Cockpit
This provides accommodation for two adults
sitting side-by-side. As the money available for this
project was extremely limited, the comfort afforded to
the operators is negligible.Controls
There is a central control lever for all three throttle
cables, a rudder control lever and a main switch for the
fuel supply. All engines have electric self-starts and
ignition warning lights are fitted which serve to give a
visual indication in the event of engine failure.
Skirt
This is a "C" type skirt of heavy-duty
rubberised canvas giving a lift of about
four-and-a-half inches when fully loaded. The
shape of the skirt is restricted by the use of
strong rubber straps secured to the underside of
the hull. |
Sketch
showing section through lift duct.
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Safety
Sheet steel is fitted between the cockpit and the lift
unit. There is adequate guarding of the two propellers.
The guards and the thrust engine mountings are capable of
supporting the craft in an upturned position in the
unlikely event of the craft rolling.
THE
CONSTRUCTION OF THE CRAFT
Work was done outside the corriculum, usually during
lunchtime and after school. It soon became apparent that
a craft of this size could not be built in the existing
workshops. Thus it was that a strange object began to
take the shape of a hovercraft behind the closed curtains
of the school stage. There, under the hot stage lighting,
the boys solved one difficulty after another.
PRELIMINARY
TRIALS AND EXPERIMENTS
Outdoor trials were held frequently throughout the
construction of the craft and contributed greatly to its
successful completion. These trials were observed with
much amusement, and in some cases scepticism, by many
interested pupils. From these trials we were able to
determine the exact position of the lift unit, thrust
unit and cockpit. The balancing of the craft had been so
carefully maintained that it would operate to a limited
degree without a skirt of any description.
Experiments
were carried out using manometers to measure air cushion
pressures under various conditions. Stroboscope
techniques were used to determine fan and propeller
speeds. In addition an investigation of the water
absorbed by various buoyancy materials was carried out in
order to determine the most suitable material on a cost
versus effciciency basis.
THE
FIRST PUBLIC APPEARANCE
Preliminary trials over, the final finishing
touches were quickly undertaken and the craft was ready
for its first public run. One of the senior boys who had
worked on the craft was given the honour of demonstrating
its prowess.
With a
deep roar, the lift engine easily lifted the gross weight
of half a ton and then, very smoothly, the power of the
two 197cc thrust engines sped the craft across the school
fields, to the accompanying applause of the many friends
and parents gathered to watch the maiden run.
Suddenly
disaster loomed up in the shape of a goal post directly
in the path of the oncoming craft. Safety drill had been
carried out in simulated conditions and it was with
confidence that we waited for the craft to slide to a
halt, the lift engine having been cut. It was not to be.
The craft kept on a collision course and the inevitable
happened. With a crash, the work of months wrapped itself
round a very strong 4in. x 3in. upright and pieces of
hovercraft flew off in all directions.
A rush to
the scene confirmed the worst. The goalpost had carved
into the bows for a depth of 3ft. 6in. and had reached
the cockpit. The occupants had escaped with minor shock.
With a wry smile the driver said "It's not so
bad sir, we'll soon fix it". And they did. Back
to the school it was carried, repair work commenced
almost immediately. What drives twelve boys, two members
of staff and several parents to work until midnight
rebuilding a severely damaged hull? Such was their
enthusiasm that by the next day it was clear that the
craft would be ready to compete in the Daily Express Air
Rider competition at Harlow only forty-eight hours after
the crash.
SHOWS
AND DEMONSTRATIONS
As an unofficial entry in the Daily Express Air Rider
competition it was a considerable surprise to find that
the craft was, in every respect, superior in performance
to the Air Riders present, beating the winner's time for
the course by a clear ten minutes. The care and effort
expended by the team had been adequately compensated. We
knew our machine had fulfilled all our expectations.
After this
success the reliability and the appearance of the craft
were improved and we have given many demonstrations at
various schools and shows. The pilots became very
proficient and could manoeuvre the craft easily and
safely.
The craft
was recently demonstrated before the Manchester Regional
Group of Project Technology, under rather unusual
conditions - 8pm on a November night involved obvious
difficulties. Headlights were fitted to the craft and
goalposts indicated by marker beacons. This is possibly
one of the few occasions that a light hovercraft has
performed during the hours of darkness.
FUTURE
DEVELOPMENT
It is proposed to carry out research into improved lift,
through a modified skirt and an increase in lift engine
capacity. In addition it should be possible to improve
our propeller design and the craft still requires
intensive tests over water courses.
Since some
of the boys involved in the construction are now 17 years
old, it is probable that we shall carry out more involved
experiments to test the correlation of theory with
practice in the design of light hovercraft. This is a
subject offering much scope and, judging from the
arguments in amateur hovercraft circles, the answers are
by no means clear!
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