Abstract
The tow force of tugboat has been brought through the bollard pull test, it execute under the condition of calm water and no forward speed. However, since the tugboat usually works in waves, the towing ability has to be examined in waves. In case of shallow propeller immersion depth I/D (Immersion depth/ Propeller diameter ratio), it will be supposed that a tugboat caused the tow force reduction due to the propeller racing in waves. In this paper, we examine the characteristics of mean tow force of tugboat for various factors, such as I/D ratio, wave height, wave direction, towing speed, wave length/ship length ratio X/L, through ship model experiment. In the water tank experiment, two types of ship models are used, which equipment a single kort nozzle Propeller or twin Azimuth Drive Propeller (A.D.P), respectively. Main results are as follows; 1) The mean tow force Tm in calm water and in wave clearly decreased with shallow I/D ratio. 2) Concerning with the influence of wave direction, the mean tow force Tm decreased with the wave height in head waves, but Tm increased in follow waves. 3) The influence of the wave length/ship length ratio X/L and towline length on Tm was slight.
