EN and M,> relative to the other two flexures as discussed in the section 
on calibration. 
INFLUENCE OF DYNAMOMETER BOAT 
The results of the wake surveys with and without the downstream body 
(dynamomemter boat) are presented in Figure 10, and in Appendix A. These 
data indicate that the downstream body had only a small effect on the 
circumferential and radial variation in the flow and only a small effect 
on the harmonic content of the flow. However, they also indicate that the 
downstream body reduced the volume mean velocity through the propeller 
disk by approximately 12 percent; i.e., without the downstream body the 
volume mean wake (1-w)=1.06 and with the downstream body (1- m7 0-93- 
W. 
These results are, of course, without the propeller in place. i 
The change in effective velocity through the propeller due to the 
downstream body was deducted from thrust and torque identities between the 
mean thrust and torque measured during the blade loading experiments at 
the self propulsion point (Condition 1 in Table 3), and mean thrust and 
torque measured during a previous self propulsion model experiment.* 
These results, which include the effect of the propeller, indicate that 
the downstream body reduced the effective velocity through the propeller 
disk by approximately 5 percent; i.e., without the body, (1-w,)J=1.02 and 
Caton men sou: whereas, with the body, (1-w,,)=0.97 and Cheat Ooe2 
The difference between the effect of the downstream body on volume 
mean wake and effective wake is probably due to a combination of the 
following: 
1. The effect of the propeller action; (1-w,) and Cy) include 
the effect of the propeller but (1-wyy) does not. 
2. Experimental inaccuracies; both methods for calculating the 
change in velocity are based on a small difference of two much larger 
nearly equal experimental results. 
*DINSRDC experiments 21 and 22 on Model 5265-1B, in which the mean 
thrust and torque was measured using transmission dynamometers mounted 
inside the model hull. 
29 
