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
Black Sails (TV series) Sails" is a pirate treasure. The Starz series vividly depicts the daily life of pirates." Jeff Jensen of "Entertainment Weekly" said, "Not even a guilty pleasure, "Black Sails" is arrrrrr-estingly good". Tom Long of the "Detroit News" commented "Alliances are made and broken, power shifts go this way and that, blood is spilled, and wenches keep wenching. It's oddly addictive, and the cast—made up mostly of British, Australian, and Canadian actors—is as sharp as you'd expect from pay cable". Conversely, Brian Lowry of "Variety" said, ""Black Sails" never quite takes off, developing into a tired treasure hunt with indifferent casting