Measurements & numbers
Sail area
How much cloth is in the sail - and the honest basis for what it costs.
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Sail area is the surface of the finished sail, in square metres. For a triangular sail with no roach it is close to ½ × luff × foot, but the moment you add roach or belly, that formula understates it - real area comes from the actual outline.
It matters for two reasons. It drives how much power the sail makes, and it drives what it costs: more cloth, more seams, more hours.
A caution worth knowing: rating rules and brochures often quote a nominal area from the rig triangles (P×E÷2 and I×J÷2), which is not the same as the real cloth area of a roachy full-batten main. When we quote, we are talking about the actual sail.