NO. 



LANtil.KY MEMOIB ON MECHANICAL FLIGHT 20!! 



the pith showed a slightly less deflection than the one with it, it happening 

 probably that the wood in one case was a little stiller than in the other, al- 

 though they were carefully selected to be as nearly alike as possible. The rib 

 with the pith in it weighed 34 grammes and the one without it weighed 30 

 grammes. It was inferred from this test that the placing of a light pithy ma 

 terial in the interior of the ribs would have no good effect, and would aot only 

 add weight, but also complicate the construction. The reason for making this 

 test with pith in one of the ribs was that it was thought probable that the rib 

 flattened out somewhat when it was deflected under a load, and that the pith 

 stiffened with the glue with which it was fastened in, might lessen this. 



As the cross-rib described above, which was tested on October 23, 1899, 

 seemed in every way suited for use in the wings of the large aerodrome, a emu 

 plete wing equipped with similar ribs but of slightly changed dimensions, as 

 shown in Plate 66, Fig. 5, was immediately constructed. As previous tests had 

 shown that the wing covering did not "flute " or " pocket " to any considerable 

 extent even when the ribs were as much as thirty inches apart, only ten cross- 

 ribs were used in this wing. The eight intermediate cross-ribs were of the 

 form described above, but the ribs at either end of the wing were made of a 

 larger cross-section and otherwise stiffened in order to resist the strain of the, 

 tightly stretched cloth covering. 



On April 13, 1900, a final sanding test was made on this win-, guyed in a 

 manner similar to that used in the aerodrome, in which the following results 

 were obtained: 



Sanding Test of Labge Wing. 



Area, 260 sq. ft.: weight of wing, 29 pounds: weight of sand on wing, 231 pounds; total 

 weight supported by wing, 260 pounds, or one pound per square foot. 



Deflection of cross-ribs, numbering from inner edge to extreme outer edge of wing— 



„ ., Deflection. 



Number of rib. Inches. 



1 (Heavy end rib) 5.5 



9 9.5 



3 11.75 



'! 12.25 



5 



12.5 



G 12.75 



7 12.9 



S '.'.'.'.'.'.'.'.'.'.'.'. 130 



9 120 



10 (Heavy end rib) 9 -" a 



The weight of sand put on the win-- in this test was 1.5 times as great as 

 the pressure which at this time it was expected would be imposed upon it in 

 flight, and was in fact 1.2 times as great as the normal pressure when support- 

 ing the aerodrome as finally constructed. Even under this weight the greatest 

 deflection noted in terms of the total length of the rib was less than 0.10, show- 

 ing that the elastic limit of the rib was far from being reached. 



