The original Hexadome support ring was 90" in diameter and consisted of six segments. I decided to make the dome base ring exactly the same size. Using one of the existing segments as a pattern, I "copied" it with a flush cut router bit until I had enough pieces to make the ring base and most of the ribs. Except for the the two main ribs, they all have the same radius of curvature.
Surprisingly (to me at least), the wood (mainly sheets of 1/8" masonite and 1/2" plywood) was only about a third of the cost. Most of the money went into "little things" like paint, trim, caulking and hardware. You can do most of the work by yourself with a few good tools (primarily a jigsaw and router), but some aspects will require help from others (i.e., tracing out the gores and lifting the dome in place).
I would highly recommend pursuing such a project. The three weeks of hard work will reward you for decades of use.
If you want to know more or would like to have a tour of the new observatory, please e-mail me.