Murthy 



to the uniform motion and steady displacements. Also, the moment 

 of the thrust about the C. G. 



- k m T 

 T 



must be equal to the moment due to the fluid pressure. 



Using the expansion (5-5) for the longitudinal force and similar ex- 

 pansions for the vertical force and pitching moment, we may write 



T cos0 = 



1 + (8 2 , Z , 80) 



T = 8X, nnn + PX n , nn +8 2 X^ nnn 

 1000 0100 2000 



+ ^ X 0200 +5/3X 1100 + 0(52/3 '^ 2 ) 



(6-2) 



T sin0 = 



80 + 06 + 809 

 100 010 110 



T = <5Z + 0Z + 



1000 M 0100 



+ 8 Z + Z Z + 8BZ + (8 2 , 80 2 ) 



2000 M 0200 P 1100 V P ' P ' 



(6-3) 



- V ' 5M 100n + ^ M 0100 + ^2000 + ^0200 + 



+ 5/3M noo + ( 8 Z , 80 Z ) 



(6-4) 



It will be noted that we have not used terms containing a or e as 

 we are considering steady motion in calm water. 



Referring to (5-6) and (5-7) we see that 



x iooo = 



and x oioo = 



and, similarly, 



z iooo = 



and z oioo 10 



from conditions of equilibrium in the hydrostatic case. Similarly, 

 during static hovering, i. e. at zero speed ahead, the total moment 

 about the C. G, of the pressure on the cushion hull and that on the 

 side hulls should be zero for equilibrium 



i. e. 



' M iooo + * M oioo-° 



140 



