A sail includes at least three sides, namely two longitudinal sides respectively called “luff” and “leach”, as well as a lower transverse side called “foot” consisting of an assembly of panels having transverse edges parallel to the foot and longitudinal edges parallel to the luff and the leach, each panel being hinged to the adjoining panel around an axis parallel to the foot. Each of the panels includes reinforcing elements distributed into the two following groups: (a) a first group in which they extend parallel and in proximity to said transverse edges, and (b) a second group in which they extend parallel and in proximity to the longitudinal edges of the panel. They are connected two by two by connection parts in the continuation of the reinforcing elements of the second group, so that the forces assumed by the reinforcing elements are transmitted longitudinally from one panel to another.