In June 2018, a European project team installed an 18m x 3m Flettner rotor on multi-purpose cargo ship Fehn Pollux. While the technology itself is about a century old, there are only a few demonstrators in action, and measuring their performance is not as straightforward as one might think. The team were proud in particular of their handiwork installing a set of measuring instruments. Now the first results are in, confirming the excellent properties of the rotor in relation to seakeeping; and even better in terms of performance. If all that sounds too good to be true, there is one potential problem with the excellent paper by Michael Vahs and co-workers in Schiff und Hafen - it's written in German.