Nonlinear fluid–structure modeling of a semi-rigid jib and forestay: How does the forestay affect performance and structural stress?

A numerical fluid-structure interaction (FSI) analysis is conducted on a semi-rigid jib, as part of the Solid Sail Performance Oriented Rig Technology (SPORT) project, which purpose is to develop large semi-rigid sails to equip merchant ships. The pressure loads on the sail are calculated with a semi-analytical model based on the lifting line theory, coupled with a finite element structure solver to compute the composite layup deformation. A new forestay model is proposed in this study, formulated as a beam with negligible bending stiffness. The FSI model is first validated without the forestay. The maximum of camber, position of maximum of camber and twist are in good agreement with the experimental measurements. Furthermore, the influence of the forestay on the aerodynamic performance of a sailboat in a representative upwind configuration is evaluated. The comparison of the propulsive force with and without forestay connections shows that the add of a forestay tends to reduce the performance of the jib, for most of the tack and clew loads. The stress analysis also shows that for a given propulsive force and a constant sum of tack and clew loads, the addition of a forestay does not significantly reduce stresses in the panel membranes.