1971 Volume 46 Pages 77-80
The author published in 1968 on the course stability of SHIOJI MARU, the ship of Tokyo University of Mercantile Marine, and alluded in the report to the effectiveness of a fin fitted above the rudder to her course stability. As the fitting of the fin was not sufficient to remove unstableness, they renewed the rudder which has the rudder ratio A_R/L・d=1/32.3, in comparison with the old one of 1/38.4. After several tests of maneuverability, renewal of the rudder remarkably contributes to improve maneuverability indices, and yet unstableness is not removed. Merely for improvement of course stability at straight course, fitting a fin having suitable area is prefer to the renewal of the rudder.