Sail Performance

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Sail Performance

Techniques to Maximize Sail Power

C. A. Marchaj

This volume replaces Marchaj's classic Sailing Theory and Pactice, published 25 years ago, and offers new information on, rig design, sail construction and trim, wind-sail interaction, and the structure of the wind. The performance of any sailing craft depends largely on the power of the available sail--how the rig uses the wind and turns it into a useful driving force. But sail forces are determined by a multitude of factors, including wind speed, sail area and shape, and steadiness of the wind, among others. From wind-tunnel tests that he has conducted, Marchaj describes how these factors affect sail power and why certain rigs are superior in power and efficiency--concluding that the Bermuda, or marconi, rig is by no means the best available. This major work is an accessible, nonmathematical treatment of the subject and marks a turning point in modern thinking in the arena.

** Review **

Part I: Some Remarks About Yatch Evolution, Rating Formulae and Speed Performance: Speed and Size. The Traditional Cruising Yacht Concept. Reaction Against Unhealthy Fast Boats. Flat-Out Racer Concept. Seakindliness and Seaworthiness. Speed Performance Factors. How Fast Is Fast. Weather Factor. Drive Towards Ultimate Speed. Reference and Notes Part 1. Part II: Aerodynamics of Sails: Introduction. How and Why an Aerodynamic Force is Produced. Distribution of Pressures Over Sails. The Effects of Aerodynamic Forces. Measurement of Aerodynamic Forces. Aerodynamic Drag of the Sail. Apparent Wind Structure. Dependence of the Optimum Angle of Sail Incidence Upon Heading Angle and Wind Strength. The Importance of Sail Camber. Importance of Sail Planform. Sail Power of Various Rigs. Wind Gradient Effect and Sail-Hull Interference. Wind-Sail and Other Conventional Rigs. Sail Interaction. Some Remarks About Sail Trim. Center of Effort. Some Remarks About Cut, Set and Defects of Sail. Part III: Wind--Steady and Unsteady: The Significance of Barometric Depressions. True Wind Structure. Local Winds. The Wind Over a Regatta Course. Microburst. Pumping--A Legitimate Sailing Technique? Sailing Down-Wind (Rolling). Katzmayr Effect. References and Notes, Part 3. Appendices 1 and 2. Beaufort Scale of Wind Speed. Conversion Tables.