Sealegs

Sealegs is an amphibious boat system developed by Sealegs International Ltd of Auckland, New Zealand. Motorised, retractable and steerable wheels are fitted to a rigid-inflatable boat, so it can be driven from storage, down a ramp or beach and into the water with its occupants staying dry. Afloat, the wheels are raised clear of the water and the boat runs as normal. When returning, they are lowered while still in the water, and the boat drives itself up onto land when they touch bottom.

Design

A small air-cooled Honda petrol engine inside the boat drives a hydraulic pump. This powers hydraulic motors in the two rear wheels, giving a land speed of up to about 10 km/h forwards and in reverse. The single front wheel is steered from the boat's steering wheel. At the press of a button all three wheels are raised or lowered hydraulically, like an aircraft undercarriage. In the water an ordinary outboard motor provides propulsion: with a 60 hp Yamaha the early production boats reached about 60 km/h. All components are submersible and suitable for salt water.

Production

The concept was first offered on RIBs of 4-6 m and up to 750 kg. Production began in the first half of 2003 with 4.7 m and 5.9 m models, with other sizes, including barges, built to order. Those boats used a 13 hp Honda engine and 22-inch rear wheels.

All Terrain Amphibious Craft

In April 2005 the company announced the 5.6 m Sealegs All Terrain Amphibious Craft (ATAC), designed to cross estuary mud flats and soft shingle beaches. It has two 31 x 18 inch balloon tyres at the rear and three 21 x 12 inch steerable front wheels, giving a ground pressure lower than a human footprint, and a 425 mm ground clearance. It can climb slopes of over 25 degrees. On land it is driven by a 16 hp Honda V-twin. The hull is 4 mm marine-grade aluminium with four-chamber inflatable tubes, the beam is 2.47 m, and it weighs 890 kg with a 90 hp outboard. It seats four at the centre console and carries 500 kg (six adults) on land or water. Top speed is 60 km/h on water. At the time, Sealegs was also planning an attempt on the record for the fastest English Channel crossing by an amphibious vehicle.