Full-Scale Flow Visualization of the Maneuvering Racing Sailboat*

While turning a sailboat through the wind, Olympic sailors will intentionally roll the boat to the point of near capsize – either executing a “roll tack” when sailing upwind or a “roll gybe” when sailing downwind. To modulate heel angle on the boat and avoid capsize, the sailor will shift their bodyweight to the opposite side of the boat’s longitudinal axis during the motion. These rolling maneuvers effectively “whip” the mast and sail across the boat, producing a forward propulsive force. In generally light conditions, the proper execution of these techniques allows the sailboat to propel itself faster than under steady wind alone – a critical advantage while racing. On Lake Cayuga’s waters, we study the kinematics underpinning these maneuvers by outfitting an Olympic Laser sailboat with IMU and GPS sensors and an array of GoPro cameras. Comparisons are made between the performance of the steady sailing boat and the flat or rolling tack and gybe. The vortex dynamics associated with the sail’s unsteady whipping motion is visualized at full-scale on the water by sailing the boat within a cloud of smoke produced by smoke canister and captured in footage via flying drone camera.