This paper will present both numerical and experimental activities performed at DPA on the optimization of a keel system of a typical America's Cup Yacht configuration (fin-bulb-winglet). A panel code has been extensively used to find the best shape and position of winglets to be installed on a bulb, the shape of which is fixed. The bulb is in turn connected to a keel to form the complete underwater lifting system of the sailing boat. Systematic variations of winglets geometrical parameters such as span and dihedral angle as of their position along the bulb have been performed. The result of this study has allowed the selection of the best geometries to be tested in the wind tunnel on a scaled model of the complete keel. The tests have been performed in the wind tunnel belonging to the Chalmers Department of Thermo Fluid Dynamics in Sweden. Five-hole probe measurement of the wake behind the complete lifting system has been performed to assess the velocity field in the far wake. Then a specific numerical code based on the solution of the Poisson's equations has been set up to obtain the global induced drag. This code calculates induced drag using the Maskell's formula based on velocities measured in the wake. The advantage of using Maskell's formula is in the possibility to restrict the measurement area to the zone where the vorticity is different from zero.
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