'Imagine if you could compare kite models against each other based on figures, similar to a car-magazine test. Parameters such as steering pressure, lift, drag, depower-ability, turning speed and more could be compared by looking at objective data. This would revolutionize the development process and the way we judge kites in general. A designer’s dream come true!’ says Ralf Grösel, Duotone kite designer. Back in 2013 Jan Hummel approached Ralf with exactly that idea – project TETA (Test and Evaluation of Tethered Airfoils), operated by the University of Berlin. It was the primary subject for Jan’s PhD thesis to figure out how to create valid, testable, repeatable data to establish an objective way to measure various performance attributes of a kite.
Dietmar Göhlich, professor at the department of Methods for Product Development and Mechatronics at the Technical University of Berlin explains: ‘The problem is that compared to rigid wings, the physics of flexible membranes such as kites is very complex. The general knowledge about flexible wings is limited due to the deformation of the kite under aerodynamic load.’
The solution to this problem is the world’s first test bench, TETA, which was specifically developed for validating flexible wings. It is essentially a trailer towed behind a van, bristling with scientific apparatus, from which a kite can be flown automatically or manually.
Says Jan, ‘To perform repeatable automated maneuvers, repeatable steering inputs are of course necessary, the steering inputs are implemented by two servo motors and can be controlled by the pilot via fly-by wire or from the control unit itself or from both in combination’.
Jan mentions another aspect. ‘In the long-run there are implications for computer assisted design … If you don’t have valid data, you are not able to feed complex simulations like FEM (Finite Element Method) and CFD (Computational Fluid Dynamic). Only with correct information of how the flexible wing will react to different windspeeds and rider input will a simulation software be able to provide realistic results. It might still be years away, but the information we are gathering from the test bench will lead to great leaps in our ability to model flight characteristics of a kite on a computer before we even build the first prototype.’
‘I would wish to see that this test bench becomes a standard within the kite industry. Magazines could take this opportunity into consideration to validate different kites from different brands,’ says Ralf. ‘For me this project showcases the capabilities of advanced testing technology, and future developments will surely benefit from it. Especially with the next generation of fully automated tests, which are currently under development. These tests will be precise and accurate as nothing else ever before.’