The principle of our food dryer is simple: Hot air — which rises through the container from a heat source below — is baffled around and over trays that hold the produce. These racks are 5 inches shorter than the depth of the cabinet and are placed alternately against its front and back to force the warmed air to circulate through the entire box.
The dryer is fairly inexpensive and easy to build. Start by constructing the two side frames out of straight, clear-grained 2 by 2's, as shown in drawing. The upper 38 inch section of each unit is then covered with 1/2 inch plywood on the outside and with 1/2 inch insulation board on the interior. The slides for the trays (1 inch by 1 inch by 29 1/2 inches) are nailed across the inside of each face from the front edge to within 1/2 inch of the rear edge (the gap at the rear leaves space for a sheet of 1/2 inch insulation board inside the back).
The sheet of insulation, 15 inch by 38 inch, is tacked to the ends of the tray slides as the first step in the dryer's assembly. Next the top piece and cross brace are attached to the front posts, and boards are nailed on or attached with screws to form the back. The top is then installed, leaving a 3 inch vent as shown in drawing. Insulation for the top is applied in two sections and nailed on from the inside.