US3739737A

US3739737A - Marine platforms

Info

Publication number: US3739737A
Application number: US00181422A
Authority: US
Inventors: R Baier
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-09-17
Filing date: 1971-09-17
Publication date: 1973-06-19
Anticipated expiration: 1990-06-19

Abstract

A floating platform capable of remaining stable during inclement weather conditions. The platform includes a central buoyant member equipped with a plurality of double articulated support members and float chambers located at spaced locations about its periphery. The support members are pivotally movable between retracted positions generally aligned with a longitudinal axis of the central buoyant member and extended positions radiating outwardly of the central buoyant member. The float chambers are pivotally movable between retracted positions tucked under their associated support members and an extended or vertical position by controlled flooding, and in a subsequent operation, the buoyant member is raised above the surface of the water. Damping devices are provided at the extremities of the float chambers and stationkeeping can be achieved by the use of anchors or by discharging water from appropriate ports in the float chambers.

Description

Baier 1 MARINE PLATFORMS [76] Inventor: Robert J. Baier, 3960 West Chester Pike, Newtown Square, Pa. 19073 22 Filed: Sept. 17,1971

[21] Appl. No.: 181,422

[52] US. Cl. 114/05 D, 61/46.5, 1l4/0.5 F,

1 14/435 [51] Int. Cl B63b 35/44 [58] Field of Search l14/O.5 D, 0.5 BD,

ll4/O.5 R, 0.5 F, 43.5, 46, 123, 77 R, 665 P; 6l/46.5, 48; 14/27, 28

[56] References Cited UNITED STATES PATENTS 2,212,088 .8/1940. Tomassi 114/665 P X 3,176,644 4/1965 Thomas et al.. ll5/0.5 R X 3,633,369 1/1972 Lawrence 114/0.5 D X 3,673,973 7/1972 Glosten...., 114/0.5 D 3,673,974 7/1972 Harper 11410.5 D

[111 3,739,737 dune 19, 1973 Primary Examiner-Milton Buchler Assistant ExaminerBarry L. Kelmachter Attorney-Albert W. Hilburger [57] ABSTRACT A floating platform capable of remaining stable during inclement weather conditions. The platform includes a central buoyant member equipped with a plurality of double articulated support members and float chambers located at spaced locations about its periphery. The support members are pivotally movable between retracted positions generally aligned with a longitudinal axis of the central buoyant member and extended positions radiating outwardly of the central buoyant member. The float chambers are pivotally movable between retracted positions tucked under their associated support members and. an extended or vertical position by controlled flooding, and in a subsequent operation, the buoyant member is raised above the surface of the water. Damping devices are provided at the extremities of the float chambers and stationkeeping can be achieved by the use of anchors or by discharging water from appropriate ports in the float chambers.

22 Claims, 12 Drawing Figures Patented June 19, 1973 6 Sheets-Sheet 1 Patented June 19, 1973 6 Sheets-Sheet 5 Patented June 19, 1973 6 Sheets-Sheet 4 Patented June 19, 1973 6 Sheets-Sheet 5 Patented June 19, 1973 6 Sheets-Sheet 6 MARINE PLATFORMS The present invention relates to marine platforms and more particularly to mobile marine platforms which can be readily deployed and, when deployed, remain stable even during inclement weather conditions.

In recent years it has been increasingly desirable to utilize marine platforms which are located at substantial distances from land. They have served a variety of uses ranging from oceanographic research to weather stations, and for oil exploration and missile tracking purposes. Whatever the use, however, such previously known platforms have had a number of serious drawbacks. Either they were very stable as in the case of marine platforms rigidly mounted on the ocean floor or they were freefloating structures which did not have sufficient stability to permit their use during inclement weather conditions.

In the former case, such platforms were usually massive structures which were extremely expensive to build, required extensive time for construction, and once deployed were not again movable. However, in the latter instance, while marine platforms have been designed and built which could be fairly readily deployed, they could generally be used only during relatively mild weather conditions. These were sometimes anchored to the bottom by means of flexible lines in a conventional manner. In some other instances, they were provided with float chambers which assumed a normally horizontal position for transport between home port and the deployed locations and were movable to a vertical position at the time of deployment.

in accordance with the present invention, a mobile marine platform is disclosed which is-capable of remaining stable even during inclement weather conditions. To accomplish this objective, the natural frequency of the marine platform is tunedto something other than the natural frequency of the largest waves and highest winds which are likely to be encountered by the platform and still not be disruptive of the work performed by the personnel assigned to it. It would be preferred that the natural frequency of the platform would be lower than that of the waves. This tuning, in other words, simply means that the resulting movement of the platform will not be of the magnitude of the wave action so long as the normal frequency ofthe wave is higher than the frequency of the platform. It will be recalled, of course, that the smaller the waves, the higher their frequency. When the waves become larger, that is, have an ever lower frequency, possibly even lower than the platform was designed to resist, the platform will begin to approach the full amplitude of the wave movement.

It will further be recalled that the natural frequency of any object is determined by the spring rate (for example, pounds per foot) of its support and the mass of the object. Change in either spring rate or mass of the object alters its natural frequency. In keeping with this definition, it is seen that a conventional vessel or ship of the type illustrated has a very high spring rate measured in hundreds of tons per foot of immersion, and it therefore responds to wave action quite readily. However, when the same displacement is provided in a plurality of long slender vertical floats, the spring rate (for example, tons per foot of immersion) is greatly reduced and the natural frequency is accordingly changed to alower value. Of course, it is recognized that a stable platform with displacement provided by slender vertica] floats would be difficult to transport from one location to another and furthermore would have substantially greater draft than a conventional ship of the same displacement.

By means of the present invention, the mobility of conventional design is combined with the stability of the slender vertical float design. Hence, the configuration of the present invention provides a platform including a main buoyant member equipped with a plurality of double articulated support members and float chambers located at spaced locations about its periphery. The support members are pivotally movable between retracted positions generally aligned with a longitudinal axis of the platform and extended positions radiating outwardly of the platform. The float chambers are pivotally movable between retracted positions tucked under their associated support member and an extended or vertical position by controlled flooding, and in a subsequent operation the buoyant member is raised above the surface of the water. Damping devices are provided at the extremities of the float chambers so as to be positioned in the depths where the water is substantially calmer than at the surface and thereby further add to the stability of the platform. in addition, station keeping can be achieved by the use of anchors or by discharging jets of water from appropriate ports in the float chambers.

When the support members and float chambers are in their extended positions, the platform is provided with a maximum degree of stability and this configuration provides yet a further benefit. If hoists or davits are positioned along the gunwales of diagonally opposite support members, they are substantially aligned across the geometric center of the platform. In this manner, operations on extremely long articles such as pipe or submarine cable are enhanced because of the extended support length thereby provided. In addition, increased stability is realized due to the geometrically centered position of the davits such that hoist loads along the geometrical center will not roll or tilt the platform.

Accordingly, it is a primary object of the invention to provide a floating marine platform capable of remaining stable during inclement weather conditions.

It is another object of the invention to provide a floating marine platform which can be readily converted from the configuration of a conventional vessel to that of a stable platform. A related object is to provide a vessel equipped with a plurality of support members located at spaced locations about its periphery wherein the support members are pivotally movable between retracted positions aligned with a longitudinal axis of the vessel and extended positions radiating outwardly of the platform. Another related object is to provide such a vessel equipped with a plurality of double articulated support members and float chambers located at spaced locations about its periphery wherein not only are the support members pivotally movable between their retracted and extended positions but also wherein the float chambers are pivotally movable between retracted positions tuckedunder their associated support member and an extended or downwardly directed vertical position.

A further object of the invention is the provision of a floating marine platform which, when deployed, has a natural frequency different from the natural frequency of the largest waves it is intended to encounter. A related object is to provide the floating platform with a low spring rate. Another related object is to provide the platform with support in the deployed position by means of long slender vertical columns or float chambers from which the water has been removed.

Still a further object of the invention is the provision of a floating marine platform having support members which substantially enlarge the beam of the vessel while substantially retaining the previous length of the platform so as to increase stability about both the roll and pitch axes.

Still a further object of the invention is the provision of a floating marine platform supported on generally long slender vertical columns equipped with retractable damping plates to further improve the stability of the platform. A related object is the provision of the platform wherein the float chambers are provided with pumps capable of directing jets of water outwardly through appropriate ports in order to achieve station keeping.

Other and further objects and advantages of the invention will be apparent or will be described in the written specification which follows taken together with the accompanying drawings.

In the drawings, wherein like numerals refer to like parts throughout:

FIG. 1 is a perspective view illustrating the invention in the configuration of a conventional vessel prior to deployment;

FIG. 2 is a perspective view of the invention in the configuration of a fully deployed floating marine platform;

FIG. 3 is a top plan view of the structure shown in FIG. 2;

FIG. 4 is a section view taken along lines 4--4 in FIG.

FIG. 5 is a detail perspective view of parts illustrated in FIG. 3;

FIG. 6 is a schematic side elevation view of a float chamber in the retracted position and showing same in phantom in its extended position;

FIG. 7 is a side elevation view of a float chamber in the extended position in order to illustrate the station keeping apparatus;

FIG. 8 is a section view taken along lines 8-8 of FIG. 7 to illustrate the station keeping apparatus in even greater detail;

FIG. 9 is a detail side elevation view, partly cut away and in section, of parts shown in FIG. 4;

FIG. 10 is a top plan view of another embodiment of the invention;

FIG. 11 is a side elevation view of the construction illustrated in FIG. 10 with certain parts cut away and in section; and

FIG. 12 is a detail side elevation view, partly cut away and in section, of parts illustrated in FIG. 11 but showing a somewhat different arrangement of parts.

Refer now to the drawings and in particular to FIG. 1 wherein the floating platform is shown in the configuration of a conventional vessel which is capable of traveling at a reasonable rate between port and a working location. The platform 20 is comprised of a central buoyant member 22 having a deck 24 and a deck house 25 in which may be housed quarters for the crew, fuel storage, and appropriate equipment. In addition, the central member 22 may be provided with a wheel house 26 to serve as a central control station for operation of the marine platform 20. Therefore, as will be seen in the description which follows, the central buoyant member 22 is truly the core member of the marine platform 20 and the element about which all activity takes place.

The construction of the invention which permits the platform 20 to assume the deployed configuration shown in FIG. 2 from the configuration of a conventional vessel (Flg. 1) will now be described. As is seen most clearly in FIG. 3, the central buoyant member 22 is generally square in plan configuration although the deck 24 has extensions 28 at either end. Adjacent each of the vertical corners of the central member 22 are a pair of first hinges (see especially FIGS. 1-3) 30 which pivotally mount an associated support member 32 to the central member 22. Each support member 32 is itself buoyant and therefore aids the floatation of the marine platform 20 when it assumes the configuration of FIG. 1.

Similarly, a pair of second hinges 34 (see especially FIGS. 2 and 4) mount for pivotal movement a float chamber 36 to each support member 32 adjacent its extremity. Therefore, in the configuration of FIG. 1, the support members 32 all assume a position generally aligned with a longitudinal axis of the central member 22 and each of the float chambers 36 is folded in a manner tucked under its associated support member 32. In this situation, the float chambers 36 are all fully buoyant.

In order to deploy support members 32, that is, to move them from the configuration shown in FIG. 1 to that shown in FIG. 2, it is possible for a derrick 38 suitably mounted on the deck 24 of the central buoyant member 22 to engage its line 40 with a suitable protuberance on the outer surface of the support member 32 and by swinging in its customary manner to move the support member 32 to an extended position radiating outwardly from the geometric center of the central buoyant member 22.

It should be noted that the first hinges 30 mounting each support member 32 to the central buoyant member 22 are adjacent the gunwales of the platform 20 and an articulated linkage 42 serve to connect the opposite corner of the support member 32 on the same end mounting the hinges 30 and extends to locations substantially on the center line of the central buoyant member 22 for pivotal movement thereat. The articulated linkage 42 serves to permit the swinging move ment of each support member 32 between the fully retracted position indicated in FIG. 1 and the fully extended position of FIG. 2. The linkage 42 (FIG. 5) includes a pair of

links

44 and 46 which are hinged medially at 48 in such a manner that in order to move to its maximum open position, as shown in FIG. 2 the

links

44 and 46 might be caused to pass over center or might provide locking of the

links

44 and 46 in the central position. In either case, a suitable actuator 50 is preferably employed to drive the

links

44 and 46 through their last few degrees of movement and then hold them in their extreme position.

In this manner, an adequate locking arrangement is achieved to maintain each support member 32 in its extended position until it is desired to retract it. In the alternative to use of the derrick 38 to swing each support member 32 between its retracted and extended positions, it may be desirable to utilize a tugboat or other utility vessel (neither shown).

As seen especially well in FIGS. 7 and 8 the construction of the float chambers 36 includes an internal frame structure 52 and external pressure plates 54.

In order for each float chamber 36 to move from its retracted or horizontal position to its extended or vertical position (FIGS. 4 and 6), a suitable valve arrangement can be provided operable to permit flooding of the float chambers 36. When the platform is in the configuration illustrated in FIG. 1, the float chambers 36 are buoyant and are devoid of water. A typical valve arrangement is schematically illustrated in FIG. 6 and includes a sea valve 56 located at a deepest point on the float chamber and an air valve or port 58 located near the hinge 30. By suitably opening the sea valve 56 and the air valve 58, the float chamber 36 is caused to swing downwardly (counterclockwise in FIG. 6) on the hinges 34 to its extended or vertical position.

When it is desired to retract the float chambers 36, the procedure is reversed and water within the float chambers is expelled, with the aid of, for example, compressed air from a source represented schematically by an air compressor 60 mounted on the deck 24 (FIG. 3). Of course, it will be appreciated that water can also be expelled from the float chambers 36 by simply pumping it out in a suitable manner (not shown). When substantial floatation of each float chamber 36 is achieved, it will move to its fully retracted position. A second articulated linkage 62 (FIG. 4) extends between the support member 32 and the float chamber 36 and is pivotally mounted to each respectively at locations distant from the hinges 34. Similar to the articulated linkage 42, the second articulated linkage 62 includes

links

64 and 66 which are centrally hinged at 68 and are secured by means of an actuator 70 in the extended position shown in FIGS. 2 and 4. In this instance also, the

links

64 and 66 may be so designed as to pass over center when the float chamber 36 is moved to its extended position and thereby achieve a locking of the float chamber'36 in that position or alternatively might be held in the centered position by the actuator 70.

Refer now to FIGS. 7 and 8. In order to maintain the position of the marine platform 20 on location, it may be desirable to direct jets of water from each of the float chambers 36 in a direction opposite that of the forces being imposed on the platform 20. To this end, a suitable pump 72 is mounted within a cylindrical housing 73 and is suitably positioned in azimuth to take in water through any one of a plurality of ports 74 a-h positioned around the periphery of the float chamber 36 andto expel the water through an associated oppositely positioned port. Each of the float chambers 36 is provided with such an arrangement of ports located substantially in a plane as near as possible to the mean centroid of the air and water drag areas for a minimum induced movement. By operating the station keeping mechanisms in each of the float chambers 36 in a unitary fashion, a powerful jet stream is provided which serves to hold the marine platform 20 steady against adverse wind forces or water currents.

Cooperatively associated with each of the float chambers 36 is a damping mechanism 76 (FIGS. 4 and 9) which includes an elongated damper support column 78 having a length substantially the same as that of the float chamber 36 and a damper plate 80 fixed to the end of the column. The column 78 is pivotally mounted by means of a universal joint 82 to a piston 84 slidably received in a damper extension cylinder 86 fixed within the float chamber 36. The column 78 is longitudinally movable through the extension cylinder 86 which serves as a guide for the column as it is extended or retracted. Additionally, when the column 78 is in the fully retracted position such that the damper plate 80 is positioned adjacent an extremity of the float chamber 36, the extension cylinder 86 serves to provide adequate protection for the relatively fragile column and allows retraction of the entire damping and float chamber mechanism as a unit tucked under the relatively fragile column.

At such time that the float chambers 36 assume the vertical or extended position (FIGS. 4 and 6), air from the air compressor mounted on the deck 24 of the platform 20 is utilized to drive the piston 84 downwardly in the extension cylinder 86. Suitable seals 88 fixed to the piston 84 serve to maintain pressure in the extension cylinder 86 while permitting longitudinal movement of the column 78. In an alternate construction, the seals 88 can be eliminated and the damper plate can be extended by simply permitting the column 78 and piston 84 to descend by gravity alone. A stop ring 90 is provided adjacent the extreme end of the extension cylinder 86 to prevent further descent of the piston 84. In addition, a plurality of latches 91 are pivotally mounted on the piston 84 and biased outwardly (FIG. 9) to engage the lower edge of the stop ring 90 preventing relative motion between the column 78 and the extension cylinder 86 when the former is in the extended position. The stop ring 90 may be removably mounted on the extension cylinder 96 in the event it would be desirable to remove the piston. Furthermore, a cable 92 is utilized to release the latches 91 and to retract the column 78. The cable 92 is suitably mounted on the internal frame structure 52 of the float chamber 36 and extends to the inboard side of the piston 84 to which it is firmly fastened as at the eye 94. When the column 78 is fully retracted, the damper plate 80 rests snugly against the extreme end of the float chamber 36 (FIG. 4) tucked under the support member 32.

The damper plate 80 is preferably perforated to allow for restrictive flow of water through it. The column 78 is designed to locate the damper plate 80 as far as possible from the surface of the water consistent with structural requirements to reduce the effect of the waves. Furthermore, the purpose of the universal joint 82 is to prevent the build-up of excessive stresses in the column 78 should wave action cause the platform 20 to roll to the degree not structurally provided for by the column.

By utilizing a damping mechanism 76 of the construction just described associated with each of the float chambers 36, the platform 20 is capable of withstanding an advanced sea state before beginning to roll and pitch excessively. The reader will appreciate that with the column 78 locating the damper plate 80 as far from the surface of the water as possible consistent with the structural capabilities of the column, the effect of the surface waves on the plate will be minimal and the tendency of the platform 20 to move will be counteracted by the damping action of the plate.

In another embodiment of the damping mechanism,

the column 78 may be replaced with a cable (not Very often platforms of the configuration of the marine platform illustrated in FIG. 1 are utilized for operations on submarine cable or underwater pipe. Geometrically, the present invention is uniquely capable of performing such operations even during inclement weather conditions. For example, it has been noted that if a first series of davits 96 are suitably mounted along the gunwales of a support member 32, and a second series of davits 98 are similarly mounted along the gunwales of a support member 32 diagonally opposite the previously mentioned support member, the first series of davits 96 will be substantially aligned with the second series of davits 98. In this manner, a substantial length of submarine cable or underwater pipe 99 can be supported by the platform 20 (FIG. 2) and be operated on in a desired fashion. At the same time, the platform 20 is in a condition of maximum stability which will permit the work to continue even in a sea state which would previously have been unacceptable for such an operation.

In operation, the marine platform 20 will normally assume the configuration of FIG. 1 whenever it is in port or proceeding toward or returning from a deployment location. The platform 20 can be utilized in this configuration (FIG. 1) if weather conditions are favorable and stability is not a problem. If the platform begins to roll excessively due to increased wave activity, the support members 32 can be deployed to their extended positions without extending the float chambers 36. Such a configuration serves to increase roll stability equal to the pitch stability of the conventional vessel configuration illustrated in FIG. 1 and may be sufficient to perform the intended function. This configuration could also be used in water too shallow to completely deploy the float chambers 36. If adequate depth is available and the seas begin to rise causing adverse movements of the platform, the valves 56 and 58 are opened to permit flooding of the float chambers 36. As

water replaces air within the float chambers 36, they begin to sink and swing from a substantially horizontal position, rotating about the hinges 34 until they are substantially vertical and, nearly filled with water, are suitably locked in position. At this point, air from the air compressor 60 is directed into the float chambers 36 to thereby force the water to exit via the valves 56. As the water is removed, the increased buoyancy will cause the platform 20 to ride even higher in the water until the central buoyant member is completely clear of the water. Additional water can be removed until a desired clearance of the central buoyant member 22 above the water is achieved. Since wind conditions and water currents might cause the platform 20 to tilt, such a condition can be compensated for by suitably adjusting the level of the water in selected float chambers.

With all of the support members 32 thus locked in a cruciform configuration, and each of the float chambers 36 similarly locked in a vertical position, the damping mechanisms 76 associated with the float chambers 36 are suitably deployed. When thus deployed, the platform 20 is subject to a minimum of outside disturbance which might otherwise cause it to pitch or roll excessively. Furthermore, with the first series of davits 96 generally aligned with the second series of davits 98 on diagonally opposite support members 32, the platform 20 is capable of supporting activities such as work on submarine cable or underwater pipe with a minimum of disturbance from inclement weather conditions. Of course, whenever desirable, the aforesaid operations can be reversed to permit the platform 20 to return to its original configuration.

Another embodiment of the invention is illustrated in FIGS. 10, 11, and 12. In this embodiment, a floating platform is provided which is particularly suited for off-shore pipe laying operations. Modern, but conventional, pipe laying barges require considerable deck area for the performance of various operations on the pipe such as positioning, welding, tensioning, inspection, and applying protective coatings. As previously discussed, the productivity of all these operations would be greatly increased if they were performed on a platform substantially free from roll and pitch movements in all but the heaviest of seas.

The floating platform 100 illustrated in FIGS. 10, 11 and 12 meets the qualifications of a vessel having the deck areas required to perform the necessary operations and yet of a design providing increased stability over conventional vessels during inclement weather conditions. The platform 100 is shown with a main buoyant member 102 having a large deck area 104 upon whichis constructed a plurality of work stations 106 and associated pipe supporting davits 108. The work stations 106 and davits 108 are aligned to position a length of pipe 110 along the centerline of the platform 100.

As is most clearly seen in FIG. 10, the platform is constructed such that it can selectively assume a conventional configuration (solid lines) or a deployed configuration (phantom lines). Thus, a pair of associated buoyant support members 112 are pivotally mounted on hinges 114 adjacent each of the vertical corners at one end of the main buoyant member 102. In a manner similar to that earlier described with reference to sup-' port members 32, the support members 112 can be deployed by means of a derrick or a tugboat (neither shown). They are also provided with an articulated linkage 116 to permit swinging movement between the fully retracted position and the fully extended position and with actuators 118 to lock them in the extended position. As with the platform 20, this platform can be used in either the retracted or deployed configurations.

It will be apparent that when the support members 112 are in their retracted positions, a tunnel 120 is defined by the longitudinal spacing between the support members except in the region of a ramp structure 122 half of which is integral with each of the support members. When the support members 112 assume their retracted positions, the halves of the ramp structure meet along a common interface 124.

By reason of the construction illustrated in FIGS. 10 and 11, operations can be easily performed on the length of pipe 110 supported by the davits 108 and extending generally along a centerline of the platform 100. An upper surface 126 of the ramp structure 122 is somewhat lower than the level of the deck 104 and has a sufficient arc to permit the assembled pipe 110 to be gradually lowered into the water at the end of the platform 100 to maintain a reasonable level of bending load in the pipe. An extended pipe support structure or stinger 128 is removably attached to the outermost ends of the support members 112 to provide additional support for the pipe 110 as it continues to be lowered into the water. Of course, the stinger 128 is attached to the support members 112 when they are in their retracted positions. However, when the support members are extended (phantom lines in FIG. 10) the stinger 128 is removably attached to the rearmost extremity 130 of the deck 104 (FIG. 12) which actually overlies deck surfaces 132 of the support members 112 when they are retracted.

As with the platform 20, the platform 100 is preferably provided with float chambers 134 and with damping plates 136 which operate in the same manner as previously described. lndeed, in all other respects, the

operation of the platform 100 is similar to that of the platform 20.

Since many modifications and variations of the present invention are possible within the spirit of the instant disclosure, it is intended that the embodiments disclosed be deemed illustrative and not restrictive, reference being had to the following claims rather than to the specific description to indicate the scope of this invention.

I claim:

1. A floating platform capable of remaining stable during inclement weather conditions comprising: a central buoyant member substantially horizontally disposed, a plurality of support members and associated float chambers, first hinges mounting each of said support members to said central buoyant member, said support members being movable on said first hinges in substantially the plane of said central member between a retracted position and an extended position relative to said central buoyant member, and second hinges mounting each of said float chambers on its said associated support member for movement between a retracted position substantially co-planar with said central buoyant member and an extended position lying in a plane transverse to the plane of said central buoyant member.

2. The platform as set forth in claim 1 wherein said support members are substantially axially aligned with a longitudinal axis of said central buoyant member when in their retracted positions and including drive means for moving said support members from their retracted positions to their extended positions angularly disposed relative to said longitudinal axis, and wherein each of said float chambers has a plurality of ports therein and valve means associated with each of said ports operable to permit the inward flow of water to thereby flood the interior of said float chamber causing each of said float chambers to move from a substantially horizontal retracted position to a substantially vertical extended position.

3. The platform as set forth in claim 2 including means for selectively expelling water from said float chambers when said float chambers are in the extended position to thereby adjust the height above the water of said central buoyant member.

4. The platform as set forth in claim 2 including first locking means for securing said central buoyant member and said support members against relative movement in said extended positions and second locking means for securing said support members and said float chambers against relative movement in said extended positions.

5. The platform as set forth in claim 2 including a plurality of intake and exhaust ports positioned around the periphery of each of said float chambers and located substantially in a plane at the level of the main centroid of the air and water drag areas for said platform, and pump means selectively positioned in azimuth to draw in water through one of said intake ports and to expel water through one of said exhaust ports associated therewith for maintaining a predetermined position of said platform.

6. The platform as set forth in claim 2 including damping means operatively associated with each of said float chambers and movable between a first position in a substantially retracted relationship with said associated float chamber and a second position substantially extended beyond said associated float chamber.

7. The platform as set forth in claim 6 wherein said damping means includes a support column substantially axially aligned with said float chamber and a damper plate mounted to an end of said support column and lying in a plane transverse to a longitudinal axis of said support column, said support column being movable between said first position whereat said plate is positioned adjacent an extremity of said float chamber and second second position whereat said plate is distant from said extremity.

8. The platform set forth in claim 7 including actuating means for moving said support column between said first and second positions.

9. The platform as set forth in claim 7 wherein said damping means includes a universal joint mounting said support column to said float chamber to enable swinging movement of said support column relative to said float chamber.

10. The platform as set forth in claim 9 wherein said damping means includes means releasably locking said support column against axial movement in said second position.

11. The platform as set forth in claim 1 wherein said support members are substantially aligned with a longitudinal axis of said central buoyant member when in their retracted positions and are angularly disposed relative to said longitudinal axis when in their extended positions and wherein first and second of said support members are mounted to said central buoyant member at opposed locations and have axes substantially parallel to one another and angularly disposed relative to the longitudinal axis of at least a third of said support means when said support means are in their extended positions, and including first davit means mounted at spaced locations on the upper surface and along the gunwales of said first support member and second davit means at spaced locations on the upper surface and along the gunwales of said second support member, all of said first and second davit means being substantially aligned across the geometric center of said platform when their associated support members assume their extended positions.

12. The platform as set forth in claim 11 wherein said central buoyant member is substantially rectangular in a plan view and wherein said first hinges mounting said first and second support members to said central buoyant members are at diagonally opposed locations.

13. The platform as set forth in claim 12 including drive means for moving said support members from their retracted positions to their extended positions and wherein each of said float chambers has a plurality of ports therein and valve means associated with each of said ports operable to permit the inward flow of water to thereby flood the interior of said float chamber causing each of said float chambers to move from a substantially horizontal retracted position to a substantially vertical extended position.

14. The platform as set forth in claim 13 including means for selectively expelling water from said float chambers when said float chambers are in the extended position to thereby adjust the height above the water of said central buoyant member.

15. The platform as set forth in claim 13 including first locking means for securing said central buoyant member and said support members against relative movement in said extended positions and second locking means for securing said support members and said float chambers against relative movement in said extended positions.

16. The platform as set forth in claim 13 including damping means operatively associated with each of said float chambers and movable between a first position in a substantially retracted relationship with said associated float chamber and a second position substantially extended beyond said associated float chamber.

17. The platform as set forth in claim 16 wherein said damping means includes a support column substantially axially aligned with said float chamber and a damper plate mounted to an end of said support column and lying in a plane transverse to a longitudinal axis of said support column, said support column being movable between said first position whereat said plate is positioned adjacent an extremity of said float chamber and said second position whereat said plate is distant from said extremity.

18. The platform as set forth in claim 1 including a pair of support members in side-by-side spaced relationship substantially aligned with a longitudinal axis of said central buoyant member when in their retracted positions and are angularly disposed relative to said longitudinal axis and to each other when in their extended positions, ramp means integral with each of said pair of support members defining a tunnel between said support members when in their retracted positions and having an upper surface below the surfaces of said central buoyant member and said support members and sloping downwardly away from said central buoyant member, and davit means mounted at spaced locations along a central axis on the upper surface of said central buoyant member for supporting elongated items above said central buoyant member and aligned with said tunnel.

19. The platform as set forth in claim 18 including means for selectively expelling water from said float chambers when said float chambers are in the extended position to thereby adjust the height above the water of said central buoyant member.

20. The platform as set forth in claim 18 including first locking means for securing said central buoyant member and said support members against relative movement in said extended positions and second locking means for securing said support members and said float chambers against relative movement in said extended positions.

21. The platform as set forth in claim 18 including damping means operatively associated with each of said float chambers and movable between a first position in a substantially retracted relationship with said associated float chamber and a second position substantially extended beyond said associated float chamber.

22. The platform as set forth in claim 21 wherein said damping means includes a support column substantially axially aligned with said float chamber and a damper plate mounted to an end of said support column and lying in a plane transverse to a longitudinal axis of said support column, said support column being moveable between said first position whereat said plate is positioned adjacent an extremity of said float chamber and said second position whereat said plate is distant from said extremity.