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Ship & Naval

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Background

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Tankers can range in size of capacity from several hundred tons, which includes vessels for servicing small
harbours and coastal settlements, to several hundred thousand tons, for
long-range haulage. A wide range of products are carried by tankers,
including:

Tankers are a relatively new concept, dating from the later years of the 19th
century. Before this, technology had simply not supported the idea of carrying
bulk liquids. The market was also not geared towards transporting or selling
cargo in bulk, therefore most ships carried a wide range of different products
in different holds and traded outside fixed routes. Liquids were usually loaded
in casks - hence the term "tonnage",
which refers to the volume of the holds in terms of the amount of tuns of wine (casks) that
could be carried. Even potable water, vital for the survival of the crew, was
stowed in casks. Carrying bulk liquids in earlier ships posed several
problems:

  • The holds: on timber ships the holds were not sufficiently water or
    air-tight to prevent a liquid cargo from spoiling or leaking. The development of iron and steel hulls solved this problem.
  • Loading and Discharging: Bulk liquids must be pumped - the development of
    efficient pumps and piping systems was vital to the development of the tanker.
    Steam engines were developed as prime-movers for early pumping systems.
    Dedicated cargo handling facilities were now required ashore too - as was a
    market for receiving a product in that quantity. Casks could be unloaded using
    ordinary cranes, and the awkward nature of the casks meant that the volume of
    liquid was always relatively small - therefore keeping the market more stable.
  • Free Surface Effect: Describes the effect a
    large surface area of liquid in a ship will have on the stability of that ship.
    See Naval Architecture. Liquids in casks posed
    no problem, but one tank across the beam of a ship could pose a stablity
    problem. Extensive sub-division of tanks solved this problem.

In the end, the tanker had its beginnings in the oil industry, as oil companies sought cheaper ways to
transport their refinery product to their customers. The Oil Tanker was born.
Today most liquids are cheaper to transport in bulk and dedicated terminals
exist for each product. Large storage tanks ashore are used to store the product
until it can be subdivided into smaller volumes for delivery to smaller
customers.

Even the Guinness brewery company
in Dublin had a tanker fleet to export
the famous stout to the UK.

Different products require different handling and transport. Thus special
types of tankers have been built, such as "chemical tankers" and "oil tankers". "LNG carriers", as they are typically known, are a
relatively rare tanker designed to carry liquefied natural gas.

Among oil tankers, supertankers are designed for transporting oil
around the Horn of
Africa from the Middle
East. The floating storage and
offloading unit (FSO) Knock Nevis, formerly the ULCC Jahre
Viking, is the largest vessel in the world. The supertanker is 458 metres (1504 feet)
in length and 69 m (226 ft) wide.

Supertankers are one of the three preferred methods for transporting large
quantities of oil, along with pipeline transport and rail. However such
tankers can create environmental disasters from oil spills especially if an accident causes the ship
to sink. See Exxon
Valdez, Braer, Prestige oil spill, Torrey Canyon, and Erika for
examples of coastal accidents

Reza & Sintha


The Naval Architect

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A naval architect is a professional engineer who is responsible
for the design, construction, and/or repair of ships, boats, other marine
vessels, and offshore structures, both commercial and military, including:

Some of these vessels are amongst the largest and most complex and highly valued movable
structures produced by mankind. They are the most efficient method of
transporting the world"s raw materials and products known to man. Without them
our society could not exist as it currently does.

Modern engineering on this scale is essentially a team activity conducted by
specialists in their respective fields and disciplines. However, it is the naval
architects who often integrate their activities and take ultimate responsibility
for the overall project. This demanding leadership role requires managerial
qualities and the ability to bring together the often-conflicting demands of the
various design constraints to produce a product, which is "fit for the
purpose."

In addition to this leadership role, a naval architect also has a specialist
function in ensuring that a safe, economic, and seaworthy design is
produced.

To undertake all these tasks, a naval architect must have an understanding of
many branches of engineering and must be in the forefront of high technology
areas such as vessel arrangements, hydrodynamics, stability, and structures. He
or she must be able to effectively utilize the services provided by scientists,
lawyers, accountants, and business people of many kinds.

Naval architects typically work for shipyards, ship owners, design firms and
consultancies, equipment manufacturers, regulatory bodies, navies, and
governments.

Reza & Sintha


The science of naval architecture

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Hull Form
Hull
Form

Modern low-cost digital computers and dedicated software, combined with
extensive research to correlate full-scale, towing tank and analytical data,
have enabled naval architects to more accurately predict the performance of a
marine vehicle. These tools are used for static stability (intact
and damaged), dynamic stability, resistance, powering, hull development,
structural analysis, etc. Curiously, analytical tools (such as Computational
Fluid Dynamics) still have difficulty in predicting with absolute certainty the
response of a floating body in a random sea. The challenge is being addressed by
universities, towing tanks, and other marine research entities throughout the
world. Data is regularly shared in international conferences sponsored by RINA, Society of Naval

Architects and
Marine Engineers (SNAME) and others

Reza & Sintha


The craft of naval architecture

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Venetian gondola
Venetian
gondola

Traditionally, naval architecture has been more craft than science. The
suitability of a vessel"s shape was judged by looking at a half-model of a
vessel or a prototype. Ungainly shapes or abrupt transitions were frowned on as
being flawed. This included, rigging, deck arrangements, and even fixtures.
Subjective deors such as ungainly, full, and fine were used as a
substitute for the more precise terms used today. A vessel
was, and still is described as having a ‘fair’ shape. The term ‘fair’ is meant
to denote not only a smooth transition from fore to aft but also a shape that
was ‘right.’ Determining what ‘right’ is in a particular situation in the
absence of definitive supporting analysis encompasses the art of naval
architecture to this day.

Reza & Sintha