Vessel Motion

Question 1

Lateral motion is easier to detect from which position on the bridge?

Answer 1

Centerline

Question 2

Where is the pivot point of a vessel with lateral motion but no rotational motion?

Answer 2

At the Center of Lateral Resistance (CLR)

Jeff 220

Question 3

A ship’s maneuvering lever is defined by the relationship of what two forces?

Answer 3

Pivot Point and the ship’s propulsion forces

Jeff 220

Question 4

As a stopped ship gains turning momentum (tug or thruster force), what is the result in the ship’s longitudinal motion?

Answer 4

Begins to creep ahead.

Jeff 254

Question 5

A ship stopped, puts rudder hard over and ahead on engines. Where is the initial PP?

Answer 5

Within 1/8 L from bow.

Jeff 257

Question 6

What is the drift angle of a ship turning?

Answer 6

The angle in relation to the ship’s centerline and direction in which the ship’s bridge is actually traveling in a turn.

Jeff 259

Question 7

Drift angle for full-bodied ships such as bulkers is _________ than the drift angle for ships with finer, narrow hulls.

Answer 7

Larger

Jeff 261

Question 8

A ship is stopped and PP is at the CLR (close to midship). If a tug starts pushing on bow or stern to create rotation on the ship, what happens to the PP?

Answer 8

It shifts towards the end of the ship, opposite from the tug.

Jeff 252

Question 9

When conducting a turning circle, which is larger?

A. Tactical diameter
B. Final diameter

Answer 9

A. Tactical diameter

House 38

Question 10

When a vessel has a list, making a turn in the direction towards the angle of list, the turn will be:

a. Smaller, and quicker
b. Larger, and quicker
c. Smaller and take longer
d. Larger and take longer

Answer 10

d. It will take longer and result in a larger turn

House 42

Question 11

When a vessel is moving ahead, the transverse thrust:

A. Considerable, moving the stern in the direction of propeller rotation
B. Minimal, therefore this negligible effect is generally ignored.

Answer 11

B

House 43

Question 12

Define the term “headreach.”

Answer 12

The distance travelled forward over the ground, after engines are stopped

House 223

Question 13

The aim in berthing larger vessels is generally to obtain a singular lateral motion, in order to land parallel to the dock, and also, because lateral motion is easier to check than ______ motion.

Answer 13

Rotational

Hooyer 12

Question 14

As a rule of thumb on a loaded ship at full ahead on an even keel, in slack water, start reducing speed about ____ times the ship’s length, from the position in which you’d start maneuvering.

Answer 14

20x

Williamson 3

Question 15

As a rule of thumb on light ship at full ahead on an even keel, in slack water, start reducing speed about ____ times the ship’s length, from the position in which you’d start maneuvering.

Answer 15

10x

Williamson 3

Question 16

Normally a ship’s speed will need to be below what speed before starting engines astern?

Answer 16

5 kts

Will 3

Question 17

It’s best to reduce speed gradually, through each bell, in order to maintain control. This is particularly important with which type of propeller?

Answer 17

CPP

Will 4

Question 18

A ship travels 100 feet in one minute at 1.0 knot. This is equivalent to _____ nm/min.

Answer 18

0.017 nm

Will 4

Question 19

A ship with a right-hand turning propeller turns “short round” best when turning which way?

Answer 19

To starboard

Will 9

Question 20

The majority of CPP props are ____-hand turning.

Answer 20

Left

Will 10

Question 21

Pivot point for a vessel stopped is located where?

Answer 21

At the center of gravity. Will be midships for a vessel on an even keel. Further aft if trimmed by the stern.

Question 22

The “wind force moment” is the resultant moment from multiplying _____ x ______.

Answer 22

Wind force lever by the wind’s force

Will 26

Question 23

A vessel will settle in a “neutral position” when stopped, as wind and current forces are balanced. The ship will tend to return to these positions after moving away from them. For most vessels, the three neutral positions are:

Answer 23

A vessel stopped
A vessel moving forward, into the wind
A vessel moving astern, sailing with a tailwind

Herve 111

Question 24

Two “unstable neutral positions” for most vessels, which a vessel will tend to move away from, are:

Answer 24

Moving forward, with a tailwind
Moving astern, with a headwind

Herve 111

Question 25

What is the most effective method of slowing a vessel?

Answer 25

Drifting or turning

Herve 131

Question 26

How does vessel’s speed relate to the resistance of air and water as their forces affect a ship’s motion?

Answer 26

The square of relative ship speed

Herve 132

Question 27

For most vessels, an accelerating turning circle diameter (starting from a stop) is less than _____ of that for a turning circle at constant speed while underway.

Answer 27

Half

Mac 11

Question 28

Any ship significantly trimmed by the head will have what kind of directional stability?

Answer 28

Negative.

Mac 19

Question 29

Large, full-bodied ships with large block coefficients often squat to increase trim in which direction?

Answer 29

By the head

Mac 19

Question 30

Which force is more strongly felt by a vessel, bank cushion or bank suction?

Answer 30

Bank suction

Mac 21

Question 31

If a vessel in a narrow channel starts to sheer due to bank suction/cushion, what should be done?

Answer 31

Do not reduce speed! Let the head fall off towards mid-channel, and maintain some rudder towards the near bank while increasing RPM. Once heading starts a few degrees back towards center of channel, increase rudder to check swing

Mac 47

Question 32

When making a turn in a channel, begin the turn when what point on the ship is at the turning point at the end of the reach?

Answer 32

Abeam the pivot point.

Mac 74