Fig. 11. Augmentation of mean force coefficient during clap-and-fling wing beat plotted as a function of duration of wing rotation within the stroke cycle (A) and Reynolds number based on wing tip speed velocity (B). Augmentation of mean lift and drag coefficient due to clap-and-fling, scaled to the performance a single flapping wing is shown in (C) and (D), respectively. Angular distance between the wings during clap was –4.95°. For these experiments we modified a conventional stroke pattern (stroke amplitude=160°, cycling frequency=0.16 Hz, geometrical angle of attack at mid stroke=50°, up/down ratio=0.5 and approximately symmetrical timing of wing rotation at which 50% of the rotational phase occurs before and 50% after the clap) by systemically varying the onset of wing rotation at the end of each half stroke (in A) and stroke frequency (in B–D).