How to be the best at sail pumping?

Pumping or flicking1 is often used by sailors to get extra propulsion while sailing (subject to restrictions by the racing rules2). Common unsteady sailing situations, due to crew action (e.g. manoeuver like gybing3) or environment conditions (e.g. pitching in waves4, 5) can be reproduced in tunnel testing with accurate flow and yacht attitude4 control. Repeated pumping generating unsteady effects on aerodynamic forces6 is investigated here with a dynamic trimming system. Results are presented for different apparent wind angles (AWA) to determine the best pumping conditions and better understand the physical mechanisms involved