From The Pilot House:
The Mysterious Mark of Samuel Plimsoll

From The Pilot House:
The Mystery of Plimsoll Marks

The Water Taxis often pass through Port Everglades taking guests to many Water Taxi Cruise and Save Partners. Guests have so much to look at they often miss something interesting. This includes symbols on the sides of the large commercial vessels.

These symbols are a language of their own and they have a very interesting history. Referred to as the Plimsoll Mark, they are located on the port and starboard side of a ship. The mark was established in the 19th century by Samuel Plimsoll, a champion for mariners and member of the British Parliament. Samuel was shocked at the number of cargo ships that were sinking at sea due to overloading by greedy ship owners. The symbol is known as the Plimsoll Mark, or the Load Line. This symbol is found on all commercial ships and provides a graphic indication of how much cargo a ship can hold and still remain balanced and safe to embark on it’s journey.

Closer look at Plimsoll Mark

Here is a closer look at the universally adopted Plimsoll Mark and associated draft marks. Here is what it all means:

- The line through the circle indicates how deeply the vessel is allowed to be submerged as it is loaded. The more cargo you load, the lower the mark sinks. This vessel has just unloaded so the mark is about 6 feet above the water.
- The initials GL stand for the regulatory agency under which the vessel was built and load lines assigned, in this case Germanischure Lloyd.
- The vertical line with the horizontal hash marks and letters indicate load allowances for different geographic locations, seasons and weather conditions:

  • W – Stands for winter.
  • S – Stands for summer. A ship loaded in cold, dense water during the winter will sink down to the summer load line when floating in less dense, warmer summer water.
  • T – Stands for Tropical. “Tropical Water,” being warmer than “Summer Water,” is even less dense so the ship sinks even lower with the same load of cargo.
  • F – Stands for Fresh Water which is less dense than Salt Water.
  • TF – Stands for Tropical Fresh. A ship loaded on a tropical fresh water river to the “Tropical Fresh” line will rise up out of the water to the winter line when the ship travels to northern cold water.

- The graduated numbers and marks to the right of the Plimsoll Mark are the “Draft Marks” measured in decimeters. Whichever number is showing at the water line indicates how much of the ship’s hull is below the water line.

Markings used to keep a cargo ship level

In addition to the loading information in the middle of the hull, Draft Marks at the bow and stern indicate the “Trim” of the ship and help the loading officer position the cargo so as to keep the ship level. Think of it as a sea-saw – if you put too much cargo in one end or the other, the heavier end will sink lower than the lighter end. Ships are generally loaded so the stern or back of the vessel is slightly lower than the bow.

The system of Load Lines / Plimsoll Marks make it an easy task for regulatory authorities, insurance companies and ship owners to determine if each ship is safely loaded just by looking at the marks in relation to the water line. Note that the marks are actually welded onto the sides of the vessels to discourage over-ambitious shipping companies from repainting the marks in a more profitable location!

A properly loaded cargo ship

A lightly loaded container ship heading to sea. She appears to be properly balanced as the ship is not leaning or “listing” to one side and she appears to be floating with the proper trim.

If you are visiting Fort Lauderdale or live in the area, take a Water Taxi (link to ticketing page) to get a closer look at these ships.

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