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Hang Gliding History : Development in Britain of the Flexwing hang glider : Second Generation

Second Generation

For the competition Mere 1975 the Rogallo gliders were separated into two groupings. Class 1 was for gliders of the standard Rogallo type, e.g. Skyhooks 3A; McBroom Argus; Wasp 229 B3. Class 2 was for higher aspect ratio gliders with such refinements as deflexers and battens. These were thought of as high performance Rogallos and were widely regarded as machines for experts only, though probably in truth they were easier to fly, being more responsive to pilot inputs, than the by now outdated standard Rogallo. These came later to be referred to as second generation machines. The Swallowtail glider from America appeared at the Mere meet of 1975 and showed its clear superiority in the hands of Chris and Bob Wills. Naturally pilots wanted to benefit from such sparkling performance so that British manufactures had to take a step forward with their designs. With this demand for greater performance sail technology had to move on from the unsophisticated designs that had appeared to date. Sails on many of the early Rogallos had been made with seams that ran spanwise (Breenwave, Arion). Others ,such as the Hiway and Skyhooks standard Rogallos were chevron cut, that is the seams formed a forward pointing vee. As nose angles and wingspans increased it became more logical to construct sails with chordwise seams and panels. Battens began to appear in these second generation gliders, at first probably more to inhibit sail flap or ripple than to form any aerodynamic function. Designs began to sport one or two battens, mostly arranged near the tips in radial layout. McBroom brought out his Cobra design in 1975 with chordwise seamed panels and 6 chordwise battens. Additionally the design had truncated tips (i.e. 'cut off' ). Hiway too had been experimenting along these lines but eventually put aside the truncated tips and introduced its Cloudbase of 1976 with chevron cut sail and 4 radial battens (chordwise in later models). In general it would seem that truncated tips, unless enhanced by end fins or end plates did nothing to improve either performance or handling of the second generation gliders. Some models also featured some radial shaping of the sail in the area of tips. This radial or round tip, which was braced by battens, largely took over in design terms due to its low weight and therefore low inertia.

It was at this time that deflexers appeared. The deflexer being a post and wire device to stiffen the leading edges against flight loadings. The combination of deflexers and battens gave stability and predictability to the sail and gave some scope to tune the glider by altering the sail shape and therefore lift distribution. The mystery of glider tuning had arrived.

Sail billow which had been a central part or the Rogallo concept, began to be squeezed out of the second generation gliders as the twin cone shape of the early design began to flatten and sprout true wings.

Early Rogallo design, with its very low aspect ratio placed no importance upon the size or shape of the leading edge pocket, which enclosed the wing boom. However, as the wing booms were increasingly moved outward to give increased aspect ratio and sail billow progressively reduced, the size and shape of the leading edge pocket began to impinge upon the design considerations. Some attempts were even made to inflate this pocket in order to produce a better airfoil section though in most designs an increase in the size (width) of the pocket was accepted as the norm,as was some tapering from nose to tip.

With the changing of the sail cut from chevron or spanwise panels the chordwise seaming gave the an opportunity to incorporate integral batten pockets. Batten material at first was mostly plastic electrical wiring conduit which was a cheap but easily broken product. However glass fibre battens soon proved to be both strong and very durable. At this time there was in some quarters a prejudice against preformed battens and indeed there were moves in the competition sector to force Rogallos with preformed battens to enter class 3, which at that time was the rigid wing section.

By the end of 1976 the L/D of production gliders had increased to perhaps 6:1. Naturally some exaggerated claims were made by manufactures in their advertising material as to both performance and handling but not until the event of the third generation were such claims realised.

General Specification of second generation gliders

Aspect ratio 3.5-5.5.

Nose angle 90-100 degrees.

Sail planform Still recognisably a Rogallo but tip chord increased by roach. Occasionally tips truncated. Sail shaping Defined by external wire bracing devices such as deflexers and keel reflex wires.

Keel and leading edges Keel tends to be shorter than leading edges.

Keel pocket fully enclosed and not raised.

Cross tubes Exposed, both one and two-piece.

Sail slackness 2-3.5 degrees billow.

Top rigging Kingpost always.

Battens Flexible battens to support tips.

Pitch stability From keel reflex and a contribution from tips.

Duration of type 1974 to 1976.

Examples Wasp Falcon series, Hiway Cloudbase, Chargus Vega, Birdman Firebird.

Second Generation
Hang Gliding History : Development in Britain of the Flexwing hang glider : Second Generation