Vessel Stability

1
Vessel Stability

• Dan Hardin
• Commercial Fishing Industry Vessel Safety
  Coordinator
• U. S. Coast Guard
• Marine Safety Office, Seattle WA

2
Vessel Sinking

• Oct 1, 1998 - 36 crabber.
• Working south of Point Roberts.
• Generator stops while 2 crew recover pots.
• Owner stated he saw water in the E/R.
• Before being able to do anything the vessel
  sinks.
• 2 POB were picked up by nearby fishing vessel.

3
Vessel Sinking

• Oct 1, 1998 - 28 crabber.
• Working south of Point Roberts (within 1 hour of
  first vessel).
• Vessel heels to stbd, crab pots on deck shift,
  before vessel can recover, vessels rolls to stbd
  and sinks.
• 2 POB were picked up by nearby fishing vessel.

4
Vessel Sinking

• 30 Oct 97, 58 Seiner coming into Bellingham
  Bay.
• 4 persons on board (2 deceased/2 missing).
• F/O Tanks near empty, vessel to go in to DDX.
• Fish hold partially full of fish/ice slurry.
• Towing a seine skiff, up close on aft deck, tied
  off low on deck and attached to boom up high.
• Oversize drum for vessel/house mods extended.

5
Bellingham Seiner
6
Overview

• Watertight Integrity
• Vessel Subdivision
• Vessel Loading
• Intact Stability
• Damage Control

7
Stability

• The ability of a vessel to return to the upright
  position after being heeled by an external force.

8
Heel
9
Heel
10
Heel
11
Heel
12
Heel
13
Heel
14
Heel
15
Why boats float

• The weight of a boat
• equals
• the weight of water it displaces

16
Why boats float

• The weight of a boat
• equals
• the weight of water it displaces

17
Why boats float

• The weight of a boat
• equals
• the weight of water it displaces

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Buoyancy
19
Buoyancy
20
Buoyancy
21
Buoyancy
22
Buoyancy
23
Buoyancy
24
Buoyancy
25
Buoyancy
26
Buoyancy
27
Buoyancy
28
Buoyancy
29
Buoyancy
30
Maintaining Watertight Integrity

• Goal To provide the vessel with a proven means
  to minimize the effects of flooding.

Page 5
31
Maintaining Watertight Integrity Vessel Hull
32
Bulkhead deck
The uppermost deck to which watertight bulkheads
extend, commonly the main deck.
Page 5
33
Watertight Hatches Doors

• Watertight closures prevent water from entering
  the watertight enclosure of the hull.
• Water is extra weight reducing vessel freeboard
  and increasing free surface effect dangers.

Page 7
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Watertight Hatches Doors

• Know the location of all watertight closures.
• Inspect all watertight closures for condition.

Page 7
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Watertight Hatches Doors

• Inspect the operation of dogs, gaskets and
  sealing surfaces.

Page 7
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Watertight Hatches Doors

• Closures should be closed and dogged while
  underway unless actually in use, to prevent
  downflooding.

Page 7
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Watertight Hatches Doors

• Dont allow cargo or deck gear to block
  weathertight closures or any other doorway

Page 7
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Watertight Hatches Doors

• Dont paint gaskets.
• Inspect to ensure gaskets remain in serviceable
  condition.
• Inspect and grease dogs regularly.

Page 7
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Watertight Hatches Doors

• Always keep portlights closed and deadlight
  covers secured when at sea.

Page 7
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Downflooding
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Downflooding
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Downflooding
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Downflooding
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Downflooding
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Downflooding
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Downflooding
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Downflooding
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Downflooding
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Downflooding
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Downflooding
51
Recommend Practices

• Watertight condition of the deck, house and side
  shell must be maintained.
• Discharge piping penetrating the hull should be
  fitted with check and positively closing valves
• Inlet piping should be fitted with positive
  closing valves located at the shell plating.
• Deckhouse openings should be fitted with
  weathertight doors.

Page 6
52
Recommended Practices

• Doors should be steel or equivalent material
  permanently attached to the bulkhead
• Weathertight doors should open outward and be
  fitted with a minimum or two dogging devices in
  addition to hinges.
• All emergency doors should be quick acting.
• Propulsion machinery spaces above the bulkhead
  deck should be watertight.

Page 6
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Maintaining Watertight Integrity Vessel
Subdivision
54
Subdivision
Watertight transverse bulkheads up to bulkhead
deck down to the keel
Page 5
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Subdivision
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Subdivision
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Subdivision
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Subdivision
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Recommend Practices

• Vessel should be subdivided with collision
  bulkhead and watertight bulkheads.
• Collision bulkhead be stepless and intact up to
  the bulkhead deck. (No doors/scuttles)
• Penetrations shall include valves operable from
  aft of the collision bulkhead and above the
  bulkhead deck.
• All pipe penetrations shall be as far inboard and
  high as practicable
• Minimize the number of pipe penetrations.

Page 8
60
Recommend Practices

• Ensure watertight bulkheads watertight.
• Machinery spaces should be enclosed by W/T
  bulkheads (Engine room, auxiliary equipment).
• W/T bulkheads with openings should be quick
  acting W/T doors and should always be kept
  closed.
• Watertight doors should open outward from the
  machinery space.

Page 5-6
61
Vessel Loading
Freeing ports
Deck
Freeboard
Draft
Page 9
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Vessel Loading
Adding weight reduces freeboard and
reduces reserve buoyancy
Page 9
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Vessel Loading
Reserve buoyancy lost
Page 9
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Vessel Loading
Reserve buoyancy
Page 9
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Vessel Loading
Reserve buoyancy lost
Page 9
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Vessel Loading
Reserve buoyancy lost
Page 9
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Recommended Practices

• Keep weight low in the vessel.
• Avoid adding weight above the main deck.
• Secure gear and catch to prevent loads from
  shifting.
• Limit duration of side lifting operations.
• Minimize number of partially filled tanks.
• Do not overload.
• Keep freeing ports clear.

Page 9
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Stability
69
Center of Buoyancy
B
Page 10
70
Center of Buoyancy
The point through which the force of buoyancy
acts vertically upwards (B)
B
Page 10
71
Center of Gravity
Center of Gravity (G) is a downward force
G
B
Page 10
72
Center of Gravity
(G) rises and falls when weights are
moved, added, and/or removed.
Fish
G
B
Page 10
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Center of Gravity
G
B
Fish
Page 10
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Metacenter
G
B
Page 11
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Metacenter
Can be considered as being the pivot point when
the vessel is being inclined.
M
G
B
Page 11
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Metacenter
Page 11
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Metacenter
Page 11
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Metacenter
Page 11
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Metacenter
Page 11
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Metacenter
Page 11
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Metacenter
Page 11
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Roll PeriodShorter Roll Period
Stable
M
G
B
The distance between G and M referred to as GM is
the Metacentric Height
This vessel has positive GM
Page 11
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Roll PeriodLonger Roll Period
Unstable
G
M
B
This vessel has negative GM
Page 11
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Uncontrolled Weight Movements
M
G
Page 12
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Uncontrolled Weight Movements
M
G
Page 12
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Free Surface Effect
M
G
Page 13
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Free Surface Effect
M
G
Page 13
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Free Surface Effect
M
G
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Unsecured Loads
Live Tank
M
G
B
90
Unsecured Loads
Live Tank
M
G
B
91
Recommended Practices

• Limit free surface effect by minimizing the width
  of tanks and the number of partially filled
  tanks.
• Install bin boards in center of wide fish holds.
• Secure all loads.
• Devise a system to secure each item like crab
  pots while loading or off loading.

92
Maintaining Intact StabilityGoal To maintain
intact stability of your vessel at all times of
operation

• Adequate intact stability
• Established when the vessel is built and
  initially outfitted for operation.
• When the vessel at rest possesses characteristics
  of the stable condition.
• Intact stability is considered to be adequate if
  GM is 2.
• Older vessels designed with GM 1.6 to 2. Check
  with a marine architect.

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93
Recommended Practices

• Ensure vessel maintains adequate intact stability
  prior to getting underway, will be a tremendous
  benefit when vessel is exposed to forces of
  fishing and the sea.
• Have vessel stability evaluated by a qualified
  individual.

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Important Factors Affecting Vessel Stability
M
G
B
Page 14
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Important Factors Affecting Vessel Stability
M
G
B
Load Height
Page 14
96
Recommended Practices

• Minimize the height of traps or pots on deck.
• Ice can collect on traps increasing Center of
  Gravity.

Page 14
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Important Factors Affecting Vessel Stability
Live Tank
M
G
B
Live Tanks on Deck
Page 14
98
Recommended Practices

• Minimize the width and the number of live tanks.

Page 14
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Important Factors Affecting Vessel Stability
Live Tank
M
G
B
Suspended Weight
Page 15
100
Important Factors Affecting Vessel Stability
Live Tank
M
G
B
Page 15
101
Important Factors Affecting Vessel Stability
Live Tank
M
G
B
Vessel slips out from beneath weight
Page 15
102
Important Factors Affecting Vessel Stability
Live Tank
M
G
B
Restrain load to prevent vessel slip
Page 15
103
Recommended Practices

• Minimize the duration of these operations.
• Exercise extreme caution when lifting over the
  side or quarters as change in center of gravity
  is even more significant.
• Ensure to prevent the suspended weight from
  swinging to mitigate adverse effects.

Page 15
104
Important Factors Affecting Vessel Stability
High Tow Points
Page 16
105
Recommended Practices

• After deploying, shift the towing point to a
  lower location.
• Maintain the tow on the longitudinal center line
  of the vessel (directly behind the vessel).
• Avoid towing off the quarter or beam.

Page 16
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Damage Control
107
Hull Breaches
Page 18
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Chafed Hose
Page 19
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Chafed Hose
Page 19
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Chafed Hose
Page 19
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Damaged Through Hull Fitting
Page 20
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Damage Control Kit
Page 22
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Summary
114
Vessel Sinking

• Oct 1, 1998 - 36 crabber.
• Working south of Point Roberts.
• Generator stops while 2 crew recover pots.
• Owner stated he saw water in the E/R.
• Before being able to do anything the vessel
  sinks.
• 2 POB were picked up by nearby fishing vessel.

115
Vessel Sinking

• Oct 1, 1998 - 28 crabber.
• Working south of Point Roberts (within 1 hour of
  first vessel).
• Vessel heels to stbd, crab pots on deck shift,
  before vessel can recover, vessels rolls to stbd
  and sinks.
• 2 POB were picked up by nearby fishing vessel.

116
Vessel Sinking

• Oct 97, 58 Seiner coming into Bellingham Bay.
• 4 persons on board (2 deceased/2 missing).
• F/O Tanks near empty, vessel to go in to DDX.
• Fish hold partially full of fish/ice slurry.
• Towing a seiner skiff, up close on aft deck, tied
  off low on deck and attached to boom up high.
• Oversize drum for vessel/house mods extended.

117
Bellingham Seiner
118
THE END