Norrbin 



lapping 



LT2/V 



06 as 



LT2/7 



Fig. 12. Rotary force and moment derivative data with mean 

 regression line . (Cubic fit to experimental results.) 



1.69 • 1 • k^ - 0.04 



- 1.28 • I • ^ +0.02 



1.29 ^ ' ^ - 0.18 



4 V 



_ 1.88 I • ^ + 0.09 



(6.4) 



and of the data 100, 86, 67 and 79 per cent respectively, appear 

 within ± 20 per cent of these mean values. 



It is obvious that these expressions should be regarded as 

 guide values only, but they may also be used for comparative studies, 

 especicdly when steering on a straight course is of main concern. 

 In this latter case it is more important to have a proper knowledge 

 of the control derivatives, whereas Eq. (6.4) may furnish adequate 

 estimates for the hull forces; they again shall be corrected for 

 alternative control arrangement alternatives, however. 



842 



