The purpose of a Load line or Plimsoll line is to ensure that a ship has sufficient freeboard (the height from the water line to the main deck) and thus sufficient reserve buoyancy (e.g., the enclosed volume created by the area between the water-line and the main deck-line).
Note : Do Not confuse with Painting Segregation Line.
Normally, the scant draft will be defined as “Painting segregation line” and have same position with full summer load line as below:
Scantling draft is the maximum draft at which the ship can withstand all the loads safely. In other words, it is the draft at which the strength of the ship is built.
Bow/ Thruster mark
Pilot ladder mark
Answer for the question of Draft mark measurement:
Some case, we can ignore the thickness of bottom if the LCG variate not more than 0.5% in hydro-static calculation upon draft & ship lines (tuyến hình).
“For sister vessels, if the difference between lightweightdata is sufficiently small and within the accuracy or tolerance of inclining tests/ lightweight surveys (difference in lightweight is less than 0.5% and difference in LCG is less than 0.5% LBP), the lightweight data of the first vessels may be used for the sister vessel; i.e. identical final stability documentation may be accepted for the sister vessel as for the first vessel.” – DNV rule
9 thoughts on “DRAUGHT MARKS AND SURVEYING”
May I know what’s the tolerance of the position of draft mark during construction in dry dock.
Hi, as my experience, The tolerance for each Mark is max Plus (+) 2mm (SOLAS), at dry dock construction, the draft marks should be placed at the designated levels (as closely as possible) Because it will affect directly to the ship loading computer, inclining test (During the testes, all data will be set-up again within tolerance of initial design) after the ship launching. A lot of Design/ Loading data behind and affected by it. As long as the testes are satisfactory with IMO load lines requirement and depend on your yard’s design team experiences and confident.
Further details, you can visit here https://amarineblog.com/2019/08/21/draft-mark-draught-mark-inspection
Well explained about Draught Marks ..many thanks
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