NO. 4 PIONEER WIND TUNNELS RANDERS-PEHRSON II 



epoch-making paper on "Atmospheric Friction "/' read before the 

 Philosophical Society of Washington, February 27, 1904. 



This paper disclosed for the first time the fact that skin friction 

 is responsible for the major part of the total drag. The tests were 

 made in the wind tunnel on carefully constructed boards up to 16 feet 

 long suspended on the wire balance. 



Tests were also made on various spindle- and fish-shaped bodies, 

 establishing the best form for airship hulls and giving, for the first 

 time, the reason why the now universally accepted torpedo shape is 

 preferable. The resistance of wires, struts, wings, and other airplane 

 parts was also studied. 



The tunnel was also used for instruction at the University, several 

 students taking part in the experiments. Occasionally, special tests 

 were made for other investigators ; for instance. Octave Chanute sent 

 a stufifed buzzard for lift and drag measurements, and Emile Berliner 

 had a monoplane model tested. 



WRIGHT BROTHERS 



The Wright Brothers" gliding experiments at Kitty Hawk in 1901, 

 although they seemed successful to other observers, were very dis- 

 appointing to the Wrights themselves, as the new glider did not at all 

 perform according to their calculations based on the aerodynamic 

 tables of Lilienthal. On returning to Dayton in August, they decided 

 to find out by laboratory methods what was wrong. 



Their first testing machine consisted of a bicycle wheel mounted 

 horizontally on a spar projecting from the front of a bicycle. The 

 relative aerodynamic efficiency of various surfaces was found by 

 mounting them on this wheel, balancing one against the other and 

 riding the bicycle at a fairly constant speed. 



Next they sent the blast from a fan through a square tube and 

 mounted their surfaces as blades on a vane in the stream, balancing a 

 curved surface against a plane surface. 



By the middle of October 1901 a small wind tunnel was completed. 

 It was 16 inches square inside and about 6 feet long, with a glass top. 

 The wind was forced through by a blower fan, and passed through a 



" Atmospheric friction with special reference to aeronautics, pp. 237-276, 

 diagrs., 1904. From Bull. Philos. Soc. Washington, vol. 14, 1904. 



Also printed in England: Atmospheric friction on even surfaces, with 

 commentary note by the Rt. Hon. Lord Rayleigh, F. R. S. Reprinted from the 

 Philos. Mag., July 1904, pp. 58-67, diagrs. 



