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Coxswain - St Joseph > Towing > Flashcards

Towing Flashcards

1
Q

Forces are also considered ___

A

Types of resistance

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2
Q

___ forces cause a towed vessel to resist motion

A

Static

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3
Q

The ___ of a towed vessel determines the amount of force working against the vessel

A

Displacement or mass

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4
Q

Inertia is ___

A

The tendency for a vessel at rest to stay at rest

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5
Q

The moment of inertia occurs when ___

A

A towed vessel resists effort to turn about a vertical axis to change heading

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6
Q

An attempt to tow a distressed vessel ahead and ___ at the same time should not be used

A

Change its heading

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7
Q

Overcome the effects of static forces by ___

A

Starting a tow slowly, both on initial heading and changing heading

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8
Q

Dynamic forces occur once ___

A

The towed vessel is moving

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9
Q

Dynamic forces are based on ___

A

The towed vessels characteristics, the motion caused by the towing vessel, and the effects of waves and wind

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10
Q

Once a vessel moves in a straight line, it wants to keep moving in a straight line

A

Momentum

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11
Q

The greater its displacement or the faster it is moving, the harder it is to ___

A

Stop or change the vessel’s direction

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12
Q

Once a vessel’s heading begins to change, it wants to keep changing in that same direction

A

Angular momentum

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13
Q

The faster the towed vessel’s heading changes, the harder it is to ___

A

Get the tow moving in a straight line

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14
Q

The key to dealing with momentum is to ___

A

Anticipate how momentum will affect the towed vessel’s motion and apply an offsetting force early and gradually

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15
Q

As a vessel moves, the layer of water in immediate contact with the hull moves. Due to friction between water molecules, the layers of water close to the hull try to drag along

A

Frictional resistance

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16
Q

As speed increases, frictional resistance becomes ___

A

Turbulent

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17
Q

Turbulence takes additional energy, and ___

A

More speed requires even more power

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18
Q

Frictional resistance will constantly affect the tow, normally ___

A

Keeping some steady tension in the towing rig

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19
Q

Frictional resistance is managed with ___

A

Towing speed

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20
Q

Frictional resistance also varies with ___

A

Hull shape

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21
Q

Different hull shapes react to motion through the water in different ways

A

Form drag

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22
Q

A large amount of lateral resistance, spread evenly over the length of the hull, will hinder ___, but will help ___

A
  • Effort to change a towed vessel’s direction

- Offset angular momentum in steading up on a desired heading

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23
Q

A towed vessel may be able to help offset form drag by ___

A

Using its rudder

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24
Q

Going from displacement speed to planing speed, or back, can ___

A

Decrease the towed vessel’s stability and cause it to capsize

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25
Q

Wave drag could slow the hull down to displacement speed and cause a severe ___

A

Shock-load

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26
Q

A ___ forms at the bow while the hull moves through the water

A

Surface wave

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27
Q

The size of the bow wave increases as speed increases, causing the wave to create resistance for the bow to be pulled or propelled through the water

A

Wave-making resistance

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28
Q

___ is the rapid, extreme increase in tension on the towline, transferring through the tow rig and fittings to both vessels

A

Shock-load

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29
Q

The frictional forces of wave drag, spray drag, and wind drag act on ___

A

The hull, topsides, superstructure, and rigging

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30
Q

Wind and wave drag also cause a distressed vessel to make ___

A

Leeway

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31
Q

Motion in a downwind direction

A

Leeway

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32
Q

Wave drag depends on the ___

A

Normal wetted surface area of the hull and the amount of freeboard exposed to wave action

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33
Q

In large seas, combination of wave drag and form drag could overcome the ___

A

Towed vessel’s forward momentum and cause the towed vessel to stop and transfer a large amount of strain to the tow rig

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34
Q

In head seas the towing vessel can only control the effect of wave drag by ___

A

The speed and angle that the towed vessel encounters the waves

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35
Q

In following seas wave drag causes the towed vessel to ___

A

Speed up as the crest approaches, increasing speed to keep tension in the towing rig, and reducing spped as the crest passes

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36
Q

Spray drag adversely affects the towed vessel’s motion by ___

A

Imparting a momentary heel, pooling on deck or in the cockpit, and possibly forming ice

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37
Q

A steady beam wind can cause ___, while a severe gust can cause a ___

A
  • List and leeway

- Threatening heel

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38
Q

List, heel, and leeway may cause a towed vessel to ___

A

Yaw

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39
Q

A headwind increases ___

A

Tow rig loading in a direct line with the towed vessel while the towed vessel crests a wave, causing shock-loading

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40
Q

Reducing towing speed will ___

A

Lower frictional resistance, form drag, and wave making resistance; lower tow-rig tension. In head seas reduce wave drag, spray drag, and wind drag

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41
Q

Getting the vessels in-step will ___

A

Cause the vessels to gain and lose momentum at the same time, minimizing shock-loading

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42
Q

To get the vessels in step ___

A

Lengthen rather than shorten the towline if possible

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43
Q

When operating near bars and inlets, getting the vessels in step may be impractical due to rapidly changing depth and contours. ___ may be used

A

Counteracting shock-load

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44
Q

Lengthening the towline will ___

A

Reduce the effect of shock loading via catenary and stretch length

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45
Q

The weight of the line causes a dip in the line called a ___

A

Catenary

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46
Q

Catenary causes ___

A

Energy from shock loading is spent on flattening out the catenary before being transferred through the rig and fittings

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47
Q

Depending on the type of towline, another 50’ of towline length will give ___

A

5’-20’ more stretch to act a a shock absorber

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48
Q

Tow on a course to keep the seas ___

A

30 - 45 degrees either side of dead ahead or dead astern

49
Q

Setting a course to lessen the effect of the seas may require ___

A

Tacking to either side of the actual desired course

50
Q

Deploying a drogue may help to prevent the towed vessel from ___

A

Rapidly accelerating down the face of a wave

51
Q

A drogue does add ___ to the tow, but could prevent ___

A
  • Form drag

- Shock-load

52
Q

___ instead of other synthetic fiber cordage should be used for a good combo of strength and stretch

A

Nylon

53
Q

Towlines are usually ___

A

2-in-1 DBN, 2-4” in circumference, up to 900’

54
Q

Towline is typically secured to the reel with ___

A

Small stuff

55
Q

Unless slipping the towline in an emergency, keep at least ___ turns of towline on the reel

A

4

56
Q

Inspect towlines for ___

A
  1. Cuts
  2. Chafing
  3. Flattening
  4. Fusing
  5. Snags
  6. Hardening
57
Q

Fusing of towline is caused by ___

A

Overheating or over-stretching

58
Q

Hardening of towline is caused by ___

A

Heavy use

59
Q

Towing pendants and bridles are made from ___

A

DBN or Kevlar

60
Q

Pendants and bridles should have a breaking strength ___ than the towline

A

Equal to or greater than

61
Q

A pendant is used to ___

A

Reduce wear and chafing at the towline end

62
Q

A pendant must be long enough so the ___

A

Towline is clear of obstructions on the towed vessel

63
Q

A bridle is used when ___

A

Both legs can be rigged to exert an equal pull on the hull of the distressed vessel

64
Q

A bridle is preferred for ___

A

Heavy weather towing

65
Q

Use a long bridle when ___

A

The best attachment points for the towed vessel are well aft, but maintain a fair lead forward to reduce chafe

66
Q

The amount of tension on each bridle leg increases with the ___

A

Size of the angle between the bridle legs

67
Q

Keep the legs of the bridle long enough so the angle of the legs stays less than ___

A

30 degrees

68
Q

The bridle legs must be long enough to reduce ___

A

Towed vessel yaw

69
Q

When deploying the drogue ___

A

Pay out all 200 feet

70
Q

When recovering the drogue ___

A

Bring the towed boat to a stop

71
Q

Vessels with a large superstructure forward or outboard engines will tend to lay ___

A

Stern-to the wind

72
Q

Vessels with deep draft and low superstructure will tend to lie ___

A

Broadside to the seas

73
Q

Before starting the approach, an ___ is established

A

Imaginary danger zone

74
Q

The size of the danger zone depends upon ___

A

The conditions and the arrangement of the distressed vessel

75
Q

Safe distance keeps you out of the ___

A

Danger zone

76
Q

The position taken by the rescue vessel which allows the crew the safest opportunity to pass the towing equipment

A

Optimum position

77
Q

Optimum position provides ___

A

Better vessel control, while keeping appropriate distance, and maintaining a safe escape route

78
Q

A 90 degree arc; 45 degrees forward and aft of your tow bitt

A

Maneuvering zone

79
Q

Staying in the ___ keeps you out of the danger zone and gives you a way out

A

Maneuvering zone

80
Q

It is preferable not to make opening and closing maneuvers when ___

A

Lines are over (except the heaving line)

81
Q

Avoid making correcting maneuvers on the ___

A

Face of a wave

82
Q

Tow veers to one side or the other

A

Yaw

83
Q

Ways to minimize yaw include ___

A
  1. Change scope
  2. Adjust trim
  3. Decrease speed or alter course
  4. Deploy a drogue
  5. Use a bridle
84
Q

Max safe towing speed

A

1.34 x square root of length at waterline x 0.9

85
Q

4 conditions encountered when towing in current

A
  1. Head current
  2. Tail current
  3. Cross current
  4. Combo of currents
86
Q

Depending on the velocity of the head current and the speed of the tow, SOG may be ___

A

Reduced, stopped, or even reversed

87
Q

If the current opposes wind and seas the seas get ___

A

Steeper and break more readily

88
Q

A head current increases ___

A

The strain on the tow rig

89
Q

When towing in a waterway with bends and turns, the greatest current will be to the ___

A

Outside of the bend

90
Q

At a bend the water will be deepest ___

A

On the outside of the bend

91
Q

At a bend, the towed vessel may ___

A

Sheer or yaw to the outside of the bend

92
Q

Prevent towed vessel sheer by ___

A

Reducing the length of towline prior to entering narrower sections of a waterway

93
Q

Current flowing the same direction as the course steered

A

Tail current

94
Q

Compensate for tail current by ___

A

Taking early action

95
Q

In a narrow channel if the towing vessel gets into an area of lesser current than the towed vessel with a following current, the tow ___

A

Sheets off along the axis of the current, possibly causing slack in tow rig, loss of firm control, and potentially overrunning the towing vessel

96
Q

A current that is flowing from either side, across the intended track

A

Cross current

97
Q

A cross current will require the towing vessel to ___

A

Adjust heading for set and drift for both vessels

98
Q

During a cross current the towed vessel should ___

A

Steer into the current if able

99
Q

Cross current can be minimized by ___

A

Shortening tow, offsetting track up current, and the towed vessel steering into the current

100
Q

Two methods of switching to a side tow

A
  1. Drop tow method

2. Transition method

101
Q

When a tow is about to sink you should ___

A

Break the tow and rescue the people

102
Q

If the sinking boat is unable to disconnect the tow you should ___

A

Cut towline or slip the towline by breaking the bitt

103
Q

If you have to cut the towline, cut it ___

A

Directly aft of the tow bitt

104
Q

If there were no onboard the tow, the water is shallow (less than the length of towline), and it is safe, a sinking tow should ___

A

Be allowed to pay out until the tow reaches the bottom. A floating object should then be attached to the end of the towline

105
Q

Do not attempt to break the bitt if there is ___

A

A strain on the towline

106
Q

When shortening tow in heavy weather, set a course of ___

A

10 to 15 degrees off the seas with the tow to windward

107
Q

When shortening tow in heavy weather, divide your attention ___

A

80% aft and 20% forward

108
Q

When a boat is pulled sideways by an opposing force

A

Tripping

109
Q

Static forces of towing

A
  • Inertia

- Moment of Inertia

110
Q

Dynamic forces of towing

A
  • Momentum
  • Angular momentum
  • Frictional resistance
  • Form drag
  • Wave-making resistance
  • Wave drag
  • Spray drag
  • Wind drag
111
Q

Prior to towing, what environmental information should be collected?

A
  • Marine forecast
  • Currents and tides
  • Daylight and darkness
112
Q

What communication should be made with the tow prior to arriving?

A
  • ETA
  • Advise to wear PFDs
  • Deck layout, fittings & backing plates
  • Ask for info the distressed crew thinks is important
  • Ask if anything has changed since last comms with OPCON
  • Ascertain heightened sense of urgency
  • Advise further comms will be conducted on scene
  • Set up comms schedule
113
Q

What communication should be made with the tow once on scene?

A
  • Concerns
  • When & how equipment will be sent
  • Explain plans and pass safety instructions
  • Describe the approach
  • When & how the tow rig will be passed
  • Tow rig instructions
  • Inquire about type/condition of tow connection points
  • Emergency breakaway procedures
  • Emergency signals
114
Q

What should be evaluated on the vessel to be towed prior to passing gear?

A
  • Compare vessel’s drift rate to your own
  • Confirm # of POBs & PFDs
  • Circle vessel to see condition
  • Look at vessel shape and how it lays to the seas
115
Q

Opening-by-Pivoting

A
  1. Pivot bow 45° towards boat
  2. Back away till bow even with boat’s bow
  3. Bow back into the elements
  4. Return to optimum
116
Q

Opening-by-Backing

A
  1. Back square to conditions
  2. Pivot away from boat after bow is clear
  3. Move ahead to optimum
  4. Pivot square into the elements
117
Q

Closing-by-Backing

A
  1. Back square to the conditions
  2. Pivot bow towards boat
  3. Move ahead to optimum
  4. Pivot square into elements
118
Q

Closing-by-Quartering

A
  1. Pivot away from boat
  2. Tend line off quarter
  3. Square up in optimum

Coxswain - St Joseph (8 decks)

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