This paper presents RoCuModel, an iterative tangible modeling system that helps users build 3D models in a tangible way for personal fabrication. It consists mainly of a special tangible curve and an infrared camera. Users can create 3D objects by creating sketchy low-fidelity shapes with the hand. By rotating the curve along a fixed axis, users can visualize the volumetric model in a 3D space in real time. RoCuModel provides a new way for people to design and create a rotationally symmetric 3D model. This is our first step towards eliminating the gap between specialists and non-specialist users in personal fabrication.