I'm still working on copying the seam finish on Mitch's fancy running shirts. I made him another, this one with an entirely new technique.
This time, the seam is serged in the typical fashion (right sides together) so that the seam allowance is on the inside of the garment, then the seam allowance is coverstitched down from the wrong side, allowing the loopers to show on the garment right side. The needle stitching flattens the serged seam on the inside without adding too much bulk. I used matching red thread in the serger and coverstitch needles, and black thread in the coverstitch looper. Mitch likes a decorative stitch on the outside, and that seems to be the way most RTW running shirts are done.
I also hemmed with the coverstitch loopers on the right side. I'm not sure I love that. This fabric is a wicking polyester jersey from Seattle Fabrics. It's nice and light and feels very breathable, but it was the devil to sew. It was slippery and strtechy and generally did not want to behave.
My coverstitch machine particularly disliked it. The feed dogs had a hard time gripping the fabric, so the stitch length was all over the place. She also skipped stitches every time a seam crossed, which you can see at the sleeve/shoulder intersection above. I'm not sure how well this will hold up over time. So far, it is the closest appearing approximation to the RTW shirt, but I'm not sure it will end up being as sturdy, since I had so much trouble getting even stitches. I think I'll take a little break before sewing more of these, to see which finish Mitch likes best over time. In a few months, he'll probably be needing something with long sleeves. That'll be novel!