The final calibrations used during the test were conducted in the laboratory 

 with water in the pressure tank and gage cavities. A series of automated calibra- 

 tions were performed, and averaged. A second series of calibrations was conducted 

 midway through the test which resulted in a slight variation in sensitivity of the 

 gages, which was attributed to exercising the gages during the first part of the 

 test. From these calibrations, the degree of expected accuracy of the pressure 

 measurements was obtained. For any single calibration, the error band, based on a 

 95 percent confidence level was calculated from the standard deviation relative to 

 a straight line calculated sensitivity. The average error band of all gages for the 

 pretest calibrations was +0.035 psi (0.24 kPa) . The average difference between the 

 pretest and midtest calibration sensitivity was 0.022 psi/V (0.15 kPa/ V) . For a 

 typical measured pressure coefficient of -0.4 this variation in calibration sensitiv- 

 ity corresponded to 0.015 psi (0.10 kPa) at low test speeds (V = 6 knots) and 

 0.035 psi (0.24 kPa) at high test speeds (V = 11 knots). An expected upper and 

 lower bound on a given pressure measurement could be formulated by simply adding the 

 above sources of error. 



1. Expected error at low test speeds - +0.050 psi (0.34 kPa) 



2. Expected error at high test speeds - +0.070 psi (0.48 kPa) 



EXPERIMENTAL CONDITIONS 



All experiments on Propellers 4679 and 4718 were conducted with the blades set 

 at the design pitch. Table 5 indicates the test conditions. The values of carriage 

 speed V , rotational speed n, resultant inflow speed at 0.7 radius V _ _, Reynolds 

 number R , and advance coefficient J are nominal values. Generally, the final 

 measured quantities were averaged over the number of runs at each condition and 

 varied slightly from the quantities indicated. Most conditions were run at the three 

 indicated configurations of uniform flow, 7.5 deg inclined flow, and uniform flow 

 with the static pressure taps covered with tape to determine loading effects on the 

 pressure gage output. 



DATA COLLECTION 



The data which were recorded during the experiment included 40 channels of 

 blade-surface pressure, propeller rotational speed, carriage speed, and wave height 



10 



