Sailing Performance of Ocean Cruising Yacht by Full-Scale Sea Test

Abstract

The sailing performance of a 10.6 m-LOA ocean cruising yacht was measured by sea test and the results were compared with calculated values. The sea test was carried out to examine the steady sailing performance as well as the dynamic performance in waves.First, the steady sailing performance was estimated by calculating the velocity prediction program (VPP). The VPP calculates the equilibrium sailing state of the boat considering the balance of X, Y forces and K, N moments, respectively. The hydrodynamic force coefficients of hull were derived by the towing tank test using 1/4.275 scale model, and the aerodynamic force coefficients of sail were calculated using the results of a wind tunnel test.Then, the sailing state parameters of the full-scale were measured under various wind conditions. The measured items were wind velocity, wind direction, boat velocity, leeway angle, heel angle and rudder angle. These values were compared with the results of VPP. The both results were in good agreement and this indicates that the calculating method and fluid dynamic coefficients for VPP were adequate.Next, The motion of the boat was measured in conjunction with wave measurement using a throw-in type wave meter. A vertical gyro and accelerometers were used for measurement of rolling, pitching and heaving motion of the boat. These data were analyzed by means of spectral analysis, and compared with both model test and numerical calculations. The model test was performed in regular wave conditions at the towing tank. The analyzed results indicated the sail damping effect on the rolling motion quantitatively and the distinctive feature of motion for the sailing cruiser in waves.