Swaan and Wahab 



HEAVE 



DOUBLE AMPUTUDE 



TRIMMED BY HEAD 



TRIMMED BY STERN 



WAVE LENGTH 105 tt 



PITCH ANGLES 

 DOUBLE AMPLITUDE 



MEAN TRIM ANGLE 

 M05 and 70 tt 



MOMENT OF YAW 

 DOUBLE AMPLITUDE 



f 0_ 



d I 



HEAVE 



MEAN RISE HEIGHT 



5 _ ACCELEFiATION FORVU&.Ri 



ROLL ANGLES 



DOUBLE AMPLITUDE 



LATERAL FORCE 



DOUBLE AMPLITUDE 



ACCELERATION AFT 



—SPEED IN KNOTS 



- SPEED IN KNOTS 



-SPEED IN KNOTS 



Fig. 14 - Effect of trim on the behaviour in waves. Wave direction 135' 

 (bow sea), wave height 2 feet, 2580 fan revolutions per minute 



The effect of a beam sea combined with a side wind was investigated for a 

 speed of 28 knots only. The measured data are given in Fig. 13. It shows that 

 the effect of a side wind was very small. 



CONCLUSION 



With regard to the behaviour of the vehicle the following general conclusions 

 may be drawn. 



The design with rigid jet exits proved to be dynamically unstable over water 

 especially in regard to rolling. Minor changes in the jet exit arrangement could 

 not remove this difficulty. The installation of flexible trunks, however, improved 



710 



