Lehman and Kaplan 



Fig. 6 - Test arrangement 



asymmetry. In this manner, one extension resulted in an appendage extending 

 1/2 propeller diameter below and 3/4 propeller diameter above the propeller 

 center line. Two extensions resulted in an appendage extending 1/2 propeller 

 diameter below and 1 propeller diameter above the propeller center line. Photo- 

 graphs of the appendage, fairings, and dynamic force balance are shown in Figs. 

 7 and 8. This appendage is considered three-dimensional, as the ends are rather 

 far from the tunnel walls. 



Dynamic Calibration of Appendage- Force Sensing System 



In calibrating the appendage force sensing system a constant force was ap- 

 plied to the system by a small electrodynamic shaker monitored by a force gage 

 in a small impedance head. The output from the force sensing element (dynamic 

 strain gage balances) was read on the meter of a Hewlett-Packard wave ana- 

 lyzer.* The wave analyzer readings thus permitted plotting the response of the 



*A capacitor was installed in parallel across the meter terminals to produce a 

 smooth signal. The bandwidth of the analyzer is 7 Hz for 3 dB attenuation. 



176 





