- Joined
- Feb 27, 2009
- Location
- Milan, NY 12571
Ever wonder what all those marks on the side of big vessels are? well, they trim and load lines for the diferent types of waters that vessel might operate on.
Displacement and tonnage
Acording to Archimedes principle a vessel displaces a weight of water equal to its own weight. S displacement is a measure of the vessel's weight.
it is expressed in either:
short tons = 2000lb or
long tons = 2240lb
tonnage is a measure of the load carrying capacity of carg vessels, where one ton equals 100 cubic feet of interior volume:
gross tons = volume inside watertight bulkheads
net tons = volume inside watertight bulkheads less the volume of operational spaces.
draft marks
draft marks at both bow and stern indicate the depth of the keel below the water line. A vessel that is neither trimmed down by the bow nor trimmed down by the stern can have different drafts fore and aft.
draft marks are 6" high and spaced 12" from base to base. The base of a number indicates the number of feet exactely. If the waterline is at the top of a number, the draft is the number of feet, plus six inches.
Loadlines and the Plimsoll Mark
A set of loadlines, painted at the midpoints on both sides of a vessel, is collectively called the Plimsoll Mark. The horizontal bars indicate the maximum depth to which the vessel may be loaded, depending on the season and whether the water is salt or fresh.
To one side is a circle with a horizontal bisecting bar, at the level of the summer seawater line. There may be letters at the ends of the bisecting bar which indicate the vessel's registration society or agency. In the United States, the certificating agency is the American Bureau of Shipping (ABS).
The "freshwater allowance" allows a vessel, loading for an ocean voyage in a freshwater river or lake, to be trimmed below the fresh water line if it will later rise to the apropiate salt water line.
Great Lakes Loadlines
great Lakes Loadlines- for vessels registered in the Great Lakes -are similar to the Plimsoll Mark, but with more fresh water gradations.
Displacement and tonnage
Acording to Archimedes principle a vessel displaces a weight of water equal to its own weight. S displacement is a measure of the vessel's weight.
it is expressed in either:
short tons = 2000lb or
long tons = 2240lb
tonnage is a measure of the load carrying capacity of carg vessels, where one ton equals 100 cubic feet of interior volume:
gross tons = volume inside watertight bulkheads
net tons = volume inside watertight bulkheads less the volume of operational spaces.
draft marks
draft marks at both bow and stern indicate the depth of the keel below the water line. A vessel that is neither trimmed down by the bow nor trimmed down by the stern can have different drafts fore and aft.
draft marks are 6" high and spaced 12" from base to base. The base of a number indicates the number of feet exactely. If the waterline is at the top of a number, the draft is the number of feet, plus six inches.
Loadlines and the Plimsoll Mark
A set of loadlines, painted at the midpoints on both sides of a vessel, is collectively called the Plimsoll Mark. The horizontal bars indicate the maximum depth to which the vessel may be loaded, depending on the season and whether the water is salt or fresh.
To one side is a circle with a horizontal bisecting bar, at the level of the summer seawater line. There may be letters at the ends of the bisecting bar which indicate the vessel's registration society or agency. In the United States, the certificating agency is the American Bureau of Shipping (ABS).
The "freshwater allowance" allows a vessel, loading for an ocean voyage in a freshwater river or lake, to be trimmed below the fresh water line if it will later rise to the apropiate salt water line.
Great Lakes Loadlines
great Lakes Loadlines- for vessels registered in the Great Lakes -are similar to the Plimsoll Mark, but with more fresh water gradations.