1. The c/D at each radius was the same as that on the FFG-7 propeller; 

 however, the t/c was increased to up to 5/3 times the value on the FFG-7 in order 

 to allow sufficient thickness in which to recess the gages. 



2. A balanced distribution of skew was used with slightly smaller magnitudes 

 of skew than on the FFG-7 propeller. The projected skew angle extended from 



-5 deg at the 50 percent radius to +20 deg at the tip. 



3. The design advance coefficient J. was reduced from a value of 1.077 on 



A 



both the FFG-7 propeller and Propeller 4679, to 0.751 on Propeller 4718. Therefore, 

 at design J , the experimental propeller rotational speed n is increased for a 

 given speed of advance V.. This increases the local Reynolds number R at a given 

 V and increases the number of propeller revolutions for a given pass down the 

 towing basin. The increased number of runs provided improved statistical data. 



4. The design thrust loading coefficient C , was reduced to approximately 

 3/5 times the value on the FFG-7 propeller so that the design thrust loading 



coefficient per blade is approximately the same as on the FFG-7 propeller. 



28 

 The propellers were designed using the lifting line procedure of Caster et al. 



29 

 for the preliminary design, and the lifting surface procedure of Kerwin for the 



final design. The results of the lifting line calculations are shown in Table 2. 



The geometric details of the model propellers are presented in Figure 1 and Table 3. 



Photographs of the propellers are shown in Figure 2. 



EXPERIMENTAL TECHNIQUE 

 FACILITY 



All experiments were conducted on DTNSRDC Carriage V. The propeller was driven 

 from downstream using the drive system and housing of the DTNSRDC 1000 hp dynamometer. 

 This dynamometer system uses two 500 hp (0.372 MW) electric drive motors located in 

 a pod attached to the lower end of a strut. The test arrangement is shown in 

 Figure 3. 



The 1000 hp dynamometer was mounted to the carriage in two different 

 orientations: 



1. With the propeller shaft parallel to the direction of the carriage advance 

 so that the propeller operated in uniform flow, and 



2. With the propeller shaft inclined 7.5 deg downward from the direction of 

 the carriage advance so that the propeller operated in inclined flow. 



