Forces on sails to stay within the limitations of a craft's stability and power requirements, which are functions of hull (for boats) or chassis (for land craft) design. Sails derive power from wind that varies in time and with height above the surface. In order to do so, they are designed to adjust to the wind force for various points of sail. Both their design and method for control include means to match their lift and drag capabilities to the available apparent wind, by changing surface area, angle of attack, and curvature. Wind speed increases with height above the surface; at the same
Twin Sails Bridge Twin Sails Bridge The Twin Sails Bridge (also known as The Second Harbour Crossing) is a double leaved bascule bridge in Poole, Dorset, England. The bridge provides a second road link from Poole Town Centre to Hamworthy. The intention is that the bridge will allow development of four major sites, two in the town centre and two in Hamworthy, including the old power station, which was closed in 1988. The bridge spans the Backwater Channel which links Holes Bay with Poole Harbour. The bridge and approach roads are connected to the junction of West Quay Road in the East and