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Your First Sailing HandbookPart 1: The BasicsVedran Bobanac

Published byBOBLab d.o.o., Zagreb

Cover design byKreativne ovcice / Creative Pink Sheep

Reviewed by• Damir Milos, MSc in Philosophy,

senior sailing instructor at Academia Navalis Adriatica (ANA)• Zivko Matutinovic,

senior sailing instructor at Academia Navalis Adriatica (ANA)• Nenad Bobanac, PhD in Naval Architecture• Robert Grubisa, MSc in Naval Arhitecture,

radio sailing boats designer, builder and sailor• Ksenija Zaninovic, PhD in Physics (Meteorology)• Marko Vucetic, BSc in Physics (Meteorology)

Revised byTomislav Skracic, MA,

senior English lecturer at Faculty of Maritime Studies in Split

Written and illustrated byVedran Bobanac, PhD in Electrical Engineering

First edition published May 2009Second edition published March 2020© 2009 Vedran Bobanac

This handbook was typeset using the LATEX typesetting system created by LeslieLamport, the memoir class created by Peter R. Wilson, with pedersen chapterstyle, and glossaries package created by Nicola Talbot.All the illustrations were drawn in Inkscape vector graphics editor.

ISBN 978-953-57746-3-1

Disclaimer

This e-book has been written in good faith, with the aim to educate and providetrustworthy information about sailing. Although the content has been thoroughlychecked, it may contain mistakes and omissions. Any action you take uponthe information from this e-book is strictly at your own risk, and the author willnot be held responsible for any damages, injuries and/or any other accidents inconnection with the use of this e-book. The author advises readers to take fullresponsibility for their safety and know their limits.

This e-book is licensed for your personal use only. This e-book may not be re-soldor given away to other people. If you would like to share this book with anotherperson, please purchase an additional copy for each person. If you’re readingthis book and did not purchase it, then please purchase your own copy. Thankyou for respecting the hard work of this author.

Once you get splashed by the sea-water under sails, you won’trinse off the salt until your dying day.

Joza Horvat (1915-2012),Croatian writer and sailor

Preface

This handbook deals with the basics of modern sailing. It is intended primarilyto those interested in recreational sailing on cruising boats, who have none orlittle sailing experience. Moreover, all the fundamental topics are treated system-atically and in-depth, which makes the handbook suitable for more experiencedsailors as well. I tried to be concise and present all the information by usingsimple language and numerous original illustrations.

The handbook was originally written as supporting literature for the basicsailing course at Academia Navalis Adriatica (ANA), the Croatian school of sailingand nautical skills. The first edition was published in 2009 and the second edition,extended and improved, stands before you. The structure of the ANA’s basiccourse has been maintained and the content is therefore divided into days, whichmeans that the reading is easily combined with practice at sea. I believe thatthis is important because sailing cannot be learned solely from books. All thetheory is not worth much without practice and experience at sea. On the otherhand, some theoretical background is necessary for sailing to be safe and fun.This handbook is a practical reading, but it also provides all the fundamentaltheoretical information.

I would like to thank my reviewers and revisor who invested their time and helpedme improve the content with their valuable advice.

I am also very grateful to my family for all of their help and support whilepreparing this handbook, but most of all I am grateful to my parents for making itpossible for me to enter this wonderful world of sailing as a boy.

Sailing really is a specific activity. You may think of it as a sport or a science,while for a lot of people it is a way of living, a philosophy, an art. I think that sailingis all that and above all, a beautiful way to connect with the nature and otherpeople. It is no wonder that life is often compared with sailing... as the beautyof sailing lies in traveling, not just in reaching the destination. I always seek thatbeauty in my everyday life.

Zagreb, March 2020

Author

v

Contents

1 Day One 11.1 Types of Boats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Parts of a Boat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.3 Points of Sailing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.4 How the Boat Sails . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.5 Positions of the Crew . . . . . . . . . . . . . . . . . . . . . . . . . . 101.6 Handling the Sails . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1.6.1 Preparing the Sails . . . . . . . . . . . . . . . . . . . . . . . 111.6.2 Hoisting the Sails . . . . . . . . . . . . . . . . . . . . . . . . 131.6.3 Lowering the Sails . . . . . . . . . . . . . . . . . . . . . . . 14

2 Day Two 172.1 Sailing a Course . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172.2 Parts of Sails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182.3 Trimming the Sails . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2.3.1 Generally about Trimming and Steering . . . . . . . . . . . 202.3.2 Trimming the Jib . . . . . . . . . . . . . . . . . . . . . . . . 222.3.3 Trimming the Mainsail . . . . . . . . . . . . . . . . . . . . . 25

2.4 Reefing and Changing the Sails . . . . . . . . . . . . . . . . . . . . 262.4.1 Changing the Jib . . . . . . . . . . . . . . . . . . . . . . . . 282.4.2 Reefing the Mainsail . . . . . . . . . . . . . . . . . . . . . . 29

2.5 Roller Furling and Lazy Jacks . . . . . . . . . . . . . . . . . . . . . 30

3 Day Three 333.1 Tack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333.2 Avoiding Collision . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.2.1 Boat Categories . . . . . . . . . . . . . . . . . . . . . . . . 383.2.2 Rules for Power Boats . . . . . . . . . . . . . . . . . . . . . 393.2.3 Rules for Sailing Boats . . . . . . . . . . . . . . . . . . . . . 403.2.4 Remarks on Collision Avoidance . . . . . . . . . . . . . . . 41

3.3 Stopping the Boat . . . . . . . . . . . . . . . . . . . . . . . . . . . 423.4 Apparent Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4 Day Four 454.1 Gybe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454.2 Anchoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

4.2.1 Choosing an Anchorage . . . . . . . . . . . . . . . . . . . . 514.2.2 Anchoring Technique . . . . . . . . . . . . . . . . . . . . . 52

4.3 Meteorology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544.3.1 Weather Basics . . . . . . . . . . . . . . . . . . . . . . . . . 544.3.2 Winds in the Adriatic . . . . . . . . . . . . . . . . . . . . . . 56

viii

5 Day Five 615.1 Man Overboard (MOB) . . . . . . . . . . . . . . . . . . . . . . . . . 61

5.1.1 Recovery under Sails . . . . . . . . . . . . . . . . . . . . . 615.1.2 Recovery under Power . . . . . . . . . . . . . . . . . . . . . 64

5.2 Tuning the Boat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 655.2.1 Turning Forces . . . . . . . . . . . . . . . . . . . . . . . . . 655.2.2 Tuning the Sails . . . . . . . . . . . . . . . . . . . . . . . . 715.2.3 Rig Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

A Appendix A: Basic Sailing Skills 79A.1 Knots Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79A.2 Tying the Knots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

A.2.1 Bowline Knot . . . . . . . . . . . . . . . . . . . . . . . . . . 82A.2.2 Clove Hitch . . . . . . . . . . . . . . . . . . . . . . . . . . . 82A.2.3 Reef Knot . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83A.2.4 Sheet Bend . . . . . . . . . . . . . . . . . . . . . . . . . . . 83A.2.5 Cleat Hitch . . . . . . . . . . . . . . . . . . . . . . . . . . . 84A.2.6 Figure of Eight . . . . . . . . . . . . . . . . . . . . . . . . . 85A.2.7 Fisherman’s Bend . . . . . . . . . . . . . . . . . . . . . . . 85A.2.8 Round Turn and Two Half Hitches . . . . . . . . . . . . . . 86

A.3 Coiling Ropes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86A.4 Folding the Sails . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

A.4.1 Folding the Jib . . . . . . . . . . . . . . . . . . . . . . . . . 88A.4.2 Folding the Mainsail . . . . . . . . . . . . . . . . . . . . . . 90

A.5 Berth – Leaving and Returning . . . . . . . . . . . . . . . . . . . . 92

B Appendix B: Boat Dynamics and Stability 95B.1 Aerodynamics and Hydrodynamics . . . . . . . . . . . . . . . . . . 95

B.1.1 Forces Balance and Interaction . . . . . . . . . . . . . . . . 95B.1.2 Forces Generation . . . . . . . . . . . . . . . . . . . . . . . 97

B.2 Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100B.3 Turning Moments Generation . . . . . . . . . . . . . . . . . . . . . 101

Glossary 105

References 119

Author’s Biography 121

ix

1Day One

1.1 Types of Boats

There are many different types of sailing boats, for instance see Fig. 1.1. A boatwith one mast is called a sloop. A boat with two masts, the after mast beingshorter, is called a ketch. A boat with two masts, the after mast being taller, iscalled a schooner.

SLOOP KETCH SCHOONER

Figure 1.1: Types of boats

Furthermore, boats can differ in the number of hulls. Boats with two hulls arecalled catamarans and with three hulls trimarans.

The configuration of masts and sails on a boat is called a rig. The Bermudarig is by far the most popular type of rig on modern sailing boats. The Bermudarig is characterized by triangular sails and it is a type of fore-and-aft rig. The maincharacteristic of fore-and-aft rigged boats is that they can sail upwind much betterthan the traditional square rigged boats. This is because fore-and-aft rig consistsof sails that are set along the centerline (longitudinally), opposed to the squarerig where sails are set perpendicular to the centerline (transversely).

In this handbook the most widespread modern type of a sailing boat is con-sidered and that is the Bermuda rigged sloop.

1

2 1.2 Parts of a Boat

1.2 Parts of a Boat

The sloop normally sails with two sails: one mainsail and one foresail that iscalled a jib (see Fig. 1.2). Larger boats use an inboard engine, while smallerboats (usually shorter than 25 feet) may have an outboard engine. The enginedrives the propeller providing thrust when sails are not used.

JIB MAINSAIL

Figure 1.2: Sloop’s principal sails

A typical sloop is shown in Fig. 1.3. The front part of a boat is called the bow,while the rear part is called the stern. A cockpit is a working area, towards thestern of a boat, from which the boat is steered and controlled. A boat is steered byturning the tiller which results in turning the rudder, since these two are connectedwith a shaft. When the rudder is turned off the centerline it makes the boat turnleft or right. On bigger boats a steering wheel is used instead of a tiller. Forestay,backstay and shrouds are steel wires or rods that support the mast (collectivelycalled standing rigging).

Some important lines are drawn in various colors in Fig. 1.3 (see the legendwhere colors tell you which line is which). Halyards and topping lift are led to thetop of the mast, then down through the mast; they exit the mast near the deck andare then directed to the cockpit as shown in Fig. 1.3. Similarly, outhaul is led fromthe rear end of the boom, through the boom towards the mast and then to thecockpit. The main halyard and outhaul are used to stretch the mainsail, while thejib halyard is used for hoisting the jib. The topping lift supports the boom whenthe mainsail is not hoisted and it is run in the same way as the main halyard.Mainsheet and vang are used to control the boom and the mainsail during sailing− but more on that later. All the above mentioned lines are collectively calledrunning rigging.

Traveler and jib car are adjustable blocks running along tracks, through whichsheets (mainsheet and jib sheets) are attached to the deck (see Section 5.2.2 foradjustment details).

Remark: The term rig comprises mast, boom, sails and rigging (both standingand running). A Bermuda rigged sloop may have different rig configu-rations (more on this topic in Section 5.2.3).


JIB HALYARD

OUTHAUL

MAIN HALYARD

TOPPING LIFT

MAINSHEET

VANG

BACKSTAY

FORESTAY

MAST

KEEL

HULL

RUDDER

STANCHION

BOOM

GOOSENECK

WATERLINE

BOW STERN

SHAFT

PROPELLER

WINCHES

SPREADERS

TILLER

SHROUDS

LIFELINE

PULPIT CLUTCHES

JIB CAR

TRAVELER

(a) Side and rear view

WINCHESROPECLUTCHES

MAST

BLOCKS

TILLER

(b) Top view

Figure 1.3: Parts of a boat


All the lines running from the mast to the cockpit are led through the system ofblocks and then through rope clutches, so that they can be put on the winches.Each line has its own clutch and each clutch has two positions: opened andclosed. When the clutch is opened, the line can move freely in both directions.When the clutch is closed, the line can be pulled in only one direction (towardsthe cockpit), while the other direction is blocked.

Winches facilitate tightening of the lines when they are under tension. Linesmust always be put on the winch in the clockwise direction with a suitable numberof turns. The stronger the force on the line, the more turns should be put on thewinch. When the tension in the line becomes too strong to be pulled by hand, ahandle is used.

Winches can be standard or self-tailing (Fig. 1.4). They are both operated inthe same way, except when using a handle. In this case, standard winches arenormally operated by two persons, i.e. one is tailing (pulling the free end of theline) while the other is turning the handle. On the other hand, self-tailing winchesallow simple one-person operation, since they have self-tailing jaws. After the linehas been put in these jaws, it is tailed automatically as the handle is being turned.

HANDLE

(a) Standard winch

JAWS

HANDLE

(b) Self-tailing winch

Figure 1.4: Types of winches

5 1.3 Points of Sailing

1.3 Points of Sailing

The direction in which the boat is sailing is usually described as the angle be-tween the boat’s centerline and the wind direction. These angles are called pointsof sailing. The boat can sail in every direction except in a range of directions thatpoint into the wind too much. Directions that cannot be achieved are limited withtwo straight lines that are set at the angle of approximately 90◦ (the exact angleis different for different boats).

Remark: The direction that cannot be achieved is marked red in Fig. 1.5. The 90◦

angle is marked with a standard symbol: an angle curve and a smalldot − . See also Fig. 1.6.

WIND

CLOSE HAULED (CLOSE HAULING)

BEAM REACH (REACHING)

BROAD REACH (BROAD REACHING)

RUN (RUNNING)

Figure 1.5: Points of sailing

Basic maneuvers in sailing are (see Fig. 1.7):• Tack• Gybe• Luff up• Bear away.

DIRECTIONOF SAILINGMAINSAIL

JIB

Figure 1.6: Boat top view

6 1.3 Points of Sailing

During tack and gybe maneuvers the boat is changing tack which means thatsails are moving from one side of the boat to the other.

Luff up is a maneuver where the boat is turning towards the wind. When theboat is luffing up, sails should be pulled in by the crew.

Bear away is a maneuver where the boat is turning away from the wind. Whenthe boat is bearing away, sails should be eased out by the crew.

WIND

GYBE

TACK

LUFFUP

BEARAWAY

LUFFUP

BEARAWAY

Figure 1.7: Basic maneuvers

The following terms are used to describe sides of the boat (see Fig. 1.8):• Sides of the boat regardless of the wind:

◦ Port side − left side of the boat (when facing the bow)◦ Starboard side − right side of the boat (when facing the bow)

• Sides of the boat relative to the wind:◦ Windward side − side of the boat closer to the wind◦ Leeward side − side of the boat away from the wind

• Tack of the boat refers to the side from which the boat is getting the wind:◦ The boat is sailing on a port tack − the boat is getting the wind over

the port side (the mainsail is on the starboard side)◦ The boat is sailing on a starboard tack − the boat is getting the wind

over the starboard side (the mainsail is on the port side).

Remark 1: The position of the mainsail determines whether the boat is sailing onport or starboard tack.

Remark 2: It is important to understand the difference and avoid confusion be-tween tack (maneuver) and tack on which the boat is sailing (overwhich side the boat is getting the wind − port or starboard).

7 1.4 How the Boat Sails

PORTSIDE

STARBOARDSIDE

CENTERLINE

(a) Regardless of the wind

STARBOARDTACK

PORTTACK

WIND

WINDWARD SIDE

WIND

LEEWARD SIDE

(b) Relative to the wind

Figure 1.8: Sides of the boat

1.4 How the Boat Sails

It is easy to understand how a boat sails in run point of sailing. The wind fills thesails and simply pushes the boat. But how can the boat move forward in reachingand close hauling? One simple answer would be that (in these points of sailing)sails work like wings of an airplane.

WIND

HIGHER PRESSURE

LOWER PRESSURE

Figure 1.9: Airflow over sails of a close hauled boat

23 2.3 Trimming the Sails

GOOD TRIM

WIND

Figure 2.7: All the tell-tales streaming horizontally

TURN TOWARDS THE WIND OREASE THE JIB SHEET

WIND

Figure 2.8: Leeward tell-tales flapping

TURN AWAY FROM THE WIND ORPULL THE JIB SHEET

WIND

Figure 2.9: Windward tell-tales flapping

29 2.4 Reefing and Changing the Sails

2.4.2 Reefing the MainsailReefing should be performed in close hauling (or between closehauling and reaching). That is because the mainsail can be de-powered only in these points of sailing. Therefore, reefing in otherpoints of sailing (from reaching to run) should be avoided. While thecrew is reefing the mainsail (or releasing the reef), the helmsmankeeps the boat on course, by sailing only with the jib.

WIND

This is a procedure for reefing the mainsail (the same for 1st and 2nd reef):1. Crew prepares. No. 1 is by the mast and No. 2 is on the mainsheet. The

boat is sailing a close hauled course.2. Depower the sail. No. 2 eases the mainsheet and No. 3/4 opens the vang

clutch. The mainsail is now flapping.3. Lower the sail and attach the reef’s

tack. No. 3/4 opens the main hal-yard clutch and releases the halyard,while No. 1 pulls down the luff of themainsail until the reef’s tack can beplaced in the hook on the gooseneck.

4. Tighten the halyard. No. 3/4 closesthe main halyard clutch and tightensthe halyard with the handle, whileNo. 1 ensures that the reef’s tack isattached to the hook.

5. Tighten the reef line. No. 3/4 putsthe reef line on the winch and pulls it,first by hand and then with the han-dle, until the reef’s clew reaches theboom. In order to take the pressureoff the mainsail while tightening thereef line, the boom may be lifted byusing a topping lift.

6. Power the sail. No. 2 pulls in themainsheet, while No. 3/4 tightens thevang and makes sure that the top-ping lift is loose.

7. Tie the reefed part of the sail. Theremaining part of the mainsail (whichhas been reefed) is now hangingdown from the boom (see Fig. 2.16),so it has to be folded (rolled) and thentied with ropes. The ropes should bepulled between the foot of the main-sail and the boom, not around theboom.

Figure 2.16: Reefing the mainsail

46 4.1 Gybe

The tasks of each crew member during gybe are given in the sequel. Textualdescriptions of tasks relate directly to Fig. 4.3, which illustrates crew positionsand actions in the gybe maneuver.

Crew tasks during gybe

No. 5• By saying: ”Ready to gybe” he tells the crew to prepare for the maneuver.• When everyone is ready, he checks again that the boat is in broad reaching

and as he starts turning the boat he says: ”Gybe”.• He turns the boat by turning the tiller to windward (or on bigger boats, by

turning the steering wheel to leeward). He must not turn the boat too fast(he may even keep the boat in run position for a while), in order to allow No.2 enough time to pull in the mainsheet (see below).

• When the boat is on a new course (broad reaching), he stops turning theboat by putting the tiller back in the middle of the boat (or by turning thewheel) and after that he crosses on the other side of the boat (new windwardside) and sits down in a position for steering.

• In stronger wind he should put the tiller (or wheel) in the middle earlier(sometimes immediately after the boom has crossed the centerline). This isbecause, after the mainsail is gybed, the boat will have tendency of turningtowards the wind.

No. 2• On ”ready to gybe” he makes sure that the mainsheet is free of knots and

that there is nobody standing on it.• When the boat is in run position (jib is hanging down), he pulls the main-

sheet until the boom is almost aligned with the centerline of the boat. Ifthe wind is not too strong, he can start pulling the mainsheet before runposition.

• He observes the leech of the mainsail and when he sees that the wind hascaught the mainsail from the other side, he lets the sheet out of his hands.The wind pushes the mainsail to a new leeward side.

• If the wind is strong, the mainsail will be excessively pushed against thespreaders, so he has to pull back the mainsheet in order to put the mainsailin the proper position.

No. 3• On ”ready to gybe” he unfixes the active jib sheet and holds it tight in his

hands (with enough turns on the winch so that the sheet does not slip).• He does not release the jib sheet like in tack maneuver, because the jib

could wrap around the forestay.• When the boat is in run position, he pulls the jib sheet a little bit (about 1

meter of line) and then releases by taking it completely off the winch.• As the jib is being pulled to the other side of the boat, he makes sure that

the released jib sheet does not get stuck somewhere in the cockpit.

47 4.1 Gybe

WIND

3

5

2

1

4

3

5

2

1

4

3

5

2

1

4

4

52

1

3

Figure 4.3: Crew tasks during gybe

71 5.2 Tuning the Boat

5.2.2 Tuning the Sails

Halyard(s)

When hoisting the sails, tension of halyards is adjusted in accordance with thecurrent wind strength. The stronger the wind, the higher the tension. If strengthof the wind increases during sailing, the sails (both the jib and the mainsail) mayget curves at the luff which is a sign that the halyard is under-tensioned. A seriesof parallel creases at the luff may also be visible, as seen in Fig. 5.12a. In thissituation the airflow at the luff is disturbed and the halyard should be tightened,but only after releasing the sheet. The halyard must never be tightened while thesail is under power!

(a) Under-tensioned halyard (b) Over-tensioned halyard

Figure 5.12: Halyard tension

If strength of the wind decreases during sailing, the halyards may become over-tensioned. This may not always be recognized if the boat is sailing a close hauledcourse (Fig. 5.13a), but as the boat bears away this becomes noticeable as shownin Fig. 5.13b (disturbed airflow at the luff of the jib). Long gathers along the luffwill also appear (Fig. 5.12b shows the jib, but the same applies for the mainsail).In this situation the halyard(s) should be eased a bit.

WIND

(a) Close hauling

WIND

(b) Reaching

Figure 5.13: Noticing over-tensioned halyard

82 A.2 Tying the Knots

A.2.1 Bowline Knot

4321 5

Figure A.5: Tying the bowline knot

In step 2 a crossing turn is made with enough of the working end left. The keymoment is when the working end is passed through the crossing turn in step3 – see that the working end and the standing part must be on the oppositesides of the upper part of the crossing turn. Passing the working end in theopposite direction in step 3 would be a mistake. The knot is tightened by pullingthe standing part and doubled working end simultaneously in step 5, i.e. standingpart is pulled to one side while working end (plus the part of the line next to it) ispulled to the other side.

Bowline knot actually makes a loop at the end of the line. The size of the loopdepends on the line’s function. For instance, if the knot is tied to the sail (e.g. ahalyard) the loop should be small (shorter working end in step 2). If the knot ismade on the dock line to be put on the bollard, the loop should be big (longerworking end in step 2). However, the size of the crossing turn (made in step 2)can always be the same – big enough for the working end to pass through it twice.

Remark: Always leave the working end long enough in step 5, so that it cannotslip out.

A.2.2 Clove Hitch

1 5432

Figure A.6: Tying the clove hitch

The knot is tightened by pulling the standing part and the working end simultane-ously in step 5. Note that the working end is always passed around the pole inthe same direction, i.e. there is no ”breaking” of the line.

BAppendix B: Boat Dynamics and Stability

This appendix provides physical explanations of forces that act on a boat duringsailing. It can be said that this appendix extends Sections 1.4 (How the BoatSails) and 5.2.1 (Turning Forces).

B.1 Aerodynamics and Hydrodynamics

B.1.1 Forces Balance and Interaction

All the forces on the part of the boat above the waterline (created by the windblowing across the sails, rig and hull) can be considered as one force (totalaerodynamic force) acting in a single point which is called the center of effort(CE). This force has already been discussed in Section 1.4, where it is referredto simply as the total force. The total aerodynamic force is dominantly created bythe sails, so the position of CE results from the boat’s current sail configuration.

All the forces on the underwater part of the boat (created by the boat movingthrough the water) can be considered as one force (total hydrodynamic force)acting in a single point which is called the center of lateral resistance (CLR).The position of CLR is affected by the construction of the boat’s underwater part(design of the hull, keel and rudder).

WIND CLOSE HAULINGLATERALRESISTANCE

TOTAL FORCE(HYDRODYNAMIC)

LONGITUDINALRESISTANCE

TOTAL FORCE(AERODYNAMIC)

DRIVINGFORCE

SIDEWAYSFORCE

CENTER OF EFFORT (CE)

CENTER OF LATERAL RESISTANCE (CLR)

Figure B.1: Aero- and hydrodynamic forces

When the boat is sailing steadily (at steady speed and steady heel) all the forcesare in balance. This means that the total aerodynamic force has the same amountand opposite direction from the total hydrodynamic force. The same goes for thecomponents of these two total forces (see Fig. B.1). Driving force (aerodynamic)has the same amount and opposite direction from the longitudinal resistance(hydrodynamic), while sideways force (aerodynamic) has the same amount andopposite direction from the lateral resistance (hydrodynamic).

95

104 B.3 Turning Moments Generation

Boat Trim

Boat trim implies changing the position of the center of lateral resistance (CLR)and it can therefore be explained in the same way as sail balance. The positionof CLR is changed by moving the weight back and forth (typically the weight ofthe crew), thus making either stern or bow more immersed.

However, the position of CLR cannot be changed as easily as the position ofcenter of effort (CE) and that is why boat trim is not as efficient as sail balance.Namely, referring to boat trim, turning moment (caused by the separation ofsideways force and lateral resistance) is not very strong because the longitudinalseparation between CLR and CE is not very expressed (see Fig. B.14).

Boat trim has more effect on very small cruisers and especially on dinghieswhere the weight of the crew is comparable to the weight of the boat, whichmeans that CLR can be moved to a greater extent.

WIND WIND

Figure B.14: Boat trim

Remark: Some handy explanations and comparisons about CE and CLR can befound in [24, 25].

Glossary

# | A | B | C | D | F | G | H | I | J | K | L | M | O | P | R | S | T | V | W

#

1st reefWhen the 1st reef is set, the mainsail has a smaller surface compared to itsfull size. The 1st reef is used in strong winds. 27

2nd reefWhen the 2nd reef is set, the mainsail has a smaller surface compared tothe 1st reef. The 2nd reef is used in very strong winds. 27

A

airfoilA foil operating in the air. 97

anchorA heavy device attached to a boat by a cable and dropped overboard tosecure a boat to the seabed. 10, 50, 80

anchor bendSee fisherman’s bend. 80

anchor windlassA manual or motor-driven winch used on bigger cruisers, to facilitate anchorretrieval. 50

angle of attackAn angle between the oncoming flow and the foil’s reference line (oftenchord line). Chord line is an imaginary straight line connecting foil’s leadingand trailing edge. 97

apparent windA combination of the true wind and the wind produced by motion. 43, 45,76

asternBackwards. Abaft the stern, i.e. behind the boat. 37, 52

B

backstayA wire leading from the masthead to the stern. 2, 74

balanced helmWhen a boat has a balanced helm, it will have a little tendency to turn. Ifyou let go off the tiller/wheel, it will continue on a straight course. 68

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