Popular Science Monthly 



897 



© Underwood and Underwood 



Thousands of such machines must be made if we are to win the war in the air. Airplanes 

 must be built on the progressive assembling system adopted in automobile plants. We 

 must be prepared soon to make three thousand five hundred airplanes a month 



kind of mechanical paradox. The frame 

 of the wing is in effect a very carefully de- 

 signed, very carefully constructed bridge. 

 There is probably no other structure in the 

 world that is so light and yet so strong. A 

 pilot who flies at a speed of over a hundred 

 miles an hour, who climbs more than six 

 thousand feet in seven minutes, and who 

 makes a sickening drop 

 two miles in the air in 

 order to escape an adver- 

 sary subjects his wings to 

 terrible strains. Cyclones, 

 which are nothing but 

 winds traveling with air- 

 plane velocity, blow down 

 houses and uproot trees, 

 because the houses and 

 the trees are not stiff 

 enough to withstand such 

 enormous pressures. The 

 modern airplane is a 

 storm machine. It forces 

 itself through the air with 

 cyclone speed; which 

 means that it is subjected 

 to exactly the same pres- 

 sures as if it were lashed 

 firmly to the ground in 



© Brown and Dawson 



No iron cross 



for us, but the 

 red, white and blue of Liberty 



the worst Kansas cyclone. Years of re- 

 search and mathematical calculation have 

 taught the airplane builder how to make a 

 wing so strong that it is not likely to snap 

 off like a clay pipestem. 



Where Shall We Get Spruce? 



To make the wings strong, yet light, 

 spruce is used. If we are 

 to build airplanes at the 

 rate of 3,500 a month we 

 must make deep inroads 

 into our forests. There 

 is none too much spruce 

 of the superior kind re- 

 quired for airplane con- 

 struction. It is hard to 

 find good wood. But the 

 task of building wings is 

 further complicated by 

 the fact that although the 

 spruce is bought by ex- 

 perts, fully two-thirds of 

 it is rejected because of 

 its faulty grain or some 

 other defect. 



The building of an air- 

 plane wing is hardly a 

 commercial art. It is 



