Tugs General - Shiphandling Facts and Rules Flashcards

1
Q

Tugs General - HP to BP
(MacElrevey)

A

100 HP = 1 ton bollard pull (MacElrevey)

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2
Q

Tugs General - BP to 100BHP by tug
(Henson)

A

VS: 1.0 tons / 100bhp
ASD: 1.3 tons / 100bhp
Conventional:
- w/ nozzles: 1.5 tons / 100bhp
- w/ open prop: 1.1 / 100bhp
(Henson pg 79)

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3
Q

Tugs General - ship speed for conventional tug

A

maximum 3 kt ship speed

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4
Q

Tugs General - negatives for pulling

A
  • may part line
  • poor lead for ships in ballast
  • wave surge puts shock load on line (Hooyer pg 60)
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5
Q

Tugs General - tug position in turn

A

tug pushing forward on shoulder less effective than on quarter because of pivot point and hydrodynamic forces forward opposing the turn

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6
Q

Tugs General - Conventional and Omni positioning

A

use conventional forward and omni aft

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7
Q

Tugs General - VS and ASD positioning

A

use ASD forward and VS aft (except if more braking force is needed)

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8
Q

Tugs General - bow in maneuver tug position - same type

A

1 or 2 tugs same type - use stronger tug forward

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9
Q

Tugs General - stern in maneuver tug position - same type

A

1 or 2 tugs same type - use stronger tug forward

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10
Q

Tug Use in Port - AST / Voith tractor assist
(Henson)

A
  • Voith better at stern indirect towing at higher speeds
  • ASD better as forward tug and at stern direct towing at speed (100% thrust any direction)
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11
Q

Tug Use in Port - main types of tug assistance
(Henson)

A
  • tugs towing on a line, usually 1.5x length of tug
  • tugs operating at the ship’s side made fast with 1, 2, or 3 lines
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12
Q

Tug Use in Port - Voith assist towing/pushing switch
(Henson)

A

can switch from towing on line to pushing, forward or aft, at ship speed of 2 kts or less

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13
Q

Tug Use in Port - IMO escort heeling regs
(Henson)

A

requires tugs engaged in escort operations with the max heeling lever in an equilibrium situation, heeling angle 15º or less

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14
Q

Tug Use in Port - line pull relationship to bollard pull
(Henson)

A
  • if prop RPMs double, then line force will increase by a factor of 4 and required engine power will increase by a factor of 8
  • applies to most tug ops
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15
Q

Tug Use in Port - towline length
(Henson)

A
  • should be as long as possible
  • tugs lose 40-60% on short towline
  • in heavy wave conditions could lose up to 90%
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16
Q

Tug Use in Port - tug assist line strength
(Henson)

A
  • should be 4-6x tug’s BP rating
17
Q

Tug Use in Port - center of pressure relation to tow point and heel
(Henson)

A
  • the smaller the distance from center of pressure vertically to the towing point will reduce heel
18
Q

Tug Use in Port - propulsion point relation to tow point and heel
(Henson)

A
  • longer distance from propulsion point vertically to tow point will counteract heel
19
Q

Tug Use in Port - ASD vs. Voith escort brake / steering forces
(Henson)

A
  • ASD tugs brake better
  • Voith tugs steer better
20
Q

Tug Use in Port - minimum tug GM height
(Henson)

A
  • minimum recommended metacentric height is 3m
21
Q

Tug general - whistle signals from ship - One short blast
(Slesinger)

A
  • if stopped - “come ahead”
  • if going ahead or astern - “stop”
22
Q

Tug general - whistle signals from ship - Two short
(Slesinger)

A
  • “back your engine”
23
Q

Tug general - whistle signals from ship - Three very short blasts
(Slesinger)

A
  • “more speed”
24
Q

Tug general - whistle signals from ship - One prolonged blast
(Slesinger)

A
  • “slow speed”
25
Q

Tug general - whistle signals from ship - One long and two short blasts
(Slesinger)

A
  • “let go the tug”
26
Q

Tug general - radio communication commands must…
(Slesinger)

A
  • identify tug
  • direction and amount of force to be applied
  • desired push/pull angle
  • verify receipt, understanding, and implementation by tug
27
Q

Tug general - radio communication command terms to avoid
(Slesinger)

A
  • “on” - use “towards” instead
  • “off” - use “away” instead
  • “full” - use power in thirds, “slow, one-third, two-thirds, etc.”