bay surfer wrote:
Dental floss is high quality dacron thread.
It's my understanding that the standard multifilament waxed ( and unwaxed ) dental floss is nylon not Dacron ( the trade name for DuPont's polyester ). Kites are stitched with sailmaker polyester thread, which is treated with UV stabilizers.
Hand-sewing a lock-stitch like a sewing machine makes with correct upper and lower thread tensions takes some practice. If serious about hand-stitching your kite's leading edge closure seam, get a hand-sewing awl and spare your fingers a bunch of needle jabs.