Tony Prentice

During the 60's Tony was experimenting with several different flying machines.

The following is an article by him that appeared in a UK magazine

BIRD MEN

TONY PRENTICE WITH HIS LILIENTHAL REPLICA

Flying like a bird, with wings strapped to their shoulders, a dream of many men past and present.

With the advent of powered flight, aircraft have developed away from this dream. The experience of flight is now so insulated that to fly means no more than going by bus or train.

I have endeavored to recapture this dram by returning to the pre-Wright brother’s era, the days of the Bird-man. My main inspiration has come from the German pioneer Otto Lilienthal and his English emulator Percy S, Pilcher. They both conducted their flying experiments during the 1890’s with wings like those of a bird. Examples of these can be seen in the Science Museum. South Kensington.

Lilienthal’s method of flight was to support himself in the center framework of his machine. Then, from the side of a hill, he would run into the wind until the lifting surface sustained him in the air. Control was effected by shifting his body weight and consequently changing the centre of gravity of the glider. Swinging the lower part of his body forwards caused him to dive and increase air speed. To climb he swung backwards and to achieve lateral balance he would swing sideways. This was all very much like riding a three dimensional bicycle, balance being maintained by body movement. Pilcher’s method of launch was often like that of a kite or present day glider, by being towed into the air. Once airborne he would control his machine as did Lilienthal.

By this means both pioneers achieved flights of up to a quarter of a mile and even on occasions gained height in slope lift.

Lilienthal’s flights numbered about 2000 by 1896. In August of that year during a flight, a sudden gust of wind caused his glider to stall and he crashed from 50feet. His spine was broken and a few hours later he died. Had he lived and completed his experiments with control and powered flight he would probably have been before the Wright Brothers in achieving sustained powered flight.

Undaunted by Lilienthal’s death Pilcher continued with his experiments. By 1899 he too was ready to fly a powered machine.  The engine to power this craft he had built in a family works in Westminster. It was a 4h.p. oil engine, although he had calculated that 2 h.p. would be adequate. Before testing this machine Pilcher visited Lord Braye at Stanford Park, Market Harborough, to demonstrate his glider, the ‘Hawk’. The day was wet and gusty and his machine had become soaked with rain. Not wishing to disappoint his audience, Pilcher took off for a short glide. Then he returned to his starting point and took off a second time. He was going well when the tail plane collapsed causing the machine to crash. Pilcher died two days later from injuries he sustained. So, like Lilienthal, he died on the threshold of power flight.  To both these pioneers though, powered flight was not their goal. The idea was to use the power to attain height to where they would be able to soar in the up-currents, as the large birds do and as pilots do today. Many people, like the Wright brothers, followed the example of these two pioneers, but their ambition was powered flight and so ‘Bird-Man’ flight was lost.

My efforts over the last few years have been directed to once again producing the ‘Bird-Man’ glider. I have based my design on those of Lilienthal’s and Pilcher although constructional detail is my own and I have used some modern materials. The wing span is 22ft with an 8ft chord. Overall length of the body and tail is 17ft. The structure is mainly of bamboo with aluminium and plywood parts. Piano wire has been used for the bracing of the wings and standard cable for the strut bracing at the centre. Covering of the wings and tail is of nylon. The total area being about 200sq ft. Small clamps are used to tension the bracing wires and covering. The weight of the whole apparatus is approximately 50lb. It gives a wing loading of about 1lb per sq ft. Compare this with a modern high performance sailplane with a loading of 5lbs per sq ft. This low loading enables slow flight to be achieved, which is necessary for a running take off.

In the summer of 1968 I took the glider to Brasted Hill in Kent for trials. This happens to be only a few miles from Eynsford where Pilcher tried his gliders. After much preparation it was ready for flight. I clambered underneath the wing, through the bracing wires and positioned myself in the framework. Then standing up, the weight of the machine supported by my arms and shoulders, I faced the wind. Nervously I started down the slope, the weight lessening with each stride, until the machine was born by the air. Running faster still unable to stop my feet barely touching until, I felt no longer the ground beneath my feet, but a force beneath my arms lifting.

Gliding a few feet above the ground I made the bottom of the slope. The exultation that I felt at that moment is impossible to describe. I had realised my dreams of flying like a bird.

Carrying the machine back up the hill I arrived breathless, but determine to try again. For the next two weeks I continued with my tests, trying to improve control. Sometimes a gust would cause me to lose balance. On one occasion as I landed the tail was lifted by a gust of wind which threw me upside down. The pain in my leg made me think thatI I had broken it, but it turned out to be only a sprain. The gliders was also damaged, but on the spot repairs were soon carried out.

On the last day of my tests the wind had freshened considerably and with the glider the worse for wear I was wondering whether discretion was the top part of valour. However, I decided to have a last flight and positioned myself at the top of the slope, I waited for a lull as i restrained the glider against the win, but suddenly I was lifted vertically and then thrown over smashing the right wing spars. This time i was unscathed but the glider was now no longer in a fit state to fly. So I packed up and returned to London.

Due to other commitments I was unable to return to my aerial activities until 1971 when I built the glider with modifications. This time I tried it out at Daventh where I now live. At the same time I tried a new design which has a self generating foil shape. It is in a delta plan form and shows as great potential because of its simplicity and low weight.

This year at the South Down Gliding Clubs 50th anniversary (see photograph) i increases my distance, height and control with the delta machine. Certain weaknesses in the structure showed itself and I am now correcting this for further trials.

If this article has aroused anyone’s interest and would like to try “aerial tobogganing” I would be pleased to hear from them.

A R. PRENTICE. T. O. CY/EDI 12.

London Region
                 

Copyright Tony Prentice August 2008

You might like to read an article Tony wrote to accompany a video he made of some of his early flights

 

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