On April 21, Putnam contracted with a subsidiary of General Motors to design, build and test the new vehicle. Three days later, a GM team began putting together a model made of wood, sheet metal and cardboard. Working through a weekend, they finished it on Monday, April 27. They named the project DUKW, based on the GM manufacturing code: D for the model year 1942; U for utility truck, amphibious; K for front-wheel drive; and W for dual rear-driving axles.
Putnam, a yachtsman, asked the naval architectural firm of Sparkman & Stephens to design the hull. Roderick Stephens, known, with his older brother Olin, for winning the 1937 America’s Cup, took on the job. He came up with a welded hull that fit snugly under the chassis of a standard Army truck. It sacrificed not an ounce of the truck’s cargo capacity: it could carry 5,000 pounds or 25 soldiers with gear.
GM engineers redesigned the truck’s rugged transmission so a driver could smoothly shift power from the wheels to a propeller. Even in water, the driver steered normally; when the front wheels turned, so did a rudder at the stern. By June 2, engineers had a pilot model, which they tested on land and, the next day, in a lake near Pontiac, Michigan, with 63 designers and builders on board. In water, the DUKW could go 5 miles per hour; on land its top speed was 50 mph. “She’s better in water than any truck, and she’ll beat any boat on a highway,” Stephens joked.
That summer, he and the engineers worked on getting their DUKWs in a row. But despite a grudging Army order for 2,000 vehicles, there was an “almost total absence of official interest” in the DUKW, according to a project report. “The OSRD was getting nowhere,” says Office of Strategic Services (OSS) veteran Donal McLaughlin.
McLaughlin, now retired and living in a Maryland suburb, had just joined the OSS—the intelligence agency from which the CIA would later emerge—and was assigned to work in secret on a documentary about the DUKW’s capabilities. The film was shown to General Devers and to officers in the Army Corps of Engineers. Devers, Bush later wrote, “was the only man in the Army in an important post who fully saw the [DUKW’s] possibilities.” The film, along with some backstage Pentagon lobbying by the well-connected Putnam and others, managed to keep hope alive. Fearing the amphibians “might sit out the war in some Detroit warehouse,” as Putnam put it, he rededicated himself to championing them through the military bureaucracy.