NO. 3 LANGLEY MEMOIE ON MECHANICAL FLIGHT L99 



lower guy-posts of the aerodrome being represented by wires stretched from 

 the posts. In actual use on the aerodrome LI was proposed to have three main 

 guy-wires running front each of the main cross ribs to the lower guy post, bul 

 in the test, which is now to be described, the wires which would have come near- 

 est the body of the machine were left off to see what effect their removal would 

 have on the wing. 



The weight and dimensions of the wing, as set up, were as follows: Length 

 of the main ribs, 24 feet; length of the cloth covering, 22 feet; width of the 

 cloth covering, 11 feet; total weight, 2!) pounds. The two main ribs (front rib 

 and mid-rib) were solid, 3.5 cm. in diameter at butt, 2.5 cm. in diameter at tip, 

 and tapering from the middle to the tip. There were twelve regular cross-ribs 

 set 50.8 cm. (20 inches) apart, each rib being as above described, 11 feet long, 

 22 mm. outside diameter by 17 mm. inside diameter at the butt, and tapering 

 from where they were attached to the mid-rib to the tip, and each weighing 

 300 grammes. There were two extra cross-ribs, one at the inner end next to 

 the body of the machine and the other at the outer end. These were solid strips 

 of wood 3.8 cm. wide by 1.2 cm. thick, made extra wide and stiff in order to with- 

 stand the strain of stretching the cloth covering. There was also a thin, flat 

 strip at the rear edge, which connected together all the tips of the cross-ril>s, 

 holding them a uniform distance apart, and also serving to fasten the cloth. 

 The main mid-rib was stiffened in a vertical direction by a system of small guy- 

 wires drawn over short guy-posts about 6 inches high. With the wing inverted 

 and fastened in the way above described, a weight of 2 kilogrammes placed at 

 the inner rear corner produced a deflection of 26.7 cm. When the inner rear 

 corner was pulled up by a spring balance until the balance registered 2 kilo- 

 grammes, there was an upward deflection of 41.3 cm. When the main mid-rib 

 was held at the inner end, the pull of 2 kilogrammes, applied to the inner cor- 

 ner as before, caused an upward deflection of 25.4cm. instead of 41.3 cm. This 

 wing was afterwards given a sanding test under a weight of 0.7 pound per 

 square foot. With fine guy-wires fastened from the front of the cross ribs to 

 the tip and drawn just taut, the ribs showed an average deflection of 9 indies at 

 the tip under the above weight. When a small wooden guy-post was added 

 under each of these small guy-wires, the same weight produced an average de- 

 flection of 5 inches at the tip of each rib under the same load. In a previous 

 test of the wing, using hollow cross-ribs 16mm. outside diameter by 10mm. in- 

 side diameter at the butt, and only half as far apart as the later ones, a load 

 of 1 pound per square foot on the wing produced an average deflection of 9 

 inches at the tip of each rib when the cross guy-wires on each rib wore hold 

 up by short guy-posts, but when these short guy-posts were removed, the same 

 load produced a deflection of nearly 25 inches at the tip of each rib. 



