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12: Boat stability
12: Boat stability
12: Boat stability
This is a draft cheat sheet. It is a work in progress and is not finished yet.
Stability theory
Center of Buoyancy |
The force generated by a vessel displacing water. It changes position depending on heel angle, trim and loading. |
Center of Gravity |
It is determined by structure and weight distribution of a vessel. Ideally the centre of gravity should be as low as possible. |
The Angle of Heel |
As the boat heels more the righting moment becomes greater. |
The Point of Vanishing Stability |
When the righting moment becomes zero the vessel inverts. This is called the angle of vanishing stability (AVS). |
Righting moment curves - sailing vessel
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Recreational craft directive
Category |
Type |
Wind Force |
Wave Height |
A |
Ocean |
F8 |
4m |
B |
Offshore |
F8 |
4m |
C |
Inshore |
F6 |
2m |
D |
Sheltered waters |
F4 |
0.5m |
New yachts in Europe are built to the Recreational Craft Directive (RCD). Minimum standards laid down for construction and stability. It gives an indication of the operating limits of a vessel with the category A, B, C or D displayed on the builders plate.
Righting moment curves - motor vessel
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