The Science of Sailing: Part 5
Sailing Fundamentals, Foils and Foil Sections, Hull Forms, and “Australia II”


(note from Peter)

When I decided how to divide the material I wanted to cover into parts, chapters, and sections in 2013, I planned to devote Part 5 to foils and foil sections. Part 6 was to contain a compendium of lift and drag data for sails, hulls, keels, and rudders. Part 7 was to cover force and moment equilibrium and the results thereof for the detailed calculation of transverse, longitudinal, and directional stability. Part 8 was to be dedicated to the methods for determining the performance of sailing yachts (by VPP, CFD, and model tests). Finally, Part 9 was to cover descriptions of different sail configurations and hull forms in relation to their performance and a description of the America’s Cup projects I was involved in. As I am writing this, 10 years later, I realize that a nine-book series was overly ambitious. Each of these books requires, on average, some 3,000 hours to write. While I might be given the necessary years to complete the remaining 4 volumes, my interest in doing so has waned because of having embarked on a late career as an author of fiction novels. I have described the quandary I found myself in in 2021, when I wrote my first novel, elsewhere on this site. To cut a long story short, I have decided that Part 5 is to be the last of the “Science of Sailing” series of books. It will encompass force and moment equilibrium, the nature, detection, and significance of free moments, foils and foil sections, hull forms, and the Australia II project.

Part 5 commences with Chapter 10, devoted to coordinate systems, axis rotations, and the determination of the attitude of a sailing vessel at some angle of heel, running trim, and leeway to wind and water vectors. Chapter 11 covers force and moment equilibrium—specifically, the forces and moments involved and their location, magnitude, and direction. Free moments originate from force-couples. They play a major role in determining the location of the resultant force, particularly when the flow exhibits boundary layer separation. The treatment of free moments is found in Chapter 12.

The lift and drag of foil sections are covered in Chapter 13. Particular attention is given to the relation between foil section geometry and the lift and drag forces exerted by the flow over a range of angles of attack. Foil sections are assumed to possess an infinite span. The span of foils such as keels and rudders is finite, however, and the flow around the tips of wings and foils affects lift and drag significantly—increasingly as the span, in relation to the length of the chord, decreases. Chapter 14 addresses this effect of finite span.

The developing hull form for what I have termed the “intermediate-Froude range of speeds” is described in Chapter 15. Besides a historical account of how the best hull forms came to be developed, this chapter provides an overview of the relative performance in terms of drag of the various hull forms considered. Hull forms for speeds associated with Froude numbers (based on waterline length) exceeding 1.0 are not considered, as this is the regime of hard-chine planing hulls, not adopted for sailing craft. The material on hard-chine hulls included in this chapter is for defining the difference in drag in this Froude number range with round-bilge hulls. Such hulls, irrespective of whether they are round bilge or hard chine, are often incorrectly referred to as “semi-displacement” or “semi-planing hulls”.

Finally, in Chapter 16, I have, for the first time in 40 years, described in detail how the America’s Cup was won in 1983 and my role therein. This chapter differs from previous chapters because of wanting to include descriptions of the shenanigans between the New York Yacht Club and the Australia II team. Many books and articles have been written about the non-sailing aspects of that event, but none have covered it completely, and some have been misled about what actually happened.

Blurb text

This book is Part 5 of a larger work entitled “The Science of Sailing”. Its subject is the science behind sailing and the naval architecture governing the performance of sailing craft, with particular reference to sailing yachts. Sailing craft are wholly dependent on the wind for their propulsion and are unique in the sense that fluid dynamics plays more than a vital role in their design. Both aerodynamics and hydrodynamics, the science of the motion of air and water around bodies, determine the speed potential of a sailing vessel.

All the important aspects pertaining to the behaviour and performance of sailing craft are described in the collected parts of this work. The arrangement of this material steadily expands the subject, chapter by chapter. The science required to understand and follow the reasoning that lies at the base of how some specific designs evolved is presented before describing those designs.

Part 5 has been allotted to four distinct topics. The first of these is associated with force- and moment equilibrium and free moments—the basis for the calculation of the performance of sailing craft. The second deals with the lift, drag, and moment properties of foils and foil sections such as keels and rudders. The third covers the design and performance of different hull forms, and the fourth is my personal account of the design of “Australia II”, the yacht that won the America’s Cup in 1983.

Some topics covered in other volumes are:

  • Basic principles and the attainable speed under sail (Part 1);
  • The origin and nature of fluid-dynamic lift and drag (Part 2);
  • Phenomena and drag originating from the boundary layer (Part 3);
  • Phenomena and drag originating from the air-water interface (Part 4).

Part 5 is the last book in the series.

Peter (in Dutch, Pieter) van Oossanen holds an M.Sc. and Ph.D. from Delft University of Technology. He has received prizes and awards for his achievements in naval architecture and hydrodynamics. His writings include more than 100 papers on specialist topics in the field of ship science.

Purchase information

The book is published by Van Oossanen Academy Publishers, and produced by Drukkerij AMV b.v. in Lunteren, the Netherlands.  It has a hard cover. The book comprises 448 pages. Its ISBN number is 978-90-827682-6-8. The book is sold by all major bookshops. It can also be ordered directly from Van Oossanen Academy Publishers. The following link is provided for that purpose.