Size Matters

When size really does matter

Written by Godfrey Dykes

© RN Communications Branch Museum/Library

With the QUEEN ELIZABETH class of British aircraft carriers now approved, at least as hulls but not necessarily as viable operational warships but have a look here first Carrier waves Jan 2010 the designer(s) would have had to address two international SIZES (dimensions) in those criteria of build, but not a third which designers of Ocean Liners have had to address.

A Liner, as opposed to a Cruise Ship, is called such because it sails on a direct route to ONE PORT - in a Line so to speak, and the line almost always used is called a Great Circle Line. Britain still has a Liner and she is called the RMS Queen Mary 2, running on a Line between Southampton and New York. There are very few others, and their demise was brought about by the commercial aeroplane. The port of New York and the downtown Manhattan west side terminals (in the Hudson River) are bread-and-butter to the Cunard Liner, and to get to them the QM 2 has to pass under the Verrazano-Narrows Bridge which connects Brooklyn and Staten Island (two of the five New York boroughs) together - the bridge is the longest suspension bridge in the USA, longer than the Golden Gate Bridge in San Francisco. The overall height of the Liner is therefore a governing factor in its design and the QM 2 clears the bridge comfortably with 25 feet to spare. This is a picture of that bridge (Staten Island bottom, Brooklyn top, so Manhattan to the left) and its height above the sea at the mid channel point of the Narrows at Mean High Water (MHW) is 228 feet - QM 2 overall height keel to funnel is 236 feet - draught = 33 feet = 203 feet water line to funnel.

The two international sizes mentioned above are covered by the words 'PANAMAX' and 'CAPESIZE' which all designer of ships build into their creations. The first word relates to the BEAM of a ship and the second word to the DRAUGHT (or Draft which is often used) of a ship, beam relating to WIDTH and draught to DEPTH. Width matters only in the PANAMA CANAL and depth matters only in the SUEZ CANAL. Originally, 'Capesize' was coined meaning that if the draught was too large for the Suez Canal, the ship would have to sail around the Cape of Good Hope to get access to the Indian Ocean and all points East. In keeping with the word 'PANAMAX', the word 'CAPESIZE' is also known as 'SUEZMAX'.

Added on the 30th July 2015. The new Suez Canal parallel channel has been built and completed and will be opened for traffic from the 5th August 2015. Click on the image below to listen to an audio file which outlines the details.

Taking the two Canals as separate entities and starting with the Suez Canal which handles much larger ships than does the Panama Canal, NO passenger ship (Liner or Cruise Ship) has a problem or even a near problem with Draught. VLCC's and ULCC'S (Very Large Crude Carriers and Ultra Large Crude Carriers (super tankers) with draughts as much as 72 feet (well over twice that of QM2)) can use the Canal. The Suez Canal connecting two seas together, or more correctly one Sea (Mediterranean) and one Gulf (Gulf of Suez) which automatically leads to a Sea (Red) is 100 miles long Port Said to Port Suez. The other restrictions placed upon ships using the Canal (overall height and beam) are very generous - overall height considerably greater than that of the QM2 - and no ship (wanting to use the Canal) should exceed them, this despite the enormous size of ships today in the 21st century. However, there are two other 'potential' problems, one being the cost of using the Canal and the other, the Dead Weight Tonnage (DWT) allowed. It is almost amazing to know that just 8% only of world trade passes through this canal - security and cost are primary causes. Whilst each type/size of ship using the Canal pays a going-rate, the average cost per ship is a massive $250K USD one way. Warships frequently pay over the going-rate because to ensure safety of passage, they are regularly assigned escorting tugs. DWT is one of the many misunderstood criterions of sea commerce and it is nothing to do with the DISPLACEMENT (War Ship) or Gross Tonnage (Merchant Ship) but only to do with safety.....is the ship loaded with cargo, fuel, fresh water, ballast water, provisions, passengers, and crew (or not as is the case) such that the ship's PLIMSOLL Line is sitting on or is above the water level ? DWT does not apply to war ships. The allowance for DWT is 210,000 tons. Thus a tanker registered as being 80,000 tons takes on a bunkering 'a cargo of oil' of the maximum permissible weight, resulting in the ship weighing 290,000 tons. Whilst the word 'SUEZMAX' governs all ship measurements, none of the restrictions imposed affects the passage of 99.85% of the world's shipping either now or to come! I have transited the Suez Canal many times in both directions and in 1956 I won my first campaign medal there when I was just 18 years of age.

We cannot move seamlessly from one Canal to another, not simply because of geographical distances involved but because the Panama Canal, when compared to the very simple no locks Suez Canal is so complex (even though just less than 50 miles long overall connecting two Oceans together) that its modus operandi is almost mind-blowing . Just for example, the Pacific Ocean is only 8 inches higher than the Atlantic but each time a ship transits the very short canal it takes nearly 23 million imperial gallons of fresh water (from artificial lakes) which is then ditched (lost) to the open sea. In the South American rainy season the lakes overflow but in the dry season their water levels are a cause for concern. Before I begin this section let me tell you of a little instance which happened to me while in a Panama lock coming home from a commission in the Far East (based on Singapore) in the submarine Auriga in 1968. The Wireless Office (Radio Room) is a secret place mainly because it is where all the coding and decoding of sensitive wireless messages took place. Whenever the office was empty, the door was shut and locked even at sea and the key(s), on a lanyard, were kept on the duty radioman's person or on the radio room boss' person - which was me. Otherwise, the keys were kept on the 'Important Keyboard' under the control of an officer and were only issued against a signature. I was on the top of the conning tower of the submarine (sail fin), goofing and observing the comings and goings of personnel and machines in the process of lowering my submarine just 8 inches to the level of the Atlantic when I decided to climb down on to the casing below (the submarines main upper deck) to go for a walk-about. During the climb down inside the sail fin, the lanyard snagged, torn my trousers, pulled the keys out of my pocket and broke the connector which was an Inglefield clip similar to the fastening device used on flags for their hauling up and down a mast. The keys fell down bouncing as they went off various pieces of metal until they disappeared onto the ballast tanks at the very bottom, and then into the lock (into the sea). I immediately reported my bad luck to the officer-of-the-watch on top of the sail fin, but by that time an attempted retrieval was ruled out especially when we were one of two smallish vessels in the lock waiting to exit. We were able to get a spare set of keys from the 'important keyboard system' and after an official report was submitted, we, the skipper and I, put it down to experience. Those keys are probably still in the bottom of that lock, the first lock East about (the Miraflores locks second stage) even to this very day.

Now for those mind-blowing details told my way! I have stated that the Pacific is higher in level by 8" above the level of the Atlantic. In the simplest of terms, we could draw this as follows.

However, that assumes that each stretch of water (before and after the lock) is of uniform level. What happens if we say that the total distance between the Atlantic and the Pacific is 50 miles and that the longest stretch of level water is 30 miles? The other 20 miles are anything but uniform in level and the water supply is either not available or uncertain !

Clearly we have to engineer these variables so that they are navigable. Believe it or not, this is what they did.

For the first 8.2 miles from the Pacific end it was relatively easy going except for a bridge (Bridge of the Americas) which had to be built. Then over two locks measuring 1.1 miles they raised the water level upwards by 54 feet. After another mile they again raised the water level by another 31 feet. In this area they built an artificial lake which would act as a header-tank giving them plenty of water. By this stage, just 10.3 miles in from the Pacific the water level was now 85 feet above sea level. For the next 30 miles of a level but twisting and bending waterway (the whole canal orientated in a NW to SE direction), they created the main level of the Panama Canal. After a total of 40.3 miles from the Pacific they built an artificial lake (by damming an existing way course) again to ensure plenty of water available, three further locks, and lowered the ships 85 foot 8 inches back to sea level, this time the Atlantic's sea level. So, the whole operation looks like this.

That's it in a nutshell, oh, all except for the 25 odd thousand deaths (yes, thousand) of the men who built this through jungle and almost impossible conditions.

Now today, there is a major rethink and a requirement for a new system if the Panama Canal is to stay in business into the next decades. Something like 34% of all ships are now post-panamax ships and cannot use the Canal because of their size. Unlike the Suez Canal where the average cost to use it is $250K USD, the Panama average cost is just $54K USD. That post-panamax figure is on the increase and it is not only the narrowness of the locks which are the cause of the trouble, it is also a water problem (or rather to stop wasting water in the Canal) and that bridge I have just mention above (Bridge of the Americas) will also cause problems if ships are much larger. Many millions of dollars are earmarked for a proposed new system and it will be interesting to watch it develop over the next ten years or so.

In the animation below you will see four ships being processed leaving the Pacific bound for the Atlantic. This is the first of three locks along the 50 mile long canal, which is called the Miraflores Locks and has two lifts each of 27 foot - this is the top lift so the waterway you see ahead, an artificial lake providing the water for the locks, is 54 foot above the sea level of the Pacific Ocean. Note the large white bridge ahead (above the red hulled ship) which is called the Centennial Bridge under which all ships pass. In the sequence you will see the lock levels lowering and raising, the lock gates opening and shutting, the tugs in attendance, the people watching on the viewing gallery. Note also the little grey coloured locomotives which run on parallel railway lines to the locks and which pull the ships into the locks: ships leave the lock under their own power. Just like the Suez Canal, ships queue both ends to await a single file traffic journey. Click on your REFRESH button to start the animation from the beginning. Enjoy.