What are soft wing sails and how do they work?

These wind propulsors are similar to the rigid wing sails that are described above, the difference is that they do not have a rigid wing coverage surface material but a more soft one, so that Furling and adjusting of variable camber of the wing profile is possible.


The material of the soft sail is normally made of composite (polyester sailcloth or similar) for endurance in a marine environment, having certain flexibility for being compressed and reefed appropriately.


When the wind becomes unfavourable then instead of retracting, the wing sail is reefed and furled to reduce their exposure to the wind.


The aspect ratios per wing can vary from heights of 30-40m and width from 10-15m, depending on the design and the available space on board.


The requirements for the soft wing sails regarding the installation are mainly similar to the rigid wing sails as described previously, it would be expected an extra auxiliary mechanism to be installed for the furling of the sail cloth, either that be electrical or hydraulic or even pneumatic depending on the provider.


One differentiation regarding maintenance compared to rigid wing sails would be expected to be the soft cloth strength and durability, since such would be related to the operational hours on wind force exposure but also to environmental conditions, such as sun radiation, heat, cold, ice and humidity.




– Information courtesy of Konstantinos Fakiolas’ book ‘Wind Propulsion Principles’, Edition 1 –