NZ Hang Gliding History, part 2

Of Lancers and Sharks

GrAeme bIrd CONtINueS WItH pArt 2 OF tHe StOrY OF HANG GlIder deSIGN IN NeW ZeAlANd IN tHe 1970s ANd 1980s

Double Surface

Early in 1980 the French hang gliding company La mouette introduced the Atlas, a 30% double surface design with innovative pre-formed aluminium tube ribs that clearly defined the airfoil shape of the sail.

The result was a huge improvement in sink rate and glide ratio over the then single surface gliders with flexible ribs such as the Lancer IV. The Atlas dominated the circuit that summer until Ultralight Products (UP) a California based company, released the Comet.

UP moved what the Atlas had started forward a quantum level. Now the wing was 65% double surface with the completely enclosed cross bars eliminating a major source of drag. The Comet’s sink rate was another jump ahead as was its glide ratio and performance at speed. If that was not enough, UP also created a novel crossbar attachment that allowed the keel and pilot’s hang point to move ether side of the wing’s centre line thereby giving the pilot much more leverage for improved roll control, something that made the relatively taut wing flyable.

Within months the Lancer IV was no longer relevant. Pacific Kites had changed hands and US sailmaker Bob Schutte and friends released the Vampire, a second generation Comet, to the New Zealand market for which Flight Sails had no answer.

My brother Warren had countered with a glider called the Sabre. It however did not work as hoped, it was all new territory at this point. I realised that we had to think further ahead of the Comet concept to get back into the game. After conferring with Murray Ross, one of New Zealand’s leading sailmakers, a plan was born.

We decided to go to a near 100% double surface wing with ribs in the lower and upper surfaces to better sail control sail shape. We also chose to enclose the keel as well as the cross bar for further drag reduction. The nose angle was increased significantly from the Lancer, and we moved as others had to pre shaped aluminium tube ribs for the upper surface.

I wanted the upper surface of the sail to fly in its own right, with the lower surface to do its job separately. The upper surface was attached to the leading edge with small pockets at each batten, so it did not rely on the lower surface to determine its fit during flight.

I had noticed two things about double surface flexible wings from a

Above; A good shot of the Shark under surface

Below left; Prototype Shark being test flown by Warren

Below; A Pacific Kites Vampyre

Above; Pete James at the Kaimai Range Right: View of surfaces in flight

prototype some years earlier. Firstly the upper and lower surfaces moved separately to each other when in flight and secondly due to wing twist, the outer lower wing section inverted at speed causing the lower surface to suck away from the upper surface creating a high drag tip section. To get around these issues the lower surface was stand alone and fully ribbed. The trailing edge of the lower surface was not attached to the upper surface at all, instead a web running parallel to and inboard from the trailing edge, attached both surfaces and ran from the keel to about 3/4 span. This allowed each surface to float in relation to each other.

In the tip region the lower surface was not attached to the upper surface except for a strap that picked up the tip batten of the lower surface allowing it to move separately to but not away from the upper surface. We put a lot of attention into pitch stability and added an aluminium tube to the upper surface parallel to and near the trailing edge that allowed for a single blow-down tube to support two battens in the outer wing section.

As there was no extended keel pocket anymore, we moved the inverted dive recovery lines that ran from the top of the kingpost further outboard for greater effect. The lack of any vertical surface on the Shark bothered me at the time, therefore we raked the kingpost slightly and added a triangle shaped fin, from whence came the name. Sharks and Vampires March ‘81

At this time North Island pilots had polarised into two camps, the Pacific Kites Vampire pilots and those who flew Flight Sails gliders. The Vampires had been taking names for some months, so the Shark could not come soon enough. First test flights went well, then first blood. We turned up at the upper NW take-off at Maori Bay in a 15-20 knot breeze, to find Bob Schutte flying a Vampire.

Initially feeling out sink rate we both went for height with similar results. Then came performance at speed with a race out to sea. With control bars to our knees the Shark headed to the horizon, and surprisingly the Vampire dropped at high speed to the tree tops below? It took awhile for what had happened to sink in and after a few more flights it became clear as to why the gliders were so different in this way.

The sails of the Comet/Vampire type gliders had very little shape cut into them, relying on the preformed aluminium ribs to create the airfoil, and a curve cut into the leading edge of the sail to match a given leading edge bend. As a result even though the sail was taut on the frame, it was sensitive to changes in leading edge flex caused by increased load. The higher the flight speed, the higher the leading edge flex, the looser the trailing edge of the sail (most noticeable in the tip region) leaving a smaller portion of the wing producing lift, allowing steep, fast and spectacular dives, but at the expense of high speed glide performance. The plus side of this glider configuration was it helped the Vampires handling.

The Shark on the other hand, had a lot of shape cut into the sail at each batten. When the leading edge flexed at speed, the heavily shaped sail lost little trailing edge tension, resulting in a wing that retained much of its efficiency at speed. Not as good for beating up take-offs, but amazing for going places. This sail stability however did make the Shark a little stiffer to fly. August ‘81

Every flight over the next few months was a battle for hearts and minds of the New Zealand pilot. My job was to out fly the Vampires every time we met in order to generate sales. This pressure had the unforeseen benefit of honing my flying skills so as part of the New Zealand team I went on to win the Class 5 of the World Champions in Beppu Japan with the Shark. On the light days the events were very competitive, however whenever conditions allowed time and distance events the Shark was phenomenal, just point and shoot.

A week later back in New Zealand I fractured my neck test flying when I shouldn’t have been, which slowed down further development on the Shark. Fortunately during this time Warren was making hay selling Sharks locally and overseas. Our main focus became to improve the Sharks handling, so to make it more appealing to a wider range of pilots. This was not easy as the design features that made the Shark great were also its achilles heel in handing, and we could not afford to go back to beginning.

I tried a smaller fully 100% double surface version by cutting the upper surface back to the lower surface profile. The glider was all black and looked quite the weapon, it was very fast and more nimble, however it turned out to be too small to produce a good sink rate, and therefore was not suited to most pilots. I then tried a small as possible lower surface that still encased the crossbar on the standard Shark to see what effect it would have on handling. On my first test flight at a training site, the glider rolled so quickly in the first turn, I found myself in a steep dive rather close to the ground. A max flare just avoided another fractured neck and all right in front of my wife Juanita. It seamed clear to me that point it was time to move on to something else and that was my last flight.

The Shark was an amazing and unique glider with a lot of innovation and we did manage to go a step further than the Comet type gliders. Warren also had good success with a trike option. However around this time the hang glider market was shrinking in New Zealand and we basically ran out of funds, and with my decision to stop flying we decided it was a good time to move onto other things.

That’s my story of hang glider design in New Zealand during the mid to late 70’s and early 80’s. Footnote

In the early days I learned a lot from my friend Rob Beresford not only on how to fly but how to think about a hang glider. Rob built all his gliders in his garage and he made everything except the sail. When I first modified the Flexi Flyer sail and then made the Skua sail I was on my own, there was no point of reference at all, until the Cohen gliders turned up, and that was the big “AH HA!” moment. As a sailmaker I knew what Cohen had done and I knew I could do better, hence the Lancer range. I was also influenced a lot by Bill Moyes a hang gliding pioneer and legend who over the years was very supportive and a friend.

This has been a blast to write and I hope its been fun to read.

Right; Fark it’s a Shark at worlds in Japan Below; The Trike option