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DRY-DOCKING
ISSUES
PRESENTED BY:
Bill Robblee
MSC TECHNICAL DIVISION

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Critical Issues
• Is the dry dock adequate?
–Determined during Tech Evaluation of proposal
–Checked at time of docking
• Accurate determination of docking condition
–For use in docking calculations

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Is The Dock Adequate?
• Dock Width > Ship’s Beam 

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Is The Dock Adequate?
• Dock Width > Ship’s Beam 
• Dock Length > Ship’s Length 
–Floating docks, ship can exceed dock length

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Is The Dock Adequate?
• Dock Width > Ship’s Beam 
• Dock Length > Ship’s Length 
–Floating docks, ship can exceed dock length
• Dock Capacity > Ship’s Docking Disp. 

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Is The Dock Adequate?
• Dock’s rated linear load/foot > loading from ship?
–Both floating and graving docks have a maximum load per
foot rating given in long tons per foot

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Dock Loads
• Determined by
–Trapezoidal Load Method
–Moment Area Method
• Both methods assume ship is infinitely stiff
• Uniform keel blocking, use trapezoidal
• Moment Area method based on eccentrically loaded
column theory

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Dock Loads
• Factors
–Ships displacement
–Eccentricity – distance between ship’s LCG and centroid of
blocking area
–Total block area

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Load per foot, fwd = W / Lkeel - 6(W)(e)/(Lkeel)2
Load per foot, aft = W / Lkeel + 6(W)(e)/(Lkeel)2

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Ways to meet load per foot limit:
• Use position 3 (minimum overhang)
• Move LCG ship by adding ballast or shifting fuel

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Approximate Dock Loads
• T-ATF: 12 tons per foot
• T-ARS: 20 tons per foot
• T-AO: 45 tons per foot (ballasted)
• T-AO: 47 tons per foot (light ship)
• T-AOE: 45 tons per foot (ballasted)
• T-AOE: 48 tons per foot (light ship)
• T-AKE: 64 tons per foot

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Dock Capacities
• Cascade General, Dry Dock 3
–26,000 tons, 46 tons per foot
• GSY
–30,000 tons, 50 tons per foot (anticipated rating)
• BAE TITAN
–52,534 tons, 60 to 70 tons per foot
• BAE OLD DOMINON
–14,000 tons, 28 tons per foot

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In-dock Period
• Changes to dock loading while in dock:
–Removing ballast
–Removing anchors and chain
–Removing props, rudders, shafts
• Effect on dock loading must be considered.

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The Docking Condition
• Displacement and LCG
–From ship’s drafts
• Vertical Center of Gravity
–From ship’s loading
–Includes “ghost weight” to make CargoMax displacement
equal to displacement from drafts

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The Docking Condition
• “Ghost Weight” – unaccounted weight
–Unaccounted light ship weight changes
–Unaccounted loads (spares, cargo, etc)
• Pier side condition, corrected to as read drafts
–Adjustments , as required, for acceptable docking condition

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Questions?