Below is a schematic picture of a greenhouse or aviary dome (I
may build both versions). The struts of the dome are color coded
by size, and the covering (aviary wire or plastic sheeting) is blue.
The dome can be scaled to the size desired. Use the scale factors
listed below, and add an inch on each end for the drilled holes.
For a ten foot radius
dome (about 300 square feet of usable floor space), the dimensions
(for 1/2 inch electrical conduit) would be:
-
90 pieces each 4 ft. 3 3/8 in. long
(0.412411 times radius plus 2 inches)
(for the spokes of the hexagons, red in the picture).
-
85 pieces each 4 ft. 2 3/8 in. long
(0.403548 times radius plus 2 inches)
(for the rims of the hexagons, lavender in the picture).
-
80 pieces each 3 ft. 7 3/4 in. long
(0.348615 times radius plus 2 inches)
(for the spokes of the pentagons, green in the picture).
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Electrical conduit is sold in 10 foot lengths, so 127
would be needed, at a cost of $165.10 ($1.30 each). If 3/4
inch conduit were used for greater strength, the cost doubles
to $330.20.
76 bolts, 152 washers, and 76 nuts would be needed to
connect the struts. Each strut has the last inch flattened
and drilled to accept the bolts.
For a 20 foot radius dome (about 1200 square feet of first
floor area, with a ceiling over 25 feet high), 3/4 inch conduit
would be used:
-
90 pieces each 8 ft. 4 7/8 in. long
(0.412411 times radius plus 2 inches)
(for the spokes of the hexagons, red in the picture).
-
85 pieces each 8 ft. 2 3/4 in. long
(0.403548 times radius plus 2 inches)
(for the rims of the hexagons, lavender in the picture).
-
80 pieces each 7 ft. 1 5/8 in. long
(0.348615 times radius plus 2 inches)
(for the spokes of the pentagons, green in the picture).
255 lengths of 10 foot conduit ($663.00) would be needed for the 20 foot
radius dome (the size of a house).
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For a greenhouse, the dome would be covered in clear plastic, such
as 8 mil polyethylene. For an aviary, it would be covered with aviary wire
(also called poultry wire or chicken wire) on all sides, top and bottom,
then roofed with tarp or opaque plastic, and walled (in the winter) with
clear plastic. Aviary wire is about $0.15 per square foot, and 8 mil plastic
is bout $0.02 per sqaure foot. The aviary wire is laced onto the struts
with galvanized steel wire. The plastic is glued to the struts in a shingle
arrangement, with upper sheets overlapping lower for better waterproofing.