Fabric development at Flysurfer

The cloth is usually the part of the kite that kitesurfers pay the least attention to…although it performs the function that actually makes our sport possible: it catches the wind. It also makes up the largest part of the kite equipment and the demands on it are equally large: it has to be durable, cannot absorb water and must survive light, salt and hard crashes. And last but not least, it has be light because a kite should fly, obviously.

Most people can only guess at how much thought manufacturers put into their components. Alone in a Flysurfer Kite with a surface area of 10 square meters, approximately 30 square meters of sail cloth are implemented. From that amount, one-third is used for the top- as well as bottom-sail, the rest for the profile ribs and components inside the kites. Then come diverse reinforcement bands, profile nose stiffeners and some small parts such as pulley, shackles, depower rope, lines and much more …

For Flysurfer, this means an immense amount of testing, because if only one of these parts fails to function, frustration is the result, not just for the rider, but for our service division as well. Here, we benefit from the synergy created by having another aviation sport, skywalk paragliders, under the same roof as Flysurfer. For more than six years, we have been developing our own cloths at skywalk/Flysurfer, usually in cooperation with partners. Testing procedures were not predetermined, but resulted out of our own development.

Torture before certification

Before we find a cloth that is good enough for implementation in our kites, test models must be subjected to various kinds of torture. We rip, tear, stretch, age and sometimes use our own invented methods of testing on our cloths. We would like to give you a brief look at the process each of our new materials must undergo before becoming an integral part of a Flysurfer kite.

The first station is for static tensile tests, where we test the cloths for tear and seam strength. A five to ten centimeter strip of cloth is tensioned into the test construction and stretched until it tears. The strength values are protocolled and analysed in diagrams. We can also control various sewn samples for their load capacity.

Tear strength alone is not everything, not by a long shot. When a cloth is extremely stretchable, this naturally effects flight performance.The goal is a stable and constant wing. Thus, we test the stretch in both directions, warp and weft. If different values occur, this can be attributed to the use of different threads. But this can be used to an advantage when the material is cleverly implemented in the design of the kite.

The static tests are supplemented with a so-called shock test. We believe that this is a necessary step, although we are aware that most likely no other manufacturers subject their materials to such a wide degree of testing. In a specially constructed drop tower, a weight is dropped from a predetermined height onto the stretched sample.The impulse load is calculated with ultra-quick measurement devices and then saved. Flysurfer is the only kite maker equipped with these measurement capabilities. Why are these measurements so important? It is simple: materials often react differently to abrupt load than they do to static force. For example: glass can stand up to an unbelievable load, if the load is placed slowly and with equal force onto the surface, but will break easily from an abrupt impact. Rubber has the opposite reactions. We can observe these effects in kite cloths. Here, we have to find the right compromise, since excessive stretching has a negative effect on flight performance. The kite should last, no matter how much abuse it gets.

When a cloth can stand up to both static and dynamic load equally well, that does not automatically mean that the kite will easily survive a tree landing. Surely one or another of you have noticed that Flysurfer kites almost always survive tree contact completely or at least almost fully intact. Along with our rigid tube-less system, the material selection contributes enormously. This “tear strength” is calculated with a so-called bettsometer. A small needle is inserted into the cloth and the resistance to additional tear is measured with a simple force meter. A very effective and informative test which reproduces the actual resistance of a cloth to tearing.

One might think that also net fabrics would have performed well in the above tests. Still, it is obvious that these are not suited for catching the wind. Therefore, we always test the porosity of the cloth. Flysurfer uses a JDC clock for this purpose. Air is sucked through the cloth sample in a defined area and the time is measured until a predetermined volume is sucked through. The longer it takes, the more airtight the cloth.

Tear strength, impermeability and elasticity are all nice properties. Flysurfer stands for product longevity like no other manufacturer in the kiting sector. The cloth should maintain its properties for as long as possible. We have never neglected testing. But how do you simulate the aging of a kite? Very simple: outdoors. There are still no laboratory tests which can simulate the effects of exposure to sun, wind, humidity and temperature change better than nature itself can. So we hang multiple cloth samples over a period of weeks outdoors, and let nature take its course. Once the cloths have spent weeks outside, the test series begins again. Naturally, we do extreme long-term studies as well. When we get our hands on an old kite that is no longer worth repairing, we get cloth that has lived through the everyday abuse of kiting, sometimes years old. We would like to know: what other kite manufacturer takes this kind of time and effort for testing?

In addition, we examine cloth workmanship thoroughly and constantly look for the signs of wear and tear. The goal of all these considerations is dependable products and carefree sessions on snow, water and land.

The Deluxe Cloth – flagship of our cloth development

When you get a glimpse of the testing that our materials undergo, you can understand why the path of the Deluxe Cloth development was a long one and why the Deluxe Cloth is what it is today: an unbelievably tear resistant, super light, yet still durable cloth. The number of steps and detours in between was anything but inconsequential. We continue with testing and researching today, since weight, tear strength and durability are attributes that can never be good enough.

We use Skytex 27 from Porcher Marine as a basis for our Deluxe Cloth, since the unbeatably low weight particularly impresses us. Under 30 grams per square meter is certainly a bold statement. Only the strength of this cloth is in need of improvement, from the point of view of kiters, but can certainly be overcome when you look at the weight of the competitons cloth. We implemented two different cloths, on the profile ribs and cloth, into our first generation of Silver Arrow, the fastest kite in the light wind category at that time. The kite lost over a kilogram of weight, which allowed Flysurfer to usher in a new and up to now, unbroken era of light wind kiting.

But we are still not completely satisfied. Eventually, one or another kite will land in a tree or on a sharp rock. Furthermore, it would be a shame to limit light construction to only the larger kites, therefore the kites subjected to less force.

It is exactly these points that we want to improve upon. Together with the manufacturer of high tech balloon cloths, Aerofabrix, we continue to research and tinker. With many different ideas and approaches. Alu-damping, which weighs practically nothing but provides unbelievably good protection against UV-light, was a part of this testing as well. Unfortunately, use of this coating led to nasty corrosion upon constant exposure to saltwater. Too bad, because we would have loved to have this shining, chrome-colored kite in our product range. So we switched to other coatings. In the end, an only marginally heavier cloth became the original Silver Arrow cloth, which is so tear resistant that we were able to produce the profile ribs as well from the same material. And it is exactly for this reason that the heavier weight did not bother us, because all in all, the kite remained almost as light as our first Silver Arrow and even 30 percent less than the standard variation. At the same time, we were able to build a stiffer kite, immediately apparent during the first steering manoeuver in the air. And that with a tear strength that can be seen. Flying is twice the pleasure when you can depend on the long life of your equipment. At least, that is the way we feel.