Seamanship
Dock water allowance and loading
How much deeper you may load in dock water of a given density, and how much cargo that leaves to load at the present draught.
From the load line certificate
Hydrometer, e.g. 1010
How it works
A ship floats deeper in fresh water than in salt. The fresh water allowance (FWA, on the load line certificate, or Δ / (4 × TPC) mm) is the difference between 1,025 and 1,000 kg/m³. In brackish dock water, DWA = FWA × (1,025 − ρ) / 25: with FWA 200 mm and density 1,010, the ship may load 120 mm deeper than her load line, because she will rise that much on reaching the sea.
Cargo still to load = (allowed draught − present mean draught) in cm × TPC. Use the TPC for the dock water (TPC × ρ / 1,025) when you need it exact, and a mean draught corrected for trim and deflection.
For training and cross-checking. Not a substitute for approved navigation equipment, nautical publications and the ship’s own procedures. Calculations run in your browser and nothing you type is stored; a PDF you download is made on our server and not kept.
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