NOVELTY - The device (15) has a fairing (51), rotationally attached to and encasing a mast (17), including two fairing sections (59,61). One of the sections, extending from the base end (53) to a point within the minimum cone of rotation (41a) defined by the stays (27a,27c) and elongate body (25) of the mast, has a symmetrical airfoil cross-sectional shape with a projecting rounded forward face (63) and an extending tapered back (65). The fairing rotates fully relative to the wind to provide aerodynamic lift in one position or not provide such lift in another position.    USE - Device for powering craft, such as watercraft e.g. single- or multi-hulled boat, a land craft, or ice boat, by aerodynamic forces.    ADVANTAGE - The fairing allows the mast to withstand extreme wind, and can be released to feather in the wind at a position in which no aerodynamic lift is produced without interference from the stays. Since the device can be fitted to an existing mast equipped with stays, the device can also retrofit the craft formerly fitted with sails. The core of the fairing allows the fairing to utilize a rigid exterior shell in a manner reducing the fairing thickness. The device has aerodynamic lift surfaces which can be controlled through all wind conditions, and is structurally robust for carrying the sails.    DETAILED DESCRIPTION - The device (15) has a fairing (51), rotationally attached to and encasing a mast (17), including two fairing sections (59,61). One of the sections, extending from the base end (53) to a point within the minimum cone of rotation (41a) defined by the stays (27a,27c) and elongate body (25) of the mast, has a symmetrical airfoil cross-sectional shape with a projecting rounded forward face (63) and an extending tapered back (65). The other fairing section extends from one fairing section to the top end (55) in manner parallel to the minimum cone of rotation. The fairing rotates fully relative to the wind to provide aerodynamic lift in one position or not provide such lift in another position. The fairing has an exterior shell of plastic, aluminum, fiberglass or carbon fiber, and a core of plastic foam, balsa wood, or plastic honeycomb. An INDEPENDENT CLAIM is also included for a method for powering a watercraft by aerodynamic forces.    DESCRIPTION OF DRAWING(S) - The drawing shows the side view of a device for powering a craft mounted to a watercraft.    Device for powering craft (15)    Mast (17)    Elongate body (25)    Stays (27a,27c)    Minimum cone of rotation (41a)    Fairing (51)    Base end (53)    Top end (55)    Fairing sections (59,61)    Projecting rounded forward face (63)    Extending tapered back (65)