No pattern? No problem! A hoop made from math.

Today I made the hoop slip, and considering that I did not have a pattern I think it turned out DARN well.  I decided the best way to make the skirt would be to make a pattern piece that, when four were sewn together, would make the circular skirt.

I originally measured out my muslin pattern piece for a hoop that would have a 100 inch circumference at the bottom.  After looking at the hooping of that size, though, I thought it looked too small so I did some more research online.  Turns out that 100 inches seems to have been a standard size for day dresses, dinner dresses, etc, but for a ballgown the hoops were more like 120 to 135 inches.  So I revised my pattern by cutting out another smaller piece that would go between the bigger ones for eight total pieces of fabric sewn into a circle.
 
This is my original measurement/sketch sheet - I had a couple of different ideas.

Muslin laid out on the table to sketch my pattern piece - I measured the length and the width I wanted at top and bottom, then did some math and made guide points so I could draw the angles.

I sewed the eight pattern pieces (four big, four small) together, alternating the large and small.  I decided to make the seams flat felled, and I'm very glad I did.  This needs to be strong, and it REALLY helped with having the inside of the pockets be smooth for the hooping wire.

I then put a big hem in the bottom for the bottom hoop.  For the other hoops, I used my iron to make a crease to follow and sewed a pocket into the skirt.  This seemed easier than making separate pockets to attach, and I was right.

I then cut the hooping to the right length (I missed my guess a bit and the pockets wound up being a couple of inches shorter than I predicted, but that's ok).  And by cut, I really mean "mangle with my small wire cutters until my hands are sore and I sort of break it apart."  Hooping wire is actually two wires set in a balsawood (at least, it looks like balsa) and fabric structure, which is what makes it hold shape so beautifully.

 
The finished product!  The only problem I have is that the top hoop is too close to the waist, so I think it's going to be a very sudden jut out.  If I decide it's too weird, I can take the hoop out and move the loop down.