 The Hovercraft Principle: How does a hovercraft work?
A hovercraft is an amphibious vehicle that is supported by a
cushion of slightly pressurized air. Although often seen as
a mysterious, even bizarre mode of transportation, it is conceptually
quite simple. To understand how hovercraft work, it is necessary
to realize that the dynamics are more closely related to aircraft
than to boats or automobiles. As a member of the family of air
cushion vehicles (ACVs) or ground effect machines, which includes
wing-in-ground-effect or ram wings, surface effect ships, sidewall
hovercraft, and surface skimmers, hovercraft, are the amphibious
member of the air cushion vehicle family. They are the most
novel among vehicles that are supported by pressurized air.
Refer to the illustration below as you read about how hovercraft
actually function.
Hovercraft float on a cushion of air that has been forced
under the craft by a fan. This causes the craft to rise or
lift. The amount of lift can range from 6" to 108" (152mm
to 2,743mm) depending on the size of the craft. The amount
of total weight that a hovercraft can raise is equal to cushion
pressure multiplied by the area of the hovercraft. To make
the craft function more efficiently, it is essential to limit
the cushion air from escaping, so the air is contained by
the use of what is called a skirt. Fashioned from fabric,
which allows a deep cushion or clearance of obstacles, hovercraft
skirts vary in style ranging from bags to cells (jupes) to
separate fingered sections called segments. Most Neoteric
hovercraft utilize the segmented skirt system because each
segment can deflect individually when passing over bumps so
that very little lift air is lost on uneven terrain.
Once "lifted" or "on cushion", thrust must be created to
move the hovercraft forward. With many craft, this is generated
by a separate engine from the one used to create the lift,
but with some, the same engine is used for both. As the diagram
above indicates, the fan-generated air stream is split so
that part of the air is directed under the hull for lift,
while most of it is used for thrust.
Now that the hovercraft has lift and thrust, it must be steered
safely. This is achieved through the use of a system of rudders
behind the fan, controlled by handlebars up front. Steering
can also be controlled by the use of body weight displacement...a
skill which is achieved after practice. As an option, Neoteric
hovercraft offer patented, reverse thrust buckets as another
means of control. This is the only system available today
that enables the driver to reverse at speed, to maintain cushion
at speed, to regulate speed going downwind, to hover while
stationary and to brake (a must on ice).
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