7. NUMERICAL SIMULATION OF TACKING OPERATION
Using the aerodynamic coefficients in Figure 15, the numerical simulation of tacking operation was performed. In this case, we have no measured data by the reconstruction ship. Therefore we assume that the tacking starts from the beating to wind condition in Figure 11. The simulated results are shown in Figure 16. The rudder is steered from 3 degrees to -15 degrees for tacking. As shown in the figures, with decreasing of heading angle of the ship, the velocity decreases and leeway angle increases rapidly. The trajectory shows that the ship heads to wind and comes to a standstill. This means that the ship is "caught aback" in the wind or fall "in iron" condition. If the rudder is steered from 3 degrees to -5 or -10 degrees for the tacking, the results are almost same. Moreover, it can be considered that the operation of turning around of the yard about 1 80 degrees might involve the great difficulties in strong wind From these results, we should conclude that this ship could not perform the tacking operation.
8. CONCLUDlNG REMARKS
It has been our wish for a long time to reveal the sailing performance of the typical Japanese sailing trader, which has already disappeared into history. In this report, we focused on the maneuver characteristics at both wearing and tacking operation of this ship. From the measurements at the wearing operation, the response of ship state parameters was shown in detail. Then we proposed the numerical simulation method of maneuvering motion. For the wearing operation, it can be considered that the numerical simulation indicates the ship performance very well when the sail is trimmed appropriately.
Simulated results at tacking maneuver (from port tack)
Finally, the tacking maneuvering performance was discussed. In order to clarify the sail performance in upwind condition, both the numerical calculation by the Vortex Lattice Method and the wind tunnel tests were carried out. The simulated results using these sail coefficients showed that this ship could not perform the tacking operation.
Unfortunately, our co-author Professor Kensaku Nomoto passed away by sea accident on 20 July 2002. The sea trial and measurements of the Naniwa-maru would not have been realized without his enormous effort. We all express our regret over his death. The Naniwa-maru is now set in the Osaka City Maritime Museum named "Naniwa-no-Umi-no-Jikukan", and never sails out on the sea any more.
 Nomoto, K., Masuyama, Y. and Sakurai, A., "Sailing Performance of "Naniwa-maru." A Full-Scale Reconstruction of Sailing Trader of Japanese Heritage," 15th Chesapeake Sailing Yacht Symposium, SNAME, 2001.
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 Masuyama, Y., Fukasawa, T. and Sasagawa, H., "Tacking Simulation of Sailing Yachts - Numerical Integration of Equations of Motion and Application of Neural Network Technique," 12th Chesapeake Sailing Yacht Symposium, SNAME, 1995.
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 Masuyama, Y and Fukasawa, T.: "Full Scale Measurement of Sail Force and The Validation of Numerical Calculation Method", 13th Chesapeake Sailing Yacht Symposium, SNAME, pp.23-36, 1997
Professor, Division of Mechanical Engineering, Kanazawa Institute of Technology. Yutaka Masuyama, who is now fifty-six, graduated from the Dept. of Mechanical Engineering of the graduate school of Toyama University in 1971. He worked as an apprentice at the Kumazawa Craft Laboratory, yacht design office, from 1972 to 1975. From 1975, He has been working at Kanazawa lnstitute of Technology. His main field is fluid dynamics and naval architecture, in particular sailing science. He has been studying about the sailing performance of a hydrofoil sailing boat to the America's Cup boat. He is also interested in the performance of small water vehicle such as a hydrofoil solar boat.
Professor Emeritus, Osaka University. Kensaku Nomoto graduated from the Department of Naval Architecture of Imperial University of Kyushu in 1947. Then he has been working at the Department of Naval Architecture of Osaka University. He was Professor in Naval Architecture up to 1987, and then Professor Emeritus of Osaka University. He was also Professor in Ship Technology of World Maritime University, IMO/UN, Malmoe, Sweden up to 1987. He made a major contribution in the field of ship motion dynamics particularly in the maneuvering. His study provided the base of autopilot system of ship. For his achievements he was awarded the Gold prize of the Columbus Prize, presented by Genoa city, Italy, and also the Prize of the Minister of Transport of Japan. Unfortunately, he passed away by sea accident on 20 July 2002. He was 76 years old. His death is heavy loss to the Society of Naval Architects and Sailing Federation of Japan.
Professor, Dept. of Aeronautics and Astronautics, Kyushu University. Akira Sakurai, who is now sixty-one, graduated from the Dept. Aeronautical Engineering (present Aero. & Astro.) of the graduate school of Kyushu U. in 1970 and has been working at the same department since then. He worked in the field of computational fluid dynamics of compressible Navier-Stokes equations in his early days, then turned his attention to various aspects of experimental fiuid dynamics. At present his main interest lies in the field of autonomous, unmanned vehicles. He is also an avid sailor.
Professor, Division of Mechanical Engineering, Kanazawa Institute of Technology. Toichi Fnkasawa, who is now forty-nine, graduated from Graduate School of University of Tokyo (Naval Architecture) and received the Doctor of Engineering in 1981. He worked as Research Associate at University of Tsukuba from 1981 to 1984, as Lecturer at University of Tokyo from 1984 to 1985, as Associate Professor at University of Tokyo from 1985 to 1992, in the field of Naval Architecture. His main research field is fluid-structure interaction problems. He has been working as Professor at Kanazawa Institute of Technology from 1992 to present in the field of vehicle dynamics.