Starting to build the solar kiln

[btulloh]

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)

[btulloh]

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.

[Kbeitz]

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.

[btulloh]

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

[btulloh]

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. 




 

[fishfighter]

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

[btulloh]

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

[btulloh]

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.  ??

[YellowHammer]

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
 

 

[GeneWengert-WoodDoc]

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.

[btulloh]

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.

[fishfighter]

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

[btulloh]

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.   

 

[samandothers]

Better safe than sorry!

[YellowHammer]

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

[xlogger]

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

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

[btulloh]

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.

[fishfighter]

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

[btulloh]

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.

[Ditchdoc]

How long are your roof panels going to be?

[btulloh]

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

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

[fishfighter]

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

[btulloh]

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. 

[fishfighter]

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).

[btulloh]

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.)