Tony Prentice

THE DREAM OF FLIGHT

The following article accompanied a video made by Tony Prentice and gives an insight as to what he was up to during the middle 60’s to the early 70’s.

 

THE EARLY DAYS----This video was produced from standard 8 cine film shot between 1968 and 1975.
It shows some of the history of the sport of hang gliding in the UK reflecting the independent development to that in the USA and Australia.

Hang gliders first appeared in the 1890’s when the Germans pioneer of flight Otto Lilienthal built a number of gliders using weight shift as the main means of control. Englishman Percy S Pilcher emulated Lilienthal and built his own designs. Chanute in the USA developed the idea further building a biplane hang glider with improvements in aerodynamics and structural strength. He also acted as a clearing house for information passing it on to other pioneers. The Wright brothers were able to benefit from this which enabled them to develop their gliders and eventually a powered machine. The Wright’s discarded the idea of weight shift as being impractical and so the concept was lost in history………

THE FLYING PRENTICE’s-----Like many others I dreamt of being able to fly with my own set of wings.
Main stream gliding was far too restrictive as were other forms of aviation being expensive and difficult for a schoolboy to get into. I went through stages of building models out of balser wood and tissue producing my own designs which flew with varying degrees of success. Radical ideas could be tried and improved or discarded as the R&D dictated. The next stage was to build larger models with stronger materials. Bamboo was chosen at it was cheap, and easily obtained and light weight for its strength.

The first machine was an 8’ octagonal kite that would fly but was not very stable. The next machine was a flat diamond shape with a 17’span. Aerofoil shape was given to the wing by bowing bamboo “ribs” using string from one end to a point along its length. With this device extended jumps could be made from the roof of the pram sheds hanging by our hands from the frame. When it was windy enough we were able to kite up someone a few feet above the ground.

Pictures of Lilienthal and other pioneers were found in aviation books and visits to the Science Museum where both Lilienthal and Pilcher machines were on display. A 6’ span model was built based on the Lilienthal machine and flown as a kite and in free flight. From this model a full size machine was constructed in1964 and some early trials conducted jumping from the pram sheds.

 Details of machines shown in video:-

1) It wasn’t until 1968 that trials took place on the Northdowns, which are shown in the first part of the film. Because of the limitations of the film format and the lack of help to do the filming only the first tentative attempts at flight are shown. Conditions were not ideal with the wind direction across the hill necessitating trying to take off across a gully in the hillside. As full flying speed could not be reached the machine is shown stalling. Later in the trials flights were achieved down the main slope into wind distances up to 100yards. The last flight of the trials was into a much stronger wind where a run was not required and some hovering flights were made. Eventually control was lost and the machine was damaged in a ground loop. Subsequent history: - the machine was rebuilt with some modifications and flew again in the early 70’s before being damaged again.

2) A simpler machine with a self-generating aerofoil based on the Rogallo was built to replace the Lilienthal glider. The idea again came from books showing the Ryan wing and other developments from the NASA space programme. We were blissfully unaware of the adoption of the Rogallo for hang gliding in the USA and Australia. This machine used the same materials and construction methods as the earlier machine but was much easier to build and was lighter. The films show different versions of the design as it got bigger to provide sufficient lift for flight. The main problem was the porosity of the wing covering which allowed too much air through. This problem hindered all the first machines until ripstop nylon was used on machine No4. In hindsight the high porosity of the sails probably saved our lives as any crashes were from low down. A magazine in the USA was known as Low & Slow and you did not fly higher than you were prepared to fall. Hand towing was tried to get the machine into the air and this can be seen in the sequence. Because the bamboo would flex in strong gusts an element of auto stability would occur with excess air spilling out behind the sail. Note: - battens were used in the sail on the later version.After seeing the prototype of Geoff McBroom’s Rogallo at Southdown Gliding Club 50th anniversary meeting on the 3rd September 1972 and of its use of aluminium tube for the frame, I decided to build machine No 3 using aluminium tubing.

3) The sail was cut directly from an old army surplus cargo parachute but it was still too porous. The sail did have battens in the trailing edge to overcome the stretch of the material but with no top rigging to maintain the reflex the glider was divergent. The film shows the glider being flown on the Southdowns and on the Isle of white and was the first to be flown there. Pete Scott who lives on the island showed me around and many of the sites we found are still in use for hang gliding or paragliding. When flying off Wrothham hill a storm front came in with rain and strong squalls. The rain ‘proofed’   the material and with the increases wind speed I found myself at about 300 feet above the hill. I managed to keep control but was pleased to get back on the ground in one piece. It was time to design a more stable and efficient wing.

4) As my brother worked for Trumans (the Beer Company) they sponsored the cost of building the next machine, in return for some publicity shots and to jump off the pier at Selsey in the Bird Man competition held on 21st July 1974, and other hang gliding events. This was done and the children’s swimming arm bands were slid over the cross tube to save the glider from going to the bottom.

The machine flew well and would out perform any of the manufactured wings of the day. It used 1.5in 16 gauge tubing for the main frame and blue rip stop nylon for the sail. Leading edge deflexers were used to limit the bending and maintain the required sail shape.

The film shows it flying at Mill Hill and devils Dyke with no top rigging. This was added later which also improved the ground handling.

The McBroom designed home built of Peter Scott can be seen (red and black sail) flying on the Isle of white its sail had far more billow and in comparison was much slower.

One scene shows us flying in very strong winds at Compton bay with the white tops of the breakers out at sea. It ended with my brother top landing and ground looping breaking it to pieces. It was soon repaired and was flying again in a few days.

3) The Red and Blue machine was designed to fly as slowly as possible. The concept came from the sailing rig which uses a fore sail and a main sail which overlap forming a slot. The airflow is channeled through the slot and helps prevent the mainsail from stalling. The design worked well and very slow flight could be achieved but control was a problem with adverse yaw. I later found out that a similar machine had been tried in the 20’s designed by Reinhold Platz the Fokker aircraft designer.

The design is still under development and hopefully the latest machine will be ready for test flying in 2002. The flying sequence was filmed at Mill Hill and other machines of the day can be seen flying. The orange glider is a Miles Handley design called ‘The Gulp’ and is flown by Johnny Carr.

6)The last sequence is of myself flying over Beachy Head in a Hiway 21 ‘Cloudbase’.

Copyright Tony Prentice August 2008