Ship Longtitudinal Centre of Gravity Position

Discussion in 'Stability' started by Robert Wilkinson, Aug 3, 2021.

  1. Robert Wilkinson
    Joined: Jan 2018
    Posts: 23
    Likes: 0, Points: 1
    Location: New Zealand

    Robert Wilkinson Junior Member

    If the Longtitudinal Centre of Gravity of a ship (without added load) is behind (aft) of it's Longtitudinal Centre of Flotation, does this affect a ships change in aft draft ?


    For change in draft aft calculations, does added weight always have to be added at Longtitudinal Centre of Flotation, parallel sinkage calculated there and then change in trim calculation for movement of weight to it's actual position done from there ?

    or

    Can an Added weight be positioned at the ships original Longtitudinal Centre of Gravity, Parallel sinkage calculated at LCG and then the change in trim calculation for movement of weight to it's actual position done from there ?


    I am thinking of a situation when it is calculated that a cargo load is to be positioned aft of the ship Longtitudinal Centre of Gravity, when the ship Longtitudinal Centre of Gravity is behind Longtitudinal Centre of Flotation.
     
  2. Ad Hoc
    Joined: Oct 2008
    Posts: 7,274
    Likes: 1,164, Points: 113, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Hi Robert,

    Yes. This also assumes the LCF and LCB are not coincident too.

    The former.
    Assuming the load is small, relative the the ships displacement, you add at the LCF to get that parallel sinkage, then, as you note, move to its correct position and calculate the chnage in trim via MCT.
    If you add at the LCG, it wont be parallel sinakage.

    Makes no difference.
    The LCG is almost never at the LCF....
     
    jehardiman and bajansailor like this.
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