New York Minute

There's boat name for you, if you own a fast racing boat. It's slang for real quick, as in "I'll have your order in a New York minute." Johnny Carson once said it's the interval between a Manhattan traffic light turning green and the guy behind you honking his horn. I love the name but you can have it. Let me know!

Is Anyone Not Amazed?

Is anyone not amazed by Banque Populaire V's smashing of the Jules Verne record for non-stop circumnavigation, just completed? Here are the stats: 29,002 miles covered, time elapsed 45d 13h 42m 53s,  for an average speed of 26.5kts! (You want to see her going 41 knots?)

She routinely put in noon to noon runs of over 600 miles; the fastest 24 hour run by a clipper ship was 465 miles (Champion of the Seas, designer Donald McKay, in1854. This record stood until 1984.)

"Banque Pop V", or simply "BPV", is a 130 foot trimaran, 75 feet in beam, with enormous sail area and stupendous sail-carrying ability, strong enough and big enough to be able to press on at high speeds even in big southern seas. She is featured in an earlier blog entry, with a video link - great stuff.

 

She is surely among the greatest yachts ever to sail. Hats off to her and the crew.

Bulbous

Bows, that is. At higher speeds, most of the energy driving a displacement hull is wasted on wave creation, including at the bow. To the extent wave making can be minimized, the efficiency of the hull increases. The addition of a bulbous bow creates a wave ahead of the ship's normal bow wave, and the trough of the bulbous bow's wave coincides with the crest of the ship's bow wave, tending to cancel the wave out. A bulbous bow lends about 5% to the efficiency of the hull, and reduces pitching as well.

Bulbous bows add to the wetted area of the hull. At slow speeds the drag induced by wetted area is the primary impediment to hull efficiency. For this reason bulbous bows are not (apparently) suitable for sailboats, which so often travel at much less than maximum speed.

The concept is said to have been first developed by David Taylor, head of ship design for the U.S. Navy in 1910.  He noticed that the ram commonly incorporated into the bow of large combatants in that era seemed to slow the ships much less than theory predicted. While slow to catch on, bulbous bows are now ubiquitous.

The Baidarka built by Alaska's Aleuts has the unique bow depicted here. While western academics assumed the shape had some totemic significance, perhaps meant to mimic a salmon's maw, some believe it represents a bulbous bow. The efficiency of these boats is remarkable, and it seems entirely possible that thousands of years of inspired design resulted in an advance that long anticipated David Taylor's discovery.




You may think there is a flaw in the logic here - that bulbous bows are efficient only in hulls driven at the higher realm of their potential speeds, and that kayaks are slow. Think it through. A container ship and a kayak both have displacement hulls. Simplifying somewhat, the maximum hull speed of a displacement hull is known to equal 1.34 multiplied by the square root of the waterline length, at which point there is a big bow wave, a big stern wave, and a deep trough amidships - think of a tug powering along. A kayak with a 16 foot waterline length will thus have maximum hull speed of about 5.4 knots. (If you're doing the math, a container ship with a 900 foot waterline length has a maximum hull speed of 40 knots.) A powerful man could and would drive a kayak at speeds approaching 5 knots, suggesting that the bulbous bow would be a useful part of the hull. Bear in mind also that when a hull is driven by muscle, even a small addition to efficiency is normally appreciated and sought after.

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