So where to begin? I got a lot of inspiration from Adam Savage's Totoro costume for ideas about framing--just less oval and more spherical. After a little trial and error (aka, getting materials online, then realizing they definitely would not work) I found some light irrigation tubing down at my local home depot. I got 100 feet for about $11, so the price was perfect. I had a leftover construction hat from making gargoyles a few years back (I think they're under $10 at home depot again) and started. To make the hoops, I did a little math to figure out the circumference with the largest hoop being 5' in diameter (so about 15' around). To put them together at first I tried just duct tape, but there was always a bend because the tubing is (perfectly for my purposes) meant to be fairly rigid. So I cut a small piece (under 5 inches) and slit it on the curved edge. This piece could be curled in on itself a bit to fit back into either side of the tubes, but rigid enough that it reinforced curve of the tubing. Then lots of duct tape was applied to keep it in place (though it didn't need it that much).
On the fabric/slipcover end of things, I'm planning on dyeing some white muslin gray and using cheesecloth as a window for the wearer to see out of. Still pricing cheesecloth, and watching Joann's coupons for a good time to get muslin.
Apparently my mom had a coat rack! Which I sto...erm...borrowed for boulder costume making purposes. The hat fits perfectly atop it and makes putting on the lower rings much easier. I may need to space out the next couple of hoops further--there needs to be a fairly large viewing window for the wearer to see out of and currently it's more like a very slim slit that allows you to kind of not stumble. *sigh* Stupid practical things like walking and physics are so inconvenient!