JK!
I found a couple of sites and liked this best:
http://msucares.com/poultry/reproductions/poultry_make_incubator.html
Construction of a still-air incubator
Small incubators, suitable for use in the home, can be purchased from stores that sell farm equipment. An egg incubator can be built at home with a little work and expense.
The first incubator is constructed from a polystyrene ice chest. It is inexpensive, and because it is insulated, is inexpensive to operate. It can be damaged easily. The eggs and chicks can be observed through a window in the lid. This incubator will hold about 40-45 eggs.
The second incubator is more expensive, but is more permanent. It is constructed of plywood and glass, and will accommodate up to 100 large eggs. Both incubators are heated by a commercially available heating cable. The heating cable can be replaced with two or three ordinary light bulbs. Get a list of organizations that sell incubator supplies and equipment from your county agent or state poultryman.
Polystyrene Incubator
You'll need the following equipment and supplies to construct this incubator.
Polystyrene ice chest (12-16" x 20-24" x 12"-15")
Heating cable
Micro-switch assembly (thermostat)
Glass (approx. 10"x14")
" welded wire - hardware cloth (24"x36")
Cake tin (9"x14"x1 1/2")
Thermometer
Masking tape
Get all equipment and supplies before starting construction. Carefully read and understand the instructions. Expect to spend about 2 hours building the incubator and 4 hours testing it. A description of the construction process, complete with illustrations, is available online.
Plywood Display Incubator
This incubator is more expensive and will take longer to construct than the polystyrene incubator, but it is more durable. It is built of ½-inch exterior or marine grade plywood and glass, and will accommodate up to 100 large chicken eggs. Building plans for this incubator are available online.
1/2"x4'x6' A-C Exterior Plywood
3/8"x3/4"x8' Pine
3/4"x1½"x13' Pine
3/4"x3¼"x4' Pine
1/2"x3/4"x8' Pine
1/2"x18"x27" rigid insulation board
18"x27" heavy duty aluminum foil
1/2"x30" semi-rigid plastic pipe
10"x20" single strength window glass
10"x14" single strength window glass
1½" roundwooden drawer pulls
metal drawer pulls (cup type)
2" hooks with eyes
8' felt weatherstripping 1/4"x1/2"
20"x27" - ¼" hardware cloth
vent covers - sheet metal
incubator electrification kit *
attachment plug
No. 18-2 flexible service cord
duplex outlet for surface mounting
small porcelain knobs for heating element
4"x1" flat hinges
water pan - minimum 360 sq. in.
1/8"x16½' steel rod
3/16"x8' steel rod
Assorted nails and screws
Waterproof wood glue
Both incubators are heated by a commercially available glass-covered heating element. For the plywood incubator, it should provide 160 watts of heat. Slightly less heat is required in the polystyrene incubator.
Although, for the price and lack of self-energy needed in the purchase-over-building ratio, I went and bought two of these:
http://www.tractorsupply.com/webapp/wcs/stores/servlet/ProductDisplay_10551_10001_28385_-1______?rFlag=true&cFlag=1