An Investigation into the Efficiency of Gybing Daggerboards Available to Purchase

This investigation was completed by the author as an undergraduate thesis to fulfill requirements for the Webb Institute of Naval Architecture. A one-quarter scale model of a Lark dinghy was equipped with a gybing daggerboard, a daggerboard allowed to rotate about its vertical axis. The model was tested in a conventional configuration at various leeway angles with the foil aligned to the center plane, in a gybing configuration at a series of angles relative to the hull, and in configurations combining hull yaw and gybing angles to simulate realistic performance. Side-force (lift) and resistance (drag) were measured and expanded to full-scale. The results were found to agree with the hydrodynamic theory of boats with gybing foils; namely that they have lower drag for a given lift force developed to place aerodynamic forces in balance. The exact change in performance is not known and requires a determination of velocity made good to windward in order to draw conclusions beyond the drag reduction found in this research.