CHAPTER VIII 



HISTORY OF CONSTRUCTION OF SUSTAINING AND GUIDING SUR- 

 FACES OF AERODROMES 4, 5 AND 6 



Introduction- 

 Li some early experiments in 1887 with the small models without motor 

 power, which have not heen particularly described, two pairs of wings, in the 

 same plane, were employed for reasons connected with stability. Afterward, 

 in many of the rubber-driven motor models, which have been described in Chap- 

 ter II, two large front wings were employed and the following pair were di- 

 minished into what may properly be called a tail. This plan was a retrogres- 

 sion in design, and it was pursued by the writer with a pertinacity which was 

 not justified by the results obtained, being used even on the early rubber-driven 

 models. 



In this construction, it will be observed that the flat tail was in fact not 

 only a guiding but a sustaining surface, since it bore its own share of the 

 weight. It was not until a much later date (November, 1895) that the writer 

 returned to his earlier construction of two pairs of wings in the same plane 

 bearing the whole weight of the aerodrome, to which was now added a flat 

 tail, whose function was not to support, but wholly to guide. This was de- 

 veloped into the final construction by the addition of a vertical rudder or 

 rudders. 



The present chapter is not concerned with the history of the earlier at- 

 tempts witli small models, or of those numerous constructions of sustaining sur- 

 faces which were never put to actual trial; nor does it give any description of 

 the experiments which were made in placing one set of surfaces over the other, 

 according to a method suggested in "Experiments in Aerodynamics." 1 



The experiments in " Aerodynamics," and the theoretical considerations 

 given in Chapter V on sustaining surfaces, would never alone have led to the 

 construction which was finally reached, which was largely ihio. to the hard les- 

 sons taught by incessant accident and failure in the field. The present chapter, 

 therefore, should be read in connection not only with the pages of "Aerody- 

 namics," but with Chapters V and IX of this book. 



Tt is to be remembered that, while the center of gravity of the aerodrome 

 could be determined readily and exactly, the center of pressure could be de- 

 termined only approximately in advance of trial in actual flight. The positions 



1 Chapter V. 



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