NO. 4 



WIND TUXNEL EXPERIMENTS IN AERODYXAMICS 



65 



different wings. l-"igure ;^2 shows some difference in form for curves 

 M plotted on angle of incidence. It must be borne in mind, how- 

 ever, that the orig-in of these curves is at a greater distance from the 

 center of pressure the farther the wing is swept back. A better idea 

 of the variation in pitching" moment with change in incidence can be 

 ol)tained by plotting the curves with the estimated center of gravity 



Fig. 26. 



of the machine as the origin. Figure 20, Part I of this report, shows 

 the movements of the centers of pressure to be similar for all wings. 

 The conclusion is that sweeping back wings has no effect on the cor- 

 responding derivatives of X, Z, and M, and consequently no effect 

 on longitudinal stability. It is of course to be expected that swept 

 back wings may slightly increase the radius of gyration for pitching 

 and so affect the motion indirectly. Aerodynamically, however, no 

 advantage is to be expected. 

 5 



