Plimsoll

A fundamental aspect of seaworthiness, but one which a yachtsman may forget, is reserve buoyancy. A square rigger deeply laden with cargo did indeed "batten the hatches" before going to sea, for if a hatch gave way in heavy weather the ship would likely founder. Modern sailing yachts are light, with ample freeboard, and thus can take on a good deal of water before going under.

Samuel Plimsoll (1824 - 1898) was a member of the British Parliament who worked for the safety of mariners, work which led to a law requiring a mark on the side of every British ship beyond which it could not be loaded. The U.S. adopted the practice in 1929 (Load Line Act of 1929), and the Load Line Convention of 1966 has been adopted by almost all maritime nations.

The modern Plimsoll Mark is depicted above. A ship floats lower in fresh water, which is about 97% as heavy per unit volume as seawater, so a ship leaving the Caribean to enter the fresh water of the Panama Canal's Lake Gatun will lose considerable freeboard. It is interesting to note that Winter North Atlantic requires the most freeboard - the most reserve buoyancy - evidence of the awful conditions met by ships on that run.

The bisected circle to the left of the Plimsoll Mark carries the initials of the ship's classification society, whether American Bureau of Shipping (ABS), Bureau Veritas or, in the case of the illustration, Lloyd's Register.

In the U.S., commercial ships greater than 79 feet in length and engaged in foreign trade must have a marked load line, and carry a load line certificate. The actual certification is undertaken by the ABS. U.S. Naval ships are exempt from load line regulations, but they do carry an amidships mark which limits loading. It looks like an asterix.

Professional Mariner magazine gives the annual Plimsoll Award: "The Plimsoll marks on ships today are an enduring testimony to his tireless pursuit of safety at sea. Professional Mariner proudly presents its Plimsoll Awards each year to individuals and organizations that embody the spirit of Samuel Plimsoll." So great was Samuel Plimsoll's contribution to the safety of life at sea.








Tonnage

In England sailors until fairly recently described a yacht as, for example, a "seven ton cutter." That didn't mean a yacht weighing seven tons, but rather a yacht with a useful interior space of about 700 cubic feet, a "ton", as used in that context, equaling 100 cubic feet.

Lots of folks are confused by tonnage terms. Here are the four fundamental measurements.

Gross tonnage measures the interior space of the ship, including most non-cargo spaces. One of these "tons" equals 100 cubic feet. As I understand it, the term is derived from "tun", a great fat barrel holding 256 gallons of water or wine, and requiring about 100 cubic feet of stowage space per tun.

Net tonnage is the useful cargo space of a ship, with again one ton equaling 100 cubic feet. Generally, net tonnage is the ship's gross tonnage minus engine spaces, shaft alleys, crew quarters etc. There are, as the normally very dry Knight's Modern Seamanship puts it, "some annoying variations" among nations in what spaces are disregarded to find net tonnage, but these variations are disappearing in the face of international conventions, including the International Convention on Tonnage Measurement of Ships. Net tonnage is important not only because it describes the cargo carrying capacity of the ship, but because canal fees, harbor charges etc. turn on net tonnage.

Displacement is the weight of the water displaced by the ship, which is, as Archimedes realized, equal to the ship's weight. Generally, not always, yachts are described by their displacement.

Deadweight tonnage (DWT) is a measure of how much weight a ship can safely carry, disregarding the unloaded, unfueled, unprovisioned weight of the ship ("lightship weight") but including not only cargo, but also stores, fuel, water etc. The term is sometimes confused with displacement but the two terms mean entirely different things.

Yacht Names

 I've written about yacht names before, see the January 21, 2010 post. Here are a few that have occurred to me lately. Feel free to use or suggest them - perhaps you'll let me know by comment if you do.


Trice  Trice, an old English usage of uncertain etymology but dating to at least the 1500's, means at once or instantly. It could be the name of a fast cruising boat.

Brant   A brant is a sort of seagoing goose common to New England.Bird names make good boat names - Herreshoff's Meadowlark, Shearwater and countless others come to mind - but I don't think I have seen a transom bearing the name Brant. Brant has a good bold sound, a bit in your face; I like it. 

Tipping Point   Here's a phrase that is very much in vogue just now. Maybe a clever name for someone's first sailing yacht, about which purchase - and use - he is a bit nervous.

Pierhead Jump   A sailor who signs on for a voyage with little forethought and without knowing much at all about the ship or the skipper has made a pierhead jump. It's a good salty name for a boat bought without a lot of deliberation.

What thoughts went into the naming of your boat? Have you lately seen a name you thought was just great? Do you, like me, see my post linked above, think there are rules to the naming of boats, or does anything go? Post a comment!

The Shipping Man

A friend of mine, Matt McCleery, has written a book - The Shipping Man. It's a nice tale of a money manager's sudden infatuation with owning a ship, apparently a disease with no hope of cure. It made me want to be "A Shipping Man" too!


I really liked the book. Good plot, good characters, well crafted, and an education to boot. Here's a link:

http://www.amazon.com/Shipping-Man-Matt-McCleery/dp/0983716307

Lifeboat

 While picking up my son (he who can tie a bowline with his feet) at Massachusetts Maritime Academy, I saw some modern lifeboats and took a few pictures.

Modern lifeboats are completely covered and have diesel engines. The propellers are shrouded in Kort nozzles, for the safety of people in the water.

I like this picture. On cargo ships and tankers the lifeboat is often mounted on rails over the stern, and when the lever is pulled the boats flies down the rails and into the sea. That's a boat you don't want to miss.



This lifeboat has a capacity of 76 persons, each strapped into a padded seat. Not comfy, but a lot better than an open boat.

The steering station. The silver tube to the left of the helmsman is the exhaust pipe.