Recap-Key questions

Question 1

State the range of engine revolutions at which the following diesel engines run.
(i) a slow-speed engine
ii) a medium-speed engine
(iii)a highspeed diesel engine

Answer 1

i) 150rpm
ii) 350-650 rpm
iii) 900-1200 rpm

Question 2

What are the advantages of a slow-speed diesel engine?

Answer 2

Good at developing ahead power
Connected directly to prop shaft – no need for gear box, easier maintenance and
Cheaper to build
Cheaper to run as they burn heavy fuel oil

Question 3

What are the disadvantages of a slow speed diesel engine?

Answer 3

Poor response to speed reductions
Cannot run at very low revs
The whole engine must be run backwards to gain astern power ie must be stopped and is
limited by the size of the air bottle
Runs at pre-set revs
Gas Turbine engines fitted to some Pax Ships, very responsive to speed
changes, 90% power operating astern

Question 4

Describe a fixed-pitch propeller

Answer 4

Cast in one piece
Fixed pitch
Pitch/angle of blade varies from root to tip
Designed to run at a particular speed

Question 5

Describe a controllable pitch propeller (CPP) or variable pitch propeller

Answer 5

Cast as a number of separate pieces
Each blade bolted onto the central boss
Pitch varies from root to tip
Designed to give optimum performance over a range of revs

Question 6

State at what point in general (ie at how many degrees) a single rudder would stall.

Answer 6

35˚ ~ 45º

Question 7

Name and sketch an example of a variable profile rudder

Answer 7

Schilling

Question 8

State how a variable profile rudder differs from a single rudder

Answer 8

Effective over a much larger angle ie stalls @ around 70º

Question 9

Name one other type of rudder that increases the effective angle that it will operate through and state
how this is achieved

Answer 9

Active rudder – achieved by the addition of an independently moveable flap.

Question 10

Approximately where is the pivot point on a stationary vessel lying at an even keel?

Answer 10

Amidhsips

Question 11

What does the pivot point on a stationary vessel lying at an even keel coincide with?

Answer 11

Centre of gravity

Question 12

Where does P move to when the vessel first starts to move ahead?

Answer 12

Right ahead

Question 13

Where will P move to when the forward motion overcomes the water resistance and the vessel is moving at a uniform speed?

Answer 13

1/4 ship’s length forward

Question 14

Take a vessel proceeding astern with the wind on the port quarter – in which direction will the bow
tend to wander?

Answer 14

To starboard

Question 15

Which way would a vessel moving ahead tend to turn with a wind on the port beam?

Answer 15

To port

Question 16

A vessel proceeding on the starboard side of a shallow river may experience a “bank effect”. State
how this would affect the vessel.

Answer 16

The forward pressure area is partially constrained on the obstructed (stbd) side causing the
bow to be pushed away (to port) The negative pressure aft of the pivot point results in the
stern being sucked in towards the river bank.

Question 17

Squat is not an increase in draught. State what it is

Answer 17

A reduction in under keel clearance

Question 18

State the cause of squat

Answer 18

Increased speed of water flow under the hull causes a drop in pressure which leads to a loss
in buoyancy causing a fall in W/L immediately adjacent to the water envelope which leads to
the loss of UKC.

Question 19

State the most effective way of reducing squat

Answer 19

Reducing speed as squat varies proportionately to v²

Question 20

State how “bow cushion” effect assists a vessel when navigating in the confines of a canal.

Answer 20

It will help to keep the vessel central provided the vessel is restricted on both sides.

Question 21

Describe the dangers posed by interaction between two vessels overtaking one another in confined
waters when the bow of the overtaking ship approaches the stern of the vessel being overtaken.

Answer 21

Positive pressure from the bow acts on the stern and the rudder of vessel being overtaken
causing the latter to want to sheer across the path of the v/l overtaking.

Question 22

Describe the dangers posed by interaction between two vessels overtaking one another in confined
waters when the two vessels are abeam of each other

Answer 22

The negative pressure areas will cause the vessels to be drawn or sucked in towards each
other whilst the positive pressure areas at the bows will cause the bows to turn away from
each other.

Question 23

Describe the dangers posed by interaction between two vessels passing one another in
confined waters from opposite directions when the bows of the vessels approach each other

Answer 23

Positive pressure from the bows repel each other

Question 23

Describe the dangers posed by interaction between two vessels passing one another in
confined waters from opposite directions when the two vessels are abeam of each other

Answer 23

The positive pressure from the bow of ship A will act on the stern and rudder of ship B causing the bow to shear towards the passing vessel A

Question 24

State the two most important factors that govern interaction between vessels

Answer 24

• Speed
• Distance apart

Question 25

State the initial action that the Master might take if your vessel drags her anchor

Answer 25

Pay out more cable

Question 26

Name four devices used for securing an anchor

Answer 26

Guillotine, devils claw, brake and lashings

Question 27

State what type of organisation determines the number and size of anchor (s) and length of cable that the vessel must carry.

Answer 27

Classification Society (ie Lloyd’s Register, amongst others)

Question 28

State what is meant by “snubbing the cable”.

Answer 28

Stopping the cable running out by use of the brake.

Question 29

State what is meant by veering cable

Answer 29

Paying out under power

Question 30

State what is meant by “short stay” and “long stay”.

Answer 30

Almost up and down, little weight on cable, – cable taught, almost horizontal, a lot of
weight on the cable.

Question 31

State what information the Master would give the OOW before going to stations to anchor the vessel

Answer 31

Which anchor
Depth of water
Amount of cable to be veered
Whether anchor to be lowered just clear of hawse pipe or to water’s edge.

Question 32

How long is a marine shackle?

Answer 32

27.432 meters (27.5 meters), 90 feet, 15 fathoms

Question 33

A crew member has been reported as missing. State what type of turn would the OOW execute and
give reasons for your choice

Answer 33

Scharnov turn because it takes less time to carry out than the Williamson turn.

Question 34

Describe how to execute the Anderson turn.

Answer 34

Wheel hard over towards MOB till ship’s head has changed by 250°. Helm amidships
Slow v/l down by use of main engines

Question 35

Describe how to execute the Scharnov turn

Answer 35

Wheel hard over – either way.
When ship’s head has changed by 240° helm hard over to opposite side.
When 20° short of reciprocal track midships wheel and steady up on new course.

Question 36

Describe how to execute the Williamson turn.

Answer 36

Wheel hard over towards MOB.
When the ship’s head has changed by 60° put the helm hard over opposite way.
When 20° short of reciprocal track midships wheel and steady up on new course

Question 37

What turning method is best for restricted visibility and why?

Answer 37

Williamson turn since it takes ship away from the scene of incident

Question 38

Which turn is the fastest recovery method?

Answer 38

Anderson turn

Question 39

What is a wave period?

Answer 39

The time interval, in seconds, between the passage of successive wave crests relative to a stationary observer

Question 40

What is the angle of encounter?

Answer 40

The angle, relative to the ships head, at which the wave strikes the vessel

Question 41

What is the rolling period?

Answer 41

Time taken in secs, to roll from the max angle of heel on one side through the upright and to the max angle of heel on the other side

Question 42

How can synchronous rolling be avoided?

Answer 42

Changing in heading

Question 43

What is meant when a vessel is said to be ‘stiff’?

Answer 43

A large GM and will return to the upright very quickly

Question 44

What is meant when a vessel is said to be ‘tender’?

Answer 44

A small GM and will return to the upright slowly

Question 45

What is hogging?

Answer 45

Vessel bends from the midships area meaning bow and stern are lower in the water.

Question 46

What is sagging?

Answer 46

Vessel bends from the midships area meaning bow and stern are higher in the water

Question 47

What is fixed pitch?

Answer 47

The propeller is cast as one piece with a central
boss and a number of blades permanently fixed to it. The angle the blades make to the
line of the shaft gently changes between the root, (where it is fixed to the boss), and
the tip. This angle is termed the ‘pitch’. As such they are designed for operating at a
particular speed so that each part of each blade is delivering the optimum thrust at that
speed.