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Wrong again.

Andreas Fischbacher's Manta Ray
Andreas Fischbacher's Manta Ray
At various times during the least 20 years or so I've made statements like:
It will take a few hundred years at least before soft kites can catch up the 5000 + year start that framed kites have.
Just as there were cars before Benz and Daimler, and aeroplanes before the Wrights, there were earlier frameless kites; but make no mistake about this: soft kites started with Jalbert and Rogallo (and Jalbert more than Rogallo in my view).
It's all happened in my life time- not even 60 years have passed since the first practical ram air inflated single line kite flew. In kite years, soft kites are infants- which helps me stay calm in the face of their insolent disobedience to whatever child rearing theory I'm currently captured by.
But soft kites are growing up faster than I ever would have thought possible.
Evidence for this is the accelerating emergence of excellent new examples. Every year now, a truly original kite appears- and there are plenty of makers filling in gaps with clever variations of established shapes.

Martin Lester's Spirit.
Martin Lester's Spirit
Without insulting anyone, and not in order of merit; Martin Lester's Spirit, Marco Casada and Claudio Capelli's Cherub, various work by the Dusseldorf group of Jurgen Ebbinghaus, Rolf Sturm, Peter Reileit et al, Rolf Zimmerman's Dragon , and Andreas Fischbacher's Manta are particularly impressive.

Seriously, I did misunderestimate how rapid progress would be- because my focus was too narrow. From a purely engineering perspective the challenges are daunting. Aerodynamic theory isn't going to help kite design much in the forseeable future, except perhaps for some rigid kites. The underlying problem is that even fabric covered framed kites change shape in response to pressure distribution, which is itself mainly determined by shape. Analytically this makes things 'difficult'- which in this context is another word for impossible. Soft kites are even more so. This is not the least reason why most kite energy projects have now migrated to rigid (carbon fibre) aeroplane configuration kites.

UKS Fish, Ray, Fish, Shark and Bear
UKS Fish, Ray, Fish, Shark and Bear
But there are other paths to understanding; evolution has no pre-formed theory for it's designs and yet it has, to name just two triumphs; the cockroach and the seagull to it's credit. Cockroaches are spectacular survivors; an unanswerable, in our faces (and kitchens) challenge to the counterproductivity of social welfarism and greenism. Seagull's are spectacularly good fliers; they piss me off even more than cockroaches do. When my kites can't fly because the wind is above 100km/hr and turbulent, they're still up there in complete control showing off.

Rolf Zimmerman's Dragon.
Rolf Zimmerman's Dragon
There are paths that soft kite development has taken in addition to the Poperian process of; theory/hypothesis/experiment.
There are hybrid designs that use sticks as a crutch while learning to fly (what a mixed up metaphor).
Pilot kites provide lift and stability while new designs are developing.
And drogues- huge ones sometimes- are used to drag misbehaving kites into line until details get sorted.
But most of all, there are lots of kitemakers applying their creativity -driven by unrealisable (shhh!!) dreams of wealth and fame- but actually fired by a creative impulse that cannot be denied no matter what the rewards may be.

Bert and Ernie
Bert and Ernie
Soft kites can usefully be divided into those that are designed to excell by wind range, stability, lift, and flying angle,- and those for which some shape or graphical form is of paramount consideration.
Ram air inflated parafoils , flowforms and the like are judged solely by performance criteria. Free of shape and graphic constraints, development has been rapid. Their only remaining serious opposition as pilots/lifters is the Parasled- which is a hybrid form; ram air with some stiffening struts.

Ram air inflated kites for which the prime consideration is shape (often required to mimic some animal or sea creature) are much more difficult to develop. Thirty years ago, it seemed to me that there were very few such shapes that would be capable of flying as soft kites without big drogues or unrealistic keels/flares. I was wrong about this too- never would have thought that Martin's Spirit, Pierre Fabre's Spaceman, Rolf's Dragon or a Ray could fly without these encumbrances. Actually, this isn't true- in my youthful exuberence I thought everything would be possible, and within a year at most, but then swung too far the other way when early attempts didn't fly.
What will eventually be possible is an open question.

For themed soft kites, there are four basic layouts.

The first, and easiest, is shapes that have some substantial drag element inherent in their form.
Octopus kites are an example, Martin's Spirit is also (but much cleverer than the Octopus).

The second style is shapes that have sufficient width relative to length (aspect ratio) for wing drag to provide stabilising effect. My Ray, Andreas's Manta Ray and Rolf's Dragon are examples. The attached photo of Rolf's Dragon shows how high angle of attack bridling of the wing tips has been used to provide the required stabilising effect. Smooth tailed Rays use a combination of high aspect ratio and progressively more reflexive profiles (that have more drag relative to the lift they generate) to achieve the same result.
I expect that Bernhard Dingwerth's new Butterfly will eventually succumb to this approach and join the ranks of breakthrough designs.

Pierre Fabre Spaceman
Pierre Fabre Spaceman
The third style is rather special: anthropomorphic kites. So that dingbats (most Australians and a smaller proportion of other nationalities) don't need to reach for a dictionary; these are human form kites. Confusingly, Martin's Spirit is not one of these, but Bears, various Sesame Street contributions from No Limits, Pierre's Spaceman and the Casada/Capelli Cherub are.
The key stabilising element for this style is arms- they stick out the sides and generate drag; work rather like the high wire artiste's balancing pole. The main challenge for designers of this style of kite is to get enough rigidity in the neck so that the head doesn't fall off to one side or the other and bugger things up.

Jurgen Ebbinghaus Fish
Jurgen Ebbinghaus Fish
The fourth style is low aspect ratio kites ; fish and the like. That such shapes can work is established- Jurgen Ebbinhaus's fish for example- but they are inclined to violent oscillating motion which can only be damped by huge drogues (my early attempts at Dolphins and Phillip McConnachie's Shark and Orca for example). The cause of these oscillations is still speculative. Von Karman undoubtedly has a malign influence (he identified and quantified the periodic flow separation that requires, for example, tall chimneys to have disruptors to damp out destructive oscillations).

But I now think that the dominant cause of their instability is that the aerodynamic lift forces operate some distance behind where frontal lateral area has it's effect.
To explain this by analogy, I first need to ask a question; what's brown and sticky?
No, silly; not hot chocolate, the answer of course is a stick,- and when a stick is shoved from an end, it doesn't stay in alignment-as it would if pulled instead.

UKS Fish
UKS Fish
I've been using this theory to develop the UKS Shark and Fish- changing their shape incrementally to move the centre of lift forward and lateral area rearward . This has been tolerably successful. Drogueless, they do still thrash around a bit at low wind speeds but straighten up as the angle of attack decreases when the wind builds. This theory also explains Jurgen's fish I think- but von Karman is still probably lurking there somewhere.

But theories by themselves won't get the job done. Even billions of dollars and the undivided attentionof the world's aerodynamic establishment wouldn't convince kites to yield up all their secrets.
What's working is the trial, error and very occasional success of many attempts, an essentially Darwinian process that results in progress because failures are discarded while successes get replicated.

It's onwards and upwards then!

But will soft kites come to dominate completely?- will framed kites ever become an endangered species like indigenous kites?
No chance (consider again the title for this newsletter though), but that large soft kites are increasingly important for kite festivals is undoubted, and this is motivating more designers to make contributions. If 20gm/sq.m fabric became available at an affordable price, soft designs could make a strong challenge at the smaller end and in very light winds as well.

Peter Lynn, Cervia, May 29th 2010.



octopus
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