The search for an alternative propulsion system for marine transport has returned back to its roots, to a technology that has been known for thousands of years, wind propulsion. The need to reduce emissions and costs of transporting goods has revived the idea of applying wing sails to ships, starting with the experience of high-performance racing sailboats, that have been experimenting with this concept for 20 years already. The purpose of this work is to provide an innovative framework for wing sail design optimization, known in literature as Surrogate Based Design Optimization. The idea is to reduce the computational burden of high-fidelity fluid dynamic simulations, that would be too impractical to use coupled with an evolutionary algorithm for design space exploration and substituting them with a surrogate model trained on as few samples as possible.