Some Problems of Tugs attending to Large Vessel

Abstract

As a large vessel diminishes speed in the channel, she commences to lose control of her bow, and tugs are used to push against the bow of the vessel. Though the tug can work with greatly reduced speed of the large vessel, if the latter can not kill her headway sufficiently, this is seldom the case. The present paper determines the limits of the speed of the vessel within which the effective work of tugs can be expected, by solving the subject as the problem of the static equilibrium. Calculations are made for the particular cases of 4, 000 shp tug with controllable-pitch-propeller and 1, 950 shp tug with Voith-Schneider-propeller. The result shows that the c.p.p. tug can work most effectively with about 4 knots of headway of the large vessel, while the v.s.p. tug with about 3 knots.