##
7.1.1: Hydrostatic curves

A series of graphs drawn to a
vertical scale of draught and a base of length, which gives values such as the
centre of buoyancy, displacement, moment causing unit trim, and centre of
flotation. These curves are useful for quick assessment
of the draughts and the initial stability in in various loading conditions.

##
7.1.2: Draft

The

**draft**or**draught**of a**ship's**hull is the vertical distance between the waterline and the bottom of the hull (keel).**Draft**determines the minimum depth of water a**ship**or**boat**can safely navigate.##
7.1.3: Displacement

The

**displacement**or**displacement tonnage**of a ship is its weight based on the amount of water its hull displaces at varying loads. Ship displacement varies by a vessel's degree of load, from its empty weight as designed (known as "Lightweight tonnage”) to its maximum load.##
7.1.4: Centre
of Floatation

When the

**ship**floats at a particular draft, any trimming moment acting on the**ship**would act about a particular point on the water plane. This point is the centroid of the area of the water plane, and is called the**center**of the**floatation**.###
7.1.4.1: LCF:

Longitudinal
center of floatation is the distance from the reference line to the center of
floatation.

##
7.1.5: Center
of buoyancy:

**Centre of Buoyancy**of a

**ship**is defined as being at the geometric

**centre**of the underwater volume of the

**ship**at a particular instant and is the point through which the total

**buoyancy**force (B) is considered to act vertically upwards.

###
7.1.5.1: LCB

This is
the

**longitudinal centre**of the underwater volume, and is the point through which all the**buoyancy**can be said to act vertically upwards.###
7.1.5.2: VCB

The point at
which a

**vertical**line through the heeled**centre of buoyancy**crosses the line through the original one, is called vertical center of buoyancy.##
7.1.6: Tonnes
per centimetre immersion (**TPC**):

The amount of
weight which will sink the

**vessel**1 cm deeper in the water, that is, the weight which will increase the draft by 1 cm is called the tonnes per centimeter immersion (**TPC**).##
7.1.7: MCT 1cm

The

**MCT 1 cm**is the moment required to change the trim of the vessel by**1 cm**and may be calculated by using the formula:**MCT 1 cm**= W x GML/100L.

Where, W = The vessel's displacement in
tonnes.

GML = The
longitudinal metacentric height in meters.

##
7.1.8: KB

The vertical
distance between the keel and the center of buoyancy is expressed as '

**KB**'##
7.1.9: KML

**KML**is the distance between keel to longitudinal metacentric height.

##
7.1.10: KMT

KMT is the distance
between keel to Transverse metacentric height.

##
7.1.11: Waterplane Area

The

**area**of a hull at a particular horizontal**plane**, within the waterline.##
7.1.12: Wetted Area

The

**wetted area**is the**area**of the hull (watercraft) which is immersed in water.