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Trimming - как считать trimming table

To calculate the trim changes you should have next information:
Additional weight (W (MT)) – in our case it is 100 MT, but can be any other;
Suppose the ship is in the even keel position;
LBP (m) – length between perpendiculars;
LCG (m)– distance from the midship to the gravity center of the hold or any other compartment on the vessel;
Draught (D (m)) – specific draught for what you want to perform calculation;
TPC (t/cm) – draught change Tones Per Centimeter for draught D;
MCT (t*m/cm) – Moment to Change Trim for draught D;
LCF – Length to the Center of Flotation from midship.

If LCG or LCF are in forward to midship, you must be positive, otherwise – negative.

New draught will be: Dnew=D+W/TPC/100;

Distance between LCG and LCF: L=LCG-LCF;

Trim change: ∆T=W*L/MCT/100;

New draught at forward: Dfwd=Dnew+∆T/(LBP/(LBP/2-LCF));

New draught at aft: Daft= Dnew-∆T/(LBP/(LBP/2+LCF));

And finally:

Forward draught change: ∆Dfwd=Dfwd-D;

Aft draught change: ∆Daft=Daft-D;

Of course, you can make a perpendicular to draft mark correction then, but it will be only tiny part of millimeter correction. I never use it.

If you want to create trimming table, you have to repeat this calculation sequence for each draught and each compartment.

If you are working with general, not bulk cargo, LCG better to replace with distance from midship to frame that matches with gravity center of load unit.

I use small excel template for trimming table preparation and also I have built small but smart program for ship trimming while loading/discharging or ballast operations which works on data from trimming table. This program is used by more than hundred vessels today. I distribute it as freeware so, if some one will need it, I can share it.



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