Abstract
The characteristics of lift and drag of the saucer-shaped otter board were studied using models with five kinds of cambers (0, 5, 10, 15, 20%). The models attached with appendages were rigged for an attack angle of between 0°and 30°and for an inward heel angle of between 0°and 10°at 5-degree intervals. The horizontal lift, drag and moment were measured by a three-component load cell in a circulating test tank. The lift and drag coefficients, lift-drag ratio and coefficient of pressure centre were then calculated.Only from the mean lift-drag ratio which was narrowly defined and calculated using the width of 5°on both sides of the attack angle at the maximum lift-drag ratio for all models, it was difficult to evaluate the efficiency of the otter boards because the variation of the mean lift-drag ratio at given different cambers was not significant. Therefore we judged the stability of the otter boards both from the width of attack angle at 75% of the maximum lift-drag ratio and from the coefficient of pressure centre. As a result, the otter boards with cambers of between 15% and 18% and with an attack angle of between 10°and 30°were stable and better than the others.
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