This invention relates to an apparatus for handling a boat. Background to the invention

Launch and recovery systems are known for handling small boats during launch from and recovery to a larger mothership. Earlier publication WO2012/069853 is one example useful for understanding the invention. Summary of the invention

According to a first aspect of the invention there is provided an apparatus to handle a boat, the apparatus comprising:

a cradle adapted to receive the boat within the cradle, the cradle being coupled to a mothership by a pivot coupling allowing pivotal movement between the boat and the mothership about the pivot coupling;

a movement mechanism configured to move the cradle relative to the mothership and/or the boat;

a position reference device detecting the position of the cradle relative to the boat; and

a transmission mechanism adapted for transmitting the output data from the position reference device to the movement mechanism, and wherein the movement mechanism controls the movement of the cradle relative to the mothership and/or the boat in response to the transmitted output data from the position reference device.

Optionally the pivot coupling permits sliding movement of the cradle relative to the mothership, optionally along a vertical axis. The pivot coupling optionally permits freedom of pitching movement of the cradle relative to the mothership, and/or the boat. The pivot coupling optionally permits freedom of heaving movement of the cradle relative to the mothership and/or the boat. Optionally, the movement mechanism can comprise one or more hoist devices, optionally having lines that are optionally connected between the cradle and the mothership. Optionally the lines from the hoist devices can be connected between the cradle and a frame disposed above the cradle. Optionally the hoist devices can be disposed on the frame. In some embodiments, the frame is mounted on the mothership above the stern of the mothership. The recess could alternatively be incorporated into a side of a vessel. The frame is optionally arranged vertically over and optionally spans across at least a portion of a recessed dock formed in the mothership. Optionally the cradle is suspended from the frame within the recessed dock. Optionally, more than one hoist line is provided between the frame and the cradle, and in some embodiments the cradle has at least one hoist line connected at each corner of the cradle.

Optionally the hoist device can comprise a winch, having a barrel driven in rotation to pay out and recover a line onto the barrel.

Optionally the hoist device can comprise a tensioning mechanism, comprising a plurality of sheave blocks, which may be movable relative to one another by means of a ram, e.g. a hydraulic ram. Optionally one sheave block can be fixed, for example on the frame, and the other can be movable relative to the fixed block. One end of the line reeved through the sheave blocks can be fixed, for example to the frame, and the other can be fixed to the cradle. Thus movement of the travelling block relative to the fixed block reels in the line. The gearing between the blocks can be adjusted to reel in a greater amount of line than the relative movement of the sheave blocks. The sheave blocks can be mounted on a vertical column in the frame. Suitable hoist systems are described in US 6,296, 232, the disclosure of which is incorporated by reference.

Optionally the set of fixed sheaves is moved relative to the set of movable sheaves by a driver, typically in the form of a hydraulic actuator such as a hydraulic cylinder. Optionally, retraction and extension of the hydraulic actuator changes the distance between the two sets of sheaves. Optionally the hydraulic actuator is mounted vertically in the column.

Optionally, more than one hoist device is provided, optionally comprising a winch. Each hoist device optionally has a respective line extending between a respective hoist device and a connection point on the cradle. Optionally the connection points on the cradle for the individual lines are spaced apart on different parts of the cradle, for example, near or at the corners of the cradle. Optionally the lines are individually controlled by the movement mechanism, so that different parts (e.g. corners) of the cradle can be raised and lowered relative to other parts of the cradle, optionally by operating particular winches or other hoist devices corresponding to those parts of the cradle to which the lines are attached. Optionally, each hoist device can be driven by a separate motor, which can be independently controlled by the movement mechanism. Optionally the hoist devices can be driven from a single power source, and can be individually controlled.

Optionally the movement mechanism comprises pairs of hoist devices. Optionally pairs of hoist devices are disposed forward and aft of the cradle. Optionally the hoist devices in each pair operate synchronously. Optionally each hoist device comprises two or more lines, in order to spread the lifting load such that the diameter of each line can be reduced in size in comparison to the diameter required if a single line is used. Optionally the lines attach to the cradle via a pivotable yoke.

Optionally the hoist device comprises a constant tension mechanism. The hoist mechanism may be driven by a hydraulic or an electric power supply. One suitable electric drive system may have the following components: efficient all electric drive, inverter vector control, and a tension/torque controller to automatically adjust in order to maintain a minimum value with the speed controlled by operator joystick. Optionally the movement mechanism can have a passive action to apply force to the cradle, for example, by buoyancy applied to submerged parts of the cradle or by passive operation of the winches or other hoist devices, for example, under constant tension control. Optionally the movement mechanism can actively control the movement of the cradle, for example, by driving the winches or other hoist devices, or by adjusting the buoyancy, or by driving a hydraulic motor. Optionally the movement mechanism can have both passive and active functions controlled by the control box. Optionally the movement mechanism is passive until the cradle is lifted, and while the cradle is being lifted, the movement mechanism is typically active. Optionally the cradle is lifted using a combination of active and passive functions of the movement mechanism. Optionally during cradle lifting the movement mechanism moves the cradle in concert with the boat, and the active function of the movement mechanism during lifting of the cradle typically synchronises the movement of the cradle and the boat.

Optionally in examples with hydraulic power systems, power arising from hydraulic fluid fluctuations can be stored transiently in hydraulic accumulators, and applied to the winches or other hoist devices when active force is required.

The position reference device optionally detects the movement of the cradle relative to the boat in the cradle, as well as the position of the cradle relative to the boat. In other words, the position reference device can optionally measure the clearance (distance between the cradle and the boat) and the relative movement (dynamic rate of change of distance between the cradle and the boat). In some examples, the position reference device can optionally detect acceleration of the boat relative to the cradle (rate of change of speed of movement), and can optionally comprise an accelerometer. Optionally, the apparatus can record the position and movement data relating to the relative position and movement between the boat and the cradle in order to recognise and record speeds and accelerations. For this purpose the apparatus can optionally have a memory device optionally provided on the position reference device and/or the movement mechanism. Optionally, the position reference device or the movement mechanism can determine trajectories of the boat relative to the cradle using comparisons of previous data sets, for example it can determine that the boat is approaching the cradle by comparing sequential distance data measurements, and can determine the likelihood of some or all of the following events occurring: whether impact is likely, which parts of the boat might be likely to collide with which parts of the cradle, and optionally when such impact is likely to occur, using the time stamped position data from the position reference device. Optionally apparatus can record movements and/or accelerations and can use the recorded data to predict movements of the boat relative to the cradle, and can initiate movement of the cradle earlier to compensate for the predicted movements of the boat.

In certain examples, the movement mechanism is driven to maintain a constant gap between the cradle and the boat while idling, and to reduce the gap at a predictable rate when winding in and recovering the boat.

Optionally the position reference device can comprise a signal reflector on one of the boat and the cradle and a signal transmitter and optionally a receiver on the other. The reflector can optionally be passive or active. Optionally the transducer can be provided on the cradle, but could optionally be on the boat instead.

Optionally the position reference device can comprise at least one LASER sensing device, which is typically mounted on the frame above the cradle, and is configured to track targets on the cradle and the boat, and to determine the difference in position between the cradle and the boat by comparison of the measured distances between the tracked targets. Suitable LASER devices are available from Leuze electronic GmbH. Optionally two LASER sensing devices can be used, one mounted in a forward position on the gantry and one mounted aft. Optionally the devices can operate continuously in order to scan the boat, cradle and mothership, in order to provide real-time relative positioning of each object during the handling process. The positioning data can be used to create a 3D visualisation of the relative positioning to aid the hoist device operator. Optionally the data from the LASER devices can be transmitted from the LASER sensing device(s) to the control box to inform the control of the movement mechanism.

Optionally the position reference device can comprise at least one linear measurement sensor. Optionally position reference devices can be provided on the frame above the cradle. Optionally the linear measurement sensor can comprise a cable optionally held in substantially constant tension between the cradle and the frame, whereby the cable is reeled in as the cradle approaches the frame and is reeled out as the cradle moves away from the frame. The direct connection through the cable at constant tension reports to the movement mechanism data concerning the position of the cradle relative to the frame of the mothership.

Likewise, the linear measurement sensor can comprise a cable held in substantially constant tension between the boat and the frame, whereby the cable is reeled in as the boat rises and is reeled out as the boat falls away, the direct connection through the cable at constant tension reporting to the movement mechanism data concerning the position of the boat relative to the frame of the mothership. The data from the linear measurement sensors on cradle and the boat can be collected and compared by the movement mechanism control unit, and the relative positions of the boat and the cradle can thereby be inferred. Cables can be connected to the boat and to the cradle by means of releasable catches. Reels paying the cable in and out can be connected to the frame, typically above the cradle and the boat. Suitable linear measurement sensors are available from SICK AG. Linear measure measurement sensors can be fitted forward and aft of the cradle, either on one side only or on each side. Optionally the linear measurement sensors measure the distance in the reeled out cable between the frame and the cradle and between the frame and the boat. Optionally the four linear measurement devices can be attached between the frame and the boat, optionally port & starboard, fore & aft. Once the boat is fully engaged in the cradle and the latching device is deployed, a deck hand could pull each cable down from the linear measurement devices using a lanyard and connect the cable to the boat via a releasable connector. Once attached the linear measurement sensors can accurately measure the position of each connection to the boat, and as these will be in known locations relative to the keels the gap between the boat and the cradle can be readily deduced. Optionally, the position reference device comprises at least one sensor, but optionally can comprise more than one sensor, which can optionally report position and movement data at different parts of the cradle, for example at or near the ends of the cradle, or at or near the corners of the cradle. Intermediate sensors between the ends (optionally between the corners) are also useful.

Optionally the position reference device can comprise at least one acoustic signal transducer, such as a piezoelectric transducer. Optionally the position reference device can comprise at least one sonar device. The use of sonar devices to determine the relative position between two submerged objects within a column of water is well known to the skilled person, and numerous suitable sonar devices and other transducers could be used for this purpose. Suitable acoustic transducers are available from Kongsberg Simrad.

Optionally, the position reference device comprises an acoustic signal generator and an acoustic signal receiver, optionally disposed within the same sensor unit, although they could be separate. Optionally the position reference device is mounted on the cradle.

Optionally the cradle comprises a frame, for example a U-shaped frame having a base and side walls, and optionally the recess is provided between the sidewalls and above the base. Optionally, the boat is received within the recess between the sidewalls and above the base, and is supported on the base when the boat has been recovered from the water. Optionally the frame of the cradle comprises fenders on the entrance, base and/or side walls. Optionally these fenders take the form of rollers rotationally mounted on arms. Optionally the arms can be pivotally mounted on a pivot point on the frame, and can be articulated around the pivot point to move the rollers relative to the frame. Optionally the rollers on the base can be moved into a raised configuration around the pivot point when the cradle is being lifted, to provide a soft landing for the boat as it contacts the cradle during the lifting process. Optionally the rollers are raised by a hydraulic system. Optionally the rollers are collapsed by the weight of the boat as the cradle is raised out of the water.

Optionally, the position reference device is mounted on the base of the cradle, optionally on the upper surface of the base of the cradle, and is optionally arranged to transmit and optionally to receive acoustic signals between the base of the cradle and the boat (optionally the underside of the boat), when the boat is in the cradle.

Optionally, the frame can incorporate one or more buoyancy devices such as tanks or solid low density material. Optionally, buoyancy tanks can be equally distributed over the cradle. Buoyancy tanks can optionally be sealed. The buoyancy devices can optionally comprise sealed compartments on each side. Optionally at least some of the buoyancy in the buoyancy devices may be adjustable, but substantially most of the buoyancy can be fixed, in order to avoid uncontrolled redistribution of ballast during pitch and heave motions. Optionally buoyancy devices can be individually adjusted (e.g. by partial flooding during use or after commissioning) to attain the optimum neutral position in still water to match the specific boat hull profile and displacement. Optionally the buoyancy devices can be disposed in the sidewalls of the frame of the cradle and will optionally be located at the forward and aft ends of the side walls.

In certain examples, the buoyancy can be adjusted to match the motions of the cradle and the boat as far as possible. The adjustment can be made before installation on the mothership, where the type of boat to be handled with the apparatus is known and will not change, or can be optionally adjusted in use to trim the cradle with respect to the boat so that the two move together in response to water motion, e.g. wave movement. When the buoyancy is adjusted to trim the cradle with respect to the boat, this can reduce the power demand on the movement mechanism.

Any suitable vessel may be used, but optional embodiments use a monohull mothership and a catamaran boat such as the Alnmaritec aluminium 18m offshore crew boat. The cradle can optionally incorporate a trim control device adapted to reduce relative movement of the cradle and the boat, optionally as a result of heave when the boat is in the cradle. Optionally, the trim control device can be disposed in the base of the frame. Optionally the trim control device can comprise at least one aperture in the base of the frame adapted to permit passage of fluid through the base of the frame, thereby reducing resistance to vertical movement of the frame within the water. Optionally more than one aperture can be provided in the base of the frame. Optionally the number, dimensions and locations of the aperture(s) in the base of the frame can be designed in accordance with the dimensions of the cradle and the boat in order to tune as far as possible the motion of the frame to the motion of the cradle when subjected to water motion when in use. Optionally, the aperture is adjustable in order to increase or decrease the surface area of the aperture.

Optionally the base of the cradle can comprise more than one aperture. In certain examples, at least one of the apertures in the base is adjustable, although not all of the apertures in the base need to be adjustable in all examples, and in certain examples the base could comprise a number of fixed apertures, and a number of adjustable apertures.

In certain examples, the trim control device can be adjusted to match the motions of the cradle and the boat as far as possible. The adjustment can be made before installation on the mothership, where the type of boat to be handled with the apparatus is known and will not change, or can be optionally adjusted in use to trim the cradle with respect to the boat so that the two move together in response to water motion, e.g. wave movement. When the trim control features are adjusted to trim the cradle with respect to the boat, this can reduce the power demand on the movement mechanism. Similarly the weight distribution of the cradle can be used to trim it with respect to the boat to match the movement of the two components in the water and to reduce the power demands on the movement mechanism.

Optionally the trim control is provided by passive mechanisms (i.e. buoyancy and apertures in the cradle) while the boat is out of the cradle. Optionally the trim control is provided by both active and passive mechanisms when the boat is in the cradle, and particularly when the boat is engaged in the cradle, e.g. with the centre of gravity of the boat is approximately aligned with the centre of gravity of the cradle, and particularly in the phase of the procedure before the cradle is lifted. As the cradle is lifted by the movement mechanism and approaches the boat, the movement mechanism actively adjusts the position of the cradle to trim it to the boat's position in the water, based on feedback data from the position reference device. Thus the cradle is lifted while motion matching the cradle and the boat, thereby reducing the likelihood of severe collisions between the boat and the cradle. During this phase, particularly as the cradle base approaches the keel(s) of the boat, a water cushion is formed between the cradle and boat, improving the motion matching between the cradle and the boat. Once the boat and the cradle have come into contact, the active motion matching mechanisms are optionally reduced in power or switched off entirely, and the boat is raised out of the water by the movement mechanisms as quickly as possible.

Optionally, the pivot point coupling the cradle to the mothership can comprise a pivot link fixed to one end of the cradle, optionally the forward end of the cradle, and can optionally be coupled to the mothership by a vertically slidable mechanism, such as a carriage slidably engaged with a vertical bar mounted on the mothership. Optionally the pivot link can slide vertically relative to the mothership in use, and can the vertical sliding capacity can optionally be fixed relative to the mothership according to different sea states. Optionally, the pivot link can be connected to the cradle between the top and the bottom of the cradle. Optionally, the pivot link can be connected to the cradle below the top of the cradle, but above the midline of the cradle. Optionally, the pivot link can permit rotational movement around the vertical axis of the carriage. Optionally when the boat and the cradle are approaching a contact configuration during recovery operations, the winches are being driven actively using the position reference device data. When the boat and the cradle come into contact, the winches are optionally driven under constant tension to recover the boat from the water, and to reduce the gap between the boat and the cradle in the event of vertical displacement between the two. Optionally, the boat can be retained within the cradle by thrust generated by the boat relative to the cradle. In certain embodiments, the boat can be retained within the cradle by a latching mechanism which permits rotational motions of the boat relative to the cradle, i.e. yaw, roll and pitch motions around the vertical,

longitudinal and transverse axes of the boat respectively, and which optionally permits certain linear motions of the boat relative to the cradle, for example heave and sway motions along the vertical and transverse axes of the boat respectively, but which optionally restricts or prevents at least one linear motion of the boat relative to the cradle, for example surge motions along the longitudinal axis of the boat, and optionally restricts or prevents backward surge motions of the boat relative to the cradle when the latching mechanism is engaged. Optionally, the latching mechanism engages between the cradle and the boat at a position on the boat between the two ends of the boat. Optionally, the latching mechanism engages the boat at a position on the boat that is spaced from the bow of the boat.

Optionally, the latching mechanism engages between the cradle and the boat at or near to the centre of gravity of the boat. Optionally, the latching mechanism engages between the cradle and the boat at two locations on the boat which are spaced apart on opposing sides of the longitudinal axis of the boat. Optionally the spaced apart locations are equidistant from the centre of gravity of the boat. Optionally the two locations on the boat at which the latching mechanism engages between the cradle and the boat are aligned with a point on the longitudinal axis that is close to the centre of gravity of the boat. Optionally, the two locations on the boat at which the latching mechanism engages are disposed on or close to a transverse axis of the boat that passes close to or through the centre of gravity of the boat.

Optionally, the latching mechanism forms a pivotal attachment between the cradle and the boat, thereby allowing the rotational motions of the boat relative to the cradle. Optionally, the latching mechanism freely allows heave motions of the boat relative to the cradle, while restricting linear surge motions.

Optionally, the latching mechanism is engaged to couple the boat to the cradle after the boat has entered the cradle, and optionally after the centre of gravity of the boat is aligned with or is close to the centre of gravity of the cradle. Optionally the latching mechanism comprises a first pair of engagement devices such as arms on the cradle, and a second pair of engagement devices such as arms on the boat. Optionally the engagement devices on at least one of the boat and the cradle are selectively actuable from a first non-engaging configuration, in which the

engagement devices do not engage between the boat in the cradle, and a second engaging configuration, in which the engagement devices engage between the boat in the cradle to latch the boat within the cradle. Optionally, at least one of the pair of arms on the boat and the cradle are selectively actuable by moving pivotally from the first non-engaging configuration to the second engaging configuration.

Optionally, the pivotal movement of at least one of the pair of arms changes the angular orientation of one pair of arms relative to the other. Optionally, the pivotal movement of the at least one pair of arms is a movement through substantially 90°. Optionally, the pivotal movement of the at least one pair of arms through

substantially 90° is a movement in the horizontal plane, but could optionally be a movement in the vertical plane, relative to the other pair of arms. Optionally, the pair of arms on the boat are selectively actuable in this manner. Optionally, both pairs of arms can be selectively actuable if required, but in certain embodiments, only one pair of arms is selectively actuable.

Optionally the pair of arms on the boat are disposed at a different orientation from the pair of arms on the cradle when the arms are engaged in the second engaging configuration, and the latching mechanism is retaining the boat within the cradle. Optionally, the arms on the boat are perpendicular to the arms on the cradle in the engaging configuration. Optionally, the arms on the cradle are generally parallel to the plane of the side of the cradle in the first disengaged configuration, and are generally perpendicular to the plane of the side of the cradle in the second engaged configuration.

Optionally, a rear face of the arms on the boat engage a forward face of the arms on the cradle. Optionally the arms on the cradle are disposed behind the arms on the boat in the engaged configuration. Optionally, in the engaged configuration, the bow of the boat is restrained by a fender at the end of the cradle.

Optionally, the engaging faces of the engaging devices have friction reducing features. The friction reducing features can comprise a friction reducing surfaces, such as smooth bearing surfaces, optionally formed from a plastics materials.

Optionally, the engaging faces of the engaging devices can have friction reducing devices such as wheels, sliders, rollers etc. Optionally, the friction reducing devices can rotate and are rotationally constrained on rotational axes on the arms.

Optionally the rotational axes of the friction reducing devices on the boat arms are perpendicular to the rotational axes of the friction reducing devices on the cradle arms, at least in the engaged configuration of the latching mechanism. Optionally, the rotational axes of the friction reducing devices on the boat are vertical, optionally being aligned with the vertical axis of the boat, and optionally the rotational axes of the friction reducing devices on the cradle are horizontal, optionally being aligned with the transverse axis of the boat or of the cradle, and optionally being perpendicular to the plane of the side of the cradle, at least in the second engaged configuration of the latching mechanism. Rotational movement of the boat relative to the cradle, for example yaw, pitch and roll is permitted by the engagement between the cradle arms being disposed behind the boat arms, and allowing free rotational movement of the boat by virtue of the rotating friction reducing devices on the arms. Linear movement of the boat along the vertical axis of the boat, i.e. heave movement is permitted by vertical sliding of the arms. However, linear surge movement of the boat out of the cradle after the latching mechanism has been engaged is prevented or restricted by the inter- engagement of the arms.

Optionally, one or both of the arms on the boat and the cradle can be retractable, either linearly or pivo tally. Optionally, the selectively actuable arm in the latching mechanism can be moved by means of a hydraulic device, for example a hydraulic cylinder. The various aspects of the present invention can be practiced alone or in

combination with one or more of the other aspects, as will be appreciated by those skilled in the relevant arts. The various aspects of the invention can optionally be provided in combination with one or more of the optional features of the other aspects of the invention. Also, optional features described in relation to one aspect can be combined alone or together with other features in different aspects of the invention. Various aspects of the invention will now be described in detail with reference to the accompanying figures. Still other aspects, features, and advantages of the present invention are readily apparent from the entire description thereof, including the figures, which illustrates a number of exemplary aspects and implementations. Any subject matter described in the specification can be combined with any other subject matter in the specification to form a novel combination. The invention is also capable of other and different examples and aspects, and its several details can be modified in various respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive. Furthermore, the terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Language such as "including," "comprising," "having," "containing," or "involving," and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited, and is not intended to exclude other additives, components, integers or steps. Likewise, the term "comprising" is considered synonymous with the terms "including" or "containing" for applicable legal purposes.

Any discussion of documents, acts, materials, devices, articles and the like is included in the specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention.

In this disclosure, whenever a composition, an element or a group of elements is preceded with the transitional phrase "comprising", it is understood that we also contemplate the same composition, element or group of elements with transitional phrases "consisting essentially of", "consisting", "selected from the group of consisting of, "including", or "is" preceding the recitation of the composition, element or group of elements and vice versa.

All numerical values in this disclosure are understood as being modified by "about". All singular forms of elements, or any other components described herein are understood to include plural forms thereof and vice versa. References to directional and positional descriptions such as upper and lower and directions e.g. "up", "down" etc. are to be interpreted by a skilled reader in the context of the examples described and are not to be interpreted as limiting the invention to the literal interpretation of the term, but instead should be as understood by the skilled addressee. Brief Description of the Drawings

An embodiment of the present invention will now be described, by way of example only, and with reference to the accompanying figures in which:

Figure 1 is a side sectional view of apparatus for launching and recovering a boat from a mothership, showing a boat in a cradle and the hoist devices in the form of winches;

Figure 2 is a side sectional view similar to figure 1 showing the apparatus without a boat received within the cradle;

Figures 3 and 4 show sequential views similar to figure 2 showing the cradle tracking the water motion;

Figures 5-8 show sequential isometric views of the apparatus during a boat recovery operation; Figures 9, 11 and 13 show isometric views of three different possible alternative cradles for use in the apparatus in the above figures;

Figures 10, 12 and 14 show plan views of the cradles in figures 9, 11 and 14;

Figure 15 is a plan view of the mothership showing lateral restraints limiting the movement of the cradle;

Figure 16 shows a close up of a latching mechanism of the apparatus;

Figure 17 shows the hoist device in the form of a tensioning mechanism;

Figure 18 shows the linear measurement sensors in place with the tensioning mechanism;

Figure 19 shows a view of the LASER sensing device; and

Figure 20 shows two views of an example of fenders in the form of rollers on the base of the cradle.

Detailed description of certain examples of the invention

Referring now to the drawings, apparatus 10 for launching a boat B from a mothership M has a cradle 15, which optionally has a recess adapted to receive the boat B within the cradle 15. In this example the cradle 15 comprises a frame, with a general U-shape having a base 15b and side walls 15w, with the recess provided between the sidewalls 15w and above the base 15b for receiving the boat B between the sidewalls 15w and above the base 15b. The boat B is supported on the base 15b when the boat B has been recovered from the water (see fig 9).

The side walls 15 w of the frame of the cradle 15 can incorporate one or more buoyancy devices such as buoyancy tanks 17 which are optionally equally distributed on the cradle 15, and can be sealed and/or can have apertures to admit water and/or gas, to permit adjustment of the buoyancy by e.g. partial flooding during use or after commissioning to attain the optimum neutral position in still water to match the specific boat hull profile and displacement. The buoyancy tanks 17 can optionally be installed within the side walls 15w and may comprise solid buoyant material or buoyancy tanks. The size and disposition will be determined during tank and sea trials but will optionally comprise forward and aft tanks in each side wall 15w, or can be evenly distributed.

The cradle 15 is optionally received within a recess in the hull of the mothership M, which in this example is located at the stern of the mothership M, but which in other examples can be at different locations on the mothership M. The recess forms a dock for the cradle 15 to receive the boat B within the whole of the mothership M. Above the recess, the apparatus comprises a frame 20, configured to suspend the cradle 15 within the recess, to facilitate the handling of the cradle 15 and the boat B during launch and recovery operations.

The cradle 15 is coupled to the mothership M by a pivot coupling 30 at each side of the recess, allowing pivotal movement between the boat B and the mothership M about the pivot couplings 30, optionally in the vertical plane. The pivot couplings 30 optionally connect the forward portion of the cradle 15 to parts of the frame 20 extending into the recess at the sides of the recess.

The pivot couplings 30 optionally each comprise a carriage 31 (for example a collar) which at least partially surrounds or is otherwise engaged to a vertical bar 21. The carriages 31 are optionally slidable along the vertical bars 21 in the vertical plane. In certain examples (not in this case) the carriages 31 and the vertical bars 21 can optionally have circular cross sections, allowing rotational movement of the carriages around the axes of the bars, but in this example, the cross section of the carriages 31 and the vertical bars 21 are noncircular, thereby preventing relative rotation between the two components around the vertical axes of the bars 21. The pivot couplings 30 each have at least one link arm extending into the recess toward the cradle 15, and the link arms optionally have apertures to receive a pivot pin in a horizontal configuration, which is linked to at least one pivot lug formed in each side of the forward sections of the cradle 15. The pivot pins connect the cradle 15 through the pivot coupling 30 to the frame 20 on the mothership M. Optionally, the lugs on the forward section of the cradle 15 are disposed on the front face of each side wall 15w, and optionally each side wall has a separate pivot coupling 30 connecting to the frame 20 on the mothership M. Alternatively, the pivot coupling 30 can be connected to a different part of the mothership M. Optionally the lugs are disposed between the top and the bottom of the side wall 15w, optionally spaced some way below the top surface of the cradle 15, so that the pivot point of the cradle 15 is located between the midpoint of the side wall 15 w and the upper surface of the cradle 15.

Optionally the frame 20 supports a movement mechanism configured to move the cradle relative to the mothership M. The movement mechanism in the present example comprises at least one hoist device (4 in this example) which in this example take the form of winch devices 40 coupled to the lower side of the top beam of the frame 20, and having winch lines 41 connected between pulleys on the cradle 15 and the frame 20. The connection points on the cradle for the individual lines are spaced apart on different parts of the cradle, for example, near or at the corners of the cradle. In this example, the cradle 15 has at least one winch line 41 connecting each corner of the cradle 15 to the frame 20. The winches 40 are optionally arranged in pairs, one pair 40f at the front of the cradle 15 and one pair 40r at the rear. The winches in each pair 40f, 40r are operated in unison but each pair can be operated independently of the other pair, to raise or lower the front relative to the back of the cradle 15.

In some examples, the winch lines 41 are individually controlled to move different parts of the cradle relative to other parts. Optionally, each pair of winches can be driven by a separate motor, which can be independently controlled by the movement mechanism, but in this example, each winch 40 has a separate motor, and the winches in each pair are driven together by a controller in the movement mechanism. The winches 40 are optionally all constant tension winches and can be driven by an electric power supply (not shown). Other types of power supply can be used, e.g. hydraulic, pneumatic, etc.

The winches 40 are controlled from a controller in a control box 42 incorporating a processor and forming a part of the movement mechanism, optionally disposed on an upright beam of the frame 20, to raise and lower the cradle 15 within the recessed dock in the hull of the mothership M. As the cradle 15 is raised and lowered within the recessed dock, the pivot coupling 30 slides up and down the vertical bar 21, allowing free pivotal movement in the vertical plane between the cradle 15 and the mothership M.

The apparatus has a position reference device detecting the position of the cradle relative to the boat. The position reference device in one example takes the form of an acoustic transducer 50, and in this example, at least 4 acoustic transducers 50 are provided spaced apart on the upper surface of the base 15b of the cradle 15. A suitable acoustic transducer is available from Kongsberg Simrad. Other transducers (acoustic or otherwise) could be used instead. Optionally an accelerometer can be used in addition to or instead of the transducer 50. The acoustic transducers 50 are provided in front and rear pairs 50f, 50r which are spaced apart axially along the base of the cradle 15, and the transducers 50 in each pair 50f, 50r are optionally spaced apart laterally from one another on the base of the cradle 15. Each transducer 50 optionally contains an acoustic signal transmitter, and an acoustic signal receiver, optionally housed within a single sensor unit. The transducers 50 emit an acoustic signal upwards from the base of the cradle and receive a return from any physical item in the recess of the cradle. The time between the signal and the return is used by the processor in the control box to determine the distance between the transducer and the item in the recess. The acoustic transducers 50 are configured to detect the movement of the cradle relative to the boat in the cradle, as well as the position of the cradle relative to the boat. The transducers 50 measure the distance between the cradle and the boat in real-time, and report this data back to the control box 42, where it is optionally recorded and processed by the processor. The transducers 50 and the control box 42 can therefore also determine the dynamic rate of change of position between the cradle and the boat, and thereby measure and record the movement of the boat relative to the cradle 15, and by comparing movement data changes with time, the control box 42 can detect and record accelerations of the boat relative to the cradle 15 which is plotted as the rate of change of speed of movement of the boat and the cradle 15. The control box 42 optionally houses at the storage device such as a hard disk or flash memory adapted to record the position and movement data relating to the relative positions, movements and accelerations between the boat and the cradle 15, and may also have and display in order to display this measured data and processed information at the control box, or optionally on a display in the wheelhouse (or elsewhere) on the mothership M. The system can thus determine trajectories of the boat relative to the cradle using comparisons of previous data sets, for example it can determine that the boat is approaching the cradle by comparing sequential distance data measurements, and can determine whether impact is likely and when such impact is likely to occur, using the time stamped position data from the control box 42.

The transducers 50 optionally relay the data to the control box 42 over a wireless network, but may also be physically connected to the control box 42 by data lines embedded within the frame of the cradle 15, and optionally extending to the control box 42 via cables 53 which can optionally connect through sockets provided in the frame of the cradle 15 adjacent to the lugs on the frame forming part of the pivot connection 30.

In the present example, the control box 42 can be connected to the winches 40 over the same wireless network, or optionally through cables 43 embedded within, or attached to the surface of, the frame 20, thereby forming a transmission mechanism for transmitting the output data from the transducers 50 to the winches 40 via the control box, so that the movement mechanism controls the movement of the cradle 15 relative to the mothership M in response to the transmitted output data from the transducers 50.

The cradle 15 can incorporate a trim control device to reduce relative motion of the cradle and the boat as a result of heave when the boat is in the cradle, so that the cradle tracks the movement of the boat more accurately when subjected to the same heave and pitch forces exerted by the water motion within the recess. The trim control device can be in the form of one or more apertures 15a disposed in the base 15b of the frame of the cradle 15. The apertures 15a in the base 15b of the frame permit passage of fluid through the base 15b of the frame, thereby reducing resistance to vertical movement of the cradle 15 within the water. Optionally the apertures can be closed to increase resistance to vertical movement of the cradle 15 in the water. In certain examples, the base 15b of the cradle 15 has at least one variable aperture and optionally at least one fixed aperture. The variable aperture can simply be formed by a sliding panel formed in the base 15b, which can be slid back to reveal or close off the aperture and allow passage of fluid vertically through the base 15b which reduces drag and resistance to vertical movement of the cradle 15 within the water. In practice, the dimensions of the apertures in the base can be determined in advance to tune the hydrodynamic behaviour of the cradle in the water so that it is similar to the known behaviour of the boat to be received in the cradle 15. Although it is possible to change the cross-sectional area of the apertures and therefore the resistance to the vertical movement of the cradle 15 through the water, in practice a single cradle 15 is optionally used with the same design of boat, so the cross- sectional area of the aperture can be set initially during commissioning of the mothership or installation of the system, and then left at that setting until the cradle 15 is used with a different design of boat, which may have different hydrodynamic profile.

The cradle 15 can incorporate roller or fender devices around the inner surfaces of the frame of the cradle 15, to guide the boat into the cradle 15 and reduce friction during recovery and launching operations. Optionally the fender devices can comprise resilient devices, to have constant contact with the sides of the boat to avoid or reduce lateral movement of the boat in the cradle. The frame can comprise buoyancy tanks 17 in the form of hollow section members with internal bulkheads, creating separate compartments within the frame members (e.g. within the walls 15w). During installation, the tanks 17 in the walls can be filled or emptied to adjust the buoyancy.

The apparatus incorporates an optional latching mechanism, to restrain the boat B within the cradle 15 after the boat has entered the cradle. Optionally the latching mechanism is engaged when the centre of gravity of the boat B is aligned with or is close to the centre of gravity of the cradle 15. The boat B can thus be retained within the cradle 15 after thrust generated by the boat relative to the cradle has ceased, for example as the boat B is being lifted from the water. The latching mechanism permits rotational motions of the boat relative to the cradle, i.e. yaw, roll and pitch motions around the vertical, longitudinal and transverse axes of the boat respectively, and optionally permits certain linear motions of the boat relative to the cradle, for example heave and sway motions along the vertical and transverse axes of the boat respectively, but the latching mechanism restricts or prevents at least one linear motion of the boat relative to the cradle, and in this example, the latching mechanism is arranged to prevent or restrict surge motions along the longitudinal axis x-x of the boat, in particular backward surge motions of the boat B relative to the cradle 15 when the latching mechanism is engaged and the boat B is in the cradle 15.

The latching mechanism engages between the cradle 15 and the boat B at a position on the boat B between the two ends of the boat B, spaced from the bow of the boat B, and optionally at or near to the centre of gravity of the boat B. The latching mechanism engages between the cradle 15 and the boat B at two locations on the boat B which are spaced apart on opposing sides of the longitudinal axis x-x of the boat B, which are equidistant from the centre of gravity of the boat B, and which are optionally aligned with a point on the longitudinal axis x-x that is close to the centre of gravity of the boat. The latching mechanism 16 comprises a first pair of arms 16c attached to the cradle, and a second pair of arms 16b attached to the boat. The arms 16c are connected to the cradle 15 by a pivot connection allowing them to move from a first configuration into a second horizontal configuration around the pivot connection. The second pair of arms 16b attached to the boat B are optionally mounted as vertical posts, and do not require a pivot connection with the boat B, but could optionally incorporate one.

The arms 16 are selectively actuable from a first non-engaging configuration, in which the arms 16 do not engage between the boat in the cradle, and a second engaging configuration, in which the arms 16 engage between the boat in the cradle to latch the boat within the cradle. In the second engaging configuration, the arms 16c on the cradle are moved from the first folded non-engaging configuration in which the arms 16c are folded flat and parallel to the plane of the cradle sides (best shown in figure 2) to the second engaging configuration (best shown in figure 16) so that in the engaging configuration between the arms 16, the arms 16c are perpendicular to the arms 16b, and the arms 16c extend perpendicular to the plane of the cradle sides, to a position where the front faces of the arms 16c engage against the rear faces of the arms 16b. The arms 16c on the cradle 15 are moved from e.g. folded to the engaged configuration after the boat B has entered the cradle 15, and the vertical posts of the arms 16b have passed the pivot point on the arms 16c on the cradle 15, at which point, the bow of the boat B is driven against the inner end of the cradle 15 by the thrust of the engines of the boat B. After the arms 16c are moved from the folded to the engaged configuration, behind the vertical posts of the arms 16b on the boat B, the bow of the boat B is close to or abutting a fender F on the inner end of the cradle 15.

The rear faces of the arms 16b on the boat B engage the forward faces of the arms 16c on the cradle 15. In the present example, the engaging faces of the engaging devices have friction reducing features in the form of freely rotating wheels 18c, 18b which are rotationally constrained on rotational axes on the arms 16c, 16b.

Optionally the rotational axes of the wheels 18b on the boat arms 16b are perpendicular to the rotational axes of the wheels 18c on the cradle arms 16c when the latching mechanism is in the engaged configuration, with the cradle arms 16c actuated into the horizontal configuration. Thus the rotational axes of the friction wheels 18b on the boat B are vertical, aligned with the vertical axis of the boat, and the rotational axes of the wheels 18c on the cradle 15 are horizontal, aligned with the transverse axis y-y of the cradle.

In this example, the wheels 18 are provided with a degree of inherent resilience, as in this example they are manufactured from a resilient plastics material, so that as the arms 16 engage any shock forces are absorbed by the resilient material of the wheels 18, and are not transferred to the boat B or to the cradle 15. Rotational movement of the boat B relative to the cradle 15, for example yaw, pitch and roll is permitted by the engagement between the cradle arms 16c being actuated in the horizontal configuration behind the boat arms 16b, and allowing free rotational movements of the boat B relative to the cradle 15 by virtue of the rotating wheels 18 on the latching mechanism 16. Linear movement of the boat B along the vertical axis z-z of the boat B, i.e. heave movement is permitted by vertical sliding of the rear face of the arms 16b up the forward face of the arms 16c. However, linear surge movement of the boat B out of the cradle 15 after the latching mechanism has been engaged is prevented or restricted by the inter-engagement of the perpendicular arms 16b,c. In the present example, the wheels on the arms allow sway of the boat B within the cradle 15 within the constraints of the width of the cradle 15.

Accordingly, the boat B is relatively unconstrained within the cradle 15, at least with respect to rotational movement of the boat B. This allows the boat B to freely pitch, roll and yaw around the 3 main axes of the boat B, relative to the cradle, and relative to the mothership M, but the freedom of the boat B to move along the linear axes is limited in respect of the horizontal axis, so surge movement of the boat B along the horizontal axis is prevented by the latching mechanism 16 which limits rearward surge of the boat B, and by the bow of the boat B pressing against the inner end of the cradle 15, which prevents forward surges of the boat B. In certain examples, the boat B can surge forward and aft within the cradle to a relatively small extent, so that the bow of the boat B is not kept pressed against the fender F when the cradle 15 is being raised. The wheels 18 on the latching mechanism 16 do allow vertical linear heaving of the boat B relative to the cradle 15. The limited freedom of the boat B for movement relative to the cradle 15 and relative to the mothership M allows the boat B to naturally react against the arms due to the forward motion of the mothership M. The boat B is kept from "falling" backwards from the cradle 15 during the cradle raising phase but is otherwise unconstrained. Optionally the recovery operation is performed when the mothership is moving forward. Providing the boat arms 16b just forward of the deck house on the port and starboard sides of the boat sets the rotational centre of the boat B after engagement of the latching mechanism at or close to the centre of gravity of the boat B. It is not essential for the latching mechanism to engage at the exact centre of gravity of the boat B, but if the boat arms 16b are close to the centre of gravity of the boat, the rotational movements of the boat B within the cradle 15 will be more consistent, so matching the position of the arms 16b on the boat B to the centre of gravity of the boat is one optional advantage. The vertical arms 16b on the boat B allow the boat B to sway and yaw while the horizontal retractable arms 16c on the cradle 15 allow the boat B to roll and heave.

The arrangement helps to avoid the need for near waterline attachments between the boat B and the cradle 15, and clears the foredeck area of the boat B for transfer of personnel. The latching mechanism is inherently simple with no complex mechanisms that could jam or prove difficult to maintain, and allows a measure of redundancy as either arm on either side of the boat B would be capable of providing the necessary latching.

Optionally, the arms 16 can incorporate sensors in the form of simple proximity devices in order to allow remote confirmation of inter-engagement of the latching mechanism to prevent the cradle being raised until the boat B is safely latched. In use, with reference to figs 5-8, the boat B is received within the submerged cradle 15 within the recess of the hull of the mothership M. The winch lines 41 have been paid out under the control of the control box 42, so that the base 15b of the cradle 15 is submerged well below the bottom of the keel of the boat B, in the configuration shown in fig 1. The winches 40 are not exerting any significant tension but are optionally idling and maintaining constant tension without actively moving the cradle up towards the frame. The pivot couplings 30 have slid down the bars 21, and the cradle 15 is free to pivot in the vertical plane around the pivot axes defined by the pivot couplings 30. The buoyancy tanks 17 within the frame of the cradle 15 are at least partially flooded, but some buoyancy remains within the cradle 15, so that the upper parts of the sidewalls 15w of the cradle 15 emerge above the surface of the water within the recess, partially under the force of the buoyancy, and partially under the force of the winches. Optionally, the buoyancy remaining within the cradle 15 can be fixed, and can be sufficient to encourage partial tracking of the cradle 15 in accordance with water motion within the recess. Because of the pivot couplings 30, the movement of the cradle 15 within the recess is limited to pitching (rotation) and heaving (vertical displacement) movement in the plane of the pivot pins through the couplings 30, and the cradle 15 is substantially restricted from moving laterally within the recess, and from rolling from side to side within the recess. Optionally the aft end of the cradle can have lateral restraints 70 (see Fig 15) such as a roller which can optionally be resiliently biased inwardly into the recess of the mothership M to reduce or eliminate the tendency of the cradle 15 to move laterally within the recess. At this stage, when the boat B is out of the cradle 15, the motion matching between the cradle 15 and the boat B is passive i.e. arising from adjustment of buoyancy and apertures in the cradle, generally trimmed before commission to synchronise with the boat. As the boat B enters the mouth of the cradle 15, the vertical rollers at the mouth of the cradle 15 guide the boat B into the cradle 15 and space it laterally from the sidewalls 15w of the frame. At this point, the arms 16b on the boat B have not yet passed the arms 16c on the cradle 15, which are still in the disengaged

configuration, with their axes parallel to the face of the side of the cradle 15. At this point, the keel of the boat B clears the upper surface of the base 15b of the cradle by a suitable distance, for example approximately 50 cm, depending on the draft of the boat. When the bow of the boat B has reached the forward end of the cradle 15, it can be tied or otherwise secured to the stanchions emerging from the upper surface of the sidewalls 15w of the cradle 15. The boat B is optionally restrained against rolling movement relative to the cradle, by the sidewalls 15w of the frame and the fenders F.

The arms 16b on the boat B move past the arms 16c on the cradle 15 just at the point when the bow of the boat B presses against the inner end of the cradle 15. Optionally, there is a short clearance between the bow of the boat B and the fender at the inner end of the cradle 15. At this point, the arms 16c on the cradle 15 are actuated from their initial disengaged configuration parallel to the face of the side of the cradle 15, to the second horizontal engaged configuration perpendicular to the face of the side of the cradle 15, so that the forward faces on the horizontal arms 16c of the cradle 15 engage behind the rear faces of the vertical arms 16b on the boat B. The resilient wheels 18c on the horizontal arms 16c freely rotate to allow roll and heave movements. The resilient wheels 18b on the vertical arms 16b on the boat B freely rotate to allow sway and yaw movements of the boat B. In this example, the arms 16c on the cradle 15 are moved between the disengaged and the engaged configurations by hydraulic cylinders 19, but other deployment mechanisms can be provided.

When the boat B is fully received within the cradle 15, with the arms 16c in the horizontal engaged configuration, the buoyancy in the cradle can optionally be adjusted by injecting gas (for example compressed air) into the adjustable tanks within the frame of the cradle. Compressed air can be injected through an air line 44 connecting a supply of compressed air (for example a cylinder disposed on the deck of the mothership M) with the variable buoyancy tanks within the frame of the cradle. This can be done under the control of the control box 42. Alternatively the buoyancy can be determined during trials and can be set by using enclosed tanks or rigid buoyancy material. Alternatively, the position of the cradle 15 within the recess can be adjusted by means of the winches 40. In some examples, without buoyancy, the winches 40 can provide the sole mechanism to raise and lower the cradle 15 within the recess.

Using either or both of the variable buoyancy or the winches 40, the vertical position of the cradle is adjusted under the control of the control box 42 to raise the cradle relative to the floating boat B until the upper surface of the base 15b of the cradle 15 is approaching the lower surface of the keel of the boat B. During this process, the wheels 18c on the horizontal arms 16c freely rotate so that the cradle 15 moves passively relative to the boat B.

The displacement between the upper surface of the base 15b of the cradle 15 and the under surface of the keel is measured by the transducers 50 and the details relayed to the control box 42, where it is processed for each transducer, and the winch motors for the winches 40 are individually controlled between the front pair of winches 40f and the rear pair of winches 40r in order to maintain the attitude of the cradle 15 parallel to the keel of the boat B as much as possible, so that as the boat B pitches and heaves within the recess in response to water motion as shown in figures 3 and 4, the cradle 15 is moved by the winches 40 in the same way, thereby keeping the base 15b of the cradle generally parallel to the keel of the boat B as the cradle 15 is gradually raised up by the winches 40 towards the frame 20. The dynamic positioning of the cradle relative to the boat by virtue of the transducers 50, control box 42 and winches 40 ensures that when the boat B makes initial contact with the cradle 15, it does so in a generally parallel configuration and any impacts between the boat B and the cradle 15 are spread over a generally large area on the cradle 15 and on the boat B, thereby reducing the risks of collision damage to both components.

Thus, when the boat B is in the cradle 15, and the base of the cradle 15 is approaching the keel of the boat B, the motion matching is both active and passive . As the cradle 15 is lifted by the movement mechanism and approaches the boat B, the movement mechanism actively adjusts the position of the cradle 15 to trim it to the boat's position in the water, based on feedback data from the position reference device. Thus the cradle 15 is lifted while motion matching the cradle 15 and the boat B, thereby reducing the likelihood of severe collisions between the boat B and the cradle 15. During this phase, particularly as the cradle base approaches the keel(s) of the boat B, a water cushion is formed between the cradle 15 and boat B, improving the motion matching between the cradle 15 and the boat B. In the event that the boat B pitches suddenly within the recess so that the bow moves closer to the cradle, the sudden movement of the bow of the boat B will be detected by the front transducers 5 Of, and optionally the difference in clearance between the front pair 50f and the rear pair 50r will also be separately detected before a collision event occurs between the boat B and the cradle 15. The sudden movement detected at the front transducers 50f and the discrepancy between the clearance between front and rear transducers 50f, 50r is transmitted to the control box 42 and processed in real-time as soon as it is detected by the transducers 50. The control box interprets the data as being representative of a sudden forward pitch of the boat B relative to the cradle 15, and reacts instantly by paying out the front winches 40f (or reducing their rate of winding in) in order to realign the cradle 15 with the boat B in a generally parallel configuration, thereby reducing the risks of collision events between the bow of the boat and the base of the cradle 15.

In a similar manner, in the event that the boat B pitches in the opposite direction so that the stern moves closer to the cradle, the sudden movement will be detected by the transducers 50, and optionally the difference in clearance between the front pair 50f and the rear pair 50r will also be detected before a collision event occurs. The sudden movement detected at the rear transducers 50r and the discrepancy between the clearance between front and rear transducers 50f, 50r is transmitted to the control box 42 and processed in real-time as soon as it is detected by the transducers 50. The control box interprets the data as being representative of a backward pitch of the boat B relative to the cradle 15, and reacts by paying out the rear winches 40r in order to realign the cradle 15 with the boat B in a generally parallel configuration, thereby reducing the risks of collision events between the stern of the boat and the base of the cradle 15. When the pitching stops the winches resume their winding in under the control of the control box 42.

Pitching movement of the boat B relative to the cradle 15 result in the boat B pivoting around the arms 16b,c of the latching mechanism 16, as the wheels 18c freely rotate.

Accordingly, the movement mechanism comprising the winches 40 under the control of the control box 42 reacts to data supplied by the transducers 50 in order to control the movement of the cradle 15 so as to maintain a relatively constant geometric relationship between the cradle 15 and the boat B as the cradle 15 is being raised in order to recover the boat B from the water.

After the cradle 15 has come into contact with the boat B, the winches 40 are operated in a similar manner to raise the cradle 15 and the boat B from the position shown in figure 6 to the position shown in figure 7. In that state, the boat B is optionally not subjected to any significant accelerations due to the waves, and as the boat B approaches this position, generally less and less intervention from the control box 42 and winches 40 is required in order to maintain the steady parallel geometric relationship between the cradle 15 and the boat B. Once fully recovered from the water and in the position shown in figure 9, the boat B can be removed from the cradle onto a set of rollers for further handling as desired, thereby freeing the cradle 15 to recover another boat B. The latching mechanism 16 remains engaged with the arms 16b,c remaining relatively perpendicular thereby retaining the boat B within the cradle 15 as they are lifted out of the water. Once the boat B has moved forward out of the cradle 15 and onto the deck of the mothership M, the horizontal arms 16c are moved back to their vertical disengaged positions for recovery of another boat B within the cradle 15. Once the boat B and the cradle 15 have come into contact, the active motion matching mechanisms are optionally reduced in power or switched off entirely, and the boat B is raised out of the water by the movement mechanisms as quickly as possible. Optionally, the movement mechanism can also comprise an arresting mechanism comprising a ratchet or braking mechanism, arresting or restricting movement in the opposite direction of travel, which allows the example to utilise the natural lifting motion of the waves under the cradle 15, so that if a large wave lifts the cradle 15, the line is reeled in and the position maintained. The arresting mechanism can of course be adopted in other examples with different movement mechanisms.

Conversely, when the boat B is being launched, the same operation is performed in reverse order, and as the boat B is entering the water, the movement of the cradle 15 is controlled in a similar manner to move the cradle 15 so that it maintains a generally steady geometric relationship with the boat B as the boat becomes more and more subjected to accelerations as a result of wave motion. Optionally the buoyancy of the cradle can be adjusted at this point to increase the tendency of the cradle to sink away from the boat at the point of launch. During launch, the latching mechanism 16 is engaged until the cradle 15 has moved safely away from the boat B, and the boat B is floating freely in the water, at which point the latching mechanism is disengaged to allow the boat B to move out of the submerged cradle 15. Optionally, the disengaged configuration of the arms on the cradle 15 could be a vertical configuration, where the arms and the cradle were parallel to the arms on the boat, and parallel to the plane of the sides of the cradle. It is sufficient that the arms somehow move from a non-engaging configuration, in which they do not interfere with the freedom of movement of the boat relative to the cradle, to an engaging configuration, in which the inter-engagement of the arms limits the freedom of movement of the boat relative to the cradle. With reference to Figs 9-14, alternative designs of cradle are possible. The alternative designs of cradle shown in figs 9-14 share certain features with the cradle 15 and these features will not be described again for brevity, but the reader is directed to the earlier description in relation to these features. The modifications described in Figs 9-14 can be used with any of the other examples described herein.

The example of the cradle 12 shown in Figs 9 and 10 has a frame with a general U- shape having a base 12b and side walls 12w, and a recess between the sidewalls 12w and above the base 12b for receiving the boat B as previously described, with apertures 12a. In the cradle 12, the side walls 12w incorporate buoyancy devices in the form of tanks 17 which are equally distributed along substantially the entire length of the walls 12 w. Optionally, the side wall 12 w can incorporate a single tank which can optionally extend for substantially the whole height and length of the wall 12w. However, in this example, the tanks 17 are vertically and optionally

horizontally divided into separate compartments, and need not extend vertically for the full height and/or length of the whole wall 12w. The tanks 17 can be sealed and/or can have apertures to admit water and/or gas, to permit adjustment of the buoyancy by e.g. partial flooding during use or after commissioning to attain the optimum neutral position in still water to match the specific boat hull profile, displacement, and trim. The buoyancy tanks 17 may comprise solid buoyant material or buoyancy tanks. Generally, the arrangement of tanks 17 in the cradle 12 is similar to the arrangement of tanks in the cradle 15.

The cradle 12 differs from the cradle 15 principally in the arrangement of the base 12b. In the cradle 12, the base 12 has a pair of trim control apertures 60 extending along the length of the cradle 15, which are at least partially filled by trim control plates 61 and 62. At least one of the trim control plates 61, 62 is optionally slidable within the aperture 60 relative to the other, and in this example, the first plate 61 is optionally fixed within the aperture 60, and the second plate 62 is optionally slidable relative to the aperture 60 and to the first plate 61. Slidably mounting the plate 62 within the aperture allows adjustment of the cross-sectional area of the aperture 60. In certain circumstances, the aperture 60 can be left entirely free from plates, to allow the maximum cross-sectional area in the aperture 60, and permit the maximum amount of fluid flow vertically through the base 12b through apertures 12a, with the minimum of resistance. That arrangement could be used for designs of boat with a very shallow drafts, and a tendency to react to wave motion by excessive pitching and heaving, because it permits the cradle 12 to move rapidly in response to the movement mechanism with the minimum of time lag as a result of

hydrodynamic resistance to movement of the base 12b through the water. However, in this example, the cradle 12 has blanking plates 61 and 62 installed within the aperture 60 and arranged to blank off a selected amount of the surface area of the aperture 60. The plate 62 has been slid longitudinally within the aperture 60 to partially underlie the plate 61, and to modify the surface area of the aperture available for passage of fluid through the base 12b, as the cradle 12 moves through the water. The blanking plates 61, 62 can optionally be adjusted prior to use, for example at commissioning, and left in the same configuration, or can be adjusted in use as desired.

The cradle 13 shown in figures 11 and 12 is similar to the cradle 12 in terms of the sidewalls 13w. The base 13b of the cradle 13 is again different, and incorporates no trim control features, but is simply a flat frame to support the boat within the cradle 13, with apertures 13a.

The cradle 14 shown in figures 13 and 14 differs in respect of the sidewalls 14w, which incorporate buoyancy tanks 17 only at the ends of the walls 14w, and have frame sections with apertures between the buoyancy tanks 17 at respective ends of the cradle 14. The base 14b has apertures la as previously described. Optionally, in the cradle 14, the latching mechanism can be omitted.

In other respects, the cradles 12, 13, 14 have acoustic transducers 50r, 50f which function in a similar way as previously described in relation to the cradle 15. Features of the different cradles 12, 13, 14 and 15 can be combined with one another freely and optional features used in one of the cradles can be used in other cradles in different examples of the invention. Optionally when the boat and the cradle are approaching a contact configuration during recovery operations, the winches 40 are being driven actively using the data from the transducers 50. When the boat B and the cradle 15 come into contact, the winches 40 are optionally driven under constant tension rather than using the data from the transducers to recover the boat from the water as quickly as possible. In the event that a wave unexpectedly lifts the boat up from the cradle, the winch motors operating at constant tension automatically speed up when they detect the reduction in tension arising from the displacement of the boat B away from the cradle 15, and this helps to close the gap between the boat B and the cradle 15 in the event of vertical displacement between the two. Optionally, the winches 40 are switched to operate at constant tension under the control of the control box 42, and this transition can optionally be triggered at a predetermined distance between the boat B and cradle 15, detected by the transducers in the normal way.

Figure 17 shows another modification that can be used with any of the above- described examples of the invention. The modification of this example pertains to the hoist devices, and other aspects of this example are as described in earlier sections, so will not be repeated here for the interests of brevity. In this

modification, the hoist devices are in the form of tensioning mechanisms 80 affixed to the frame 20 at spaced apart locations, for example, at or near corners of the cradle. The tensioning mechanism 80 comprises at least one fixed sheave block 80f attached to the frame 20, and at least one travelling sheave block 80t, which is movable relative to the fixed block 80f. Lines 81 are fixed at one end to the frame 20 before being reeved through the sheaves in the sheave blocks 80f and 80t. The lines 81 are further reeved through a sheave block, itself fixed to the frame 20, acting as a pulley. The lines 81 are fixed to pivot points 80p at or near each corner of the cradle 15. The sheave blocks 80f,80t are vertically spaced from one another in the frame of the tensioning mechanism 80 and are aligned along an axis of an upright column of the frame 20, which is generally perpendicular to the axis of the mothership M. The sheaves within the blocks 80f, 80t are mounted on horizontal axles about which they can rotate. In this example, the fixed sheave block 80f is mounted axially above the travelling sheave block 80t relative to the upright column of the tensioning mechanism 80. The travelling block 80t is moved, relative to the fixed block 80f, by retraction and extension of a hydraulic ram 80h. In the illustrated example, this mechanism provides a ratio of movement of approximately 3:1 of the cradle 15 with respect to the travelling block 80t; different numbers and diameters of sheaves in the tensioning mechanisms 80 will lead to different ratios of movement and are within the scope of other examples. This means that a small amount of retraction or extension of the hydraulic ram 80h leads to a comparably large length of line 81 reeled in or out, and a correspondingly large lift or drop of the cradle 15 relative to the frame 20. The small amount of movement required to achieve a large lift of the cradle 15 also means that the cradle 15 can be relatively rapidly lifted, and the position maintained. The other features of the apparatus can be selected from any of the other examples described herein.

According to one optional feature in this example, the apparatus can also comprise an arresting mechanism comprising a ratchet or braking mechanism, arresting or restricting movement in the opposite direction of travel, which allows the example to utilise the natural lifting motion of the waves under the cradle 15, so that if a large wave lifts the cradle 15, the line is reeled in and the position maintained. The arresting mechanism can of course be adopted in other examples with different movement mechanisms.

Figure 18 shows the tensioning mechanisms 80 in situ with linear measurement sensors 90 positioned fore and aft on the frame 20. The linear measurement sensors 90c are attached to the cradle, and comprise a cable held in substantially constant tension between the cradle 15 and the frame 20. When the cradle 15 approaches the frame 20, the cable is reeled in under constant tension, and the cable is reeled out as the cradle is lowered. The sensors passively detect the position of the cradle 15 relative to the frame 20 by measuring the amount of line recovered and spooled out, and the measured data is transmitted to the movement mechanism. Here the linear measurement sensors are shown attached to one side of the cradle 15, but they can optionally be attached to both sides, and it is beneficial for a pair of linear measurement sensors 0 to be connected fore and aft of the cradle 15. The linear measurement sensors 0 can be used with any example described herein, and are not limited to the example disclosed.

Linear measurement sensors 90b are manually attached to the boat B once it has entered the cradle 15, for example, by fixing onto the boat B by a releasable catch. Lanyards can optionally be provided trailing from the catches which can be manually pulled down into the required position by a deck hand. Similarly to the cradle sensors 90c, the boat sensors 90b attached to the boat B passively reel in the cable when the boat B is lifted, and reel out the cable when the boat B is lowered, and the data is transmitted to the movement mechanism as described in other examples. This data can be compared by the control system in the control box 42 of the movement mechanism to accurately calculate the relative positions of the cradle 15 and the boat B, as the attachment positions of each cable of the linear

measurement sensors 90 is known. Figure 19 shows the tensioning mechanisms 80, linear measurement sensors 90b, and optional LASER scanners 100. The optional LASER scanners 100 are mounted on the frame 20 above the cradle 15 such that the beam from the scanners 100 travels from the frame 20 towards the cradle 15, and optionally act to track specific targets positioned on the cradle 15 and the boat B. Alternatively, the scanners 100 need not be directed at particular targets on the boat B or cradle 15, and can simply detect the overall structure beneath them. By calculating the difference in the measured distances between the boat B at the cradle 15, optionally by using the targets on each, the scanners 100 can determine the relative positions of the cradle 15 and boat B as described by other examples herein. By constantly scanning the targets, the scanners 100 can provide real-time position data that can be used by the control system in the control box 42 of the movement mechanism. Additionally the scans can be used to create 3D visualisations of the relative positions of the boat B and the cradle 15 to inform the hoist device operator. The LASER scanners 100 can be used with any example described herein.

In a further example of an optional modification useful with any of the foregoing examples, Figure 20 shows a modified cradle 15 with rollers llOr rotationally mounted on arms 110a that are pivotally mounted on pivot points llOp on the cradle base 15b, and which are articulated around the pivot point llOp to raise and lower the rollers llOr in an arc around the pivot point llOp relative to the base 15b. Optionally the rollers llOr on the base 15b can be moved into a raised configuration around the pivot point llOp by a hydraulic cylinder llOh when the cradle 15 is being lifted, and can be maintained in the raised position by the hydraulic cylinder llOh. The hydraulic cylinder llOh can optionally incorporate a gas spring to resiliently bias the arms 110a into the extended raised position, so that when the keel of the boat B engages the raised arms 110a, the arms 110a and rollers llOr provide a soft landing for the boat B as it contacts the cradle 15 during the lifting process. Optionally the spring is collapsed gently by the weight of the boat B as the cradle 15 is raised out of the water. This optional modification reduces the impact damage between the boat B and the cradle 15 during lifting procedures. During launch procedures, the hydraulic cylinders 11 Oh can be operated to lower the arms 110a and move the rollers llOr away from the keel of the boat B, to facilitate launching. The modification can be used with any example described herein.