NO. 6 LANGLEY MEMOIE ON MECHANICAL PLIGHT 89 



During the year 1895 but two field-trials were made with the steam aero 



dromes, and neither of these was successful; but a great step forward had 1 n 



taken in the construction, guying and arrangement of the sustaining surfaces. 

 The wings had been made stronger with no increase in weight per unit of area. 

 On the contrary, the ratio of weight of sustaining surfaces to area had been act- 

 ually reduced from 43 to 28 grammes per square foot, so that the surfaces were 

 both lighter and stronger. 



Two longitudinal ribs had taken the place of the single one before used, a 

 second wing clamp had been added to correspond to the midrib, the difficult 

 problem of torsion had been effectually solved, the system of guying greatly im- 

 proved, and it appeared that in the next trial the wings might be expected to 

 bear the weight of the aerodrome without serious distortion. 



1896 



In January, 1 896, two new pairs of wings were designed for No. 6, and in or- 

 der to give a greater efficiency to the rear wings, they were made larger than 

 the front ones, the area of the latter being 22 square feet, and of the former 27 

 square feet, and whereas the width of each wing had formerly been one-third 

 of its length, it was now increased to two-fifths to correspond to those of No. 5. 



The progress made in construction and guying is shown by the fact that 

 when on January 28 one pair of the wings of No. 5 was inverted and sanded, the 

 yielding at the tip was less than 5° greater than at the root, whereas at one time 

 it had been 65°. A similar test applied to a pair of wings of No. 6 on March 4 

 gave even better results, as the yield at the root was but 1° 45', and at the tip 

 2° 30'. 



The successive stages of the development of the wing clamps are shown in 

 Fig. 16. In its final form the front wing clamp, or that which held the main 

 front rib, shown at AB (1896), had adjustable sliding pieces, by means of which 

 the wings could be set at any desired angle of elevation, the wing as a whole re- 

 volving about the rear wing clamp, shown at CD (1896). 



The general system of guying the wings, as shown in Plate 17, had been 

 greatly improved. In the present form a bowsprit and guy-posts firmly at- 

 tached to the midrod furnished points of attachment for the piano wires with 

 which the wings were guyed and held rigidly in place, other wires being stretched 

 across from wing to wing so as to maintain them at a constant diedral angle of 

 about 150°. The clamps by which the guy-posts were attached to the midrod, are 

 shown at EF (Fig. If,). 



In the successful flights of No. 5 on May 6, the completed wings already de- 

 scribed weighed together 1950 grammes (4.29 pounds), and had a total sustain- 

 in- area of 6.4 square metres (68.8 square feet), the flying weight of the aero- 



