Design Method for Contra-Rotating Propellers for High-Speed Crafts: Revising the Original Lerbs Theory in a Modern Perspective

Table 3

Main characteristics of CR propellers used for the parametric investigation.

	Case A-l	Case A-2	Case A-3
Front number of blades	4	4	4
Aft number of blades	4	4	4
Front EAR	0.82	0.87	0.79
Aft EAR	0.94	0.98	0.89
Strength margin	5	6	5
Cavitation margin fore	0.78	0.78	0.83
Cavitation margin Aft	0.7	0.7	0.75
Unloading curve	Y	Y	Y
Propeller efficiency	0.704	0.699	0.71