Once we found a pattern we liked, I adjusted the it a bit so I would only have to buy six 100 yard rolls of fabric as opposed to seven with a lot of leftover fabric. Unless you have a lot of extra money, keep in mind how evenly the fabric gets distributed among 100 yard rolls when you do the design. I made an Excel spreadsheet to estimate the amount of fabric I would need, and it worked quite well. You can download the spreadsheet by clicking here.

I should note that the balloon will use a scoop at the bottom of the envelope instead of the skirt that is shown here.

There are a total of 12 vertical gores making up the envelope. The gores are the up and down strips that you see in the picture. When constructing the balloon, one completely sews each of the gores before sewing one gore to another. Each of these gores are constructed from 13 panels. Each panel is a parallelogram that is 58 inches high, with another inch on the top and bottom for the seam. Below are pictures that show what the panels look like.

Above are the theoretical statistics for balloon. They are necessarily the actual balloon statistics. These numbers were calculated using Bob Nungester's program, available at:

http://www.jps.net/chuck1/empty_pockets.htm

I used output of this program as input to an Excel spreadsheet that calculated the dimensions of each panel. Below I have scanned the output of that spreadsheet. The panels are numbered 1 to 13, with panel one being the bottom panel. The numbers in the left column are the actual dimensions of the panel in inches. Refer to the picture above as to what edge is referenced by what letter. Numbers in right column are just the left column divided by two. I use this when cutting, as I fold the panel in half for the cutting.