Monday, 3 March 2014

Ship Of The Week - QUEEN MARY 2




THE NEED FOR A SHIP OF ITS KIND


Cunard's Queen Mary and Queen Elizabeth were the transatlantic liners sailing from Southampton to New York till the later 1940s. Once these ships had served their lifetime, it was time to keep up the transatlantic liner services on. The giant ocean liner Queen Elizabeth 2 did the job. But the Queen eventually had seen out her lifespan and its age would finally come to an end. When Cunard Line was taken over by Carnival Corporation in May 1998, the QE2 underwent an extensive refit operation wherein her outmoded steam turbines were replaced by modern diesel-electric installations. QE2 since then, had been offering a traditional mixture of six day transatlantic crossings. But then a great blow almost crippled the ocean liner industry - The First Commercial Transatlantic Airliner, which cut down the journey time from 5 days to 15 hours!

Miraculously, after the 1997 Titanic movie, the company detected a shift in mood. Cruising and particularly transatlantic crossings had gained supreme attraction. Eventually it was decided that a larger and even better ship could be designed for the purpose. And that gave birth to the design of Queen Mary 2.



WHY AN OCEAN LINER AND NOT A CRUISE SHIP?

To understand this, it is important you get along with the basic differences between a cruise ship and an ocean liner from this pictograph.


The cost differential between building and operating a world class ocean liner and a cruise ship was the major challange that was to be faced. It could only be done if there prevailed a continued demand for transatlantic ferry. The trigger was luckily set off by the motion picture of Titanic, 1997, the effect of which gave the industry a clear idea about the resurfacing demands for atlantic ocean lining experiences. People literally wanted to relive moments of transatlantic voyages. The design and building of the World's Biggest Ocean Liner Queen Mary 2 thus began.

She costs a whooping 800 million dollars and has a capacity of 2620 passengers and 1253 officers and crew.



DECISION OF BASIC SHIP PARTICULARS

Stephen Payne, The Chief Designer of the Queen Mary 2 had to optimize the dimensions of the vessel, taking into cinsideration, three dimensional obstacles which the ship would face in its voyage. 
  • LENGTH: The length of QM2 was constrained by the turning basin at Southampton and the length of the finger piers of New York that jut out into the Hudson River.
  • BEAM: Initially, her beam was decided to be limited to that of a Panamax Vessel. But then came up another challange. The then Chairman of Carnival Corporation wanted over half the passangers on QM2 to have their personal balcony space. Payne experimented with the accomodation of balconies by increasing the height of the accomodation decks. But that would render the ship less stable. The project had almost shut down until Payne came up with the only solution left - Increase in the ship's beam. As a result, the QM2 could not be built to sail through the Panama Canal. The decision was costly as in, she had to sail through the harsh seas of Cape Horn.
  • HEIGHT: The height was limited so that she could transverse below the Verazzano Narrows Bridge at New York's entrance. It was due to this reason, QM2 needed to have a Squat Mast
  • DRAFT: The draft was limited by the depths available at the ports of New York and Southampton.
  • SPEED AND POWER: The speed of the ship had to be decided so that she was able to maintain her tight schedule even in the worst weather conditions. After analyses on data from the Queens sailing before her, Queen Mary 2 was designed for her maximum speed and power requirements accordingly. She is powered by four 16 cylinder Wartsila 16V46CR Diesel-Electric Engines (combined power of 21,500 KW) and two General Electric LM2500+ Gas Turbines which together provide further 50,000 KW power. The gas turbines are actually a derivative of GE aircraft gas turbines. Therefore, being light, they were easily accomodated just below the funnel, without any hazards to the stability of the ship.

This is an infograph on the basic particulars of the QM2:










DESIGN CHARACTERISTICS

1) BOW SHAPE:
One of her most unique features, is her specially designed bow. The entrance angle at the lower waterlines are low enough to eliminate the drag component of the ship due to wave breaking infront of the bow. With higher waterlines, the bow shape is designed to decrease effects of slamming, which is a great threat at North Atlantic rough waters. The overall flared bow shape helps the ship in cutting through the roughest waves, with minimal effect of bow slamming. 

The Flared Bow of Queen Mary 2



2) BREAKWATER:
There are always high risks of green water slamming on the deck, on a route which covers the North Atlantic Ocean. The designers came up with the innovative design of a breakwater on the main deck, which streamlines the incoming gush of green waters away from the ship's body.

Breakwater on the Weather Deck of Queen Mary 2



Note how the breakwater helps in dividing the stream of green waters away from the ship's body



3) SEAKEEPING CHARACTERISTICS:
This is one of the most crucial analyses carried out during the design of a passanger ship. The response of the ship to waves and winds conditions determine the quality of voyage the guests are going to enjoy. QM2's seakeeping and resistance tests were carried out at Maritime Research Institute (MARIN), Netherlands on its 12 meter long model and the comfort and reliability of the ship were found to be outstanding. 

The 12 meter long model of Queen Mary 2 at MARIN, Netherlands

  • Comfort Indicators: The three principal quantitative indicators used to analyze the comfort level in the ship were:
                                              1) Motion Induced Interruptions (MII): The condition in which the ship motions cause a standing person to stumble or look for support.

                                              2) Motion Sickness Incidence (MSI): Sickness caused due to motions of the ship.

                                              3) Maximum Transient Vibration Value (MTVV): Discomfort of the passanger due to vibrations in the ship structure.

  • Pitch Response in Irregular Waves:  It was interestingly found that complete head seas condition didnot represent the severe most conditions of pitching, for a vessel of her size. Rather, quatering wave directions (condition when heading direction makes an angle of approximately 45 degrees and 135 degrees with each other) yield a higher pitch response. The graph below has been taken from the tank test results obtained by Stephen Payne, and it clearly illustrates the described scenario.

Pitch Response of Queen Mary 2 to Irregular Waves

  • Roll Response in Irregular Waves: The effect of the fin stabilizers on the roll response of the ship were studied in order to select the appropriate control gain of the controls of the fins for the prototype. The following graph from the same source shows that the effect of the stabilizers is maximum when the waves are from the stern quarter directions. A short discussion on the roll stabilizer fins will be carried out very shortly.

Roll Response of Queen mary 2 to Irregular Waves


4) ROLL STABILIZER FINS:
Queen Mary 2 has four VM Series folding fin stabilizers. They are one piece passive type design (which means they donot have flaps), and when combinedly used, they reduce the ship's roll by almost 90%

A few details on the fins for your curiosity:
  • Each weighs approximately 70 Tons.
  • Width of a single fin is 2.5 meters.
  • Their extension from the ship's shell is of about 6.25 meters.
  • Each of them provide a lift force of 1070 kN.
  • It takes approximately 30 seconds to extend or house back the fins.
This is an interesting picture of one of the starboard side stabilizer fins, taken during the drydocking of Queen Mary 2. Take note of its enormous size, compared to the two men walking down the dock.




5) DYNAMIC POSITIONING SYSTEM:
She is equipped with Dynamic Positioning System to enhance its maneuverability within confined port waters. Her DP System is controlled by a combination of sensors, GPS networking systems, three bow thrusters, two pod propellers and two azipod propellers. Queen Mary 2's position can be adjusted in one meter increments, if needed.


6) POD PROPULSION TECHNOLOGY:
The Queen Mary 2 is the first ship to be driven by four mermaid pod propellers. The forward two pods are fixed and only help in surging motion. Whereas, the two pods aft of them are azipods. That is, they are 360 degrees rotatable, thus helping the ship to steer manoeuvre efficiently. 
  • Each pod weighs 250 Tons.
  • They are the largest and most powerful pods ever made.
  • Each supply a power of 21.5 MW, thus giving a total propulsive power of 86 MW.
  • The pods are individually hydrodynamically designed to attain the maximum speed of Queen Mary 2
  • The propellers are made of stainless steel and are highly skewed for better efficiency.

Note, in the following picture the size of one such pod undeneath The Queen Mary 2.

The fixed pod on the port side of Queen Mary 2




7) SQUAT FUNNEL DESIGN:

The prime purpose of a funnel in a passanger liner is to guide the exhaust smoke higher away from the topmost deck, thus keeping the stream away from passengers. But QM2 had a problem. Her funnel couldnot be tall enough for that, considering the height constraints which it had to encounter to pass below the Verazzano Narrows Bridge, as visible in the picture below.




You must have been wondering what was the idea behind a squat funnel. The base of the funnel was designed with a curved contour and tested in a wind tunnel testing facility. The purpose was served. The curved surface at the funnel's base, forced the wind stream along its curvature, leading the smoke stream towards the tip of the funnel. A snapshot of the funnel model in the wind tunnel test is shown below. Note the curved contour of the funnel base, which leads the smoke stream towards the tip of the funnel keeping it away from the passangers on deck.








CONSTRUCTION OF QUEEN MARY 2

She was built in the Chantiers de l'Atlantique, France; which previously built the SS Normandie (1935) and SS France (1961), Norweigian Epic (2010), etc. She was built in a period of only one year, owing two the efficiency of the shipbuilding technology used in the shipyard.

Check out the magnificient snapshots taken during the construction process of the ship.




Assembly of the forward section of Queen Mary 2



Massive block of three accomodation decks being assembled to the ship




The funnel of Queen Mary 2 on its way to the assembly unit


The four mermaid pod propellers waiting to be fitted to her hull



Fitting of the bow thruster swivel doors

Queen Mary 2 just before the assembly of her last block at the fore end


QM2's last block being assembled to her steel structure





Queen Mary 2 ready to be painted and floated out



Queen Mary 2 just after float out from the shipyard



TODAY


She was built more than ten years ago. But she still remains the world's largest, most efficient and most comfortable ocean liner in the world! Here is a view of how she looks when she spreads her waves at sea:



LSD




Article By: Soumya Chakraborty



Author's Note: This article has been written on the basis of technical studies made on the design of Queen Mary 2. I hope you now know a lot more about the world's largest ocean liner than you did before. The snapshots of the ship and its model donot belong to LSD, and full credit goes to their respective owners. Thank You for reading. Your doubts and feedbacks are encouraged. In case of any, please comment or write to learnshipdesign@gmail.com

4 comments:

  1. There are two very good documentaries on yhis ship named "inside queen mary 2" (mighty ships - discovery channel) and another one in megastructures - national geographic channel. Both these videos can be seen in you tube.

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