Swallowtail versus Gulp
This page compares the refined Rogallo wings of 1975, using the American Wills Wing Swallowtail as an example, with more elaborate designs, the British Miles Wings Gulp serving as an example. It then covers my own first experimental hang glider.
The highest scoring pilot at the 1975 British Championships was American Bob Wills flying an all-black Sport Kites Inc. Wills Wing Swallowtail. Examining the glider from under its expanse of sailcloth I noticed that the sun highlighted brownish streaks criss-crossing the fabric. Wills explained that the sails of these gliders were originally white (or multicolored in some cases) and they were painted black for an upcoming movie which they had just filmed in Greece. The film was Sky Riders, starring James Coburn, Susannah York, Robert Culp, and Charles Aznavour. It was in cinemas/movie theaters the following year. (See Paint it black–my review of that film.)
Bob Wills was already a household name in Britain and elsewhere because of his eight-hour flight in Hawaii in 1973 and, partly I suspect, because his was an easy name to remember! I overheard people conversing in the high street of my local town: “Did you hear about that Bob Wills flying for eight hours in a hand glider!” (I also thought it was hand glider at first. I am told that the term hang glider means slope glider and it was originated by German aviation pioneer Otto Lilienthal.)
The line to launch on the main competition day in the sunshine of August 1975 consisted of more than a hundred hang gliders and it was hours long. I was next in line behind Bob Wills and his black-painted Swallowtail. Bob was a tall guy, but even so that glider was big. He said it cut through turbulence better than smaller gliders. (His brother Chris, the first US champion, unable to comprehend my first name, called me “Mr. Everhard.”) I did not see Bob’s flight because I was following the launch marshal’s directions.
Watching from a cliff, we could see Bobby must have realized his mistake, because, to our horror, his kite slowly turned back to re-circle the pylon. With his altitude almost gone and the kite far from the finishing gate, I knew he’d lost everything. I stood holding my breath as Bobby somehow eked out a few yards, and then a few more, and, flying literally inch by inch, made it through the gate and saved his win.
The crowd cheered him unreservedly, happy to root for the Yank who’d already become something of a legend.
— from Higher than Eagles, the Tragedy and Triumph of an American Family by Maralys Wills and Chris Wills, 1992 (see my review)
That contrasts with Bob Wills’ more usual spot landing approach, such as at the 1974 U.S. nationals the preceding December:
Champion Bob Wills, on the other hand, would make his final approach much higher and would go from prone to standing and back with his hands high on the down tubes as if walking his kite down a staircase. He would step the glider down by pitching the nose up and down and adjusting from standing to prone flight depending on whether he wanted more or less parasitic body drag.
— by Dan Poynter in the USHGA magazine Ground Skimmer, January 1975
So, how did the Wills Wing Swallowtail, the first major improvement on the standard Rogallo, compare with gliders of more advanced design, particularly the Miles Wings Gulp? The Gulp had superior performance. That is, it was more efficient, gliding at a shallower angle and sinking more slowly even than the Swallowtail. No need for afterthoughts like the so-called sailfeather added to standard Rogallos to prevent luffing dives; it had a proper tailplane for pitch stability. However, according to its pilots, the Gulp was hard to turn and was susceptible to turbulence in the roll axis to a scary extent. In contrast, the Swallowtail was (again, according to its pilots) better behaved than any previous hang glider. It was even resistant to the dreaded luffing dive.
For more about the development of the Swallowtail, see A painted history of hang glider design.
Meanwhile, I was building a world-beating hang glider of my own design. Simpler than the Miles Wings Gulp, but with a larger control frame to accommodate the pilot in a prone harness for less drag. I designed it with pencil and paper and I built it in the back yard and garden, occasionally carrying out strength testing on some parts by hanging a heavy weight (me!) from a tube with the required degree of leverage.
The huge control frame was to accommodate the pilot in a prone position.
The modified harness was OK but, unfortunately, in this configuration the new glider barely rose off the ground before dumping me back to earth.
While I had (and I believe I still have) an intuitive grasp of basic physics, my lack of full understanding of induced drag was evident in this project. Having said that, aerodynamic effects are not as hard to understand as many aerodynamicists would have you believe. Don’t take my word for it:
If anybody ever tells you anything about an aeroplane which is so bloody complicated you can’t understand it, take it from me: it’s all balls.
— R.J. Mitchell, designer of the Supermarine Spitfire (World War 2 fighter aircraft)
So it was back to the drawing board or, rather, to an unheated upstairs room where, over the winter of 1975-6 I sat at my desk, pencil in hand, while wearing so many layers of clothing that, if I went down stairs and back up again, I overheated. The redesigned glider flew better after Roly the sail-maker and I rebuilt it accordingly.
There was pride in man’s conquest of the air. There was the realization that he took life in hand to fly, that in each bolt and wire and wooden strut death lay imprisoned like the bottled genie–waiting for an angled grain or loosened nut to let it out.
— from The Spirit of St. Louis, 1953, by Charles A. Lindbergh, first to fly solo across the Atlantic
The bottled genie escaped from my experimental hang gliders more than once in the following years, but from causes more subtle and complex than mechanical failure. However, I remained unscathed until early summer, 1981.
Flying squad, a short history of the east coast U.S. hang glider manufacturer Sky Sports, which I include here to avoid imparting the impression that Bob Wills and Miles Handley were the only people creating significant developments
Miles Handley photo gallery on British Hang Gliding History
Miles Wing Gulp photos by Don Liddard on flickr