130 SMITHSONIAN CONTBIBtmONS TO KNOWLEDGE VOL. -t 



from ever building a dynamic flying machine sufficiently large to carry even one 



human being. 2 



However, since strength is a function of material and form rather than 

 weight, it is possible by select inn' proper materials and adopting suitable struc- 

 tural forms to evade to a certain extent this " law of the cube." The whole his- 

 tory of st ructural science has therefore been a series of attempts to find stronger 

 and lighter material and to discover methods of so modifying form as to dis- 

 pense witli all parts of a structure that do not contribute to its strength. So in 

 aerodromics the structural problem has been that of finding materials and forms 

 best suited to the purpose for which they are required, for it does not always 

 follow that either the form or the material best suited for one scale of construc- 

 tion is the most advantageous to employ on a different scale. Nor is even the form 

 or material which gives the greatest strength for the least weight necessarily 

 the best to employ. For the structural problem must necessarily be co-ordinated 

 with those of balancing, propelling, and transporting, and each must, therefore, 

 have its proper attention in the design of the whole machine. 



Many of the general considerations of the design of an aerodrome suffi- 

 ciently large to transport a man were determined during the spring and summer 

 of 1898, when the first actual drawings (Plate 32, Figs. 1, 2 and 3) of the pro- 

 posed machine were made. Starting with the assumption that the Models Nos. 

 5 and (i were capable of transporting a load of approximately ten pounds more 

 than their weight, it was seen that, since the supporting surface of any aero- 

 drome would increase approximately as the square of the linear dimensions, in 

 order to carry a man the aerodrome would need to be approximately four times 

 the linear dimensions of these models. Calculations based on the results accom- 

 plished in the construction of the models indicated that such an aerodrome 

 would need to be equipped with engines developing 24 horse-power. The best 

 that could reasonably be hoped for was that these engines would not weigh over 

 200 pounds, and, therefore, allowing 40 pounds for fuel and fuel tanks, it be- 

 came necessary to bring the weight of frame, supporting surfaces, tail, rudder, 

 propellers and every other accessory within 250 pounds, if the total weight of 

 the machine, including 150 pounds for the aeronaut, was not to exceed 640 

 pounds, or 16 times the combined weight of the model and its load of 10 pounds. 

 Although the problem of constructing the frame, wings and all other parts 

 within the limit of 250 pounds seemed indeed formidable, it was believed that the 

 greatest obstacle in the production of such a machine would be that of securing a 

 sufficiently light and powerful engine to propel it. 



itronomer and mathematician re-affirmed tins opinion as late as 1900 and even 

 stated that man could not hope to construct a flying machine capable of sustaining a weight as 

 great, as our largest birds, not knowing that even at that time the model Aerodromes Nos. 5 and 6 

 had already done more than this. 



