GB1594938A - Free floating marine structure - Google Patents

Free floating marine structure Download PDF

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Publication number
GB1594938A
GB1594938A GB4666376A GB4666376A GB1594938A GB 1594938 A GB1594938 A GB 1594938A GB 4666376 A GB4666376 A GB 4666376A GB 4666376 A GB4666376 A GB 4666376A GB 1594938 A GB1594938 A GB 1594938A
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United Kingdom
Prior art keywords
gas
marine structure
vessel
chambers
hull
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
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GB4666376A
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Hart A S C
Original Assignee
Hart A S C
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hart A S C filed Critical Hart A S C
Priority to GB4666376A priority Critical patent/GB1594938A/en
Priority to ES77464239A priority patent/ES464239A1/en
Publication of GB1594938A publication Critical patent/GB1594938A/en
Expired legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B39/00—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude
    • B63B39/02—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude to decrease vessel movements by displacement of masses
    • B63B39/03—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude to decrease vessel movements by displacement of masses by transferring liquids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
    • B63B1/02—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement
    • B63B1/10—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls
    • B63B1/107—Semi-submersibles; Small waterline area multiple hull vessels and the like, e.g. SWATH

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • Ocean & Marine Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Artificial Fish Reefs (AREA)
  • Revetment (AREA)
  • Wind Motors (AREA)

Description

(54) FREE FLOATING MARINE STRUCTURE (71) I, ARTHUR STANLEY COLQU HOUN HART, a British subject of White Gates, Smallridge, Axminster, Devon, England, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a free-floating marine structure, for example a multi-hull vessel.
According to the present invention there is provided a free-floating marine structure comprising a deck structure and at least one hull structure which comprises a hull unit connected to the deck structure by a nacelle which defines a gas chamber extending downwardly through the hull unit, which chamber is open at the bottom of the hull unit to the sea and is closed at the top so as to contain a gas cushion within the chamber, the structure being provided with valve means operable to release from the chamber, or admit into the chamber, gas under pressure under the control of control means which includes means responsive to the actual attitude of the marine structure and is arranged to maintain the marine structure substantially in a predetermined attitude.
Preferably, the marine structure is in the form of a multi-hull vessel having a plurality of such hull structures.
The marine structure preferably comprises at least two nacelles. The respective valves of the chambers may then be connected together by a gas duct system so that by opening the valves, the gas pressures in the chambers can be equalised.
For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is a side elevation of one embodiment of the invention, comprising a twinhulled sea-going vessel, Figure 2 is a view of the stern of the vessel, Figure 3 diagrammatically illustrates a system of air ducts included in the vessel, and Figure 4 shows very diagrammatically a plan view of a twin-hulled vessel including a control system for supplying gas to gas chambers of the vessel.
Referring to Figures 1 and 2, the vessel comprises two identical hull structures 1 which are arranged generally parallel to one another in spaced-apart relationship and are connected by a deck structure 7, including living and working quarters for the personnel of the catamaran.
The starboard hull structure will now be described although of course the description applies equally to the port hull structure. As clearly shown in Figure 1, the structure 1 comprises a generally cylindrical hull unit 2 connected to a torsion tube 3 above the hull unit 2 by means of upright nacelles 4. Each nacelle defines a gas chamber 5 which is closed at the top by an end wall 6 and which extends downwardly through the hull unit 2 and is open at the bottom of the hull unit so that the sea can enter the chamber 5. A gas cushion is accordingly trapped in each gas chamber above the water level in the chamber.The hull unit 2 includes ballast sections 8, where the main ballast of the vessel is carried, and also trim sections 9, where final adjustments can be made to the ballasting of the vessel to allow for the load which the vessel is carrying, weather and sea conditions and similar factors. The ballasting is such, however, that the vessel floats with the waterline 10 of the vessel between the hull units 2 and the deck structure 7. Figure 2, shows that the hull structure l is provided with a power unit 11, including driven propeller and rudder.
Referring to Figures 1 and 3. the cham bers 5 are respectively provided in their end walls 6 with valves V which are connected together by a system of ducts 12 and are preferably pneumatically operated although they could be mechanically or electromechanically operated. The valves are three-way valves. In a first position, each valve is closed and then isolates the respective chamber 5. In a second position the valve connects its chamber to the system of ducts 12 so as to enable pressure equalisation between the chambers. The third position of the valve disconnects the chamber from the duct system and connects it to a compressed air source 13 which supplies air under pressure through a distributor 14 and the valve V to the selected chamber 5. In this way, the air pressure can be increased, if desired.Of course, the duct system or the nacelle chambers will include pressure relief means (not shown) venting to atmosphere.
The valves V are controlled by control means which includes means responsive to the actual attitude of the vessel and is arranged to maintain the vessel substantially in a predetermined attitude.
The vessel can be operated with all the valves V in their open position. Under such conditions, a wave arriving at the bow of the vessel causes an increase in air pressure in the two forward nacelle chambers. However, rather than causing the bow to rise bodily with the wave as would happen in a conventional twin-hulled vessel, the increased pressure is immediately distributed amongst the other nacelles by way of the system of ducts 12, so that the bow does not rise as rapidly as it would otherwise do and at the same time the stern of the vessel will tend to rise under the increased air pressure in the nacelles there. In this way, pitching of the vessel is reduced. For analogous reasons "heel" (rolling) is also reduced.Moreover, because of the relatively small, or even extremely small, waterplane area of the nacelles and the semisubmersible nature of the hull structures with the hull units fully submerged and the nacelles partially sub merged, only relatively slight "heave" is experienced with the vessel. Another advantage of the vessel, due to the air pressure equalisation, is to ease stresses in the vessel caused by the waves. In particu lar, the attitude of the vessel is adjusted, owing to a distribution of changes in air pressure in any particular nacelle chambers to the remaining chambers, before the hull structures of the vessel are subjected to any appreciable stress due to the waves, and this result is especially important in the case of a vessel of high tonnage.
In order to adjust the internal pressure in any one or more of the nacelle chambers, for example to adjust the internal water lines, the external waterline, or to compen sate for any localised heavy loading of the vessel, the or each appropriate valve is operated to connect the chamber(s) to the air source 13. In Figure 1, all the internal waterlines 30 are level with the waterline 10 of the vessel but they may be made either higher or lower. The vessel could be pro vided with main and internal waterlevel transducers and with air pressure transduc ers whose outputs are connected to a com puter on the vessel which, in accordance with pre-set criteria in the computer, oper ates the air valves so as to provide correc tion or compensation of the nacella air pressures automatically.In such an arrange ment, each nacelle chamber may include a vertical tube of dielectric material on which are sited at selected intervals, say 1 or 2 ft.
apart, latch reed switches. A float, in which is embedded a permanent magnet, is posi tioned within the tube and floats at the water surface in the chamber. As the water level varies, the float moves up and down within the tube and each time it passes a latch reed switch, the switch closes to produce a pulse which is amplified and fed to a computer. This is suitably programmed so as to control operation of the air supply valves so as to maintain the actual vessel attitude as closely as possible at a predeter mined vessel attitude.
Referring to Figure 4, there is shown a control system for operating the valves (V) and the pressure relief means (R) of the nacelle chambers 5. In this particular case, the vessel has only three nacelles in each hull structure and the nacelle chambers of each hull structure are supplied from a single air supply source. For opening and closing the valves V and pressure relief means R, there is provided a controller in the form of a gimbalmounted plate 15 fitted with a pendulum. At each of six locations around the periphery of the plate contact switches A and B are respectively mounted above and below the plate, these switches A, B being operative to control the valve V and pressure relief means R respectively. In operation, if a wave approaches say the port bow, the wave will cause the port bow to start to rise so as to cause the switch B associated with the port bow nacelle to be operated by the gimbal-mounted plate to vent that nacelle. Thus, the extra buoyancy at the port bow produced by the wave will be offset by a reduction in air pressure in the nacelle chamber. The system works corres pondingly for a trough between waves so as to open the valve V of the port bow chamber and increase the nacelle air press ure. Of course, all the valves V and relief means R of the various nacelle chambers operate in the same way, thereby keeping the attitude of the vessel closely constant.
In a modification, each hull unit may comprise respective elliptoid sections for the nacelles connected end-to-end, with their greater cross-sectional widths aligned generally in the fore-aft direction of the vessel.
This has the advantage that the effect of tidal currents on the vessel, in particular in the sideways directions, is minimised.
In Figures 1 and 2 there is shown a further modification in which the gas chambers 5' are incorporated within the nacelles, these chambers being flared outwardly in their lower end regions as indicated at 50'. In this way, skin friction effects can be reduced.
Figure 1 shows that a further improvement in performance can be obtained by flaring each gas chamber to a greater extent in the aft direction than in the fore direction. In view of flaring the gas chambers outwardly, the hull unit 2', instead of having rounded undersides, has upright lower side walls and a generally plane undersurface as Figure 2 clearly shows.
In one mode of operation, at least one of the valves can be closed. Then, the air in all the isolated chambers would serve as a "cushioning" effect against the action of the waves. Indeed, in a modification, a multihull vessel, such as a twin-hulled vessel, has one or more isolated nacelle chambers in each hull structure.
It is not intended that the invention as disclosed herein be confined to multi-hull vessels. In fact, it could be adapted to single-hulled floating vessels such as caissons, floating harbours, wide barges and the like.
Lastly, it is mentioned that whilst the described vessel and modifications are designed and adapted so that normally they float with the waterline between the hull units and the deck structure, by using compressed air sources capable of delivering sufficient air pressures, the weight of the vessel can be supported almost exclusively by the air cushioning in the nacelle chambers, thus reducing skin friction effects and drag to a negligible amount.
WHAT I CLAIM IS: 1. A free-floating marine structure comprising a deck structure and at least one hull structure which comprises a hull unit connected to the deck structure by a nacelle which defines a gas chamber extending downwardly through the hull unit, which chamber is open at the bottom of the hull unit to the sea and is closed at the top so as to contain a gas cushion within the chamber, the structure being provided with valve means operable to release from the chamber, or admit into the chamber, gas under pressure under the control of control means which includes means responsive to the actual attitude of the marine structure and is arranged to maintain the marine structure substantially in a predetermined attitude.
2. A marine structure according to claim 1, and which is in the form of a multi-hull vessel haying a plurality of such hull structures.
3. A marine structure according to claim 1 or 2, wherein at least two such nacelles are incorporated in the marine structure, and a gas duct system is provided interconnecting some or all of the said valve means so that by opening the valve means, the gas pressures in the chambers can be equalised.
4. A marine structure according to claim 1, 2 or 3, wherein gas supply means are connected to the valve means for supplying gas under pressure to the or any said gas chamber when the associated valve means is opened.
5. A marine structure according to any preceding claim, wherein the valve means includes pressure relief means operative to exhaust the chambers to atmosphere.
6. A marine structure according to any preceding claim, wherein at least two such nacelles are incorporated in the marine structure and the respective valve means of the gas chambers each comprise a multiway valve having a closed position in which the associated gas chamber is isolated, a position in which the associated gas chamber is brought into connection with gas supply means, connected to the various valve means, so as to become charged with gas under pressure, and a position in which the associated gas chamber is brought into connection with a gas duct system interconnecting the valve means, whereby to provide for gas pressure equalisation between the gas chambers.
7. A marine structure according to any preceding claim, wherein the control means comprises a gimbal-mounted plate, responsive to the actual attitude of the marine structure, and contact switches, operative to control operation of the valve means, are mounted above and below said plate so as to be operated by the plate as the actual attitude of the marine structure changes in use.
8. A marine structure according to any preceding claim, wherein the control means comprises water level detector means in the gas chamber or gas chambers and computer means arranged to receive gas chamber water level information from the detector means and to control operation of the valve means accordingly.
9. A marine structure according to any preceding claim in the form of a water-going vessel, wherein the nacelles are elliptoidal with their greater cross-sectional widths aligned generally with the fore-aft direction of the vessel.
10. A marine structure according to any preceding claim in the form of a water-going vessel, wherein the lower end region of the
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. comprise respective elliptoid sections for the nacelles connected end-to-end, with their greater cross-sectional widths aligned generally in the fore-aft direction of the vessel. This has the advantage that the effect of tidal currents on the vessel, in particular in the sideways directions, is minimised. In Figures 1 and 2 there is shown a further modification in which the gas chambers 5' are incorporated within the nacelles, these chambers being flared outwardly in their lower end regions as indicated at 50'. In this way, skin friction effects can be reduced. Figure 1 shows that a further improvement in performance can be obtained by flaring each gas chamber to a greater extent in the aft direction than in the fore direction. In view of flaring the gas chambers outwardly, the hull unit 2', instead of having rounded undersides, has upright lower side walls and a generally plane undersurface as Figure 2 clearly shows. In one mode of operation, at least one of the valves can be closed. Then, the air in all the isolated chambers would serve as a "cushioning" effect against the action of the waves. Indeed, in a modification, a multihull vessel, such as a twin-hulled vessel, has one or more isolated nacelle chambers in each hull structure. It is not intended that the invention as disclosed herein be confined to multi-hull vessels. In fact, it could be adapted to single-hulled floating vessels such as caissons, floating harbours, wide barges and the like. Lastly, it is mentioned that whilst the described vessel and modifications are designed and adapted so that normally they float with the waterline between the hull units and the deck structure, by using compressed air sources capable of delivering sufficient air pressures, the weight of the vessel can be supported almost exclusively by the air cushioning in the nacelle chambers, thus reducing skin friction effects and drag to a negligible amount. WHAT I CLAIM IS:
1. A free-floating marine structure comprising a deck structure and at least one hull structure which comprises a hull unit connected to the deck structure by a nacelle which defines a gas chamber extending downwardly through the hull unit, which chamber is open at the bottom of the hull unit to the sea and is closed at the top so as to contain a gas cushion within the chamber, the structure being provided with valve means operable to release from the chamber, or admit into the chamber, gas under pressure under the control of control means which includes means responsive to the actual attitude of the marine structure and is arranged to maintain the marine structure substantially in a predetermined attitude.
2. A marine structure according to claim 1, and which is in the form of a multi-hull vessel haying a plurality of such hull structures.
3. A marine structure according to claim 1 or 2, wherein at least two such nacelles are incorporated in the marine structure, and a gas duct system is provided interconnecting some or all of the said valve means so that by opening the valve means, the gas pressures in the chambers can be equalised.
4. A marine structure according to claim 1, 2 or 3, wherein gas supply means are connected to the valve means for supplying gas under pressure to the or any said gas chamber when the associated valve means is opened.
5. A marine structure according to any preceding claim, wherein the valve means includes pressure relief means operative to exhaust the chambers to atmosphere.
6. A marine structure according to any preceding claim, wherein at least two such nacelles are incorporated in the marine structure and the respective valve means of the gas chambers each comprise a multiway valve having a closed position in which the associated gas chamber is isolated, a position in which the associated gas chamber is brought into connection with gas supply means, connected to the various valve means, so as to become charged with gas under pressure, and a position in which the associated gas chamber is brought into connection with a gas duct system interconnecting the valve means, whereby to provide for gas pressure equalisation between the gas chambers.
7. A marine structure according to any preceding claim, wherein the control means comprises a gimbal-mounted plate, responsive to the actual attitude of the marine structure, and contact switches, operative to control operation of the valve means, are mounted above and below said plate so as to be operated by the plate as the actual attitude of the marine structure changes in use.
8. A marine structure according to any preceding claim, wherein the control means comprises water level detector means in the gas chamber or gas chambers and computer means arranged to receive gas chamber water level information from the detector means and to control operation of the valve means accordingly.
9. A marine structure according to any preceding claim in the form of a water-going vessel, wherein the nacelles are elliptoidal with their greater cross-sectional widths aligned generally with the fore-aft direction of the vessel.
10. A marine structure according to any preceding claim in the form of a water-going vessel, wherein the lower end region of the
or each gas chamber is flared outwardly.
11. A marine structure according to claim 10, wherein the flaring of the or each gas chamber is greater in the aft direction than in the fore direction.
12. A marine structure according to any preceding claim, including gas supply means capable of supplying gas under sufficient pressure that the weight of the marine structure is supported almost exclusively by the gas pressure in the gas chambers.
13. A marine structure substantially as hereinbefore described with reference to the accompanying drawings.
GB4666376A 1977-10-28 1977-10-28 Free floating marine structure Expired GB1594938A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB4666376A GB1594938A (en) 1977-10-28 1977-10-28 Free floating marine structure
ES77464239A ES464239A1 (en) 1977-10-28 1977-11-09 Free floating marine structure

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB4666376A GB1594938A (en) 1977-10-28 1977-10-28 Free floating marine structure

Publications (1)

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GB1594938A true GB1594938A (en) 1981-08-05

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GB4666376A Expired GB1594938A (en) 1977-10-28 1977-10-28 Free floating marine structure

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GB (1) GB1594938A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2135262A (en) * 1983-02-22 1984-08-30 Blohm Voss Ag A semi-submersible drilling platform
WO1993006002A1 (en) * 1991-09-26 1993-04-01 Elf Aquitaine Production Controlled-heave floating oil platform

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2135262A (en) * 1983-02-22 1984-08-30 Blohm Voss Ag A semi-submersible drilling platform
WO1993006002A1 (en) * 1991-09-26 1993-04-01 Elf Aquitaine Production Controlled-heave floating oil platform
FR2681831A1 (en) * 1991-09-26 1993-04-02 Elf Aquitaine FLOATING OIL PLATFORM WITH CONTROLLABLE PILLING.
US5363788A (en) * 1991-09-26 1994-11-15 Elf Aquitaine Production Floating oil rig with controllable heave
GB2265864B (en) * 1991-09-26 1995-02-01 Elf Aquitaine Floating oil rig with controllable heave

Also Published As

Publication number Publication date
ES464239A1 (en) 1978-07-01

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PCNP Patent ceased through non-payment of renewal fee