Building my first solar kiln

[etd66ss]

Hello, brand new member.

I'm looking to build my first solar kiln so I can harvest, mill and dry non-structural lumber (decorative beams, T&G paneling and trim from Scots Pine) for my intended 2022 house build.

I have a brother who owns a circular mill (8" depth of cut) and I'd like to build the kiln without having to buy any lumber. I have about 200 utility poles from an old rail line, and intend to mill 2x8 dimensional floor joists from them (yes, I know all about the carcinogenic creosote chemicals, and we take the required precautions when milling)

I also intended to use the poles to make 1x8 (rough cut) planking for the floor, but the question came up, would the creosote flooring adversely affect the wood that I am drying? Would all the lumber smell like the treated poles? Because that would be undesirable.

My other options for the floor planking would be ash (emerald ash borer killed all of our ash trees here in the northeast, so we have this material in abundance), cottonwood poplar, or my last choice would be spruce, as I prefer to save those trees for other projects, as I only have so many nice spruce trees on site. The question is, would un-treated wood survive the proximity to the ground (no concrete pad or stone) and the humidity from the drying process? I really don't want to buy ~$600 worth of marine plywood for the floor...

I'd like to be able to dry 24ft long beams and boards, so my kiln will be 26ft long.

[etd66ss]

Here is an option for the kiln floor.

1) "Treated" 2x8's for the floor framing



 


2) "Treated" rough cut 1x8's for the sub floor planking


 


3) "Treated" dimensional cut 2x4's on the perimeter


 


4) 1.5" XPS-150 foam for floor insulation


 


5) Ash or Poplar finish floor planking


 

Thoughts?

[Nebraska]

How will you set it? Gravel/cement  footings and block... I wouldn't  go straight on the dirt soil.  I have one on my list as well my plan is to make runners out of poles and put the platform on an old grain bin slab I have and build up from there.  Your floor plan looks workable, how will you load that long? Doors etc. Mine will mirror  the VA tech plans.

[etd66ss]

My plan for setting is:

1) Drill 8 holes with my 3pt 12" post hole auger.

2) Put about 4" of dry ready-mix in the bottom of each hole.

3) Set utility poles in each hole packing around them with dry ready-mix.

4) Use water level to top the poles maybe ~6" off the ground.

5) Build my floor framing off that.

Initially I was going to design to load and unload from the ends, but then decided I want access in the back. So I'll have two hinged doors and two lift off doors on the back, each about 6.25ft wide.  I'll lift the center doors off with my TLB bucket. Not sure I can make them light enough for me to lift off by hand...

[Nebraska]

That sounds ok, not sure about the longevity of the posts set in concrete. Maybe better set on concrete  so they can breathe.
Maybe sackcrete  pads in the bottom for post to sit on, then fill coarse gravel around post. Then cut off with h20 level.

[etd66ss]

That sounds ok, not sure about the longevity of the posts set in concrete. Maybe better set on concrete  so they can breathe.
Maybe sackcrete  pads in the bottom for post to sit on, then fill coarse gravel around post. Then cut off with h20 level.

I'm also considering just using patio stones to set this thing on, because I don't really have a permanent location for it as of yet. It needs to be close to a power source as I don't want to pay what it costs to use solar powered fans, and where I am planning to put it now for ease of access to power could be an eyesore once my house is built...

[doc henderson]

there have been some great builds, here, and guys that use them daily.  you might add to your profile so we know more about your location and age and such.  I assume you are not 88 y/o but I really do not know!    @GeneWengert-WoodDoc was one of the original developers.

[samandothers]

If your poles are creosote or other treatment they will be nasty to mill and the dust is not good on your or your brothers health.  

Nebraska Happy Birthday!

[etd66ss]

If your poles are creosote or other treatment they will be nasty to mill and the dust is not good on your or your brothers health.  

Nebraska Happy Birthday!

We are aware yeah. However they are useful and we take precautions when handling.

Ok, finally got around to updating profile.

[doc henderson]

most of your lumber will have a vapor barrier. and many will use tar to seal it.  so the issue may be if the cut poles will retain the rot resistance.  the newer poles are better in terms of smell.  use what you got and let us know how it goes.  there have been courses on line, and lots of info here and webinars on the NHLA website (you have to register and add name with no spaces).

[scsmith42]

I would not use creosote lumber inside the kiln unless you covered it with some type of vapor barrier.  For floor joists it should be ok.

You will want at least 26' inside dimensions in order to place 24' long lumber inside.  Forking lumber that long into a kiln is challenging, because any corrections made at the steering wheel are magnified at the edges of the lumber stack.

I built some 20 footers a few years back and have hinged doors on them.  I would try to avoid door panels that you have to lift off if possible, but if this is the only choice I would put a 6 footer in the middle and have 10' hinged doors on the sides.

You will need to build an extremely strong header above the doors so that it does not sag.  I built mine by embedding a truss inside of glued and screwed plywood sides.  I have not had any issues with sag thus far.



 

 

[etd66ss]

You will need to build an extremely strong header above the doors so that it does not sag.

Thanks for posting, I was just working on the header in my design. Seems to have turned out similar to your pictures. I was going to do a W-Truss but the vent locations kind of messed up the load pathing.



I am thinking about double hinged doors. The inner doors are hinged to the outer doors. Open the inner doors first, they fold back and latch to the outer doors, then swing out the outer doors. Probably have guide wires with turnbuckles running to the fold back hinge location.

Right now the opening is 25ft, I don't think I want to go any wider. If I do want to load/unload with forks vs. manual, I'll just have to go with ~22.5ft boards instead of ~24.5ft.

[doc henderson]

might consider an overhang across the front to keep water off the doors, and can add guttering so you do not have a mud puddle in front.  you can also change the size and shape of you vents to fit the header, and could even direct them to the soffit of the overhand.  this is what I plan to do.  the soffit frame can be triangulated to add stiffness to the bottom of the header so it does not try to twist on the bottom side.  it will add some weight.

[doc henderson]

as an after thought, if you glue and screw plywood to the header, do you need all of the webbing with 2x?

[etd66ss]

as an after thought, if you glue and screw plywood to the header, do you need all of the webbing with 2x?

There is a trade-off between weight added to the bean from the truss members and what is needed to hold itself up without deflection. It could be overkill, would have to actually do some truss calculations. I've already modified the design from what I posted above but still more thinking I need to do on it. 

[etd66ss]

I'm at 43 deg LAT, should I add 7 deg and go to 50 deg or go with 45 deg?

Trying to maximize the polycarbonate roofing, don't want to have to cut any.

[doc henderson]

most have gone with 45°.  I assume you plan to hit it hard in the summer.  If you are planning to run year round, you could try to optimize for winter when the heat is less, but air is also dry.  I will tell what Dr. Wengert told after my 20th or so detailed question.  "It is only a solar kiln".  If you think to hard about angles, materials, cost ect., you may never build it.  

[doc henderson]

one detail is how to finish the peak so it does not leak and does not get damaged.  if you have an abundance of glaze surface to the load, you may have to cover part if doing a slow wood like oak, and fill it full.  for beams, the large volume to surface area will slow the water loss, and may get very hot if not fully loaded.

[etd66ss]

It seems 55 degrees works out well for the 12ft Tuftex panels.

The glazing collection area is 266 sq-ft.

It's a bit taller than I wanted.



 

 

 

 

I have ~2000 bd-ft of 1x8x24 material shown in the kiln. It seems like from the VT design document they show a 9.5" air gap front and back, that's what I have shown in mine.

Also, why is adding images on these forums such a cluster? And how do I make them so they can be expanded to full size?

[doc henderson]

sounds like it will fastened to the ground.  part of the size of the VT kiln, is so it can be picked up on forks and moved.  you could also make it wider to keep the 45° angle if needed, and it would also be less tall.