Seagull Aircraft, one of the world's first hang glider manufacturers, specialized in curved leading edges as a way of reducing washout (wing twist) without increasing sail tension.
The Wasp Nova was another experimental hang glider of 1975.
One of the Wessex club's best coastal sites then, as now, was Kimmeridge. One sunny day in 1976 the author was being rocked and rolled by thermal turbulence a couple of hundred feet above the hill, the sloping green contrasting with the sea reflecting the blue sky beyond. And rising slowly from the hillside, an all-white wing flown by beginner Peter Robinson. His kite-shaped shadow undulated slowly along the hillside as we passed each other, careful to keep well apart.
A collision was to be avoided at all costs: We carried no emergency parachutes. (Would you be able to unclip and jump out in time?)
The Sport Kites Inc.* Swallowtail was a great improvement on the standard rogallo. Its principle features were judicious removal of sailcloth -- the 'scallop' cut of the trailing edge -- and less billow. Yet it retained the standard rogallo's simplicity.
* Nowadays Wills Wing Inc.
Swallowtails featured in the 1976 movie Sky Riders (filmed in Greece during 1975) starring James Coburn, Robert Culp, Susannah York, and Charles Aznavour (better known as a singer). After filming of the action was complete, the Wills Wing team toured Europe and stopped by in England to win the British Championships at Mere, Wiltshire, in August 1975.
A rather lengthy account of the social ramifications of Sky Riders is down-loadable via the articles menu -- accessible from the main menu.
So began an article by Mike Jerram in the March 1976 edition of Britain's private flying monthly magazine Pilot.