Freeboard (nautical)
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In
sailing Sailing employs the wind—acting on sails, wingsails or kites—to propel a craft on the surface of the ''water'' (sailing ship, sailboat, raft, windsurfer, or kitesurfer), on ''ice'' (iceboat) or on ''land'' (land yacht) over a chosen cour ...
and
boating Boating is the leisurely activity of travelling by boat, or the recreational use of a boat whether Motorboat, powerboats, Sailing, sailboats, or man-powered vessels (such as rowing and paddle boats), focused on the travel itself, as well as sp ...
, a vessel's freeboard is the distance from the
waterline The waterline is the line where the hull of a ship meets the surface of the water. Specifically, it is also the name of a special marking, also known as an international load line, Plimsoll line and water line (positioned amidships), that indi ...
to the upper deck level, measured at the lowest point of sheer where water can enter the
boat A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size, shape, cargo or passenger capacity, or its ability to carry boats. Small boats are typically found on inl ...
or
ship A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished ...
. In commercial vessels, the latter criterion measured relative to the
ship's load line The waterline is the line where the hull of a ship meets the surface of the water. Specifically, it is also the name of a special marking, also known as an international load line, Plimsoll line and water line (positioned amidships), that indi ...
, regardless of deck arrangements, is the mandated and regulated meaning. In yachts, a low freeboard is often found on racing boats, for increased speed (by reducing weight and therefore drag). A higher freeboard will give more room in the cabin, but will increase weight and drag, compromising speed. A higher freeboard, such as used on
ocean liners An ocean liner is a passenger ship primarily used as a form of transportation across seas or oceans. Ocean liners may also carry cargo or mail, and may sometimes be used for other purposes (such as for pleasure cruises or as hospital ships). Ca ...
, also helps weather waves and so reduce the likelihood of being washed over by full water waves. A low-freeboard vessel is susceptible to taking in water in rough seas. Freighter ships and
warship A warship or combatant ship is a naval ship that is built and primarily intended for naval warfare. Usually they belong to the armed forces of a state. As well as being armed, warships are designed to withstand damage and are usually faster a ...
s use high freeboard designs to increase internal volume, which also allows them to satisfy
International Maritime Organization The International Maritime Organization (IMO, French: ''Organisation maritime internationale'') is a specialised agency of the United Nations responsible for regulating shipping. The IMO was established following agreement at a UN conference ...
(IMO) damage stability regulations, due to increased
reserve buoyancy The waterline is the line where the hull of a ship meets the surface of the water. Specifically, it is also the name of a special marking, also known as an international load line, Plimsoll line and water line (positioned amidships), that indi ...
.


See also

*For the term as used in measuring sea ice, see
Sea ice thickness Sea ice thickness spatial extent, and open water within sea ice packs can vary rapidly in response to weather and climate. Sea ice concentration are measured by satellites, with the Special Sensor Microwave Imager / Sounder (SSMIS), and the ''Europ ...
. *
Narco-submarine A narco-submarine (also called a drug sub or narco sub) is a type of custom ocean-going self-propelled typically semi-submersible (sometimes fully- submersible) vessel built for smugglers. Newer submarines are 'nearly-fully' submersible to be ...
, a type of vessel that often is a surface ship with a very low freeboard.


Notes


References

* * {{Authority control Nautical terminology Ship measurements de:Schiffsmaße#Freibord