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Schatzberg, Eric, 1956- / Wings of wood, wings of metal : culture and technical choice in American airplane materials, 1914-1945
(c1999)

3. Metal and its discontents,   pp. [44]-63


Page 50

CHAPTER THREE
Figure 3.2. Samples of spars tested at Wright Field. Note the buckling failures in the
top flanges of the metal spars at center left. A. S. Niles, "Tests on 61/4 Inch Metal
Spars," Air Corps Technical Report, no. 2895, Oct. 1, 1927, 35, copy in Library of
Congress.
initial results, published in 1927, showed that no metal spar performed as
well as the best wood spars. According to the report, the principal cause of
failure was "the liability of [metal] spars to fail by lateral buckling of the
compression flange. The wood spars did not show the slightest tendency to
buckle." The authors attributed the poor showing of metal not to any inher-
ent deficiency but rather to the designers' lack of experience with metal
construction. Neither did they see any inherent advantage in metal, ascrib-
ing relative merit to the skill of the designer not the material.'8
Some advocates of metal, aware of the buckling problem, believed metal
better suited to large airplanes. Buckling became less serious as airplanes
increased in size, because the buckling strength of thin parts increased with
the cube of thickness. Although this relationship was only dimly perceived
at the time, many proponents of metal were also advocates of large air-
planes. However, no one in the 1920s could predict how big airplanes had
to become before buckling ceased to be a serious concern. Even in 1930, the
largest American passenger airplanes revealed no clear advantage for metal
in terms of weight efficiency19 The historical record presents very little evi-


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