Abstract
The suitable airfoil for a micro air vehicle has been studied experimentally. A flapping airfoil is one of solutions for small sized flyers, but the flapping motion similar to insects is not easy to realize because of its complicate mechanism and requirement for light and flexible materials. It is known that insects yield the lift force by a large vortex trapped near the flapping airfoil. Since I noticed that the similar vortex structure is observed near a rotating airfoil around its spanwise axis, the characteristics of the rotating airfoil are studied as an alternative flapping airfoil. The lift force is measured by falling a piece of paper that rotates naturally derived from a well known phenomenon as an auto rotation. Several shapes of airfoil are tested in relation to variety of insect's airfoil. The difference between airfoils of a dragonfly and butterfly is described in this paper.
