The basic condition, which simulates steady ahead self-propulsion 

 in calm water with no ship motions, is defined as Condition 1 in Table 1. 

 The propeller rotational speed, trim and draft at this condition were 

 obtained from model self-propulsion data. No cavitation occurred on the 

 model propeller at any model experimental condition described in this 

 paper. 



Runs simulating hull pitching and/or the effect of waves were con- 

 ducted at the same conditions as the run in calm water with no hull 

 pitching, except that the hull pitch was varied and/or the model was 

 run in waves (Conditions 2 to 6 in Table 1) . These experiments were 

 conducted for forced pitching of the model in calm water, for operation 

 in regular head waves without pitching of the restrained model hull, 

 and for forced pitching of the model for operation in regular head 

 waves. For forced pitching in waves, the phase of the wave at the pro- 

 peller, il>j-, was varied relative to the phase of the hull pitching, ^^. 

 Three relative phases were evaluated: 



1. Wave crest at the propeller plane when the stern of the model 

 hull is pitched up at its maximum value, $^ - $^ = (Condition 4 in 

 Table 1). 



2. Wave crest at the propeller plane when the stern of the model 

 hull is pitched down at its maximum value, $j- - $^ = 180 degrees (Con- 

 dition 5 in Table 1) . 



3. Wave crest at the propeller planes when the hull pitch is 

 passing through its mean value (^I^j^iax ~ '^MIN^/^ from stern down to stern 

 up, $^ - $^ = 90 degrees (Condition 6 in Table 1). 



For the unsteady hull-pitch simulation in calm water, the hull- 

 pitch angle ij; was varied sinusoidally about the calm water equilibrium 

 trim angle i^n^j) with an amplitude ijj^ of 1.33 degrees and a frequency 

 f-^ of 0.8 hertz, f^L^/g'^ = 2.63. For operation in waves without the 

 hull pitching, the model hull operated in regular head waves with a 

 single amplitude r,^ of 0.118 m (0.39 ft), ^a/^w = 0.019; a wavelength 

 % of 9.20 m (30.20 ft), 1^/% = 1.62; and a wave velocity Vy of 

 3.79 m/s (12.43 ft/s) . At the experimental model speed of 3.58 m/s 

 (6.96 knots) the frequency of encounter is 0.8 hertz which is the same 

 as the model pitching frequency. Operation in waves with pitching of 

 the model hull necessitated a reduction in the amplitude of the pitch 

 of the model hull and/or the amplitude of the waves from the afore- 

 mentioned values in order to prevent flooding of the model hull. The 

 minimum amplitudes of the hull pitch and the waves were 0.67 degree and 

 75 mm (0.25 ft), respectively (see Table 1). The frequency of the hull 

 pitching and the frequency of encounter of the waves were both 0.8 hertz 

 for all experimental conditions with pitching and waves. 



The selected amplitude and frequency of encounter of the waves, 

 and amplitude and frequency of the hull pitching were within the scaled, 

 predicted operating and response characteristics at full scale of an 

 equivalent transom-stern ship. 



Air-spin experiments were conducted with all three flexures over a 

 range of rotational speeds in order to isolate the effects of 



