As wind energy continues to expand to new frontiers in terms of the location, number, and size of wind turbines, the industry has begun to seek smarter operations and management solutions. Wireless sensing nodes could provide a low-cost platform to support a variety of applications designed to reduce the levelized cost of energy and increase the safety of wind turbines. However, a wireless sensor node deployed on a wind turbine blade would have an extremely limited energy supply. To combat this limitation, we present BladeMAC, a new MAC-layer protocol designed for sensor nodes deployed on rotating wind turbine blades. BladeMAC overcomes a unique cyclical channel problem to allow a sensor node attached to a rotating blade to opportunistically and efficiently offload its data to a sink node attached to the turbine tower. We have implemented and evaluated BladeMAC using Contiki OS and the Cooja simulation tool. We present results showing that BladeMAC effectively deals with the cyclical channel problem at a wide range of data arrival intervals, and that BladeMAC is insensitive to rotation speed and rotation speed fluctuations.