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 in the Sunset adding a sense of brooding, thespian eloquence to the disc's shadowy post-hardcore, AFI all but reinvented themselves," and "With longer, deeper, richer, more complex compositions than they've ever attempted before, Black Sails tackles everything from brooding hardcore ... to shimmering balladry..." The publication also went as far as to say that "Black Sails" is "their first epic." "Decoy Music" reviewer Aaron Yarborough praised Davey Havok's lyrical contribution to the album, commending his efforts to "find himself," saying "the way he expresses how he feels is pure poetry." Yarborough concluded by recommending the album to "anyone who likes heavy punk." All