The deck line is shown here for illustration only. Usually the distance between the deck line and the Plimsoll mark is greater than shown here. The distance between the deck line and the mark to which the vessel is loaded is the Freeboard. The mark is required to be permanently fixed to the vessel amidships on both sides of the hull and painted in a colour that contrasts with the hull colour.
LTF - Lumber, Tropical Fresh - This is the draft to which the vessel can load when carrying lumber in the Tropical Fresh designated zone.
LF - Lumber, Fresh - This is the draft to which the vessel can load when carrying lumber in the Fresh designated zone.
LT - Lumber, Tropical - This is the draft to which the vessel can load when carrying lumber in the Tropical designated zone.
LS - Lumber, Summer - This is the draft to which the vessel can load when carrying lumber in the Summer designated zone.
LW - Lumber, Winter - This is the draft to which the vessel can load when carrying lumber in the Winter designated zone.
LWNA - Lumber, Winter, North Atlantic - This is the draft to which the vessel can load when carrying lumber in the Winter North Atlantic designated zone.
F - Fresh - This is the draft to which the vessel can load when not carrying lumber in the Fresh designated zone.
TF - Tropical, Fresh - This is the draft to which the vessel can load when not carrying lumber in the Tropical Fresh designated zone
F - Fresh - This is the draft to which the vessel can load when not carrying lumber in the Fresh designated zone
T - Tropical - This is the draft to which the vessel can load when not carrying lumber in the Tropical designated zone
S - Summer - This is the draft to which the vessel can load when not carrying lumber in the Summer designated zone
W - Winter- This is the draft to which the vessel can load when not carrying lumber in the Winter designated zone
WNA - Winter, North Atlantic - This is the draft to which the vessel can load when not carrying lumber in the Winter North Atlantic designated zone
LR - Lloyds Register - The initals of the Classification Society which assigns the marks.
Other possible Initials are: BV - Bureau Veritas, GL - Germanischer Lloyd, AB - American Bureau of Shipping, and so on.
These marks are used in conjunction with the loadline chart, which clearly shows the designated areas and the dates which apply to these zones.
A vessel loading in a summer zone for a port in another zone with a higher freeboard requirement may, for instance, load to the summer mark, provided that she has lightened enough due to fuel and water consumption by the time that zone is reached that she is in compliance.
All vessels must, in addition to having the loadline permanently marked
on both sides of the hull, carry a loadline certificate, issued by a classification society, this certificate stipulates the distances and drafts
required for that particular vessel.
The loadline zones chart
Some facts about the Plimsoll line.
When, in 1836, public concern about the loss of ships and crews reached the point where the British Parliament was forced to appoint a committee to investigate the growing number of shipwrecks. In 1850, legislation was passed to create the Marine Department of the Board of Trade, to enforce application of laws governing manning, crew competence, and operation of merchant vessels. The first battle of the load lines had begun.
Despite calls for regulation, the British government avoided direct interference with ship operators until, in 1870 Samuel Plimsoll, a member of Parliament from the industrial Midlands, demanded creation of a safety limit, a "load line" to limit the weight of cargo loaded aboard ships.
Plimsoll exposed what he described as "coffin ships" created by overloading, and drafted a bill to improve conditions aboard merchant vessels. The government formed a "Royal Commission" to investigate merchant marine practices and conditions and exposed many "malpractices" committed by "bad owners." A reform bill was introduced in 1875 but was defeated. Public awareness of shoddy practices and abuse had become widespread however, and in 1876 the first load line regulations were made into law. This law was applied to all ships calling at British ports. Because of this every merchant ship afloat carries the "signature" of Samuel Plimsoll, a politician from Derby, part of England closer to horse racing and Robin Hood than the sea.
Who Regulates ships?
The Plimsoll Mark (Load Lines) and American Shipping
The position of the load line was not fixed by regulation in the early years and there was considerable variation in how the line was marked on a ship's side. American vessels were loaded to a formula based on "inches per foot of depth of hold" (the method used in Britain prior to 1890) until 1917, when the U.S. Shipping Board required adherence to British Board of Trade standards based on a set of calculated freeboard tables.
Load line legislation was introduced in congress in 1920 and failed. Not until 1929 was the Load Line Act passed in the United States, more than a century after ship losses due to overloading became a recognized problem in the industry.
These are some of the factors which affect the allocation of the Plimsoll mark to a vessel.
Structural Strength - The deeper the draft of a ship (the amount of the ship that is underwater), the greater are the loads imposed on the ship's structure.
Compartmentalization - In the event of an accident (or casualty in marine terms), the amount of reserve bouyancy available will depend on how the hull is divided into separate watertight compartments. Compartmentalization is especially critical in the design and construction of passenger ships and special subdvision load lines are assigned for these vessels.
Deck Height - Platform height (the height of the weather deck above the waterline) is a measure of how the vessel may be affected by seas which sweep across the deck.
Transverse Stability - While freeboard does not directly determine the side-to-side stability of a ship, higher freeboard will allow a ship to roll further before submerging the deck.
Hull Form - Sheer describes the curve between bow and stern. A ship with high freeboard at the bows and stern compared to midships (where freeboard is measured) has more reserve bouancy.
Fullness - The underwater shape of a hull. A rectangular cross-section as on a tanker, is described as "full" and has less reserve bouyancy with the same freeboard than a more rounded hull like that of tugboat or liner.
Length - A long ship only a few feet of freeboard has less reserve bouyancy that a shorter ship with the same freeboard.
Type of Vessel and Cargo - Tankers and Lumber ships with bouyant cargoes require less freeboard than a passenger liner or containership.
Season and Zone - Weather conditions normally encountered along a ship's trade route effects its seaworthiness. Ships sailing the North Atlantic in Winter are exposed to much more severe conditions than one sailing around the South Seas.