Quote Originally Posted by Pleater View Post
I don't sew the edges of the pleats, as a rule - and the one kilt I have tried that with requires redoing as the pleats roll outwards - perhaps the sewing shortens the edge.
What's happening is uneven tension of the threads through the machine. This can also be achieved when sewing by hand (and better controlled). Sailmakers use this to put curvature into the sails.