Manoeuvrability and Propulsion of Very Large Tankers 



action was measured as a function of time. A qualitative diagram of the differ- 

 ent quantities such as 0, /', U, o and the lateral displacement of the ship is 

 shown in Fig. 15 whilst Fig. 16 defines the quantities used. 



The Results of the Comparative Z Manoeuvring Tests 



One of the main reasons for this investigation was to devise criteria and 

 the possible regions of application for conventional rudder steering and jet 

 steering. It was clear that at service speed it would be difficult to improve on 

 the conventional system since the power requirements for jet steering might 

 become excessive. 



A common yardstick for both steering systems was considered to be the 

 maximum value of the yaw angle rate 4'^^^. Figure 16 shows the behaviour of 

 as a function of time during the z manoeuvring tests. During the experiments 



^i// HEADING ANGLE, U NOZZLE EXHAUST VELOCITY, S RUDDER ANGLE 



S,U 



I '2 



MEASURED QUANITIES vl/ v/' U S 



Fig. 15 - Path of some innportant steering 

 quantities as a function of time 



259 



