LOW-SPEED HARBOUR MANOEUVRING OF FERRIES

In the summer of 1991 two converted ro-ro passenger ships, ASK and URD were put into service on the Kalundborg-Aarhus route, between Zealand and Jutland in Denmark. After a short time severe manoeuvring difficulties were experienced, which resulted in time delays and damage to the ferry berths. The most severe problems occurred in Kalundborg where the ferries have to stop and turn just before reaching the berth, which they have to reverse into. It was concluded that the manoeuvring problems occurred because the available lateral forces, both fore and aft, were too small. Another problem was insufficient reversing force, especially when a lateral force aft had to be generated with one propeller running ahead. To increase the lateral force forward it was decided to install an extra bow thruster. The next step to increase the manoeuvrability when reversing was to repair and upgrade the propeller and main engine control system so that the full engine power could be delivered to the propellers, when reversing. However, these steps were not sufficient to solve the manoeuvring problems. The article discusses the installation of a stern thruster and larger rudders to solve the problem. A comprehensive and systematic model test programme was carried out, and before the implementation of the solution on the ships, it was tested on a manoeuvring simulator.