4.4 Side Force due to Inclined Propeller Plane

　

 When rotating the pod unit to control the ship the propeller plane will be placed at an angle of attack to the flow. By considering the thrust to have both a longitudinal component and a lateral component the side force as a function of pod angle can be derived as given in Eq.(19). However, for small angles of attack the sine of an angle is approximately the same as the angle itself, result in Eq.(20).

　

　

　

4.5 Pod Stabilising Effect

　

 When the pod is in the straight-ahead position it acts in a similar manner to a fin, serving to stabilise the ship. The derivative contribution of this fin must be calculated and added to that of the hull itself. Although not at an angle of attack the accelerated propeller race helps to stabilise the ship. The respective areas and velocities should be calculated and applied as in Eq.(21).

　

 The stabilising effect of a pod fitted with a control flap is calculated in the same way but with the appropriate lift curve slope. The corresponding derivative contributions are given in Eq.(22) to (24).

　

　

　

4.6 Pod Control Force

　

 The control force for an azimuthing pod or control flap must be calculated to establish the manoeuvring characteristics of the design. The control force for an azimuthing pod does not benefit from the accelerated propeller flow however it does have the thrust contribution as shown in Eq.(25). Conversely, control by use of a flap surface benefits from the propeller race effects but not the thrust as shown in Eq.(26). Finally, the respective yawing moment control forces are given as a function of the longitudinal position of the pod in Eq.(27) and (28).