Mechanical difference between roller furling and reefing?
The difference between roller furling and roller reefing/furling is primarily in the construction of the sail to prevent excessive draft when reefed. My Norlam genoa (dacron/mylar/dacron sandwich) has a piece of 3/4" thick soft foam incorporated in the luff. It is about 12" wide at midheight, tappering to about 2" at each end. Its purpose is to roll up the center of the sail around a larger diameter thus flattening the sail. There are also patch reenforcements on the leach and foot at selected reefing positions.