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.