10. Initial Stability

Question 1

Term

Answer 1

Definition

Question 2

Initial Stability

Answer 2

The stability of a vessel in the condition when the center of gravity is at its lowest point at the beginning of a voyage.

Question 3

Metacentric Height (GM)

Answer 3

The vertical distance between the center of gravity and the metacenter. It is a key indicator of initial stability.

Question 4

Metacenter (M)

Answer 4

The point about which a ship rolls and pitches; higher metacenter indicates greater initial stability.

Question 5

Center of Gravity (G)

Answer 5

The point through which the weight of the vessel acts vertically downwards.

Question 6

Righting Arm (GZ)

Answer 6

The horizontal distance between the center of gravity and the center of buoyancy when a vessel is inclined. It is a measure of the vessel’s ability to right itself.

Question 7

Center of Buoyancy (B)

Answer 7

The center of the volume of water displaced by the ship’s hull.

Question 8

Free Surface Effect

Answer 8

The effect on stability caused by the movement of liquids in partially filled tanks within the vessel, reducing the ship’s overall stability.

Question 9

Rolling Period

Answer 9

The time it takes for a ship to roll from side to side, which indicates the ship’s initial stability.

Question 10

Angle of Loll

Answer 10

The angle to which a ship with negative initial stability will lean without external force.

Question 11

Angle of Inclination

Answer 11

The angle at which a ship is tilted due to external forces or cargo shift.

Question 12

Dynamic Stability

Answer 12

The ability of a ship to resist overturning in rough seas, influenced by the initial stability.

Question 13

Heeling Moment

Answer 13

The external force applied to a ship causing it to tilt or heel.

Question 14

Static Stability

Answer 14

The initial stability of a ship in calm waters, usually evaluated by its righting arm curve against heeling angles.

Question 15

Tender Ship

Answer 15

A ship with a high center of gravity and small metacentric height, having sensitive and quick responses to external forces.

Question 16

Stiff Ship

Answer 16

A ship with a low center of gravity and large metacentric height, known for slow but strong resistance to tilting.

Question 17

Buoyancy

Answer 17

The upward force exerted by water displacement that supports the ship.

Question 18

Trim

Answer 18

The difference in draft between the bow and stern of a ship.

Question 19

List

Answer 19

The permanent inclination of a ship to either port or starboard.

Question 20

Roll

Answer 20

The oscillating motion of a ship from side to side.

Question 21

Pitch

Answer 21

The oscillating motion of a ship’s bow and stern up and down.

Question 22

Yaw

Answer 22

The side-to-side movement of a ship’s bow, deviating from its course.

Question 23

Surge

Answer 23

The forward and backward movement of a ship along its length.

Question 24

Sway

Answer 24

The lateral motion of a ship moving side to side along its width.

Question 25

Damping

Answer 25

The reduction of motion through resistance or friction.

Question 26

Draft

Answer 26

The vertical distance between the waterline and the bottom of the hull.

Question 27

Displacement

Answer 27

The total weight of the water displaced by the hull of a fully laden ship.

Question 28

Ballast

Answer 28

Weights placed in a ship to improve stability.

Question 29

Bilge

Answer 29

The lowest compartments on the ship, on either side of the keel, where water typically collects and must be pumped out.

Question 30

Bilge Keels

Answer 30

Attached along the length of the ship’s hull to reduce rolling motion.

Question 31

Draught (Draft)

Answer 31

The minimum depth of water a ship or boat requires to float.