These domes are made out of 1/2" schedule-40 PVC pipe, connected together
with "Magic Hubs".
The gray struts are longer than the blue struts by a factor of 1.13, to make the dome more spherical.
Here's a schematic view. There are 25 of the blue struts and 30 of the longer gray ones.
So for example, to make a dome 30 feet in diameter you'd have:b: length of the blue struts g: length of the gray struts c: curcumference of the dome r: radius / height of the dome d: diameter of the dome g = 1.13 b b = 0.88 g c = 10 g g = c / 10 r = c / 2Pi c = 2Pi r d = r * 2 r = d / 2
Or, if the PVC pipe comes in 20 foot lengths, you could make three gray struts out of each length, giving:d = 30 r = 15 c = 94.2 g = 9.42 b = 8.29
Or if it comes in 10 foot lengths, you could make two gray struts out of each length, giving:g = 6.66 b = 5.87 c = 66.6 r = 10.6 d = 21.2
g = 5 b = 4.4 c = 50 r = 7.96 d = 15.9
You may be able to order Magic Hubs from
Geo Tech Systems.