84 SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE VOL. 27 



essarily heavy. This suspicion was a correct one, though the lull extent of the 

 evil was not yet surmised. 



In the light of subsequent experiment it may now lie confidently stated that 

 the trouble was with the wings, which at the moment after launching were flexed 

 wholly out of the shape which they were designed to have, and which they re- 

 tained up to that critical moment. 



Alter returning to Washington, one of the wings was inverted, and a quan- 

 tity of sand, equal in weight to the pressure upon the wing in flight, was added, 

 under which the yielding at the tip amounted to 65°, or from +20 c to —45°, 

 showing that the wings were entirely too weak to sustain the aerodrome. 



In speaking of the efforts to strengthen the wings, it must be constantly 

 remembered that this could hardly he done in any way which did not involve 

 increased weight; that is, it could hardly be done at all, since increased weight 

 was forbidden. 



The first attempt at systematic guying was made on October 27. As shown 

 in Fig. B, Plate 16, two guy-posts extending beneath the midrod were con- 

 nected by guy-wires with the outer extremities of the wing, by means of which 

 it was sought to hold the wing in place and prevent its extremity from twist- 

 ing upward, while a third wire connecting with the bowsprit prevented its mov- 

 ing backward. In addition, two aluminum wires, stretched across above from 

 wing to wing, kept the lower guys tight. 



On October 27, Aerodrome No. 5, equipped with large new wings and tail, 

 having a combined area of 3.7 square metres (40 sq. ft.), the wings being each 

 (!4 cm. x 102 cm. (2."). 25 in. X 75.75 in.), turned sharply and completely round, ap- 

 parently through some internal current of the main wind against which it was 

 advancing. Owing to this almost instantaneous turn, it lost headway and came 

 down. This led to the subsequent construction and use of a much larger verti- 

 cal rudder, intended to prevent in future any such sudden pivoting and conse 

 quent loss of momentum. The wings showed a tendency to "pocket"" and 

 bag, which indicated some serious fault in their construction. 



As a result of these experiments, it was decided on October 29 to attempt 

 to make the wings stiller (though their weight was almost prohibitory), by in- 

 serting more cross-pieces, cross-pinning and guying them so as to make them 

 more rigid as a whole, and less liable to pocket. 



At this time an automatic device in the form of a sliding tail was designed, 

 which it was thought would cause the center of pressure to move backward 

 when the aerodrome reared, and forward when it plunged downward, but the 

 device, though afterward constructed, was never brought to trial in the field. 



Aerodrome No. 5, equipped with a new set of winij's similar to those \isi'<\ 



" Pocketing " is a form of distortion in which the canvas or silk bass locally in nnmerous places 

 In tween the cross-ribs. 



