I was with friends this morning, on board "Monkey Fist", and Frances had her Sailrite machine out making a cover. She had a neat attachment that would fold a 2" webbing over the edge of the cloth, exactly in half, whilst it was being sewn on:
http://www.sailrite.com/Binder-2-Swing-Bracket
Sailrite has developed a new 2-inch binder for canvas and sail workers. Dressing and finishing off edges of enclosures, awnings, dodgers, biminis and sails is made much easier with this high quality 2" binder. This 2 inch Binder automatically guide and fold 2-inch fabric tape or “facing” (made from vinyl, Sunbrella, Dacron, cotton, etc) over a raw edge of another fabric panel during sewing. This binder can also be used to attach flat 2-inch webbing. The resulting sewn edging will be strong and thick enough to securely hold marine fasteners and grommets.
Sailmakers will appreciate the usefulness of this 2 inch binder. Install 2-inch Dacron sail tape on sail edges with ease – reduce time consuming edge hemming. The gate of the binder is wide enough that a leech line can even be fed into the edge tape during sewing.

How neat, I thought. Just perfect for putting a chafe-protecting webbing onto the luff and leech.