Don't forget that the length of the tubes isn't critical, but the distance between bolt holes is.
Use a jig that locates off of the first hole to position for the second hole.
Indeed. Here's a photo of the jig I built the last (first) time I made a dome.
That's the end that the already-drilled hole goes on. The other end, of course, is under the drill bit.
The first time I did this, I was building the dome for myself. Recently, someone asked me, "Where'd you buy that dome?" Upon hearing the answer, he asked what I'd charge to build him one. He has yet to actually come up with the money, but he's indicated that he's game.
Y'all may also enjoy reading about the hoist I constructed from hardware-store materials to make building the dome easier. Domes can be built "top-down" or "bottom-up". Top-down, you hang the dome from a crane or hoist and everybody works on the ground. Each time a level is completed, the dome is raised and construction of the next level is begun. Bottom-up, you start on the ground, and pretty quickly you're moving ladders around to finish the job. Even if you have a man-lift, top-down is faster, because you can have as many people working as you have tools. With bottom-up, you need a ladder or a man-lift for every worker, and there is still the additional hassle of having to lift up the struts, drop tools on people's head, fall off ladders, and so forth.
Here's a photo of the hoist itself, ready for construction of the dome:
And here's a photo of the completed dome with the hoist:
If you're interested,
this blog post describes the logic behind why I think all of this is safe. Lots of load-limit calculations that may interest the engineering geeks aong us.
This blog post details the hardware-store materials that I used to construct the hoist.
..... (I was kind of wondering too:ashamed
