We present an interactive design system for designing free-formed bamboo-copters, where novices can easily design free-formed, even asymmetric bamboo-copters that successfully fly. The designed bamboo-copters can be fabricated using digital fabrication equipment, such as a laser cutter. Our system provides two useful functions for facilitating this design activity. First, it visualizes a simulated flight trajectory of the current bamboo-copter design, which is updated in real time during the user’s editing. Second, it provides an optimization function that automatically tweaks the current bamboo-copter design such that the spin quality—how stably it spins—and the flight quality—how high and long it flies—are enhanced. To enable these functions, we present non-trivial extensions over existing techniques for designing free-formed model airplanes [UKSI14], including a wing discretization method tailored to free-formed bamboo-copters and an optimization scheme for achieving stable bamboo-copters considering both spin and flight qualities.