Improving Safety and Propulsion Efficiency of Ships using Retractable Bridge

1. Improving Safety and Propulsion Efficiency of Ships using Retractable Bridge C. Maheshwar Anglo Eastern Maritime Academy Ship Production Symposium, 2012 Providence, Rhode Island, USA 24-25 October 2012

2. This presentation covers the following topics: Introduction – Evolution of Bridge Reduction of Aerodynamic Resistance – Studies so far Relationship between Propulsion Power and Wind Resistance Disadvantages with Raised Superstructure Bridge Watchkeeping Today Redundancy of Tall Bridge Concept Funnel and Deck Cranes Flush Deckers Present Day Ships and Future Retractable Bridged ships Advantages of Retractable Bridge Challenges to be overcome Case Study The Roadmap

3. Evolution of Bridge • Traditionally, sailing ships were commanded from the quarter deck, aft of the mainmast. With the arrival of paddle steamers, engineers required a platform from which they could inspect the paddle wheels and where the captain's view would not be obstructed by the paddle houses. • A raised walkway, literally a bridge, connecting the paddle houses was therefore provided. When the screw propeller superseded the paddle wheel, the bridge was retained.

4. Evolution of Bridge • Traditionally, commands would be passed from the senior officer on the bridge to stations dispersed throughout the ship, where physical control of the ship was exercised, as technology did not exist for the remote control of steering or machinery. • Helm orders would be passed to an enclosed wheel house, where the coxswain or helmsman operated the ship's wheel.

5. Evolution of Bridge • Engine commands would be relayed to the engineer in the engine room by an engine order telegraph, which displayed the captain's orders on a dial. • The engineer would ensure that the correct combination of steam pressure and engine revolutions were applied. • The bridge was often open to the elements, therefore a weatherproof pilot house could be provided, from which a pilot, who was traditionally the ship's navigating officer, could issue commands from shelter.

6. Evolution of Bridge • Iron, and later steel, ships also required a compass platform. • This was usually a tower, where a magnetic compass could be sited far away as possible from the ferrous interference of the hulk of the ship. • Depending upon the design and layout of a ship, all of these terms can be variously interchangeable. Many ships still have a flying bridge, a platform atop the pilot house, open to weather, containing a binnacle and voice tubes to allow the conning officer to direct the ship from a higher position during fair weather conditions.

7. Evolution of Bridge • The concept was that the higher you are situated, the better and farther you could see. • Larger ships, often had a navigation bridge which would be used for the actual conning of the ship. Modern advances in remote control equipment have seen progressive transfer of the actual control of the ship to the bridge. The wheel and engines can be operated directly from the bridge, controlling often-unmanned machinery spaces. • Today, Monkey Island and Crow’s nest have become so archaic that people have forgotten their meaning as they have been deleted from contemporary marine glossaries.

8. Wind Forces • The wind forces are in direct proportion to the ship area exposed above water (projecting areas, also called the wind or sail area), which varies due to superstructure design and ship loading condition. • The aerodynamic resistance of the hull (above water) and superstructure account for approximately 5–8% of the total drag on a ship and for approximately 10% of the total resistance, but by optimising the ship’s aerodynamic profile in the early design phase, it is possible to save 3-4% on the overall fuel consumption.

9. Wind areas of various ships The area of ship above water, part projected on a plane perpendicular to the wind direction, varies greatly, not only due to the different sizes of ships, but even more to the different types of ships, and also depending on whether the ship is loaded or not. Examples: A modem general cargo ship of 30, 000 ton displacement, fully loaded, has a wind area of about 10 m2/lin m of ship, while in ballast condition has an area of about 14 m2/lin m of ship. Large passenger ships will have wind areas of about 26 m2/lin m or more.

10. Reduction of Aerodynamic Forces – Studies so far A. Small ocean going vessels are already being constructed presently for carrying specialized cargoes and applications with removable bridge, the bridge along with the superstructure being small in size is bolted to the main deck and can be removed easily. B. FORCE Technology and Grontmij|Carl Bro have joined forces in a new concept study under the Danish industry project Green Ship of the Future.

11. Reduction of Aerodynamic Forces – Studies so far The aim of the project is to reduce the ship’s aerodynamic resistance and thereby reduce the fuel consumption.  In the project, the performance of handysize bulk carrier Seahorse 35 from Grontmij|Carl Bro is evaluated. With 7,500kW installed power for the main propulsion and specific fuel oil consumption of 165g/kWh, the daily consumption is approx 30 tons heavy fuel oil per day or 9,000 tons at an operation profile of 300 sea days – so even a small percentage-wise decrease in fuel consumption will have a noticeable effect on the ship’s yearly operational costs.

12. Reduction of Aerodynamic Forces – Studies so far It is predicted that optimising the areas directly exposed to the wind can reduce the ship’s aerodynamic resistance by approximately 30-40%. This gives an overall decrease in fuel consumption of 3-4%. C. A Computational Fluid Dynamics (CFD) study was conducted by NTNU, Norway on the effect of aerodynamic resistance of a Container vessel with the foll: particulars;

13. Computational Fluid Dynamics (CFD) study Particulars of the Container vessel Length water line, LWL=221.65m Breadth=32.2m Depth=18.5m Draught=10.78m Block coefficient, CB=0.674 Deadweight, DWT=40900tonnes Cargo capacity: 2800TEU containers; Design speed: 23 knots

14. Computational Fluid Dynamics (CFD) study The container stack was modified and the values air resistance of various situations were tabulated. By applying:- 1.General form of stacks 2.By modifying 3 rear container stacks, for considering accommodating the available spaces due to remove the stacks 3.The 45 degree drag reduction surface with the front edge of the first stack, with modifying rear stacks 4.Sloping upper surface including above modification

15. Summary of CFD Study results

16. Summary of CFD Study results •A drag reduction surface at 45°on front row of containers reduced air flow resistance by 11.5% •By sloping the upper surface of the container stacks and avoiding large gaps between stacks the air resistance could be reduced by about 15% •Streamlining of containers on the after deck behind the deck house reduced the air resistance by about 6.5% By design optimization a reduction of air resistance of about 33% was achieved. The air resistance was 3.2% of the total resistance for this design and speed of ship –leading to fuel and emissions reductions of ~ 1% .

17. Relationship between Propulsion Power and Wind Resistance • Propulsion Power is proportional to Total Resistance • Total Resistance would be equal to Still Water Resistance plus Wind Resistance • Wind Resistance is calculated from the formula Rwind=1/2 X Cx Xƍair X At X Vr² and is directly proportional to (At) Transverse Projected Area above water line and (Vr) Relative Wind Speed.

18. Relationship between Propulsion Power and Wind Resistance Wind Resistance is also a function of density of air which is in turn a function of the temperature. Likewise, Still Water Resistance is a function of Density of sea water which is further a function of sea water temperature

19. Disadvantages with Raised Superstructure Susceptibility to wind forces. More chances of ship toppling over the side when faced with wind speeds beyond a certain limit. Difficulty in shiphandling specially in a strong wind. Need for constant course correction entailing additional fuel consumption. Reduced fuel efficiency and increased fuel consumption particularly relevant during the present days of increased cost of bunker fuel and reducing fossil fuel dependence.

20. Disadvantages with Raised Superstructure Reduction in stability due to increase in height of Centre of Gravity (loss in metacentric height). Increased weight of the vessel, increased quantity of steel used and ultimately increased cost of construction and increased power for propulsion . Increased power consumption due to raised head requirement of utilities like fresh water, sanitary water etc. Increased cost of air conditioning due to exposure of accommodation to ambient conditions of temperature and humidity.

21. The Era of Sealed Bridges The era of sealed bridges has dawned upon us. Today’s bridge watchkeepers do not have to step outside the bridge to have a feel of the sea, to take sights or for any other traditional navigational watchkeeping requirements. Reliance has been placed on technology for all navigational duties. GPS, ARPA, ECDIS have taken over the traditional duties of navigational watchkeepers.

22. The Era of Sealed Bridges All the watchkeeper does today is to look out through the sealed bridge. Often, this vision is impaired by rain, fog, wind etc. etc. rendering him helpless in crucial situation. Accidents have occurred where a bridge watchkeeper could not discern a moving vessel from a stationary object, where technology had failed to warn him. The very purpose of bridge lookout has lost its relevance.

23. Replacing Human Element with Technology We might as well have a high resolution and a powerful camera with telescopic view and night vision mounted outside the bridge facing the front and the sides which would project the image on to a stationary screen. This would help the watchkeeper take the right decision rather than depending solely on the senses of the watchkeeper. In other words, the bridge front can be converted to a giant screen which would give live high definition images of what is happening outside irrespective of the weather condition outside.

24. Redundancy of Tall Bridge Concept The concept of tall bridge has become redundant. The bridge could as well be housed to be a part of the flat box structure, which could be raised to a height during arrival and departure from port. Over a period of time, even this requirement would become redundant as it would be possible to berth and unberth the ship without the requirement of having to see the outside world. The accommodation would also be a part of the box structure with portholes.

25. Integrating Bridge with Engine Room Ultimately, the bridge could be integrated with engine room for sailing watch keeping purposes. As it is now, we are having Bridge Control of Engines. This could lead to reduction in manpower and consequent costs. We could go back to the once tried out and discarded polyvalent dual skilled marine officer training.

26. The Funnel In one of the ships that the author had sailed, during rough weather, due to the prevalent heavy wind, the funnel flew off and fell on the deck. It could have fallen into the sea as well. The winds play havoc with the funnel, especially on older ships as little maintenance is carried out on the supporting structure other than the normal external painting and presence and proximity to corrosive acidic atmosphere from Noxes and Soxes.

27. The Redundant Funnel The funnel would become redundant if the exhaust gases and pipes could be led aft through the engine room above the highest water line and discharged horizontally into the atmosphere. If a reliable non-return mechanism is incorporated to prevent sea water ingress into the exhaust pipes, the pipes could be led below the waterline aiding the propeller thrust as is done in automobiles and smaller crafts..

28. Redundancy of Deck Structures Deck Cranes and Derricks: These days most of the ports are equipped with their own cargo handling facilities. Usage of shipboard cranes has become scarce. Masts can always be made telescopic and can be retracted when not in use.

29. Flush Deckers We are talking about flush deckers which in naval architecture parlance, refer to when the upper deck of a vessel extends unbroken from stem to stern. There is no raised forecastle or lowered quarterdeck. Ships of this type may be referred to as "flush deckers", although this term is often taken as referring to a series of United States Navy destroyers originating from World War I and typified by the Wickes class

30. Ships of the Future - with Retractable Bridges Funnel modified to fit horizontally inside the engine room under the waterline to aid propellor thrust Superstructure retracted into the horizontal box structure

31. Advantages of Retractable Bridge Easier ship handling, especially in strong winds. Additional safety when facing winds with great force. Streamlined structure offers less air resistance resulting in better speed, better fuel economy and efficiency, overall reduced fuel cost of propulsion. Reduced vibration due to encapsulation of bridge and accommodation within the horizontal box structure. Improved stability due to reduction centre of gravity and improved metacentric height. More relevant to Ro-Ro vessels and Car carriers.

32. Advantages of Retractable Bridge Improved propulsion characteristics because of the added thrust and jet affect of the exhaust gases. Reduction in deadweight of the vessel, quantity of steel used and overall cost of construction. Reduced power required for utilities. Reduced power consumption for air conditioning because of reduced losses of cold air due to reduced length of air conditioning ducts. Reduced in air conditioning load as accommodation spaces are not exposed to ambient conditions of temperature and humidity. Better co-ordination between deck and engine departments during sea watches and emergencies.

33. Challenges Unlearning traditional ship design concept of having an elevated navigational bridge with a good all around lookout. Accepting new concept of an integrated bridge and engine room watch keeping. Provision of a suitable device (either mechanical or hydraulic) for raising and lowering a small section of the accommodation area containing bridge to above the deck level during berthing and unberthing activities. Prevention of water ingress into the Exhaust pipes of the Engines – Design and provision of a reliable non return mechanism.

34. Challenges Provision of high tech high definition all weather three dimensional cameras to give a good view of the outside. Projection of the live images on the screens inside the bridge. Since the funnel would have lost its significance, the ship’s flag state, owner’s logo/insignia could be painted and displayed on the shipsides and other places. Provision of watertight integrity of the accommodation to prevent ingress of rain water and sea water spray into accommodation.

35. Limitations Applicable to only those ships which do not carry any deck cargo which protrudes out of the main exposed weather deck, like bulk carriers and tankers. Container ships car carriers and other similar ships would need to make other structural design changes. Since resistance due to wind force is a function of the direction, the advantage of wind force aiding the ship speed when acting from rear will be lost.

36. CASE STUDY – A CHEMICAL TANKER • At fully loaded condition at maximum draft • Calculate the underwater cross sectional area • Calculate exposed Hull area • Calculate superstructure area

37. CASE STUDY – A CHEMICAL TANKER At fully loaded condition at maximum draft; the underwater cross sectional area is (12.2m Draft X 32.2m Breadth) =393 sq. mtrs. The total wind exposed area is equal to the sum of exposed hull area and area of superstructure i.e., (6.6m Freeboard X 32.2m breadth) + (18m Ht X 28m breadth) = (211.4 + 504)=719 sq. mtrs.

38. Superstructure Area vs Total wind exposed area We will be able to substantially reduce the power required for propelling the ship by dispensing with the 504 sq. mtrs of superstructure area exposed to the wind as a against a total wind exposed area of 719 sq. mtrs. About 70% is the component of Superstructure Area of the Total Wind Exposed Area

39. PREPOSTEROUS! ABSURD! RIDICULOUS! UNCONVENTIONAL! IMPRACTICAL! Been hearing these words since centuries, whenever a new idea is born! This is not THE END This is a NEW BEGINING! Dawn of a NEW ERA!

41. Thank you Namaste