- Static Stability:
- The ability of a ship to resist small tilts or heeling.
- Dependent on the shape of the hull and the center of gravity.
- Dynamic Stability:
- The ability of a ship to resist larger tilts or rolling under the influence of waves.
- Affected by external forces like wind, sea conditions, and wave patterns.
- Righting Moment:
- The force that acts to bring the ship back to an upright position when tilted. It is influenced by the shape of the hull, the weight distribution, and the metacenter.
Factors Affecting Ship Stability:
- Weight Distribution:
- Improper loading or cargo distribution can shift the center of gravity, affecting stability.
- Ballast:
- Water or other heavy materials used to stabilize ships, particularly during loading and unloading operations.
- Draft and Trim:
- Draft refers to the depth of the ship's hull submerged in water, while trim refers to the distribution of weight along the length of the ship.
Stability Criteria and Calculations:
- Metacentric Height (GM):
- A measure of a ship’s initial stability. The greater the GM value, the more stable the ship is.
- Stability Curves:
- Graphs that illustrate how a ship will respond to heeling or rolling.
Types of Stability Tests:
- Inclining Experiment:
- A procedure to determine a ship's stability by tilting the vessel and measuring the angle of heel.
- Critical Stability Assessment:
- This test determines the point at which a ship will capsize under extreme conditions.
Importance of Ship Stability:
- Safety:
- A stable ship ensures the safety of the crew, cargo, and passengers, reducing the risk of capsizing or sinking.
- Cargo Loading:
- Proper cargo management, ballast, and weight distribution are crucial for maintaining stability during transport.