NEW INSIGHTS INTO VOITH SCHNEIDER TRACTOR TUG CAPABILITY

The emerging use of tanker escort in restricted waters requires tugs that are capable of rendering effective retarding and steering assistance to large ships operating in the 6 to 12 knot speed range. This paper presents findings from a coordinated program of model tests, computer simulations and full scale trials which have yielded new insights into the capabilities of Voith Schneider propelled tractor tugs. The emergency assist capabilities are shown as speed- dependent contours of the vector assist force in the coordinates of the assisted vessel. For tractor tugs the capabilities increase with speed. Simulations of tug assisted tanker manoeuvres at 10 knots show that the tractor tug is more effective than a conventional tug in controlling the behaviour of a disabled tanker.