Thus, for the results presented in this report gravitational loads and 
centrifugal loads scale the same. Furthermore, if proper allowance is 
made for the difference in density between the model propeller and the 
full scale propeller,* the gravitational and centrifugal loads scale the 
same as the hydrodynamic loads. 
Therefore, in addition to the components of loading arising from 
hydrodynamic effects alone, for many experimental conditions the compo- 
nents of loading arising from the sum of hydrodynamic, centrifugal, and 
gravitational effects are presented. The components of loading arising 
from the sum of the hydrodynamic, centrifugal and gravitational effects 
are designated components of total loading. The centrifugal and gravi- 
tational loads presented are equivalent values for a nickel-aluminum- 
bronze propeller blade. These combined, or total, loading results are 
discussed in later sections. 
The time-average centrifugal spindle torque results, M, are com- 
c 
pared in Figure 9 with calculated values using the method of RELL 
Previous measurements of spindle torque by Boswell et anki and by Hawdon 
et ai have correlated well with values calculated by this procedure. 
The calculated value of M, is 33 percent lower than the experimental 
c 
value at design pitch (see Figure 9); however, this is within experimental 
accuracy. The largest measured value of M, is 0.5 inch-pounds (0.07 N-m) 
e 
as shown in Table 6 whereas the accuracy of this measurement is plus or 
minus 0.2 inch-pounds (0.02 N-m) as discussed in the section on accuracy. 
The large experimental inaccuracy as a percent of the measured M, value 
c 
results from a combination of (1) the small value of the measured M, ; 
c 
and (2) the inferior characteristics of flexure number 3, which measures 
*The model propeller used in these experiments was made of aluminum, den- 
sity pp=5.44 lbf-s2/£t4 (2.80 g/cm3). The full scale propeller on the 
DD-963 is made of nickel-aluminum-bronze, density Pp=14.48 lb£-s2/f£t4 
(7.46 g/cm3). 
re crieilil, R.J. et al, "Experimental Spindle Torque and Open-Water Per- 
formance of Two Skewed Controllable-Pitch Propellers," David Taylor Naval 
Ship Research and Development Center Report 4753 (December 1975). 
28 
