Patentamt Europaisches ||| || 1 1| || || || || || || ||| || ||| || (19) J European Patent Office

Office europeen des brevets (11) EP 0 559 806 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publicationation and mention (51) |nt. CI.6: B63B 3/20, B63B 25/08 of the grant of the patent: 06.08.1997 Bulletin 1997/32 (86) International application number: PCT/GB91/02148 (21) Application number: 92902279.6 (87) International publication number: (22) Date of filing: 04.12.1991 WO 92/10396 (25.06.1992 Gazette 1992/14)

(54) WATERCRAFT HULL MODIFICATION VERANDERUNG eines schiffsrumpfes PROCEDE PERMETTANT DE MODIFIER LA COQUE D'UN BATEAU

(84) Designated Contracting States: (74) Representative: Meeks, Frank Burton et al DE ES FR GB IT NL SE BREWER & SON Quality House (30) Priority: 05.12.1990 GB 9026444 Quality Court 03.05.1991 GB 9109719 Chancery Lane London WC2A1HT(GB) (43) Date of publication of application: 15.09.1993 Bulletin 1993/37 (56) References cited: DE-A-3128 822 FR-A- 2 372 072 (73) Proprietor: STUART, William FR-A- 2 449 033 GB-A- 1 082 982 Houston, TX 77082 (US) US-A-3 831 212

(72) Inventor: STUART, William • A GROUP OF AUTHORITIES 'ship design and Houston, TX 77082 (US) construction' 1969 , SOCIETY OF NAVAL ARCHITECTS AND MARINE ENGINEERS , NEW YORK

CO CO o CO <7> ^ Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in ^O a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. Q. 99(1) European Patent Convention).

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Description prevent hydrostatic collapse of these deep water struc- tures when it becomes uneconomic to build the legs to The present invention relates to watercraft hull a size to withstand the hydrostatic pressure encoun- modification and is particularly although not exclusively tered at that depth. concerned with hull modification to oil tanker vessels 5 There is one case common in ship design where a and other ships engaged in the trade of carrying liquids small compartment is free flooded and that is a sea which would, if the hull were broached, present a poten- water chest. A sea water chest is a small compartment tial hazard to the environment and an economic risk of having a volume of between 1 and 10 metres cubed, losing cargo. which is free flooded for pipe connections and which is Most ships currently engaged in the carriage of oil 10 used as a source of salt or fresh water for the conven- have a single hull or single skin usually referred to as a ience of the ship's piping systems as a water inlet. This single bottom. If they run aground or collide with a sub- compartment is always on the shell hull, and can be and merged object or are involved in a collision with another sometimes is located between the outer and inner bot- vessel, they readily lose their cargo on the broaching of tom. the hull, bottom or side, as was the case with the Exxon 15 In French patent application No. 7735538 (publica- Valdez. tion No. 2372072) there is made known a double hulled The provision of double hulls on tankers to avoid or storage tank. The double hull space of the tank extends at least reduce the loss of cargo following damage to across the bottom and up each side of the tank and is the hull, bottom or side has been the subject of discus- split into upper and lower compartments which are seg- sion for many years. 20 regated from each other by partition plates. The lower In general, the provision of a double hull has not compartment is able to free flood to the level of the par- been considered economical although the introduction tition plates through valves which communicate with the of double hulls is most desirable from an antipollution water on which the tank floats. point of view. It is well known to fit fenders to the sides of ships It is known to fit to an existing watercraft by way of a 25 and boats to protect specific areas of the hull from con- retrofit an additional hull internally of the main hull. In a tact damage. Fenders are typically corrugated with sec- known method an inner hull skin is fitted extending tions between 30.48 cm and 35.56 cm (12 and 14 across the bottom of the ship and supported by trans- inches) deep and are fitted to vessels, such as tugs, verse framing built up from the existing main hull bottom supply boats and ferries that are frequently involved in of the ship. 30 berthing and other operations in which contact with It is also known to build vessels with an additional other vessels occurs. Fenders are fitted to the sides of hull or bottom, e.g. by building both hulls from sub- the vessels usually above the water-line of the vessel assemblies in sandwich-like form with inner and outer and are to protect the vessel from damage by contact hull sections in each assembly, and then assembling with docks or with other vessels. Fenders are fitted only these sub-assemblies on a building slip or in a dock. 35 to those selected parts of the vessel that come into con- Another method, more dramatic, is to cut off the tact with docks or other vessels. existing single hull bottom structure and replace it with a According to a first aspect of the present invention newly constructed double bottom structure. This there is provided a watercraft having a main hull, an method has been applied to tankers with major ground- outer hull skin and an outer hull structure which spaces ing damage. 40 the outer hull skin from the main hull and which is A retro fit of hull sides which is relatively common is attached to an external surface of the main hull of the the fitting of sponsons to the sides of a ship, which act watercraft, characterised in that the outer hull structure essentially as buoyancy tanks and which are added to comprises a plurality of structural elements each com- provide the ship with a greater water plane area and prising a base portion having first and second opposite inertia and increase the carrying capacity of the ship. 45 edges and first and second outwardly inclined side walls This is often done when the naval architects have made which respectively extend from the first and second a design error, or when the owner or operator requires a edges of the base portion in directions which are away change in the characteristics of the ship. from the plane of the base portion and on the same side With known double bottomed watercraft, whether of the base portion, the plurality of structural elements the double bottom was a feature of the craft initially or so being arranged into a plurality of sets, the structural ele- added internally as a retrofit, the spaces between the ments of a first such set being attached in predeter- outer and inner hulls are left as void spaces. There is a mined positions to the external surface of the main hull risk that leakage of cargo into these spaces will occur, and presenting support surfaces spaced from the main and so efficient monitoring systems are required for hull and the structural elements of a subsequent set these spaces, as otherwise contamination of any ballast 55 being attached to the support surfaces presented by a stored in the spaces may occur or there may be danger- preceding set and presenting support surfaces spaced ous build up of explosive gases in the spaces. further from the main hull than the support surfaces pre- Free flooding of void spaces in underwater struc- sented by the structural elements of the preceding set tures is known in relation to oil platform jacket legs to with the outer hull skin being attached to the support

2 3 EP 0 559 806 B1 4 surfaces presented furthermost from the main hull of In one specific embodiment of the invention herein- the watercraft. after to be described, the structural elements extend in According to a second aspect of the invention there the longships direction of the watercraft and the struc- is provided a watercraft having a main hull, an outer hull tural elements are elongate elements. skin and an outer hull structure which spaces the outer 5 In preferred embodiments of the invention hereinaf- hull skin from the main hull and which is attached to an ter to be described, the structural elements form sec- external surface of the main hull of the watercraft, char- tions of the outer hull structure arranged in succession acterised in that the main hull comprises first and sec- along the length of the watercraft and the structural ele- ond sections and that the outer hull structure forms the ments of each outer hull structure section are arranged first sections of the outer hull skin, the outer hull struc- 10 in end-to-end relationship with the structural elements ture comprising a plurality of structural elements each of the next adjacent outer hull structure section. comprising a base portion having first and second In an embodiment of the invention hereinafter to be opposite edges and first and second outwardly inclined described the ends of the structural elements of each side walls which respectively extend from the first and outer hull structure section are spaced from the ends of second edges of the base portion in directions which 15 the elements of the next adjacent outer hull structure are away from the plane of the base portion and on the section and an outer hull skin part of one outer hull same side of the base portion, the structural elements structure section and an outer hull skin part of the next when assembled in predetermined positions presenting adjacent outer hull structure section are connected by a the first sections of the outer hull skin and support sur- stress relief joint whereby the outer hull skin parts of the faces spaced from the main hull to which the second 20 two outer hull structure sections form a continuous skin sections of the outer hull structure are attached. at the joint while the outer hull structure remains struc- According to a third aspect of the invention there is turally discontinuous at the junction of the outer hull provided a watercraft having a main hull, an outer hull structure sections. skin and an outer hull structure which spaces the outer In another embodiment of the invention the struc- hull skin from the main hull and which is attached to an 25 tural elements include a stress relief zone in which parts external surface of the main hull of the watercraft, char- of the structural elements are removed to relieve stress acterised in that the outer hull skin consists of a plurality transmission in the zone and the outer skin includes a of sections and that the outer hull structure forms the stress relief joint in the zone. sections of the outer hull skin, the outer hull structure In an embodiment of the invention the outer hull comprising a plurality of structural elements each pre- 30 skin comprises elongate outer skin sections arranged to formed with an outer hull skin section such that when extend substantially transverse to the longships direc- the structural elements are assembled in predetermined tion of the watercraft. positions by attachment to the main hull the outer hull In embodiments of the invention according to its skin sections are assembled into the outer hull skin first and second aspects hereinafter to be described the spaced from the main hull. 35 structural elements form an open honeycomb structure In embodiments of the invention hereinafter to be comprising a first set of structural elements attached to described the outer hull structure and its attachment to the main hull and a second set of structural elements the main hull is such as to provide fluid containment attached to the first set of structural elements. spaces between the outer hull skin and the main hull Preferably, the outer hull skin is spaced from the which can free flood. 40 main hull by a distance of between 0.1 and 0.05 of the In embodiments of the invention hereinafter to be beam of the watercraft. In particular, the outer hull skin described communication is provided for a flow of water is spaced from the main hull by a distance substantially to free flood the fluid containment spaces. 1/15 the beam of the watercraft. In an embodiment of the invention hereinafter to be In an embodiment of the invention hereinafter to be described the flow of water to the spaces is supplied 45 described the fluid containment spaces between the from the body of water within which the craft moves and outer hull skin and the main hull extend above the the communication providing the flow of water to the waterline of the watercraft and supply means are pro- containment spaces comprises openings in the outer vided for supplying an inert gas to the spaces. Alterna- hull skin extending across the bottom part of the craft. tively, the fluid containment spaces between the outer Preferably, the communication providing the flow of so hull skin and the main hull extend above the waterline of water to the water containment spaces comprises open- the watercraft and vacuum applying means are pro- ings in only that part of the outer hull skin which extends vided for applying vacuum pressures to the spaces. across the bottom of the main hull. In an embodiment of the present invention, the fluid In an alternative embodiment of the invention, the containment spaces between the outer hull skin and the communication providing a flow of water to the fluid con- 55 main hull comprise preselected segregated fluid con- tainment spaces comprises controllable supply means. tainment spaces and supply means are provided for The controllable supply means preferably comprises supplying a pressurised inert gas to one or more of the normally open valve means which close or are closable preselected spaces, whereby the level of the water in in conditions which demand closure. the one or more spaces can be brought to a level below

3 5 EP 0 559 806 B1 6 the waterline of the watercraft. invention, the hull sides will increase in width by a simi- In an embodiment of the invention the preselected lar amount. In a cargo ship, these changes will ideally fluid containment spaces extend above the waterline of affect the cargo body and pump rooms only, that is the the watercraft and vacuum applying means are pro- extent of the ship where cargo is carried. vided for applying vacuum pressures to one or more of 5 In embodiments of the invention according to its the preselected spaces, whereby the level of the water first and second aspects hereinafter to be described the in the one or more spaces can be brought to a level structural elements are channel shaped and hold the above the waterline of the watercraft. outer hull skin spaced from the main hull. In preferred Preferably, the preselected spaces include one or embodiments of the invention as hereinafter to be more port and starboard spaces in the region of the bow 10 described the outer hull skin is substantially flat and of the watercraft and/or one or more port and starboard substantially parallel to the main hull. spaces in the region of the stern of the watercraft. In embodiments of the invention hereinafter to be In an embodiment of the invention hereinafter to be described the fluid containment spaces between the described the supply means for supplying the pressu- main hull and the outer hull skin are free-flooded and rised inert gas to predetermined ones of the prese- 15 hence are at ambient hydrostatic pressure. If free- lected spaces and the vacuum applying means for flooded the structure cannot be subject to static water applying vacuum pressures to predetermined ones of pressure and therefore the structural elements can be the preselected spaces are such that the water level in thinner and of less weight than normally required by a the predetermined ones of the preselected spaces can conventional double bottom construction. Free flooding be brought to predetermined levels above or below the 20 the spaces has a cost benefit effect by obviating the waterline of the watercraft thereby (i) to increase the necessity for piping, venting and access systems nor- overall ballast effect by increasing the level of the water mally associated with conventional double bottom con- in the preselected spaces, (ii) increasing the ballast struction. effect at one end of the craft and decreasing it at the The structural elements are preferably attached by other by raising the water level to a level above the 25 welding to the main hull bottom and sides, and the outer waterline of the vessel in preselected spaces at the one hull structure is fitted in the transverse plane in align- end and lowering the level of the water in the spaces to ment with the vessels' existing internal transverse struc- a level below the waterline at the other end of the vessel tural members. to alter the trim of the vessel or (iii) differentially to adjust The outer hull skin can be attached e.g. by welding the water levels of the water in the port and starboard 30 to the support faces of the structural elements and for a preselected spaces to above and below the waterline to ship will be preferably of a thickness determined by the alter or correct a list in the watercraft. classification rules commonly used for the design and The feature of the present invention of applying to construction of ships; this outer hull skin will be substan- the external surface of the main hull an outer hull struc- tial enough to take the wear and tear of normal ship ture to provide a double bottom and/or double hull either 35 operation including bearing loads imposed due to dock- in part or in total, enables the double hull concept now ing of the vessel in a dry or wet dock. to become more affordable and economically viable. In preferred embodiments of the invention hereinaf- The hull modifying method of the invention further- ter to be described a further substantial cost saving is more minimises the disturbance to the vessels' existing realised by divorcing the outer hull structure from any internal structure and does not require the creation of 40 contribution to the watercraft's longitudinal hull strength, tanks and void spaces internal to the vessel, which by rendering the outer hull structure structurally discon- tanks and void spaces would be subject to hydrostatic tinuous in predetermined stress relief zones. Thus the pressure and pressure head due to liquid cargo. outer hull structure components do not become part of A double bottom and hull provided in accordance the highly stressed bottom flange of the existing hull with the invention can be made safer as spaces 45 girder. The main hull and innerbottom of the watercraft between the existing hull and the outer hull skin are can therefore be the sole contributor to the longitudinal flooded, which prevents accidental build up of explosive strength of the watercraft and shall not be relieved of the hydrocarbon gases in the spaces. paramount duty of providing the overall structural longi- The outer hull structure when fitted in accordance tudinal strength of the watercraft. The substantial cost with the present invention is external to the main hull so saving is achieved by obviating the necessity for using causing an increase in physical depth and width of the high tensile strength steels for the outer hull skin which watercraft. The depth will increase most likely by an are normally associated with the highly stressed plates amount equal to the beam divided by 15; e.g., in the of the hull girder. case of 100 ft or 30 metre beam ship, 2.0 metres. Beam However, there can be an advantage in making the divided by 1 5 is the statistically derived ideal depth or 55 outer skin continuous in the case of a vessel with defi- width of a double hull, believed to reduce the accidental cient longitudinal strength, or a vessel with loading spillage of oil from hull damages by between 37.5 and restrictions, in which case a continuous outer hull struc- 92 percent over a single hull tanker. If the hull sides are ture can add to the longitudinal strength of the vessel. fitted with an outer hull structure in accordance with the Where the structure elements form an open honey-

4 7 EP 0 559 806 B1 8 comb support structure as a result of the build-up of changes in physical dimension, beam, draft virtual dis- sets of structural elements high energy absorbing char- placement, wetted surface of the tanker, all of which will acteristics are advantageously achieved, together with result in a speed reduction, but not a reduction expected an ability to deflect under load; these are desirable fea- to outweigh the advantages of employing methods tures of a damage resistant structure. In this regard, the 5 according to the invention. externally applied outer hull structure should perform Where the outer hull skin is a continuous mem- better than a conventional double bottom and certainly brane having apertures on that part of the outer skin better than a single hull vessel. attached to the bottom of the main hull, in the event of It is considered that the double bottom/double hull broach of the main hull, any oil that leaks out of the main of the watercraft according to the invention can be u hull will, because it is less dense than water, flow applied in a building slip or drydock of either floating or through free-flooded water containment spaces graving type dock. The exact dimensions and plate between the outer hull skin and the main hull, and will thickness configurations and scantling of the applied flow up the sides of the main hull until it reaches the outer hull structure can be provided specifically for each level of the oil in the main hull. The oil will not be able to watercraft and sent to a classification authority for 15n spill out from between the outer hull skin and the main approval, in the same manner as traditional structures hull at the sides of the watercraft because there are no are determined. apertures in the outer hull skin at the sides of the water- Convenient lengths of the structural elements, say craft. 40 to 60 feet or 1 2 to 1 8 metres for a tanker, are posi- Where the fluid containment spaces between the tioned in the dock prior to the docking of the tanker, at 2021 outer hull skin and the main hull extend above the locations between the docking blocks. The tanker is waterline of the watercraft an inert gas can with advan- then docked, after the tanker bottom has been tage be applied to the space above the waterline to dis- inspected, shot blasted and cleaned. The structural ele- place water in the space to a level below the waterline of ments are lifted in place for welding to the hull, edge the watercraft. This has the effect of reducing the draft preparations for welding having been effected prior to 2521 and displacement of the watercraft and enabling an positioning. The structural elements are then welded in increase in the cargo carrying capacity of the watercraft. position and built up as far as practical to the prescribed Where stress relief joints are arranged to connect depth of outer hull skin. At this point, the docking blocks the outer hull skin parts together so that the outer hull would require to be repositioned as is normal, to allow skin forms a continuous membrane at the joints, the completion of the work, since they obstruct the fitting of 303< outer hull skin remains structurally discontinuous but the support members in the places where the ships' bot- there are no gaps between the outer hull skin parts. tom rests. An alternative is to redock the tanker to a Several embodiments of the invention according to slightly offset position in the dock. This which would its different aspects will now be described by way of involve flooding the dock, repositioning the tanker, or example with reference to the accompanying drawings moving the tanker by use of dockside winches in the 353t in which:- normal manner and docking the tanker on the newly applied sections, and then completing the unfinished Fig. 1 is a schematic side view of a marine vessel hull in way of the old dock block positions. for carrying very large crude oil cargoes to which an Another option available is to set the structural ele- outer hull structure in accordance with a first ments transverse across the vessel. This way provides 40« embodiment of the present invention is applied the least impact on moving the docking blocks. On completion of the build-up of the structural ele- Fig. 2 is a schematic longitudinal cross-section ments, or the attachment of the honeycomb support taken on the line ll-ll in Fig 3 of the vessel shown in structure obtained from them on the bottom and sides of Fig 1 the tanker, an outer hull skin can be welded in place. 4541 In a tanker, the side part of the outer hull structure Fig. 3 is a schematic section of the vessel shown in after the turn of the bilge can have the structural ele- Fig 1 , taken on the line Ill-Ill in Fig 1 ments in the vertical position thus simplifying the weld- ing, allowing attachment to the hull and to each other by Fig. 4 is a schematic isometric view of a cargo tank down hand welding, which produces a better quality 50st section of the vessel illustrated in Figs 1 to 3, show- weld by virtue of being easier to perform. ing in more detail the outer hull structure applied to Paint and protective conservation measures can be the main hull of the vessel in accordance with the applied in a timely fashion to the applied outer hull struc- first embodiment of the invention ture and to the main hull to cover the original coatings disturbed during the course of the work. 5i Fig. 5 is a schematic isometric scrap view illustrat- Preferably the sections at the bow and stern are ing in more detail the assembly of structural ele- faired into the hull lines by means of tapered sections to ments and hull skin elements forming the outer hull minimise the additional resistance of the hull and loss of structure shown in Fig. 4 speed caused by the outer hull structure and by

5 9 EP 0 559 806 B1 10

Fig. 6 is a schematic end view of an outer hull struc- sel can be adjusted by adjustment of the water level ture of an alternative form of construction of the in selected fluid containment spaces of the outer outer hull structure according to a second embodi- hull structure ment of the invention which can advantageously be used in of that illustrated in 4 and 5 and place Figs 5 Referring first to Fig 1 , the marine vessel shown is which obviates the need for a separate outer hull a very large crude oil carrier (VLCC) and comprises a skin element bow 11, a main cargo carrying body 12 and a pump room body 13. The vessel 10 is formed with a conven- Fig. 7 is yet another alternative form of construction tional main hull to which has been applied in accord- of the outer hull structure according to a third 10 ance with the present invention an outer hull structure embodiment of the invention which can be used in 15. The outer hull structure 15 extends for the full length place of that illustrated in Figs 4 and 5 and which of the cargo body 1 2 which is best seen in Fig 2 and obviates the need for a separate outer hull skin ele- which comprises cargo tank sections 1 6. ment In the schematic cross-section of the vessel shown 15 in Fig 3, it will be seen that the outer hull structure 15 Fig. 8 is a schematic isometric view of a cargo tank extends fully across the bottom and up each side of the section of a large crude oil carrier vessel of the type main hull 14 where it terminates just below the main illustrated in Figs 1 and 2, provided with an outer deck 17. hull structures in forms different from those illus- Referring now to Fig 4, one of the cargo tank sec- trated in Figs 5, 6 and 7 20 tions 16 of the vessel 10 is illustrated to reveal in more detail the formation of the main hull 14 and the con- Fig. 9 is a schematic sectional side view of part of struction of the outer hull structure 15. The main hull 14 the outer hull structure illustrated in Figs 1 to 4 and together with the deck 1 7 houses a main cargo tank 1 8 Figs 5, 6 or 7, showing the manner in which the and port and starboard segregated tanks 19 and 20 outer hull structure is faired into the main hull lines 25 usually employed as ballast tanks in the conventional at the bow and stern of the vessel carrier vessel. The outer hull structure 1 5 is built up from structural elements 21 of channel section, which are Fig. 1 0 is a schematic isometric view of a part of the arranged one upon another to produce a cellular cross- outer hull structure illustrated in Fig 5, showing a section and which extend the length of the tank section stress relief zone in which the outer hull structure is 30 16. The structural elements 21 support an outer hull made structurally discontinuous skin 22 and provide fluid containment spaces 155 between the main hull 14 and the outer hull skin 22. Fig. 11 is a cross-section through the outer hull The structural elements 21 are arranged unifor- structure and through the stress relief zone shown mally down each side of the main hull 1 4 and across the in Fig 10, taken in a plane indicated by the refer- 35 full width of the bottom of the hull 14 with the distance ence numerals XI-XI in Fig 10 between the main hull 14 and the outer hull skin 22 being maintained constant. Fig. 12 is a schematic sectional view corresponding A scrap view of a part of the bottom of the main hull to that shown in Fig 1 1 but showing an alternative 1 4 together with the outer hull structure 1 5 applied to it means of providing a stress relief zone in the outer 40 is shown to an enlarged scale in Fig 5. As will be seen, hull structure. the bottom of the main hull 14 is formed by a main hull skin 141 secured to and strengthened by longitudinally Fig. 13 is a schematic sectional side view of a large extending girders 142 which are arranged with uniform crude oil carrier vessel having an outer hull struc- spacing across the bottom of the main hull 1 4 and up ture of the form illustrated for example in Figs 6 and 45 each side of the hull 14. The structural elements 21 of 7 and in which supply means are provided for sup- the outer hull structure comprise channel shaped inner plying a controlled supply of water for flooding the structural elements 21 A and outer structural elements fluid containment spaces between the outer hull 21 B, each having side walls 23 extending from a bridg- skin and the main hull ing portion 24. The side walls 23 extend as shown along so the external surface of the main hull skin 141 in align- Fig. 14 is a schematic transverse cross-section of ment with the girders 142 on the inside surface of the the vessel having an outer hull structure as illus- main hull skin 141, the side walls being welded to the trated in Figs 2 to 5, showing the containment of oil main hull skin by any conventional welding technique. following rupture of the main hull of the vessel The side walls 23 of the outer structural elements 21 B 55 engage the side edges of the bridging portions 24 of the Fig. 15 is a schematic part sectional side elevation elements 21 A and are welded thereto by any conven- of a large crude oil carrier vessel fitted with an outer tional welding technique. Finally, an outer hull skin ele- hull structure according to the invention, and illus- ment 221 is secured by welding to the bridging portions trating the manner in which the draught of the ves- 24 of the outer structural elements 21 B.

6 11 EP 0 559 806 B1 12

Openings 25 are provided in the bottom part of the hull structure 15A is shown in which the structural ele- outer hull skin element 221 and in the structural ele- ments 21 are welded to the bottom of the hull 14 and to ments 21 A and 21 B to allow free-flooding of the space each other in the same manner as that described for the between the main hull 14 and the outer hull skin ele- arrangement of Fig 5 and an outer hull skin 221 is also ment 221 when the vessel is in the water. 5 applied in the same manner. A further alternative form No openings 25 are however provided in that part of of construction for the outer hull structure 15 is illus- the outer hull skin 22 which extends up each side of the trated to the right side of Fig 8 at 1 5B where three rows vessel so that in the event of rupture of the main hull 14, of spaced structural elements 21 are built up along the any oil that leaks out of the main hull 14 will, because it bottom of the main hull 14. An outer hull skin 221 is is less dense than water, flow through the free-flooded 10 secured in place in the same manner as that for the spaces between the outer hull skin 22 and the main hull arrangement of Fig 5. skin 141 , and will flow up the sides of the main hull skin It will be appreciated that additional rows of struc- 1 41 until it reaches the level of the oil in the main hull 1 4. tural elements 21 can be added to form an outer hull Oil will therefore be retained between the outer hull skin structure of the required depth and that the outer hull 22 and the main hull 14. 15 skin 22 can take the form of a sheet 221 applied to the In an alternative constructional form of the outer structural elements or be formed by outer hull skin ele- hull structure 15 shown schematically in Fig 6, the struc- ments and the bridging portions of the outermost struc- tural elements 21 A take the same form as those shown tural elements 21 or indeed take the form of structural in Fig 5 and are welded to the main hull skin 141 in the units as illustrated in Fig 7. same manner and along lines of the longitudinal extend- 20 As will be seen in Figs 1 and 2, the outer hull struc- ing girders 142. Similarly, the outer structural elements ture 15 includes end portions 151 and 152 at the bow 21 B take the same form as those shown in Fig 5 and and the stern of the vessel 1 0 by which the outer hull again are welded in the same manner along the edges structure 15 is faired into the main hull 14. The form of the bridging portions 24 of the elements 21 A to form which the fairing end portions 151 and 152 take is illus- a cellular constructions in the same manner of that pro- 25 trated schematically in Fig 9 which shows the stern end vided in the arrangement shown in Fig 5. In place of the portion 152. As can be seen from Fig 9, the structural outer hull skin element 221 of the arrangement shown in elements 21 A and 21 B, which are secured to the main Fig 5 individual hull skin plates 22C are welded in place hull skin 141 terminate at the rear of the outer hull struc- as illustrated to form with the bridging portions 24 the ture 15 in a truncated structural element 21 E and a outer hull skin 22. 30 faired structural element 21 F which are secured to the In yet a further alternative form of construction for main hull 14 in the same manner as the structural ele- the outer hull structure 1 5 which is shown in Fig 7, struc- ments 21 A and 21 B and to which are secured outer hull tural units 21 D are preformed to provide inner side walls skin elements 222 and 223, the joins between the ele- 231, a common bridging portion 232 and oppositely ments with each other and with the main hull 14 being directed outer side walls 233 to which is secured an 35 made by welding. outer hull skin element 222. Each unit 21 D is secured to In the embodiments of the invention hereinbefore the main hull skin 141 by welding the inner walls 231 to described with reference to Figs 4 and 5, the outer hull the main hull skin 141 along the lines of the longitudinal skin 22 of the outer hull structure 22 is formed by weld- girders 142. Each structural unit 21 D is then welded in ing together hull skin elements to form a continuous place, with the abutting edges of the outer hull skin ele- 40 membrane throughout the length of each cargo tank 1 6 ments 222 being welded together to produce a continu- of the vessel. It is however considered to be an advan- ous outer hull skin 22. tage in certain circumstances to arrange for the outer Further alternative forms of construction for the hull structure 15 to contribute essentially no strength to outer hull structure 15 are illustrated in Fig 8. While the the longitudinal hull strength of the vessel. To achieve structural elements 21 are of the same form as those 45 this, the outer hull structure 15 needs to be made struc- illustrated in Figs 4 and 5, it will be seen that for that part turally discontinuous along predetermined paths so that of the outer hull structure 15 which extends up each the outer hull structural elements 21 and the outer hull side of the vessel, the structural elements 21 extend skin 22 do not become part of the highly stressed com- vertically upwardly instead of horizontally. As shown in ponents which make up the main hull 14 of the vessel. Fig 8, they are secured to the side of the main hull 14 so As best seen in Fig 4 stress relief zones 21 G are and to each other in the same manner as that described provided in which the structural elements 21 include for the arrangement illustrated in Figs 4 and 5 and are stress relief discontinuities and the outer hull skin 22 is provided with an outer hull skin 221 also in the same made structurally discontinuous by the formation of a manner. stress relief joint. That part of the outer hull structure 15 which 55 Turning now to Figs 1 0 and 1 1 , an isometric scrap extends across the bottom of the main hull 1 4 is formed view is shown of a part of the outer hull structure 15 from structural elements 21 which extend longitudinally which extends horizontally along the bottom part of the as provided for in the arrangement described with refer- main hull 14. As hereinbefore described with reference ence to Figs 4 and 5. To the left side of Fig 8, an outer to Fig 5, upper structural elements 21 A are secured to

7 13 EP 0 559 806 B1 14 the main hull skin 141 which is supported by the longitu- structure 1 5 along that part of it which is secured to the dinally extending girders 142, while the outer structural bottom of the main hull 14. The manifold 25 is of sub- elements 21 B are secured to the inner structural ele- stantial diameter and extends through the outer hull ments 21 A in the manner illustrated in Fig 5. Likewise structure either within the space provided by one line of the outer hull skin element 221 is secured to the bridg- 5 structural elements 21 or by an opening specifically pro- ing portions 24 of the structural elements 21 B. Stress vided for that purpose. The manifold 25 is provided with relief is obtained by the provision of stress relief aper- a large plurality of orifices and the arrangement is such tures 211 and slots 212 in the side walls of the upper that sea water is free to flow via the sea water chests 23 structural elements 21A and apertures 213 and slots and 24 into the manifold 25, out through the orifices 26 214 in the side walls of the structural elements 21 B. In 10 and into the spaces between the main hull 14 and the addition the outer hull skin is formed with a stress relief outer hull skin 22 so that the outer hull structure is joint 223. flooded and the water in it free to rise to the level of the Referring now to Fig 11, it will be seen that the water within which the craft moves. Remotely controlled stress relief zone 21 G is located in the region of the valves 27 and 28 are provided at opposite ends of the highly stressed transversely extending frame member 15 manifold 25 and are controlled by two oily water moni- 143 of the main hull 14 and that the stress relief joint tors 29 and 30 which respond to the presence of oil in 223 of the outer hull skin 221 is formed as an inwardly the water contained within in the spaces between the extending tubular enlargement of the hull skin element main hull 14 and the outer hull skin 22 to close the 221. In this way, the outer hull structure 15 is rendered valves 27 and 28 so that the spaces between the main virtually discontinuous in the zone 21 G so that the main 20 hull 14 and the outer hull skin 22 become completely hull 14 and the components which support it can be shut off. made the sole contributors to the longitudinal strength While, in normal operation, the vessel 10 in Fig 13, of the vessel. operates in a free flood mode in which the spaces The stress relief zones 21 G as shown in Fig 4 may between the main hull 14 and the outer hull skin 22 are be replaced by an arrangement as illustrated in Fig 1 2 in 25 free to flood to the waterline of the vessel, any rupture in which the structural elements 21 A and 21 B terminate in the main hull resulting in the discharge of oil into the the stress relief zone 21 G so as to provide a gap 34 outer hull structure 1 5 would be sensed by monitors 29 between their adjacent ends and the outer hull structure and 30 and contained by closure of the valves 27 and 22 is completed by an outer hull skin 221 which includes 28. the stress relief joint 223. 30 Turning now to Fig 1 4, a schematic cross-section of In the specific embodiment of the invention herein- the vessel 10 is shown in which the presence of oil is before described with reference to Figs 4 and 5, the illustrated by fine dot shading. Where a break appears outer hull structure 15 is arranged to be free flooded by in the main hull 14, for example at location 31 in Fig 14 the provision of openings 25 in the outer hull skin 221 oil discharged from the opening 31 will travel along the and in the side walls 23 and bridging portions 24 of the 35 bottom of the main hull 1 4 and then up the sides of the structural elements 21 A and 21 B. While the provision of main hull 14 partially to fill the space between the main openings 25 in the outer hull skin 221 serves to provide hull 14 and the outer hull skin 22 as shown at 32 and 33 a ready means for free flooding the spaces provided in Fig 13, displacing the water flooding the space between the main hull 1 4 and the outer hull 22, for some between the two hull structures. The rupture 31 may applications this may be considered to be undesirable 40 result from a failure of the main hull 1 4 and the outer hull and in accordance with an alternative embodiment of structure will then remain intact. The monitors 29 and the invention now to be described with reference to Fig 30 then sense the presence of oil and close off the 12 the outer hull skin 22 is provided without openings valves 27 and 28 providing an effective containment of and alternative supply means are provided for supplying the oil leaking from the opening 31 . water for free flooding the spaces between the outer hull 45 Where the break in the main hull 14 is caused as a skin 22 and the main hull skin 14. result of a collision at sea and a break also appears in Referring now to Fig 13, the vessel 10 shown is of the outer hull skin 22, oil from the opening 31 will still fol- the same form as the vessel 10 described with refer- low the path shown in Fig 14 the outer hull structure 15 ence to Figs 1 and 2 and is provided with an outer hull will effectively contain the leaking oil for some time. structure 1 5 in any of the forms hereinbefore described so In the embodiment of the invention illustrated in with reference to Figs 1 to 1 1 except insofar that the Figs 4 and 5, where openings 25 are provided in the outer hull skin 22 is without the openings and forms a outer hull skin 221 a break in the main hull 14 as repre- continuous membrane. Supply means are nevertheless sented by the opening 31 in Fig 14 will likewise give rise provided for free flooding the spaces between the main to containment of the oil within the outer hull structure hull 1 4 and the outer hull skin 22 and comprises the pro- 55 15 at least until the oil has completely displaced the vision of a bow sea water chest 23 and a stern sea water within the space between the main hull 1 4 and the water chest 24 both of which are open to the sea and to outer hull skin 22. which are connected the opposite open ends of a man- In the embodiments of the invention hereinbefore ifold 25 which extends for the full length of the outer hull described with reference to the drawings, it has been

8 15 EP 0 559 806 B1 16 arranged for the fluid containment spaces between the lower the stern within the water and achieve the main hull 14 and the outer hull skin 22 to become required full immersion of the propeller within the water. flooded to the waterline of the vessel in order to equal- It will furthermore be appreciated that in the event ise the hydrostatic pressures on the outer hull structure that the vessel for one reason or another has taken up a 1 5. It may nevertheless be advantageous to arrange for 5 list to port or starboard within the water the spaces 39, flooding of the outer hull structure 15 to levels (i) below 40 and on one side of the vessel can be subjected to the draft waterline to increase buoyancy of the vessel, pressurised inert gas to lower the water level in the (ii) above the waterline to reduce the buoyancy or (iii) spaces and increase the buoyancy on that side of the differentially at different parts of the vessel to alter the vessel while the corresponding spaces on the other side trim of the vessel. To achieve these ends, the outer hull 10 of the vessel can be subjected to vacuum pressures to skin 22 is formed without openings at least along that increase the ballast effect on that side of the vessel. part of it which extends along the two sides of the vessel A double bottom construction offers many advan- and means are provided for supplying an inert gas to tages over a single bottom but primarily it results in a the fluid containment spaces above the waterline of the structure that can withstand a considerable amount of vessel. The inert gas may be supplied to the outer hull 15 bottom damage caused by grounding without flooding structure 15 as shown in Fig 14 via supply pipe 35 and of the cargo tanks or loss of cargo to the sea. Ships fit- valve 36 which is connected to a pump for supplying ted with double bottoms will remain afloat on the inner pressurised inert gas to lower the level of the water in hull (also known as the tank top) when the bottom has the spaces to a level below that of the waterline of the been severely damaged. vessel or the spaces may be subjected to vacuum pres- 20 The invention is not limited to the prevention of sure by connection via branch pipe 37 and valve 38 to marine pollution, but is applicable to any type of ship or one or more vacuum pumps for withdrawing gas from vessel which would benefit from the installation of an the spaces so as to raise the level of the water within the outer hull structure according to the invention. spaces to a level above that of the waterline. The watercraft to which this invention especially To achieve an adjustment in the trim of the vessel, 25 applies are those that carry oil or bulk materials, or ves- segregated and possibly dedicated fluid containment sels which carry liquids which are hazardous to the spaces will need to be provided within the outer hull environment if spilled on the seas or navigable water- structure 15 as for example illustrated in Fig 15 where ways of the world. forward port and starboard segregated fluid contain- Other advantages to be gained from the watercraft ment spaces 39 and 40 are provided on the sides of the 30 according to the invention are as follows:- vessel 1 0 toward the bow and one or more port or star- board rear fluid containment spaces 41 are provided in 1. By virtue of the additional depth of the double the region of the stern of the vessel 10. Each of these hull, the minimum draft requirements can be met spaces may be connected via separate supply lines to without utilizing salt water ballast. This enables oil pumping installations for either supplying inert gas 35 tanks which have been previously converted for bal- under pressure to the spaces or subjecting the spaces last to once again be utilized for the carriage of oil. to vacuum pressures. In conditions where increased buoyancy is 2. The lightweight outer hull structure aids in ensur- required, all the segregated port and starboard fluid ing the main hull oil barrier is not penetrated on containment spaces 39, 40 and 41 on both sides of the 40 grounding by virtue of the relative thickness, i.e. the vessel can be supplied with inert gas under pressure to outer hull structure collapses or shears rather than lower the level of water in the spaces and effectively to allowing piercing of the hull. increase the buoyancy of the vessel. Alternatively, when additional ballast for the vessel is required all the port 3. The capability to utilize the spaces between the and starboard fluid containment spaces 39, 40 and 41 45 hulls at the forward and aft end to trim the vessel to can be subjected to vacuum pressures to raise the level ensure propeller immersion. The spaces between of the water within the spaces. the hulls can be selectively pressurized to deballast Where the trim of the vessel needs to be adjusted or subjected to vacuum pressures to induce a trim for example when the vessel is transitting without cargo to ensure propeller immersion. This feature is and with ballast only and when the draft is not quite suf- so important as it is necessary under international ficient to achieve full propeller immersion to the required rules to obtain propeller immersion and minimum depth, the trim of the vessel can be adjusted by subject- drafts for safe navigation ing the two spaces 41 on the port and starboard sides of the vessel to vacuum pressure to increase the ballast Claims effect at the stern and to subject the spaces 39 and 40 55 to increased pressure to lower the water level within the 1. A watercraft (10) having a main hull (14), an outer spaces to a level below the waterline thereby to hull skin (22) and an outer hull structure (15) which increase buoyancy in the region of the bow of the ves- spaces the outer hull skin from the main hull and sel. The combined effect is then to raise the bow and which is attached to an external surface of the main

9 17 EP 0 559 806 B1 18

hull of the watercraft, characterised in that the outer 4. A watercraft according to any of claims 1 , 2 or 3, hull structure comprises a plurality of structural ele- characterised in that the outer hull structure and its ments (21) each comprising a base portion (24) attachment to the main hull is such as to provide having first and second opposite edges and first fluid containment spaces (155) between the main and second outwardly inclined side walls (23) which 5 hull and the outer hull skin which can free flood. respectively extend from the first and second edges of the base portion in directions which are away 5. A watercraft according to claim 4, characterised in from the plane of the base portion and on the same that communication (23, 24, 25, 26, 27, 28; 25) is side of the base portion, the plurality of structural provided for a flow of water to free flood the fluid elements being arranged into a plurality of sets, the 10 containment spaces. structural elements of a first such set (21 A) being attached in predetermined positions to the external 6. A watercraft according to claim 5, characterised in surface of the main hull and presenting support sur- that the flow of water to free flood the fluid contain- faces spaced from the main hull and the structural ment spaces is supplied from the body of water elements of a subsequent set (21 B) being attached 15 within which the watercraft moves. to the support surfaces presented by a preceding set (21 A) and presenting support surfaces spaced 7. A watercraft according to claim 5 or 6, character- further from the main hull than the support surfaces ised in that the communication providing a flow of presented by the structural elements of the preced- water to free flood the fluid containment spaces ing set with the outer hull skin being attached to the 20 comprises openings (23, 24; 25) in the outer hull support surfaces presented furthermost from the skin extending across the bottom part of the water- main hull of the watercraft. craft.

2. A watercraft (10) having a main hull (14), an outer 8. A watercraft according to claim 5 or 6, character- hull skin (22) and an outer hull structure (15) which 25 ised in that the communication providing a flow of spaces the outer hull skin from the main hull and water to free flood the fluid containment spaces which is attached to an external surface of the main comprises controllable supply means (23, 24, 25, hull of the watercraft, characterised in that the main 26, 27, 28). hull comprises first and second sections (24, 22C) and that the outer hull structure forms the first sec- 30 9. A watercraft according to claim 8, characterised in tions of the outer hull skin, the outer hull structure that the controllable supply means comprises nor- comprising a plurality of structural elements (21) mally open valve means (27, 28) which close or are each comprising a base portion (24) having first closable in conditions which demand closure. and second opposite edges and first and second outwardly inclined side walls (23) which respec- 35 1 0. A watercraft according to any of claims 5 to 7, char- tively extend from the first and second edges of the acterised in that the communication providing the base portion in directions which are away from the flow of water to free flood the fluid containment plane of the base portion and on the same side of spaces comprises openings (25) in only that part of the base portion, the structural elements when the outer hull skin which extends across the bottom assembled in predetermined positions presenting 40 of the main hull. the first sections of the outer hull skin and support surfaces spaced from the main hull to which the 11. A watercraft according to any of the preceding second sections of the outer hull structure are claims, characterised in that the structural elements attached. are elongate elements. 45 3. A watercraft (10) having a main hull (14), an outer 1 2. A watercraft according to claim 1 1 , characterised in hull skin (22) and an outer hull structure (15) which that the structural elements extend in the longships spaces the outer hull skin from the main hull and direction of the watercraft. which is attached to an external surface of the main hull of the watercraft, characterised in that the outer so 13. A watercraft according to claim 1 1 or 12, character- hull skin consists of a plurality of sections (222) and ised in that the structural elements form sections of that the outer hull structure forms the sections of the outer hull structure arranged in succession the outer hull skin, the outer hull structure compris- along the length of the watercraft. ing a plurality of structural elements (21 D) each preformed with an outer hull skin section (222) such 55 1 4. A watercraft according to claim 1 3, characterised in that when the structural elements are assembled in that the structural elements of each outer hull struc- predetermined positions by attachment to the main ture section are arranged in end-to-end relationship hull the outer hull skin sections are assembled into with the structural elements of the next adjacent the outer hull skin spaced from the main hull. outer hull structure section.

10 19 EPEP0 0 559 80636 B1 20

1 5. A watercraft according to claim 1 3 or 1 4, character- 24. A watercraft according to claim 4, characterised in ised in that the ends of the structural elements of that the fluid containment spaces between the outer each outer hull structure section are spaced from hull skin and the main hull extend above the water- the ends of the elements of the next adjacent outer line of the watercraft and vacuum applying means hull structure section. 5 (37, 38) are provided for applying vacuum pres- sures to the spaces. 16. A watercraft according to claim 15, characterised in that an outer hull skin part of one outer hull struc- 25. A watercraft according to claim 4, characterised in ture section and an outer hull skin part of the next that the fluid containment spaces between the outer adjacent outer hull structure section are connected 10 hull skin and the main hull comprise preselected to one another by a stress relief joint (223) whereby segregated fluid containment spaces (39, 40, 41) , the outer hull skin parts of the two outer hull struc- wherein supply means (35, 36) are provided for ture sections form a continuous skin at the joint supplying a pressurised inert gas to at least one of while the outer hull structure remains structurally the preselected spaces, whereby the level of the discontinuous at the junction of the outer hull struc- 15 water in the at least one space can be brought to a ture sections. level below the waterline of the watercraft.

17. A watercraft according to any of claims 1 to 15, 26. A watercraft according to claim 25, characterised in characterised in that the structural elements include that the preselected fluid containment spaces a stress relief zone (21 G) in which parts of the 20 extend above the waterline of the watercraft and structural elements are removed to relieve stress wherein vacuum applying means (37, 38) are pro- transmission in the zone and the outer hull skin vided for applying vacuum pressures to at least one includes a stress relief joint (223) in the zone. of the preselected spaces, whereby the level of the water in the at least one space can be brought to a 18. A watercraft according to any of claims 1 to 11, 25 level above the waterline of the watercraft. characterised in that the outer hull skin comprises elongate outer skin sections arranged to extend 27. A watercraft according to claim 26, characterised in substantially transverse to the longships direction that the preselected spaces include at least one of the watercraft. port and starboard space in at least one of the bow 30 or stern regions of the watercraft. 19. A watercraft according to claim 1 or 2 or any of claims 4 to 18 as appendent on claim 1 or 2, char- 28. A watercraft according to claim 27, characterised in acterised in that the structural elements comprise that pressurised inert gas supply means for supply- channel shaped elements. ing an inert gas to predetermined ones of the 35 preselected spaces and vacuum applying means 20. A watercraft according to claim 19, characterised in for applying vacuum pressures to predetermined that the structural elements form an open honey- ones of the preselected spaces are such that the comb structure comprising a first set of structural water level in the predetermined ones of the prese- elements (21 A) attached to the main hull and a sec- lected spaces can be brought to predetermined lev- ond set of structural elements (21 B) attached to the 40 els above or below the waterline of the watercraft first set of structural elements. thereby (i) to increase the overall ballast effect by increasing the level of the water in the preselected 21. A watercraft according to any of the preceding spaces, (ii) increasing the ballast effect at one end claims, characterised in that the outer hull skin is of the craft and decreasing it at the other by raising spaced from the main hull by a distance of between 45 the water level to a level above the waterline of the 0.1 and 0.05 of the beam of the watercraft. vessel in preselected spaces at the one end and lowering the level of the water in the spaces to a 22. A watercraft according to any of claims 1 to 20, level below the waterline at the other end of the ves- characterised in that the outer hull skin is spaced sel to alter the trim of the vessel or (iii) differentially from the main hull by a distance substantially 1/15 so to adjust the water levels of the water in the port the beam of the watercraft. and starboard preselected spaces to above and below the waterline to alter or correct a list in the 23. A watercraft according to claim 4, characterised in watercraft. that the fluid containment spaces between the outer hull skin and the main hull extend above the water- ss Patentanspruche line of the watercraft and wherein supply means (35, 36) are provided for supplying an inert gas to 1. Wasserfahrzeug (10) mit einem Hauptrumpf (14), the spaces. einer auBeren Rumpfhaut (22) und einer auBeren Rumpfstruktur (15), die die auBere Rumpfhaut von

11 21 EP 0 559 806 B1 22

dem Hauptrumpf beabstandet, und die an einer dem Hauptrumpf beabstandet, und die an einer auBeren Oberflache des Hauptrumpfs des Wasser- auBeren Oberflache des Hauptrumpfs des Wasser- fahrzeugs befestigt ist, dadurch gekennzeichnet, fahrzeugs befestigt ist, dadurch gekennzeichnet, daB die auBere Rumpfstruktur eine Vielzahl von daB die auBere Rumpfhaut aus einer Vielzahl von strukturellen Elementen (21) umfasst, die jeweils 5 Abschnitten (222) besteht, und daB die auBere ein Bodenteil (24) mit ersten und zweiten gegen- Rumpfstruktur die Abschnitte der auBeren Rumpf- iiberliegenden Kanten und ersten und zweiten nach haut bildet, wobei die auBere Rumpfstruktur eine auBen geneigten Seitenwanden (23) umfasst, die Vielzahl von strukturellen Elementen (21 D) sich jeweils von den ersten und zweiten Kanten des umfasst, die jeweils so mit einem auBeren Rumpf- Bodenteil in Richtungen erstrecken, die von der jo hautabschnitt (222) vorgebildet sind, daB, wenn die Ebene des Bodenteils entfernt sind und auf dersel- strukturellen Elemente durch Befestigung an den ben Seite des Bodenteils liegen, wobei die Vielzahl Hauptrumpf in vorbestimmten Stellungen zusam- von strukturellen Elementen in eine Vielzahl von mengebaut sind, die auBeren Rumpfhautabschnitte Satzen angeordnet sind, wobei die strukturellen in der auBeren Rumpfhaut zusammengebaut sind, Elemente eines ersten solchen Satzes (21 A) in vor- 75 die von dem Hauptrumpf beabstandet ist. bestimmten Stellungen an der auBeren Oberflache des Hauptrumpfs befestigt sind, und Stiitzoberfla- 4. Wasserfahrzeug nach einem der Anspriiche 1, 2 chen darstellen, die von dem Hauptrumpf beab- Oder 3, dadurch gekennzeichnet, daB die auBere standet sind, und die strukturellen Elemente eines Rumpfstruktur und ihre Befestigung an den Haupt- nachfolgenden Satzes (21 B) an den Sttzoberfla- 20 rumpf so ist, urn Fliissigkeitsenthaltungsraume chen befestigt sind, die von einem vorangehenden (155) zwischen dem Hauptrumpf und der auBeren Satz (21 A) dargestellt werden, und Stiitzoberfla- Rumpfhaut zu liefern, die frei stromen konnen. chen darstellen, die weiter von dem Hauptrumpf beabstandet sind, als die Stiitzoberflachen, die von 5. Wasserfahrzeug nach Anspruch 4, dadurch den strukturellen Elementen des vorangehenden 2s gekennzeichnet, daB Verbindung (23, 24, 25, 26, Satzes dargestellt sind, wobei die auBere Rumpf- 27, 28; 25) fur eine Stromung von Wasser vorgese- haut an den Stiitzoberflachen befestigt ist, die am hen ist, urn die Fliissigkeitsenthaltungsraume frei weitesten von dem Hauptrumpf des Wasserfahr- stromen zu lassen. zeugs dargestellt sind. 30 6. Wasserfahrzeug nach Anspruch 5, dadurch 2. Wasserfahrzeug (10) mit einem Hauptrumpf (14), gekennzeichnet, daB die Stromung von Wasser, urn einer auBeren Rumpfhaut (22) und einer auBeren die Fliissigkeitenthaltungsraume frei stromen zu Rumpfstruktur (15), die die auBere Rumpfhaut von lassen, von dem Wasserkorper geliefert wird, in dem Hauptrumpf beabstandet, und die an einer dem sich das Wasserfahrzeug bewegt. auBeren Oberflache des Hauptrumpfs des Wasser- 35 fahrzeugs befestigt ist, dadurch gekennzeichnet, 7. Wasserfahrzeug nach Anspruch 5 Oder 6, dadurch daB der Hauptrumpf erste und zweite Abschnitte gekennzeichnet, daB die Verbindung, die eine Stro- (24, 22C) umfasst, und daB die auBere Rumpf- mung von Wasser liefert, urn die Fliissigkeitenthal- struktur die ersten Abschnitte der auBeren Rumpf- tungsraume frei stromen zu lassen, Offnungen (23, haut bildet, wobei die auBere Rumpfstruktur eine 40 24; 25) in der auBeren Rumpfhaut umfasst, die sich Vielzahl von strukturellen Elementen (21) umfasst, iiber das untere Teil des Wasserfahrzeugs erstrek- die jeweils ein Bodenteil (24) mit ersten und zwei- ken. ten gegeniiberliegenden Kanten und ersten und zweiten nach auBen geneigten Seitenwanden (23) 8. Wasserfahrzeug nach Anspruch 5 Oder 6, dadurch umfasst, die sich jeweils von den ersten und zwei- 45 gekennzeichnet, daB die Verbindung, die eine Stro- ten Kanten des Bodenteils in Richtungen erstrek- mung von Wasser liefert, urn die Fliissigkeitsenthal- ken, die von der Ebene des Bodenteils entfernt sind tungsraume frei stromen zu lassen, ein steuerbares und auf derselben Seite des Bodenteils liegen, Lieferungsmittel (23, 24, 25, 26, 27, 28) umfasst. wobei die strukturellen Elemente, wenn sie in vor- bestimmten Stellungen zusammengebaut sind, die so 9. Wasserfahrzeug nach Anspruch 8, dadurch ersten Abschnitte der auBeren Rumpfhaut und gekennzeichnet, daB das steuerbare Lieferungs- Stiitzoberflachen darstellen, die von dem Haupt- mittel normalerweise offene Ventilmittel (27, 28) rumpf beabstandet sind, an die die zweiten umfasst, die sich schlieBen, oder bei Zustanden, Abschnitte der auBeren Rumpfstruktur befestigt die SchlieBung erfordern, geschlossen werden sind. 55 konnen.

3. Wasserfahrzeug (10) mit einem Hauptrumpf (14), 10. Wasserfahrzeug nach einem der Anspriiche 5 bis einer auBeren Rumpfhaut (22) und einer auBeren 7, dadurch gekennzeichnet, daB die Verbindung, Rumpfstruktur (15), die die auBere Rumpfhaut von die die Stromung von Wasser liefert, urn die Fliis-

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sigkeitsenthaltungsraume frei stromen zu lassen, umfasst, die angeordnet sind, urn sich im wesentli- Offnungen (25) in nur dem Teil der auBeren Rumpf- chen quer zur Langsrichtung des Wasserfahrzeugs haut umfasst, das sich uber den Boden des Haupt- zu erstrecken. rumpfs erstreckt. 5 19. Wasserfahrzeug nach Anspruch 1 oder 2, oder 1 1 . Wasserfahrzeug nach einem der vorhergehenden einem der Anspriiche 4 bis 18, wenn sie an Anspriiche, dadurch gekennzeichnet, daB die Anspruch 1 oder 2 angehangt sind, dadurch strukturellen Elemente langgestreckte Elemente gekennzeichnet, daB die strukturellen Elemente sind. kanalformige Elemente umfassen. 10 12. Wasserfahrzeug nach Anspruch 11, dadurch 20. Wasserfahrzeug nach Anspruch 19, dadurch gekennzeichnet, daB die strukturellen Elemente gekennzeichnet, daB die strukturellen Elemente ein sich in der Langrichtung des Wasserfahrzeugs offene Wabenstruktur bilden, die einen ersten Satz erstrecken. von strukturellen Elementen (21 A) umfassen, die 15 an dem Hauptrumpf befestigt sind, und einen zwei- 13. Wasserfahrzeug nach Anspruch 11 oder 12, ten Satz von strukturellen Elementen (21 B), die an dadurch gekennzeichnet, daB die strukturellen Ele- dem ersten Satz von strukturellen Elementen befe- mente Abschnitte der auBeren Rumpfstruktur bil- stigt sind. den, die nacheinander entlang der Lange des Wasserfahrzeugs angeordnet sind. 20 21. Wasserfahrzeug nach einem der vorhergehenden Anspriiche, dadurch gekennzeichnet, daB die 14. Wasserfahrzeug nach Anspruch 13, dadurch auBere Rumpfhaut von dem Hauptrumpf mit einem gekennzeichnet, daB die strukturellen Elemente Abstand von zwischen 0,1 und 0,05 der Schiffs- von jedem auBeren Rumpfstrukturabschnitt in breite des Wasserfahrzeugs beabstandet ist. einem aneinandergelagerten Verhaltnis zu den 25 strukturellen Elementen des nachsten benachbar- 22. Wasserfahrzeug nach einem der Anspriiche 1 bis ten Rumpfstrukturabschnitts angeordnet sind. 20, dadurch gekennzeichnet, daB die auBere Rumpfhaut von dem Hauptrumpf mit einem 15. Wasserfahrzeug nach Anspruch 13 oder 14, Abstand von im wesentlichen 1/15 der Schiffsbreite dadurch gekennzeichnet, daB die Enden der struk- 30 des Wasserfahrzeugs beabstandet ist. turellen Elemente von jedem auBeren Rumpfstruk- turabschnitt von den Enden der Elemente des 23. Wasserfahrzeug nach Anspruch 4, dadurch nachsten benachbarten auBeren Rumpfstrukturab- gekennzeichnet, daB die Fliissigkeitsenthaltungs- schnitts beabstandet sind. raume zwschen der auBeren Rumpfhaut und dem 35 Hauptrumpf sich uber die Wasserlinie des Wasser- 16. Wasserfahrzeug nach Anspruch 15, dadurch fahrzeugs erstrecken, und in dem ein Lieferungs- gekennzeichnet, daB ein auBeres Rumpfhautteil mittel vorgesehen ist, urn ein trages Gas an die eines auBeren Rumpfstrukturabschnitts und ein Raume zu liefern. auBeres Rumpfhautteil des nachsten benachbar- ten auBeren Rumpfstrukturabschnitts durch ein 40 24. Wasserfahrzeug nach Anspruch 4, dadurch Entspannungsgelenk (223) aneinander ange- gekennzeichnet, daB die Fliissigkeitsenthaltungs- schlossen sind, wobei die auBeren Rumpfhautteile raume zwischen der auBeren Rumpfhaut und dem der beiden auBeren Rumpfstrukturabschnitte eine Hauptrumpf sich uber die Wasserlinie des Wasser- kontinuierliche Haut an dem Gelenk bilden, wah- fahrzeugs erstrecken, und ein Vakuumanwen- rend die andere Rumpfstruktur an dem Verbin- 45 dungsmittel (37, 38) vorgesehen ist, urn dungspunkt der auBeren Rumpfabschnitte Vakuumdrucke auf die Raume anzuwenden. strukturell diskontinuierlich bleibt. 25. Wasserfahrzeug nach Anspruch 4, dadurch 17. Wasserfahrzeug nach einem der Anspriiche 1 bis gekennzeichnet, daB die Fliissigkeitsenthaltungs- 15, dadurch gekennzeichnet, daB die strukturellen 50 raume zwischen der auBeren Rumpfhaut und dem Elemente eine Entspannungszone (21G) einschlie- Hauptrumpf vorher ausgewahlte getrennte Fliissig- Ben, in der Teile der strukturellen Elemente entfernt keitsenthaltungsraume (39, 40, 41) umfassen, in werden, urn Spannungsiibertragung in der Zone zu dem ein Lieferungsmittel vorgesehen ist, urn ein entlasten, und die auBere Rumpfhaut ein Entspan- unter Druck gesetztes trages Gas an wenigstens nungsgelenk (223) in der Zone einschlieBt. 55 einen der vorher ausgewahlten Raume zu liefern, wobei der Stand des Wassers in dem wenigstens 18. Wasserfahrzeug nach einem der Anspriiche 1 bis einen Raum auf einen Stand unter der Wasserlinie 11, dadurch gekennzeichnet, daB die auBere des Wasserfahrzeugs gebracht werden kann. Rumpfhaut langgestreckte auBere Hautabschnitte

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26. Wasserfahrzeug nach Anspruch 25, dadurch tion de base dans des sens ecartes du plan de la gekennzeichnet, daB die vorher ausgewahlten portion de base et du meme cote, de la portion de Fliissigkeitsenthaltungsraume sich uber die Was- base, la pluralite d'elements structurels etant agen- serlinie des Wasserfahrzeugs erstrecken, und in cee en une pluralite, de jeux, les elements structu- dem ein Vakuumanwendungsmittel (37, 38) vorge- 5 rels d'un tel premier jeu (21 A) etant fixes en sehen ist, urn Vakuumdrucke auf wenigstens einen positions predefines a la surface exterieure de der vorher ausgewahlten Raume anzuwenden, coque principale et menageant des surfaces de wobei der Stand des Wassers in dem wenigstens support ecartees de la coque principale et les ele- einen Raum auf einen Stand uber der Wasserlinie ments structurels d'un jeu suivant (21 B) etant fixes des Wasserfahrzeugs gebracht werden kann. w aux surfaces de support menagees par un jeu pre- cedent (21 A) et menageant des surfaces de sup- 27. Wasserfahrzeug nach Anspruch 26, dadurch port degagees plus loin de la coque principale que gekennzeichnet, daB die vorher ausgewahlten les surfaces de support menagees par les ele- Raume wenigstens einen Backbord- und einen ments structurels du jeu precedent, I'enveloppe Steuerboardraum in wenigstens einem der Bug- is exterieure de coque etant fixee aux surfaces de oder Heckgebiete des Wasserfahrzeugs enthalten. support menagees le plus loin de la coque princi- pale du navire. 28. Wasserfahrzeug nach Anspruch 27, dadurch gekennzeichnet, daB das Lieferungsmittel fur unter 2. Navire (10) ayant une coque principale (14), une Druck gesetztes trages Gas zum Liefern eines tra- 20 enveloppe de coque exterieure (22) et une struc- gen Gases an vorbestimmte der vorher ausgewahl- ture de coque exterieure (15) qui degage I'enve- ten Raume und das Vakuumanwendungsmittel zur loppe de coque exterieure depuis la coque Anwendung von Vakuumdrucken auf vorbestimmte principale et qui est fixee sur une surface exterieure der vorher ausgewahlten Raume derart sind, daB de coque principale du navire, caracterise en ce der Wasserstand in den vorbestimmten der vorher 25 que la coque principale comporte des premiers et ausgewahlten Raume dabei auf vorbestimmte deuxiemes elements (24, 22C) et en ce que la Stande uber oder unter der Wasserlinie des Was- structure exterieure de coque forme les premiers serfahrzeugs gebracht werden kann, urn (i) der elements de I'enveloppe exterieure de coque, la gesamten Ballasteffekt zu erhohen, indem der structure exterieure de coque comportant une plu- Stand des Wassers in den vorher ausgewahlten 30 ralite d'elements structurels (21) chacun compor- Raumen erhoht wird, (ii) den Ballasteffekt an einem tant une portion de base (24) ayant des premiers et Ende des Fahrzeugs zu erhohen und ihn an dem deuxiemes bords opposes et des premieres et anderen Ende des Fahrzeugs zu verringern, indem deuxiemes parois laterales inclinees vers I'exterieur der Wasserstand auf einen Stand uber der Wasser- (23) et qui s'etendent respectivement depuis les linie des Schiffs in vorher ausgewahlten Raumen 35 premiers et deuxiemes bords de la portion de base an dem einen Ende gebracht wird, und auf einen en des sens qui s'ecartent du plan de portion de Stand unter der Wasserlinie an dem anderen Ende base et du meme cote de la portion de base, les des Schiffs, urn den Trimm des Schiffs zu andern, elements structurels assembles se trouvant en des oder (iii) die Wasserstande des Wassers in den vor- positions predefinies menageant les premieres her ausgewahlten Backbord- und Steuerboardrau- 40 sections d'enveloppe exterieure de coque et des men uber oder unter der Wasserlinie einzustellen, surfaces de support ecartees de la coque princi- urn eine Schlagseite in dem Wasserfahrzeug zu pale a laquelle sont fixees les deuxiemes sections andern oder zu berichtigen. de structure exterieure de coque.

Revendications 45 3. Navire (10) ayant une coque principale (14), une enveloppe de coque exterieure (22) et une struc- 1. Navire (10) ayant une coque principale (14), une ture de coque exterieure (15) qui degage I'enve- enveloppe de coque exterieure (22) et une struc- loppe de coque exterieure depuis la coque ture de coque exterieure (15) qui degage I'enve- principale et qui est fixee a une surface exterieure loppe de coque exterieure depuis la coque so de la coque principale du navire, caracterise en ce principale et qui est attachee a une surface exte- que la structure de coque exterieure comporte une rieure de la coque principale du navire, caracterise pluralite de sections (222) et en ce que la structure en ce que la structure de coque exterieure com- exterieure de coque forme les sections de I'enve- porte une pluralite d'elements structurels (21) dont loppe de coque exterieure, la structure exterieure chacun comporte une portion de base ayant des 55 de coque comportant une pluralite d'elements premiers et deuxiemes bords opposes et des pre- structurels (21 D) chacun preforme avec une sec- mieres et deuxiemes parois laterales inclinees vers tion d'enveloppe de coque exterieure (222) tel que I'exterieur (23) qui s'etendent respectivement lorsque les elements structurels sont assembles en depuis les premiers et deuxiemes bords de la por- positions predefinies suite a la fixation a la coque

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principale, les sections d'enveloppe de coque exte- tions de structure de coque exterieure agences rieure sont assemblies dans I'enveloppe de coque successivement le long du navire. exterieure a I'ecart de la coque principale. 14. Navire selon la revendication 13, caracterise en ce 4. Navire selon I'une ou I'autre des revendications 1 , 2 5 que les elements structurels de chaque section de ou 3, caracterise en ce que la structure de coque structure de coque exterieure sont disposes en rap- exterieure et sa fixation a la coque principale est port bout-a-bout avec les elements structurels de la telle a assurer des vides de reception de fluide section suivante adjacente de structure de coque (155) entre la coque principale et I'enveloppe exte- exterieure. rieure de coque principale leur permettant le libre 10 remplissage. 15. Navire selon la revendication 13 ou 14, caracterise en ce que les extremites des elements structurels 5. Navire selon la revendication 4, caracterisee en ce de chaque section de structure de coque exterieure que la communication (23, 24, 25 26, 27, 28; 25) sont ecartees des extremites des elements de la est assuree pour un ecoulement d'eau de libre rem- 15 section suivante adjacente de structure de coque plissage des vides de reception de fluide. exterieure.

6. Navire selon la revendication 5, caracterise en ce 1 6. Navire selon la revendication 1 5, caracterise en ce que I'ecoulement d'eau de libre remplissage des qu'une partie d'enveloppe de coque exterieure vides de reception de fluide provient de la masse 20 d'une section de structure de coque exterieure et d'eau dans laquelle le navire se deplace. une partie d'enveloppe de coque exterieure de la section suivante adjacente de structure de coque 7. Navire selon la revendication 5 ou 6, caracterise en exterieure sont raccordees I'une a I'autre par un ce que la communication assurant un ecoulement joint de detente des contraintes (223) les parties d'eau de libre remplissage des vides de reception 25 d'enveloppe de coque exterieure des deux sections de fluide comporte des ouvertures (23, 24; 25) de structure de coque exterieure formant une enve- dans I'enveloppe de coque exterieure qui s'eten- loppe continue au joint alors que la structure de dent le long du fond du navire. coque exterieure retient une structure discontinue au joint des sections de structure de coque exte- 8. Navire selon la revendication 5 ou 6, caracterise en 30 rieure. ce que la communication assurant I'ecoulement d'eau de libre remplissage des vides de reception 1 7. Navire selon I'une ou I'autre des revendications 1 a de fluide comporte la regulation des moyens 15, caracterise en ce que les elements structurels d'apport (23, 24, 25, 26, 27, 28). prevoient une zone de detente de contrainte (21G) 35 dans laquelle des parties d'element structurels sont 9. Navire selon la revendication 8, caracterise en ce eliminees pour la detente de transmission de con- que les moyens de regulation d'apport comportent trainte et I'enveloppe de coque exterieure prevoit un des moyens a vannes normalement ouvertes joint de detente de contrainte (223) dans la zone. (27,28) qui se referment ou admettent la fermeture sous les conditions exigeant la fermeture. 40 18. Navire selon I'une ou I'autre des revendications 1 a 11, caracterise en ce que I'enveloppe de coque 10. Navire selon I'une ou I'autre des revendications 5 a exterieure comporte des sections allongees d'enve- 7, caracterise en ce que la communication assurant loppe exterieure agencees pour s'etendre essen- I'ecoulement d'eau de libre remplissage des vides tiellement en sens transversal par rapport au sens de reception de fluide comporte des ouvertures 45 longitudinal du navire. (25) situees exclusivement dans la partie de I'enve- loppe de coque exterieure qui s'etend le long du 19. Navire selon la revendication 1 ou 2 ou I'une ou fond de la coque principale. I'autre des revendications 4 a 18, en association avec la revendication 1 ou 2, caracterise en ce que 1 1 . Navire selon I'une ou I'autre des revendications pre- so les elements structurels comportent des elements cedentes, caracterise en ce que les elements struc- en forme de canalisation. turels sont des elements allonges. 20. Navire selon la revendication 1 9, caracterise en ce 1 2. Navire selon la revendication 1 1 , caracterise en ce que les elements structurels torment une structure que les elements structurels s'etendent en sens 55 alveolee ouverte comportant un premier jeu d'ele- longitudinal du navire. ments structurels (21 A) fixes a la coque principale et un deuxieme jeu d'elements structurels (21 B) 1 3. Navire selon la revendication 1 1 ou 1 2, caracterise fixes au premier jeu d'elements structurels. en ce que les elements structurels torment des sec-

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21 . Navire selon I'une ou I'autre des revendications pre- certains des vides preselectionnes sont tels que le cedentes, caracterise en ce que I'enveloppe de niveau d'eau dans les vides preselectionnes sont coque exterieure est ecartee par rapport a la coque apportes au besoin a des niveaux predetermines principale d'une distance entre 0.01 et 0.05 des au dessus ou au dessous de la ligne de flottaison baux du navire. 5 du navire, permettant ainsi (i) d'augmenter I'effet global du lest en augmentant le niveau d'eau dans 22. Navire selon I'une ou I'autre des revendications 1 a les vides preselectionnes, (ii) d'augmenter I'effet 20, caracterise en ce que I'enveloppe de coque global du lest a une extremite du navire et de le exterieure est ecartee par rapport a la coque princi- diminuer a I'autre en relevant le niveau d'eau a un pale d'une distance essentiellement de 1/15eme 10 niveau au dessus de la ligne de flottaison du navire des baux du navire. dans les vides a un niveau au dessous de la ligne de flottaison et a I'autre extremite du navire pour 23. Navire selon la revendication 4, caracterise en ce modifier I'assiette du navire ou (iii) pour ajuster au que les vides de reception de fluide entre I'enve- dessus et en dessous de la ligne de flottaison le dif- loppe exterieure de coque et la coque principale is ference! des niveaux d'eau dans les vides preselec- s'etendent au dessus de la line de flottaison du tionnes a babord et a tribord pour modifier ou navire et dont les moyens d'apport (35, 36) sont corriger un faux-bord du navire. prevus pour apporter un gaz inerte aux vides.

24. Navire selon la revendication 4, caracterise en ce 20 que les vides de reception de fluide entre I'enve- loppe exterieure de coque et la coque principale s'etendent au dessus de la line de flottaison du navire et des moyens d'apport de depression (37, 38) sont prevus pour amener la pression negative 25 aux vides.

25. Navire selon la revendication 4, caracterise en ce que les vides de reception de fluide entre I'enve- loppe exterieure de coque et la coque principale 30 comportent des vides preselectionnes de segrega- tion de reception de fluide (39, 40, 41), dont les moyens d'apport (35, 36) sont prevus pour fournir un gaz inerte sous pression dans un seul au mini- mum des vides preselectionnes, suivant lesquels le 35 niveau de I'eau dans un des vides au minimum est amene au choix au dessous de la ligne de flottaison du navire.

26. Navire selon la revendication 25, caracterise en ce 40 que les vides de reception de fluide s'etendent au dessus de la ligne de flottaison du navire et suivant lequel des moyens d'apport de pression negative (37, 38) sont prevus pour apporter les pressions negatives dans I'un au minimum des vides prese- 45 lectionnes, suivant lesquels le niveau d'eau dans un vide au minimum est amene au choix a un niveau au dessus de la ligne de flottaison du navire.

27. Navire selon la revendication 26, caracterise en ce so que les vides preselectionnes comportent au mini- mum un vide a babord et a tribord dans une zone au minimum a I'avant et a I'arriere du navire.

28. Navire selon la revendication 27, caracterise en ce 55 que les moyens d'apport de gaz inerte sous pres- sion apportant un gaz inerte en certains des vides preselectionnes et les moyens d'apport de pression negative pour amener les pressions negatives en

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