EXAM 1

Question 1

Defn: The distance from the center of buoyancy (B) to the transverse metacenter (M)

Answer 1

Metacentric Radius (BM)

Question 2

Defn: The plane defined by the intersection of the ship’s hull with the surface of the water. The enclosed area of the hull at the waterline in square feet.

Answer 2

Waterplane OR Area of the Waterplane (AWP)

Question 3

Formula: Metacentric radius (BM)

Answer 3

BM = Moment of Inertia / Volume

BM = I / V

Question 4

A vessel with G below M is said to have what kind of stability?

Answer 4

Positive stability

Question 5

How is GM found aboard a ship?

Answer 5

By referencing the stability booklet

Question 6

Defn: A line perpendicular to the keel, passing through the intersection of the stem and the summer load line.

Answer 6

Forward Perpendicular (FP)

Question 7

A ship with G above M is said to have what kind of stability?

Answer 7

Negative stability

Question 8

Defn: The point at which all the vertically downward forces of weight are considered to be concentrated; The center of mass of the vessel.

Answer 8

Center of gravity

Question 9

Defn: The weight that must be loaded to increase (or discharge to decrease) the mean draft by one inch.

Answer 9

Tons per Inch Immersion

Question 10

Formula: Quarter Mean Draft

Answer 10

M/M/M = Avg Fwd + Avg Aft + (6)Avg Mid

8

Question 11

Defn: The intersection of a vertical line through B with a line drawn through the keel (K) and the center of gravity (G). The point to which G may rise and the vessel will still have positive stability.

Answer 11

Metacenter (M)

Question 12

Defn: The height of the center of gravity above the keel

Answer 12

KG

Question 13

Defn: Transverse stability of a vessel for small angles of inclination (up to 10 degrees)

Answer 13

Initial stability

Question 14

A ship that has no righting tendency (GZ = 0) i.e. if heeled over from a wave will remain at that angle until it is acted upon by another wave from an opposite side, that vessel is said to have __________ stability.

Answer 14

Neutral stability

Question 15

Formula: Volume (V)

Answer 15

V = Displ. x 35 ft-t

OR

V = Length x Breadth x Depth = L x B x D

Question 16

Defn: The vertical distance between G and M. Used as a measure of initial stability, denoted as GM.

Answer 16

Metacentric height (GM)

Question 17

Defn: The midway point between the forward perpendicular and the after perpendicular.

Answer 17

Midships Point

Question 18

Formula: Righting Moment (RM) What are its units?

Answer 18

= Displacement / Righting Arm RM = w / d Foot-tons

Question 19

What is the term used for a ship with a smaller GM?

Answer 19

‘tender’

Question 20

A vessel where G and M are at the same height has what kind of stability?

Answer 20

Neutral stability

Question 21

Formula: Area of the Waterplane (AWP)

Answer 21

AWP = L x B x p

OR

AWP = TPI x 420

Question 22

Formula: Waterplane Coefficient (p)

Answer 22

p = Area of the Waterplane = AWP

Length x Breadth L x B

Question 23

Formula: GG’

Answer 23

GG’ = w x d

final displ

Then:

KG = initial KG +/- GG’

Question 24

Formula: Area of the Waterplane (AWP)

Answer 24

AWP = Tons Per Inch Immersion (TPI) x 420

Question 25

Defn: A line perpendicular to the keel, passing through the rudder post.

Answer 25

After Perpendicular (AP)

Question 26

Defn: The point at which all the vertically upward forces of buoyancy are considered to be concentrated; The geometric center of volume of the immersed portion of the vessel.

Answer 26

Center of buoyancy

Question 27

Formula: Height of the Metacenter (KM)

Answer 27

KM = KB + BM

Question 28

Defn: The condition where the fore-aft mean draft is greater than the midships draft.

Answer 28

Hogging

Question 30

Defn: The true measure of a vessel’s stability for small angles of inclination up to 10 degrees.

Answer 30

Righting Moment (RM)

Question 31

If a ship will heel over until it reaches the angle where KG equals KM, at which point it will stop and rest at that angle of heel it is said to have _________ stability.

Answer 31

Negative stability

Question 32

Formula: Metacentriz Height (GM)

Answer 32

GM = GZ

sin ø

Question 33

Formula: GZ (Righting Arm)

Answer 33

GZ = GM sin ø

Question 34

Defn: The vertical distance of the metacenter with the keel of the vessel. Varies with Draft and with Angle of Inclination Supplied by the shipbuilder in the ship’s stability booklet

Answer 34

Height of the Metacenter (KM)

Question 35

What is the term used for a ship with a larger GM?

Answer 35

‘stiff’

Question 36

Formula: Center of Buoyancy (KB)

Answer 36

KB = Draft x .53 (Merchant ship)

KB = Draft x .50 (Barge)

Question 37

Defn: The ability of a vessel to right itself after being acted upon by an outside force The tendency or ability of a ship to right itself when heeled to one or the other side.

Answer 37

Stability

Question 38

If GZ is said to be an ‘upsetting arm’ then a vessel has what kind of stability?

Answer 38

Negative stability

Question 39

A ship that when heeled over by external forces will attempt to right itself is said to have ________ ________.

Answer 39

Positive stability

Question 40

Defn: The condition where the midships draft is greater than the fore-aft mean draft.

Answer 40

Sagging

Question 41

Formula: Theory of Moments

Answer 41

KG = total moments

total final displ

Question 42

Formula: Moment of Inertia (I)

• Barge
• Merchant ship

Answer 42

I = (L x B³) (Barge)

12

I = L x B³ x K (Merchant ship)

Question 43

Defn: The length of a horizontal line drawn from G to the line BM. Always perpendicular to BM. Found in the cross curves or statical stability curves.

Answer 43

Righting Arm (GZ)