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
North Sails to designing sails, with the goal of building sails that were faster than the competition’s. North began testing the strength and stretch characteristics of sailcloth he received from his suppliers, to eliminate variability in his raw materials. He introduced computer-driven cloth cutting machines, to increase the consistency and repeatability of a sail design. North was a pioneer in computer modelling of sail forces and structural loads. North used a laminated Mylar and Dacron sail on the 12-metre "Enterprise" in 1977. North’s emphasis on computer technologies and new materials is reflected in the company today, which makes intensive use of computer