Cetan : The Human Powered Hydrofoil

History

This student project was founded two years ago in an attempt to break the world record for the fastest human powered hydrofoil. The two current records are: The Guinness World Record (Flying Fish, 15 knots) and the International Human Powered Vehicle Association record (Decavitator - MIT, 18.5 knots). Our first-generation hydrofoil vehicle, Cetan, inherited from the tradition of the Flying Fish. The superstructure of the vehicle was composed of large-diameter, thin-wall aluminum tubing and T-joints with a helicopter blade airfoil extending downward that enclosed the drive shaft and culminated in a small marine propeller. At low speeds, two computer-designed carbon-fiber-resin composite displacement hulls provided the buoyancy necessary to support the weight of the rider and the structure. At higher speeds, a pair of underwater wings lifted the hulls out of the water while a pair of smaller, control foils at the bow were used to maintain balance. The team designed and constructed Cetan with two specific goals in mind: minimizing weight and maximizing the aerodynamic efficiency of the entire submerged structure. The life of Cetan ended in June of 1999. The fact that the project failed to meet its goals does not overshadow its achievements. A substantial amount of fundamental information and experience in the details of the manufacturing process have been carried over to the design and construction of our next generation vehicle, Cetan EVO.

Cetan Evo

Between June and October of 1999, the team rethought the fundamental concepts, validated concepts, designed components and subsystems on CAD software, discussed the design, and continued iterations of these steps. Gradually, the next generation vehicle took shape. Based on the team's detailed and painstaking calculations, we confirmed the concept that carefully managed wing-strut and drive shaft-marine-propeller systems plus several creative applications of existing marine systems could generate a drag amount comparable to that of the Decavitator for speeds around 18-19 knots. This is a very difficult thing to achieve in practice considering the fact that submerged propeller and drive shaft require a streamlined, hollow strut that acts as a fairing and a shaft support/guide. This adds more drag because of extra wetted area and frontal cross-section area. However, skin friction and profile drag only account for a small percentage of total drag. Induced drag, or the drag due to lift, is proportional to the weight of the vehicle/driver. In fact, for every additional pound, the drag increases as a cubic function.

In an effort to reduce drag at takeoff, Cetan EVO will feature a mono-hull configuration. The hull, modeled after a 16 foot cruising kayak, will not only provide floatation at low speeds, but also serves as a stress-bearing member. To minimize weight while resisting bending and twisting, a carbon-fiber-resin and Nomex honeycomb sandwich wall structure is incorporated. Other components that will be made of carbon-fiber-resin composite are the seat, wing struts, wings, propeller, stability systems, and monocoque body that bears the lift force, the driver's weight, and the thrust force. The entire vehicle is designed using a safety factor of 1.9, meaning that the maximum material stress is 1.9 times the calculated stress. This figure will increase as the season progresses and the manufacturing process is refined.

Several other noticeable new features of Cetan EVO include a revolutionary stability system and a full driver aerodynamic fairing. During designing and construction, the use of advanced computer design software such as PATRAN, ANSYS, Profoil, X-foil, Unigraphics, etc., and the use of precision machining and model-making techniques such as CNC machining and stereolithography will certainly bring the vehicle to a level never achieved by Cetan. Prototype construction is projected to be finished in May of 2000. Necessary testing, refinement of design, reconstruction, etc. will occur during succesive weeks. A final test run is projected for June of 2000, and the rest will be history!

Team

Come take a look at those who are currently working on Cetan or take a look at those who have come before.

Picture gallery (Coming soon!)