A Study on the Turning Ability of Twin-engine, Twin-propeller, and Twin-rudder Ship 'KAKUYO MARU'

摘要

We made the turning trial of "KAKUYO MARU", which was equipped with two engines, two propellers and two rudders, to find out the steady turning diameter, the turning time and the turning speed reduction ratio. The results of trial are stated below. 　1) The size of steady turning diameter depended on the rudder angle and was little affected by the turning speed.　2) The ratio of the steady turning diameter to the ship length between perpendiculars (D/L) was inversely proportional to the rudder angle, and its regression formula was expressed as y=20.361x-^l.OOOl.　3) The turning time was inversely proportional to the rudder angle and the turning speed, and its regression formuia at 10 degrees of rudder angle was expressed as y_1O°=453.l7x^-O.6797.　4) The turning speed reduction ratio changed in proportion to the rudder angle and was almost constant even though the turning speed changed.　5) In comparing the measured D/L values by turning speed and rudder angle with Sugihara's nomogram values, the error between measured values and nomogram values was 13.6% at most. Accordingly, Sugihara's nomogram can be applied to a twin-engine, twin-propeller, and twin-rudder ship also.　6) As for the effect of ship's bottom fouling on the turning diameter, the steady turning diameter varied inversely with the period elapsed from the last bottom cleaning in a dock, and its regression formula at 10 and 20 degrees of rudder angle were expressed as y_1O°=-0.6313x^2-0.7471 x +394.8 and Y_20°=-0.6529x^2+4.2921x+189.4 respectively.