Propeller -Induced Appendage Forces 



10.0 

 8.0 



4.0 

 3.0 



1.0 

 0.8 



0.6 



0.4 

 0.3 



0.2 



0.4 0.6 0.8 



Spacing/Propeller Dia«ieter 



Fig. 32 - Induced force ratio vs spacing ratio for a 

 two-bladed propeller upstream of an appendage, 

 axial measurements, and an appendage angle of 10° 



8. Single-bladed- propeller tests can be used to predict the induced append- 

 age force levels associated with multibladed propellers. This technique can be 

 employed for determining both the axial and transverse appendage forces. Com- 

 parisons have been made between single-bladed and two-, three-, and four-bladed 

 propeller units. This is perhaps one of the more useful unsteady induced force 

 test techniques developed to date. 



9. Introducing an attack angle to an appendage results in both axial and 

 transverse forces for both even- and odd-bladed propellers. 



10. With an appendage attack angle of 10° the induced force ratio associated 

 with a two-bladed propeller approximately doubles for the blade rate harmonic. 

 The value for the second harmonic of the blade rate approaches that for the blade 

 rate harmonic at a 0° appendage attack angle. 



11. With an appendage attack angle of 10° the induced transverse force ratio 

 associated with a three-bladed propeller decreases to about 1/2 the value asso- 

 ciated with the 0° appendage attack angle. 



203 



