Variation modeling is used in design to predict and diagnose potential quality problems. Most variation modeling assumes the parts are rigidly assembled. However, in some cases, this assumption is invalid. For example, when hydraulic tubes are assembled into aircraft structures, the compliance of the tube facilitates assembly. If the tubes were rigid, they cannot be assembled, i.e., the variations of the tubes and structures are too great. Despite the importance of compliance in assembly, it is typically not explicitly modeled during design. This paper proposes a new method to directly predict the assemblability of any tube design with minimal dependence CAD/FEM modeling and simulation. The model includes a variation model for the tubes and aircraft, compliance model and assembly model. It can be used during design to improve yields.