Japan develops retractable metal sails for cargo vessels
It is an interesting concept that is projected to save about 30 percent of fuel usage. It would take about five to 10 years to recover the cost of the system. There effectiveness probably would depend on the direction of the wind in relation to the course being navigated. In traditional sailing craft, the sails are usually most effective when the wind is coming from the side of the ship. Going into the wind or with the wind behind the ship is usually not as fast.