Scale Effect of Full Hull Forms with Various Stern Shapes

Abstract

In order to investigate the effect of the stern shape on the scale effect of resistance and self-propulsion factors, each two geosims were tested for the hull forms with four types of different sterns, which are U shape frame lines with normal and swelled sterns and V shape frame lines with single and twin screw propellers.As expected beforehand, V shape of frame lines gives lower form factor values both under full and ballast load conditions. At the full load condition tendencies of variation of form factors for each hull forms are quite similar to each other, contrary to our expection, and values of form factor increase gradually with the increase of Froude no. Whereas, at the ballast condition, hump and hollow exist on the (1+K) curves throughout the speed range tested.The values of the wake and thrust deduction coefficients vary considerably owing to the variation of the stern shapes, but the scale effects of the self-propulsion factors are not so great in this scale range of rather big models.Authors introduce the new parameter lm/D, to define the mean clearance between a ship and a propeller and some discussions about the relation between nominal wake and effective wake, and about the scale effect of wake are presented.