Step 1: Tools and Materials
Make sure you use ratcheting pipe cutters- there's a few hundred cuts to do.
For the hubs
30' 1" Schedule 40 PVC pipe (There will be waste)
130 1' Schedule 40 couplings
26 1/4" x 2" hex head bolts
26 1/4" hex nuts
52 1/4" washers
For the struts
35 Long struts (53 5/16" for an 8' high dome)
30 Short struts (46 7/16" for an 8' high dome)
If you want to make a dome of a different radius or do the calculation yourself, here's the formula (all units need to be in inches). Six inches need to be subtracted from each strut to compensate for the length of the hubs.
For the long struts:
strut length = (dome radius x .61803) - 6
For the short struts
strut length = (dome radius x .54653) - 6
I used Class 200 pipe (thin wall) for the struts. The dome is light, cheaper, packs into a couple of duffel bags for transportation, and is plenty strong to hold up tarps, lights, and a flagpole. If you feel this is not strong enough, you can use Schedule 40. It will just be a lot heavier.
The final cost of the dome, including the tarps used to cover it, ended up around $200. If you shop around for the couplings online, you can save almost $100 from the average home improvement store price. I got all 130 connectors for $53, and the company that I bought them from, http://www.pvcfittingsdirect.com/, offers free shipping on orders over $50.
Step 2: Making Hubs
The use of schedule 40 pipe is important. Class 200 cannot handle the stress of holding the dome together without breaking. Schedule 40 is flexible enough to allow the dome to be built without bending precise angles, but strong enough to keep from breaking.
You need to make:
10 4-way hubs
6 5-way hubs
10 6-way hubs
You will need:
130 4" pieces of 1" schedule 40 PVC
26 1/4" x 2" hex-head bolts
26 1/4 hex nuts
52 1/4 washers
Step 3: Mass Production
The easiest way to do this is with the assembly line method and using jigs to eliminate time consuming measurement.
I made my jigs out of plywood, cut to fit over the PVC to show where to cut without marking. This let me cut all of the hub pieces to length very quickly, and mark the notches without having to think.
As well as cutting, drilling is assisted greatly by a jig. When making the jig, it helps a lot if you come up with a way to make the jig hold the workpiece to avoid error. I settled for an overhang along the back and a steady hand, but I'm sure that there is a better way.
By only doing one type of operation at a time, there is much less set up time and the entire process gets done faster.
Step 4: Cutting the Notches
The notch needs to be cut down the middle of the pipe, to a depth of 2.5 inches. The marking jigs make this a little faster, but expect to spend at least a couple hours cutting.
Dust collection is very important. PVC powder is not very good for your lungs, and there is quite a lot of it. This is one time where a good dust mask or respirator can make this a lot more pleasant. My shop has a dust collection system, so I used that. A shop vac would also work very well.
The blade that you use is also important. I had bad luck using some larger blades, so I used a 1/4" blade with fine teeth. The coarser toothed blades tended to cut too fast and chip the pipe.
Step 5: Flattening the Tabs and Drilling the Holes
Drill the hub pieces about 1/2" in from the end of the tab. This gives it enough strength while still making the hubs fit together right. Use a 5/8" bit to let the 1/4" bolts fit without any effort.
Step 6: Assembling the Hubs
If you don't want to have holes in your covering, make sure the bolts face inwards. I decided to make all of the bolts on the bottom hubs face outwards to attach to grommets on the covering, but it's up to you.
After the hubs are bolted together, attach couplings to all of the tabs.
Step 7: Putting the Frame Together
You will need:
3-4 Friends (the more people, the easier this step is)
10 4-way hubs
6 5-way hubs
10 6 way hubs
35 Long struts
30 Short struts
1 Large open space
There are many ways to begin putting the dome together. The first thing you need is a diagram of assembly. The best one that I've found is at http://www.desertdomes.com (Direct link: http://www.desertdomes.com/graphics/dome/2vdiagram.gif)
Even with the diagram, this step is still tricky. I like to build it from the top down, having a few people lift it up for each level. If you are alone, building it up from the bottom may work, but you will need a ladder. I found that it takes at least three people to set up the dome efficiently.
Step 8: Covering the Dome
The tarps finally fit together with a lot of folding, rolling, and duct tape. We also took off a single strut to make a door.