How it works
Hovertravel Ltd: Extracts taken from ‘The Hovercraft. How it Works’ by Alan Blunden. Published by Ladybird 1996 (Out of Print) copyright Ladybird Books Ltd.
What is a hovercraft and how did it begin?
The hovercraft principle had interested many inventors but it was Sir Christopher Cockerell who made it feasible. He wanted to make a vehicle that would move over water on a layer of air. The hovercraft works because fans draw in air from around the craft, slightly increase the pressure of that air and then pump it down underneath the hull. This air is trapped between the craft and the ground. As more air is pumped downwards, the pressure of the air pushing on the underneath of the hovercraft increases. Eventually the pressure of the air is greater that the weight of the craft. A cushion of air is created beneath its hull. The air lifts the hull clear of the surface over which it is travelling.
The 'skirt' around the hovercraft prevents the air from escaping and its bag-and-finger design gives passengers a smoother ride and overcomes the problems of waves that it may encounter as it travels through stormy waters or rough terrain.
Driving a Hovercraft
Hovercraft control is much less positive than that of conventional boats, which have control and propulsion surfaces in the much denser medium of water. Consequently it is more difficult to manoeuvre a hovercraft precisely, relative to a boat or ship. The captain has four main controls at his driving position. The speed of the hovercraft depends on the amount of power being produced by the two propulsion engines and transmitted to the propellers. However, speed can also be controlled by adjusting the height at which the craft hovers.
The steering of the craft is controlled by rudders, which are located in the slipstream behind each propeller. The captain can also use the propellers to change the direction of the craft.
The captain has one other method of control available. Some of the air pressurised by the lift fans is directed upwards, instead of down into the cushion. This air escapes through tubes called bow thrusters, which are fitted on either side of the passenger cabin.