Soft actuators producing bending motions have gained significant attention for their advantages in mimicking the properties and movements of human muscles. However, the research on soft rotary actuators has yet to keep pace with other soft actuators. This paper makes two key contributions to the design and modeling of these actuators. First, we introduce a novel design for a soft rotary pneumatic actuator. This design outperforms existing cylindrical shaped soft actuators, especially in terms of torque. Second, we present an analytical model based on finite deformation. This model accurately describes the relationship between rotational movement and corresponding torque. The accuracy of this model is validated through Finite Element Method (FEM) simulations and corresponding tests. By providing a mechanically efficient design and a highly accurate analytical model, this work offers a comprehensive solution for the development of new soft pneumatic actuators.