Terminology & Units
- Last UpdatedDec 17, 2025
- 4 minute read
The following gives a list of the terminology and units used for both the hydrostatics and deadweight scale. The LBP is the perpendicular distance between the AP and the FP.
|
DRAFT |
The moulded draft at midships (LBP/2). Measured normal to the baseline. Units of meters or Feet. |
|
DISPLT |
The displacement of the ship in water of the specified density. The default density is - 1.025 tonne/m3 If no shell thickness is specified then DISPLT is the moulded displacement of the main hull and appendages. If a shell thickness is specified then this DISPLT is the extreme displacement that means, moulded displacement plus the displacement of the shell plating. The displacement of the shell plating is calculated from the shell thickness and the wetted surface area. The wetted surface area estimation is detailed below, see WSA. Units of Tonnes or Tons. |
|
TPI |
The tonnes per centimeter immersion or the tons per inch immersion.
WPA is the moulded waterplane area including appendages but not including shell plating. WPA is defined below. Units of Tonnes or Tons. |
|
MCT |
The moment to change trim one centimeter or one inch between the perpendiculars. For simplicity, MCT is assumed to be independent of the VCG, that means, BML replaces GML in the formula, as given below:
BML is defined below. Units of Tonnes-meters or Tons-Feet. |
|
LCB |
The longitudinal center of buoyancy of the moulded hull volume, that means, including appendages and excluding shell plating. Measured from the AP, positive forwards and parallel to the baseline. Units of meters or Feet. |
|
LCF |
The longitudinal centre of flotation of the moulded waterplane area, that means, including appendages and excluding shell plating. Measured from the AP, positive forwards and parallel to the baseline. Units of meters or Feet. |
|
TCF |
The transverse center of flotation of the moulded waterplane area, that means, including appendages and excluding shell plating. Measured normal to the centreline, positive to starboard. Units of meters or Feet. |
|
KML |
The height of the longitudinal metacentre above the moulded baseline at midships. The moulded hull waterplane area and volume are used, that means, including appendages but not the shell plating. KML = VCB + BML Units of meters or Feet. |
|
WPA |
The moulded waterplane area including appendages and excluding shell plating. Units of meters2 or Feet2. |
|
VCB |
The vertical center of buoyancy of the moulded hull volume, including appendages and excluding shell plating. Measured normal to the moulded baseline at midships. Units of meters or Feet. |
|
TCB |
The transverse center of buoyancy of the moulded hull volume, including appendages and excluding shell plating. Measured normal to the centreline, positive to starboard. Units of meters or Feet. |
|
BML |
The longitudinal metacentric radius, that means, the height of the longitudinal metacentre above the centre of buoyancy for the moulded hull.
Units of meters or Feet. |
|
BMT |
The transverse metacentric radius, that means, the height of the transverse metacentre above the centre of buoyancy for the moulded hull.
Units of meters or Feet. |
|
CB |
The block coefficient:
Moulded Volume includes appendages and excludes shell plating. |
|
CM |
The midship sectional area coefficient:
Midship Sectional Area is the moulded section. |
|
CW |
The waterplane area coefficient:
|
|
CP |
The prismatic coefficient:
|
|
KMT |
The height of the transverse metacentre above the moulded baseline. The moulded hull waterplane area and volume are used that means, including appendages and excluding the shell plating. KMT = VCB + BMT Units of meters or Feet. |
|
WSA |
The wetted surface area can be calculated in one of two ways (as specified in Ship Data/General):
Units of meters2 or Feet2. |
