NOVELTY - A vessel (1) has a mast structure (15) and a rigid wing sail. The mast structure has a mast top (17) rotational about a vertical wing sail rotation axis to adjust angle of incidence of wind. The wing sail has a main panel (31) joined at the middle to the mast structure via one tilting assembly (20), and a top panel (35) joined at the lower end to the upper end of the main panel via another tilting assembly (40). Both panels are tilted about respective tilt axes (21,41) parallel with each other and perpendicular to the rotation axis. The mast structure foot (16) is secured to the vessel.    USE - Vessel. Uses include but are not limited to e.g. a catamaran vessel, a mono-hull vessel, a cruise liner, a ferry.    ADVANTAGE - The wing sail can be brought into the docked position, in which the main panel becomes horizontal and the top panel extends vertically downward, allowing for easier access to equipment e.g. communications equipment, radar, signaling lights, at the top of the top panel by maintenance crew. The top panel is temporarily tilted with the main panel in sailing position to temporarily reduce the wing sail height to a Panamax height so that the vessel can pass under bridges. Securing the top panel while the wing sail is in docked position avoids risk of undesirable wing sail motion, while allowing for safe working conditions for maintenance personnel. The closer spacing between mast structures without overlapping the docked wing sails facilitates maintenance crew access to the lower ends of the wing sails. Making the wing sail foldable to reduce horizontal extension of the wing sail in docking position minimizes shadow formation over the vessel decks and permits for clear deck space for e.g. a helicopter pad. Filling balancing tanks to effect shift of center of gravity towards one tilt axis reduces effort to tilt the wing sail in controlled manner. The water balancing system can also stabilize the wing sail in vertical sailing position. The mast structure may be telescopic to reduce the height of the vessel when needed. The main panel may be extended as an upward ramp which may be of use when harvesting solar energy with photovoltaic cells on the wing sail.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a method for transportation with a vessel; and    (2) a method for operating a vessel.    .    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic perspective view of a wing sail installation in sailing position.    Vessel (1)    Mast structure (15)    Foot (16)    Mast top (17)    One tilting assembly (20)    Tilt axes (21,41)    Main panel (31)    Top panel (35)    Another tilting assembly (40)