NO. 3 LANdl.KY MBMOIB ON MECHANICAL PLIGHT 201 



clamp which held it during the tests. The rear portion of the spruce rib pro- 

 jected 5 feet from the clamp, being thus 3.3 times as Long as the quill, and it 

 weighed L20 grammes, the weight for the Larger size having, therefore, increased 

 slightly less than the cube of the length. 



The results of the tests of both the quill and the rib are given in the fol- 

 lowing table. The approximate cross-section of the quill al the poinl of clamp- 

 ing, the middle and the tip are shown in diagrams .1, II and ('. respectively, of 

 Plate 67. The cross-sections of the rib at the corresponding points are shown 

 in diagrams D, E and F. The cross-sections of the quill, enlarged five times, are 

 shown in diagrams A', B' and C. 



Quill from the Remiges of Habpy Eagle. Hollow Spruce Rv... 



Weight. 4 grammes; length, 45 em.; tip, 17 cm. Weight, 120 grammes; length, 153 em.; section, 



above butt when the latter is horizontal. rectangular; tip, 17 cm. above butt. 



Point of Weight 



Defection application Absolute in terms Deflection 



interim of weight in weight in of in terms 



of length. terms of grammes. greatest of length, 



length. length, 



.38 0.39 15. 1.0 .11 



.38 0.445 11.400 0.76 .11 



.38 0.56 7,900 0.53 .11 



.38 0.75 4,000 0.27 .11 



.38 0.95 2,000 0.135 .11 



In each case the unit of length was the portion extending beyond the clamp; 

 the unit of weight, the greatest weight employed to produce the deflection. It 

 should be noted, however, that the relative deflection was quite different in the 

 two comparisons. In the case of the quill the deflection was 17 cm. in 45 cm., or 

 38 per cent; in the case of the rib it was 17 cm. in 153 cm., or 11 per cent. In 

 the case of the rib at the point 0.39 the absolute weight was 15,000 grammes, 

 the relative weight unity and the deflection in terms of length 0.11. While no 

 rigorous comparison can be instituted, since the rib was not deflected nearly as 

 much proportionately as the quill, yet the general inference is that while the 

 rib was not intended to be, and was not as elastic proportionately as the quill, 

 it was probably at least as strong in proportion to its weight. Briefly sum- 

 marizing these results it will be noted that the spruce rib was about 3.3 times 

 the length and 30 times as heavy, while it was 15 times as stiff near the butt and 

 26 times as stiff at the tip, as the quill. 



As this test on the rib for the large wings had apparently shown that the 

 plan of constructing the ribs in the form of a hollow square secured maximum 

 strength for minimum weight, it was decided to construct a few sample ribs 

 after the same plan for the wings of the new quarter-size model of the large 

 aerodrome, and to test these ribs in a similar manner. The following table 

 shows the results of the test on one of these ribs: 



Total length of rib = 80 cm. Curve = 1 in IS. Highest point of curvature = 0.25 from front. 

 Section of rib = 10 mm. X 14 mm. at point of attachment to mid-rib. tapering to 8 mm. X 12 mm. 

 at the front point and to 7 mm. X 2 mm. at the tip. The rib was clamped with the tip projecting 

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