The side seams are Supplex. I've never heard of it before but it's listed on the Fehr Trade site as being ideal. I made an initial pair with just Supplex in an XS based on my measurements. The Supplex doesn't have as much recovery and it feels more cotton-y than spandex-y if that makes any sense. I switched to an XXS for this pair and it fits more like I think Spandex shorts should fit as it's tighter and the slick material rebounds.
Picking out spandex is much harder than I anticipated. I told one of my non-sewing friends that it's so hard to pick out spandex for booty shorts because the prints are so loud. She said, "Those are words I thought I would never hear you say." I used about 1/2 a yard for this pair. I was very excited thinking about how cheap workout gear was going to end up being until I got to the checkout and the freight charge for 4 yards of material was $19.50! That's more than the price of the fabric per yard.
Now about flatlocking: My Bernina manual lists something called "3 Thread Flatlock" that gives tensions settings for all four threads and "2 Thread Flatlock" that gives tension settings for three threads. I chose the 3 Thread Flatlock option because when I tried to sew with only 3 threads the looper threads kept slipping out. I don't know about anybody else but threading my serger might be my most un-favorite thing ever. Recommended tension settings are: left needle 1-2, right needle 1-2, upper looper 3-5 and lower looper 7-9.
After I sewed right sides together and then pulled the material apart gently to expose the stitching, it looked like this:
I have no idea if that's how it's supposed to look but if it's wrong I suppose I'll find out when my shorts disintegrate. The inside looks like this with a ridge that is flattened against the short. The seam allowance doesn't stick up.
You'll notice little loops sticking out every once in awhile. I think that has something to do with moving the fabric around while I sew. My serger lightbulb burnt out awhile ago. Instead of getting a new one I just sew in the dark. :)
These come together very quickly. I love a good sewing challenge but it's also nice when you can go from un-cut fabric to wearable shorts in the time it takes to watch a baseball game. Speaking of, I've had to resort to carrying my serger into the living room so I can get something done while I watch the Royals play. Anybody else a Royals fan?!
Also, posing in workout wear feels very odd. I decided I wanted to try leaping like they do in sportswear magazines but it looked like this so I quickly opted to stand still.