Ship constant

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Ship Constant

The ships constant is the difference between a vessels design lightship and it's actual displacement when empty. The ships constant is determined by a draught survey. The ships constant will vary over the life of the vessel.


Unintentional Reasons for Variations

  • Sedimentation in ballast or fuel oil tanks
  • Corrosion
  • Fouling of hull
  • Coating build-up (paintwork, tank coatings, etc.)
  • Garbage collection, particularly in cargo holds
  • Wear and tear of mechanical devices

Other Reasons for Variations

Effect of a Ships Constant

Generally, a ships lightship value will increase over time; particularly for vessels with large cyclical passenger loads, ships prone to corrosion, and ships which aren't regularly dry-docked. One estimate of lightship increase is a rate 0.5% per annum. Additional inclining tests should be performed after any substantive additions, relocation, or removal of weights, as well as periodically over the life of a vessel.

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