By Everard Cunion, 2001 and 2014
The modern sport of hang gliding is normally associated with sunny California and equally sunny Australia. However, individuals with the right stuff in Britain and other countries were quick to copy the pioneers in the USA and Oz. One early British hang glider manufacturer was Skyhook Sailwings, based in what had been a cotton mill in industrial Lancashire in the north of England.
Skyhook chief engineer Len Gabriels started his aviation career in his teens during World War 2. He flew free flight model aircraft in his time off from working in an aircraft factory. “First they were powered by rubber band motors” he says, “but rubber was scarce during wartime so we used to strip old inner tubes in desperation.”
Changing to tow-launched free-flight gliders, he found that thermals – pockets of rising air – sometimes carried them upwards. “If you were very lucky it would come out of the thermal without having drifted very far from the launch point. Usually however there was a breeze and the model would drift down wind which resulted in a cross country chase after it, sometimes for two or three miles.”
Like a number of individuals who contributed to the technology of hang gliding, Len had little formal engineering education: “World War Two arrived just before I left school at fourteen. I had to go straight into work in an aircraft factory, therefore I didn’t have any academic qualifications. However, I don’t regret this at all. An engineering apprenticeship and four years night school three times each week helped of course.”
Before hang gliders and powered ultralights, Len built his own miniature tape recorders, black-and-white televisions, aero diesel engines, and radio control units.
Len provided most of the photos and information on this page in 2001.
In 1972 I heard about hang gliding which originated in California. I had to have a go. As I couldn’t find anyone who was doing it in the UK I had to design and make my own — based on the meagre information which trickled across from the USA and my own knowledge of aerodynamics. After a few false starts a successful design was produced. Others became interested and as a result I sold hundreds of sets of plans. I supplied materials and eventually got into full manufacture along with a couple of partners.
Among a variety of experimental hang gliders flown at the British Championships held at Mere, Wiltshire, in August 1975, was the Skyhook monoplane.
While experimental hang gliders with rigid sails looked promising, the simpler Rogallo flexwing was what most pilots flew and it continued to be improved. The Wills Wing Swallowtail, made by Sport Kites of California (nowadays known simply as Wills Wing) was the first major improvement over the standard Rogallo and it was widely copied. The Skyhook Cloud 9 was one of the earliest British swallowtail types. It had a 100 degree nose angle when ninety degrees was normal for swallowtails. Like the Skyhook standard Rogallo, it had sail clearance towers — small upright struts on the ends of the crosstubes – to which the upper side flying wires were attached, preventing them from digging into the sail. As well as giving a ‘cleaner’ sail, it allowed a shorter king post. (My research indicates that California manufacturer Pacific Gull was the first to use sail clearance towers.)
The V-shaped hang strap on the Cloud 9 was attached to the keel tube fore and aft of the (virtual) hang point. At the time it was felt by some that, in swallowtail type Rogallos, the ‘feel’ of pitch control was too light. A lower hang point, as used on many standard Rogallos, provided a sort of artificial pitch stability but at the same time made roll control heavier. The Cloud 9 hang strap side-stepped the latter problem. It also provided an easy adjustment of ‘hands off’ airspeed (pitch trim).
The Cloud 9 also featured an innovative control frame that folded without the need to detach any cables. Extraordinarily, the base tube folded in half. Yet in the air, it was safe and solid. Their next wing, the Sunspot of 1977, retained that innovative design. (I flew a Skyhook Sunspot for a couple of years.)
In 1977, Skyhook built a wing with a bowsprit and front rigging instead of crosstubes. A bowsprit-rigged wing lends itself to a tail-first configuration, which is how the Skyhook differed from its contemporary in Britain, the Gryphon (designed by Miles Handley) and, a couple of years later, the Gannet (Bob England) and the Sigma (Ian Grayland).
Why put the tailplane in front of the wing? Firstly, to confer vital pitch stability, the foreplane must be set at a slightly more nose-up angle than the main wing. One result is that the foreplane stalls before the main wing. The foreplane having stalled, losing lift, the glider pitches nose-down (a characteristic of any stable aircraft) thereby preventing the main wing ever from stalling.
Therefore a canard hang glider is, in principle, virtually stall proof. In practice, there are several drawbacks to the canard configuration, not least of which is complexity.
Len Gabriels flew an early powered Skyhook Safari hang glider from London to a field sixty miles short of Paris in 1979. In the photo taken over London, Tower Bridge is visible. (The authorities in France refused Len permission to continue to Paris.)
The propeller shaft lay alongside the back of the keel tube at an angle. The vertical strut in front of the propeller braced the propeller shaft to the keel tube. It also and served as a landing skid and prop guard.
Unfortunately, if you stalled the wing on that configuration of powered hang glider (it was not unique to Skyhook) the high thrust line caused the whole thing to pitch nose-down strongly. It happened to newsman and hang glider pilot Brian Milton (in life-jacket in the photo) – and film of the resulting crash appeared on British television news. Luckily, he landed on top of the inverted wing in a recently ploughed field and he survived. (He was still not fully recovered by the time of the cross-channel flight: He was originally scheduled as the pilot.)
Partly because of that shortcoming, fixing the engine and propeller to the wing was abandoned in favour of mounting it on a three-wheeled buggy behind the pilot’s seat. The buggy – the trike – was attached to the hang glider where in un-powered (gliding) flight the harness is attached.
The Skyhook twin engine contra-rotating propeller power unit solved the problem that, at the time, there were no engines with enough power to get two people into the air, which caused a problem in pilot training.
The Pixie power unit started out as suitable for Britain’s lightly regulated sub 70kg microlight category.
From these beginnings, the modern flex-wing powered ultralight (microlight) evolved.
Skyhook Sailwings continued to develop hang gliders into the 1980s. The Skyhook Gipsy was a popular lightweight, single-surface hang glider.
When it ceased trading in 1997 Skyhook Sailwings was Britain’s longest established hang glider manufacturer. Yet it had always been a part time business. (Len was by that time managing director of a small specialist engineering firm.)
By 2001, Len had retired, but he remained active in a sailing club and looked after their web site. “I can say that I’ve had a very full and interesting working life,” he concludes. “And all because of my hobbies.”
It should be Government policy, both National and local, to encourage all hobbies.
Defying Newton, powered ultralight operations at Newton Peveril in Dorset, England
Flying squad, a short history of the east coast U.S. hang glider manufacturer Sky Sports
The importance of a hobby (Len’s web site)