Optimization of a complete 2D flying sails configuration is considered. An optimum shape design problem is then defined considering the maximization of the drive force on the sails and a complete flow modelling including accurate turbulent effects. The corresponding numerical algorithm is based on a gradient descent method coupled with a discrete shape grid-point parametrization. The descent direction is obtained by an exact computation of an incomplete discrete gradient associated with a multi-level strategy. The numerical behavior of the present formulation has been illustrated by the optimization of a real 2D configuration of an America's Cup yacht.