Stability & Buoyancy

Question 1

What is the tendency of a vessel to remain upright?

Answer 1

Stability

Question 2

What are the two primary forces acting on a floating vessel that affect stability

Answer 2

Weight and buoyancy. The interaction between these two determines the vessels stability

Question 3

The point at which the weight of the vessel acts vertically downwards

Answer 3

the center of gravity

Question 4

What shifts the center of gravity

Answer 4

adding or subtracting weight

shifting weight

Question 5

When weight is changes the center of gravity

Answer 5

moves towards the added the weight

Question 6

If a vessel has been damaged so that water is flowing in and out of a hole below the waterline, this is known as

Answer 6

free communication with the sea

Question 7

The upward force of water displace by the hull

Answer 7

is the buoyancy of a shp

Question 8

The center of gravity of the displace water of a boat is known as

Answer 8

the center of buoyancy

Question 9

A vessel is said to be in equilibrium when the vessel is at rest and

Answer 9

the center of buoyancy is pushing upwards and is below the center of gravity pushing downwards.

Question 10

A ship’s equilibrium is affected by

Answer 10

the movement of the center of gravity or center of buoyancy or by some outside forces, such as wind and waves.

Question 11

When a vessel rolls, the forces of the center of gravity will

Answer 11

move in the same direction as the tool. The downward force of gravity is offset by the upward force of buoyancy and causes the vessel to heel

Question 12

When the underwater volume of a vessel changes shape, the center of buoyancies moves. It will move towards the part of the hull that is more deeply immersed causing the center of buoyancy to lose alignment with the center of gravity. This is called

Answer 12

heeling

Question 13

On a ship, the intersection of the vertical line though the center of buoyancy and the vertical centerline is called the

Answer 13

metacenter

Question 14

The distance between the center of gravity and the metacenter is called

Answer 14

the metacentric height

Question 15

When the metacentric height (the distance between the center of gravity and the metacenter) is positive, meaning that the metacenter if above the center of graffiti, the center go buoyancy shifts so that is outboard of the center of gravity and the vessel is considered to be

Answer 15

stability and the forces of buoyancy and gravity will act to bring the vessel back to an uprightpoistion.

Question 16

If the center of buoyancy is inboard of the center of gravity, the metacentric height is negative, the forces of buoyancy and gravity will tend to

Answer 16

roll the vessel further towards capsize.

Question 17

If the center of gravity is not on the centerline of the vessel, the vessel will heel until equilibrium is reach with the cuter of buoyancy and the center of gravity in alignment. This condition is referred to as

Answer 17

list.

Question 18

Helling is a temoirary leaning, listing is a ___ leaning

Answer 18

permanent

Question 19

A vessel has tow principle types of stability:

Answer 19

Longitudinal and TRansverse

Question 20

A vessel is usually much longer than it is wide. Therefore, the ______ plane (___ and ___) is more ____ than its ____ plane (____)

Answer 20

longitudinal (fore and aft) stable transverse plan (beam)

Question 21

pitchpoling

Answer 21

when a vessel pitches end-over-end

Question 22

Which stability tends to keep the vessel from rolling over (capsizing)

Answer 22

Transverse (athwartships) stability

Question 23

A shipping rolling over is

Answer 23

capsizing

Question 24

Additional weight above the center of gravity increases the distance from the center of gravity up to the center of buoyancy, which _____ stability

Answer 24

decrseases

Question 25

Removal of weight from below the center of gravity

Answer 25

decreases stability

Question 26

The force that causes a vessel to return to an even keel, or upright position, is called the vessel’s

Answer 26

moment

Question 27

The force causing a vessel to react agains a tool and return to an even keel is the

Answer 27

=righting moment.

Question 28

The broader a vessel’s beam,

Answer 28

the more stable that vessel will be and the less likely it is to capsize

Question 29

As a vessel heels, the center of buoyancy moves to the lower side of the vessel forming an

Answer 29

angle of inclination

Question 30

Larger changes int he movement of the center of buoyancy will result with any given

Answer 30

angle of heel

Question 31

A vessel may also capsize when aground as the

Answer 31

volume of water beneath the vessel decreases and the vessel loses blance

Question 32

The two principle forces that affect stability are

Answer 32

static and dynamic forces

Question 33

Static forces are caused by

Answer 33

the placement of weight within the hull. Adding weight on one side of a vessel’s centerline or above it’s center of gravity usually reduced stability. Flooding or grounding a vessel makes it susceptible to statice forces with may adverse affect stability.

Question 34

Dynamic forces are caused by

Answer 34

actions outside the hell such as wind and wave. Strong gusts of wind or heavy seas, especially in shallow water, may build up a dangerous sea tending to capsize a vessel.

Question 35

A liquid that only partly fills a compartment is said to have

Answer 35

free surface

Question 36

Water in a partly filled compartment is called

Answer 36

loose water

Question 37

When loose water shifts from side to side or forward and aft due to turning, speed changes or wave actions the vessel

Answer 37

looses stability and does not want to right itself.

Question 38

If fish are free to move about inside a compartment (a commonly seen condition) this will

Answer 38

change a vessel’s stability

Question 39

To correct free surface effects

Answer 39

Minimize the number of partially filled tank
Fish wells should be completely empty or filled
Cargo such as fish should be prevented from rolling back and forth on the deck

Question 40

To correct free communication with the sea, you should

Answer 40

Patch the hull opening
Place weight on the high side to decrease the list towards the damaged side
Remove weight above the center of gravity on the damaged side

Question 41

Icing can

Answer 41

increase the displacement of a vessel by adding weight above the center of gravity and causing it to rise

Question 42

To correct for icing

Answer 42

Change course, speed or both to reduce the freezing spray and rolling
Physically remove the ice

Question 43

The entry of water into the hull resulting in progressive flooding and loss of stability is

Answer 43

downflooding

Question 44

To correct downing flooring you need to

Answer 44

keep all watertight fittings and openings secured when a vessel is underway way
pump out the water