Because there is no way of measuring the total weight of a ship. And if it was there, it's not relevant. They measure the "weight" of a ship in displacement, so the amount (tons) of water is displaces. This is usually mentioned under "normal displacement" which means fully bunkered, staffed and 2 thirds of supplies.
It implies that a ship "weighs" less if you put it in a huge vat of alcohol, as well.
AnusStapler t1_j8wbs7n wrote
Reply to TIL Gross Tonnage is Measure of a Ship’s Internal Space, Not its Weight. by theAusterityClinic
Because there is no way of measuring the total weight of a ship. And if it was there, it's not relevant. They measure the "weight" of a ship in displacement, so the amount (tons) of water is displaces. This is usually mentioned under "normal displacement" which means fully bunkered, staffed and 2 thirds of supplies.
It implies that a ship "weighs" less if you put it in a huge vat of alcohol, as well.