A hovercraft is an air cushion vehicle (ACV) that flies above the earth's surface on a cushion of air. An engine that provides both the lift cushion and the thrust for forward or reverse movement powers it. It is a true multi-terrain, year-round vehicle that can make the transition from land to water without touching the surface. A Thrust propeller provides forward propulsion and directional control is accomplished via rudders mounted aft of the Thrust Fan.
To properly operate your hovercraft you must become familiar with the machine and all of its components. This helps to build a general understanding of the mechanics and limitations of the craft.
A Hovercraft is a vehicle which travels over any surface on a cushion of air which is trapped in a chamber under the vehicle. This chamber is supplied with air under pressure from an axial 4-blade lift fan. The top and bottom of the chamber is formed by the vehicle bottom and the surface over which the vehicle is traveling respectively. The sides of the chamber are formed by the flexible skirt. The simplest skirt is the "C"¯ skirt or the straight skirt shown in Fig. I.
Figure II shows the peripheral jet type Hovercraft, which traps air by means of a curtain or skirt formed by a jet or stream of fast moving air. This jet of air is aimed down and inward at a 45 degree angle for best efficiency and highest lift.
Experimenting with flexible skirts showed that the lifting efficiency and stability of the craft could be increased by using a bag skirt system. (Fig. IV.) The vehicle could be built to almost any platform shape and is simpler to build because air does not have to be supplied to a jet system all the way around the perimeter of the vehicle. The air could be ducted directly into the bag and the chamber. The pressure in the bag could be equal to or greater than the pressure in the chamber. The greater the bag pressure, the harder the ride over rough surfaces.
With flexible skirts the power required for lift varies from 20 to over 200 lbs. per horsepower and depends on many factors. In general a vehicle that has about 100 to 150 lbs. weight for every horsepower of lift will operate well provided an efficient lift fan and duct are used.
There are different types of hovercraft being produced and used throughout the world. For many centuries man has been traveling over the world's seas at ever increasing speeds. New technologies were introduced in order to make the speed increase possible. Conventional displacement mono-hulls could no longer keep up and multi-hulls and planing hulls were introduced. Even higher speeds were achieved with hydrofoils and air cushion vehicles. The practical maximum speed of all marine craft mentioned so far lies around 100 km/h. The drawback of the recent trend for high-speed marine craft is the increased power requirement and fuel consumption. It is very unlikely that any "conventional" marine craft will be able to operate at much higher speeds with acceptable fuel efficiency. The excessive power requirement of high-speed marine craft is mainly caused by viscous drag; well over 50% of the drag is caused by water friction. The obvious solution is to minimize water contact. This approach works for hydrofoils and hovercraft. The speed of a hovercraft is bounded by the sea state and longitudinal stability considerations.