WINDSTRUC is a three-year project where calculation models are developed and compared with measurements on aphysical model. The project will employ and doctoral student. Design companies, equipment suppliers and shipowners will contribute with resources and financing. The project comprises three main parts: (1) Design and manufacture of a telescopic sail rig that was developed and patented within the Effship project; (2) Development of tools for dimensioning and optimization of sail structures for ships based on Fluid-Structure-Interactions. Sail structures, as well as large wind turbines, require simultaneous analysis of both structure and fluid structural since the deformation due to the surrounding flow is so large that the flow is affected by the deformation and thus creates a coupled problem; (3) Analysis and evaluation with ShipCLEAN models. Model for the telescopic rig is implemented in the ShipClean model and its performance is evaluated and compared with other sailing concepts.