This document discusses critical issues related to dry docking ships, including ensuring the dry dock is adequate for the ship and accurately determining the docking condition. It addresses factors like making sure the dock width and length can accommodate the ship. It also covers calculating dock loads based on the ship's displacement, eccentricity from its center of gravity to the blocking area, and block area. Guidelines are provided for meeting load limits per foot of dock and examples given of approximate load capacities for different types of ships and docks. Determining the correct displacement and center of gravity based on draft readings and any "ghost weight" is also summarized.

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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?