Str^m-Tejsen and Chislett 



= 06 



9 0-5 

 I 0.4 



C 



z 03 



E 



I 02 



Fig. 2Z - Relationship between the non- 

 dimensional yaw velocity and the shaft 

 revolutions as a function of model speed 

 and model size (for 100 mm amplitude 

 at the scotch yokes) 



particular manoeuvre. For example, if interest is centred on the steady turning 

 state corresponding to maximum rudder-angle, then acceleration terms are of 

 minor importance and tests need only be made for one rudder angle, and for 

 drift angles, yaw velocities, and speeds covering a range centred about the esti- 

 mated equilibrium state. 



On the other hand, to obtain coefficients which truly represent the sym- 

 metry inherent in ship forms and reflected in the design of the mathematical 

 model, it is necessary to plan the experiments accordingly. In particular, two- 

 variable crosscoupling terms should preferably be obtained from measurements 

 corresponding to a range of parameters in which at least one of the parameters 

 is assigned both positive and negative values. The numerical values of the coef- 

 ficients will then uniquely describe the steering and manoeuvring properties of 



350 



