As 1st A/E on a large container vessel you should be familiar with the vessel's stability and the concepts of same. Regarding trimming of a vessel, and the location of the LCG, LCB and LCF, in which direction, and about which point, will the vessel trim based upon their relative locations?
• Longitudinal Center of Gravity (LCG) vs Longitudinal Center of Buoyancy (LCB) – which one moves and which one is fixed for a given loading condition • Longitudinal Center of Flotation (LCF) – what it represents and why it’s important for trimming • How a ship trims: does it rotate about LCF, LCB, or LCG when weight is added or removed off-center fore and aft
• First, recall what the LCF physically represents on the waterplane and how a vessel tends to pivot when trimming bow-up or bow-down • Compare the positions of LCG and LCB: if LCG is forward of LCB, will the ship tend to trim by the head or by the stern? Why? • Ask yourself: during a small change of trim, which point stays nearly fixed on the water surface as the ship rotates? That will tell you the axis of trim.
• Be clear on the definition of LCF: it is the centroid of the waterplane area and is usually the pivot point for trim calculations • Verify which center (LCG, LCB, or LCF) is associated with buoyant force, and which is associated with weight • Make sure your chosen option matches BOTH: correct direction of trim (head vs stern) AND correct pivot point (LCF vs LCB vs LCG) – one wrong part makes the whole option incorrect.
No comments yet
Be the first to share your thoughts!