Ship lightweight Calculation

(In cargo ships preliminary design)

Introduction

The calculation of the ship lightweight and her center of gravity is one of the basic tasks to be performed in the ship initial design stage, where it is advisable to be able to perform quick, approximate calculations, allowing to quickly analyze many alternative dimensionings. In this blog I present a form to enter the main dimensions of a cargo ship from which the program computes, approximately, the ship lightweight and center of gravity height broken down in Steel, Equipment and Machinery. Results are limited to ships up to 320 m. length between perpendiculars and aspect ratios should be normal.

Definitions

The user is required to define type of vessel and these dimensions:

• Length between pp
• Breadth
• Depth to Upper deck
• Design draft
• Block coefficient
• MCR of propulsion engine
• RPM of propulsion engine(s)

There are options to specify cargo space volume in reefer ships, ice class navigation notation, number of line shafts and type of engine coupling. Also optional is to define experience coefficients of 3 lightship components, based on the actual information that the designer may have got by comparing actual data with the results obtained with this method. Optional data are indicated with an * and in gray cells, with default values between [ ].

Results

Results are displayed in a table as shown.

Referencess

Ref.1 El Proyecto Básico del Buque Mercante (Merchant ship's basic design). R. Alvariño, J.J. Azpiroz, M.Meizoso. FEIN 2007
Ref.2 Ship design for Efficiency and Economy, H. Schneelkuth. Butterworths

Ship lightweight Calculation

Cargo ships

Bulkcarrier Crude Oil tanker Chemical tanker Oil Products tanker General Cargo Coaster Reefer LPG carrier Container carrier

Length Lpp (m)
Breadth (m)
Depth to Upper deck (m)
Draft T. summer(m)
Block Coefficient @ summer T.
Propulsion engine(s) Power(Kw)
RPM of P. Engine(s)
P. Engine(s) coupling: Direct[1]/Reductor 2 *
Number of line shafts [1]/2 *
Ice Class ([0] a 5) *
Steel experience coefficient *
Equipment experience coefficient *
Machinery experience coefficient *
Reefer Capacity (cubic feet)*

Results	Weight (Tm)	Kg (m)
Ship type
Steel (+)
Equipment
Machinery
Light Weight
Deadweight