Sail Performance: Theory and Practice

This is the successor to the author's previous book Sailing Theory and Practice, published over 30 years ago, and takes into account the many developments which have taken place in sail performance since then.

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.

The performance of any sailing craft largely depends 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, sail shape, sail setting, the hull, angle of heel, wind gradient, and steadiness of the wind.

From wind tunnel tests which he has conducted, Tony Marchaj describes how these factors affect sail power and why certain rigs are superior in power and efficiency to others. The tests also indicate where improvements in efficiency may be made, particularly when freed from the constraints imposed by the arbitrary limitations of the racing rules.

Professor Marchaj compares a number of different types of rig--Bermudan, lateen, sprit, gunter, dipping lug and Polynesian crab claw--and concludes that the Bermudan rig, which dominates the contemporary sailing scene for racing and cruising, is by no means the best available.

This major work makes a significant contribution to our understanding of the factors which contribute to an efficient sailing rig, and is a landmark in modern thinking on the subject.

"There can't be a yacht designer around who doesn't know Marchaj's Sailing Theory and Practice: this is the modern version of a classic."--Yachting World

"By a master of wind tunnel and test tank research . . . a unique publication."--Multihull International

"A classic."--Royal Naval Sailing Association

"Exceptional value . . . should be on the bookshelf of very serious amateur and professional sailor."--Nautical Magazine

"This is one of the most authoritative works around."--Yachting World

Selected Contents

Part 1: Rating Formulae and Speed Performance

Speed and size

Seakindliness and seaworthiness

Speed performance factors

How fast is fast?

The drive towards ultimate speed

Part 2: Aerodynamics of Sails

How and why an aerodynamic force is produced

Distribution of pressure over sails

Effects and measurement of aerodynamic forces

Aerodynamic drag of the sail

Apparent wind structure

Sail camber and sail shape

Sail power of various rigs

The effect of wind gradient

Sail-hull interference

Wing sails

Sail interaction

Centre of effort

Cut, set and defects of sails

Part 3: Steady and Unsteady Wind

The significance of barometric depressions

True wind structure

Local winds

Microbursts

Pumping--a legitimate technique?

Rolling downwind

Katzmary effect