A multi-use vessel designed to receive a variety of float-on modules that accommodate project specialty equipment and still allow the mother vessel to operate in the traditional construction mode. The vessel may be formed as a new construction or by converting an existing vessel. The vessel is provided with a deck between the gunwales (tween deck) that is lower than the gunwales. The tween deck is provided with docking ports to receive and secure float-on modules containing the equipment required for the desired operation. The tween deck may also be provided with a moon pool for laying pipeline directly through the vessel. The vessel is ballasted to position the tween deck below the water line so that the float-on modules may be installed or removed. The gunwales of the vessel may include one or more cranes spaced along the length of the vessel for moving equipment on the float-on modules or performing installation operations and lifts as necessary. The rear gunwales may include lowering equipment for lowering equipment such as templates to the sea floor.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The invention is generally related to vessels used to provide offshore
 construction services and more particularly to a vessel that is adaptable
 to provide a variety of services.
 2. General Background
 In the production of hydrocarbons offshore, a variety of services are
 required. These services include laying pipeline on the sea floor and the
 installation of structures and equipment used in the drilling and
 production of hydrocarbons. The means used to lay pipeline depends upon a
 variety of factors such as water depth and pipe diameter. Directing the
 pipeline into the water at an angle nearly vertical to the water surface
 is typically used in deep water. This is generally referred to as J-Lay.
 Directing the pipeline into the water at a relatively shallow angle is
 typically used in shallow water. This is generally referred to as S-Lay.
 Each method uses different equipment to accomplish the task. J-Lay may use
 a near vertical support and stinger. In S-Lay, the pipe may be unwound
 from a reel as it is laid or pipe joints may be welded together on the
 laying vessel during the laying operation. Installing equipment and
 structures requires the use of lowering equipment such as cranes capable
 of handling the weight of the equipment.
 Having one vessel capable of performing each operation is expensive as this
 can result in a vessel remaining idle when the specific operation that it
 is dedicated to is not required. Also, current vessels dedicated to
 specific tasks are only capable of speeds at six to seven knots.
 The current state of the art leaves a need for vessels that have multiple
 use capability and greater speed.
 SUMMARY OF THE INVENTION
 The invention addresses the above need. What is provided is a multi-use
 vessel designed to receive a variety of float-on modules that accommodate
 project specialty equipment and still allow the mother vessel to operate
 in the traditional construction mode. The vessel may be formed as a new
 construction or by converting an existing vessel. The vessel is provided
 with a deck between the gunwales (tween deck) that is lower than the
 gunwales. The tween deck is provided with docking ports to receive and
 secure float-on modules containing the equipment required for the desired
 operation. The tween deck may also be provided with a moon pool for laying
 pipeline directly through the vessel. The vessel is ballasted to position
 the tween deck below the water line so that the float-on modules may be
 installed or removed. The gunwales of the vessel may include one or more
 cranes spaced along the length of the vessel for moving equipment on the
 float-on modules or performing installation operations and lifts as
 necessary. The rear gunwales may include lowering equipment for lowering
 equipment such as templates to the sea floor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 Referring to the drawings, it is seen in FIG. 1-6 that the invention is
 generally indicated by the numeral 10. The multi-use vessel 10 is
 generally comprised of a buoyant, self-propelled ship 12.
 The deck (tween deck) 14 between the gunwales 16 is lower than the gunwales
 16. The tween deck 14 is provided with a plurality of docking ports 18.
 The ship is provided with several thrusters. At least one tunnel thruster
 20 is positioned near the bow. Full three hundred sixty-degree rotating,
 retracting, thrusters 22 are positioned forward. Full three hundred
 sixty-degree rotating, retracting, thrusters 24 are positioned aft.
 Standard ship-type propellers 26 with rudders are provided at the stern.
 Although not shown, it is preferable that two each of thrusters 22 and 24
 be provided.
 The ship 12 may be built as a new construction or by converting an existing
 ship. For the type of work envisioned, the preferred ship size is
 approximately eight hundred to nine hundred feet long, one hundred fifteen
 feet wide, and capable of submerging the desired tween deck 14 ten feet
 below the water line. It is preferred that the tween deck 14 provide a
 work area of five hundred forty-eight feet in length and eighty feet in
 width. Existing "lash ships" that incorporate a submerged elevator
 platform design originally intended to handle two "Danube-Sea" barges each
 one hundred twenty-five feet long and thirty-six feet wide will fit within
 these parameters and thus conversion will save time and money over new
 construction.
 The following generally includes the main operations required to convert a
 lash ship. The aft transverse sternlog is removed and replaced with a
 hinged aft and downward watertight door operated by hydraulic cylinders.
 The elevator platform is removed and the elevator winches and arm area are
 modified to accept a deep water lowering apparatus and equipment suitable
 for operations in ten thousand feet of water. The original number three
 tween deck dry barge storage hold is converted to a ten-foot maximum
 submerged deck for float in operation. The forward superstructure is
 enlarged. The thrusters and tunnel thrusters are added. The below-deck
 tanks are converted as necessary to support the new vessel ballasting
 requirements for submerging the tween deck. Pedestal cranes may be added
 along the gunwales to support construction activities. An overhead crane
 may be added to support template lowering operations. Pipeline stinger
 handling davits/winches are added to the original elevator support area.
 Docking ports are added to the tween deck. Quick connect/disconnect points
 are added to support the various work operations.
 In operation, a float-on module is installed as follows. FIG. 1 illustrates
 the ship 12 at the normal operating draft. The ship 12 is ballasted to
 lower the tween deck 14 approximately ten feet below the water surface as
 shown in FIG. 2 and 3. One or more float-on modules 30 are floated above
 the tween deck 14 and positioned to align docking probes 28 with the
 docking ports 18. The ship 12 is then de-ballasted to raise the tween deck
 14 into contact with the float-on modules 30 such that the docking probes
 28 are received in the docking ports 18. For the sake of clarity,
 accessory equipment on the ship 12 and work equipment on the float-on
 module 30 are not shown.
 FIG. 7 illustrates the initial position of the module 30 over the deck 14.
 It can be seen that the docking probe 28 is in a first retracted position
 in the module 30. FIG. 8 illustrates the docking probe 28 moving to its
 second extended position toward the docking port 18. FIG. 9 illustrates
 the docking probe 28 being received in the docking port 18 during the
 initial de-ballasting of the ship. FIG. 10 illustrates the docking probe
 28 fully inserted into the docking port 18. The latches 32 provided on the
 docking probe 28 are moved to their second extended position and received
 in complementary grooves 34 in the docking port 18 to lock the module 30
 in position. As indicated by the water line, FIG. 11 illustrates the
 vessel after it has been de-ballasted and is at the normal operating
 draft.
 As seen in FIG. 12-19, the modules 30 may be used for a variety of
 equipment for different operations. It is also seen in these Figures that
 one or more cranes 36 are provided along the gunwales 16. Lowering
 equipment 38 is provided on the gunwales 16 at the aft section of the
 ship. FIG. 12 and 13 illustrate modules 30 with equipment 40 for laying
 pipeline in the J-Lay mode through a moon pool 42. Laying pipeline in the
 J-Lay mode may also be accomplished over the side of the vessel. FIG. 14
 and 15 illustrate modules 30 with equipment 46 for laying pipeline in the
 S-Lay mode. A stinger 48 is provided at the rear of the ship 12. Barges 50
 are illustrated on the sides of the ship 12 for providing pipe as it is
 needed during the welding and laying operations. FIG. 16 and 17 illustrate
 modules 30 with equipment 52 (reels) for laying pipe or flexible line on
 the seafloor. FIG. 18 and 19 illustrate the ship 12 set up for lowering
 templates 54 to the sea floor.
 Because many varying and differing embodiments may be made within the scope
 of the inventive concept herein taught and because many modifications may
 be made in the embodiment herein detailed in accordance with the
 descriptive requirement of the law, it is to be understood that the
 details herein are to be interpreted as illustrative and not in a limiting
 sense.