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
Scarlet Sails (tradition) popularity both of the book and of the tradition. Scarlet Sails (tradition) The Scarlet Sails () is a celebration in St. Petersburg, Russia, the most massive and famous public event during the White Nights Festival every summer. The tradition is highly popular for its spectacular fireworks, numerous music concerts and a massive water show. More than one million people attended the Scarlet Sails show celebrating the end of the 2007 school year. In 2010 public attendance grew to 3 million, with entertainers including such stars as the Cirque du Soleil, Mariinsky Ballet and Antonio Banderas. This tradition began after World