190 SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE VOL. 27 



curved surfaces formed of wood. The first of this series of tests, the results 

 of which are given below, was made November 30, 1898, on the superposed wing 

 shown in Plate 37, Figs. 1 and 2. Tt should be noted, however, that when this lest 

 was made the wing was not provided with the stiffening strips or the vertical 

 partitions. 



Weight of wing = 1000 grammes; weight of guy-posts, etc., = 475 grammes; distance of mean 



ci liter of gravity of guy-posts, etc., from pivots of balance arm = one-half distance of CP of wing 



from pivots of balance arm; the wing, therefore, had a lever arm of two to one with reference to 



weight of guy-posts, etc., so that the equivalent weight of guy-posts, etc., = 237 grammes. This gives 



1237 grammes of equivalent load on the wing = 2.73 pounds. Area of wing = 21.85 square feet. 



Therefore load on wing = U.125 pounds per square foot. 



Calculated 

 p . souring 



An*leof ^"r «S?' ™°£/ Drift Drift pSSSd. .^0.5 



table" ift.jS5.ln.). ™l). grammes). (pounds,. per. sec. pou&sfer 



(ft. per sec). 



2 0° Ui7r, 1086 18.1 255 0.561 10.15 36.2 



3 10.0 luio 16.85 255 0.561 9.47 33.7 

 5 ' ° 95 %d 16.0 255 0.561 s.its 32.0 



|,,n 7.75 783 13.0 255 0.561 7.3 26.0 



The very interesting phenomenon was noted in this test thai the " drift " 

 or resistance of the wing seemed to remain unchanged at soaring speed at dif- 

 ferent angles of elevation. It is hardly probable that this result is accurate, 

 for the " balance arm " undoubtedly twisted under the action of the wing, and 

 this caused it to strain on its pivots, and thus, to a certain extent, falsify the 

 record as to drift. 



A test of a single-tier wing at different angles of elevation was made 

 on December 6, 1898. This wing was nearly the same as those used in actual 

 flights of Aerodromes Nos. 5 and 6 in May and November, 1896, the wing be- 

 ing of the same width fore and aft, but somewhat shorter. The actual wing 

 was a little too long to permit its being used on the whirling-table in the lim- 

 ited space of the shop. 



Weighl of wing = 420 grammes; weight of guy-posts, etc., = 320 grammes; equivalent weight of 

 guy posts, etc., = 150 grammes applied mi the wing. Therefore, total load on wing = 570 grammes. 

 Area of wing = 11.2 square Eee1 : equivalent load on wing = 0.112 pounds per square foot. 



Calculated 

 .. . Boaring 



Angle of R 7«i OD8 ^ent^/of 1 ™° p f/ Drift Drill pounds *•£„ 



*W™ ( r,.,:.r n n,i„.l. "''• , ^""""- S) - tP ° Unde) - "If? ' ."-'".V"' 



(ft. per see.). 



2 11 6 1195 19.9 210 162 9.2 42.1 



9.75 L005 L6.7 157 0.345 5.77 35.3 



5 0- 8.25 850 14.2 133 0.293 1.16 30.0 



[00 6 75 695 11.6 129 0.284 3.29 24.5 



r:: , 6.0 618 L0.3 12!) 0.284 2.92 21.8 



Tn this test it is to be noted that the " drift," or resistance, while consid- 

 erably -renter at soaring speed for 2 degrees than for 5 degrees, remains prae 

 tically the same between 5 degrees and V_ M , degrees. Comparing it with the 

 preceding test with the superposed wing, it is seen that at soaring speed at an 

 angle of L0 degrees, the single-tier wing having a load of 0.112 pounds per 



