oscillation (with the resonance at 100 to 200 hertz) from being trans- 
mitted to the blade flexures. Based on the measured resonance, it is 
concluded that the soft-mount system should successfully meet this ob- 
jective. Although some resonances were close to the propeller rotational 
speed for some experimental conditions, it was considered more desirable 
to isolate the system from towing-carriage vibration. 
EXPERIMENTAL CONDITIONS AND PROCEDURES 
Experiments were conducted at several conditions including steady- 
ahead operation, simulated pitching of the hull, and simulated accelera- 
tion. All conditions were run with the model hull rigidly attached to its 
support, with no freedom to sink or trim, and with essentially equal rota- 
tional speed on the port and starboard propellers. 
The steady-ahead condition is defined in Tables 3 and 4. The simu- 
lated full scale ship speed and propeller rotational speed for this condi- 
tion were determined from model self-propulsion data* at simulated dis- 
placement of 7,800 tons (7,920 tonnes) including corrections for wind drag 
at zero true wind and a three-percent margin on effective power with 
Cy = 0.0005. 
The trim and draft at this speed were obtained from Reference 28. 
These had been determined by setting the specified still water trim (even 
keel) and draft (19.5 feet (6.40 m) full-scale equivalent), attaching 
the model to the carriage so that it was free to trim and sink, running at 
the specified speed, and locking the model at this equilibrium trim and 
draft. The equilibrium sinkage was 0.5 feet (15.4 cm) at the bow and 3.0 
feet (98.4 cm) at the stern. 
Runs simulating hull pitching were conducted at the same conditions 
as the steady-ahead run, except that the hull pitch was varied. Two types 
of runs were conducted: (1) quasi-steady simulation in which the hull 
pitch angle ~ was set at various fixed positions, and (2) unsteady 
*DTNSRDC experiments 21 and 22 on Model 5265-1B. 
eve W.G., "The Effect of Speed on the Wake in Way of the Propeller 
Plane for the DD-963 Class Destroyer Represented by Model 5265-1B," David 
Taylor Naval Ship Research and Development Center Report SPD-311-37 (July 
UGS) ¢ 
14 
