Introduction to Naval Architecture

E. C. Tupper

• Publisher: Butterworth-Heinemann
• Year: 2013
• ISBN:
  9780080982724
• Edition: 5
• Topic: Technologie et ingénierie
• Subtopic: Sciences et technologies militaires

Written by an award-winning naval architecture author and former vice-president of the Royal Institution of Naval Architects (RINA), the fifth edition of Introduction to Naval Architecture has been fully updated to take in advances in the field and is ideal both for those approaching the subject for the first time and those looking to update or refresh their knowledge on areas outside of their direct expertise.

This book provides a broad appreciation of the science and art of naval architecture, explaining the subject in physical rather than in mathematical terms. While covering basic principles, such as hull geometry, propulsion, and stability, the book also addresses contemporary topics, such as computer aided design and computer aided manufacture (CAD/CAM). The new edition reflects the continuing developments in technology, changes in international regulations and recent research.

Knowledge of the fundamentals of naval architecture is essential not only for newcomers to the field but also the wealth of non-naval architects working in the marine area, including marine engineers, marine surveyors and ship crews. This book provides the most well-known and trusted introduction to the topic, offering a clear and concise take on the basics of this broad field.

Praise for previous edition

"...a clear and concise introduction to the subject, giving a good grasp of the basics of naval architecture." — Maritime Journal

"...my go-to book for understanding the general principles of naval architecture. The book is well-written and easy to understand." — Amazon.com reviewer

• Provides a perfect introduction to naval architecture for newcomers to the field and a compact overview for related marine professionals needing a working knowledge of the area
• Updated to cover key developments including double-hulled tankers and the increased use of computational methods and modeling in ship design
• Draws on the experience of renowned naval architecture author Eric Tupper to provide extensive scope and authoritative detail, all in an accessible and approachable style

Chapter 1

Introduction

General

Modern large ships are perhaps the most complex of modern engineering projects and represent the largest man-made mobile structures. Ships still carry over 90% of world trade and still carry large numbers of people on pleasure cruises and ferries in all areas of the globe. Ships, and other marine structures, are needed to exploit the riches of the deep. Their design, build, maintenance and operation, in all of which naval architects play a major role or exert considerable influence, are fascinating activities.

Although one of the oldest forms of transport, ships, their equipment and their function, are subject to constant evolution due to changes in world trade and technology and by pressure of economics. Other changes are driven by social changes and, in particular, by the public’s desire for greater safety and for more protection of the environment.

A feature of many new designs is the variation in form of ships intended for relatively conventional tasks. This is for reasons of efficiency and has been made possible by the advanced analysis methods available, backed up by model experiment when needed. These enable unorthodox configurations to be adopted with confidence.

Naval Architecture and the Naval Architect

What is naval architecture and what is required of a naval architect? In essence, one can say that naval architecture is the science of making a ship ‘fit for purpose’ and a naval architect is an engineer competent in naval architecture. A fuller answer on the nature of naval architecture is to be found in Ferreiro (2007). In summary, he defines naval architecture as:

The branch of engineering concerned with the application of ship theory within the design and construction process, with the purpose of predicting the characteristics and performance of the ship before it is built.

He defines ship theory as

The science explaining the physical behaviour of a ship, through the use of fundamental mathematics or empirically derived data.

The Ship

‘Ship’ should be interpreted broadly to mean any structure floating in water. It is usually self-propelled but may rely on tugs for movement. Others rely on the wind. Marine structures, such as harbour installations, are the province of the civil engineer.

The purpose of a merchant ship is to carry goods, perhaps people, safely across water. That of a warship is the support of government policy. In ordering a new merchant ship, the owner will have in mind a certain volume of cargo to be carried on voyages between certain ports with an average journey time. Each requirement will have an impact upon the ship design. For instance:

• The type of cargo may be able to be carried in bulk or may require packaging; it may be hazardous or it may require a special on-board environment.

• The volume of cargo will be the major factor in determining the size of the ship. There may be a need to move the cargo in discreet units of a specified size and weight.

• Ports, plus any rivers and canals to be negotiated, may place restrictions on the overall dimensions of the vessel. Depending on the port facilities, the ship may have to have more, or less, cargo handling equipment on board. The routes used also dictate the ocean areas to be traversed and hence the sea and weather conditions likely to be encountered.

• Schedules dictate the speed and hence the installed power. They may indicate desirable intervals between maintenance periods.

Fit for Purpose

To be fit for purpose, a ship must be able to operate safely and reliably. It must:

• float upright with enough watertight volume above the waterline to cope with waves and accidental flooding.

• have adequate stability to cope with operational upsetting moments and to withstand a specified degree of flooding following damage. It must not be so stable that motions become unpleasant.

• be able to maintain the desired average speed in the sea conditions it is likely to meet.

• be strong enough to withstand the loads it will experience in service.

• be capable of moving in a controlled way in response to movements of control surfaces, to follow a given course or manoeuvre in confined waters.

The ship must do all this economically with the minimum crew. This book deals with these various matters and brings them together in discussing the design process and the different ship types that emerge from that process. The design should be flexible because ship use is likely to change over the long life expected of ships.

Variety

Naval architecture is a fascinating and demanding discipline. It is fascinating because of the variety of floating structures and the many compromises necessary to achieve the most effective design. It is demanding because a ship is a very large capital investment. It must be safe for the people on board and the environment. Unlike many other forms of transport, the naval architect does not have the benefit of prototypes.

There are fishing vessels ranging from small local boats operating by day to ocean-going ships with facilities to deep freeze their catches. There are vessels for exploitation of undersea energy sources, gas and oil and extraction of minerals. There are oil tankers, ranging from small coastal vessels to giant supertankers. Other huge ships carry bulk cargoes such as grain, coal or iron ore. Ferries carry passengers between ports which may be only a few kilometres or hundreds apart. There are tugs for shepherding ships in port or for trans-ocean towing. Then there are dredgers, lighters and pilot boats without which a port could not function. Warships range from huge aircraft carriers through cruisers and destroyers to frigates, patrol boats, mine countermeasure vessels and submarines.

Increasingly naval architects are involved in the design of small craft such as yachts and motor cruisers. This reflects partly the much greater number of small craft, partly the increased regulation to which they are subject requiring a professional input and partly the increasingly advanced methods used in their design and new materials in their construction. In spite of the increasingly scientific approach, the design of small craft still involves a great deal of ‘art’. Many are beautiful with graceful lines and lavishly appointed interiors. The craftsmanship needed for their construction is of the highest order.

Many naval architects are involved in offshore engineering – finding and exploiting oil, gas and mineral deposits. Their expertise has been needed for the design of the rigs and the many supporting vessels, including manned and unmanned submersibles used for maintenance of underwater installations. This involvement will continue as the riches of the ocean and ocean bed are exploited in the future and attention focuses on the polar regions.

Ships come in a variety of hull forms. Much of this book is devoted to single hull, displacement forms which rely upon displacing water to support their full weight. In some applications, particularly for fast ferries, multiple hulls are preferred because they provide large deck areas and good stability without excessive length. In planing craft, high speeds may be achieved by using dynamic forces to support part of the weight when under way. Surface effect ships use air cushions to support the weight of the craft, lifting it clear of the water and providing an amphibious capability. Hydrofoil craft rely on hydrodynamic forces on submerged foils under the craft to lift the main part of the hull above the waves.

Variety is not limited to appearance and function. Different materials are used– steel, wood, aluminium, reinforced plastics of various types and concrete. The propulsion system used to drive the craft through the water may be the wind but for most large craft is some form of mechanical propulsion. The driving power may be generated by diesels, steam or gas turbine, some form of fuel cell or a combination of these. Power will be transmitted to the propulsion device through mechanical or hydraulic gearing or by using electric generators and motors as intermediaries. The propulsor itself is usually some form of propeller, perhaps ducted, but may be a water or air jet. There are many other systems on board, such as means of manoeuvring the ship, electric power generation, hydraulic power for winches and other cargo handling systems.

Growing concern as regards pollution of the environment – the atmosphere and the oceans – is having an increasing impact on ship design and operations. ‘Greener’ forms of propulsion are being developed with greater emphasis on efficiency to reduce usage of fuel.

A ship can be a veritable floating township of several thousand people remaining at sea for several weeks. It needs electrics, air conditioning, sewage treatment plant, galleys, bakeries, shops, restaurants, cinemas and other leisure facilities. All these and the general layout must be arranged so that the ship can carry out its intended tasks efficiently. The naval architect has the problems of the land architect but, in addition, a ship must float, move, be capable of surviving in a very rough environment and withstand a reasonable level of damage. It is the naval architect who ‘orchestrates’ the design, calling upon the expertise of many other professions in achieving the best compromise between many, often conflicting, requirements. Naval architecture is a demanding profession because a ship is a major capital investment taking many years to create and expected to remain in service for 25 years or more. It is usually part of a larger transport system and must be properly integrated with the other elements of the overall system. A prime example of this is the container ship. Goods are placed in containers at the factory. These containers are of standard dimensions and are taken by road, or rail, to a port with specialised handling equipment where they are loaded on board. At the port of destination, they are off-loaded on to land transport. The use of containers means that ships need to spend far less time in port loading and unloading and the cargoes are more secure. Port fees are reduced and the ship is used more productively.

Safety

Most important is the safety of crew, ship and, increasingly, the environment. The design must be safe for normal operations and not be unduly vulnerable to mishandling or accident. No ship can be absolutely safe and a designer must take conscious decisions as to the level of risk judged acceptable in the full range of scenarios in which the ship can expect to find itself. There will always be a possibility that the design conditions will be exceeded. The risk of this and the potential consequences must be assessed and only accepted if they are judged unavoidable or the level of risk is acceptable. Acceptable, that is, to the owner, operator and the general public and not least to the designer who has ultimate responsibility. Even where errors on the part of others have caused an accident, the designer should have considered such a possibility and taken steps to minimise the consequences. For instance, in the event of collision, the ship must have a good chance of surviving or of remaining afloat long enough for passengers to be taken off safely. This brings with it the need for a whole range of life-saving equipment.

Naval architects must work closely with those who build, maintain and operate the ships they design. This need for teamwork and the need for each player to understand the others’ needs and problems are the themes of a book published by The Nautical Institute in 1999.

The Impact of Technology and Computers

Over the last half-century, changing technology has had a tremendous impact upon how ships are designed, built, operated and maintained. The following are examples:

• Satellites enable ships to locate their position accurately using global positioning systems. They can pick up distress signals and locate the casualty for rescue organisations. They can measure sea conditions over wide areas and facilitate the routeing of ships to avoid worst storms.

• Modern materials require much less maintenance, reducing operating costs and manpower demands. New hull treatments permit much longer intervals between dockings and reduce pollution of the ocean.

• Modern equipment is generally more reliable. Modularisation and repair by replacement policies reduce downtime and the number of repair staff needed on board. Electronically controlled operating and surveillance systems enable fewer operators to cope with large main propulsion systems and a wide range of ship’s services.

The biggest impact has been the influence of the computer which has made a vital contribution to many of the changes referred to above. But it is in the sequence of design, build, maintaining and running of ships that their influence has been greatest for the naval architect. In some cases, these processes have changed almost beyond recognition, although the underlying principles and objectives remain the same.

In Design

Computer-aided design (CAD) systems enable concept designs to be produced more rapidly, in greater detail and with greater accuracy. Once the concept design is agreed, the same CAD system can be used for the contract design phase. Three-dimensional graphics and virtual reality techniques can be used to interact with others more efficiently. CAD systems are integrated suites of related programs and can accommodate advanced programs for structural strength evaluations, motion predictio...