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

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

Page 54

54                                                     CHAPTER THREE
production remained a chimera. Mass production was even more unrealistic
for commercial aircraft. For manufacturers in the 1920s, "quantity produc-
tion" meant "an order for fifty or one hundred machines." Passenger airlines
promised no large market; in 1924 E. P Warner estimated future American
demand for commercial transport aircraft at seventy airplanes per year.
Warner's estimate was actually a bit high. In 1938 the industry produced for
domestic use only fifty-three multiengine airplanes, the dominant type for
airline travel, while domestic air carriers needed a total fleet of only 260
airplanes to serve the largest air travel market in the world. For civil air-
craft, by far the largest market was for small, privately owned, single-engine
models, precisely the types dominated by wood-and-fabric construction.30
Advocates of metal repeatedly invoked fire safety, weight efficiency, and
production costs as arguments in favor of metal, even though practical ex-
perience proved equivocal. But another issue provided the most potent ar-
gument for metal--durability Durability was one of the most frequently
cited advantages of metal. Wood, said Junkers, "is subject to ... fire and
decay, and splinters when breaking; it bursts and warps from the effect of
humidity ... and the glued joints split; finally it is attacked by insects. ...
Metal is free from all such drawbacks."31 Indeed, metals are in general more
durable than wood, but both deteriorate when left unprotected. Wood rots,
steel rusts, and aluminum corrodes. In the 1920s, only practical experience
could determine metal's true advantage in durability ideally through stud-
ies involving comparable wood and metal airplanes operating under similar
conditions. If such studies were ever done, they were never made public. In
any case, practical experience soon demonstrated that duralumin too had
durability problems, problems comparable in severity to those of wood.
In the early postwar years, airplane operators had little information on
durability but soon discovered that heat and humidity were very hard on
wood-and-fabric. Airplane operators quickly recognized that maintenance
varied considerably with climate and type of service. Wood-and-fabric air-
planes deteriorated much faster in tropical than in temperate climates. As
early as 1920, the U.S. Navy found that its wood airplanes in Panama rotted
"very quickly," even when kept in hangars. Colonial airlines in French Gui-
ana and the Belgian Congo became convinced that "all-metal seaplanes are
an absolute necessity in the tropics" due to the warping, rot, and alignment
problems experienced with their wood-and-fabric ships.32
Proponents of duralumin were initially very sanguine about its durabil-
ity33 As the use of duralumin spread, however, reports of corrosion prob-
lems began to accumulate, and by 1925 evidence of an especially insidious
type of corrosion began to appear-intercrystalline embrittlement. In com-
mon types of corrosion, chemical reactions eat away the surface of the metal
while leaving the properties of the underlying material unchanged. Inter-
crystalline embrittlement, on the other hand, produces little change on the

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