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

6. Neglected alternative i: plywood stressed-skin construction,   pp. [114]-134

Page 125

PLYWOOD STRESSED-SKIN CONSTRUCTION                                   125
wood tests were completed in 1928, but the army did not publish the re-
suits. Until the late 1930s, the NACA, the army, and the navy showed no
interest in studying wood stressed-skin structures.30
By 1930 the term stressed-skin construction referred almost exclusively to
metal in the eyes of researchers in federal agencies, universities, and air-
plane companies. In 1929 MIT aeronautical engineering professor Joseph
Newell, formerly of McCook Field, began a study of reinforced plates under
edge compression. This study focused on duralumin, but some plywood
panels were tested. By 1931 the tests indicated that corrugated dural gave
the best weight-to-strength ratio, but also that reinforced plywood was su-
perior to stiffened flat duralumin sheet. Nevertheless, most of Newell's re-
search focused on flat dural sheet, and he did not mention the plywood
results in his journal articles, which gave useful guidelines for designing
metal stressed-skin structures. Newell was one of the few engineers to ex-
press doubts about the wisdom of all-metal construction, making his omis-
sion of the plywood data even more striking.31 Other researchers and de-
signers working with stressed-skin structures did not even consider wood as
an alternative material. When New York University professor Alexander
Klemin polled industry and government engineers in 1930 about stressed-
skin design, both his questions and the answers were framed exclusively in
terms of metal construction.32
Military and civil interest in stressed-skin structures continued to grow in
the early 1930s. In May 1931, the NACA established a temporary subcom-
mittee on monocoque design to oversee research at the Bureau of Standards
and the NACAs Langley Laboratory The subcommittee defined its scope
entirely in terms of metal, claiming that research on stressed-skin structures
was "a result of the present trend toward all-metal airplane construction."
The experimental studies supervised by the subcommittee were almost ex-
clusively conducted with duralumin and stainless steel. Much of the re-
search concerned practical design questions, such as the proper spacing of
rivets.33 Such practical research provided significant benefits to designers of
metal stressed-skin structures, benefits not available to designers of wooden
The limitation of stressed-skin research to metal clearly demonstrates the
power of the progress ideology of metal to promote a particular develop-
mental path. There was absolutely no technical reason to restrict stressed-
skin research to metal; in fact, the shift to stressed-skin structures created
new opportunities for low-density materials like plywood. With their high
densities, metals exacerbated the buckling problems inherent in all thin-
walled structures, a fact easily demonstrated in the 1920s using elemen-
tary equations for buckling strength (see chapter three). Yet if engineers
noticed that stressed-skin construction provided an argument in favor of
wood, they did not think it worthy of mention. A 1927 French report briefly

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