Cuts & construction
Reef points
Reinforced rows used when shortening a mainsail in heavy air.
DutchRifpuntenour Dutch loft →
SpanishRizosour Spanish loft →
Reef points are the reinforced positions used to make a mainsail smaller. A reef normally has a new tack, a new clew, and a row of small ties or eyes across the sail between them. When the reef is set, the lower part of the sail is gathered along the boom and the working sail begins higher up.
The important loads are at the new tack and new clew. Those corners need proper patches because they take the same sort of load as the original tack and clew. The small ties in the middle are only for bundling loose cloth; they should not be used to haul the sail down hard.
Reefing changes more than area. It lowers the centre of effort, reduces heel, and leaves a flatter, stronger shape for wind that would overpower the full sail.