Introduction to Yacht Design E-Book

Ian Nicolson

• Herausgeber: Fernhurst Books Limited
• Kategorie: Fachliteratur
• Sprache: Englisch

Veröffentlichungsjahr: 2022

Beschreibung

For all those who love boats, their 'lines' are an essential element in the appreciation of individual craft. But what are these lines and how are they created? This book introduces the reader to the key principles of yacht design in a straightforward and understandable manner, allowing them to be aware of the elements and processes involved. Most of the complex maths has been replaced with simple rules of thumb. Any boat owner will benefit from understanding the characteristics of boat design which will help them if they want to modify the hull, rig, deck layout or accommodation. It will be equally useful to boat buyers who want to ask questions like: "How will she sail?"; "How much will she cost?"; "How easy is it to change things?" and "How can I reduce or increase sail area without upsetting the balance?" Boat owners and buyers will be able to feel more confident when talking to designers and boatbuilders about their current or future boat. While novice boat designers can start their journey with this book, giving them a good foundation whether they want to use pencil and paper or Computer-Aided Design. So, if you are any of the above, or simply have an interest in yacht design, this is the book for you!

Leseprobe

CONTENTS

FOREWORD

INTRODUCTION

PART 1: HOW TO BEGIN

1 GOOD-LOOKING CRAFT

2 HONING THE SPECIFICATION

3 SKETCHING THE LAYOUT & APPEARANCE

4 DRAWING A DESIGN

PART 2: DESIGNING THE YACHT

5 DRAWING THE LINES

6 WEIGHT & DISPLACEMENT

7 HOW WILL SHE PERFORM?

8 SAIL PLAN

9 CONSTRUCTION

10 ENGINES

11 THE CABIN OR ACCOMMODATION PLAN

12 THE DECK PLAN

13 COSTING A DESIGN

PART 3: MAKING ALTERATIONS TO A DESIGN

14 CHANGING THE SAIL PLAN

15 DESIGNING AN ALTERATION

PART 4: TO USE COMPUTER-AIDED DESIGN OR NOT?

16 COMPUTER-AIDED DESIGN

GLOSSARY

BIBLIOGRAPHY

FOREWORD

I have known Ian Nicolson since we both wrote for Yachts & Yachting magazine in the 1970s. I went on to establish a new yacht design company, Humphreys Yacht Design, but Ian took a different route. He joined Mylnes, the oldest yacht design firm in continuous production, in due course becoming the senior partner and owner.

But designing yachts is only one of Ian’s areas of expertise. He has also lectured at three universities, written over 25 books, many of which are still in print. Today, aged over 90, he continues to work as a yacht surveyor and race a Sonar regularly at the Royal Northern & Clyde Yacht Club.

It is that level of experience and knowledge about boats that makes Ian the ideal person to introduce you to yacht design. There can be no denying that it is a complicated business, but Ian explains the principles in a straightforward and understandable way.

I have no hesitation in recommending this book to anyone who is interested in understanding a bit more about yacht design, be they a boat owner, buyer or someone thinking about training to be a designer.

Rob Humphreys

September 2022

INTRODUCTION

DESIGN MADE EASY

This book is deliberately short and simple. Chapters have been reduced to basics and liberties have been taken, so that anyone can understand or start designing quickly and easily. Because designing is such a big subject, many problems have been eliminated by using simple ‘rules of thumb’. Subjects like stability, speed and powering have been made understandable by substantial simplification.

This book will enable a boat owner to be aware of the characteristics of their design, and it will help them if they want to modify the hull, rig, deck layout or accommodation.

It will be equally useful to boat buyers who want to ask questions like: ‘How will she sail?’; ‘How much will she cost?’; ‘How easy is it to change things?’ and ‘How can I reduce or increase sail area without upsetting the balance?’.

Boat owners and buyers will be able to feel more confident when talking to designers and boatbuilders about their current or future boat.

While novice boat designers can start their journey with this book, giving them a good foundation whether they want to use pencil and paper or Computer-Aided Design.

A yacht designed using this book should look prettier than some of the products of boat factories. She could well be faster and she should have that most valuable of all characteristics – she will have been designed lovingly by someone who does not constantly seek the cheapest way of making each component. Designs which are heavily influenced by accountants are seldom a success. If a boat is ugly she will not get the love, care and maintenance she needs. She is unlikely to last long or give her owners and crew a full measure of pleasure. The way to learn how to design beautiful craft is to look at the work of the designers whose work has lasted.

Ian Nicolson

September 2022

PART 1

HOW TO BEGIN

A yacht must be curvaceous to be beautiful. This shapeliness has a practical value because it adds to the hull strength, just as a thin eggshell gains strength from its curves.

1

GOOD-LOOKING CRAFT

There are rules for producing a good-looking craft which should seldom be broken:

1With few exceptions the above-water lines of the hull should be curvaceousIf there must be a flat line, then at least make it short – and the lines at right angles should not be flat – so that there are no flat areas. There is a practical reason here: a curved plate has ‘shape strength’, whereas a flat one is easily deformed. To understand this, take hold of a piece of paper and wave it. It is flabby and weak. Now wrap it into a tube, and it instantly gains ‘shape strength’.

2Curves should please the eye, and the eye is quickly boredSo lines should alter their curvature along their length. There are certain exceptions to this: a stem which is a straight line is acceptable, a transom seen from dead abeam or the outlines of the keel may be straight. But almost all other lines of a hull should be curvaceous.

3The sheer, that is the sweep of the deck seen in elevation, should be a bold curve with plenty of shapeNo portion of it should be straight, not even for a short length.

4The stem and the stern should not rake at the same angle, nor have the same height

5Lines which are in the same area of the structure above the sheer should have the same slopeSo the aft face of the aft cockpit coaming should have the same rake as the aft edge of the cabin top, and aft side of the aft window. If this angle is almost upright, then the fore end of the deckhouse should be much more sloped because ‘the eye is easily bored’ and does not like forward and aft slopes to be identical or nearly so.

TYPICAL FEATURES OF A DEEP-SEA CRUISERThis lines plan shows typical features on a deep-sea cruiser. The slope down at the aft end of the keel helps to keep the yacht sailing straight in rough conditions, as does the long keel. This reduces the strain on the self-steering gear.The aft cut-up reduces the area of boat in contact with the water – the wetted surface – and this enhances the light-weather performance. The cut-away aft also helps turning in confined harbours.

2

HONING THE SPECIFICATION

A professional starting a design will write down the preliminary specification, which describes the vessel and most of her gear, in ample but not comprehensive detail. There will be the main dimensions, approximate size of engine, number of berths, cruising or racing area and a note about the cost. This is followed by an area-by-area list of type, size and quality of each part of the yacht. The rig, deck gear, accommodation, electronics and so on will all be mapped out.

The final specification will be different because, during the course of the full design, owners change their minds, certain items may not be obtainable, may have been modified, found to be just too costly, or are found to have been affected by new legislation.

Beginners (and owners about to go to a professional designer) should make out three ‘wish lists’. The first includes all essentials. This will normally, but not always, cover such things as the size and purpose of the yacht, the type of construction, rig and number of berths, and anything about which there are strong thoughts – these may include quite small components. Experienced seamen want high fiddles, handy locker clasps and cleanable galleys.

The second list includes favoured features which can be sacrificed, especially if something better is found. There may not be enough money or space for everything on this list. Luxuries are put on the third list.

THE FIRST LIST – ESSENTIALS

Taking as an example an economical ocean cruiser, her first list includes:

1. The overall length is to be about 12 metres (40 feet)

2. The beam is to be moderate to fit the following requirements

3. The vessel is to be capable of long deep-sea voyages

■ She must ‘look after’ her crew in all conditions

■ She must ‘track’ well, i.e. be steady on the helm and steer easily in all wind speeds, using wind-powered and electronic self-steering units

■ She must be able to keep up with other yachts on a ‘Round-the-Worldin-Company’ cruise; but she is not a racing yacht

4. Construction must be reliable with good factors of safety

5. She must withstand accidental grounding in moderate conditions, and be safe in the hurly burly of crowded harbours and canals

6. She will normally only need one person on deck for sail handling; this could be a single-hander’s yacht

7. The normal crew will be 2, the maximum will be 5

8. Tank capacity must be suitable for long voyages and include a ‘holding’ or sewage tank

CHARACTERISTICS OF CRUISING AND RACING YACHTSWhen designing a racing boat few things matter except speed. Ease of construction, comfort, dryness and many other things are sacrificed.Cruisers are usually more of a compromise. Adequate rather than maximum speed has to be blended with a moderate cost, space inside and on deck, dryness in the cabin and on deck.

THE SECOND LIST – WOULD LOVE TO HAVE

1. High freeboard and ‘flush’ deck for a dry spacious deck and ample internal space, also for reserve stability

2. Water ballast tanks port and starboard each holding about 400 litres (90 gallons), as well as a normal ballast keel

3. Tiller steering, for economy and reliability, and for ‘feel’

4. A protected rudder and propeller

5. A truly accessible engine

6. An extra large oilskin and ‘wet’ locker

7. Space for sleeping in the cockpit

8. A workshop, even if tiny, and so on...

THE THIRD LIST – YOUR LUXURIES

The third list may contain anything from a rope cutter on the propeller shaft to a stainless steel tank for whisky in bulk.

Everyone's ideas will vary, and one person will put things on the first list which will appear on another owner's third list.

SOURCES OF INFORMATION

Designers need information, books and leaflets in substantial quantities – see the Bibliography. Browsing through yachting magazines will give the addresses of some manufacturers. The internet is an even better way to find out who, where and what the costs are.

A stroll around a boat show is a chance to collect information as to the sizes and types of engines, cookers, sinks, winches and so on. Sometimes leaflets are unavailable, so it makes sense to carry a folding rule and a notebook. In marinas there are always opportunities to take measurements, or photographs with two or three rules laid beside the fitting to show its width, height and depth.