The sail acts as an airfoil, producing a large lift force AD at right-angles to the sail and a smaller drag force AC along the sail.
Iseyile isebenza njengesikhuseli moya, isenza amandla amaninzi e-AD kwi-engile yasekunene ukuya kwiseyile kunye norhuqo lwamandlana amancinci kwi-AC ukuya kwiseyile.