"Capt. Neal®" wrote in message

I'm not sure you understand MY shelf-footed main. It has no elastic
material
comprising the shelf. It has the same 6.9oz Dacron as the rest of the
sail. It
is the shape of the panel that constitutes the shelf foot that gives it
it's shape.

Only when the outhaul is set such that the sail can belly out to the extent
allowed by the shelf foot. Tighten the outhaul, and the shelf foot becomes a
loose 'bag' along the boom.