Hovercraft and the Environment
What does the future hold for hovercraft? A brief article on what to expect from Airlift Hovercraft
For any vehicle to operate economically the drag, or resistance to motion, must be kept to a minimum. On water, the majority of drag arises from the motion of the vessels hull through the water; therefore we can reduce drag and consequentially propulsive power by minimising hull contact. The hovercraft achieves this by using low-pressure air to form an air cushion underneath it, thus actually lifting the hull clear of the water. In addition, by using air propulsion to generate forward movement, the hovercraft becomes amphibious, and able to traverse land, soft terrain or water.
Being amphibious, the hovercraft can use direct routes across sandbanks, marshes and flats, with no loss of speed or comfort. Environmentally disruptive channel dredging becomes unnecessary, whilst rivers and tidal estuaries present no problem for the passage of the vessel. Previously inaccessible areas may be accessed economically with little or no impact on their environment.
Damage to the shore environment, such as beaches, mudflats and vegetation is virtually nil because of the hovercraft’s low pressure “footprint”. For example, the average human being when standing on a beach exerts a pressure of some 3lbs per square inch underfoot, rising to 25lbs per square inch when walking. The average hovercraft by comparison, exerts a pressure of approximately 1/3lb per square inch on the surface regardless of speed. This “footprint” pressure is less than that of a seagull standing on one leg!
All Airlift Hovercraft are fully amphibious and create virtually no under water noise, just atmospheric noise levels that would be typical of a diesel truck or bus. The fact that there are no underwater protrusions or propellers eliminates the usual thrashing noise signature associated with conventional propeller driven craft, as well as negating any possible seabed erosion when operating in shallow waters. It therefore becomes obvious that fish and other marine life are in no way affected. This has been confirmed by independent scientific tests. The major noise factor with any hovercraft is the propeller noise, which in any case is largely directional in characteristic. Airlift Hovercraft’s hovercraft propulsion propellers have been designed with low tip speed to minimise atmospheric noise.
All AirLift Hovercraft’s hovercraft hulls are a “sealed unit’. This means that any accidental fluid discharges or leaks are fully contained within the hull structure, remaining there to be pumped out at an appropriate shore facility. There is no exhaust discharge into the water as with most conventional watercraft, thus eliminating the pollution of the marine environment by oil and fuel particles, particularly prevalent with outboard motor usage. Atmospheric pollution is also considerably less because of the inherent fuel efficiency of the modern four-stroke machinery utilised, as opposed to the very large percentage of marine propulsion units, which still utilise the two-stroke principle and discharge unburned oil into the water. In addition, because of the low friction with the surface, and subsequently low power requirements, the hovercraft is in itself a fuel-efficient mode of transport, thus lessening the pollution of the atmosphere even more. For example a fully loaded six-person hovercraft burns less fuel per hour than a typical jet ski, it does not pollute the water and does not disturb the bottom in shallow areas that many fish rely upon for food and breeding.
The wake created by the passage of a hovercraft is minimal, ensuring that riverbank erosion and damage to foreshore by the waves created is virtually nil. A study in the United Kingdom concluded that the passage of hovercraft over inter-tidal areas caused no damage to sea grasses or invertebrates. It was also noted that bird life rapidly adjusted to the presence of hovercraft. This has been confirmed on the Gold Coast in Australia, where a commercial operator passed over the same area of beach many times a day for more than four years without any affect to the ‘Yabbie’ population actually living in the sands directly under the flight path.