An inclining test is a test performed on a
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 ...
to determine its
stability
Stability may refer to:
Mathematics
*Stability theory, the study of the stability of solutions to differential equations and dynamical systems
**Asymptotic stability
**Linear stability
**Lyapunov stability
**Orbital stability
**Structural stabilit ...
, lightship weight and the coordinates of its
center of gravity
In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weight function, weighted relative position (vector), position of the distributed mass sums to zero. Thi ...
. The test is applied to newly constructed ships greater than 24m in length, and to ships altered in ways that could affect stability. Inclining test procedures are specified by the
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 ...
and other international associations.
The weight of a vessel can be readily determined by reading
draughts
Checkers (American English), also known as draughts (; British English), is a group of strategy board games for two players which involve diagonal moves of uniform game pieces and mandatory captures by jumping over opponent pieces. Checkers ...
and comparing with the known hydrostatic properties. The
metacentric height
The metacentric height (GM) is a measurement of the initial static stability of a floating body. It is calculated as the distance between the centre of gravity of a ship and its metacentre. A larger metacentric height implies greater initial stab ...
(GM), which dominates stability, can be estimated from the design, but an accurate value must be determined by an inclining test.
The inclining test is usually done inshore in calm weather, in still water, and free of mooring restraints to achieve accuracy. The GM position is determined by moving weights transversely to produce a known overturning moment in the range of 1-4 degrees if possible.
Knowing the restoring properties (buoyancy) of the vessel from its dimensions and floating position and measuring the equilibrium angle of the weighted vessel, the GM can be calculated.
As in a new ship test, the weight shifts have to be known and the angles of tilt measured. A series of weight (
ballast
Ballast is material that is used to provide stability to a vehicle or structure. Ballast, other than cargo, may be placed in a vehicle, often a ship or the gondola of a balloon or airship, to provide stability. A compartment within a boat, ship, ...
) movements are used to obtain an average and variance for GM.
See also
*
Metacentric height
The metacentric height (GM) is a measurement of the initial static stability of a floating body. It is calculated as the distance between the centre of gravity of a ship and its metacentre. A larger metacentric height implies greater initial stab ...
*
Naval architecture
Naval architecture, or naval engineering, is an engineering discipline incorporating elements of mechanical, electrical, electronic, software and safety engineering as applied to the engineering design process, shipbuilding, maintenance, and o ...
*
Semi-submersible
Semi-submersible may refer to a self-propelled vessel, such as:
* Heavy-lift ship, which partially submerge to allow their cargo (another ship) to float into place for transport
*Narco-submarine, some of which remained partially on the surface
* ...
References
External links
{{Ship measurements
Ship measurements