NO. .*> LANGLE^ MEMOIB ON MECHANICAL lUCHl 101 



wings 10°, tip angle 20°, the flight partook of the same character, but the ma- 

 chine struck the water clear of the boat. 



The fact that with the CG 10 cm. in advance of the calculated CI' the aero- 

 drome steadily rose in front, seems to indicate that the rule used at that time for 

 calculating the CP (see Chapter II) was not very accurate. This rule was based 

 upon the assumption that the tail, having an area equal to one-third the entire 

 sustaining surface, supported one-third the total weight (expressed by the for- 

 mula CP = — ^— -, where CP,,-,,, and CPtm represent respectively the CP 



of the wings and tail in motion), and that the CP of each surface was one-fifth 

 its width in front of the center of figure. 



December 12. Four days later, the tail had been moved back 21 cm., thus 

 carrying the CG back 7 cm., but the vertical rudder (weighing 105 grammes), 

 for which there was now no room, was taken off, which in a measure counter- 

 acted this change. 



A trial was then made with the wings set at an initial angle of 8° at the 

 root and 20° at the tip. The aerodrome was released with the engines working 

 under a steam pressure of 90 pounds, and soared off horizontally for some dis- 

 tance, when suddenly it swerved to the right as though something on that side 

 hail given out, and turning quite through 180° headed toward the boat, striking 

 the water about 76 feet away. The time of the flight was 4 seconds. 



It was found upon the recovery of the machine that one of the propellers 

 had been twisted through 90°, so that the two were no longer symmetrical. The 

 turning may have been due to this twist or to unequal influence of the wind 

 upon the two wings ; for when I applied the sand test to the wings after return- 

 ing them to Washington, it was found that they deflected so much that the grains 

 would not lie upon them, which, to a great extent, explains the failure to secure 

 a better flight. 



Thus the end of another year had been reached, and what might be called a 

 real flight had not yet been secured. The only progress that seemed to have been 

 made was that the aerodromes were not quite so unmanageable and erratic in 

 their flights as at the beginning of the year, and that it had been demonstrated, 

 at least to the writer's satisfaction, that the power was sufficient for the work to 

 be done. The launching device had been so perfected that it worked satisfac- 

 torily, but the problem of balancing seemed as far from solution as before. 



1895 

 While, for convenience in narrating the progress of the work with the aero- 

 dromes, each year has been treated as a unit, it is, of course, understood that 

 the work itself shows no especial difference between the closing of one year and 

 the beginning of another. Changes winch had important effects were introduced 



