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Deluxestogie's Endoskeletal Wood Tobacco Kiln / Flue-cure chamber

deluxestogie

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#1
PART 1 of 4


Endoskeleton. The foam board goes on the outside.

Caveat

The wood-built kiln discussed here has several advantages over using a dead, upright freezer for a kiln, but will require more work to complete, and will certainly cost more.
  • it weighs significantly less
  • it can be sized to whatever dimensions you decide
  • it can be disassembled, if needed, for storage or transport
I believe that Knucklehead's exoskeletal kiln (http://fairtradetobacco.com/threads/5688-Knuckleheads-Wooden-Box-Kiln-Build) is less work to build, though it requires a drilling jig for the corner joins. This endoskeletal kiln requires almost no skill, other than being able to work a hand saw, a hand-held drill, a screwdriver and a pocket knife.

Level of Difficulty

This kiln is not difficult to build, but is quite tedious, because of the many wood members and segments of XPS foam board. The cuts do not have to be all that precise. My choice of assembling the skeleton using deck screws (so that it can be disassembled, if need be) means a lot of drilling of pilot holes, and the placing of numerous long screws.

In contrast to Knucklehead's wood, home-built kiln, which is an exoskeletal wood frame built around an inner container of extruded polystyrene (XPS) foam board, my approach has been to construct a wood frame, with the XPS foam board on the outside of the wood skeleton. My endoskeletal frame weighs 23 pounds, excluding the shelves, XPS foam and casters. It is sturdy enough to easily support my body weight.

My initial idea was to design a simple, modular framework that could be enlarged by adding additional modules, joined to one another by wingnut bolts. That turned out to be impractical, and a needless complication. It was intended to be a marketable, enlargeable kiln kit that could be purchased.

Instead, I settled on a general design that allows a home-builder to decide on a specific set of dimensions (desired size, available space, etc.), and construct it in a similar fashion, from components readily available at most big-box home improvement stores: standard lumber, common deck screws, and Dow-Corning Foamular extruded polystyrene (XPS) insulation foam board.

If you happen to be skilled at cabinetry, then you may find the detailed commentary a bore. If you've never built anything yourself, the lengthy pointers will hopefully convince you that this really is easy to do--but it will take some time to complete. (Allow a week or two of spare-time work, or a day or two of full-time work for those more experienced.) I'm sure that even a novice will discover ways to make this simpler than what I have done.


Digital controller available on Ebay for about $15.00.

The only exotic component is its digital temperature controller, which is available for about $15 from a US-based vendor on Ebay. I have made an effort to use only simple tools to cut and assemble the kiln. The wiring is straightforward, and setting the controller is simpler than using a cell phone.

On deciding my dimensions, I measured the space available for a kiln. Another consideration is the dimensions (width) of your doorways, if you will need to move the assembled kiln from one room to another. My choice of foam insulation board (2" Foamular XPS foam) is based on its high R value (R=10), and its relatively high temperature stability (~170ºF), since I planned to use it as both a kiln and a flue-curing chamber. For the same reason, I selected a high-temperature, silicone door gasket material. If your intended use is only as a kiln, then you may choose to select less expensive foam, and a less expensive gasket material, though the electric cost increases with poorer insulation and sealing.

For the insulation board, I chose Dow-Corning 2" Foamular Extruded Polystyrene (XPS) board, which comes in 4' x 8' sheets. It has an R value of 10, and a temperature rating that will allow the kiln to be used as a flue-cure chamber as well. It's pink! It's expensive.

One of the headaches in determining the dimensions of the various wood members of the skeleton is that, unlike every other product on the market, the stated width and thickness dimensions of lumber are usually, though not always, fictional. The length is its actual length. For so called "hobby boards," the other two dimensions may be actual, though sometimes they are not. With construction lumber (most of the wood offered at Home Depot and Lowe's), the width and thickness are pretend dimensions. So you need to carry a small ruler, and measure it if you care.

This dimensional fantasy becomes a problem when you start with a desired external kiln size, say 30" wide by 26" deep. The 2" Foamular XPS board is actually 2" thick, so the frame would need to be 26" wide by 22" deep. (The kiln height is determined solely by board length, so that's predictable.) I planned on 2" x 2" verticals at the corners of the skeleton. I identified "hobby boards" on the Home Depot website that were stated to be actual 2" x 2". I did not measure them at the store. When I got them home, they were actually 1-1/2" x 1-1/2". My wood kiln frame ends up being 1" smaller in width and depth than I had planned. That's not a big deal, but is annoying.

Materials

[table][tr][td]ITEM[/td][td]QTY[/td][td]PRICE[/td][td]EXT[/td][td]SOURCE[/td][/tr]
[tr][td]110v ºF Digital Temp Controller[/td][td]1[/td][td]$14.99[/td][td]$14.99[/td][td]http://www.ebay.com/itm/281294885235[/td][/tr]
[tr][td]wood cigar box for electrical[/td][td]1[/td][td]free[/td][td]free[/td][td]on hand[/td][/tr]
[tr][td]6' 16/2 Extension Cord[/td][td]1[/td][td]$1.47[/td][td]$1.47[/td][td]Home Depot[/td][/tr]
[tr][td]12' 16/2 Extension Cord[/td][td]1[/td][td]$2.58[/td][td]$2.58[/td][td]Home Depot[/td][/tr]
[tr][td]wire twist connectors 12 pk[/td][td]1[/td][td]$1.97[/td][td]$1.97[/td][td]Home Depot[/td][/tr]
[tr][td]1# box 2-1/2" deck screws[/td][td]1[/td][td]$8.47[/td][td]$8.47[/td][td]Home Depot[/td][/tr]
[tr][td]1# box 3" deck screws[/td][td]1[/td][td]$8.47[/td][td]$8.47[/td][td]Home Depot[/td][/tr]
[tr][td]2" hook & eye 3 pk[/td][td]1[/td][td]$2.24[/td][td]$2.24[/td][td]Home Depot[/td][/tr]
[tr][td]1-1/2" x 48" piano hinge[/td][td]1[/td][td]$10.47[/td][td]$10.47[/td][td]Home Depot[/td][/tr]
[tr][td]4' x 16" wire linen shelf[/td][td]1[/td][td]$8.55[/td][td]$8.55[/td][td]Home Depot[/td][/tr]
[tr][td]4-1/2" door pull[/td][td]1[/td][td]$2.47[/td][td]$2.47[/td][td]Home Depot[/td][/tr]
[tr][td]5-3/4" door pull[/td][td]1[/td][td]$3.57[/td][td]$3.57[/td][td]Home Depot[/td][/tr]
[tr][td]1-1/2" swivel caster[/td][td]2[/td][td]$2.97[/td][td]$5.94[/td][td]Home Depot[/td][/tr]
[tr][td]1-1/2" rigid caster[/td][td]2[/td][td]$2.47[/td][td]$4.94[/td][td]Home Depot[/td][/tr]
[tr][td]3/4" screws to fit casters[/td][td]16[/td][td]free[/td][td]free[/td][td]on hand[/td][/tr]
[tr][td]3/16"x 1-1/4" fender washers[/td][td]50[/td][td]$0.14[/td][td]$7.00[/td][td]Home Depot[/td][/tr]
[tr][td]2" x 165' Tyvek tape[/td][td]1[/td][td]$12.48[/td][td]$12.48[/td][td]Home Depot[/td][/tr]
[tr][td]2" x 2" x 8' pine[/td][td]4[/td][td]$8.38[/td][td]$33.52[/td][td]Home Depot[/td][/tr]
[tr][td]1" x 3" x 8' pine[/td][td]4[/td][td]$7.95[/td][td]$31.80[/td][td]Home Depot[/td][/tr]
[tr][td]2" x 4' x 8' Foamular XPS board[/td][td]2[/td][td]$35.67[/td][td]$71.34[/td][td]Home Depot[/td][/tr]
[tr][td]1/2" x 20' Silicone Door Seal[/td][td]1[/td][td]$16.73[/td][td]$16.73[/td][td]www.homedepot.com[/td][/tr]
[tr][td]1/4" x 30" x 26" plywood[/td][td]1[/td][td]free[/td][td]free[/td][td]Home Depot[/td][/tr]
[tr][td]2 quart Crockpot[/td][td]1[/td][td]$7.00[/td][td]$7.00[/td][td]Walmart[/td][/tr]
[/table]

Tools Required

  • Cross-cut saw or miter saw or table saw (or coping saw or pruning saw--just about any saw)
  • Phillips screw driver
  • power drill or hand drill with various small bits
  • hacksaw
  • small knife
  • eye protection for use with any power tools
  • tiny straight screwdriver for wiring digital controller

Building The Skeleton

Because of the specific dimensions of my kiln, I was able to have Home Depot cut each of the 8' wood boards in half, so they would easily fit in my sedan. This results is very little wood wasted. In this discussion, I refer to the nominal dimensions, even though they are bogus.


Eight foot lumber, cut in half for transport.

Required wood pieces:
  • verticals--2" x 2" x 44" (6)
  • door top and bottom--2" x 2" x 22" (2)
  • sides--1" x 3" x 16" (8)
  • front and back--1" x 3" x 22 (6)
  • knee brace--1" x 3" x 24" (1) cut 45º angles
  • caster braces--1" x 3" x 19" (2)
  • bottom--1/4" x 19" x 23" plywood (1) [measure after bottom XPS foam is fitted]
The 2" x 4' x 8' Foamular XPS sheets (for a kiln of these dimensions) can be cut in half for transport. For a larger excess piece, one of the two 4' x 8' sheets can be cut instead into thirds (48" x 32"). If 4' x 4' won't fit into your car, it's easy enough to bring along a yard stick, a pencil and a pocket knife, to deeply score and snap the XPS to the required sizes, right there in the store parking lot.

Required XPS foam pieces:
  • door--25" x 44" (1)
  • back--29" x 44" (1)
  • sides--19" x 44" (2)
  • top--29" x 25" (1)
  • bottom--25" x 25" (1)
  • optional hinge block--3-1/2" x 44" (1)
  • optional latch block--3-1/2" x 44" (1)
Offsetting the screws


Screws offset at corners. Pilot hole template made from a business card.

Because the verticals are intersected by horizontals on two adjacent surfaces, the two screws for attaching one brace must be offset from the two screws attaching the second brace.

Pre-drilling screw holes

This build consists of a large number of long screws. Although deck screws can often be screwed directly into undrilled wood, it is less work to pre-drill a pilot hole for each screw, and it reduces the chance of splitting the wood.

As Knucklehead reminded me, the first board through which the screw will pass should be bored with a large enough bit for the screw to be pushed through snugly. The second board should be drilled with a bit that is smaller than the diameter of the screw threads. This combination allows the screw to draw the two boards together.

Although a single screw is sufficiently strong for each of the lumber joins, two screws are used for each join, in order to prevent the wood from rotating.

It's easier to pre-drill the screw holes in all the various members prior to starting assembly. After the skeleton is assembled (and now stable), drilling for the shelves and XPS foam attachment can be be done.


Door corner screws. Door knee brace.


Completed door.

The door hinge

Use a hacksaw to cut the piano hinge to a suitable length. For my 44" tall frame, I cut the 48" piano hinge to 39-1/2", in order to avoid the heads of the deck screws at the frame corners.

A piano hinge can be positioned in various orientations. Make sure that your chosen orientation allows the door to open at least 90º, and that the gap remaining between the front frame and the door is appropriate for compressing your chosen door gasket without requiring too much force. The silicone gasket is not only soft, but compresses to a very thin profile. I chose to lay the hinge flat on the exterior, with the hinge joint to the outside, leaving a 1/16" gap between the box frame and the door.

Carefully mark the position of each of the many screw holes for the box side of the hinge, then pre-drill them for the tiny screws that come with the piano hinge. Once the hinge is attached to the box vertical, position the door, mark the screw positions for the door vertical, then pre-drill and attach.


View of hinge.

Latches

I have used three simple, 2" hook and eye latches. These were mounted on the side of the door vertical, and the corresponding side of the box front vertical, with the hooks on the door side and the eyes on the box side.


Latched with three hook and eye closures.

Bob
 
Last edited:

deluxestogie

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#2
PART 2 of 4

Shelves

My chosen dimensions, from pure luck, allowed me to hacksaw the 4' wire shelf into two equal 24" shelves which perfectly fit the available space. The upper shelf is intended solely for hanging leaf below it, so it is positioned 1" below the roof, and is permanent. I drilled holes to accept the crossbars of the shelf on either side, sawed off the nub from the descending front edge, then inserted the shelf into these holes. To do this, I had to back-out two screws that held one of the two wood boards, so that I could rotate it a bit. Then the board was returned to its proper position, and the screws tightened again.


Ends of shelf bars inserted into side top braces. Lower bar sawed flush.

The lower shelf simply sits on the two mid-beams. Since it was possible to jostle the shelf in a way that allowed it to slip off the wood, I added a small screw diagonally into the corner on each side. This prevents the shelf from moving side-to-side, while still allowing it to be lifted off and removed.


A screw at each back corner prevents the removable lower shelf from shifting.

Attaching the XPS Foam Boards

I elected to attach the XPS foam with deck screws. Since the head of the screw can easily pull through the XPS, the force is spread by using a 1-1/4" fender washer on each screw. Figuring out where the screws belong is tricky. I pre-drilled the pilot holes into the bare skeleton, after it had been assembled, making sure that each hole passed completely through the wood. As with the screws for the frame, screws for the XPS along the vertical members may need to be staggered, so they don't intersect.

Once a single XPS panel was positioned, and held in place by hand, I passed a pointed rod through each pilot hole, from the inside out, until the rod poked through the XPS foam. If the rod is properly aligned, then the exterior hole in the XPS foam will allow you to pass a screw (with washer) into the foam hole from the outside, and locate the pilot-hole in the wood. Since I purchased both 2-1/2" and 3" deck screws, I could use the longer ones when screwing into the verticals (and door top and bottom), while using the shorter screws for attaching to the 1" x 3" cross members. It's important that no screw points extend into the interior of the chamber, otherwise Murphy says that you will invariably snag your leaf on them.

At the location of each hook and eye latch, the foam on the box wall was coved, as shown in the photo.


Swing the hooks, to mark the required arc, then cove the foam.


Right side foam in place.

The edges of the foam that may extend beyond the kiln can be carefully shaved off using a thin-bladed, very sharp knife. The edges need to match closely enough to allow them to be sealed using the Tyvek tape. It is possible, with Foamular XPS Foam, to simply score the surface, then snap off a clean line--BUT sometimes the magic works, and sometimes it doesn't.

Attaching the bottom XPS and top XPS are discussed below (The kiln bottom), and should be delayed until the rest of the XPS foam is in place.

Handles
The smaller handle is backed by two fender washers, positioned to align with the mid horizontal brace of the door, then screwed from outside the foam and into the wood, near the latch edge of the door.

Similarly, the larger handle, which will be used for steering the kiln when moving it on its casters, is positioned over the left side "shelf" horizontal brace (the brace below the left top brace). Because it has a wider base, it does not require fender washers. It is screwed from the outside of the foam into the wood.

For both of these handles, use the longest deck screws that will not protrude on the inside. With the handle on the left side, the fixed casters will both be attached to the left side of the bottom (see below), and the swivel casters on the right side.

Optional front corner insulation blocks

With the frame and its hinge and latches interior to the XPS foam, the vertical corners (from top to bottom) beside the hinge and the latches can not have XPS foam extending beyond the front frame of the box. If it did, then there would be no room for the door to swing open at the hinge corner, and the latches would be inaccessible. There is a gasket for the door, but the absence of insulation along these two corners will lead to increased heat loss.

I chose to cut two long pieces of XPS foam to fill those gaps, and hinge them to the box side using Tyvek tape. These will swing away to either side, allowing the door to open. After cutting the blocks (and coving the latch block to allow room for the three hook and eye latches), I placed one of the blocks in position, while taping the long edge on the box side. The block is then swung open and taped again, along the same seam, on the inside. Repeat with the hinge side block. You may need to put a small bevel on the inner corner of the hinge block, to provide room for the hinge bulge. Since these two pieces of XPS will be handled repeatedly while using the kiln, I taped their exterior for reinforcement.


Latch XPS foam block attached.

My simple solution for holding these two corner blocks of XPS snugly against the kiln when the door is closed was to use rubber bands. A 3" deck screw is anchored to the wood beneath, and is not fully screwed-in, leaving about 1/4" of the head exposed. One is placed from the side, beside the tape-hinge. A matching screw is placed from the front, into the door frame.


Two rubber band closures on each corner foam block hold them snug.

I use two rubber band closures on each corner XPS block. The rubber bands can be tied with a larks head knot onto the side screws, so they can't fall off while the door is open. I originally considered a more elegant Velcro closure, but this solution seemed reasonable and easy.


Larks head knot.

Bob
 

deluxestogie

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#3
PART 3 of 4

The kiln bottom

I chose to complete the bottom before attaching the XPS foam to the top. The 1" x 3" x 19" caster braces are screwed to the bottom of each kiln side. They should be flush with the outside of the side frame, and extend their width onto the front and back frame.


Caster braces. Be sure to countersink any screw beneath a caster attachment.

The two fixed casters are mounted on the ends of the left caster brace (the side with the large handle), and should be oriented so that the kiln can be tipped sideways with the handle and pulled or pushed. The two swivel casters go on the ends of the right caster brace. I screwed each caster using three 3/4" long screws, and managed to find at least one of the four mounting holes in a position that would allow the placement of a longer screw (without colliding with the framing screws).


The two fixed casters (on the left side) allow the kiln to roll sideways.

The XPS foam bottom will need to be marked for the location of the 1" x 3" caster braces, and for the 4 cutouts (where the casters are attached). The foam will be partially inset between the two caster braces, and rest firmly on the kiln frame. The cutouts for the caster braces should not be through and through, but only to a depth of 3/4" (the thickness of the caster brace). It is tricky, using a slender, sharp kitchen knife, but it doesn't have to be beautiful.


Floor foam carved inset for the caster brace and cutouts for casters.


Floor foam fitted over caster braces.

The left (handle) side of the foam should be beveled from the fixed caster axel to the edge of the kiln. [This bevel is also continued on the XPS side panel, so the kiln can be tipped to the left, without the foam dragging on the floor.]


Foam bevel of floor to allow the kiln to be tipped onto the fixed casters.

Once the foam is loosely fitted into place, cut a wide bevel around each swivel caster, to allow them to fully swivel.


Wide bevels for swivel casters (right side of kiln).

After the foam has been beveled on the left, and the swivel caster bevels are done, the dimensions of the 1/4" plywood floor (on the exterior of the foam) can be measured, along with the required caster cutouts. It is bored and screwed into the kiln frame, without fender washers.


The 1/4" plywood floor. The left side is shortened by the bevel of the floor foam.


The completed floor.


The bottom of the left side panel is beveled to match the floor bevel on the left.

Bob
 
Last edited:

deluxestogie

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#4
PART 4 of 4

Circuit Box


Whittling the square hole for the controller.

You can purchase a common electrical circuit box in which to mount the digital controller and hold the wire splices. I used a wood cigar box that was on hand. The Spanish cedar of the box is soft, with a straight grain, so I just marked the dimensions of the hole for the controller, then whittled the square hole for it with a pocket knife. [For a common circuit box, drill a small hole at each of the corners on the cutout, then saw the square hole with a jeweler's saw.]


Digital controller fitted into the circuit box.

My extension cords were flat, rather than round in cross-section, so I whittled 3 flat holes (one for incoming power, two for switched and unswitched output). The box also required a small round hole through which to pass the temperature probe. The controller comes with two plastic brackets which will tighten the controller in place in the box. In my cigar box, the whittled hole was so snug that I did not use the brackets.


Whittled slots for wire passage.

Wiring the Digital Controller

The specified digital controller has only 6 terminals in the back, which are accessed by removing the angled plastic piece from the back. These are clearly labeled on the accompanying instructions. Two are for attaching the temp probe wires. Two are for incoming 110v AC that powers the controller itself. The remaining two are for a single wire that will be switched on or off by passing through the controller's temp-controlled relay.

For incoming power, I use the plug (male) and most of the length of the longer extension cord. The switched circuit can be AD or DC, and just about any reasonable home voltage. In my case, it will go to a 110v outlet (female end of the short extension cord) to power a 110v Crockpot, so I use the same incoming power to connect to the controller's power as well as the switched power. While I was at it, I included another female end of an extension cord (the remainder of the long cord) to make unswitched power also available to the kiln, for any 110v gadget added at a later date.


Wired circuit box.

The cut wires of all the extension cords (discarding the "plug" end of the short one) are separated and a short length of insulation stripped from each. They will be joined using electrical twist caps. I find looking at spliced wiring always confusing.

For 2-strand AC in the US, the wider blade of the two plug blades indicates the neutral conductor. If you look carefully at a simple lamp cord (which is what these 16/2 extension cords are), you will notice that the insulation of one of the conductors bears fine ridges for its entire length. This is the neutral. In order to maintain the polarity of the wiring (so that the neutral is always the neutral), these neutral conductors should be matched during splicing. That way, the wider blade coming from the electrical wall outlet will match the wider blade on your output power. It's easy to do, if you pay attention to it. With round, 3-conductor extension cords, the neutral is usually white.


The insulation of the neutral conductor has fine ridges.

The controller itself has no exterior metal, and has no terminal for accepting a grounding wire (the green wire in a 3-conductor extension cord). Which of the controller's power terminals gets the hot and which gets the neutral does not matter. If you use 3-conductor extension cords, just pass the green on to the output cords, bypassing the controller.

Temperature Probe wires:
  • one of the wires to terminal ["5"]
  • the other wire to terminal ["6"]
Hot spliced together with twist cap:
  • incoming extension cord hot
  • to controller power terminal [marked "4"]
  • to controller relay (switch) terminal [marked "2"]
  • to unswitched output extension cord hot
Neutral spliced together with twist cap:
  • incoming extension cord neutral (with the fine ridges, wider plug blade)
  • to controller power terminal [marked "3"]
  • to switched output extension cord neutral
  • to unswitched output extension cord neutral
    The hot conductor of the switched output extension cord is connected to controller relay (switch) terminal[marked "1"]

Essentially, the neutral and hot just go to the controller's power and to each of the output extension cords, except that the hot for the switched output extension cord passes through the relay [terminals "1" and "2"] along its way, and is switched by the temperature controller.

In making the connections to the controller, it should be pulled out of the circuit box, and the wires passed through its square hole. A Nylon zip tie can then be tightened on each of the wires, just inside the circuit box wall, to prevent the cords from pulling out. Now the controller and its attached wires are inserted back into its square hole, the wires compressed in a tidy way, and the circuit box closed. If you will be attaching the circuit box to the kiln using screws through the wall of the circuit box, you may need to temporarily slide the controller out of its square hole again to do this, once the kiln's XPS foam walls are in place.

Passing a power cord through the kiln wall

The Crockpot, inside the kiln, will need to pass its power cord through the XPS foam wall to reach the switched outlet from my circuit box. In the future, I may want to add a fan, which will also require wires to pass through the XPS foam wall. A simple, adjustable way to do this is to cut a square hole in the XPS foam. The hole needs to be large enough for the Crockpot plug to pass. Either the piece of foam that is removed, or a newly cut piece will serve as a stopper for the large hole. It is then provided with a notch the size of the cord only. It is fitted with a Tyvek tape "handle". Once the cord is passed, the stopper is snugly inserted, and can be taped if needed to form a seal. To add a second wire, the stopper is removed, a notch added, and the stopper replaced after passing the wire.


Passage for Crockpot power cord.


Stopper in place inside and outside. It should be taped.

Positioning the temp probe

This controller comes with a 9' wire for the temp probe. I poked a hold just large enough to pass the probe into the middle of the top foam of the kiln. It is extended about 4" into the kiln. The hole is then taped from the inside and outside. The course of the wire outside the kiln is taped, to prevent it from being accidentally snagged. Rather than shorten the probe wire, I simply bundled it near the circuit box.


Temp probe inside. Probe wire outside.

Extra, hanging basket

About 4 years ago, I purchased two wire baskets (all metal, with no plastic) from Walmart, found in the section with doo-dads to hang in the shower. One of them has served as the main tobacco holder in my baby kiln. For this new kiln, I added two 'S' hooks to its handle, so that it can be suspended beneath the lower, removable shelf, above the Crockpot--a frequently wasted space that is not tall enough for hanging leaf. It will tilt for loading and emptying, and is suitable for pressed leaf or leaf within gallon Ziplock bags.

Taping the seams

Unlike Knucklehead's exoskeletal kiln, in which he simply applied Tyvek tape to the internal foam junctions, the internal framing of my endoskeletal kiln obscures those junctions. So, I taped every intersection of the framing with the foam. This is a tedious task, but will minimize heat and humidity loss from the kiln. Also, since the 4' x 8' XPS boards come "pre-scored" for building construction use, I taped over any of these factory scores where they appeared to be vulnerable. I did all of the internal taping prior to attaching the XPS foam roof, in order to have better lighting inside.


I used nearly all 165' of the Tyvek tape. Very sticky stuff!

The fixed location of the upper wire shelf prevents taping of the roof foam on the inside of the kiln. External taping has to suffice.

Silicone door gasket

I positioned the self-adhesive silicone door gasket as near to the inside edge of the door closure as possible. It is cut to 45º at each corner. One of the gasket's edges is thinner than the other. I attached it so that the fatter edge is toward the interior of the door opening.


Silicone door gasket.

Initial empty run

With the empty two quart Crockpot in place (resting on scrap 3/4" planks), I set it to low, set the controller to a max temp of 125ºF, and a drop of 5ºF before turning on again, and plugged it in. From room temp, the kiln required 4 hours to reach 125ºF. Thereafter, it cycled for about 30 minutes on and 30 minutes off, as the kiln temp swung between 125ºF and 119ºF.


The completed endoskeletal kiln.

The tip of my pinky finger could sense warmth at the top corners of the door. I will add some tape in that location, then see how that affects it.

Running half the time is not bad, considering that the Crockpot is set to low, and this is a fairly large kiln. The Crockpot is rated at 100 watts, which is the power utilization when set to high. I'm guessing that the low setting is about 75 watts. So, running half the time, the power use is less than a continuous 40 watt bulb.

Another factor is the humidity. Humid air holds more heat than dry air, so I expect that with humidity added, the on-off cycle will slow further.

I don't intend to measure the humidity--ever. With leaf in the kiln, I will determine the maximum amount of water that can be placed in the Crockpot, without producing condensation. The water will be replaced whenever it runs dry (an interval yet to be determined).


13 cubic feet of kiln space.

Bob
 

Rickey60

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#6
I think you have built a nice kiln/flue-cure chamber. You put a Lott of thought into it. Great design and low cost for such a well built unit. I know it will work very well. I nice unit for others to copy. I am looking forward to seeing it in action. Thanks for posting your design.
 

Knucklehead

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Excellent kiln build and (as usual) instructions. I love the cigar box for the controller. It adds a perfect tobacco touch.
 

Bex

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#14
Hmmm....a definite step up from the Cozy Can. I must say that, for the inexperienced and uninformed, the trashcan is close to my heart - so easily doable, that even I didn't find it too involved. Your instructions for this new 'endoskeletal' (what a hoot!!) kiln are great, although I did get lost halfway through, and have to concentrate more than my furry little brain is accustomed to. But these are great step by step instructions, and I can't wait to see this in action. What interests me most, other how much you actually weigh (considering this kiln would support your weight, but would it support mine??), is that you will never measure humidity EVER. But that information may be the subject of a different thread.....I will miss my occasional visit to the Cozy Can thread, however. I'm going back to read this thread again now......
 

deluxestogie

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#15
About the humidity:
If water evaporates from the Crockpot, the leaf goes into case. When the water is gone, it will go out of case. So long as I avoid condensation and drips, I don't care how high the case becomes. So long as I add water to the Crockpot not too long after it runs dry (trial and error to determine the interval), any dry leaf will promptly go back into case, and little kilning time is wasted on dry (inert) leaf.

I seem to recall that 118ºF is the temp at which mold can no longer experience vegetative growth, so mold is not an issue.

I have to say that I'm delighted that the 2 quart Crockpot is sufficient to run a kiln of this capacity. I may need more watts to flue-cure, but I'll deal with that when the time comes.

At present it is cycling at about 20 minutes on and 40 minutes off.

One issue that I haven't addressed is a vent, which will be required for flue-curing. My current thinking is to make an improvised ballcock embedded into the foam of the roof.



Bob
 

Bex

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#16
Ah, so you're talking about kilning rather than flue curing (I never got around to trying to kiln this year). The vent is a good idea, and can be made even better with the humidity controller equivalent of the temperature controller that you have on the EWTK (easier to type). If you can build your vent to open and close electrically (I think Amax has something like this), the humidity controller will open and close it according to the RH. Pretty neat. Presumably when you are using your set up for flue curing, you will then be paying attention to humidity?? Or still no?
 

deluxestogie

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#17
... when you are using your set up for flue curing, you will then be paying attention to humidity?? Or still no?
With the Cozy Can, I maintained humidity during yellowing, though I never measured it. I slowly decreased the venting up through leaf drying, then fully closed it for stem kill. So, it was basically seat of the pants flue-curing.

Since it's alright to peek (open the chamber) during the yellowing stage, which is really the only time I need to see what's happening, I decided that the fuss of installing a window would also be a questionable investment.

Bob
 

deluxestogie

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#18
I'm pleased with how little outgassing came from the kiln construction materials (specifically, the XPS foam and the Tyvek tape adhesive). So, to celebrate, I took down some of the hanging leaf from my enclosed back porch--the leaf that was hanging in the way of where I wanted to position the new Endo Kiln. It wasn't in as high a case as I would prefer for close packing, so I went with about 2/3 of a full load--some on wire strings, some in tied hands, and a pound of leaf in a gallon Ziplock for the basket--and deposited it in the Endo Kiln.



For starters, I've put 2 cups of water into the 2 quart Crockpot, set it on low, and left off the lid. I'll have a look in two days.

Bob
 
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