While attending the ceremony of the 60th anniversary of the low-speed wind tunnel of TU Dresden, I was reminded what a long journey we’ve walked already with the APUS i-2. In the early design phase of the APUS i-2 development, we added another dimension to the airfoil selection process: Volume. On the one hand we were looking for a sleek and highly efficient airfoil that gives us the cruise speeds at low power consumption, on the other hand we had to give the inner wing a certain volume to carry the hydrogen required for the 800km mission in our Tubestruct™ structure integrated hydrogen storage. Less volume would mean higher pressures in the tank to carry the required hydrogen, which brings a lot of weight and thus costs again performance. An optimization challenge that we could only master by tailoring an airfoil to our needs. Together with the Experimental Aerodynamics Group of TU Dresden we developed an airfoil and validated the calculations in the low-speed wind tunnel. Thanks to Experimental Aerodynamics Group for having us at the ceremony and even more for the joint development!