THE APPLICATION OF PHOTOGRAMMETRY IN THE STUDY OF THE EFFECTS OF SAILBOARD FIN FLEXIBILITY

In recent years, the reduction of aero- or hydrodynamic drag on fins a nd finite wings by passive means has been a popular research topic. Am ong many drag reduction devices being investigated, the flexible tip i s of particular interest to non-aerospace application. In the wind-sur fing industry, slender fins with flexible tips have shown high perform ance recently. The development of sailboard fins, however, has been on a trial-and-error basis and the physics behind the improved performan ce has not been fully understood, although some suggest that the flexi ble tip helps to reduce the induced drag. At Exeter University a serie s of comparative studies has thus been carried out in order to help fu lly understand the effects of tip flexibility on performance. This pap er presents the experiments which were aimed at observing and measurin g the bending deflection and twist of the fins of various degrees of r einforcement due to fluid dynamic forces. Fin deformation was measured by means of photogrammetry which is a low-cost non-interfering techni que suited for steady displacement measurement.