Full Scale Measurement of Sail Force and the Validation of Numerical Calculation Method

Abstract

Sail forces were measured in a full-scale sailing boat with the use of a sail force dynamometer. This apparatus consisted of an aluminum frame fixed to the hull by way of several load cells. The sailing boat was modified so that the dynamometer frame could be installed inside the hull. The mast, stays, winches, and other sailing rig were fixed on the frame so as to transmit all the forces acting on sail to the frame. By transforming the measured forces, the lift force, drag force, thrust, side force, or the center of effort of the sail force could be obtained. The sailing conditions of the boat, such as the boat speed, heel angle, wind speed, wind angle, and so on, were also measured. Sail shapes of the boat in the up-wind condition were also measured with the use of CCD cameras installed in the boat. The sail shape images taken by the cameras were transformed to bit-map files, and then processed by an SSA-2D, a sail shape analyzing software. With the use of this software, sail shape parameters were obtained. The relationship between the measured sail forces and the sail shape parameters is discussed in this paper. Moreover, the measured sail shapes were used as the input data for the numerical calculations. Numerical calculations were performed to estimate the sail forces of the boat. In the calculations, two sails, a mainsail and a jib , were modeled in the form of a vortex lattice. The vortex lattice method was adopted as the numerical calculation method. Step by step calculations were conducted up to attaining the steady state of the sail in steady wind. Calculated sail forces were compared with the measured forces, and the validity of the numerical method was studied.

Numerical and Experimental Studies of Sail Aerodynamics

“…The methodology to achieve the goal of this investigation has been reproducing the full-scale tests described in [30], [31] and [32]. Three sail arrangements have been simulated specifically with the commercial packages ANSYS-CFX and CD-Adapco's STAR-CCM+.…”

“…The methodology to achieve the goal of the investigation presented in this chapter has been reproducing the full-scale measurements obtained from the previously mentioned paper [31] together with [30] and [32]. Yutaka Masuyama and Toichi Fukasawa built the sail dynamometer boat Fujin (figure 6.1) in the late 90s, as mentioned before in chapter 3.…”

“…In 1997 Masuyama and Fukasawa built the sail dynamometer boat Fujin that was similar to the MIT dynamometer. The results using IACC and IMS type sail were reported in different papers such as [30], [31] and [32]. One of the most recent project was initiated in Germany in which the 10-meter full scale sail force dynamometer was named DYNA.…”

“…Full-scale sail tests were performed using the sail dynamometer boat Fujin [30]. The Fujin was originally built for conducting tests on sails for the Japanese America's Cup entry in 1994.…”