Manoeuvring- recap

Question 1

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

Answer 1

150 rpm
350-650 rpm
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 to respond to speed reductions

Cannot run at very low revs

Whole engine must be run backwards to gain astern power ie must be stopped and is limited by size of 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 fix 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

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

Answer 5

35˚ ~ 45º.

Question 6

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

Answer 6

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 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

Amidships

Question 11

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

Answer 11

Right ahead

Question 12

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

Answer 12

1/4 ship’s length from fwd

Question 13

Take a vessel proceeding astern with the wind on the port quarter – in which direction will the bow
tend to wander? Draw a diagram to illustrate your answer.

Answer 13

To starboard

Question 14

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

Answer 14

To port

Question 15

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

Answer 15

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 16

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

Answer 16

Reduction in under keel clearance

Question 17

State the cause of squat

Answer 17

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 18

State the most effective way of reducing squat

Answer 18

Reducing speed as squat varies proportionately to v²

Question 19

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

Answer 19

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

Question 20

Describe the dangers posed by interaction between two vessels overtaking one another in confined
waters.

Answer 20

iii) When the bow of the overtaking ship approaches the stern of the vessel being overtaken.
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.

iv) When the two vessels are abeam of each other.
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 21

Describe the dangers posed by interaction between two vessels passing one another in
confined waters from opposite directions.

Answer 21

i) When the bows of the vessels approach the other.
Positive pressure from the bows repel each other.

ii) When the two vessels are abeam of each other
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 22

State the two most important factors that govern interaction between vessels.

Answer 22

speed
distance apart

Question 23

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

Answer 23

Pay out more cable

Question 24

Name four devices used for securing an anchor

Answer 24

Guillotine, devils claw, brake and lashings.

Question 25

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

Answer 25

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

Question 26

State what is meant by “snubbing the cable”

Answer 26

Stopping the cable running out by use of the brake.

Question 27

State what is meant by veering cable

Answer 27

Paying out under power

Question 28

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

Answer 28

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

Question 29

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

Answer 29

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 30

How long is a marine shackle?

Answer 30

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

Question 31

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

Answer 31

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

Question 32

Describe how to execute the Anderson turn.

Answer 32

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 33

Describe how to execute the Scharnov turn.

Answer 33

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 34

Describe how to execute the Williamson turn.

Answer 34

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

Question 35

What is the Williamson turn good for

Answer 35

This method is good in restricted visibility since it takes ship away from the scene of incident.

Question 36

What is the Anderson turn good for

Answer 36

This is the fastest recovery method which is good for tight turning characteristics vessels

Question 37

What is the Scharnov turn good for

Answer 37

Can be carried out effectively when the time elapsed between occurrence of incident and commencement of maneuver is known.

Question 38

Angle of encounter

Answer 38

The angle, relative to ships head, at which the waves strike the vessel.

Question 39

What is rolling period

Answer 39

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 40

How can synchronous rolling be avoided

Answer 40

Change in vessel heading

Question 41

What is a stiff vessel

Answer 41

Large GM, will retune to the upright very quickly

Question 42

What is a tender vessel

Answer 42

Small GM, ship will return to the upright slowly

Question 43

What is hogging

Answer 43

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

Question 44

What is Sagging

Answer 44

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

Question 45

Where is positive and negative pressure

Answer 45

positive- bow
negative- along body of ship

Remember that dolphins swim at bow because they are being pushed out.