Soft wing sails may offer an elegant solution and provide a means of keeping costs down. Soft wing sails may capable of producing similar sorts of performance to rigid wings. Much of the performance advantage of rigid wings comes from the multiple element design. Multiple element wings can carry high camber due to the re-energisation of the boundary layer part way along the leeward surface of the wing which delays trailing edge separation. These increased cambers result in higher lift generation.
We know single element soft wings are capable of generating good lift and drag characteristics. Multi-element soft wings have not really been explored but are certainly possible. I have penned conceptual designs which, at least in the preliminary modelling, show great promise of approaching rigid wing performance. We are really at the beginning of the technology curve for soft wings and there are significant design and performance improvements waiting to happen.
Via Greg Johnston