Starting to build the solar kiln

[btulloh]

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

[Crusarius]

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

[btulloh]

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

[Crusarius]

or are less than helpful

[grouch]

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.)

[btulloh]

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.

[YellowHammer]

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.

[btulloh]

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.



  

 

[grouch]

Game 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!

[21incher]

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

[btulloh]

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.

[btulloh]

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.  :-[

[grouch]

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.

[Crusarius]

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

[btulloh]

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.

[grouch]

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.

[WDH]

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

[btulloh]

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. 

[grouch]

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

[btulloh]

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.

[btulloh]

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.

[grouch]

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

Did you settle on some fans for it?

[YellowHammer]

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

[btulloh]

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.

[YellowHammer]

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.....