French champion of pedal power, Stéphane Rousson, is developing a twin-prop waterbike designed to beat a 30-year-old world record for the fastest human-powered watercraft. The first prototype has been built and tested on the water.
The long-standing record was set on October 27, 1991, by the Decavitator team at MIT, with Mark Drela pedaling the craft over a 100-meter course on the Charles River in Boston, and clocking up a best-run speed of 18.5 knots (21.289 mph).
The idea for the project stemmed from a chat between MIT students Marc Schafer and Bryan Sullivan on a flight back from Greece in 1988, who as members of the Daedalus team had helped achieve a world distance record for human-powered flight. A proposal was submitted and seed funding from MIT granted.
Initially meant to be something that anyone could ride for fun, the focus changed with the announcement of the US$25,000 DuPont Prize in 1989 – the goal from then on was to be the fastest. After numerous redesigns and performance tweaks, Drela took his recumbent position at the pedals of the final 22-kg (48.5-lb), 6.1-m-long (20-ft) single-prop hydrofoil design and set the speed record.
The Decavitator team returned to the water once more in late 1992 to try and break the 20-knot barrier, but it wasn't to be. However, no-one else managed to beat the 18.5-knot top speed, and the DuPont Prize went to the MIT team. The record remains unbroken.
Enter Stéphane Rousson, who I first met at the Paris Green Air Show in 2010 where he dominated the exhibition hall at Le Bourget's Musée de l'Air et l'Espace with his Zeppy airship. He also revealed plans for a pedal-powered personal submarine called the Scubster, which subsequently won the Bethesda Innovation Award at the 11th International Submarine Race in 2011 ahead of an unsuccessful crowdfunding attempt.
Mirroring the propulsion system used on his airships, Rousson has elected for a two-prop setup for the Aeroster for improved performance and ultimately higher speeds. In fact, the propellers in the first prototype – which each measure 3 meters (9.8 ft) in diameter – have been "recycled" from the Zeppy itself. They're positioned off-center in relation to the cockpit for improved airflow, though currently don't counter yaw and roll forces, which is on the to-do list along with aero refinements and mass adjustments.
The frame is fashioned from "a mix of recycling material that I have in my garage, like an old carbon bike frame, multilayer plumbing pipes with carbon sock on it," with carbon fiber tubing supporting the props. The Zeppy nacelle has also been reused for the Aeroster prototype, meaning that the pilot adopts an upright stance rather than the recumbent position of MIT's record-setting hydrofoil.
Though this means a high center of gravity and more drag potential, the rider does benefit from improved visibility and more natural balance. Rousson told us that he's looking to improve aero performance in future prototypes by installing a fairing and revised seating.
Each propeller is independent of the other but they both turn at the same speed (about 200 rotations per minute), with maneuvering controlled by adjusting the position of one relative to the other. At this point, a chain connects the crank to the prop drive mechanism, but Rousson is hoping to switch to a lighter, more durable belt as the project moves forward.
The prototype's frame is attached to 4-m-long (13-ft) floats but the aim is to extend that to 6 m (~20 ft) and get the weight down to 3 kg (6.6 lb) per float, plus to install oscillating hydrofoils for better performance.
It's early days for this project, but the prototype has been on the water and speed tests are due to follow over the coming months. Rousson still has a lot of work to do before his record-breaking attempt – including either shedding some pounds to pilot the craft himself or get a lighter rider aboard – and is currently seeking funding partners to help move things forward. In the meantime, the brief video below shows the man himself testing maneuverability.
Source: Stéphane Rousson
