Abstract: An improved harness line apparatus for windsurf and other wind propelled vehicles having an elongated U-shaped curvilinear harness line made of stiff and resilient material. The ends of the stiff harness line are firmly secured to selected points along a wishbone configured boom to withstand gravitational and inertial forces. The harness line extends from the boom towards the sailor and is curved downward such that the middle of the harness line is in close proximity to but just below the harness hook when the sailing vehicle is upright and the sailor is positioned upright on the vehicle. As the sailor leans back into the wind, the sail and boom are rotated about a mast-hull pivot, but the relative positioning of harness line to harness hook is preserved. An improved length adjustable harness line is disclosed as are two improved versions of detachable harness lines.