Kenneth S. M. Davidson

Kenneth S. M. Davidson
Born	Kenneth Seymour Moorhead Davidson
Died	1958 (1959)
Citizenship	American
Known for	Founding the Experimental Towing Tank (later renamed the Davidson Laboratory); pioneering small-scale model testing of sailing yachts; tank testing of the Ranger for the 1937 America's Cup
Scientific career
Fields	Mechanical engineering, experimental hydrodynamics, naval architecture
Workplaces	Stevens Institute of Technology

Kenneth Seymour Moorhead Davidson (died 1958) was an American mechanical engineer and professor at the Stevens Institute of Technology in Hoboken, New Jersey. He is recognized as a pioneer of experimental hydrodynamics and small-scale model testing for naval architecture, and founded the facility at Stevens that opened in 1935 as the Experimental Towing Tank and was renamed the Davidson Laboratory in his honor in 1959.

Career at Stevens

Early model testing, 1931 to 1935

Davidson joined the Stevens faculty around 1930 as a professor of mechanical engineering with a personal interest in sailing. In May 1931 he began running small-scale model tests of marine vessels in the Walker Gymnasium swimming pool on the Stevens campus, working after the pool closed for the day. At the time, only two other towing tank facilities for evaluating scale models of maritime vessels existed in the United States.

In 1933 Davidson began a collaboration with the yacht designer Olin J. Stephens II. Stephens and his brother Roderick made full-scale measurements aboard the sloop Gimcrack that Davidson then analyzed to derive aerodynamic force coefficients for sails, providing the link between model-scale hydrodynamic measurements and full-scale sailing performance. The pool experiments succeeded well enough that Stevens approved the construction of a dedicated towing tank, which opened on the Hoboken campus in 1935. The tank, known as Tank 1, measured 101 feet long, with a semi-circular cross-section about 9 feet wide and 4.5 feet deep, and was used primarily to evaluate yacht designs.

The Ranger and the America's Cup, 1936 to 1939

In April 1936 the new towing tank became the first facility in the United States used to design and test a racing yacht for the America's Cup. The J-class sloop Ranger, a joint design effort by Starling Burgess and Olin Stephens for the syndicate of Harold S. Vanderbilt, was selected after a competitive series of tank tests of four candidate hulls run under Davidson's direction. Ranger won the 1937 America's Cup over the British challenger Endeavour II by four races to none. Davidson published his early findings on the modeling of windward sailing performance, including the relationship between wind speed and sail force and the lift-to-drag ratio of the rig, in a 1936 paper, Some Experimental Studies of the Sailing Yacht.

The success of the Ranger work brought wider attention to Davidson's group, and in the years that followed the tank was used to test a broader range of vessels, including steamships and ferries.

Wartime work, 1942 to 1945

During World War II the work at Stevens was largely redirected to support the United States war effort. Davidson submitted a proposal to the National Defense Research Committee of the Office of Scientific Research and Development for a second basin capable of testing the maneuvering of vessels, motivated in part by U-boat attacks on Allied merchant shipping. Tank 2, completed in June 1942 on Hudson Street at the western edge of the Stevens campus, was the world's first indoor maneuvering basin.

A third facility, Tank 3, was added in 1944 to meet a growing volume of work on seaplane hull dynamics for the United States Navy's Bureau of Aeronautics. By 1944 seaplane hull work accounted for a substantial share of the laboratory's activity, and the staff had expanded considerably to keep up with continuous around-the-clock testing.

Death and legacy

Davidson died in 1958. In 1959 the Experimental Towing Tank was rededicated as the Davidson Laboratory in his honor, and continues to operate at Stevens as a center for experimental marine hydrodynamics research. Also in 1959, the Society of Naval Architects and Marine Engineers established the Dr. Kenneth S. M. Davidson Medal, awarded for outstanding scientific accomplishment in ship research; eligibility is not restricted to society members. SNAME has counted Davidson among the leading figures of the society's twentieth-century history.

The collaboration between Davidson and Olin Stephens is widely credited as the point at which yacht design moved from an art rooted in observation and intuition toward a quantitative engineering discipline based on tank testing.

Further reading

• Bruno, Michael S. Davidson Laboratory and the Experimental Towing Tank: The History of Towing Tank Research at Stevens. (held in the TU Delft Repository).
• Clark, Geoffrey W. History of Stevens Institute of Technology: A Record of Broad-Based Curricula and Technogenesis, 1870 to 2000. Jensen/Daniels, 2000. ISBN 1-893032-24-8.