Sail Performance, based on C A Marchaj`s classic Sailing Theory & Practice, has established itself as the standard work on the subject and is now acclaimed as a milestone in sailing literature. From wind tunnel tests which he has conducted, Tony Marchaj describes how the factors of wind speed, sail area, sail shape, sail setting, the hull, angle of heel, wind gradient and steadiness of the wind all affect sail power, and why certain rigs are superior in power and efficiency to others. Sail Performance is a major work which is acclaimed for its analysis of the factors that contribute to an efficient sailing rig. `Should be on the bookshelf of every serious amateur and professional sailor` Nautical Magazine