The DynaRig owes its origin to work done in the sixties by Wilhelm Prölss , at the time he believed the system could provide additional propulsion for ships. The DynaRig is effectively a square rig, the mast is freestanding and the yards are connected rigidly to the mast, in this case each mast supports six yards. The yards, unlike a conventional square rigger, have built in camber of 12%. The sails set between the yards in such a way that when deployed there are no gaps to the sail plan enabling each spar's sail plan to work as a single sail. The sails, when not deployed, furl into the mast. The sail is trimmed to the wind direction by rotating the mast. As there is no rigging the yards have no restriction on rotation and this taken together with the curved (shaped) yards, low windage and effective single piece sail combine to give the rig improved aerodynamic efficiency compared to a traditional square rigger.