A three-dimensional sail apparatus that is made up of a plurality of spacedly disposed foils and a sail cloth for attachment to the foils on opposite sides thereof. Each foil has opposed sail cloth supporting sides that together define a foil shape, A support is disposed between the sides for controlling the relative positioning between the sides of the foil, with each rail adapted to deflect under wind force against its related sail cloth so that the foil can assume opposite respective asymmetric foil shapes.