コルトノズルが肥大船の操縦性に及ぼす影響に関する模型実験

抄録

This report presents the results of a number of steering tests of two free-running, self-propelled tanker models with several rudder configurations including the attachment of a Kort-nozzle. 1) Model A with a l/57 relative size rudder shows an abnormally stable character in straight running and this is emphasized by fitting the smaller rudders against expectation. 2) Model B with a l/63 rudder shows an unstable loop and the smaller rudders result in the wider unstable loops as one may expect. 3) By fitting a Kort-nozzle for these two models which have typically different characters, r'∼δ curves around origin are shifted to bring worse course stabilities for any size of rudders. The nozzle affects the stable model much and the unstable one less. 4) At ballast conditions of model A, almost same characters are obtained whether with a nozzle or not and irrespective of rudder area. But when the largest l/57 rudder is fitted, the model shows slightly better response for both cases of that with and without nozzle. 5) For improving course stability, it has been thought that increasing of rudder area is the simplest way for usual stern form ships but in case of model A, the better characters are provided by the smaller rudders. Even in the case with a nozzle, slightly better effects are obtained by cutting the upper part of a l/57 rudder. In case of model B with a nozzle, the upper part of l/63 rudder has no effects on course stability. These facts impress that the upper part of a conventional rudder does not play an important role but sometimes causes bad influences.