Abstract: This invention relates to an adjustable airfoil which in one embodiment includes a pivotal mast having laterally extending spaced upper and lower arms. Between the arms is a vane which is rotatably mounted on the mast and has a luff slot at its aft end for receiving the forward end of spaced battens connected to flexible sail panels. The panels are provided with inserts at their forward ends sewed in such a manner as to cause the panels to fold in accordion fashion when they are lowered. The sail is raised and lowered by a halyard which may be either in the form of an endless loop mounted adjacent a positioning cable extending between the aft ends of the arms or it may extend forwardly and down through the mast and back to a control station, such as the helm of a sailboat.