Waterline refers to an imaginary line marking the level at which ship or boat floats in the water. A ship /ʃɪp/ is a large vessel that floats on water Ships are generally distinguished from Boats based on size A boat is a Watercraft of modest size designed to float or plane on water and provide transport over it Water is a common Chemical substance that is essential for the survival of all known forms of Life. To an observer on the ship the water appears to rise or fall against the hull . A hull is the body of a Ship or Boat. It is a central concept in floating vessels as it provides the Buoyancy that keeps the vessel from sinking Temperature also affects the level because warm water provides less buoyancy, being less dense than cold water. In Physics, buoyancy ( BrE IPA: /ˈbɔɪənsi/ is the upward Force on an object produced by the surrounding liquid or gas in which it is Likewise the salinity of the water affects the level, fresh water being less dense than salty seawater. Salinity is the Saltiness or dissolved salt content of a body of Water. Seawater is Water from a Sea or Ocean. On average seawater in the world's oceans has a Salinity of about 3

For vessels with displacement hulls, the hull speed is determined by, amongst other things, the waterline length. A hull is the body of a Ship or Boat. It is a central concept in floating vessels as it provides the Buoyancy that keeps the vessel from sinking Hull speed, sometimes referred to as displacement speed, is a Rule of thumb used to provide an approximate maximum efficient speed for a hull In a sailing boat, the length of the waterline can change significantly as the boat heels, and can dynamically affect the speed of the boat. Sailing is the art of controlling a Sailing vessel. By changing the Rigging, Rudder and dagger or centre board a Sailor manages the force Sailing is the art of controlling a Sailing vessel. By changing the Rigging, Rudder and dagger or centre board a Sailor manages the force

In aircraft design, the term waterline refers to the vertical location of items on the aircraft. This is the (normally) "Z" axis of an XYZ coordinate system, the other two axes being the Fuselage Station (X) and Buttock Line (Y).

Load line

Example of a load line certificate issued by a Classification Society. In the Shipping industry classification societies are Non-governmental organizations or groups of professionals Ship surveyors and representatives of offices

The purpose of a load line is to ensure that a ship has sufficient freeboard and thus sufficient reserve buoyancy. Freeboard or FREEBOARD may refer to Sporting Goods. The six-wheeled skateboard which acts like a snowboard (on pavement In Physics, buoyancy ( BrE IPA: /ˈbɔɪənsi/ is the upward Force on an object produced by the surrounding liquid or gas in which it is The freeboard on commercial vessels is measured between the uppermost continuous deck and the waterline and this must not be less than the freeboard marked on the Load Line Certificate issued to that ship. All commercial ships, other than in exceptional circumstances,^[1] have a load line symbol painted amidships on each side of the ship and this symbol must also be permanently marked so that if the paint wears off it can still be seen. The load line makes it easy for anyone to see whether a ship has been overloaded. The exact location of the Load Line is calculated and/or verified by a Classification Society and that society issues the relevant certificates. In the Shipping industry classification societies are Non-governmental organizations or groups of professionals Ship surveyors and representatives of offices

This symbol, also called an international load line or Plimsoll line, indicates the maximum safe draft, and therefore the minimum freeboard for the vessel in various operating conditions. The draft (or draught) of a ship's hull is the vertical distance between the Waterline and the bottom of the hull ( Keel) with the thickness ^[2]

History

The first official loading regulations are thought to date back to maritime legislation originating with the kingdom of Crete in 2,500 BC when vessels were required to pass loading and maintenance inspections. Roman sea regulations also contained similar regulations.

In the Middle Ages the Venetian Republic, the city of Genoa and the Hanseatic league required ships to load to a load line. In the case of Venice this was a cross marked on the side of the ship and of Genoa three horizontal lines.

The first 19th century loading recommendations were introduced by Lloyd's Register of British and Foreign Shipping in 1835, following discussions between shipowners, shippers and underwriters. Lloyds recommended freeboards as a function of the depth of the hold (three inches per foot of depth) and these recommendations, used extensively until 1880, became known as "Lloyd's Rule".

In the 1860s, due to the increasing losses of ships due to overloading a British MP, Samuel Plimsoll, took up the load line cause. Samuel Plimsoll (10 February 1824 &ndash 3 June 1898 was a British Politician and social reformer now best remembered for having devised the Plimsoll line. A Royal commission on unseaworthy ships was set up in 1872 and finally in 1876 the United Kingdom Merchant Shipping Act made the load line mark compulsory although the positioning of the mark was not fixed by law until 1894. In 1906, laws were passed requiring foreign ships visiting British ports to be marked with a load line. However it was not until 1930 (The 1930 Load Line Convention) that there was international agreement for universal application of load line regulations.

In 1966 a Load Lines Convention was held in London which re-examined and amended the 1930 rules. The 1966 Convention has since seen amendments in 1971, 1975, 1979, 1983, 1995 and 2003. ^[3]

Standard load line marks

Load Line Mark and Lines and Timber Load Line Mark and Lines for power driven merchant vessels

Load Line Mark and Lines for commercial sailing vessels

The original "Plimsoll Mark" was a circle with a horizontal line through it to show the maximum draft that a ship may load to. Additional marks have been added over the years to allow for different densities of water and expected sea conditions.

Letters may also appear to the sides of the mark indicating the classification society that has surveyed the vessel's load line. In the Shipping industry classification societies are Non-governmental organizations or groups of professionals Ship surveyors and representatives of offices The initials used include AB for the American Bureau of Shipping, LR for Lloyd's Register, GL for Germanischer Lloyd, BV for Bureau Veritas, IR for the Indian Register of Shipping, RI for the Registro Italiano Navale and NV for Det Norske Veritas. The American Bureau of Shipping (ABS is a Classification society, with a mission to promote the security of life property and the natural environment primarily through The Lloyd's Register Group is a maritime Classification society and independent risk management organisation providing risk assessment and mitigation services The Germanischer Lloyd AG is a Classification society based in the city of Hamburg Germany. Bureau Veritas S A (formerly BVQI Bureau Veritas Quality International is an international Certification agency "For over 140 years at the service of the shipping and industrial world Det Norske Veritas or DNV is a Norwegian company established in 1864 These letters should be approximately 115 millimetres in height and 75 millimetres in width. ^[4] The Scantling length is usually referred to during and following load line calculations. Scantling Length is a distance slightly less than the waterline length of a ship and generally less than the overall length of a ship

The letters on the Load line marks have the following meanings:

• TF – Tropical Fresh Water
• F – Fresh Water
• T – Tropical Seawater
• S – Summer Temperate Seawater
• W – Winter Temperate Seawater
• WNA – Winter North Atlantic

Fresh water is considered to have a density of 1000 kg/m³ and sea water 1025 kg/m³. Fresh water marks make allowance for the fact that the ship will float deeper in fresh water than salt water. A ship loaded to her Fresh Water mark in fresh water will float at her Summer Mark once she has passed into sea water. Similarly if loaded to her Tropical Fresh water mark she will float at her Tropical Mark once she passes in to sea water.

The Summer load line is the primary load line and it is from this mark that all other marks are derived. The position of the summer load line is calculated from the Load Line Rules and depends on many factors such as length of ship, type of ship, type and number of superstructures, amount of sheer, bow height and so on. The horizontal line through the circle of the Plimsoll mark is at the same level as the summer load line.

The Winter load line is one forty-eighth of the summer load draft below the summer load line.

The Tropical load line is one forty-eighth of the summer load draft above the summer load line.
The Fresh Water load line is an amount equal to millimetres above the summer load line where is the displacement in metric tonnes at the summer load draft and T is the metric tonnes per centimetre immersion at that draft.
In any case where cannot be ascertained the fresh water load line is at the same level as the tropical load line.
The position of the Tropical Fresh load line relative to the tropical load line is found in the same way as the fresh water load line is to the summer load line.
The Winter North Atlantic load line is used by vessels not exceeding 100 metres in length when in certain areas of the North Atlantic Ocean during the winter period. When assigned it is 50 millimetres below the winter mark. ^[5]

Timber load line marks

Certain vessels are assigned Timber Freeboards but before these can be assigned certain additional conditions have to be met. One of these conditions is that the vessel must have a forecastle of at least 0. Forecastle, also spelled fo'c's'le (ˈfoʊksəl originally meant the upper deck of a Sailing ship, forward of the Foremast. 07 the length of the vessel and of not less than standard height, which is 1. 8 metres for a vessel 75 metres or less in length and 2. 3 metres for a vessel 125 metres or more in length with intermediate heights for intermediate lengths. A poop or raised quarter deck is also required if the length is less than 100 metres. The letter L prefixes the load line marks to indicate a timber load line. ^[6] Except for the Timber Winter North Atlantic freeboard the other freeboards are less than the standard freeboards. This allows these ships to carry additional timber as deck cargo, but with the facility to jettison this cargo.

The letters on the Timber Load line marks have the following meanings:

• LTF – Timber Tropical Fresh Water
• LF – Timber Fresh Water
• LT – Timber Tropical Seawater
• LS – Timber Summer Seawater
• LW – Timber Winter Seawater
• LWNA –Timber Winter North Atlantic

The Summer Timber load line is arrived at from the appropriate tables in the Load Line Rules. ^[7]

The Winter Timber load line is one thirty-sixth of the Summer Timber load draft below the Summer Timber load line.

The Tropical Timber load line is one forty-eighth of the Summer Timber load draft above the Summer timber load line.

The Timber Fresh and the Tropical Timber Fresh load lines are calculated in a similar way to the Fresh Water and Tropical Fresh water load lines except that the displacement used in the formula is that of the vessel at her Summer Timber load draft. If this cannot be ascertained then these marks will be one forty-eighth of the Timber Summer draft above the Timber Summer and Timber Tropical marks respectively. ^[8]

The Timber Winter North Atlantic load line is at the same level as the Winter North Atlantic load line

Subdivision load line marks

Passenger ships which have spaces which are adapted for the accommodation of passengers and the carriage of cargo alternatively may have one or more additional load line marks corresponding to the subdivision drafts approved for the alternative conditions. These marks show C1 for the principal passenger condition, and C2, C3, etc. , for the alternative conditions, however in no case shall any subdivision load line mark be placed above the deepest load line in salt water. ^[9]

Subdivision Load Line Marks

Passenger vessel with no allowed Subdivision Load line

Passenger vessel with one allowed Subdivision Load line

Passenger vessel with two allowed Subdivision Load lines

See also

• Ballast tank
• Classification Society
• Coffin ship
• Hull (watercraft) for general definitions. A ballast tank is a compartment within a boat or ship that holds water In the Shipping industry classification societies are Non-governmental organizations or groups of professionals Ship surveyors and representatives of offices Coffin ship is the name given to any boat that has been overinsured and is therefore worth more to its owners sunk than afloat A hull is the body of a Ship or Boat. It is a central concept in floating vessels as it provides the Buoyancy that keeps the vessel from sinking
• The London (ship)
• Plimsoll shoe
• Sailing ballast
• Samuel Plimsoll
• Stability conditions (watercraft)

References

External links

• Historical background to the adoption of the Load Lines convention
• More historical background
• Online water density calculator
• IACS Unified Requirement L: Subdivision, Stability and Load Lines