Sails of Silver now sported the same line-up that had brought it to the height of its success, "Sails of Silver" has often been seen as embodying a different spirit from their classic albums of the 1970s. Prior to "Sails of Silver", the band had always performed songs written by other people, predominantly traditional songs, but also a few 20th century pieces, such as the two Brecht songs on "Storm Force Ten". But on this album they included several songs they had written themselves, including "Let Her Go Down" and "Senior Service". This was the beginning of a trend that continues down to
Forces on sails astern, so drag force on a downwind sail becomes substantially a function of area and wind speed, approximated as follows: formula_15 Sail design relies on empirical measurements of pressures and their resulting forces on sails, which validate modern analysis tools, including computational fluid dynamics. Modern sail design and manufacture employs wind tunnel studies, full-scale experiments, and computer models as a basis for efficiently harnessing forces on sails. Instruments for measuring air pressure effects in wind tunnel studies of sails include pitot tubes, which measure air speed and manometers, which measure static pressures and atmospheric pressure (static pressure in undisturbed flow).