Published by the MIT News Office at the Massachusetts Institute of Technology, Cambridge, Mass.
Published by the MIT News Office at the Massachusetts Institute of
Technology, Cambridge, Mass.
DECAVITATOR RUNS Hydrofoil Sets Records on Charles By Charles H. Ball News Office MIT is awaiting official certification of two world speed marks for human-powered watercraft-one for men and one for women-following record- breaking runs by the hydrofoil Decavitator on the Charles River Sunday morning, Oct. 27. In a run that started at 9:18am, Professor Mark Drela, Decavitator's pilot and project faculty advisor, pedaled the hydrofoil to a speed of 18.50 knots (21.27 miles per hour) over a 100-meter (110-yard) course, breaking the previous record of 15.34 knots (17.64 mph) set by a California team. About an hour earlier, Dava J. Newman, an MIT doctoral candidate in aeronautics and astronauts, pushed the hydrofoil to a speed of 11.41 knots (13.12 mph) in the craft's intermediate-speed configuration to establish a record speed for women. Both runs were from a so-called flying start, with the hydrofoil at close to its top speed as it entered the measured course, which is slightly longer than a football field. Although the speed over the course is an average, based, on the elapsed time, it is fairly constant, according to Professor Drela. Official observers witnessed the runs and have forwarded their data to the International Human-Powered Vehicle Association in Buffalo, N.Y., for confirmation as official records. In claiming the record, MIT is leading a race to win a $25,000 prize offered by E.I. DuPont de Nemours & Company. Although Professor Drela's run fell short of the 20-knot (23 mph) requirement for winning the prize outright, he said that whoever holds the record at the end of 1992-when the prize expires-will get it. Professor Drela said he doubted that a 20-knot run was attainable by anyone in the near future. The MIT team will continue to try to improve on its record-breaking performance, he added. Dr. Drela, associate professor of aeronautics and astronautics, was the senior design engineer for MIT's human-powered aircraft, Daedalus, which set several world records on a 72.44-mile flight between the Greek islands of Crete and Santorini in April, 1988. 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. Decavitator's name is a pun, Professor Drela said. 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. Professor Drela's team consists of undergraduates, graduate students and alumni from MIT's Departments of Aeronautics and Astronautics and Mechanical Engineering. The graduate students began working on the project as undergraduates about three years ago and have seen the craft undergo a number of modifications to reach its current level of performance. Team members include Bryan Sullivan, an alumnus who initiated the project, alumni James Thorne, Harold Youngren and Juan Alonso; graduate students Matthew Wall, Marc Schafer, Erik Saarmaa, William Gorgen, Jeff Evernham and Thomas Sorensen; and seniors Thomas Washington, Karl Leeser and Richard Paxson. Sponsors include the MIT Sea Grant Program; the Laboratory of Manufacturing and Productivity, which supplied numerically-controlled milling machine time; the Department of Aeronautics and Astronautics, which supplied lab space and shop time; and Composite Engineering, Inc.,a company that builds racing shells and is owned by an MIT alumnus, Ted Van Dusen.