How Does it Work?

The pedal-powered tailboat simulates the swimming motion of a class of fish called "thunniform swimmers". Sharks, tuna and marlin are thunniform swimmers, and are among the fastest of all fish.

The propulsion fin is the rear-most fin suspended from a carbon-fibre "boom". The boom sweeps, or "heaves", from side to side by pedalling. The foot pedals are located in front of the recumbent-style drivers seat. The rudder, or "pectoral fin", is mounted at the stern of the boat. The pectoral fin is used during steering and braking, and is controlled by the side-mounted joystick.

Thrust is generated as the airfoil-shaped propulsion fin slices edge-wise back and forth through the water, just like a fishes tail. The fin generates lift and "flies" through the water like the tail of a shark, or wing of a bird.

The propulsion fin creates an alternating pattern of clockwise and counterclockwise vortices, or "whirlpools", in it's wake known as a “Reverse Karman Street”. These vortices mesh with each other to produce additional thrust for increased power and efficiency.

For readers more familiar with the principles of aquatic propulsion, the tailboat is designed to swim at Strouhal Numbers between 0.25 and 0.40. The driver has full control over heave amplitude, pedalling cadence, pedal force, rudder position and fin angle of attack while underway.

Key Features

Several key aspects of the tailboat design are novel, proprietary and patent-pending. The following features put the tailboat in a class by itself among human-powered watercraft.

• Replicates the efficient swimming action of a fish.
• Forward and Reverse thrust. NO paddle required.
• Adjustable fin pivot angle and heave amplitude while underway, for maximum power and efficiency at all speeds.
• No continuously-immersed metal parts.
• Precision engineered and built. Expedition-class reliability and ruggedness. Stainless steel fasteners throughout.
• Fins & drive-train mechanism are supported by over-sized, double-sealed, permanently-lubricated, stainless-steel ball bearings for silky-smooth, efficient and reliable operation. Seals are integral with the bearings and require NO maintenance.
• NO part of the propulsion system protrudes through the bottom of the hull, avoiding potential leak points.
• Durable, high-strength carbon fiber fins are mounted on spring-return hinges, automatically retracting upon striking a submerged object.
• Main drive cables are dry, straight and non-bending to avoid crippling fatigue failures. Cable end-fittings are chosen for maximum strength and life.
• Resistant to fouling by weeds.
• Comfortable seat provides full back support. Seat position can be quickly adjusted.
• For anti-theft protection, the propulsion fin and boom can be quickly detached and stored separately from the boat.
• Optional pedal toe clips.
• The fins are designed to act as rudders. Ideal for maneuvering under sail. Sail and outrigger are available as an option.