Davis and English 



Fig. Z4 - Test setup used in structural tests 



case by Morita in Ref. 15. For example, Fig. 27 shows a comparison of the 

 stresses calculated using the Beam Theory with the measured stresses, vividly 

 illustrating this point. 



Two further points should be mentioned in connection with these stress 

 measurements. First, centrifugal effects have not been considered, but the di- 

 rect stresses from this cause will increase the tensile stresses given in Fig. 

 25. This increase is expected to be small (less than 10 percent of the maximum 

 plotted value) at 70 percent radius, becoming a maximum at the root section. In 

 neither case is it expected to increase the stress level to 40,000 lbf/in2 how- 

 ever. Centrifugal stresses were, of course, considered in the final screw de- 

 sign, as they are of considerable magnitude towards the blade root. The second 

 factor to be considered is the screw diameter, since in the Bras d'Or applica- 

 tion the screw diameter was increased to 48 inches. This effect would then re- 

 duce the stresses in Fig. 25 by about 19 percent assuming the thrust remained 

 at 40,000 Ibf. 



The measurements of the blade deflections indicated that the largest deflec- 

 tions occurred at the outer radii and leading edge positions, as might be ex- 

 pected. The deflection of the sections was such as to reduce the installed face 

 cambers and slightly increase the section incidences. This would be expected 



992 



