We have a treat for you, namely an interview with Urs Hungerbühler, who has been responsible for the research and development of GA-KITES for many years now. He has implemented his detailed knowledge about aero- and hydrodynamics into the development of our highly renown GA Wings range and also the complete GA foiling segment. Based in Taiwan, he can both visit production facilities for quality control on a regular basis and test new prototypes immediately in different conditions. Urs thinks outside the box, comes up with innovative solutions and teamed up with experienced team riders from our windsurfing, kitesurfing and wing foiling teams to form a multi-faceted foil range for all riders.

Hello, I was born and raised in Switzerland. We were very much into mountain sports, such as skiing, climbing and flying paragliders. I started to work for a Swiss paragliding company, improving the wings. That was about mid 90's. At that time, we were already building kites for land use, like skis or buggies. We all new, if we manage to build a kite that can relaunch from the water, it will become a new water sport with a great potential. When we saw the first tube-kites, 2 lines at that time, we decided to do a better kite with more performance and better control than with two lines. My two brothers and me started to build foil-kites which were able to relaunch off the water. Pretty soon some of the big windsurf companies came onto the market, and we decided that we cannot compete with them and let the kite story be. I then moved to Tarifa in Spain for the reason of wind and kitting. After a while, I started to work with Monty Spindler on some kites. He then made contact with Knut Budig, to see if there can be a cooperation. Knut at that time, was already involved with Gaastra and was actually looking for people who can design kites. So, since then, I did develop and designed kites for Gaastra. When Gaastra started to build up another factory, I spent quite sometimes in China. During that time, I started to learn to speak Chinese and met my now wife, which is Taiwanese. After that time, I still wanted to stay in the Chines region to better learn Chinese, but I didn't want to stay in China itself. So, it was a kind of obvious to jump over to Taiwan. Here we got excellent wind and at the east-coast as well nice waves. It's kitting in winter and winging or anything with foils in summer. Relatively recent I started to work as well on foils and later on wings too.

To start from scratch, it is quite a long process. Later on, when there is some basis, it gets a bit more straightforward. I usually do first some basic calculations for the profile. Basically, develop a profile. For that, I do some simulations as well. Now, that is not a simulation of a wing. That is too difficult, as wings are flexible. That means, we don't have all the input parameters right. In CFD's a small error in input is not just a small error in output, but total rubbish. However, for the development of the profile we can do simulations and calculations to define the speed, lift, stall speed and so on. Once I got a profile, I will draw a wing in a 3D software, which is parametrised. That means I can change parameters fairly easy without needing to re-draw the wing. There I manipulate the wing, adjust all the parameters, like LE curve, AR, tip-shape and all imaginable parameters. Once I got a wing as wished, I do the unwrapping of the 3D file into a blueprint. I then manipulate the blueprint in a way, that the factory understands the wing and knows how it has to build it. That includes the waypoints, reinforcements, material definition and so on. The factory then builds a prototype. In the best case, I can go to the factory (that was interrupted due to Corona, but is back again) to check the wing, see the problems and ways to improve the building way. The next step is testing the wings by testers (or myself for basic stuff) analyse the feedback and change the wing accordingly.
 

The materials are important for a few reasons. Wings should be light but still durable. They are very often in contact with the water, riders fall into it, have to turn them around and squeeze them like this. As well, there is no support to keep the shape other than the pressure in the tubes. No bridles and no carbon mast. To get them stiff it needs some pressure in the tubes, which is a high load on seams, for example. While riding the wing it flexes, which adds more load to the seams. So, basically, they are much more stressed than a kite. That is the tubes. For the canopy, the wings are very delicate to stretch. The canopy should have a bit of tension that a wing flies nice. This tension can be lost with only a bit of material stretch, which then results in a flapping trailing edge, unbalanced force development and bad performance. So, the demands for the materials are very high.
 

The Cross wing is an all rounder wing and the Poison a bit more advanced. The profile of the Cross is developed to generate lift and forward-push already at low speeds. It is as well more forgiving of mistakes in pumping for takeoff and never loses its drive. The strut is with an angle for a better ergonomic and less fatigue of the hands/ wrists. LE and strut have a fair diameter for a robust feeling and high stiffness. This just makes it easier to handle the wing and get its performance out. 

On the Poison we used a profile, which is faster and more agile. It needs a bit better pumping technic than the Cross to generate power and is not so forgiving.  The strut shape is as well with an angle, for the same reason. However, on the Poison it is a bit more segmented/complicate in order to connect the strut earlier to the sail. This makes the profile a little bit harder, and we can use a little less diameter.

The MP wings are developed for a high performance. They are fairly high aspect ratio. The AR is not for all sizes the same, it starts with 7.4 on the smallest wing and ends with 8.5 on the biggest wing. Like this, they all feel pretty the same. The stability of the small wings is increased a bit. We developed a very fast profile for them, which still has a huge wind-range, means that the low-end is not too bad either. One of the problems of high aspect wings is the maneuvrability. We could solve that problem with a quite sophisticated tip shape. It has not a lot of surface there and is a very “slippery” tip. The AoA is reduced to 0 degrees and does not create lift. It is basically a winglet, which keeps the vortex of the wing.