Untitled - MetosExpo - Free

The simplicity of the solar-kiln construction is evident in theabove photo. The plywood panel from one end is removed to allowaccess for unloading a dry batch of lumber.Recycling glass for kilnsI use tempered glass for my solar kiln. Ordinary plate glass willwork, but it's not strong enough to withstand snow loads in thenorthern part of the United States. Plastic also lacks strength andwill rapidly succumb to strong winds and deterioration from ultravioletradiation. Fortunately, the wide use of tempered glass panelsin sliding patio doors makes them readily available at a reasonablecost. New ones cost about $80; used ones are a real steal (about$10) if purchased as scrap.Finding old patio doors may require a little effort, because mostglass companies usually dump the old ones. Try talking to thesecompanies about saving the next ones they replace. Glass thermopanes are frequently replaced because of failed (or damaged)seals, which allow moisture to enter the airspace between the twopanels. The resulting condensation etches the glass, forming amilky, translucent precipitate that fogs the panel. Usually only theoutside glass pane, the one on which condensation-occurs, will beaffected; the other pane remains clear. I haven't discovered a wayto completely remove the surface coloration, but it's not a problemfor solar-kiln application. Energy transmission through theglass is virtually unaffected.When you get the salvaged patio doors home, remove the panelsfrom the frame. A thin strip of aluminum between the glass panelsforms an airspace. This in turn is sealed by a rubber gasket betweenthe aluminum strip and each glass panel. A sharp utilityknife works well to slice through the rubber seal. Cut around bothsides of the aluminum strip to fully separate the panels. You don'thave to clean off the seal material that remains stuck to the glass,because it will be helpful in holding the glass in place when youinstall the panels in your kiln.My kiln has single-thickness tempered panels that are 46 in. by76 in. These panels are from the standard 4-ft.-wide patio slidingdoors, but you might also find 3-ft.-wide doors with 34-in. by 76-in.glass. The law now requires that glass be tempered for strengthand safety reasons, so check to make sure older panels are temperedas well. If they are tempered, the words "safety glass" will beetched in one of the corners.Two further words of caution: The process of tempering createslarge internal stress within the glass. As a result, the glass is verysensitive to pressure or shock, which causes it to shatter, just likean automobile windshield. This also is why the glass cannot be cut.So, it's important to base your detailed layout on the actual glasspanel size. Also, when handling the panels, be espeCially careful toavoid knocking the edges.-J W.great assurance that the end product will be free of drying defects.Because a natural balance is established between the drying woodand its environment within the kiln, "overdrying" isn't a problem.Kiln design-My experience with solar kilns includes the constructionand operation of five units in as many years. I alsolearned from previous experimenters. The Forest Products laboratoryhas published a report on a small solar-heated dryer (ReportFPU-7, available from Information Services, U.S. Forest Laboratory,1 Gifford Pinchot Drive, Madison, Wis. 53705-2389). That kiln, likemine, has a simple design and is easily built using readily availableconstruction materials. With a south-facing flat plate attached, ituses an overhead fan to drive the heated air down through thestack of lumber.I also read about other designs using condenser curtains to removemoisture, but I've concentrated on simplifYing kiln design.My structure costs about one-tenth that of a similar-size commercialunit, is built from readily available materials and works aseffectively as the more complex Forest Products Laboratory model.In addition, my design is virtually maintenance free.Construction-Building the kiln is straightforward, and you'll findthe necessary dimensions and details in the drawings on p. 74 andp. 75. Here I'll tell you the procedure I used to build my kiln, aswell as offer some hints to make the job easier for you. Beginconstruction by selecting a location that affords a good southernexposure, unshaded by trees or buildings. Cover the area withgravel and level a 6-ft. by 16-ft. section for the concrete block foundation.Now, cut and assemble the floor frame using the 4x4stringers. Cut dadoes in the end pieces to terminate the stringers.Next, nail ,the plywood floor in place.When building a kiln in a temporary location, I sometimes replacethe concrete blocks with sturdy hardwood pallets and fastenthe floor directly (no stringers) to them using drywall screws. Infact, I use these screws, up to 3 in. in length, to put together theentire kiln. They install easily, hold well and enable me to quicklyand conveniently disassemble the structure to relocate it later on.The kiln is framed with standard 2x4 studs covered with plywood.The south wall and roof support the recycled patio glasspanels you've scrounged up (see the sidebar at left). The kilnshown here uses tl1e most commonly available 46-in. by 76-in.glass panels. Four panels are used for the south wall and anotl1erfour make up the roof. Allow for a %-in. gap between panels.You'll need the spaces later for installing the window stops.Fabricate the back, side and front walls separately, then attachthe plywood siding. InCidentally, don't worry too much about gettingthe joints and seams tight. Air will infiltrate into the kilnthrough cracks in the same way air in your home is replaced periodically.A "leaky" kiln is deSirable, because it improves the aircirculation through the wood stack and results in more efficientmoisture removal.Access to the kiln for loading and unloading wood is accomplishedby Simply removing one of the end walls, so for convenience, use aminimum number of screws to secure this wall in place. For theinfrequent visits to the kiln to monitor drying progress, I've installeda simple, strap-hinged door in one of the end walls. Lastly,note the plate detail at the bottom of the front-wall frame (seefigure 1, detail B on p. 74). The plate extends out Y4 in. to serve asa sill for the glass panels to rest on. Because the plate is exposed,it's a good idea to make it out of pressure-treated wood.Next, you'll need to create a baffle by nailing a partial sheet ofplywood to two of the back-wall studs. The bottom opening of thebaffle will have to be custom-fit to work effectively with your circu-76 Fine Woodworking