WO2018099906A1

WO2018099906A1 - Container ship with reinforced hull

Info

Publication number: WO2018099906A1
Application number: PCT/EP2017/080647
Authority: WO
Inventors: Kristian AGDRUP; Troels Posborg
Original assignee: Maersk Line A/S
Priority date: 2016-11-29
Filing date: 2017-11-28
Publication date: 2018-06-07
Also published as: DK201670943A1

Abstract

Disclosed is a hull (2) for a container ship (1), said hull comprising a bow (7) and a stern (8) connected by a midship (38), said midship comprising: two hull sides (5), each hull side (5) comprising outer shell plating (22) spaced from inner skin plating (23), a bottom (6) that is at least partially planar and connected to a lower end of each hull side (5) via bilge sections (21), top shell plating (30) forming an upper end of said hull sides (5), said inner skin plating (23) forming a planar surface substantially arranged at a right angle to said bottom (6), characterized in that said top shell plating (30) extends between, and is connected to, said outer shell plating (22) and said inner skin plating (23); said hull sides (5) comprises a lower portion (33) and an upper portion (34), said lower portion (33) extends along the length of the midship (38) and extends upwards from said lower end of the hull side (5), wherein the outer shell plating (22) is equidistantly spaced from the inner skin plating (23) in the lower portion (33); said upper portion (34) extends along a part of the length of the midship (38) and extends downwards from said upper end of the hull side (5), and a first distance (d1) in a beam direction of the ship between said inner skin plating (23) and said outer shell plating (22) in said upper portion is greater than a second distance (d2) between said equidistantly spaced inner skin plating (23) and said outer shell plating (22) in said lower portion.

Description

CONTAINER SHIP WITH REINFORCED HULL TECHNICAL FIELD The disclosure relates to a hull for a container ship and to a container ship, i.e. a marine vessel configured for storage and transport of shipping containers . The disclosure relates in particular to a container ship with a reinforced hull. BACKGROUND

Container ships are marine vessels (cargo ships) that are designed and constructed for storing and transporting shipping containers (intermodal containers) . Typically, container ships carry all of their load in truck-size intermodal containers. Container ships are a common means of commercial intermodal freight transport and now carry most seagoing non-bulk cargo. Container ship capacity is measured in 20-foot equivalent units (TEU) . Typical loads are a mix of 20-foot and 40-foot (2-TEU) ISO-standard containers, with the latter predominant .

Shipping containers are stowed in the cargo holds in the hull, i.e. below the main deck, and above the main deck of a container ship. In the longitudinal direction of the container ship storage space is divided into container bays, in the transverse direction of the hull the storage space is divided in a number of rows, and in the vertical direction the storage space is divided in a number of horizontal container layers called tiers. The shipping containers are stowed as high as possible with some container ships operating with up to ten or eleven tiers above the main deck.

Container ships are provided with a deckhouse housing the navigation bridge and accommodation. The deckhouse is conventionally arranged towards the stern of the ship, immediately above the main engine room (single island design), with most of the cargo holds arranged in front of the deckhouse and the remaining holds aft of the deckhouse.

In order to maintain good forward visibility from the navigational bridge, necessary to comply with maritime regulations, there is a limitation as to how high shipping containers can be stowed in front of the deckhouse/bridge, i.e. how many tiers of shipping containers can be carried by the ship above the main deck on the most forward bays in front of the deckhouse.

The prior art discloses container ships where the deckhouse /bridge has been moved somewhat forward towards the bow of the ship (twin island design) . By moving the deckhouse forward, the capacity of the ship is increased since the shipping containers can be stowed higher in the most forward bays due to a steeper line of sight from the bridge to the water surface ahead of the bow.

US 6,386,131 discloses a hybrid ship hull which includes three parts and whose tem and bow parts are made of composite materials while the mid-section is made of hybrid steel frame. US 4,365,580 discloses a composite hull construction for boats .

Due to cost and environmental considerations, there is a desire to further increase the capacity of such container ships. The capacity of container ships can for example be increased by moving the deckhouse completely forward i.e. ahead of the container bays. Thus, there are no above deck containers ahead of the deckhouse that could obstruct view from the bridge to the water ahead of the containership .

However, the deckhouse provides for a significant part of the torsional strength of the hull when it is placed in the conventional location above the engine room or approximately amidships. Therefore, arranging the deckhouse at the bow has a negative effect on the torsional strength.

SUMMARY

It is an object to provide a hull for a container ship that overcomes or at least reduces the problems above.

The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures .

According to a first aspect, there is provided a hull for a container ship according to claim 1. By providing hull sides having a greater spacing between the opposing plating in the uppermost portion of the hull side, an enlarged lengthwise torsional box is created in the upper area of the hull side, thereby reinforcing the hull and significantly increasing the torsional strength of the hull. The beam of the ship is only increased in the uppermost area of the hull, and thus the effective beam of the ship in relation to hull resistance and passage through narrow passages is not affected. The increase in torsional strength of the hull allows the deckhouse of the ship to be positioned ahead of the container bays, at the bow of the ship, which not only improves the visibility from the bridge, but also increases the number of containers which can be stacked above deck, since they are stacked behind the bridge. Further, the increased width of the upper part of the hull may create additional area for carrying above deck shipping containers.

In a first possible implementation form of the first aspect the outer shell plating is equidistantly spaced from the inner skin plating in the lower portion, at the second distance.

In a second possible implementation form of the first aspect the outer shell plating is spaced from the inner skin plating in the upper portion at a variable first distance, the variable first distance being larger than the second distance.

In a third possible implementation form of the first aspect the lower portion extends to the upper portion. In a fourth possible implementation form of the first aspect the first distance between the inner skin plating and the outer shell plating at a transition between the lower portion and the upper portion is equal to the second distance and wherein the first distance between the inner skin plating and the outer shell plating in the upper portion gradually increases with the distance from the transition at least in a lower part of the upper portion.

In a fifth possible implementation form of the first aspect the first distance between the inner skin plating and the outer shell plating is constant in an upper part of the upper portion.

In a sixth possible implementation form of the first aspect the top shell plating covers the distance between the inner skin plating and the outer shell plating at the upper end of the hull side.

In a seventh possible implementation form of the first aspect the top shell plating is connected to an upper edge of the inner skin plating, and the top shell plating is connected to a side of the outer shell plating, such that the outer shell plating extends upwards past the top shell plating.

In an eight possible implementation form of the first aspect the hull further comprises a cargo hold for stowing shipping containers below deck.

In a ninth possible implementation form of the first aspect the hull further comprises a plurality of transverse bulkheads dividing the cargo hold longitudinally into container bays, each container bay having an opening that provides access from above. In a tenth possible implementation form of the first aspect the hull further comprises a transverse box structure forming the upper part of the transverse bulkheads, the transverse box structures connecting the hull sides.

In an eleventh possible implementation form of the first aspect the hull further comprises a deck surrounding the openings, the deck being adapted for supporting hatch covers for covering the openings /container bays, the hatch covers supporting containers stowed above deck, the deck comprising deck plating that forms an upper side of the transverse box structures . In a twelfth possible implementation form of the first aspect the hull further comprises two outer support structures, each outer support structure extending lengthwise along one of the hull sides and projecting upwardly from the top shell plating, and wherein the outer support structures provide support for at least one outer row of containers stowed above deck.

In a thirteenth possible implementation form of the first aspect the outer shell plating extends upwards such that it forms part of the outer support structure.

In a fourteenth possible implementation form of the first aspect each hull side further comprises at least one lengthwise extending crew passageway arranged on top of the top shell plating. In a fifteenth possible implementation form of the first aspect each hull side further comprises at least one lengthwise extending crew passageway arranged in the hull side between the outer shell plating and the inner skin plating.

In a sixteenth possible implementation form of the first aspect each hull side further comprises at least one lengthwise torsion box, the vertical sides of the lengthwise torsion box being formed by the outer shell plating and the inner skin plating.

In a seventeenth possible implementation form of the first aspect the top side of the lengthwise torsion box forms part of the top shell plating.

In an eighteenth possible implementation form of the first aspect the lengthwise torsion box comprises a crew passageway. In a nineteenth possible implementation form of the first aspect the crew passageway is shaped and sized for allowing an individual to walk through the crew passageway in an upright position. In a twentieth possible implementation form of the first aspect the deck comprises planar plating surrounding the opening and the planar plating extends laterally to the outer shell plating and the planar plating is connected to the outer shell plating and to the inner skin plating. According to a second aspect, there is provided an assembly comprising a hull according to the above, further comprising at least one hatch cover. According to a third aspect, there is provided a container ship comprising a hull or an assembly according to the above.

In a first possible implementation form of the third aspect the container ship further comprises a deckhouse arranged ahead of the cargo holds.

By arranging the deckhouse ahead of the cargo holds, there is no restriction in the number of tiers of containers that can be stacked in the forward container bays and the cargo space under the deckhouse that is "lost" for stowing shipping containers is much smaller when the deckhouse is arranged ahead of the cargo hold due to the V-shaped cross-section of the hull in the forward portion of the hull compared to the U-shaped midship cross-section.

These and other aspects will be apparent from the embodiments described below.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present disclosure, the aspects, embodiments, and implementations will be explained in more detail with reference to the example embodiments shown in the drawings, in which:

Fig. 1 is a side view of a prior art container ship, Fig. 2 is an elevated view of a hull of a prior art container ship,

Fig. 3 is a partially transparent side view of a container ship in accordance with an embodiment,

Fig. 4 is a cross-sectional view of the container ship in Fig. 3,

Fig. 5 is a cross-sectional front view of an upper section of a hull side according to prior art,

Fig. 6 is a cross-sectional front view of an upper section of a hull side in accordance with an embodiment,

Fig. 7 is a top view of a hull according to prior art,

Fig. 8 is a top view of portion a hull of the containership of Fig. 3,

Fig. 9 is a cross-sectional front view of an upper section of a hull side in accordance with a further embodiment,

Fig. 10 is a cross-sectional front view of an upper section of a hull side in accordance with yet another embodiment, and Fig. 11 is a top view of the container ship in Fig. 3. DETAILED DESCRIPTION

Fig. 1 shows a container ship 1, i.e. a ship suitable for stowing and transporting a large number of shipping containers, in side view. Fig. 2 shows a hull 2 of a different container ship 1 in perspective view.

A container ship 1 comprises a hull 2 that extends over the full length of the container ship 1 between the bulbous bow 7 and the stern 8. The hull 2 houses one or more engine rooms, fuel tanks, and other facilities required for the operation of the container ship 1. A major part of the interior of the hull 2, the cargo holds, is used for stowing shipping containers 19, and a small portion of the cargo holds is shown by the cutaway view 11 in Fig. 1. The container ship 1 is provided with one or more large internal combustion engines for propulsion, or driving the propellers ( s ) 9, and there will be one or more auxiliary engines (generator sets) that provide electrical power and heat for various consumers of electrical power and heat aboard the container ship 1. One or more rudders 10 provide for directional control of the container ship 1.

The container ship 1 is further provided with a deckhouse 3 comprising a navigation bridge and crew accommodation, and a casing containing one or more funnels 4. In the embodiment of Fig. 1 the deckhouse 3 is separate from the casing 4, and therefore a design of this type of container ship 1 is called "twin island". Fig. 2 shows an embodiment where the container ship is of the so-called "single island" design, where the deckhouse and the casing are a single unit.

Shipping containers 19, are stowed inside the hull 2 and on the main deck 29 in a plurality of cargo bays 12 distributed over the length of the container ship 1. The stowed containers 19 are arranged in a plurality of rows 15 distributed over the breadth, i.e. the beam b, (Fig. 7 and 8) of the hull 2 / container ship 1, and arranged in a plurality of tiers 14 in the direction of the height of the container ship 1. The cargo bays 12 are typically separated by lashing bridges 13 above deck and are separated by transverse bulkheads 16, 17 in the cargo hold below deck. The lashing bridges 13 may extend from one to four tiers 14 high and serve to secure the containers 19 by lashing.

As shown in Fig. 2, the hull 2 has an elongated shape with a length, beam b, and height. The hull 2 is a complex arrangement of stiffened plates, floors, web frames, webs and girders. Bottom floors, girders, inner and outer bottom stiffened plates form the bottom 6 of the hull 2. The side 5, formed by web frames, stringers, inner skin and outer shell stiffened plates, is connected to the bottom 6 at the raised inner bottom, close to the bilge strake 21.

The deck 29, the plating that forms the top of the hull framework, is supported by transverse box structures 20 that are attached to the tops of the side frames and the transverse box structures 20 run the full breadth of the container ship

1 thereby connecting the hull sides 5. The transverse box structures 20 contribute to the overall strength of the hull

2 and thus not only support the main deck 29, but along with the deck, frames, and transverse bulkheads 16, 17, strengthen and reinforce the hull 2.

Transverse bulkheads 16, 17 divide the cargo hold longitudinally into container bays 12. Typically, the lengthwise distance between the bulkheads 16, 17 corresponds to two 20-foot intermodal containers 19 or to one 40-foot intermodal container 19. The transverse bulkheads 16, 17 extend between the sides 5 of the hull 2 and from the bottom 6 of the hull 2 to the transverse box structures 20. The transverse bulkheads 16, 17 are connected by welds to the sides 5 (web frames) , to the bottom 6 of the hull 2, and to the transverse box structures 20. Each transverse bulkhead

16, 17 is connected to a transverse box structure 20. Thus, a transverse box structure 20 forms a part of each transverse bulkhead 16, 17. The transverse bulkheads 16, 17 can be closed or open. In the Figs, reference numeral 16 is associated with a closed transverse bulkhead and reference numeral 17 is associated with an open transverse bulkhead. Typically, the cargo hold in the hull 2 is longitudinally divided into container bays 12 by alternating open transverse bulkheads 17 and closed transverse bulkheads 16.

Both the closed and open transverse bulkheads 16,17 are provided with a plurality of stringer decks at levels that correspond roughly to tiers 14. The stringer decks serve as platforms for the crew, and together with vertical webs the stringer decks form a frame for the transverse bulkheads 16,

17. The closed transverse bulkheads 16 are open to one side and closed to the other side by steel plating that is welded to the stringer decks and to the vertical webs. The crew can access and service the longitudinal end of containers 19 that face the open side of the closed bulkheads 16 from the stringer decks. The open bulkheads 17 are open to both sides and therefore the crew can access and service the longitudinal end of containers 19 at both sides of the open bulkhead 17.

The transverse box structure 20 at the upper end of the transverse bulkheads 16, 17 is a hollow box constructed from metal plates, such as e.g. mild steel plates normally used in the construction of the hull of a marine vessel, although other materials could be used, such as e.g. high-grade steel or composite materials. The transverse box structure 20 has a substantially rectangular cross-section but does not need to be perfectly rectangular, i.e. the structure should merely be substantially box-shaped and one or more of the sides of the box can have a screened angle relative to a neighboring or opposing side.

In an embodiment, the transverse box structure 20 has four sides, each side formed by plates. The lower horizontal side 28 of the transverse box structure 20 is welded to the upper end of a bulkhead 16, 17. The upper side 25 of the transverse box structure 20 is substantially level with the main deck 29. The inside of the transverse box structure 20 forms a passageway 18 for the crew, and typically there is provided a staircase or ladder that allows access from the upper side 25/main deck 29 into the transverse box structure 20.

The hull 2 can be divided into a number of main structural elements, each element having its own function in strengthening and reinforcing the hull: bottom, sides, deck, hatch coaming, and transverse bulkheads.

A double bottom 6 structure essentially comprises of outer bottom plating, inner bottom plating, and frame work formed by tight or non-tight floors and girders. The mid-section of the ship 1, i.e. the midship 38, is preferably U-shaped with large areas of the hull sides 5 being planar and at a right angle with the planar hull bottom 6, and with the hull 2 gradually being more V-shaped towards the bow 7 and stern 8. Hence, the major part of the bottom 6 is flat and suitable for supporting tiers 14 of shipping containers 19. The sides 5 of the hull 2 comprise of a framework, inner skin plating 23, and outer shell plating 22. In the mid-ship section, the inner skin plating 23 form a planar wall at a right angle with the planar hull bottom 6 thereby delimiting the cargo space. Typically, the outer shell plating 22 is arranged at a constant distance from the inner skin plating 23, so that the outer shell plating 22 in the midship section extends at a right angle to the bottom 6 of the hull 2. The framework comprises a longitudinal bulkhead, side stringers, extending transversely and contributing to the stiffness of the hull, side longitudinals, and side web frames. The sides take up shear forces resulting from the hull girder bending moment and the weight and buoyancy distribution along the length of the ship 1. The hull girder is theoretically a box girder formed by the longitudinal members of the hull 2.

The deck 29 forms an upper surface of the hull 2 and provides support for the hatch covers 24 that carry the above-deck containers 19. The deck 29 is provided with hatch openings 35 that give access to the container bays 12 (Fig. 7) . Hatch covers 24 (Fig. 5) are placed over the hatch openings 35 to provide a weathertight deck and for supporting containers 19 that are placed on the hatch covers 24. In the prior art deck 29 is surrounded by a slightly lower placed deck that is formed at least in part by top shell plating 26 (Fig. 5) .

The support structure for the hatch covers 24, in the art referred to as the hatch coaming, extends vertically from the main deck 29 in the prior art, and is designed to prevent entry of water. It usually refers to a raised section of deck plating around the cargo bay hatch openings 35. Hatch coamings may also provide a frame onto which to fit a hatch cover 24.

The transverse bulkheads 16, 17 divide the cargo hold into a number of compartments, container bays 12, along the length of the ship 1. The closed transverse bulkhead 16, is essentially a grillage and wall structure, the open transverse bulkhead 17 is essentially a grillage structure; both supporting the container 19 stacks and adding stiffness to the hull 2.

The container ship 1 is provided with at least one crew passageway 18. Two such longitudinal passageways 18 are conventionally arranged at main deck level, with one passageway 18 extending along a hull side 5.

In the prior art, side structures 39 are provided to support an outer row 15 of containers 19, see Fig. 5. These side structures could comprise of beams, longitudinally spaced stanchions as well as railing and/or plating for safety of the crew.

Conventionally, the side structure 39 is arranged such that the passageway 18 is a mainly open structure towards the exterior of the ship 1, so that crew members have a substantially unobstructed view to the sea or port, and the side structure 39 is often provided with openings for boarding and disembarking of the crew or a pilot. The passageways 18 are sized and shaped to at least allow a crew member to pass through, walking upright. The torsional stresses on the hull 2 are at their highest around midship, and a deckhouse 3 (and its below-deck structure) placed towards the middle of the ship 1 reinforces the midship and thereby contributes to the torsional strength of the hull 2. A casing 4 and engine room, placed towards the stern 8 of the ship 1, also contribute to the torsional strength of the hull 2. Consequently, a ship 1 as shown in Figs. 3, where the deckhouse 3 is arranged at the bow 7 of the ship, needs additional hull reinforcement.

In an embodiment the hull 2 comprises two hull sides 5 and a, at least partially planar, hull bottom 6 which is connected to the hull sides 5 by bilge sections 21. The middle of the hull 2, i.e. the midship 38, has a cross section which is U- shaped, as shown in Fig. 4, while the ends, i.e. bow 7 and stern 8, have a more V-shaped cross section. Each hull side 5 comprises an outer shell plating 22 and an inner skin plating 23, spaced apart from each other by means of various pieces of framework (stringers) . In the prior art this spacing is constant throughout the hulls sides 5. The hull sides 5 enclose cargo holds used for stowing shipping containers 19 below deck. Alternating closed- and open transverse bulkheads 16, 17 extend across the width of the hull 2, and the closed transverse bulkheads 16 divide the hull longitudinally into several cargo holds and the open transverse bulkheads divide the cargo holds into container bays 12. Each container bay 12 has an opening 35 that provides access from above.

The hull 2 further comprises several transverse box structures 20, extending across the width of the hull 2 and connecting the hull sides 5, and each transverse box structure 20 forms the upper part of a transverse bulkhead 16, 17. The hull 2 is also provided with a deck 29 which surrounds the hatch openings 35. The deck 29 comprises deck plating 30 that forms an upper side of the transverse box structures 20, and the deck 29 is adapted for supporting hatch covers 24 which are used to cover the container bays 12, more particularly the previously mentioned hatch openings 35. The hatch covers 24 also support the containers 19, which are stowed above deck. The hull 2 comprises a bow 7 and a stern 8 connected by a midship part 38. Accordingly, herein the longitudinal extent of the hull 2 between the bow 7 and the stern 8 is defined as the midship. The midship 38 comprises two hull sides 5 and a bottom 6. Each hull side 5 comprises outer shell plating 22 spaced from inner skin plating 23. The bottom 6 is at least partially planar and connected to a lower end of each hull side 5 via bilge sections 21. A top shell plating 30 forms an upper end of the hull sides 5, and top shell plating 30 extends between, and is connected to, the outer shell plating 22 and the inner skin plating 23. The inner skin plating 23 forms a planar surface arranged at a right angle to the bottom 6.

In an embodiment, (Fig. 6) the hull sides 5 comprise a lower portion 33 and an upper portion 34. The lower portion 33 extends along all or a part of the length of the midship 38 and extends upwards from the lower end of the hull side 5. The upper portion 34 extends along a part or all of the length of the midship 38 and extends downwards from the upper end of the hull side 5. The lower portion 33 extends to and meets the upper portion 34. A first distance dl between the inner skin plating 23 and the outer shell plating 22 in the upper portion 34 is greater than a second distance d2 between the inner skin plating 23 and the outer shell plating 22 in the lower portion 33.

The outer shell plating 22 is preferably equidistantly spaced from the inner skin plating 23 in the lower portion 33, at the second distance d2. The outer shell plating 22 is spaced from the inner skin plating 23 in the upper portion 34 at a first distance dl . Distance dl can be variable in e.g. a transitional portion of the upper portion and distance dl is larger than the second distance d2. At a transition between the lower portion 33 and the upper portion 34 the first distance dl between the inner skin plating 23 and the outer shell plating 22 is equal to the second distance d2. In an embodiment the first distance dl between the inner skin plating 23 and the outer shell plating 22 in the upper portion 34 gradually increases with the distance from the transition at least in a lower part of the upper portion 34.

The first distance dl between the inner skin plating 23 and the outer shell plating 22 may be constant in an upper part of the upper portion 34. Alternatively, the first distance dl between the inner skin plating 23 and the outer shell plating

22 in the upper portion 34 may in an embodiment (not shown) decrease with height .

The increased first distance dl between the inner skin plating

23 and the outer shell plating in the upper portion 34 creates an increased lengthwise torsional box, thereby increasing the torsional strength of the hull 2.

As previously mentioned, the midship extends between bow 7 and a stern 8. The upper portion 34 of the outer shell plating 22 protrudes outwardly compared to the lower portion 33 of the outer shell plating 22, by a distance d3 wherein d3=dl- d2 , along the midship, see Figs. 6 and 9-11. I.e., the midship tapers outwards at the transition A between bow and midship, and tapers inwards at the transition B (Fig. 11) between midship and stern, when seen from above. Preferably, the termination of the outwardly protruding plating terminates gradually toward the transition points A and B, respectively. The outwardly protruding portion of the hull side 2 does not need to extend over the full length of the midship, i.e. the outwardly protruding portion extends only over a part of the length of the midship. Preferably, the outwardly protruding portion of the hull side 2 extends at least over 0.4 times the length of the ship as defined in accordance with the International Convention on Load Lines and is preferably centered around the amidship point .

As can be seen in Fig. 11 and the enlarged detail of fig. 11, the increased width (beam) of the uppermost portion of the hull 2 may create increased space for supporting above deck shipping containers 19. In order to ensure adequate view from the navigational bridge downwards along the hull sides, the navigational bridge is correspondingly increased in width. The top shell plating 30 covers the distance dl between the inner skin plating and the outer shell plating at the upper end of the hull side 5. The top shell plating 30 is connected to an upper edge of the inner skin plating 23, and on the opposite end, the top shell plating 30 is connected to a side of the outer shell plating 22, such that the outer shell plating 22 extends upwards past the top shell plating 30.

The hull 2 further comprises a cargo hold for stowing shipping containers 19 below deck. A plurality of transverse bulkheads 16, 17 extend across the width of the hull 2, and divide the cargo hold longitudinally into several container bays 12, and each container bay 12 has a hatch opening 35 that provides access from above.

The hull 2 also comprises a plurality of torsion boxes 20, extending across the width of the hull 2 and connecting the hull sides 5, each transverse box structure 20 forming the upper part of a transverse bulkhead 16, 17 such that the torsion boxes 20 connect the hull sides 5. A deck 29 surrounds the hatch openings 35, and the deck 29 is adapted for supporting hatch covers 24 for covering the hatch openings 35 of the container bays 12. The hatch covers 24 also support containers 19 stowed above deck. The deck 29 comprises deck plating that forms an upper side 25 of the torsion boxes 20.

In the prior art, the deck 29, which is substantially level with the upper side 25 of the transverse box structure 20, extends between the two inner skin platings 23 of the hull 2. A passageway 18 is provided between the inner skin plating 23 and the outer shell plating 22, at a level below that of the deck 29/upper side 25. See Figs. 5 and 7.

The hull 2 further comprises two outer support structures 32, and each outer support structure 32 extends lengthwise along one of the hull sides 5 and projects upwardly from the top shell plating 30. The outer support structures 32 provide support for at least one outer row of containers 19 stowed above deck. Preferably, the outer shell plating 22 extends upwards such that it forms part of the outer support structure 32.

The embodiment of Fig. 6 shows an outer support structure 32, the vertical extent h of which is such that a passageway 18 can be arranged in between the outer support structure 32, the outer row of containers 19, and the top shell plating 30. In this embodiment, the outer support structure 32 provides support for the outer row of containers 19 stowed above deck at a level that substantially corresponds to, i.e. is aligned with, the level where the second, above deck tier 14 begins.

Each hull side 5 comprises at least one lengthwise extending crew passageway 18 arranged on top of the top shell plating 30. Also, each hull side 5 may further comprise at least one lengthwise extending crew passageway 18 arranged in the hull side 5 between the outer shell plating 22 and the inner skin plating 23.

Each hull side 5 also comprises at least one lengthwise torsion box 31 extending along each hull side 5, the vertical sides of the lengthwise torsion box 31 being formed by the outer shell plating 22 and the inner skin plating 23. The top side of the lengthwise torsion box 31 forms part of the top shell plating 30, and the lengthwise torsion box 31 comprises in an embodiment a lengthwise crew passageway 18.

The crew passageway 18 is shaped and sized for allowing an individual to walk through the crew passageway 18 in an upright position. As shown in the embodiments of Figs. 9 and 10, the deck 29 comprises planar plating 30 surrounding the hatch opening 35. The planar plating 30 extends laterally to the outer shell plating 22 and the planar plating 30 is connected to the outer shell plating 22 and to the inner skin plating 23. By "planar" is meant that the plating extends continuously and in alignment, without any vertical height differences. The planar plating 30 is connected to the outer shell plating 22 and to the inner skin plating 23, e.g. by means of welding. The hull 2 is reinforced by extending the planar plating 30 all the way to the outer side plating 22, across the breadth b of the hull 2, and by connecting the planar plating 30 to the outer side plating 22, i.e. the part of the hull side 5 that is constructed like a lengthwise torsion box 31 extends upwards such that it connects with the planar plating 30.

The embodiment of Fig. 6 shows an outer support structure 32. Each outer support structure 32 extends lengthwise along one of the hull sides 5 and projects upwardly from the planar plating 30. The support structure 32 may comprise of e.g. a longitudinally extending beam, a number of vertically extending stanchions or thick plating. Each outer support structure 32 provides support for the outer row of containers 19 stowed above deck at a level that substantially corresponds to, i.e. is aligned with, the level of the upper surface of the hatch cover 24 when the hatch cover 24 is placed over the hatch opening 35 to the container bay 12. The vertical extent h of the outer support structure 32 is preferably less than 1.5 m, even more preferably less than 1 m. The embodiments of Figs. 9 and 10, show planar plating 30 connected to an upper edge of the inner skin plating 23 and to the side of the outer shell plating 22, such that the outer shell plating 22 extends upwards past the planar plating 30. The outer shell plating 22 preferably extends upwards such that it forms part of the outer support structure 32.

Each hull side 5 comprises at least one lengthwise extending crew passageway 18 arranged in the hull side 5 between the outer shell plating 22 and the inner skin plating 23. The crew passageway 18 is shaped and sized for allowing an individual to walk through the passageway 18 in an upright position .

The embodiment of Fig. 3 shows a pilot door 26 arranged in one of the hull sides 5. The pilot door 26 is connected to one of the crew passageways 18, hence giving the pilot easy access to the ship 1. The pilot door 26 is accessed by means of a ladder 27 extending vertically along a hull side 5 of the ship 1. Preferably, the pilot door 26 is located in the hull side 5 at a level below the crew passageway 18. The pilot door 26 is located in the hull side 5 since it would not be safe for a pilot to climb a ladder with a negative inclination in outer shell plating 22 in the area where the spacing between the inner skin plating 23 and the outer shell plating 22 gradually increases. Consequently, the pilot door 26 is arranged below the area where the distance between the inner skin plating 23 and the outer shell plating 22 starts to increase .

Since the passageways 18 are laterally shielded from the exterior of the hull 2 by the outer shell plating 22, a boarding opening 36 is provided in the outer shell plating 22 for providing access for crew and supplies, e.g. via a boarding gangway. This boarding opening 36 is preferably provided just below the passageway 18 i.e. the boarding opening 36 is provided in the shear strake (the upper part of the outer side plating 22) . From a strength point of view, it is preferred to leave shear strake untouched. However, it is often necessary to create openings in the shear strake for boarding gangway and tug lines, etc.

Further, several viewing openings 37 are in an embodiment provided in the outer shell plating 22 primarily to enable handling of tug lines that are connected to bollards on the deck/passage way and secondarily for giving crew members a lateral view to the exterior from the passageways 18. Thus, these openings 37 are located in the shear strake, spaced along the length of the midship 38.

The embodiment of Figs. 3 and 4 show a container ship 1, as disclosed above, with its deckhouse 3 arranged ahead of the cargo holds. The view in Fig. 4 is a cross-section taken in approximately the middle of the midship 38 (view towards the bow) . The deckhouse 3 preferably comprises the bridge and crew accommodation, but could also comprise further areas such as room for auxiliary engines.

The increased spacing dl between the outer shell plating 22 and the inner skin plating 23 causes the overall width (beam) b of the hull to be increased (Fig. 7,8 and 11), thereby potentially allowing 1 or 2 more rows of shipping containers to be stored above deck. The increase d3 in spacing dl is preferably selected to be half the width of a shipping container at each opposing hull side 5 in order to obtain one additional row above deck shipping containers or the increase d3 in spacing dl is selected to be equal to the width of a shipping container 19 at each opposing hull side 5 in order to obtain two additional rows of above deck shipping containers 19.

In an embodiment the deckhouse 3 is conventionally located, i.e. not moved ahead of the cargo holds, or only the bridge is located in the bow. In this embodiment the advantages of the increased torsional strength of the hull 2 can be exploited in other ways. The various aspects and implementations have been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed subject-matter, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

The reference signs used in the claims shall not be construed as limiting the scope.

Claims

1. A hull (2) for a container ship (1), said hull comprises a bow (7) and a stern (8) connected by a midship (38), said midship comprising:

two hull sides (5), each hull side (5) comprising outer shell plating (22) spaced from inner skin plating (23),

a bottom (6) that is at least partially planar and connected to a lower end of each hull side (5) via bilge sections (21) ,

top shell plating (30) forming an upper end of said hull sides (5) ,

said inner skin plating (23) forming a planar surface substantially arranged at a right angle to said bottom (6), characterized in that

said top shell plating (30) extends between, and is connected to, said outer shell plating (22) and said inner skin plating (23);

said hull sides (5) comprises a lower portion (33) and an upper portion (34),

said lower portion (33) extends along the length of the midship (38) and extends upwards from said lower end of the hull side (5), wherein the outer shell plating (22) is equidistantly spaced from the inner skin plating (23) in the lower portion (33) ;

said upper portion (34) extends along a part of the length of the midship (38) and extends downwards from said upper end of the hull side (5), and

a first distance (dl) in a beam direction of the ship between said inner skin plating (23) and said outer shell plating (22) in said upper portion is greater than a second distance (d2) between said equidistant ly spaced inner skin plating (23) and said outer shell plating (22) in said lower portion .

2. A hull (2) according to claim 1, wherein said outer shell plating (22) is spaced from said inner skin plating (23) in said upper portion at a variable first distance (dl) and the variable first distance (dl) varies in the direction of the height of the ship.

3. A hull (2) according to any one of the previous claims, wherein said lower portion (33) extends to said upper portion (34) .

4. A hull (2) according to any one of the previous claims, wherein said first distance (dl) between said inner skin plating (23) and said outer shell plating (22) in said upper portion (34) gradually increases with the distance from said transition at least in a lower part of said upper portion (34) .

5. A hull (2) according to any one of the previous claims, wherein said first distance (dl) between said inner skin plating (23) and said outer shell plating (22) is constant in an upper part of said upper portion (34) .

6. A hull (2) according to any one of the previous claims, wherein said top shell plating (30) covers the distance (dl) between said inner skin plating and said outer shell plating at the upper end of the hull side (5) .

7. A hull (2) according to any one of the previous claims, wherein said upper portion (34) extends over at least 0.4 times the times the length of the hull (2) .

8. A hull (2) according to any one of the previous claims, wherein said upper portion (34) is centered around the amidships position.

9. A hull (2) according to any one of the previous claims, further comprising cargo space for stowing shipping containers (19) below deck.

10. A hull (2) according to claim 9, further comprising a plurality of transverse bulkheads (16, 17) dividing said cargo space longitudinally into cargo holds and container bays (12), each container bay (12) having a hatch opening (35) that provides access from above.

11. A hull (2) according to claim 10, further comprising a transverse box structure (20) forming the upper part of said transverse bulkheads (16, 17), said transverse box structures (20) connecting said hull sides (5) .

12. A container ship (1) comprising a hull (2) according to any one of claims 1 to 12.

13. A container ship (1) according to claim 12, further comprising a deckhouse (3) arranged ahead of the cargo holds.

14. A container ship (1) according to claim 13, comprising a bridge arranged ahead of said cargo holds and an accommodation unit arranged lengthwise at a distance from the bridge in the direction of the stern.

15. A container ship (1) according to claim 13 or 14, comprising a deckhouse arranged lengthwise at a distance from the bridge in the direction of the stern.

16. A container ship (1) according to any one of claims 13 to 15, wherein said upper portion (34) extends over at least 0.4 times the times the length of the ship.