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The company Aniprop in Göttingen who is well renouned for his pioneering work developing FESTO Smartbird got noticed about our work and finally offerd us to make tests in their wind tunnel. We therefore created a new profile exclusively for these tests. The profile was made from wood and other light materials carring the aeroflexible surface.

Data of Measurement

Wing depth


Wing width



7,9 E+04 ... 1,49 E+05


4 m/s ... 7,5 m/s


2,01 (4m/s) ... 2,068 (6m/s)

Gliding ratio

ϵ = ~53

Wind tunnel height


Wind tunnel width


Force measurement

2-dinemsional 3 point measurement, Force measurement cylinder

drive & control of attack angle

step motor 1,8°/step

In the first Run we measured at different attack angles and zero wind speed to have a reference for the balance point. Then after several runs at different speeds we gained polar diagram curves showing us the performance of our wing. Luckily the results turned out to be better than expected. at every speed we measured our cA (german) / cL (english) parameter produced values above 2.0 which is actually a very high value. Usually good airfoils create a cL of around 1.5.
When measuring the cW (german) / cD (english) parameter we had an rather strange result that this parameter turned out to be slightly negative at his best point. The results were so far independent from the cL parameter. By shifting the force center a few millimeter away from the measured force center in the first run the cD values could be corrected to more plausible values. Thus cD so far remained unclear.

Polardiagramme AFAX-4ms2D 02 xs

Image 1: Polar diagram comparing conventional Airfoils (violet) with aeroflexible Airfoils (blue+green)

The comparison of the blue and green curves in the polar diagram shows another interesting feature and is another evidence of the performance of the aeroflexible surface. The green curves indicates a profile which has only a partial aeroflaxible coating while the blue curve indicates a profile which is entirely coated with an aeroflexible surface. Finally we would like to thank Dr. Wolfgang Send for his support and contribution to our aeroflexible project.