BASIC HOVERCRAFT THEORY
Hovercraft are probably better described as air cushion vehicles. An air cushion vehicle is entirely supported above the surface it is travelling over by a by a cushion of air – no part of the hull structure or propulsion system is in contact with or pierces the surface. The hovercrafts IceHover are using are about 5.5 meters in length and have soft material ‘skirt’ to help retain the air cushion. They are powered by two 4 stroke gasoline engines with total power of 140 hp together, weighs about 1100kg fully loaded, have closed and headed cabin house with a good view and have seats for 6 passengers.
A hovercraft is propelled by a rear-mounted fan or air propeller. Directional control is achieved using rudders placed in the airflow behind the fan or propeller. The supporting air cushion is generated using a fan to force air under the craft through the hull. Hovercraft are used predominantly over water. They are operated in the same areas as other watercraft (estuaries, lakes, inshore coastal areas and rivers). In addition, due to their amphibious ability, they can also be operated over very shallow water, mud, sand covered areas, ice and snow.
HOVERCRAFT AND THE ENVIRONMENT
There is a common erroneous perception that hovercraft are not environment-friendly. That is not the case. Hovercraft are, in fact, more environmentally friendly than other watercraft. Here is why.
On the Surface
Because a hovercraft is riding on a cushion of air (the entire craft rides 300mm above the surface) and has no direct surface contact it can travel over any type of reasonably level surface – including water, land, marsh, mud, grass, etc. The cushion air pressure of IceHover Hovercrafts is up to 70Kg/m2. This is an extremely low-pressure footprint and is an order of magnitude less than any other vehicle or even a human (the pressure is similar to that of a small bird). Due to the very low surface pressure, the hovercraft has virtually no impact on the surface it is travelling over - there is usually no visible indication that a hovercraft has passed over any solid or semi-solid surface. Hovercraft can safely pass over small ground-dwelling animals without causing injury. During normal water operation, a hovercraft rides on top of the water surface rather than in the water. The result is that there is no significant wake or surface water disturbance. The only part of a hovercraft that can touch the surface during normal operation is the lower edge of the cushion retention skirt fitted around the periphery of the craft hull - air leakage from the cushion usually prevents the skirt from pressing down onto the surface.
It should evident from the above section that there can be no sub-surface disturbance to either the water or the sea or river bed from hovercraft use. As a consequence, underwater organisms, fish and mammals are not affected by the passage of a hovercraft. In addition, due to the absence of any significant wake, water bed, bank or shore erosion is non-existent.
Due to the nature of the operation and construction of a hovercraft, the entire fuel and power system is mounted inside or on top of the hull and the engine exhaust is discharged directly to the atmosphere (rather than into the water as with most other watercraft). The potential for accidental leakage of raw or burnt hydrocarbons into the water is virtually non-existent as they are fully contained within the topside hull structure. In addition, the inherent operating efficiency of a hovercraft results in a significantly lower level of atmospheric pollution when compared to all other powered watercraft (around 30-60% reduction in emissions). The reason is that the hovercraft is riding on the surface instead of inside the water and then it does not need to push the water away when sailing. IceHovers Hovercrafts generates zero surface and sub-surface pollution and have levels of air pollution similar to a small road vehicle.
As detailed above, hovercraft use air drive fans or propellers for propulsion. Moving air at speed will, unavoidably, generate some noise. In addition, the engines and exhausts generate some noise. At cruise speed, the noise level is typically 71-76dBA at 25 metres. This noise level is very similar to that generated by a passing car or small van. Because the hovercraft mechanical components are fitted to the top side of the hull and the hull is not in contact with the surface it is travelling over, there is virtually no noise transmitted into or below the surface.
Let us consider a full-scale hoverport. What do you need? Just a flat area that is big enough for the craft to land on and turn around on. You don’t need to dredge anything or excavate huge docks. Compare that with the huge effort you have to go to in order to create somewhere for a conventional vessel even only a small one to berth. It is quite clear that a hoverport can be created with minimal disturbance to the local environment.