The latest version: Mark IV
(Source: Omer Wing-Sail) This wing is based on a rotating A frame mast, that supports the wing in both sides, having an accurate wing profile as well as high moment of inertia. It is made of three different sails – two main sails and one leading edge sail. All three sails are sliding independently along the mast. When all three sails are hoisted, we get a wing that one can reef and drop like any other standard sail.