Performance of flexible auto-rotating wings

Seed dispersal relies on the aerodynamical fitness of seedpods that, unlike many experimental surrogates, are found with a variety of mass distribution patterns. We investigate experimentally the effect of various mass distribution on the descent motion of thin rectangular auto-rotating wings. Under carefully controlled condition, we use high-speed photography to extract the flight characteristics such as flight duration, descent angle, and flight range, and connect them to their relative effect on the dispersion of multiple flyers. We found that both span-wise modifications, primarily affecting flexibility, and chord-wise modifications, affecting the wing's moment of inertia, can lead to improvement of aerodynamic performance. In particular, we found that while whole-wing flexibility lead to a drop in flight range in agreement with previous studies, moderate tip flexibility is beneficial.