Calculation of Ship Construction

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Naval Architecture, displacement, volumes, hull, submerged, archimedes principles, floatation, areas, mathematics, simpson rules, block coefficient, prismatic coefficient of ships in seawater and freshwater. Transverse stability, longitudinal stability, trim, bilging, ballast, rudder, power, speed, velocity, fuel consumption, resistance for naval architects, marine engineers, navigation officers.

Dear Visitor,

Have you wondered how Naval Architects calculate areas of uneven objects like the hulls of ships? How how much power is needed to drive a ship? Or how much the ship will tilt whenever cargo, fuel oil, or water are added or removed from the ship. Also how much depth the ship will sink down with each cargo loading.

Before a ship is even built, the designers must know how it will behave.


For rectangular blocks, it is very simple to calculate the volume. However ship hulls are pointed at the bow, parallel at the middle portion, and slightly pointed again at the stern.

For uneven or curved objects like ship hulls, naval architects make use of measurement of different lengths from fixed axis, do a summation of all the values to get a very good estimation of the total areas, or volumes. Simpson's 1st and 2nd rules are good examples of these types of calculations.

Block coefficient, prismatic coefficient, midship section area coefficient, waterplane area coefficient are some of the well known multiplying factors that compares the shape of a ship hull to the rectangular shape.

Calculation of water pressure acting a submerged body, center of gravity, center of buoyancy are covered as hydrostatics.

Transverse Stability and Trim

This is a study of how shifting weights will affect the center of gravity, center of buoyancy, the righting lever that will tend to bring the ship to equilibrium and how they will affect the transverse stability of the ship.

Also to determine at what angle of heel the ship will turn over beyond recovery.

In the study of trim, naval architects, marine engineers, or deck officers determine how the ship will behave as dry cargo is loaded in the cargo holds or liquid cargo in the cargo tanks, or when fuel oil or water is consumed during long voyages. Also when the ship is damaged and flooded, or ballast water is transferred into or out of ballast tanks.


The naval architect must be able to determine how big the rudder needs to be in order to turn a ship, and how big the turning angle of the ship is and how large the forces on the rudder stock are.

From the study, a suitable rudder stock shaft could be chosen to withstand the shearing forces on the shaft, and the driving steering gear needed to hold the forces of the water flowing past the rudder.

Power, Resistance, Speed, Fuel Consumption

How much power is needed to drive the ship? The naval architect must choose the prime mover engine based on calculations and referring to results of experiments on scale models in controlled conditions.

The relationships between speeds, length of ship, wetted surface areas, and displacements have already been discovered and are very useful for the calculations.

In this study, frictional resistances and residual resistances have to be determined.

Questions and Answers in Naval Architecture

Now, we have compiled a reference e-book for people interested in knowing how to apply the calculations to various situations in Naval Architecture.

The e-book can be downloaded for free.

I hope this information will serve you well if you ever need to determine the behavior of ships.



Marine Engineer World


P.S. The professional seafarer, whether Navigation Officer or Engineer, would find the e-book Questions and Answers in Naval Architecture very useful.

2004 Yoon Chee Tuck    Contact me

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