faired fuselage

A Short History of the MIT Human-Powered Hydrofoil Project (1988-1992)

The MIT Human-Powered Hydrofoil project was born in a discussion between Marc Schafer (MIT SM '92) and Bryan Sullivan (MIT SM '??) on a flight from Greece. As members of the Daedalus team, they had just helped set the world record for long distance human-powered flight. A human-powered hydrofoil, they mused, would be a vehicle which any team member could ride, not just the well-toned atheletes. When Marc and Bryan returned to the United States in the summer of 1988, they formulated a proposal and received seed money from the MIT SeaGrant office.

Professor David Gordon Wilson was recruited as the faculty advisor; his work on human-powered hydrofoils had been used as the foundation for the Flying Fish design. Matthew Wall joined the team in the fall of 1988. Professor Mark Drela was soon recruited for his expertise in designing low Reynolds number airfoils and his experience in building Monarch, Daedalus, and other human-powered aircraft.

The first version of the boat used a V-foil and air propellor. The concept of using an air propellor was initially introduced as a joke, but its advantages became apparent as the project progressed. The V-foil part of the design turned out to be less effective.

The DuPont prize was announced early in 1989 and the goals of the project were changed slightly to accomodate the added incentive. Rather than simply building a boat which anyone on the team could ride, team members decided to build the fastest human-powered hydrofoil on the planet.

Construction began in January of 1989. The V-foil design included twin wooden hulls, a 10ft diameter air propellor, a triangular fuselage based loosely on the Daedalus layout, and a surface-piercing V-foil with a 10ft span. Primary test pilot Mark Drela (140 lbs) and heavyweight test pilot Matthew Wall (170 lbs) quickly discovered the ventilation problems inherent to the V-foil design. This version of the boat was not stable in pitch, nor was the pilot able to bring the boat onto the foils under his own power. Tow tests revealed serious ventilation problems with the V-foil design, and the DuPont prize seemed to fade into the distance.

A year passed and the core team of Marc, Bryan, Matthew, and Mark recruited a new group of undergraduates to rebuild the Decavitator. Mark became the new faculty advisor. Ted VanDusen, founder of Composite Engineering, Inc. of West Concord, Massachusetts, granted the team use of his facilities to construct a pair of modified flatwater women's racing kayaks to replace the boxy wooden hulls. The Laboratory for Manufacturing Productivity gave the team access to a three-axis numerically controlled milling machine from which molds for all of the graphite epoxy foils, struts, and control surfaces were made. Using the milling machine reduced fabrication time for a new foil from six months to six days.

As testing on the Charles progressed, the boat became faster and faster and the wing surfaces became smaller and smaller. By the end of the project, eight different main foils and four sets of control surfaces had been built and tested.

In August of 1991 the team was finally ready for its first IHPVA competition in Milwaukee. Gusty crosswinds proved a severe disadvantage to the Decavitator because of its large air propeller, but the team still took sixth place in a field of over twenty.

Upon their return to Boston, the team made many changes including a stiffer frame and still smaller foils. The new high-speed wing measured only 1.75" x 29.5", yet would hold up a person at 20 miles per hour. With construction complete, the team set up its own record course on the Charles in Boston. Mark Drela established the new world record of 18.5 knots (21.3 mph) on October 27, 1991. On the same day, Dava Newman set a new women's world record of 11.41 knots (13.13 mph).

In another effort to break the 20-knot barrier, the team returned to the river in the Fall of 1992, but bad weather and theft of timing equipment allowed only a few trials. Nevertheless, a new women's record of 13.86 knots (15.95 mph) was established by Kjirste Carlson on October 8, 1992.

In December of 1992, news of a new competition in California drove the team to construct an aerodynamic fairing around the pilot, and a new set of foils. Although the fairing reduced drag significantly, it rendered the boat uncontrollable in the light crosswind present at the race and no new records were set.

The DuPont prize of $25,000 was awarded in the spring of 1993 to the Decavitator team. The 20 knot "barrier" remains unbroken. Decavitator is currently hanging in the Museum of Science in Boston, Massachusetts.