Hydrofoil sets world speed record


It's official. MIT's Decavitator has won a $25,000 prize as the world's fastest human-powered hydrofoil.

It was the second such prize won by MIT human-powered craft. In 1984, the Monarch B, a predecessor to the record-breaking Daedalus human-powered airplane, won a $30,000 speed prize offered by a British industrialist.

The new prize was offered by E.I. DuPont de Nemours & Company for the first pedal-powered watercraft to maintain an average speed of 20 knots, or 23 miles per hour, over a measured course slightly longer than a football field.

The MIT craft never reached that speed-its best run over a 100-meter (110-yard) course was a record-setting 18.50 knots, or 21.27 mph, on the Charles River on October 27, 1991-but the contest rules stipulated that the prize was to go to the holder of the world's record at the end of 1992.

Other entries had one last chance to top that mark, and MIT had an opportunity to reach 20 knots, at a final mid-December meet in California. However, the previous record held, according to MIT Professor Mark Drela, Decavitator's pilot and the faculty advisor for the project.

Professor Drela said that a 20-knot run will be difficult in the near future. It has not been decided whether to continue the project at MIT, he said.

Some of the prize money will go to the undergraduates, graduate students and alumni who made up the Decavitator team, he said, and the remainder will go into a fund for similar projects.

Dr. Drela, associate professor of aeronautics and astronautics, was a senior design engineer for Daedalus, which set several world records on a 72.44-mile flight between the Greek islands of Crete and Santorini in 1988. He also did the aerodynamic design for an unmanned lightweight plane, Perseus, built by a private company for the National Aeronautics and Space Administration for the purpose of taking scientific measurements in the upper atmosphere. (See Tech Talk, January 6, 1993.)

The Decavitator, whose propulsion system is similar to that of Daedalus, is powered by bicycle-type pedals that turn a rear-mounted 10-foot air propeller. As it accelerates, the boat enters its intermediate-speed configuration by lifting off its pontoons onto two hydrofoil wings about the size of yardsticks, enabling it to skim over the surface of the water. One of the wings then pivots out of the water, giving the boat its final high-speed configuration.

The 45-pound twin-hulled craft weighs about the same as an average 6-year-old child. It is made entirely of lightweight materials such as thin-walled aluminum tubing (the frame), carbon fiber (the hydrofoils), Kevlar and foam (the propeller) and Nomex/fiberglass (the pontoons).

Dacavitator's name is a pun. It's a coined antonym for cavitation, a phenomenon of hydrodynamics that creates drag on underwater propellers. The air propeller sidesteps the problem-thus, decavitation.

Dr. Drela's team came largely from the departments of aeronautics and astronautics and mechanical engineering. Sponsors included the MIT Sea Grant Program; MIT; the Laboratory for Manufacturing and Productivity; the Department of Aeronautics and Astronautics; the Charles Stark Draper Lab, Inc.; and Composite Engineering, Inc., a company owned by an MIT alumnus, Ted Van Dusen.

A version of this
article appeared in the
January 13, 1993

issue of MIT Tech Talk (Volume
37, Number
18).


Topics: Aeronautical and astronautical engineering, Mechanical engineering

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