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SF exam > Ship Handling- Herve Baudu > Flashcards

Ship Handling- Herve Baudu Flashcards

1
Q

Define Heave:

A

is a vertical displacement movement of the ship

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2
Q

Define Surge:

A

is a longitudinal movement

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3
Q

Define Sway:

A

is a transverse moment

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4
Q

Define Yaw:

A

is a rotational movement around the vertical axis. It involves a change of heading.

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5
Q

Define Pitch:

A

is a rotational movement around the transverse axis of the ship.It is normally a periodic movement around a median position ( the trim) caused by the ship passing through a swell coming from the front or the year

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6
Q

Define Roll:

A

is an alternating rotation movement around the longitudinal axis of the ship. Generally is caused by the swell or the sea taking the ship from the rear.

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7
Q

True or False: Generally speaking, fairly round and bluff bowed shapes turn better. Shapes that are tapered in the bows and stern have greater directional stability

A

True

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8
Q

True or False: A narrow ship more easily counters the drift which its rudder tries to create, and turns less well than a broad ship.

A

True

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9
Q

Why do ships with a high block coefficient normally have lower propulsion performance?

A

Since the flow of water through the propeller are disrupted by the solid stern shapes that generate eddies

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10
Q

Generally a ship is limited to _________ consecutive starter operations and why?

A

10 starts, and because of the compressed air capacity reserves needed for starting up.

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11
Q

True or False: the average, regulation speed for winding or releasing an anchor line is about 10 meters a minute, or one shackle every 3 minutes.

A

True

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12
Q

What is the most common type of Anchor?

A

Hinged stockless Anchor

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13
Q

Why is the port side anchor line generally longer than the starboard side?

A

Because of the unfavorable prop walk in reverse motion for a ship with a single shaft, having a fixed pitch right hand propeller.

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14
Q

One shackle is equal to ?

A

15 fathoms or 27.3 meters

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15
Q

What two categories are mooring lines divided into?

A

synthetic mooring lines and steel wire lines

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16
Q

A good mooring must resist the various forces to be applied to the ship during its stopover. These forces are caused mainly by the effects of?

A
  1. wind
  2. tide and current
  3. variations in trim, draught and list caused by commercial operations
  4. eddies caused by other ships passing nearby
  5. swell and waves, ice
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17
Q

The helm system consists of the following components?

A
  1. the rudder blade, which is the profiled, moving part underwater in contact with the water currents
  2. the bearings, which support the stock/ blade assembly
  3. the stock, which forms the rotation shaft
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18
Q

The criteria for easily defining the rudder blade are?

A
  • its surface area
  • its profile
  • its aspect ratio
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19
Q

True or False: When the steering gear fails, the rudder blade returns to midships with headway

A

True

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20
Q

Why are hydrodynamic forces greater on a rudder with stern way?

A

the point where hydrodynamic forces are applied moves towards the rear of the rudder ( the trailing edge becomes the leading edge) causing an increase in moment and therefore the mechanical force on the stock

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21
Q

How are rudders placed behind the propeller?

A

At a distance equal to the diameter of the propeller, to benefit from the acceleration of the resulting flow ( around three times the ships velocity)

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22
Q

Acceleration of the water currents over the outer surface encourages lift. The pressure zone contributes _____ of the lift force and the suction zone provides the other _______.

A

1/3 and 2/3

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23
Q

Rudder profiles are carefully designed for maximum?

A

lift and lowest possible drag

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24
Q

“thick” profile rudders encourage?

A

Laminar flow and generate greater lift.

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25
Q

What are the two main families of rudder profiles?

A
  • convex profiles

- concave profiles

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26
Q

Flap rudders can be used with as much as ___ degrees of helm

A

70 degrees

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27
Q

The turning radius for a particular ship is ______ when fitted with a becker rudder?

A

1/2

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28
Q

Becker rudders in port maneuvering, or at speeds less than 4 kts the rudder angle on ship ships may be increased up to?

A

65 degrees

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29
Q

True or False: Becker or flap rudders can be as effective as a stern thruster?

A

True

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30
Q

True or False: the kort nozzle is only suitable for ships whos speed is 12 kts and greater.

A

FALSE: above this speed drag is increased caused by the nozzle is to great.

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31
Q

The particular schilling rudder profile was designed to increase the rudder lift by?

A

extending the stall angle.

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32
Q

What is a benefit of the shilling rudder over the fin rudder principle?

A

does not have any moving parts that a source of mechanical weakness ( striking ice for instance)

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33
Q

True or False: Helm angle on a schilling rudder need NOT be limited when at Sea speed?

A

False: if the speed rises to far, a protection system maintains or returns the helm angle to values below 35 degrees

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34
Q

Schilling rudders at port speeds, the maximum helm angle may reach ____, which diverts water flow by _____, thus making the rudders action as effective as that of a bow thruster.

A

70 degrees/ 90 degrees

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35
Q

The harmful effects from cavitation can be reduced by use of a specially-adapted rudder profiles such as?

A

the specially adapted rudder profiles such as the twisted leading edge profile from Becker.

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36
Q

What are the three families propellers are divided into?

A
  • propellers
  • hydropropellers
  • voith schneider epicycloid-geared propellers
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37
Q

What are a propellers main characteristics

A

are its diameter, number and type of blades, and its geometric pitch ( angle of its blades)

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38
Q

The perfect performance of the propulsion chain assembly would have a coefficient of ?

A

1

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39
Q

True or False: Transverse thrust effect is increased the larger the diameter of the propeller and the faster it turns

A

True

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40
Q

Pitch is said to be _______ for forward motion, _______ for reverse motion, ___________ for no thrust when the ship is stopped

A

Positive, Negative, and Zero

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41
Q

Controllable pitch shaft line normally have a _______ handed propeller to gain the same turning effect as that of a right handed handed fixed propeller ship

A

Left

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42
Q

Since a propellers efficiency is better in forward motion than in reverse, the effectiveness of the twist is limited by?

A

the power from the propeller running in reverse

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43
Q

True or False: Twin screw ships are generally outfitted with two right handed propellers

A

False: This would cause to much turning torque, in general wheels are opposite pitched to counter each others prop walk.

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44
Q

When Macroscopic gas bubbles appear on the surface of the propeller blades, and when they approach the higher pressure the bubbles burst causing a sudden release of energy. This phenomenon is known as?

A

Cavitation

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45
Q

In most cases a tunnel thrusters propeller is driven by?

A

a reversible electric motor

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46
Q

At around 4 kts what percentage of efficiency has a bow thruster lost.

A

50%

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47
Q

True or False: The movement of the water mass from one side of the ship to the other causes it to start making way forward.

A

TRUE

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48
Q

True or False: A stern thruster can overcome trasnverse thrust effect.

A

FALSE: Rarely can a stern thruster overcome transverse thrust.

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49
Q

What can you do to minimize swept track?

A

Use bow thruster to turn at low speeds is an option

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50
Q

Longitudinal velocity is assessed abeam by?

A

Abeam, by observing how alignments move past

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51
Q

Changes of heading are assessed by?

A

observing from the centerline of the vessel from ahead or astern whatever is easier, depending on the position of the bridge

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52
Q

PPU stands for?

A

Portable Pilot Unit

53
Q

Any trajectory followed by a vessel when turning combines what three movements?

A

Surge, Turn, and drift

54
Q

When the vessel turns on itself, with no headway or sternway, the pivot point and the centre of rotation combine with the?

A

center of gravity

55
Q

Use of the bow thruster changes the?

A

transverse speed of the vessels bows, moving the position of the pivot point aft.

56
Q

Is a bow thruster more effective with sternway or headway?

A

Sternway

57
Q

When maneuvering, the concept of inertia leads to what two problems?

A

First and perhaps most important given the low drive power/ weight ratio is the difficulty of arresting the vessels forward movement or giving it velocity.
Second is that of acceleration or slowing the movement of a vessel, by apply forces, and thus communicating acceleration to the vessel.

58
Q

So with equal power and displacement, it may be deduced that it will be more difficult for a crude carrier to make forward way than for a container vessel because?

A

For an equal displacement a crude carrier with solid shapes will have a greater added mass than a container vessel with flowing forms.

59
Q

During the turn, the vector of the inertia force at the center of gravity is permanently behind the heading of the vessel?

A

by around 15 degrees

60
Q

The moment of inertia, the mass of the vessel and the initial velocity at the start of the turn encourages slippage in the following conditions?

A
  • the greater the velocity, the greater the inertia force
  • the higher the angular speed ( fast change of heading), the more the vessel gains centrifugal force, and then more it slips
  • the shape and draft of the vessel affect slippage: a loaded vessel with straight shapes slips much less than an laiden vessel with rounded shapes. Each vessel is a particular case, which lies between these two extremes
61
Q

How is slippage visualized?

A
  • Onboard a vessel with a stern bridge, it is difficult to perceive slippage looking at the trajectory from the outside, singe the eye of the observer moving along a great circle arc around the pivot point, is deceived by a reference system that constantly changes. Conversely looking at the trajectory from the side of the vessel inside the turn with respect to the fixed points located on one side the vessels slippage is detected much more easily.
  • Finally, if the vessel has enough velocity to create foam either side of the hull for a system of waves, after turning, the wake on the inner side of the turn is seen to be wider than that on the opposite side, thus indicating the slippage on the outside of the turn.
62
Q

It is the __________ wind whose effects are taken into account in maneuvering

A

Apparent Wind

63
Q

The instant center of windage is the point where the wind acts on the vessels superstructure. Its position varies, depending on?

A
  • wind surface (shape and surface area the vessel presents to the wind)
  • Angle of incidence (thin aerofoil theory)
64
Q

Hull Resistance is?

A

Water also exerts a hydrodynamic force that counters the movement: This is hull resistance.

65
Q

True or False: If the speed increases, the wave resistance also increases.

A

True

66
Q

A moving vessel disturbs the mass of water around it in a zone?

A

once or twice its width and about one and a half times deeper than its draft.

67
Q

The phenomena linked to hydrodynamic pressure have a number of consequences on vessel maneuvers, especially in confined and shallow waters which are?

A
  • effects of interaction when crossing or passing other vessels
  • sinkage phenomenon
  • squat
  • reduction in speed
  • increased turning radius
  • bank effect
68
Q

When turning, or maneuvering in the port, any movement of a vessel combines a?

A

longitudinal displacement, drift and rotation

69
Q

The vessel underway is therefore subject to what two external actions?

A
  • the action of the wind on the superstructure

- the action of the water on the undersides of the hull, the results of which are applied to the center of drift

70
Q

The vessels neutral position depends on?

A
  • the type of vessel
  • the speed of the vessel
  • the force of the wind
71
Q

For most vessels, there are three neutral positions of stability: the vessel will tend to return to them whenever it moves away from them

A
  • vessel stopped
  • vessel moving forward, sailing into the wind
  • vessel moving in reverse, sailing with a tail wind
72
Q

There are two unstable neutral positions: the vessel will tend to move away from these whenever it turns off its course

A
  • vessel moving forward, sailing with a tail wind

- vessel moving in reverse, with a head wind

73
Q

True of False: The confinement of the ships hull in port basins and channels restrict the space available for the water flow increases its speed. Hull resistances are considerable affected by these phenomena

A

True

74
Q

What are the several factors that contribute to local disturbance of the wind?

A
  • current meterological conditions
  • topography of the land
  • obstacles
  • time of the day
75
Q

True or False: in order to balance the transverse force and turning moment, the ship handler must create forces and moments opposed to the effect of wind.

A

True

76
Q

The three parameters characteristic the developement of swell are?

A
  • fetch or extent of its action
  • the average velocity of the wind
  • the time the wind has been active
77
Q

What number of factors can influence the ships behavior in turning?

A
  • draft
  • trim
  • sea
  • current
  • wind
  • heel
  • stability
  • engine spped
78
Q

The turning process consists of what three phases?

A
  • the maneuvering phase
  • the rotation phase
  • the turning phase
79
Q

What is normally the turning diameter of a ship with a helm angle of 35 degrees

A

3 to 5 ship lengths. May be equal to 1 for a sophisticated rudder.

80
Q

In the turn, not all points on the ship move at the same speed. How do they move?

A

the bow slow down inside the turning circle, while the stern chases on the outside.

81
Q

At running speed, a ship loses about a ______ of its velocity after a heading variation of 60 degrees. The speed then stabilises at about 60 percent of the initial speed, with a helm angle of 35 degrees

A

1/4,

82
Q

True or False: Turning is NOT the easiest and most efficient way of arresting the ships forward movement.

A

False

83
Q

It is therefore preferable, in order to tackle a turn, to being with?

A

a proportionally high helm angle, then reduce it gradually during the turn when the hull lift is established.

84
Q

True and False: The wind does NOT cause the turning curve to flatten and the tactical diameter to decrease in size

A

False: the wind does cause the turning curve to flatten and the tactical diameter to increase

85
Q

Always set one centered ________ on the next course before turning and leave it there during the whole turn.

A

EBL

86
Q

What is the IMO’s regulatory criteria for directional stability?

A

the instability loop must be below 12 degrees when the ships length/ speed ration reaches 45 seconds.

87
Q

Squat becomes significant when this ratio of depth-to-draught is under?

A

1.5 times the vessels draft.

88
Q

In practice, when on board, the signs for identifying the squat effect generally are?

A
  • the speed of the vessel, which falls, with no change to the engine speed
  • the vessel pushes on the water. The accompanying waves increase in size and in some cases can break and create a bore phenomenon on the banks of the channel.
  • The vessels trim changes and it squats
  • the radius of turn and stopping distance increase and the helm control is more sensitive
  • the propeller performance falls, vibration increases, pressure on the blades varies and the engine load is unstable
89
Q

When crossing or overtaking another vessel, it is also important to preserve a minimum distance between the vessels of?

A

equal to the width of the larger of the two, and of at least 30 meters.

90
Q

Define Current

A

Current is the horizontal movement of a mass of water to a given place.

91
Q

True or False: Fresh water exerts less pressure on the hull because it is less dense

A

True

92
Q

As a first approximation, hydrodynamic pressure forces are distributed all around the hull in?

A
  • a main over pressure zone forward and, to a lesser extent aft
  • a low pressure zone in the center
93
Q

The closer the ship is to the bank, the more the effect becomes?

A

pronounced and is difficult to control.

94
Q

Hydrodynamic pressure zones can be felt to about?

A

one ships width, ether side of the hull

95
Q

Does the blockage factor change for two ships passing in a narrow channel?

A

Yes, for the same volume of water, the sum of the volume of the two ships is much greater than the volume of each one of them.

96
Q

Good Holding bottom are?

A

clay, hard silt, sand

97
Q

Average holding bottom are?

A

coarse sand, gravel, broken shells, short weeds

98
Q

Poor holding bottom are?

A

Long weeds, soft silt, rocks

99
Q

In order to improve the ships holding at the anchorage, the anchor shank should not be?

A

Lifted off the ground.
5 degree left, loss of 15% holding power
15 degree lift, loss of 50% holding power

100
Q

The following average values may be used for anchoring in water depths

A
  • depth over 20 meters pay out 3 to 5 depth
  • depth below 20 meters pay out 5 times the depth
  • increase the length of chain in bad weather.
101
Q

Visual elements for observing whether the ship is dragging:

A
  • the chain tightens and relaxes abrupt and jerkily
  • the ship comes to its neutral position (across the wind)
  • the ship leaves its turning zone ( anchor alarm)
  • the ship may also drift with the current or swell as it increases
102
Q

Under test conditions ( ship under maximum load, at full sea speed) what is the stopping distance a ship must have?

A

15 ship lengths, maybe increased to 20 for VLCC’s. In practice it is usually nearer 10 ship lengths

103
Q

At maneuvering speed _________, reversing of the engine is reliable and the engine gives its full power very quickly in reverse

A

7 kts or less

104
Q

The rudder no longer controls the ships trajectory, as it becomes inefficient because of the eddies generated by?

A

cavitation on the propeller

105
Q

The flexibility of a CPP achieved by quickly reversing the angle of the blades is at the cost of?

A

Less efficiency in reverse than a fixed pitched propeller ( often around 50% of the available power in forward motion)

106
Q

Diesel propulsion gives maximum power in reverse, which is not the case for a?

A

Steam powered ship

107
Q

Every 90 degree change of heading reduces the vessels speed by about ________% once the engine is stopped

A

40%

108
Q

A tugs traction force is measure as a static force called?

A

Bollard Pull

109
Q

What force can a tug create that a thruster cannot?

A

Longitudinal force when working on its line, thrusters are only capable of transverse thrust.

110
Q

What is the benefit of a longer tow line vs. a short tow line for an assist tug?

A

The action reaction principle means that they therefore cause a pressure force on the ships hull which directly opposes the tugs traction. The higher the power developed by the tug and the shorter its towline, the greater this effect is ( up to 50% of the traction).

111
Q

Speed during escorts is an important issue, escort towing is carried out for length passages, during which the ship maintains a high speed, often more than ___ kts

A

10 kts

112
Q

The solas convention requires crude carriers and gas tanker ships, whose dead weight is more than 20,000 tons to have an?

A

Emergency towing arrangement

113
Q

True or False: Despite the duties and obligations of a pilot, his/ her presence on board does not relieve the master or officer in charge of the navigational watch of their duties and obligations for the safety of the ship.

A

TRUE

114
Q

Using a helicopter for pilotage operations assists?

A
  • Safety at sea
  • Safety of transfer
  • flow of traffic
115
Q

When pilot hoisting operations take place near the bridge the ________ must be shut down

A

Radar

116
Q

The combined control of these two “engine speed/ ships speed” concepts is vital when maneuvering. What are the three possible situations?

A
  • the ships speed matches the engines speed
  • the ships speed is less than that matching the engine speed
  • the ships speed is greater than that matching the engine speed.
117
Q

True or False: Over 4 kts, the helm action combined with the engine is normally more effective in starting a turn than is the bow thruster.

A

True

118
Q

True or False: The further away the pivot point is from the centre of the ship, the smaller the turning circle is.

A

False: When the pivot point is at the center, the turning radius is zero and the ship pivots on the spot.

119
Q

The resources available that generate transverse forces and turning moments are?

A
  • Bow thruster
  • rear thruster
  • prop walk
  • Rudder
120
Q

When turning it is important to concentrate on the trajectory of the ___________?

A

Pivot Point

121
Q

True or False: In practice, if the ship is stopped, the pivot point merges with the center of gravity at the middle of the ship

A

True

122
Q

Berthing port side to the wharf without a thruster the approach to the wharf is at an angle of?

A

About 20 to 25 degrees.

123
Q

What happens if the forward spring becomes taught before vessels head way is stopped when berthing?

A

The bow will violently be slammed into the dock.

124
Q

Berthing starboard side to the wharf without a thruster the approach to the wharf is at an angle of?

A

The approach to the dock is at a slight angle, some ten degrees with regard to the point where the middle of the ship is located, because the prop walk effect is away from the dock and the water streams from the propeller running in reverse create a water wedge effect between the ship and dock side.

125
Q

The technical choice made for moving off the dock depends on what several factors?

A
  • whether or not there is a bow thruster

- the space available in front of the ship and the port layout

126
Q

When getting under way port side to the wharf how much angle to the dock should be developed before going astern?

A

when the ship is atleast 30 degrees to the dock

127
Q

Inertia is ___________ to the weight of the ship, but increase with the __________ of the speed

A

Proportional, Square

128
Q

True or False: GPS velocity measurement during a turn is therefore often misinterpreted. It depends on the position of the antenna with respect to the pivot point.

A

True

129
Q

Visibility on the bridge: ships over 45 m long must comply with the following provisions

A
  • the view of the surface of the sea ahead of the bows from the bridge shall be unobstructed for over two ships lengths or over 500 meters
  • the horizontal field of view from the bridge shall be 225 degrees with an acceptable blind are angle of 20 degrees (lifting gear)
  • the horizontal field of view from the main helm control must be 60 degrees either side of the ships axis.

SF exam (14 decks)

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