It can be tricky to sew a curved hem. If it is and inside curve (like on the side of a shirt with a shirttail hem), when you fold the fabric up there isn’t enough to cover the curve, and for an outside curve (like a circle skirt) you end up with more fabric than the hemline when you fold up the raw edge. So what should you do?
One trick to get around this issue is hem curves with bias tape. Because bias tape is cut on the bias, it can stretch around curves to lie flat. So here’s how you do it.
First, you’ll want single fold bias tape 1/2″ wide or less. Check the hem allowance on your pattern, and trim it down to equal half the width of your bias tape if needed.
For deep curves, you want to steam iron the bias tape into the same curve as the fabric before applying it. Do this by lining up the bias tape with the raw edge of the fabric, and using the tip of the iron to iron just a bit of the tape at a time while ahead of the iron you continue to line the bias tape up with the edge of the fabric.
When you’re finished, the tape will hold a curve that matches the edge of the fabric. Make sure to cut the tape about 1″ longer than the hem you’re going to make.
To hem, unfold and pin the bias tape right sides together with the fabric. At the beginning of the tape fold it up about 1/2″. Overlap this folded edge with the end of the tape. This will make sure raw edges of the bias tape are covered when you’re done. It’s not strictly necessary to do this, as bias tape won’t unravel much even on a raw edge, but I like to do it anyway. Stitch in the crease line closest to the raw edge.
Fold the bias tape to the wrong side of the fabric. Press. Hem stitch along the folded edge of the bias tape.
Voila – curved hem!