Legged locomotion with its variable contact situations between feet and ground is of interest in today's research on humanoid locomotion. This paper uses a hybrid modeling framework to account for different possible ground contact situations of a simple biped gymnast experimental platform with five joints. For the considered biped unactuated rotation around foot edges as well as plane foot contact is considered in modeling and trajectory planning. Presented is a planning algorithm for periodic walking trajectories. The stability of the resulting hybrid periodic orbits is investigated in numerical experiments.