Collin
February 22nd, 2006, 00:32
For many a century the mariners stories of mountainous seas had been poo-pooed by the scientist, who within their safe abodes had said that the stories were just a load of bunkum and could prove it with mathematics. This all changed when the New year day wave hit.
Out in the North Sea on a oil platform a fella had mounted a wave height radar to monitor the height of the waves.
On January 1st 1999 during a gale this fella was surprised to see on the tracer a wave height measurement of just under 30 metres. Over the next three months, a further 20 plus waves were recorded around this height from the same oil rig.
When this info began to filter through the scientific and naval community a study was made using a satellite. After 10 passes 28 waves ranging in height from 24 - 30plus metres were discovered.
It soon became apparent that this was a three point problem.
The waves had very deep troughs on either side, they didn't obey the general wave rule of motion, and they travelled faster than the normal wave.
Normal waves generally go in the direction of the wind and don't reach higher than 16 metres, these waves were coming from anywhere between plus 45 and minus 45 degrees from wind direction and could be 30 plus metres in height.
The shipbuilding industry and ship insurance firms use the Linear Wave Theory mathematics as a working rule, this theory leads the industries into the belief that waves of 15-16 metres are the highest that will be encountered and a bigger wave will only come along about once in ten thousand years. All ships are built with this calculation in mind and in general it is quite accurate except for the amount of rogue waves and their timing of appearance.
To give you more of an appreciation..a normal wave in a gale 5-6metres in height will hit a ship with the force of 6 tons per square metre, a wave of 15 metres will hit with the force of 16 tons psm, a rogue wave of 30metres hits with a force of 100 tons psm. This has brought some consternation to the shipping industry, and the insurance firms who can no longer argue that in some cases the ship or cargo was lost due to crew error or bad maintenance.
There are now a number of theories of how these rogue waves are formed, just Google for "rogue waves" and quite a few sites will come up.
Some known cases of encounters.
One of the most hair-raising rogue wave stories describes what happened to the 81,000-ton, 1,000-foot-long liner the Queen Mary in late 1942 during World War II. It was loaded with 15,000 American soldiers bound for England when it hit a storm 700 miles off Scotland. Without warning, "one freak mountainous wave" hit the ship broadside. Thousands of tons of raging sea pushed the huge ship farther and farther onto her side until her upper decks were awash and the proud ship and her crowded human cargo were within five degrees of capsizing; . For a few seconds experienced seamen aboard thought the Queen Mary was going to roll over. But it righted itself and continued. Rogue waves have sunk other ships, including large ones. Bascom says rogue waves probably explain what happened to many ships that have disappeared without a trace.
During a storm on her New York run across the Atlantic, the 44,000-ton Italian liner MICHELANGELO was hit by a rogue wave; the flare of the ship's stylish b I ow was crumpled as though made of tin instead of special steel; a large hole was torn in the superstructure and bulkheads were crushed; heavy glass windows 80 feet above the waterline were smashed and the sea poured in. Three persons were killed and many injured as the vessel was ravaged by a lone wave of terrorizing power.
The QE2 hit a rogue wave during an Atlantic crossing, bridge crew describe a wall of white water in front of them and she hit it bow on with no damage done.
Oriana2 while answering a distress call off the Western Irish coast went through a rogue wave, no damage reported.
On a very personal note.
Whilst on route from Cape Town to Durban we sailed into rough weather. This route is in the area of the Aguhlas current, and when the storms come up from the South they cause major problems in the sea state.
From the bridge a very large wave was seen heading for the ship, this wave collapsed into the forward trough before it hit the ship bow on. The emergency close watertight doors button was hit immediately and as the ship ploughed into the foaming sea it was like hitting a brick wall, forward motion nearly stopped as the wave passed by, those crewmembers in the 'pig and whistle' were thrown about and the crews liquid refreshment ended up on the deck along with the books from the library, chairs, benches and anything else not bolted down, on the forward mooring deck the outer hinged doors had been stoved in. As the wave passed, the ships bow started to go down and seemed to keep going down as we went into the next trough, the ship started to shudder badly as the props came out of the water, the shuddering stopped and the forward speed picked up very fast and we were still going down (not bad at nearly 900ft in length). The next wave while smaller was now looming over us as we buried the bow into it (still going down), an enormous amount of water came over the focsle swamping the breakwater and slamming into the main super structure which produced 'canning' upto 5 feet off the main deck. The main deck was 50 ft above the waterline and the front of the super structure was nearly 100ft from the bow. As we came up the crest of this second wave the whole ship seemed to go backwards, (yatchsmen out there will know of this feeling but you don't expect it on a 42,000 ton liner).
We arrived in Durban the next day rather dishevelled but no serious injuries to crew or passengers.
In the piccy below is an Illustrious class carrier (most probably Victorious) taking it "green", note the absence of whitecaps on the sea in the background.
regards Collin
Out in the North Sea on a oil platform a fella had mounted a wave height radar to monitor the height of the waves.
On January 1st 1999 during a gale this fella was surprised to see on the tracer a wave height measurement of just under 30 metres. Over the next three months, a further 20 plus waves were recorded around this height from the same oil rig.
When this info began to filter through the scientific and naval community a study was made using a satellite. After 10 passes 28 waves ranging in height from 24 - 30plus metres were discovered.
It soon became apparent that this was a three point problem.
The waves had very deep troughs on either side, they didn't obey the general wave rule of motion, and they travelled faster than the normal wave.
Normal waves generally go in the direction of the wind and don't reach higher than 16 metres, these waves were coming from anywhere between plus 45 and minus 45 degrees from wind direction and could be 30 plus metres in height.
The shipbuilding industry and ship insurance firms use the Linear Wave Theory mathematics as a working rule, this theory leads the industries into the belief that waves of 15-16 metres are the highest that will be encountered and a bigger wave will only come along about once in ten thousand years. All ships are built with this calculation in mind and in general it is quite accurate except for the amount of rogue waves and their timing of appearance.
To give you more of an appreciation..a normal wave in a gale 5-6metres in height will hit a ship with the force of 6 tons per square metre, a wave of 15 metres will hit with the force of 16 tons psm, a rogue wave of 30metres hits with a force of 100 tons psm. This has brought some consternation to the shipping industry, and the insurance firms who can no longer argue that in some cases the ship or cargo was lost due to crew error or bad maintenance.
There are now a number of theories of how these rogue waves are formed, just Google for "rogue waves" and quite a few sites will come up.
Some known cases of encounters.
One of the most hair-raising rogue wave stories describes what happened to the 81,000-ton, 1,000-foot-long liner the Queen Mary in late 1942 during World War II. It was loaded with 15,000 American soldiers bound for England when it hit a storm 700 miles off Scotland. Without warning, "one freak mountainous wave" hit the ship broadside. Thousands of tons of raging sea pushed the huge ship farther and farther onto her side until her upper decks were awash and the proud ship and her crowded human cargo were within five degrees of capsizing; . For a few seconds experienced seamen aboard thought the Queen Mary was going to roll over. But it righted itself and continued. Rogue waves have sunk other ships, including large ones. Bascom says rogue waves probably explain what happened to many ships that have disappeared without a trace.
During a storm on her New York run across the Atlantic, the 44,000-ton Italian liner MICHELANGELO was hit by a rogue wave; the flare of the ship's stylish b I ow was crumpled as though made of tin instead of special steel; a large hole was torn in the superstructure and bulkheads were crushed; heavy glass windows 80 feet above the waterline were smashed and the sea poured in. Three persons were killed and many injured as the vessel was ravaged by a lone wave of terrorizing power.
The QE2 hit a rogue wave during an Atlantic crossing, bridge crew describe a wall of white water in front of them and she hit it bow on with no damage done.
Oriana2 while answering a distress call off the Western Irish coast went through a rogue wave, no damage reported.
On a very personal note.
Whilst on route from Cape Town to Durban we sailed into rough weather. This route is in the area of the Aguhlas current, and when the storms come up from the South they cause major problems in the sea state.
From the bridge a very large wave was seen heading for the ship, this wave collapsed into the forward trough before it hit the ship bow on. The emergency close watertight doors button was hit immediately and as the ship ploughed into the foaming sea it was like hitting a brick wall, forward motion nearly stopped as the wave passed by, those crewmembers in the 'pig and whistle' were thrown about and the crews liquid refreshment ended up on the deck along with the books from the library, chairs, benches and anything else not bolted down, on the forward mooring deck the outer hinged doors had been stoved in. As the wave passed, the ships bow started to go down and seemed to keep going down as we went into the next trough, the ship started to shudder badly as the props came out of the water, the shuddering stopped and the forward speed picked up very fast and we were still going down (not bad at nearly 900ft in length). The next wave while smaller was now looming over us as we buried the bow into it (still going down), an enormous amount of water came over the focsle swamping the breakwater and slamming into the main super structure which produced 'canning' upto 5 feet off the main deck. The main deck was 50 ft above the waterline and the front of the super structure was nearly 100ft from the bow. As we came up the crest of this second wave the whole ship seemed to go backwards, (yatchsmen out there will know of this feeling but you don't expect it on a 42,000 ton liner).
We arrived in Durban the next day rather dishevelled but no serious injuries to crew or passengers.
In the piccy below is an Illustrious class carrier (most probably Victorious) taking it "green", note the absence of whitecaps on the sea in the background.
regards Collin