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) united to celebrate the end of the school year in connection with the symbolism of the popular 1922 children's book "Scarlet Sails" by Alexander Grin. During the first celebration, a boat with scarlet sails sailed along the English Embankment and the Admiralty Embankment towards the Winter Palace. Although it was designed to update the rusty revolutionary propaganda, the "Scarlet Sails" tradition eventually evolved into a massive demonstration of freedom from "schools and rules" and has become the most popular public event annually celebrating the end of school year. Crowds of about one million people are treated to a wide variety