A. A spinnaker is any sail set forward of the foremost mast whose width, measured between the midpoints of its luff and leech, is equal to or greater than 75% of its foot length. A headsail is a sail set forward of the foremost mast whose width, measured between the midpoint of its luff and leech, is equal to or less than 75% of its foot length. (See RRS 55.4 and Equipment Rules of Sailing G.1.3 d&f).