Rigid wing sails resemble classic sails but are comprised of rigid materials so that the sectional profile of the Sail is more stable and resembles an aircraft wing in the cross section.
Wing sails are mounted vertically on the main deck and/or forecastle of the ship and operate under the same aerodynamic lift principles as an aircraft wing. Each wing has a specific aspect ratio (height/width) and wing profile geometry so that an as high as possible aerodynamic Lift force is generated.
In adverse conditions or at berth, wing sails can be furled/reefed telescopically or otherwise to remove unnecessary drag forces or air draft. All systems are designed to work automatically, thus by adjusting their wing sails orientation depending on the anemometer readings, while in unfavourable wind conditions there is an automatic function for reefing or furling.
Normal sizes offered by the system providers so far relate to a Wing Sail height of 20-37 m and width 8-20 m – or other tailor-fit intermediate sizes, while in case of a solo Wing Sail installed in the forecastle can be a bit higher when in full deployment – i.e 50-55 m x 15 m and 20-25 m when reefed.
One issue with the wing sails systems, especially the ones which are equipped in more than 2 on board is related to how the IMO visibility and safe navigation rules are satisfied, which is still under review for case-by-case consideration at the moment.
Installation equipment other than the sail and structure includes an electro-hydraulic power pack for rotation, reefing and furling. A remote-control panel is usually installed on the bridge for system operation. Moving parts will need regular inspection, overhauling and maintenance especially of the wear and tear items (i.e. bearings, gaskets, etc).
– Information courtesy of Konstantinos Fakiolas’ book ‘Wind Propulsion Principles’, Edition 1 –