ON FINDING MYSELF IN A NEW COUNTRY.

No, not China again, though I have been back there twice during April, and to Spain and Vietnam.

This one's a sort of allegorical country; metaphorically speaking that is.

I arrived on its shores around 2 years ago, but it's mist enshrouded most of the time, so I don't yet know much about what's there- or even how big it.

I'm not the first adventurer to set foot there- though I may be the first to journey inland and publish an account of my explorations (www.peterlynnhimself.com/SSSL.php).

And I have found some areas worth developing already- as well as swamps and dark forests from which a wandering traveller might never emerge.

Currently I'm searching out higher ground so as to maybe get above the mist for a clearer view.

And I have some ideas as to what to expect, having done some travelling in a neighbouring country which has similarities.

Have you guessed yet?

It's the world of single line single skin kites of course. And the neighbouring country is where single skin steerable kites are- although even this country has barely been explored, though it was first discovered in the 1950's (Barish), and was known from travellers' tales and curious exhibits even before then.

I believe that leaf kites came first, probably accidentally discovered 10,000 or more years ago, and used for kite fishing in what is now Indonesia. These then evolved into framed kites (a rigid or semi rigid structure covered with paper, fabric or other material) of huge variety and almost every conceivable style- and had spread to every corner of the world by the 19th century.

Then in the 20th century, Jalbert and Rogallo (both Americans) developed the principle of ram air inflation. Ram air kites (the first examples were called parafoils) are entirely soft and get their form from internal spaces filled with air at very slightly above atmospheric pressure bled in from "stagnation points" where the wind's kinetic energy is converted to static pressure by Bernoulli's theorem.

Ram air kites have the advantages of being scalable- that is, they can be much larger than framed kites, which rapidly become either too fragile or too heavy to fly satisfactorily as they are made larger.

But ram air single line kites are quite tricky to design because they do not easily allow prime determinants of stability like centre of gravity position and wing twist to be varied.

Consequently, in the 60 years since Jalbert's breakthrough, perhaps less than 50 distinct styles of ram air inflated kites have been developed that can match the reliability and wind range of most framed kites.

10,000 years is quite some head start!

Now there is a third basic single line type; kites that are completely soft, have no sticks, frames or other rigid (or semi-rigid) elements- and have no internal spaces that are ram air inflated either.

In their purest form they are just a single membrane held in shape by multiple bridle lines.

Doesn't seem possible does it? But it is- see the attached photos of a single skin Octopus kite.

They hold their shape by exploiting even tinier variations in pressure than enables ram air inflation.

Many (most?) inventions are contingent on the development of new materials or forming techniques: The steam engine could not have arrived much earlier than it did because it requires the iron and steel industry- and machine tools. Computers were never going to move into your pocket before the development of integrated circuits.

But single skin single line kites could have been made with available materials and skills even before the last ice age. And their cousins, single skin traction kites, would have been even easier to get right because they don't have to also steer themselves. The only missing ingredient was knowledge.

What would the world now be like if our ancestors of a 1000 generations ago could have travelled hundreds of kilometres across the frozen wastes in a single day- and had kites to pull their canoes upwind at 20km/hr and more? What dreams, oh for a time machine!!

But I digress.

In hindsight, I think that single skin single line kites have taken so long to emerge because the first really successful single skin steerable kite (the NPW or NASA wing) is highly cambered and has a hooked (pulled-down) trailing edge.

The effect of this is to locate the NPW's aerodynamic centre of lift further back than is compatible with single line stability.

Kites that will fly on a single line are pointed upwards by their lift forces acting at a point that is forward of (above) their centre of gravity (where the weight forces act). This is not in itself a sufficient condition- most objects that meet this criteria will not fly stably on a single line- but it is a necessary condition- objects that don't accord with this can't fly on a single line.

Actually NPW's can fly on a single line if enough weight (like a person) is hung beneath them to move their centre of gravity sufficiently rearward of their centre of lift, but this is what we in the trade regard as a pretty ugly solution- for which there is no market - nor brownie points.

Like everyone (?) interested in this tiny kite niche, I had assumed from NPWs being about the only practical single skin steerable kite for more than 20 years, that their hooked trailing edge caused enough pressure build up to keep their leading edge from being pushed in. Made sense to me anyway.

Then, though they may not have been the first, Ozone revealed their XXLite parapent design- a single skin wing with an 'open' (not hooked) trailing edge. This was a surprise to me (how does the leading edge hold its shape?), and immediately suggested that non ram air soft kites that would fly on a single line were possible.

And they are; I now have 2 models on the market, both pilot style kites, the Boomer, a 2.5sq.m 7 cell made and sold by John and Irene Tan in Singapore, fionareen@yahoo.com.sg and the 1Skin, a 3sq.m 5 cell licensed to Kaixuan kxkite.en.alibaba.com/custom_page_2/Peter_Lynn_Kites.html

I hope to soon add to these a single skin Octopus followed perhaps by a Ray.

How well do they fly?

Not as well as they will after 10,000 years further development, or even just 60 years, but well enough to be useable and useful now- and in this Anthropocene age, everything happens quicker, so watch this space!
Their design is even more constrained and difficult than for ram air inflated kites, and as yet they are limited in wind range (8km/hr to 40km/hr for the Boomers and 1Skins without very finicky tuning).
But this is not a fundamental barrier, just that nobody's yet found a way to retain the lower wind range without losing the upper end.
And they do have some surprising advantages (other than being simple, inexpensive and easily packed): Huge pull for their size- typically 3x's that of ram air 'foils.
Immediate launching and re-launching- no need to inflate them first.
And they typically fly at higher line angles than ram air kites- are more like framed kites in this respect.
For now I'm sticking with the pure form, but hybrids will soon emerge, and may well come to rule. It will take very little extra rigidity in the leading edge area by way of stiffening elements or minor ram air inflated spaces to fix all the current difficulties with holding leading edge shape at low angles of attack in strong winds.

This new country, for all that it's undeveloped and has wild places (perhaps because of this), feels like home to me already (proud to be a colonist!)- though I will return to my old home now and then to spend time with my old inflatable friends and I hope to re-visit the single skin steerables occasionally too.

PETER LYNN, ASHBURTON, NEW ZEALAND, 1 MAY 2015

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