Passagemaker - Foam Luff

In order to make a smoother roller reefed shape, we apply thin foam in a crescent shape along the luff of the sail. There is more foam in the bottom third of the luff because that's where the sail has more draft.  The extra foam makes the roll slightly wider, which flattens that part of the sail. This way, when the sail is reefed, it is also getting flatter, which helps to depower the sail. When the whole sail is completely rolled up, the sail has a much neater roll. 

Left: Notice the crescent shape of the thin foam piece on the luff; this makes the roll wider at the deepest part of the sail to help flatten the sail as it is reefed. Right: A Tape-Drive Silver sail in the midst of the construction process with a foam luff.