The slides, written out
AI-drawn illustration. Simplified to explain the idea, not to scale.
Slide 1 · UNDERSTANDING
UNDERSTANDING
SHIP STABILITY &
MODERN
SHIPBUILDING
Heel Due to Turning &
Advantages of Prefabrication
Key concepts every mariner
should know for safer
operations and better
understanding.
Slide 2 · WHY DOES A SHIP HEEL DURING A TURN?
WHY DOES A SHIP HEEL DURING A TURN?
A ship experiences two phases of heeling when making a turn.
1 INITIAL INWARD HEEL (TRANSIENT)
TRANSIENT RESPONSE
The very first response when the rudder is put over is an INWARD heel (towards the centre of the turn).
This is caused by the athwartships component of the rudder force acting at the stern.
Inward Heel
Rudder Force
2 OUTWARD HEEL (STEADY STATE)
STEADY STATE RESPONSE
As the ship develops a steady turn, centrifugal force acts outward through the centre of gravity (G).
A corresponding centripetal force acts inward through the centre of lateral resistance (CLR), near the centre of buoyancy (B).
This creates an outward heeling moment and the ship rolls OUTWARD to a steady heel angle.
Centrifugal Force (Outward)
Centripetal Force (Inward)
G
B
CLR
Small-angle relationship
tan θ = V²h / g R GM
V = Speed of ship (m/s)
R = Radius of turn (m)
g = Acceleration due to gravity (9.81 m/s²)
GM = Metacentric height (m)
h = Vertical distance between the line of action of centrifugal force through G and the inward hydrodynamic force.
KEY TAKEAWAY
Higher speed, smaller turning radius, higher KG (through increased heeling lever and reduced GM), or lower GM increases the outward heel.
Slide 3 · HOW LOADING AFFECTS
HOW LOADING AFFECTS
TURNING HEEL
The height of the centre of gravity (KG) plays
a major role in the outward heel produced
during a turn.
COMPARISON AT A GLANCE
HIGH KG
(TENDER SHIP)
LOW KG
(STIFF SHIP)
Centrifugal
Force
(Outward)
Centripetal
Force
(Inward)
G
B
CLR
Centrifugal
Force
(Outward)
Centripetal
Force
(Inward)
G
B
CLR
Larger turning heeling lever (h)
Lower GM
Greater outward heel
Slower return to upright
Greater rolling tendency
Smaller turning heeling lever (h)
Higher GM
Less outward heel
Faster return to upright
Better resistance to heeling
IMPORTANT NOTE
Raising KG not only increases the turning lever but also reduces GM.
Both effects together increase the angle of heel during a turn.
KEY MESSAGE
Maintaining a low KG (and adequate GM) helps reduce turning heel,
improves manoeuvrability, and enhances overall safety.
Slide 4 · WHY MODERN SHIPS ARE BUILT USING PREFABRICATED BLOCKS
WHY MODERN SHIPS ARE BUILT USING PREFABRICATED BLOCKS
Prefabrication (block construction) has revolutionized shipbuilding and offers significant advantages.
1
FASTER CONSTRUCTION
Blocks are fabricated simultaneously in workshops while other blocks are being assembled in the dock, drastically reducing overall building time.
2
BETTER QUALITY CONTROL
Work in a controlled environment allows for better welding conditions, precise alignment, and easier inspection (NDT), resulting in higher quality and reliability.
3
IMPROVED SAFETY & WORKING CONDITIONS
Workshops provide safer, weather-free environments with better lighting, ventilation, and ergonomics—reducing accidents and improving productivity.
4
EASIER INSTALLATION OF SYSTEMS & MACHINERY
Piping, cabling, ventilation, and equipment can be installed in blocks before assembly, ensuring better access and reducing rework in confined spaces.
5
OPTIMAL USE OF DOCK SPACE & HIGHER PRODUCTIVITY
Blocks are built outside the dock, so the ship stays in the dock only for assembly and launch—allowing shipyards to build more ships in less time.
KEY MESSAGE
Prefabrication improves construction efficiency, quality, safety, and overall shipbuilding productivity while reducing project timelines.
Drafted by SailR from our daily lessons. AI-drawn illustration. Simplified to explain the idea, not to scale. Last updated 19 Oct 2026.
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