second thought - yes it is, actually.  But doable.

I put off mowing until it's clear that not mowing will encourage weeds instead of the clovers and grasses that I want. Also, mowing is an activity for that slice of time late in the day just before the sun gets too low to see. :)

Trouble is Grouch, this year is way too wet for August.  Showers though.  Grass and weeds grow, but there's nothing going in the ground.  This is hard on trees.  They do ok with the showers, but get a little dry spell and there's no moisture in the ground for them. 

I just got back from a little bush hogging, trying to nibble away at it.  It's like May instead of August.  Normally I wouldn't have to deal with it until September and that would be good until spring.  Stuff is growing like April, not like August.  August is supposed to be dry and brown and burnt up.  Same with the lawn.  I can't go more than 3 or 4 days without needing to mow again.  It looks nice being all green out there, but I'm going to lose a lot of nice trees with this rain pattern.  Quarter inch every two or three days. 

I haven't checked around, but I bet the second cutting of hay is really good.  Same with the after beans.  The corn looks good too.

Too hot and too many people stopping by today to work on the kiln. 

I just got through debating with myself about mowing the field. (I won the debate, by the way). We've had a dry spell with just a few days of showers for relief. Ponds are down quite a bit. The grass seems almost stalled in growth. It's barely 'woolly' out there, without weeds trying to outrun the grass and clovers, so I'm postponing mowing. Just enough rain to frustrate me from tilling the old garden under and trying some late beans.

My kiln has barely gotten above 100F a few times since I found a remote thermometer + hygrometer to put in it. The first one I tried, in July I think, was only rated for 128F and the temp hit that before noon. The muggy weather we've had here for a couple of weeks has come with only short spells of full sun. The lumber feels drier, but I need to get a meter to measure moisture content.

Just checked a map and you and I appear to be at about the same latitude, just opposite sides of the Appalachians. Which way do your rains come from?

They come from the SE mostly this summer.  After that gulf air dumps on MM and FF it heads up this way.  Sometimes it comes by you on the way here, sometimes it's more of SE movement.  Some of our worst weather comes from classic nor'easters, when a low pressure area moves up along the coast.  It's been an unusual weather pattern this summer.  Funny thing is that every year I think it's an unusual pattern, but different from the previous year.  I'm beginning to think that 'normal' is just a figment of my imagination.  The good thing is that I find a way to complain about the weather no matter what it's like.

That is a great job. I have to build one in the future and really like the glazing panels that you used. I was wondering how much of a gap must be left between the panels for expansion caused by temperature swings and did you have to use big oversize holes for the mounting hardware or did you use something stretchy like silicon glue to mount them. Can't wait to see your first load. Thanks for sharing.  :)

I'm anxious to get that first load in as well.  I worked on the fan mounting stuff today and made some stops for the doors.  I didn't have a lot of time to work on it, but at least I got a little bit done.  Finishing up some the necessary details is a little more time consuming that I thought it would be.  Pretty typical. 

I'm going to run door stops around the inside of the doors and see how well that seals.  It might require some weather stripping or something.  I haven't seen much discussion about that so I'll just work it out as needed.  Fans, door stops, vent covers, then I need the cover to go on the stack and a way to seal around the stack to get the air to go through the stack.  It doesn't sound like much, but takes a little time.  Then I can run a load of SYP and see how it works.  I'm thinking I might need to throw a tarp over the south side to finish up the work inside or else I'll cook myself.

Regarding the lexan panels:  I used the fasteners they make specifically for the panels.  They have a metal washer plus a neoprene washer under that.  Both the washer and the screw is larger than the fasteners we use on metal.  Makes sense.  They have very specific instructions for installation, which I followed (for the most part).  They call for an over-sized hole, but it only amounts to a 1/4" hole for a 3/16 screw.  The hardware they sell for the panels is self-drilling and also has little wings that cut the clearance required.  Works well. In theory it provides enough expansion room.  There are strips that go between panels that have an H profile.  The top is wider than the bottom and they provide a good seal and allow for expansion and contraction.  The strips are a bit pricey, but only three are required and it seemed like a good idea to use them.  I left a little slack between panels, but with these temperatures we're at maximum expansion right now.  I'll see what happens when it gets cold this winter.

I thought about using some silicone around the edges, but after dry-fitting a couple panels and working with the the H-strips I decided to leave out the silicone.  It would have made a mess.  My purlins and rafters are lined up good on top so I have a pretty good seal without the silicone. 

Tomorrow I 'll have some time to get some things done before world ends in darkness at 1:43 pm.

I used a few sheets of black painted roofing tin to cover the stacks, and a plastic tarp for the drop down baffle.  The edges of the roofing tin is slid sideways against the walls to make a decent seal. 
I used a simple 2x4 latch to squeeze the doors shut, but a trailer cam latch is better and pretty easy.  I also basic Lowes weather stripping around the doors to seal against. 
I also have a couple pieces of two inch thick foam board to provide a barrier for the sides of the stack. 

I'm not sure how you will load it, but be very careful about the stickers protruding too much from the inside of the stack of wood. When the stack is being forked in, especially if its maybe a little too much wood and the stack is tall, it's easy to go a little too far and push the stickers against the inside of the roofing.  I've punched a hole in the roof from the inside a couple times.

Robert,

Could you not paint some of the 1" rigid foam panels black and use them instead of the tin to reduce the handling weight?

Useful thoughts from both you guys.  I hadn't thought about using black plastic.  Sounds like a good thing to use, especially to get the first load going.  I can see that all those little details will evolve with usage.  After I get the bicycle built, I'll start learning how to ride it.

The tin would be good, but all my tin is precious to me right now and reserved for covering stacks.  I may switch to tin after I get some more. For now I'm going to use some plywood.  I have odds and ends laying around that I can make 32" x 40ish pieces to lay on top.  Easy to handle and just overlap as needed.  Foam sounds good from a weight standpoint.  It might be something with thermal mass will work better though.  Wood, tin, depleted uranium.  A work in progress.

Cam latches are perfect.  May have to find some.  Maybe Kbeitz will custom make me one like he has.  ;)  He's a busy guy though, so I'm not counting on it.  I'll just rock-and-roll it for now and work it out as I go.  Maybe just lean something heavy against the door.  Who knows?

YH, I plan to fork a load in all at once.  I'm using a FEL with bucket forks to do it, so it's going to be an adventure even if there's no stickers poking out.  Stickers are the least of my worry!  Good thing to keep in mind though.  I use 32" stickers and 32" wide pallets, so I should be ok.  There's plenty of opportunity to cause trouble with the stack though.  I hope I have a spotter around when I load it.  We'll see how it goes.

These finishing details are getting interesting - as in taking too long.  I covered up the panels with a tarp this morning, but it's just not possible to get much work done on it today in the heat. 

Thanks for all the input.  Keeps those cards and letters coming.

BT

May need wide angle mirror mounted inside the kiln to replace the spotter.

Maybe a couple.  Good idea.  Spotters are never around you need 'em.

or are less than helpful :)

A wedge and a hole do the same job as a cam lock. Pick whatever material is handy for each. (Sometimes you make a hole by chasing material out of the way; sometimes you make one by wrapping extra material. Holes be strange animals.)

Roger all that.

Hot weather is beating me down.  Today's forecast is more of the same, but tomorrow the temps go down for the next week or so.  We're even supposed to have some days in high 70's coming up.  That should improve the productivity around here.  I'll get some things done this morning before the heat sets in and look forward to better weather.

Quote from: WDH on August 21, 2017, 07:14:01 AM
Robert,

Could you not paint some of the 1" rigid foam panels black and use them instead of the tin to reduce the handling weight?

I went with the corrugated metal because it had an increased surface area due to the corrugations, and would also let me get conductive heating from both the top and bottom of the metal surface as the air passes over and under it.  In reality, the solar kiln so forgiving I'm not sure I couldn't just drape the black tarp baffle over the top surface of the stack and use it as the collector.  I may give it a try.  Thanks for the idea.

Game called on account of heat at 1:00 pm.  Chipping away at things though.  Got the door stops on.  It's hard to make precision doors and seals with framing lumber, but they're not bad considering.  With the 2x4 frame and the skin on both sides, it's really a torsion box, so it should be pretty stable over time.  Framing the doors and north wall together makes it all line up pretty good.  Even before the weather stripping it seals up pretty good.

I decided to use the basic sliding vent but I put them on the inside.  I think that will work better.  No weather to worry about, and I can put a block of foam insulation on the vent cover if I really want to go that far.

This thing gets pretty small inside when you start mounting the fan stuff.  I had 2x4 supports attached to the rafters, but after sustaining a couple concussions I took them out so I could finish everything else inside first.  Ouch.



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QuoteGame called on account of heat at 1:00 pm.

Now I don't mean to be nitpicky, but it just appears to me you've chosen some design elements for this little structure that might be exacerbating that heat problem. I could be wrong; sure wouldn't be the first time. Some shade, a little more white paint and less black, turn that big picture window northward a bit -- it'd cool right down!

Thanks, I will have to look into the hardware you used for mounting the panels. :)

Good kiln building weather today. Finished making fan boards and mounts. Finished vent tracks and covers.  Cut out stack covers. Primed and painted everything. I should be able to get it all installed over the next couple days. More details than it seemed like. Almost ready to launch.

Done except for fans. I can't find decent box fans. Nothing but junk. Poorly designed plastic blades. They don't move air very well. Claim to be 2500 cfm. No way. Bad blade design performs poorly in restricted spaces.  Been to hd,lowes,walmart,target,office depot,goodwill.  No joy.  A good fan is hard to find. Gave up and cut grass,bush hogged. Broke a shear pin.

I have to find fans.  :-[

Have you tried TSC? I think it was WDH who pointed out some good ones there for moving air over stacks. Might be good in a kiln, too.

may also be a good idea to look at automotive fans. If you have a junkyard nearbye you can get them cheap. I know some automotive fans like ones that came in ford taurus are 2 speed. I have no idea how many CFM they are but they work in tight spaces very well :)

TSC has some good drum fans but they're too big and too many cfm's for this kiln.  Automotive fans would work well, but it's a project.  I have a power supply that would work for them, but it would need to go outside, away from the heat.  It may come down to that.  I hope to find something appropriate tomorrow.  The older box fans work.  A lot of people are using them.  These new ones (which all seem to come from the same factory in China) just don't have well-designed blades.  The other problem is that this is a bad time of year for fans.  Most everyone has sold down to near nothing.  There are some gable vent fans that would work just fine, but with three of them it gets to more $$ than I'd like.  I'm trying to keep the cost down on this thing, which has already been a challenge.  One way or another I'll get some fans in it in the next couple days.

Ok, while you're doing projects...

Put a line shaft in the kiln. Power it outside with a washing machine motor. Inside, have automotive fans (metal blade, pulley, no motor) running from that line shaft. Piece of scrap pipe running in oiled wooden bearings would make a temp line shaft. Belts, pulleys and fans come from the salvage yard.

Good, fast, cheap -- pick any two. :)

These are the ones that I run in my Nyle Dehumidification kiln.  Each fan is 10# in diameter and put out 800 CFM's. 

https://www.carltonbates.com/Axial-Fans/MECHATRONICS/Axial-Fan-115V-AC-125W-850-CFM-254-mm-Dia-x-107-1-mm-D-65-dB-Metal-Housing/UF25HC12-BWHR/p/40026698515-1

Quote from: grouch on August 27, 2017, 08:42:06 PM
Ok, while you're doing projects...

Put a line shaft in the kiln. Power it outside with a washing machine motor. Inside, have automotive fans (metal blade, pulley, no motor) running from that line shaft. Piece of scrap pipe running in oiled wooden bearings would make a temp line shaft. Belts, pulleys and fans come from the salvage yard.

Good, fast, cheap -- pick any two. :)

If I use a line shaft I think it should be water powered.  I know where there's a nice water wheel in PA that FF member has that's just sitting around.  I'll probably have to go visit Kbeitz's junkyard anyway to find the rest of the stuff.  I've got a chunk of lignum vitae that I could make the bearings out of. 

I have a mallet made of lignum vitae. That stuff sure would make good bearing material.

It sure does.  It has natural lubricants as well as durability.  Back in the day, a lot of factories ran on lignum vitae bearings.  The hunk I have came from American Tobacco Co., out of the old Lucky Strike factory here.

Cool and rainy day.  A good day to look for fans, but not a good day for finding fans.  There's a model carried by HD, etc.  that could work, but everyone seems to be out of stock.  It's a 20" high velocity fan, about 6000 cfm on high (claimed).  I'm going to try using just one of them - if I can scratch one up.  The closest HD showed 11 in stock, but none could be found.  Bin #31, front of store.  Empty.  Three guys looked for 20 minutes and couldn't locate them.  There's at least seven HD's here within 15 miles, so I'm going to do some callin'.  All of a sudden I don't trust the inventory control software.

One interesting thing today though, to me at least:  It rained all day - cloudy and cool.  No sun all day.  This was the first day I had the doors closed with the vents shut and the kiln was a good 10 degrees above ambient.  Looking forward to getting a stack of SYP in it as soon as I get the fan thing worked out.  Mostly cloudy through the weekend, so no rush.

Ready to dry a load of lumber as of 12 noon today.  It's raining today and tomorrow, so no pix, and not a good time to load the kiln. 

I still have some punch-list items to complete, but nothing to stop me from loading the kiln and taking it for a test drive.  Weather forecast for the next two days is not solar kiln friendly though.  Sunday and Monday should be mostly sunny but then back into cloudy weather for a few days.

Once I get the load in the kiln I can start cleaning up the punch list.  Some of the final critical-path items (like wiring and installing fan structure and fans) ate up a lot more time than they should have.  The first 90% of the work takes 90% of the time.  The last 10% of the work takes the other 90% of the time. 

Anyway, it's ready to cook now if I can get the load in without destroying too many things.  I know that sealing off the stack and getting the air circulation working right is going to be a learning experience, but I'm looking forward to that.

I'm looking forward to seeing you load it, too.

Did you settle on some fans for it?

I use 2 inch foam board cut into appropriate sized pieces to chink with.  Works great. 

More good info, YH.  You have been very helpful with details.  I can see that getting a decent seal around the stack is essential to proper air flow, but it looks to be as much art as science.  Chinking is an appropriate term.  I think I'll start paying more attention to trimming the ends on boards before I sticker from now on. 

How do you fasten your black plastic to the fan board?  I reckon it needs to be removed to load and unload since it's going to interfere with the already tricky process.  Unless I have a better idea I think I'll just staple it and pull it off when I change out the load.  Not a good long term plan, but ...

Grouch, I ended up using two fans.  One is a 'high velocity floor fan' I got at HD.  Better than the box fans.  I wouldn't want to use it for paragliding.  The other is a fan that a friend brought me a nice fan that was rescued from a small greenhouse.  It's perfect.  16" blades, just a small Dayton motor with blades and cage on the back.  I'll put up some pictures later when the rain quits.  I think the two of them will produce the proper air flow if I get the stack sealed.  I'll used some flow meters, anemometers, smoke streams, piton tubes, differential pressure sensors and turbulence indicators to check out the circulation.  Or at least I'll check around the stack with some tell-tales to confirm air flow.

On another note, I'm enjoying following vfauto's kiln build.  I wish he had gone first because he's doing a great job and I would have gotten some good pointers.  He must be a builder or something because his framing is well thought out and will make it easier at the finishing stages.  One of the problems with jack-leg carpenters like me is in the details.  It's easy to create little puzzles that take extra time to work out later.  I like the way he did his rafter tails for instance.  They will look better and work better when it's all done.

Yes, one of the reasons we switched to palletized lumber system is for the advantageous it offered in the kiln stage.  Easy loading and unloading, easy baffling, straight edges and constant geometry on the wood packs, and easy to calculate and maintain constant board footage per load.  Standardization is very helpful.

For the drop down plastic tarp fan baffle, simply use a wooden nailer strip and attach a plastic tarp to the bottom side of the the wooden fan baffle and create a good seal.  Drill a couple holes in the wood for a bungee cord, and roll the plastic up like a window blind and bungee it up out of the way for loading and unloading.  When the load is in, unhook the bungees and let the tarp drop and roll down to the top of the stack.  The weight of the unrolled plastic will keep the tarp stationary on the wood pack and seal it off.  You'll know you have a decent airflow when the you turn the fans on and the tarp billows out slightly like a sail.  I'm still using the original tarp I installed many years ago.
Shut the doors, crack the vents, and walk away. 

When loading these with a front end loader, approach very straight so you don't have to maneuver when going inside or you will eventually hit the side of the kiln.  I also placed little strips of wood, maybe half inch thick x half inch, around the door frame.  These are my safeties, so when I load the kiln, and I hear them them crack, I've gotten a little too close to the wall.   ::) and I need to stop and look.
Not that has ever happened....
Also, one you get a load in, look for the tire tractor tire marks and just start using then as a guide.  Ideally, next time just follow them in and you should do minimum damage.
Forklift's with side shift make this much easier.....

Someday, I'm going to have enough lumber ahead to use Jim_Rogers' system (https://forestryforum.com/board/index.php/topic,89720.msg1451719.html#msg1451719) of palletized stacking. That looks to be good from mill to air dry to kiln to storage.

Grouch, if you have 9 or 10 boards and you're gonna use them tomorrow, you need a pallet.  You would be surprised how much the pallets improve your life whether you're storing lumber or just moving from the mill to where you're building.  If you sit one next to the saw, you can stack and sticker right off the mill and be done with it.  If you're sawing pine here in VA you can't wait til tomorrow or you'll be growing mold already.  Even if I'm putting up siding green, I sticker the siding on the pallet and then it's easy to move and won't grow the green stuff while I'm looking for my glasses.  It takes an hour to build one, so it's not a big investment in time and it pays that back pretty quick.  I can't remember how Jim's are, but I run three boards across the bottom as well and nail the stickers in place on top.  With the boards on the bottom the thing is almost a torsion box, so it doesn't want to rack or twist.  If I set a loaded pallet down on uneven ground I just stick some wedges here and there to take the load.  (That's for short term only.)

Fans.

I also notice I forgot an important little item:  I need to close off the space between the rafters above the fan mounting boards otherwise I'm going to short-circuit my air flow.



 (https://forestryforum.com/gallery/albums/userpics/39962/Fans_04.jpg?easyrotate_cache=1504386650) 

 (https://forestryforum.com/gallery/albums/userpics/39962/Fans_01.jpg?easyrotate_cache=1504386650) 

 (https://forestryforum.com/gallery/albums/userpics/39962/Fans_02.jpg?easyrotate_cache=1504386648) 

 (https://forestryforum.com/gallery/albums/userpics/39962/Vents_1.jpg?easyrotate_cache=1504386648)

It's looking neat.

Naturally, you'll be losing some 'steampunk' charm by not doing the lineshaft, flat belts and lignum vitae bearings. You could make up for that with some gauges, valves and pipes on the outside. They don't have to do anything.

I am impressed with the fans. They have all the correct features

'Bout time.  Cookin' some wood.  Finally got it finished enough to operate.



 (https://forestryforum.com/gallery/albums/userpics/39962/Kiln_load_1A.jpg?easyrotate_cache=1504480487)

Getting the pallet in went ok, all things considered.  It was kind of like a night carrier landing in rough seas.  With a swarm of yellow jackets in the cockpit.  But no fatalities.  I opted for a small pallet of EWP that was around 19%.  About 300 bf.  It was a good choice to start with an easy one.  My joystick has an interesting personality and it can make life interesting at times.  I need to get the slop out of it one of these days.  All that weight on bucket forks is tricky anyway, even with a light pallet.

The air flow is pretty good and uniform, even with a lot of openings on the sides and under that pallet.  I plan to plug those up, but I ran out of time and enthusiasm today.  Air flow seemed pretty good anyway.  If I tighten up the holes I can probably reduce fan speed or maybe even run on one fan.  We'll see.  125 lfpm is 1.8 mph (if my math is right) so it's not exactly a hurricane coming through the stack when it's right.  I don't know if 1.8 mph will even move a small anemometer, but it felt about right.  I'm still going to plug up the holes in the morning.

The temp got up pretty good considering I closed the doors about 2:30.  I opened a lower vent and stuck my hand in about 6pm and it was pretty warm and moist.  110F coming out of the stack even at 6pm.  I'm not measuring humidity right now, other than feel, but it was pretty humid.  I opened up the vents some more and let the fans run for a while.  When it gets down below 90F I'll cut the fans off.  (I'm just guessing about how to operate this thing, plus what I've read here on FF.)  Riding the bike is different from reading about the bike though.

Don't anybody stress out about my sleepers not lining up with the stickers yet.  It's just 300 bf of EWP at 19%, so it's pretty light.  WE'll get all that done better on the next go round.

It's a good day in kiln-ville and I'm glad to get this thing running, even though I've got some exterior items to finish up.  Thanks for everybody's input up to this stage.  The hard part is just getting under way. 

Now I get to go watch the Hokies play their first game of the season.  I hear they are starting 20 freshmen tonight.  That'll be interesting. 

7:30 ABC

Good job!

Well, except for those misaligned 'sleepers'.
And not getting exact temp readings.
And not getting exact airflow.
And running off to watch a football game instead of turning on some lights and getting that work done.

;D

Hey, I'll be glad to tell you the score when it's done. Game's been on in the garage and now it's in the house while I eat and you're right, it has been interesting!

Quote from: grouch on September 02, 2017, 06:50:33 PM
It's looking neat.

Naturally, you'll be losing some 'steampunk' charm by not doing the lineshaft, flat belts and lignum vitae bearings. You could make up for that with some gauges, valves and pipes on the outside. They don't have to do anything.

Good plan.  I could make it look like something out the old movie "Metropolis".  I have a couple old art deco boiler gauges I could start with:



 (https://forestryforum.com/gallery/albums/userpics/39962/Boiler_Thermo_1.jpg?easyrotate_cache=1504527187)     (https://forestryforum.com/gallery/albums/userpics/39962/Boiler_Thermo_2.jpg?easyrotate_cache=1504527187)

Now that I'm trying to operate this thing, I read back through some of the threads and it cleared up a couple things for me.  Basically more humidity, more vent.  Makes sense.  Now I'm wondering if it would be possible to use a thermostat on the fans.  Is it an absolute temperature where they should be on/off or is it the differential between inside and outside temps?  I can see where some degree of automatic control would be a benefit for me in case I'm not around in the evening.

I believe the fans should run during the day when the sun is shining, and be turned off at night.  A timer may be more valuable than a thermostat. 

First day of all-day drying with full sun.  This thing seems to be working well.  The temp probe that's measuring the air as it comes out the stack was reading 126F.  I had all the vents about half open.

Someone loaned me this nifty little device that is pretty useful.  It measures air speed, temp, RH, wet bulb, dew point, barometric pressure, and altitude. 



 (https://forestryforum.com/gallery/albums/userpics/39962/Anemometer.jpg?easyrotate_cache=1504611688)

I used it to check the air flow through the stack at various points and was able to confirm that the air flow is pretty consistent and the at right desired velocity.  FWIW, the RH of the air coming out of the stack was 36%.  Not sure what that means, but I bet Gene will. 

The temperature of the air coming from the stack was 103f at 8pm.  I let the fans run a little longer, until it got down close to 90f.  Not sure when it's ok to turn the fans off.

Today I have the vents open only about 10%.  Air temp coming out of the stack is 140F and 23% rh.  This morning the lumber was showing 12% mc on average. 

One note on the fans.  Before the sun got involved this morning I was taking checking air flow with the Kestrel to see if it was uniform.  It's fairly uniform throughout the stack, but I tried various combinations of fans and fan speeds to see what effects that had on air flow.  The 16" greenhouse fan seems to be doing all the work.  There was adequate airflow with just the 16" fan (which is the greenhouse fan).  The HD fan didn't really contribute.  With only the HD fan running, at any of the three speeds, there was zero or close to zero airflow.  I don't think it likes static pressure.  Today I have it on low just to help bring air from behind the fan board.  I'm not quite sure what to make of that.  At any rate, the air flow is even, and perhaps a little too fast.  I only took a reading at one spot because I didn't want to open the doors, but it was showing a little over 200 lfpm, which I think I've heard is too much.

Thanks for posting the picture of that Kestrel. I've been wondering what to use for measuring all the variables that need to be juggled.

At 23% RH, that should be sucking moisture out of the lumber. You'll have shrivelled up toothpicks with 0.1% MC in a day or two.  ;D

I've had 80% to >90% RH in my 'kiln' ever since the plastic covering the ridge broke open. No telling how much rain dumped inside during the 6 inch deluge we had that night.

That HD fan sounds like it's all show and no flow.

200 fpm is OK for hardwoods.   600 fpm or more is preferred for softwoods.

Cool rainy day yesterday.  The kiln had the day off.

Today was nice and bright, and it only got up to around 78f.  Nice day.  We have 3 more of those coming, then Irma comes to town.  It'll be somewhat milder by the time it gets here, tropical storm at worst or maybe just some rain.

Today I had the vents open about 10% and the air out of the stack was 140f @23%rh.  I'm hoping someone will tell me what to think about that.  Yesterday the lumber looked to be about 12%mc on average.  I'm thinking today will get it to the finish line.  I opened up the vents to 50% about 5:30.  We're at about 74f 53% rh outside right now.  I'll let the fans run until the temp gets down below 90.  That's been around 9pm the last couple days.  The vents are open more now, so we'll see.

If all goes well, I'll take this load out tomorrow and put in another load of SYP that's been air dried to 20%.  Film at 11:00.

140° 23%RH is an EMC of 4%

Hmmmm. Thanks.  Where do I find this information?

I've still got a little more work to do on the outside of the kiln, but that can wait a few days while I catch up on a lot of things I've neglected around here.  While that's happening, there's another load of SYP in the kiln that should be ready in two or three days.

I'm going to start a new thread on using the kiln.  I'm already starting to find out what I don't know about operating this thing.

Quote from: btulloh on September 08, 2017, 07:18:12 AM
Hmmmm. Thanks.  Where do I find this information?

I want it, too!

I don't see how measuring the RH of air being forced through the stack can tell you the moisture content of the wood. It looks to me like that would be measuring somewhere between the potential for the air to absorb moisture and the amount of moisture available for it to absorb.

Grouch, you are correct.  The EMC value is the moisture level when given enough time, the wood will have reached an equilibrium with its environment and is no longer gaining or losing moisture.  In some species of wood, such as pine which looses moisture very quickly, the wood will rapidly approach EMC, however, in some species, such as white oak, the drop in moisture content is very slow.  However, given enough time, they will all reach it. 

The important thing about Btullohs number is that he has achieved, during a heating cycle, an EMC value which is lower than the actual wood moisture content, so the wood will dry.  Manipulation of the vents will allow this to be controlled to some degree.     

There are calculators and tables on the web for computing the EMC of wood at or below the fiber saturation point (about 30% moisture content) given the temperature and relative humidity.  Here one:  http://www.csgnetwork.com/emctablecalc.html

The difference between the current moisture content of the wood and the EMC value is used to determine, or in the case of conventional kilns, regulate how much moisture the wood will loose in a certain period of time.  These chamber conditions are manipulated in a predetermined "schedule" to safely dry the wood in a fast but safe manner.  I have printed out an EMC table and have copies at each kiln for quick reference.

For example, in an air conditioned house of 70° F and 40% RH, the EMC value will be 7.7%, so given enough time, all the wood in the house will come to equilibrium at that value.  A good way to do a sanity check on a moisture meter is to check wood moisture values in a stable, air conditioned or heated house, especially where the thermostat displays RH and Temp. 

Thanks YellowHammer!

I'm taking this to a new topic:  "Using the new solar kiln"  https://forestryforum.com/board/index.php/topic,97731.0.html

(Grouch, posted a neat way to do these links, but I didn't use it at the time, and now I've forgotten the procedure.  That never happened to me when I was younger. ;D)

I agree that a timer is likely most useful.  But, technically, we would not run the fans unless the kiln is 20 F warmer than outside.

MORE TECHNICAL INFO:  in general, the humidity is the key variable as it allows us to consider how fast wetter wood is drying and how low the final MC will be.

Here is info from another posting about air dried wood going into a solar kiln:
The key for your low MC lumber is the average humidity for the day, not a peak value in the afternoon, etc.

The VT kiln is design to achieve 7% final MC with the vents 95% closed, but with a few leaks.  This will indeed happen.

If the kiln building were perfectly sealed and vents were tightly closed, the MC average would never change...water could not get out.  However, if there were a few wetter pieces, they would loose MC and the drier ones would come up in MC.  In truth, the air would heat and get to 100% RH in the afternoon.  The kiln would then cool as the sun goes down, so we would see the moisture in the air condense on the walls, floor and collector.  Hopefully the liquid can drain out of the kiln.  This cycling would occur everyday.  The average RH would be very high, so we would not see much drying initially, but there would be some if we drain the liquid.

For pine we want no drier than 10% MC.  We know that if the vents were wide open and the fans were run 24/7, then the lowest MC in most of the USA would be 11 to 12% MC.  Lower MC if the fans are not run when the kiln and outside temperature are nearly the same.

So, you need to use a setting between these two extremes...VENTS OPEN PRETTY WIDE FOR PINE, BUT NEARLY CLOSED FOR OAK.

Note that you cannot damage well air dried material no matter what you do.  So we run the kiln to achieve the correct final MC.

Thanks again for the help, Gene.



One note to anyone building one if these: I have to say that the lexan twinwall is a good choice for glazing.  I am amazed by how much of thermal barrier that quarter inch gap provides.  When the kiln was at 140F on the air leaving the stack, I put my hand on the outside of the lexan and it did not even feel warm.  It actually felt cooler than the ambient air.  All in all it seems to be a good solution.  Compared to double layers of the corrugated stuff it's a lot easier to install and about the same price. 

Last phase of construction on the kiln is complete.  I added a little overhang on the front to keep the weather away from the vents and doors.  Just seemed like a good idea.  This kind of slid to the back burner after I had all the operational part complete, but now it's done.  And done.



 (https://forestryforum.com/gallery/albums/userpics/39962/Kiln_Overhang_-_Finished_01.jpg?easyrotate_cache=1507239266)

(It's hard to get good light on the north side of a solar kiln.  Does not photograph well.)

That looks great.  Better than many of the houses in my neighborhood :D

I love it. One day I will have to steel the design :)

Not being critical, but around here, we generally cut a crescent moon shaped vent for every hole. That looks to be a 4-holer at least, so you might have some more cuttin' to do.

It's a fine looking building, for sure.


;D

Grouch, I like that crescent idea for the vents.  It would generate some comments for sure.  Not easy to install though, all things considered.'
'
Crusarius, you should take a look at vfauto's design.  If I was doing it again, I think I'd frame it the way he did his.  It will take more materials than mine did though, but less fiddling involved.  He must be a builder, because his framing looks well thought out without the little issues to solve at the finishing stage.

I am curious to see how he proceeds from this point.  What kind of glazing, etc.  Some of the details with the glazing and fan mounts and creating the plenum got to be quite fiddly for me.  I want to see how he does all that.