Steve Colgate - Performance Sailing and Racing

Copyright 2012 by steve Colgate. All rights reserved. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of the publisher.

ISBN: 978-0-07-179345-2
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This book is for sailors who know the basics and want to fine-tune their sailing skills. It is for those who want:

to sail their boats faster, better, and more efficiently;

to overcome the fear of flying a spinnaker;

to know what to do in emergencies; and,

to get more satisfaction from sailing than ever before

whether they are embarking on a day sail, taking a weekend cruise, or entering their first or their fiftieth race.

To sail fast usually means to sail well. Speed means precision of technique. Precision of technique creates self-confidence and personal satisfaction.

A boats speed depends largely on how its sails are set and trimmed. And there are an infinite variety of sail types, shapes, and materials. Todays sails are made of many materials, including Dacron, a material that stretches constantly as the forces on it change. With the invention of Kevlar and spectrasail material that doesnt stretchsails are now being built with a set shape, and it is not as necessary to control the stretch as before but sail shape understanding is still critical to performance sailing. Forces affecting sails include wind-strength increases or decreases, and also pressure changes on the sails when the boat slows down as it plows into waves or speeds up when it is surfing or sailing in smooth water. As you sail in these conditions you can control this stretch, and thereby the shape of the sail, using numerous adjustment devices. Well get to those in a bit, but before we look at the specifics, lets discuss the desirable end result.

Sails power a sailboat much like an engine powers a car with a manual transmission. When a car is moving slowly, uphill, or over a bumpy terrain, you keep it in low gear to add power. As it picks up speed and the ground levels, you shift to a higher gear. When the car is moving fast on a smooth road, you shift to an even higher gear. So, too, with a sailboat. Full sails are the low gear and flat sails are high gear. When seas are heavy and the boat is sailing slowly, almost stopping as it hits each wave, the sails need power. Full sails are the answer. In smooth water and high winds when the sailboat is moving fastest, flat sails are desirable.

The mainsail is a very versatile sail and can be made flat or full at will. But, you may ask, what is a full sail or a flat sail? The terms are relative. A sail is flatter or fuller than another based on the relationship of the maximum depth of the curvature (the draft) to the distance from luff to leech (the chord). shows the cross section of a mainsail. An imaginary line drawn from luff to leech is the chord. A line drawn perpendicular to the chord at the point where the sail is the greatest distance from the chord is the draft or camber. The camber-to-chord ratio is the relation of this distance to the chord, usually expressed as a percentage. If the chord is 120 and the draft of camber is 12 deep, the camber-to-chord ratio is 10 to l or 10%. Sails can be used effectively as flat as 5% or as full as 20% at the center of effort, depending on the class of boat and the sailing conditions. The draft varies at different heights up the sail.

Figure 1-1. Draft is the maximum depth of the sail measured from the chordan imaginary straight line from luff to leech. Here its too far forward.

Of even more importance is the position of maximum draft in the sail. shows the maximum draft aft, near the leech of the mainsail. As the breeze freshens, sail material stretches and the draft tends to move aft toward the leech. This movement will cause the battens to cock to windward in the mainsail and produce a less efficient airfoil. Increased tension on the luff can keep this movement to a minimum.