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

5. Metal and commercial aviation i: Henry Ford takes flight,   pp. [96]-113


Page 112

CHAPTER FIVE
airplane parts; losses amounted to more than $5.6 million, not including
depreciation and an unsalable inventory of $1.27 million. If one excludes
operations of the Ford company airline, and includes depreciation and un-
sold inventory, total losses on airplane production amounted to at least
$5 million, or roughly $25,000 for each airplane. Even in robust years, sales
of the Ford trimotors barely covered productions costs; only the year 1929
showed a profit on manufacturing operations alone, due largely to Ford's
practice of excluding unsold inventory from operating costs.4°
The financial problems of Ford's aircraft division were due in part to its
lack of involvement in the military market. The Depression provided the
immediate impetus for Ford's decision to abandon the aircraft business.
However, a number of manufacturers with lesser financial resources sur-
vived the Depression, most notably Douglas, Curtiss-Wright, and Boeing
(as part of United Aircraft and Transport). All of these firms had substantial
military contracts. Ford initially had no interest in producing military air-
craft, although the company did sell twenty-two trimotors to the army and
navy. In 1931, after the collapse of the commercial airplane market, Ford
entered a converted trimotor in an army bomber competition, but the air-
plane's performance was far inferior to the twin-engine Boeing B-9 proto-
type. The modifications to the trimotor interfered with its aerodynamics,
resulting in "semi-dangerous" flying qualities. In addition, the army's trial
board found placement of the armament unacceptable. With no experience
in designing combat aircraft, Ford engineers proved unable to produce a
remotely acceptable military airplane. Despite entreaties from Mayo, neither
the army nor navy was willing to spend money to keep Ford in the airplane
business.41
Both the popular and technical press had heralded Ford's entry into avia-
tion as the start of a new era, but in practice Ford had little direct impact on
the technical course of airplane design. Despite frequent refinements in the
design of the trimotors, Ford did little to change the structural practices first
used by Stout on the 1923 Air Pullman, in particular the use of corrugated
coverings. Corrugation was the easiest way to give compressive strength to
thin sheet metal. In the late 1920s, however, American designers of metal
airplanes began to abandon corrugated coverings in favor of stiffened flat
sheet (see chapter seven). Corrugated skins created manufacturing prob-
lems, being more difficult to shape and attach to the structure than smooth
skins. In addition, corrugated wing coverings were not suited to the faster
airplanes of the early 1930s. To prevent excessive wing drag, the corruga-
tions had to run in the direction of flight, but even so, the corrugated skin
significantly increased drag. The corrugations also prevented the skin from
contributing much strength to the structure. Corrugated sheet has little
strength perpendicular to the corrugations, tending to fold up or expand
like an accordion. A corrugated wing covering could not resist the primary


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