COVER, ELEMENT AND STRETCH CARENE TOW PACKAGE

The present invention relates to tractors faired cables used on a ship to tow a submersible body dumped at sea and the handling of these cables. It relates more particularly cables tractor careened through scales or sections hinged together. It also applies to any type of elongated member ducted to be at least partially immersed.

The context of the invention is that of a naval vessel or vessel to tow a submersible object such as an integrated variable depth sonar in the towed body. In this context, non-operational phase of the submersible body is stored on board the ship and the cable is wound around the drum of a winch for winding and unwinding the cable, that is to say to deploy and retrieve the cable. Conversely in the operational phase, the submersible body is immersed behind the ship and towed by the latter by means of the cable, the end connected to the submersible body is immersed. The cable is wound / unwound by the winch through a cable guide device for guiding the cable.

To obtain a high immersion important tow speeds, the tow rope is streamlined thereby reduce the hydrodynamic drag and vibrations generated by the hydrodynamic flow around the cable. The cable is coated with a segmented shroud composed of rigid hull having shapes to reduce the hydrodynamic drag of the cable. The role of the sheath formed by the hulls is to reduce the wake turbulence produced by the movement of the cable in the water, when it is immersed in the water and towed by the ship. The stiffness of the hull is required for large dips in tandem with large towing speeds of at least 20 knots. Flexible fairings are interesting only for economically profile chains or buoys cables subject to ocean currents or at worst towed to from 6 to 8 knots speed. In the case of the use of rigid fairing elements, segmentation fairing keels is necessary for the cable can pass through the guide elements of the pulley type and

so as to withstand a lateral deviation of the cable in case of ship's heading change and so as to be wound on the drum of a winch.

In normal operating condition, the hulls are rotatably mounted about the longitudinal axis of the cable. It is indeed necessary that the hulls can rotate freely around the cable to be properly oriented with respect to the flow of water. Each hull is however linked to its two neighboring axially and rotationally around the cable so as to be pivotable relative thereto about an axis parallel to the axis x of a small maximum angle of the order of a few degrees. This link allows inter hulls especially the fairing assembly can move smoothly in all the guiding elements. As a result, the rotation of a hull causes rotation of its neighbors and by degrees that of all keels. Therefore, both when the cable is deployed in the water when it is wrapped around the drum while changing the orientation of one of the keel, affects step by step all the hulls careening cable. Thus, when the cable is deployed at sea the hull is naturally oriented in the direction of the current generated by the building movement. Similarly, the guide device is conventionally configured to orient and guide the keel of which pass through the way that they have a predetermined orientation with respect to the winch drum, all the hulls adopt over of lift cable same orientation relative to the drum, an orientation that allows to wind the cable maintaining the parallel scales the one to the other alternately.

The Applicant has found that, when coming wind the cable around the ducted drum of a winch in order to recover the towed body, it occasionally happens that the fairing is highly deteriorated see crushed at the time of its passage through the devices guide, which can make unavailable all the sonar system. It may even happen that this deteriorates the guide device. For example, some systems of variable depth sonars installed on some ships and operated as normal by military crews encounter hulls grinding problems about once a year and sometimes more often. This grinding may have limited consequences but can also escalate,

block the winch or damage and thus lead to the unavailability of any towing system and consequently of the sonar.

An object of the present invention is to limit the risks fairing deterioration of towed cable.

To this end, the applicant first of all, in the context of the present invention, identified and studied the cause of the hull grinding problem by watching cable shrouded in operational status and by modeling the cable streamlined operational situation different forces acting on it, including hydrodynamic and aerodynamic flow as well as gravity.

During the operational phase, the ducted cable is towed by the vessel and has an immersion end. Very often, the towing point is a point on a pulley that is located at a height above the water. Tow point of a cable or a fairing, is meant the position of the fulcrum of the cable to an onboard device on board the ship, which is the closest to the immersed end of the cable or the shroud respectively . When the ship ahead, under the action of the drag, the cable away from the transom to disappear under the water a little further than the vertical towing point. The cable length shrouded in air situation is increased compared to the single towing height above water because the cable is inclined relative to the vertical. It is observed that the last hull which is still in engagement with the vessel, that is to say the hull which is towing point, often supported on the pulley or supported on a guide device on board the vessel , is oriented correctly in the direction of flow although it is well above in air (leading edge facing the flow and the trailing edge behind. the first hull in the water (i.e. -to say just the submerged hull) is supposed to make a correct orientation in the flow from vessel speed (leading edge facing the flow and trailing edge trolling). But between these two remarkable hulls, column fairing may twist as it is in the air, just vibrated, an insignificant airflow and gravity. As a result of requests from the sea, towing conditions and waves, torsion situations of this air column are regularly observed. The first cau if torsion is caused by gravity as soon as the cable is moved away from the

vertical, which necessarily happens to him as soon as the towing speed is sufficient. Under the effect of gravity, the fairing column between the towing point and the sea will twist to one side (in air) and will recover (in water). This is the nominal position of the fairing column. This twisting is a function of the intrinsic stiffness of the column shroud but also air length. A situation in which the aerial part of the fairing 2 is slightly twisted, that is to say in torsion about the axis of the cable is shown in Figure 1 A. In Figure 1A, the vertical direction in the terrestrial frame of reference is represented by the z axis and shows the orientation of the section of certain keels in zones a, B and C enclosed by dashed lines. In the situation shown in Figure 1 A, the last hull 3 in engagement with the vessel is vertically oriented (trailing edge up) as is shown in zone A. The hulls that are in the air between the pulley P and the water surface S are laid under the effect of gravity. In other words, as shown in the area B, the trailing edge of the keel is oriented downwardly (between the pulley P and the surface S of the water, hulls revolved around the cable). However, hulls which lie in the water are adjusted under the action of the flow of water acting as the FO arrow as shown in the area C (trailing edge and leading located at approximately the same depth).

It happens from time to time, according to the sea conditions, water packets or breaking waves fall down more or less towards the transom of the vessel by creating then in the aerial part of the cable a momentary reverse flow of the prevailing low and matches the speed of the vessel forward. These bodies are fully capable of further twisting of the shroud advantage column and place it in opposition to the intended position in the normal flow of tow. In this case, the shroud is twisted and carries, in its aerial part, a half-turn around the cable. This means that two hulls of the aerial part of the fairing column have trailing edges forming between them an angle of 180 degrees around the cable. The portion of the fairing located between these two surfaces is twisted or torsionally. From this, it can happen that these parts of fairings are therefore upside down from the average flow given by the ship's speed, are then

suddenly bathed again in this way flows (due to ship motion, that of Vaques etc.) the fairing part upside is asked to come back in the right direction (related to normal medium flow). It can then:

- annul its turn and return to its initial position by describing the reverse rotation of that which had brought backwards. It is then correctly oriented.

- or add to the existing turn another half turn which bring it to the correct orientation in the flow but which has the effect of twist of 1 turn (or 360 °) the aerial part of the fairing above it and twisting in the same way a portion below it of a turn (or 360 ° but this time in the other direction). The party was initially upside returned to the positive trend in the average flow from vessel speed but it is produced two twists of a turn one over in the air and other below in water. One speaks of complete twist of the shroud (which may be translated by twist in English terminology). This complete twist is a stable position of the column shroud or fairing 2. It is shown in Figure 1 B. This situation can be described as follows: R between the towing point and the water surface S , the fairing column completes one revolution in the direction of the arrow F1 around the cable. The fairing of column 2 passes through the surface S and remains properly oriented over a length L of the order of a few meters or less sometimes. Then the fairing column 2 performs one complete turn in the water, in opposite direction, represented by arrow F2 back to the correct orientation in the stream. In other words, the shroud undergoes a complete double twisting around the cable. The double torsion comprises an aerial complete twist, located above the water surface and submerged one complete twist, located below the water surface. All that portion of the fairing located below this double full twist is not at all affected by what happens over her (its hulls are correctly oriented in the flow).

The configuration in which the fairing undergoes a double torsion is stable but strongly degraded and it might greatly to bring subsequently large disturbances on the overall system.

We have discovered that when a fairing undergoes a double full twist, under certain conditions, the fairing will be greatly deteriorated in the water and the damaged part will cause great damage to the cable keeled or even all of the ducted system during winding of the cable more precisely when it passes through the cable guide device.

By analyzing the double full twist, the applicant has found that the submerged twist can be seen as "hooked" on the cable. In other words, the torsion immersed position is fixed relative to the cable along the cable axis. However, its air exchange, the air twist remains in the same location between the towing point R and the water surface S. It is not fixed relative to the cable as the cable axis but fixed relative to the surface S of the water or at the towing point. When the cable is hoisted or lowered, the hulls immersed undergoing torsion follow the movement of the cable which is raised or lowered while the air twist remains fixed relative to the surface of the water. It follows that unwinding of the cable plunged torsion immersed to a greater depth so that the air twist remains in the same place relative to the water surface (2 twists then away the from each other). Figure 1 C illustrates a situation in which the cable has been unwound with respect to the situation of Figure 1 B (see arrow). The distance L2 represents the distance between the relevant part of the fairing by the submerged torsion and the fairing in the water entry point is greater than the distance L1 representing the same distance in the situation of Figure 1 B. At opposite a hoisting cable, with respect to the situation of Figure 1 B, according to the arrow shown in Figure 1 D, traces submerged torsion while air torsion remains in the same place relative to the surface water (both twists then approach each other).

We must then look at what happens to a twist of a submerged tower and towed as well. This twist is activated at a low height requires fairings to navigate backwards or across the stream. The action of flow on these surfaces is so very important (proportional to the surface, angle, water density and the square of the speed) that this action results by powerful torques tend to force hulls to align in the flow but they face the stiffness of the tower twist which then increases. It then happens that a balance occurs and the twist of a tower is terribly reduced in height and the cowling undergoes violent efforts that will tighten the torsion submerged under the effect of the towing speed. In other words, the complete tour of the fairing around the cable will be on a distance becoming shorter. Sea Observations have shown that the fairing column could complete one revolution around the cable over a length of less than 50 cm. When towing, the hydrodynamic flow exerts a very important couple on the misguided hulls of up deterioration of the fairing or until complete rupture of hulls.

During the ascent of a submerged torsion, the fairing has been extensively and very highly constrained, it retains memory of its deformation (i.e. its twisting) and the immersed twist out of the water still very narrow then hoisting and does not disappear when hauling. One speaks of residual torsion. According to the duration of exposure of the shroud to this twisting and submerged towed submerged twist will be able to become permanent or long enough to absorb the making for a long time totally unfit to engage in the cable guiding device although continuity of the shroud is not broken. Side air twist there is no damage, there is indeed a twist applied but at no time it can damage the cable.

When the twist immersed still very narrow is then presented to the guide device, for example the pulley, the hulls affected by this submerged torsion can not be placed correctly in the guide device, including the pulley, they get stuck in the device guide. Then all the fairing column after entering into the guide device that is methodically destroyed if we continued hauling because step by step, each hull follows the orientation of the one before. This can even lead to rupture of the guide device.

The invention provides a shroud configured to reduce the risk of occurrence of a double twist to reduce the risk of damage to the cable shroud.

To this end, the invention relates to a shroud for shrouding an elongate object to be at least partially immersed, characterized in that it comprises a plurality of shroud segments, each shroud segment including a plurality keels, the hulls comprising a channel for receiving the elongated object and being shaped so as to reduce the hydrodynamic drag of the elongate object at least partially immersed, said hull being adapted to be pivotally mounted on the elongate member about the longitudinal axis of the channel, said hulls being bonded together along the axis of the channel and being hinged together, the shroud sections being free to rotate around the channel from each other.

Advantageously, the hulls of the same shroud portion are interconnected by means of a plurality of individual couplings, each individual coupling device for connecting one of said hull section to another section adjacent to said hull said hull.

Advantageously, the fairing sections have respective heights along the axis of the channel, defined according to the angular stiffness k of the respective fairing sections, and according to the chord length LC of said hulls of said respective sections so as to prevent the formation a complete twist on said respective sections.

Advantageously, at least one fairing section has a height along the axis of the channel, set according to the angular stiffness k of said shroud portion and a function of the LC chord length of said free surface of said section so as to prevent the formation a complete air twist on said shroud section when the shroud segment is subjected to a torque of twisting or less equal to a predetermined torque.

Advantageously, at least one section has a height along the axis of the channel, set according to the angular stiffness k of said shroud portion and a function of the LC chord length of said free surface of said section so that the section is adapted to undergo a complete twist and so as to prevent the formation of a complete twist on said air

fairing section when the shroud segment is subjected to a torque of twisting or less equal to a predetermined torque.

Advantageously, the shroud segments have respective heights below a maximum height hmax such that:

p * k

hmax≤

F LC2

where F is a constant between 250 and 500.

Advantageously, at least one section of said sections includes at least one end free surface, adjacent to one another belonging to said hull portion, being a beveled keel so that it has a support edge comprising a first bearing edge bevelled with respect to the leading edge, the first edge support being arranged so that the distance between the leading edge and the first edge support, taken perpendicular to the leading edge, continuously decreases along an axis parallel to the leading edge, from a first end of the first contact edge to a second end of the first support furthest edge of the other hull that the first end, according axis parallel to the edge attack. Each hull is tapered for example an end hull.

Advantageously, the fairing sections have respective heights along the axis of the channel, defined according to the angular stiffness k of the respective fairing sections, and according to the chord length LC of said hulls of said respective sections so as to prevent the formation a complete twist on said respective sections.

Advantageously, the bearing edge is the trailing edge.

Advantageously, at least a first portion of the first bearing edge has a thickness less than a thickness of the hull in any longitudinal plane parallel to the leading edge and perpendicular to the side faces of the hull intersecting the first portion of the first edge support, the side faces extending in respective planes perpendicular to the leading edge.

Advantageously, the hull end is dimensioned to be more resistant to a compressive force applied in a direction perpendicular to the leading edge and connecting the leading edge to the trailing edge, the other section of keels.

Advantageously, the hull comprises two end portions joined or connected along the first bearing edge, the end free surface being configured to be maintained in an expanded configuration when subjected to the hydrodynamic flow of water , the two parts being arranged relative to each other around the first bearing edge such that the end has a hull trailing edge parallel to the leading edge and a constant section along the leading edge and configured to allow the relative pivoting between the two parts around the first edge support when pivoting relative torque applied between the two parts about an axis formed by the first bearing edge exceeds a predetermined threshold so that the hull end passes from the extended configuration to a folded configuration about the bearing edge.

Advantageously, the hulls are rigid.

The invention also relates to an elongate member ducted to be at least partially immersed, comprising an elongated member ducted by means of the fairing according to the invention, the elongate member being received in the channel, said hulls being pivotally mounted on the the elongated member about the longitudinal axis of the channel and being immobilized in translation relative to the elongate element along the axis of the elongate member.

The invention also relates to a tow assembly including an elongated member ducted fan according to the invention, and a towing device and handling designed to pull the elongate member ducted while the latter is partially immersed, the towing device comprising a winch for winding and unwinding the elongate member ducted through a guide device for guiding the elongate member.

Advantageously, the guide device is configured to allow to change the orientation of a hull of the fairing relative to the hull by rotating the guide device about the axis of the elongated element under the effect of the pulling the elongate member relative to the guide device when the hull has an orientation in which it is supported on the guide means and wherein the line of action developed by the elongated element on the pulley extends substantially along the axis extending from the axis of the elongate member to the trailing edge.

Advantageously, the guide device comprises a first groove whose bottom is formed by the bottom of the groove of a pulley, the first groove being defined by a first surface having a concave profile in a radial plane of the pulley, the width of the first groove and the curvature of the first curved surface profile in the radial plane being determined so as to allow to tilt the hull, by rotation of the hull about the axis x of the elongate member under the effect of pulling the elongate member relative to the guiding device along its longitudinal axis from an inverted position in which the hull is oriented trailing edge towards the bottom of the first groove, to an acceptable position wherein it is oriented leading edge towards the bottom of the first groove.

Advantageously, the hull comprises a hull comprising a receiving the elongated member and comprising a leading edge of a shank having a tapered shape extending from the nose and including a trailing edge, the first curved surface forming a first concave curve in the radial plane of the pulley, the first concave curve is defined in a radial plane of the pulley so that when the hull extending leading edge perpendicular to the radial plane, whatever the position of a hull in the first groove when the nose of the hull is supported on the first concave curve and that the elongate member exerts on the hull, in the radial plane, a plating stress of the nose of the hull against the pulley, said plating effort fp comprising a CP component perpendicular to the axis of the pulley and a lateral component CL the trailing edge of the hull is not in contact with the first concave curve or is in contact with a portion of the first concave curve forming, with a dp of the radial plane line perpendicular to the x axis extending from the axis x of the elongate member to the trailing edge of the hull, at least an angle γ equal to a slip angle this. The slip angle is given by the following formula:

this = Arctan (Cf)

Where Cf is the friction coefficient between the material forming the outer portion of the tail of the hull and the material forming the surface delimiting the groove of the pulley.

Other features and advantages of the invention will become apparent from reading the following detailed description, given by way of example and with reference to the accompanying drawings in which:

- Figure 1A shows a cable already described ducted, by means of rigid hulls axially linked, partially immersed towed from the submerged portion to a guide pulley in a situation in which the cable does not undergo double-twist, Figure 1 B shows the cable of Figure 1 a in the same state of immersion (that is to say the winding and unwinding) as in Figure 1A but undergoing double-twist; Figure 1 C shows the cable of Figure 1 A with the double-twist of Figure 1 B in a configuration in which the cable has been unwound with respect to Figure 1 B; Figure 1 D shows the cable of Figure 1 A with the double-twist of Figure 1 B in a configuration in which the cable has been raised with respect to Figure 1 B,

- Figure 2 schematically shows a ship towing a towed object by means of a ducted cable,

- Figure 3 schematically shows a portion of cable ducted fan according to the invention by means of a fairing according to the invention,

- Figure 4a shows a section of a hull of the fairing according to the invention according to the section plane AA shown in Figure 2, Figure 4b shows schematically a side view of the hull of Figure 4a view along arrow b ,

- Figure 5 schematically shows a cable section ducted fan according to the invention entering a cable guide pulley,

- Figures 6a to 6b, cups shows a pulley according to the prior art, according to the side of the hull penetrating the trailing edge towards the bottom of the groove, when it comes to rest on the pulley (6a) and after when the cable has been pulled to the right in Figure 5 (Figure 6b) that is to say that the cable has been lifted and its voltage has crushed the hull),

- in Figure 7, a partial section is shown in a radial plane BB (see Figure 5) of an exemplary pulley according to a first embodiment embodiment of the invention and a reference curve,

- Figure 8a diagrammatically shows a section of a pulley according to a second embodiment of the invention, in a plane formed by a side face of the first keel engaging the pulley (equivalent to the plane M in Figure 5) comprising the point of contact with the pulley, the figures 8b and 8c represent sections of the pulley according to successively occupied planes by the same side face of the hull when winding the cable,

- on Figures 19a and 9b there are shown sections, according to radial planes, two examples of pulleys according to a third embodiment,

- Figure 10 shows schematically, in a plane BB, upper and lower curves of a first curve tub bottom,

- Figures 1 1 a to 1 1 c shows, in successive planes parallel to the plane M of the section of the pulley and the guidelines adopted successively by the side face of the reference hull when the cable is wound , the hull arriving back on the pulley of Figure 7,

- in Figures 12a to 12c there is shown diagrammatically a side view of a hull according to a first embodiment of the invention and a shroud segment comprising a hull according to the invention entering a pulley, in perspective (12a) side view of the entry in the chicken (Figure 12b), in sectional view along the plane M visible in Figure 12a, in sectional view along the plane Q visible on Figure 12d,

- Figure 13 schematically shows an example decarène according to a second embodiment of the invention,

- Figure 14 depicts, in a radial plane of the pulley portion of a first concave curve complying with an advantageous characteristic of the invention,

- Figure 15 depicts a circle constructed with respect to a hull and verifying the advantageous feature of the invention.

From one figure to another, the same elements are identified by the same references.

The invention relates to a fairing for coating an elongate object, for example a flexible object such as a cable or a rigid object such as an offshore drilling column to be at least partially immersed. The elongate member is typically intended to be towed by a floating vessel. The fairing is designed to reduce the forces generated by the current on this elongate member when immersed in water and towed in the water by a naval vessel.

The invention also relates to a towing package as shown in Figure 2, comprising an elongated member 1 ducted by means of a fairing according to the invention. In the following text, the invention will be described in the case where the elongated member is a cable, but it applies to other types of flexible elongate elements.

The cable 1 is towing a towed body 101, for example comprising one or more sonar antennas. The towed body 101 is mechanically secured to the cable 1 appropriately. Up in water and the water outlet of the tow body 101 is performed by means of a winch 5 disposed on a deck 103 of the vessel 100.

The Tow according to the invention also comprises a towing device and handling of the ducted cable comprising:

- A winch 5 for winding and unwinding the cable 1 ducted

- a guide device 4 for guiding the cable 1, the guiding device is arranged downstream of the winch seen from the end intended to be immersed 6, the cable 1. In other words, the cable 1 is wound around the winch 5 (or unwound by the winch) through the guide device 4.

The guiding device 4 is advantageously mounted on a supporting structure 7 for attachment to the vessel can be fixed or tilting.

The guiding device guides the cable 1, that is to say to limit the lateral movement of the cable relative to the winch in a direction parallel to the axis of rotation of the winch drum. It is further preferably configured to change the direction of the cable between its end intended to be submerged winch 6 and 5 in a plane substantially perpendicular to the axis of the winch while to secure the cable radius of curvature so that does not drop below a certain threshold in this plan.

In the nonlimiting example shown in FIG 3, the guide device is a pulley 4. The guiding device may further comprise inter alia a fairlead for securing the cable radius, and / or a spooling device for storing the cable properly on the drum and / or at least one deflector forming a surface for changing the orientation of a hull with respect to the deflector by rotation of the hull about the axis of the cable under tensile effect cable during winding / unwinding. The latter can be achieved by a pulley.

Figure 3 schematically shows a portion 1 cable coated with a Shroud 1 1 according to the invention. This Shroud 1 1 comprises a plurality of sections 12a fairing 12b. Each section 12a fairing, 12b comprises a plurality keels 13, 13a. In Figure 3, there is shown two sections of fairing 12a and 12b each comprising 5 keels shroud but in practice, the shroud may comprise many more fairing sections comprising many more keels.

The hulls are advantageously rigid. By rigid hulls is meant in the present patent application, as the hulls are configured so as not to substantially deform under the effect of the hydrodynamic flow when immersed and towed in the direction of the leading edge. In other words, the hull retain substantially the same shape when subjected to hydrodynamic flow. The hulls may eventually deform under the effect of superior efforts to those developed by the hydrodynamic flow.

They are for example made of hard plastic material such as polyethylene terephthalate (PET) or polyoxymethylene (POM).

Each hull 13, 13a has a hydrodynamic profile of the type shown in Figure 4a, in an AA perpendicular to the axis x of the cable plane (or axis of the channel 1 6). In other words, each hull 13, 13a is shaped so as to reduce the hydrodynamic drag of the cable 1 when the cable 1 is pulled. 13a keel hulls are having the same characteristics as the keel 13, but may differ from the free surface 13 of the features which are explained later due to their position in the sections 12a, 12b. Each hull 13 comprises a broad nose 14 for receiving the cable 1 and a shank 15 having a tapered shape extending from the nose 14. The nose 14 houses a channel 1 6 with an axis perpendicular to the plane of the sheet, for receiving the cable 1. The nose 14 includes the leading edge BA and tail 15 includes trailing edge TE which are the extreme points of the hull 13 into the cutting plane. The hull 13 has more particularly in this plane a profile-shaped wing. The hull profile allows a less turbulent flow of water around the cable. The hydrodynamic profile has such a form of drop or NACA is to say, a profile defined by the NACA which is an acronym of the English expression "National Advisory Committee for Aeronautics."

In Figure 4b, there is shown a plan view of the hull according to the arrow B, which is the same view as in Figure 3. The hull has an elongated shape from the leading edge BA to the trailing edge TE. Side view of the hull 13 has a substantially rectangular shape defined by the trailing edge TE and the leading edge BA xc parallel to the axis of the channel 16 and connected by two lateral faces 17, 18. The side faces 17, 18 extend substantially perpendicular to the trailing edge BA. The side faces are arranged at respective ends of the channel 1. 6

In Figure 4a, is referenced LC chord length of the hull 13 which is the maximum length of the line segment CO called rope connecting the trailing edge TE and the leading edge BA of the hull 13 in a direction perpendicular to the axis of the tenth channel. In other words, the rope is the line segment connecting the end points of the hull section.

The maximum thickness E of the hull is the maximum distance separating the first longitudinal face 22 of the second longitudinal side 23 in a direction perpendicular to the chord CO in the section of the hull plan. On the embodiment of Figure 4b, the distance between the trailing edge and the leading edge is constant along the axis of the tenth channel parallel to the leading edge BA. The cord length is the distance. The longitudinal faces 22 and 23 extend parallel to the leading edge BA.

The hulls 13 are intended to be mounted on the cable 1 so as to be pivotable about the longitudinal axis of the cable 1, that is to say about the longitudinal axis of the channel 16.

The keels 13 belonging to the same 12a or 12b fairing section are interconnected by means of a coupling 20 permitting relative rotation of said keels 13 from each other around the cable 1. The coupling device 20 binds the hulls together both axially, that is to say along the towline mas also rotated around the cable 1. The coupling device 20 allows the relative rotation of the hulls with respect to each other around the cable axis, that is to say channel 1 6. This displacement is permitted to be freely with a stop. The rotation of a hull around the cable does not then drives the adjacent hull rotation. The deflection can be obtained in manner constraint with a point more or less strong towards the aligned position (no hulls of relative rotation with respect to each other around the cable). In the latter case, rotation of a hull around the cable rotated adjacent hulls of the same length around the cable. Advantageously, the clearance between the adjacent surfaces is substantially zero, so that relative rotation between the hulls involves elastic deformation of the coupling device. This allows the keel of the same section to adopt an orientation with respect to the cable allowing it to oppose the lower resistance to flow caused by movement of the cable in the water. The coupling device allows the relative rotation with a maximum amplitude, that is to say the maximum angular displacement. In this way, the rotation of a hull causes a rotation of neighboring keels and step by step the hulls of all of the same section 12a or 12b. All the hulls of the same section adopt the cable lift of a wire

same orientation relative to the drum which allows to wind the cable maintaining the parallel scales the one to the other alternately.

Advantageously, the coupling device 20 permits the relative rotation of the hulls with respect to each other so as to allow the winding of the cable around a winch, the lateral deviation of the cable due for example to the ship's heading changes . The coupling device allows the rotation of relative movements of the hulls one relative to the other with respective maximum angular deflections.

The coupling device 20 shown in Figure 3, comprises a plurality of individual coupling devices 19, comprising for example a fishplate, each capable of connecting a hull adjacent to said hull hull, that is to say coupling the free surface of the same section in pairs. In other words, each individual coupling device used to connect a hull another hull adjacent said hull only. The adjacent hull form hulls couples. The hulls of the respective hulls of couples of the same shroud portion are connected by means of separate individual coupling devices. The coupling device makes it possible to individually connect each hull of a fairing section at each of its adjacent hulls. Advantageously, the individual coupling devices are configured to elastically deform upon relative rotation hulls around the cable. It is a twisting of individual couplings.

When there is twisting a fairing portion, there is deformation of the fairing section. This deformation is obtained by elastic deformation of the coupling device 20 and / or the hulls so that the fairing section is opposed to the twisting due to its torsional stiffness. In other words, the shroud has a restoring torque in the opposite direction to the torque applied on the cowling for generating torsion. These elastic deformations are twists. In the case where the shroud includes individual coupling devices 19, the individual coupling devices 19 deform elastically during the twisting of the shroud. Conventionally, the hulls have a stiffness such that they also deform elastically during the twisting of the shroud. These elastic deformations are twists.

Advantageously, the hulls 13 are immobilized in translation with respect to the cable 1 according to the cable axis x. This avoids the hull 13 does not pack down or distance themselves along the cable 1 which could result in the fairing 1 1 blocking problems when winding the cable careened around the winch drum or 5 even the passage of guide device 4. for this purpose, each fairing section 12a, 12b comprises a fixing device 21 cooperates with a portion 12a of said hull 13a, 12b and designed to cooperate with the cable 1 so as to immobilize the hull 13a in translation along the axis of the cable. In the embodiment of Figure 3, 13a hull is the hull furthest from the end intended to be immersed 6 located in the direction of arrow f (called head hull). The hulls being bonded together, the locking achieved by the fixing device on a free surface 13a is reflected on the other free surface of the same section. The installation of an immobilization device by hull is not necessary thereby to limit costs and the assembly time and weight of the ducted cable. Alternatively, the section comprises a plurality of fastening devices each cooperating with a hull of the section. The fixing device comprises for example a ring 21 fixed to the cable by crimping 13a and cooperating with the free surface in order to immobilize in translation relative to the cable along the x axis of the cable 1.

According to the invention, the sections 12a and 12b fairing are free to rotate, one with respect to the other, about the axis of the channel 16, that is to say about the axis of the cable 1 when they are mounted on the cable 1. In other words, the keels 13, belonging to two distinct sections 12a and 12b fairing are free to rotate one with respect to the other, about the axis of the channel, that is to say, around the cable 1. Each portion 12a, 12b is relatively flexible in rotation around the same cable if a certain torsional stiffness is observed. This flexibility only increase with the extended length. For this reason, the act of cutting the free fairings section fairing in rotation relative to each other can limit the risk of double twists training, and thus reduce the risk of damage to the fairing, since twisting sections shroud are not transmitted from one section to another. The

fairing can be installed along the cable. In other words, the shroud extends over the entire length of the cable. Alternatively, the shroud extends along the cable over a length less than the length of the cable.

The fairing is designed to streamline an elongate member. It is also intended to be towed by a towing device as described in the present patent application.

The heights h, respective fairing sections, that is to say their length along the x axis of the cable, are lower than a maximum height hmax. Alternatively, at least one of the sections has a height less than the maximum height hmax. In Figure 3 the two sections of the same length but this is not an obligation. Hmax is the maximum height selected to be sufficiently low to prevent the formation of a complete air twist on the section, for example a complete twist on the stretch. The disrupted section can make a complete turn on itself and realigns the flow because it is decoupled from its neighbors this stretch disturbs most and there is neither air twisting or torsion submerged. This configuration prevents the old submerged complete twists from entering the guide device and therefore limits the risk of deterioration of the fairing. Moreover, this configuration avoids having to set up a monitoring procedure by the crew or a monitoring device to detect submerged twists as well as mechanical or manual procedure to reduce a double torsion detected or to assist a submerged outgoing remanent twist of the water to penetrate into the guide device without causing damage.

Advantageously, the height of at least one section, and preferably of each section is defined so as to prevent the formation of a complete twist of said air shroud section when the shroud, or the elongate member ducted by means of the fairing is towed in the towing predetermined nominal conditions of the fairing, the fairing section being partially immersed. Arian twist is the twist experienced by the aerial part, that is not immersed, the fairing section.

Nominal towing conditions defined by a nominal sea state, a rated speed at which the cable is intended to be towed, that is to say, the nominal speed of the ship, and the height at which is intended to be the point towing of the fairing with respect to the sea level. the nominal sea state, the nominal speed and the height of the towing point may be predetermined or included in respective predetermined nominal interval. When the fascia is being towed so that the shroud portion is partially immersed in nominal conditions, the fairing section is subjected to a torque which is less than or equal to a predetermined maximum torque This torque maximum torque is defined by nominal conditions. The predetermined maximum torque can be obtained by calculation or empirically by measuring the torque exerted by the fairing section in the nominal conditions.

The maximum height of the fairing section is defined so as to avoid the formation of a complete twist air on the shroud segment partially immersed when the fairing section is subjected to a torque of twisting or less equal to the predetermined maximum torque.

The height of the fairing is defined empirically by varying the length of the fairing section in nominal conditions more stringent towing generating torque maximum torque so as to obtain a height such that it prevents an air twist complete the fairing section. It can also be determined by simulation by modeling the behavior of the fairing section in the most demanding nominal conditions and varying the height of the segment to achieve the desired effect.

Therefore, when the fairing section is towed in the nominal and partially immersed condition, the aerial part of the fairing is subjected to a torsion torque of the waves. If this torque is less than or equal to the torque of maximum torque, it will undergo a torsion but the forces applied by the guide device and in the submerged part are balanced so that the shroud will perform a complete revolution about itself about the elongated member (or around the channel) before its aerial part does not undergo a torsion compète. Therefore, the appearance of a complete air twist and therefore, the appearance of a double torsion is avoided.

In a preferred embodiment, the height of at least one section, and preferably of each section is selected so that the portion is adapted to undergo one complete twist. The height of the segment is large enough to allow this torsion. However, this height is selected, as previously, so as to prevent the formation of a complete air twist on said shroud section when the shroud, or the elongate member ducted through the fairing, is towed in the towing conditions nominal predetermined fairing, the fairing section being partially immersed. In other words, the height of the section is sufficiently small so that when the shroud (or the cable is ducted) is towed, partially submerged and is subjected to a torque of maximum torque, it can not undergo air twist. However, it may undergo a complete twist when subjected to a torque greater than the maximum torque.

The height of the section is defined as a function of the angular torsional stiffness k of said shroud portion, depending on the LC chord length of said hulls of said section and according to the nominal towing conditions.

A fairing section T undergoing a torsion angle Θ about the axis x of a cable (or channel 1 6) is subjected to a torque C applied around the axis x of the cable 1. The torque C to obtain the twist angle is given by the following formula:

k9

C = T

Where k is the angular torsional stiffness of the fairing portion about the axis of the cable (or channel), expressed in Nm 2 / radians, h is the height of the fairing section, that is to say the length of the shroud section according to the cable axis or the longitudinal axis of the leading edge.

The maximum height hmax depends on the torsional stiffness of the fairing sections. More fairing sections show significant stiffness around the axis of the cable and they can present a significant height. Over the fairing chord length and the greater the fairing section will be disrupted by the solicitations of the sea and the tow conditions and the maximum height of the fairing sections is low. Disturbances torsional stresses generated by the sea and towing conditions are proportional to the surface of the section of the keel (ie the chord length) and the lever arm (and therefore the fairing chord length). The maximum height h max is given by the following formula:

p * k

Where F is a constant calculated in a pattern which has been identified as the most constraining and which takes account of the flow and the wake reflux and LC is the length of the chord of the hull of the fairing section.

The constant F is between 250 and 500. F depends on the maximum speed at which the tow cable is desired. If one wishes to pull the cable at a speed of 20 knots, F is set at 400 F is lower if the maximum speed decreases.

Typically, for fairings having an angular torsional stiffness k of the order of 4 to 5 Nm 2 / rad and a LC chord length of 0.125M, and the maximum of the order of 2m if the constant is fixed height 400.

The fairing according to the invention presents the same advantages in the case where there is no attempt to wind the cable around a winch. Indeed, the fact that the fairing according to the invention minimizes the risk of double twists training allows to limit the risks of deterioration of the fairing associated with aging without twists immersed they enter a guide device. The fairing of the invention thus limit the needs for cable maintenance.

Advantageously, the guide device of the towing package according to the invention is configured so as to allow to modify the orientation of a hull of the fairing with respect to the rotation guiding device of the hull around the axis of cable, as the cable pulling the effect relative to the guide device (according to the cable axis) when the hull has an orientation in which it is supported on the guide means and wherein the line action of force exerted by the cable on the guiding device extends substantially along the direction extending from the cable axis to the trailing edge of the hull.

Advantageously, the guide device is configured to return a hull since an inverted position in which it is orientated tail down, until an acceptable position wherein

it is oriented tail upwards. Orientations up and down are defined with respect to a vertical axis associated with the winch.

These configurations to facilitate winding the cable keeled on the winch. Indeed, when one comes winding the cable around the winch drum, the first keel on each section out of the water rises towards the guide device and is not linked to the free surface of the previous section, it will turn trailing edge down under the effect of gravity, taking with it the following hull fairing of the same section. If the guide device does not allow such a reversal, the hulls will get misguided on the winch drum (preferred wrap the hull trailing edge upward to avoid damage of the fairing because the edge is more resistant ).

For this purpose, the guide device comprises a guide or a set of guides for the change in orientation or tilt of the hull. This guide or guide assembly may for example comprise a pulley and / or a baffle or any other device for changing the orientation of the hull about the cable axis. A non-limiting example of this type is described in the French patent application published under number FR2923452. These devices are conventionally disposed upstream or downstream of the pulley view of the winch. They are typically concave, that is to say the type grooved so as to define a housing for receiving the hull to ensure its pivoting. These guides can be adapted to follow the wire in the event of lateral displacement of the cable parallel to the axis of the pulley (or winch), for example by being pivotably mounted about a substantially vertical axis.

So far all towing rollers are configured to pass the keel nose to the back of the throat and tail outwardly of the throat. This provision is logical since the towing cable, seat of effort, is necessarily housed in the nose of the hull, that is to say close to the leading edge. All towing pulleys then have a narrow throat V. This provision is made necessary because of the links between all the hulls. Leaving the sea and arriving at the towing pulley, the hulls that during their flight path, tend to orient themselves trailing edge down (upside down so) are thus recovered by degrees through links

Inter-hulls. When a keel is well positioned in the groove of the pulley, when hauling (but also unwinding) all of the following will gradually recover and to spend the pulley.

Furthermore, devices for reversal of the fairing (or rectifiers) are inefficient when installed downstream of the pulley to the free end of the cable because the cable position has at this place at least two degrees of freedom: lateral and longitudinal, and the current rectifier devices are not able to correctly follow the wire in these two directions or they are complex devices.

In the case of a narrow sheave V, if the guide device has no downstream turning device of the pulley to the free end of the cable, or if the device is not performing hulls incoming queue down in the pulley will be able to get stuck in the throat and, if they are not designed to withstand the force exerted by the cable in this direction, they will deform and cause deformation of the following hulls. This situation is shown in Figures 5 and 6a-6b. In Figure 5, there is shown a portion of a 1 faired cable entering a P sheave 50. In this figure, winding the cable 1 which then enters the pulley following the direction of the arrow. In this figure, the xp axis of the pulley is perpendicular to the plane of the sheet. The keel 13 of a first group of keels 12a are oriented trailing edge TE outwardly of the groove and leading edge to the throat. 13a remarkable hull is the hull of head section 12b, that is to say the free surface 13a of the section 12b that is farthest from the cable end to be immersed 6. The hull 13a is presented to the pulley P trailing edge TE to the pulley groove and the leading edge BA to the outside of the throat. This remarkable hull 13a belongs to a second group 12b keels.

If pulley P is a prior art pulley, the section of the pulley of the prior art in the lateral plane M passing through the edge 18 connecting the trailing edge TE and the leading edge BA of the shell head as seen in Figure 6a. 6b a pulley section P of the prior art in another plane including the side edge 18 of the head 13a of hull to the right of plane M in Figure 5 because the cable 1 has been hoisted, c ' ie pulled along the arrow shown in Figure 5 between Figure 5 and Figure 6b, by advancing the remarkable hull 13a in the groove. The groove of the pulley has a V-shaped section having an opening between 20 ° and 50 °. The bottom of the V has a substantially complementary shape to the leading edge so that when a hull enters the leading edge pulley upwards, the following keels linked to this hull will also move in this direction during winding cable. However, if a head 13a comes hull trailing edge towards the groove 105 as is the case in Figure 6a, the groove is too narrow for the hull trailing edge turns up under the effect of pulling the cable with respect to the groove of the sheave along its axis. The cable tension forces head hull 13a down to the bottom of the gorge. Indeed, when pulling the cable along its axis in the pulley, it develops a force to the shell, oriented in the force action line of the arrow in Figure 6a. However, if the hull is not designed to withstand this stress, it deforms and breaks (or deteriorates), as shown in Figure 6b.

To overcome these drawbacks, the invention aims to entrust a flip function hulls around the axis of the cable to the pulley itself.

To this end, the invention is to provide a towing assembly comprising a cable guiding device arranged downstream of the winch view of the cable end to be immersed, the guide device comprising a first groove whose bottom is formed by the bottom of the groove of a pulley, the first groove is configured so as to allow to switch a free surface of the fairing, by rotation of the hull about the axis x of the cable under the effect of the tension of the cable, since an inverted position in which the hull is oriented trailing edge (or tail) to the bottom of the first groove, to an acceptable position in which it is orientated leading edge (or nose) to the bottom the first groove, that is to say trailing edge outward from the groove. The dimensions and shape of the first groove profile, in particular, the width of the first groove and the curvature of the first curved surface profile (which will be defined later) in the radial plane are determined depending on the radius R of the pulley the maximum length RAC, taken parallel to the chord between the trailing edge BF hulls of the fairing, the x axis of the elongate member 1, the LC chord length of the hull and the maximum thickness E of hulls so as to allow to tilt the hull of the position back to the acceptable position.

When the trailing edge (or tail) is oriented towards the bottom of the first groove, this means that the trailing edge (or cutting of the tail end) is situated at a shorter distance that the leading edge ( or the nose) of the axis of the pulley xp. The axis of the pulley is the axis about which rotates the pulley with respect to the winch, that is to say with respect to the fixed portion of the winch.

Advantageously, the axis of the pulley is substantially horizontal, that is to say intended to extend parallel to the surface of the water in calm sea state when the towing device is fastened on a naval ship or vessel .

The bottom 26 of the pulley groove forms a circle of radius R whose center is on the axis of the pulley.

In Figure 7, there is shown a section of the pulley P in Figure

5, in the radial plane BB of the pulley P, where P pulley is a pulley according to a preferred embodiment of the invention. A radial plane of a pulley is a plane which is formed by a radius r of the pulley and the xp axis of the pulley about which the pulley rotates. The radius r has a length

R.

The first groove 24 is delimited by a first surface whose section in the radial plane BB is the first concave curve 25 (U-shaped curve shown in bold in Figure 7). The first concave curve 25 comprises a bottom 26 of the first groove 24. The bottom is the point of the first groove 24 which is the closest to the xp axis of the pulley.

In Figure 7, a reference curve is also shown by 28 V. The reference curve 28 V is the section in the radial plane BB, a second curved surface defining a second reference groove 29 and second groove Virtual. The bottom of the second groove, that is to say the bottom of the reference curve 28 is the bottom 26. The bottom V is the intersection of two legs 31, 32 of the V.

According to the invention, the opening of the V ccv is at least twice as a threshold angle and the width of the V Iv taken along a line d parallel to the axis of the pulley, is at least equal to a width threshold Is given by:

ls = 0.7 * lid

Where lid = 2 (SC + S) * sin (as)

R

as = I *

R - CAR

lid is a great width of the V,

where ai is a limit angle greater than 45 ° and less than 90 °, where R is the radius of the pulley and wherein CAR (shown in Figure 4a) is the maximum length, separating the trailing edge TE hulls fairing the cable axis, measured parallel to the chord CO hulls where LC is the chord length of the hull and E is the maximum thickness of keels.

In a preferred embodiment of the invention, the width v is at least equal to lid. The reversal is then more easily.

Advantageously, the limit angle I is given by the following formula:

ai = π / 4 + -Arctan (C)

where Cf is the friction coefficient between the material forming the outer portion of the tail of the hull and the material forming the surface delimiting the groove of the pulley. The material forming the outer portion of the tail of the pulley is the material forming the hull when it is made in a single material.

In the embodiment of Figure 7, the first curve 25 is coincident with the second curve 28 at the end points 33, 34 of the second curve 28. The end points 33, 34 of the second curve are the points of the second curve which are Iv spaced from the width in a straight line parallel to the axis of the pulley xp. They define the first groove and the second groove along an axis parallel to the axis of the pulley and along an axis parallel to the radius of the pulley passing through the bottom 26. The first curve 25 is, at any point between each of the points extreme 33, 34 and the bottom 26, coincident with the second curve or closest to the axis of the pulley xp that the second curve along the radius of the pulley in the section plane BB.

Therefore, to ensure the desired turning the first concave curve 25 defining the first groove 24 may have the profile shown in Figure 7 or lie between the endpoints at any point other than the bottom and points end 33, 34, under the curve 28 and at least a distance from the axis equal to the distance separating the bottom of the pulley of the axis of the pulley (radius R of the pulley). In other words, the first concave curve is at all points in the space delimited by the curve 28, the straight line D1 parallel to the axis passing through the bottom 26 and the straight d3 and d4 parallel to the radius R of the pulley passing by points 33 and 34.

The first concave curve 25 is the curve defining the first groove 24 for receiving the cable ducted in a radial plane (see Figure 7).

In Figure 14, there is shown in dotted lines, in a radial plane a portion 250 of a first concave curve complying with an advantageous feature of the invention. The hull 13 extends leading edge perpendicular to the radial plane. This characteristic is: the first concave curve is defined in a radial plane BB of the pulley so that when the hull extending edge BA perpendicular to the radial plane BB, regardless of the position of a hull in the first groove 24, when the nose 14 of the hull 13 is supported on the first concave curve and the cable 1 exerts on the hull 13, in the radial plane, a plating stress of the nose of the hull against the pulley, said plating Fp force comprising a component CP perpendicular to the axis of the pulley and a lateral component CL (that is to say parallel to the axis of the pulley) the trailing edge of the hull 13 BF n ' is not in contact with the first concave curve or is in contact with a portion 251 of the first concave curve forming, with a dp of the radial plane line perpendicular to the x axis extending from the cable axis until x trailing edge of the hull, an angle y at least equal to one has sliding ngle this. The slip angle is given by the following formula:

at = Arctan (C/)

This feature prevents the keel blocks the cable into the groove when the cable moves laterally in the groove, that is to say parallel to the axis of the pulley. Indeed, if this angular condition is met, it is ensured a slip of the hull in a side of the thrust cable. In other words, a pulley having a profile as defined with reference to Figure 14 ensures that turning of the hull since an inverted position to an acceptable position.

The first concave curve 25, and therefore the profile of the first groove, is obtained by the skilled person by simulations from this definition.

In practice, this angle a of the order of 10 °, a first curve forming a curved line having at any point a radius of curvature at least equal to half of the LC chord length of the hull ensures the sliding of the hull in a side of the thrust cable. A curved line is a line free of sharp edges or projecting (in the mathematical sense). Indeed, if one traces, as shown in Figure 15, a circle Cr through the nose of the hull 14 and the trailing edge TE of the hull 13, the tangent T at the trailing edge forms an angle that with the right dp, RA radius of the circle is approximately equal to 55% of the chord length LC of the hull, which is greater than the value of 50% above deduction.

Advantageously, the dimensions and shape of the first groove profile are determined so as to allow to switch a reference hull having a maximum length RAC, taken parallel to the chord between the trailing edge BF hulls of the fairing, a length of LC rope hulls and a maximum thickness E and optionally depending on the coefficient of friction Cf between the reference hull and the pulley. These dimensions and profile are advantageously defined so as to ensure the tilting of the hull since an inverted position to an acceptable position without deforming between this reference hull.

In the embodiment of Figure 7, the width of the first Ig groove is equal to the width of the V Iv. Alternatively, the first groove extends beyond the end points. It may comprise the pulley groove only, or understand the pulley groove and being delimited on either side of the pulley by baffles or vertical flanges (that is to say perpendicular to the axis of the pulley) or substantially vertical. The first groove may further be the groove of the pulley which comprises, beyond the V or V above the vertical walls (that is to say perpendicular to the axis of the pulley) or substantially vertical. The walls and end plates as defined help prevent the cable leaves the first groove in the event of lateral displacement.

In the embodiment of Figure 7, the first groove is the groove 24 of the pulley. Alternatively, the first groove comprises pulley groove. The bottom of the first groove is the bottom of the groove of the pulley. However, the first groove extends beyond the pulley groove. It is for example delimited at least on one side of the pulley with respect to a plane perpendicular to the axis of the pulley, by a deflector or a flange. The baffle or flange may be fixed relative to the pulley or rotatable relative to the pulley around the axis of the pulley. Advantageously, the first groove comprises lateral edges to limit the lateral deviation of the cable. The side edges may extend completely within the area between the two extreme points or partially and also extend partially beyond these points.

The pulley, and more specifically the pulley groove, has a constant profile. In other words, it is the same as all the radial planes of the pulley.

The first curve 25 and second curve 28 are symmetrical with respect to a plane perpendicular to the xp axis of the pulley and having a radius of the pulley passing through the bottom 26. This plane is then the median plane of the groove.

We will now explain more precisely how is obtained the pulley profile according to the invention as shown in Figure 7. The applicant is party to the realization that we open the V 6a so that the tail can clear on side during winding of the cable. Figure 8a is a partial section there is shown a pulley 40 according to a second embodiment, in the plane M, which is a plane formed by a side face 18 of the head 13a of the hull segment 12b contacting with the pulley. The lateral face includes point of the hull entering first into contact with the pulley. The pulley has a profile open V for obtaining the turning. In this figure, the pulley 40 includes a groove 44 V-13a remarkable hull is supported on a first leg 45 of the V edge towards the bottom 46 of the groove 44.

The opening of the ccg groove is such that the angle between the force application line (represented by the arrow shown in the hull) and the second tab 47 ccf is greater than 90 °. In this case, it gives the tail a clearance channel which allows it to return along the arrows shown in Figure 8a to adopt the position shown in Figure 8c passing through the position shown in Figure 8b following the movement indicated by the arrows by pivoting about the axis of the cable under the action of the cable tension (exerted in the force action line) when the cable is pulled along the groove. As shown in Figure 8a, the direction of force line of action is substantially parallel to the first leg 45. This is why the opening of the V ccg in the plane M, which is at least equal to twice the angle have limit is substantially equal to ccf. Therefore, the opening of the V ccg is greater than 90 °. To account for friction between the tail of the hull and the surface of the groove, the opening limit ccg = 2 * cci is at least equal to 95 ° and preferably at least 100 °.

The angular characteristic is not sufficient to get the right turning of the hulls. It is necessary that the width of the groove Igm in the plane M is at least one li limit width which is given by the following formula:

li = 2 (LC + E) * sin of

Or, as shown in Figure 5, the profile of the groove of the pulley in the plane BB is the projection, on a plane forming an angle β with the plane M, the profile of the groove in the plane M. The angle β depends on the CP length that is the maximum length between the trailing edge BF hulls fairing the axis of the cable taken parallel to the chord CO 13a hull. It is defined as follows:

CAR = R - R cos/?

CAR = R (1 - cos/?)

CAR

β = arccosÇl — )

R

It is therefore correct the V previously defined by the bias introduced by the angle β. The ccv opening of the V formed by the second curve 28 in the plane B is at least equal to a threshold angle as. threshold angle as is given by the following formula:

to

Where as = I *

R-CAR

Therefore, the width of the V Iv in the plane B is at least equal to the ideal width lid given by the following formula:

lid = 2 (LC + E) * sin as

The first curve 25 defining the first groove 24 has at least from the first extremal point 33 to the second end point 34 a concave shape.

It may have at least from the first extremal point 33 to the second end point 34 a V-shaped or have a plurality of sharp or projecting angles AS as shown in Figures 9a and 9b. In other words, curve substantially forms a broken line in these figures, the curves have a sharp edge or projecting at the bottom 26 and are symmetrical with respect to the plane perpendicular to the axis of the pulley and having a radius of the pulley. These profiles are more efficient to ensure the reversal of the hull profile V. These profiles are advantageously, but not necessarily symmetrical with respect to a plane perpendicular to the axis of the pulley passing through the bottom 26. Alternatively, the first curve has sharp edges and has a substantially tangent parallel to the axis of the pulley at the bottom xp. The bottom is then the curve point situated on the median plane of the groove.

Advantageously, as shown in Figure 7, the first curve 25 is between the extreme points 33, 34, a curved line. In other words, there is a concave curve free of sharp angles or projecting (in the mathematical sense). We talk about profile U. In other words,

curve substantially never comprises more than one tangent in the same point. Its derivative is substantially continuous.

When the first groove (or first curve) has a section V-shaped (first curve V), it must have a width at least equal to lid so that the turning is guaranteed. When the first groove (or first curve) has a section such that the first curve is U-shaped, while it may have a smaller width up to 0.7 * lid because it does not present sharp edges in which the tail of the hull can get stuck. In this case, the opening of the V may also be less than the threshold angle. In other words, the V should have a width at least equal to 0.7 * lid. However, the reversal may be more difficult than when the V has a width of at least lid. Below this threshold, it is not certain that the reversal takes place.

Advantageously, in the case of a first groove having a U-shaped profile, the first groove is tub bottom. The groove presents tub bottom the advantage of ensuring a certain fluid and reorientation of the hull and can guide the hull in a substantially lying position in the bottom of the groove.

This means that the first curve has a central zone, the central zone has a width equal to g * lid when lid is the ideal width and g is between 0, 7 and 1, between the combined extreme points with extreme points a reference curve 128 V having a width equal to g * lid. The central zone is delimited by the two curves (see shaded area) 10:

- an upper curve SUP having a first radius of curvature radius R1 equal to V2 * g * lid through the bottom and whose center is located on a line perpendicular to the axis of the pulley passing through the bottom,

- a bottom comprising a curved INF PERCENT central portion extending substantially parallel to the axis of the pulley symmetric relative to a plane perpendicular to the radial plane passing through the bottom and extending along the axis of the pulley a first width equal to ½ * g * lid and comprising, on either side of the central portion PERCENT, side portions LAT1 and LAT2 connecting the central portion to the end points 133, 134 and having a second radius of curvature R2 equal to 1/4 * g * lid. Each lateral portion extends over a width equal to ¼ * g * lid along the axis of the pulley. The centers of the side portions are symmetrical to each other relative to the PV vertical plane passing through the base and perpendicular to the axis of the pulley xp

The central area may be one of the two curves. The lower curve is the preferred embodiment of the invention.

Advantageously, the central zone of the first curve is formed by a pulley having a groove whose width is the width of the central zone.

Advantageously, the first curve comprises upper portions extending substantially perpendicularly above the extreme points of the V so as to prevent the cable out of the first groove during a vertical movement of the cable. These flanges are secured to the pulley or pulley belong to or are fixed with respect to the axis of the pulley.

The first curves between the upper curve and the lower curve have the advantage of checking the angular condition to avoid that the keel prevents the lateral displacement of the cable.

In Figures 1 1 a to 1 1 c shows, in parallel successive planes to the plane M, guidance successively adopted by the side face of the reference hull comprising the first point to contact the pulley, when is wound the cable. The hull trailing edge 13a comes down (Figure 1 1 a in the plane M) and when the cable is pulled, it pivots about the axis of the cable (see Fig 1 1 b), under the effect the tension of the cable, until reaching the substantially flat position in which the leading edge is facing the bottom of the groove and the leading edge is facing out of the groove (Figure 1 1 c ). This profile allows to facilitate and simplify the tilting of a hull because the flattened central portion of the pulley groove implies a substantial distance between the axis of the reaction of the pulley groove on the hull (axis extending from the edge leakage towards the center of the portion of a circle formed by the central portion) and the axis of rotation of the hull (extending along the axis trailing edge - to the axis of the channel xc or x axis of the cable) due to the large distance between the cable axis and the center of the portion of a circle formed by the central portion. This profile also enables the cable and the fairing which are placed substantially flat to come to rest safely on the flanks of the pulley when the cable is biased laterally (that is to say parallel to the axis of the pulley) in the event of e.g. vessel bend. If the cable and shroud leading edge are positioned on the right side, they stay there. If they are on the wrong side, the pulley profile allows almost turning smoothly allowing the cable (where sit efforts) to bear against the side of the pulley. This shift is present but less fluid in the other pulley configurations.

In summary, the pulley according to the invention, more generally the guiding device according to the invention ensures the recovery of a free surface bears on the pulley with a trailing edge orientation towards the bottom of the groove of the pulley and edge vertical to the trailing edge. The hull carries with it the hulls to which it is linked in rotation around the cable, that is to say, the hulls of the same section. The pulley according to the invention also makes it possible to straighten the hulls of a cable arranged in a single section in which the hulls are all linked together to rotate around the cable in case of breaking of inter-connecting keels for example in the effect a double twist thereby ensure a passage of the cable in the pulley ducted without deformation of the keels. It also helps to straighten the head hull with a fairing comprising a single section extending a length less than the length of the cable from the end intended to be submerged. It also helps to straighten the hulls of a cable including streamlined hulls which are free to rotate around the cable by each other. It also allows, due to its width, to ensure the guiding of an organized into a single cable section having a residual twist (torsion immersed very narrow unabsorbed to the passage of the pulley) without deforming the hulls which is not possible with a narrow V pulley.

The guiding device according to the invention is efficient and simple because it does not require the establishment of cable follower device (that is to say able to follow the cable when it moves laterally and vertically with respect to pulley).

The pulley according to the invention, more generally the guiding device according to the invention, because of its profile, does not provide a turning of the hull to a position wherein the trailing edge is located vertically above the leading edge. For example, in the case of the pulley tub bottom, the hull is returned into a position in which it is substantially flat (slightly raised trailing edge up). It must therefore rotate about ¼ turn against V2 turn (if it were to adopt the trailing edge position above and vertical leading edge) which facilitates the hull recovery operation by the pulley .

Advantageously, the guide device comprises, between the winch and the pulley, a rectifying device to guide keels coming out of the pulley in the direction of the winch about the axis of the cable so that they have a predetermined orientation with respect to the winch drum, e.g. leading edge downward and the trailing edge to the vertical of the leading edge. These devices are only really effective when the position of the cable is well known (and this is the case at the outlet of the pulley).

In the embodiment of Figures 4a and 4b, the hulls of the sections have a constant section, that is to say fixed, along the leading edge. By section is meant the free surface profile in a transverse plane, ie a plane extending perpendicularly to the leading edge BA, that is to say the axis of the channel xc. By constant section means a section having substantially the same shape and the same dimensions in all transverse planes, regardless of their positions along the leading edge between the side faces 17, 18. In other words, the trailing edge BF is substantially parallel to the leading edge BA over the entire width I of the hull. The width I of the hull is the distance between the two side surfaces 17, 18 along an axis parallel to the leading edge BA.

The trailing edge BF is a parallel support edge to edge BA.

Alternatively, as shown in Figures 12a to 12c, at least one of the fairing 130 is a beveled keel hull. A bevelled hull is a hull which comprises a BAPA support edge comprising a first bevel bearing edge BZA from the edge of BAa attack, the bevel being designed so that the distance between the leading edge and attack BAa the

first edge support in BZA bevel taken along an axis perpendicular to the edge of BAa attack and to the axis xc of channel 1 6 varies linearly along the axis xc. By first edge support in BZA bevel means a first BZA support edge which extends longitudinally substantially along a straight line which is skewed or inclined relative to the edge of BAa attack. The first bearing edge BZA extending longitudinally in a first plane containing a plane or parallel to the plane defined by the edge of BAa attack and CO chord of the hull. In other words, the first bearing edge BZA is skewed to the edge of BAa attack in the foreground.

The support edge BAPA extends longitudinally between two ends

E1 and E2. The support edge BAPA is arranged so that the distance between the BAPA bearing edge and the edge of BAa attack decreases continuously from a first end E1 of the first bearing edge BZA to a first lateral face 180 of the hull nearest the second edge of the first support BZA that the first end of the supporting edge, along an axis parallel to the leading edge BA.

In the embodiment of Figure 12b, the lateral side 180 is the side face 130a of the hull furthest from the free end of the cable 6 (visible in Figure 2) in the opposite direction of the arrow. The other lateral side 170 is the side of the free surface 130a closest to the free end 6 of the cable. This feature facilitates the turning of the hull 130 when it comes to bear on the pulley by its trailing edge, upon winding the cable, i.e. when pulling the cable with respect to the xp axis of the pulley according to the arrow f. Indeed, in Figure 12b, the position is represented P 'on the pulley 4 of Figure 7, the point where the free surface 130a comes into contact with the pulley 4 as a result of the traction of the cable with respect to the xp axis of the pulley in the direction of the arrow. This point is located at a distance B '(shown in Figure 12b) of the cable 1 at right angles to the cable axis x. the position P is also shown on the pulley 4, the point where a free surface 13 which would have the shape shown in Figures 4a and 4b is in contact with the pulley P. This point is located at a distance dB cable 1 perpendicular to the cable axis x. The distance dB is less than the distance B, therefore, the turning of the hull is facilitated and hence the flipping section from the free surfaces is also facilitated. This applies in the case of the pulley of the invention but also in the case of any guiding device, particularly of the type allowing to change the orientation of the hull with respect to the rotation guiding device of the hull around the cable axis. In particular, the bevel support edge facilitates the reorientation of a hull in any guiding device for changing the orientation of the hull with respect to the rotation guiding device of the hull around the axis of cable (or channel) when the keel rests on a bearing surface of the guide device by the bearing edge. In other words, in particular the bevel bearing edge facilitates reorientation of the hull by any guiding device comprising a surface opposing the traction cable ducted during winding or during the wire unwinding. The invention works for example with guide devices for monitoring the cable in the event of lateral displacement and / or vertical cable. Generally, the presence of a beveled keel allows to limit the risks of deterioration of the shroud, especially in the presence of a double torsion facilitating the tilting of a hull to its input in a guide device, which limits the risk that the fairing from getting stuck in the guide device.

This embodiment is also advantageous in the case of a pulley having a constant profile, more particularly a pulley according to the invention. Indeed, the contact point P 'is located in a plane M' located at a distance D 'smaller than the distance D at which is located the plane M (including the point P) relative to the axis of the pulley, parallel to the cable axis x. Therefore, the pulley groove is shallower along the plane M 'that according to plane M. In fact, the profile of the groove in the plane M (or M') is the projection of the profile of the groove in a plane radial passing through the plane P (or respectively P ') on the plane M (or respectively M') forming an angle β (or respectively β 'inférieurà β) with the radial plane at the point considered. The fact that the groove is shallower along the plane M 'that according to plane M implies that the pulley is flatter along the plane M than along the plane M at least at the bottom (that is, ie at the central portion of the curve defining the groove). If the hull comes into contact on the central portion of the pulley tub bottom, the central portion is flat in the plane M 'and in the plane M, in other words, the radius of the contact surface at the point P is

important in the map M in the plane M, which facilitates the tilting of the hull under the traction of the cable end with respect to the axis of the pulley.

In the embodiment of Figure 12b, the beveled hull comprising the bevel 130a of the head section of the hull, that is to say the furthest hull of the cable end to be immersed. This facilitates the tilting of the free surface 130a when the cable winding and to facilitate tilting the entire section 120 as the hull, being connected in rotation around the cable to the other of the keel portion, it causes all the hulls section 120 in its movement around the cable. The head 130a is a keel hull adjacent to one another hull 130b belonging to the same section 120. The first bearing edge 130a of the head BZA hull is arranged so that the distance between the leading edge BAa and the first bevel bearing edge BZA continuously decreases along an axis parallel to the edge of BAa attack from a first end E1 of the first bearing edge BZA to a second end E2 of the first board 'furthest BZA support the other 130b buoyancy, that the first end E1, according to the axis parallel to the edge of BAa attack.

Alternatively, the beveled hull is the hull section of the tail, that is to say the hull nearest the end of the cable intended to be submerged. This facilitates the tilting of the hull during the unwinding of the cable (when the keel rests on the pulley of the other side of the pulley with respect to the axis of the pulley) and facilitate the changeover of the entire section for the hull (by propagation of the rotational movement of the entire section). The tail fairing is a keel which is adjacent to one another hull belonging to the same section. The first bearing edge is configured so that the distance between the edge of BAa attack and the leading edge of bevel support decreases, along the edge of BAa attack from a first end of the first bearing edge next to each other until a second free surface of the first bearing furthest edge of the other hull that the first end along the axis parallel to BAa. The other end of the first bearing edge is closer to a side face of the first end of the supporting edge. This embodiment, like the previous, ensures failover of all hull fairing sections without having to provide only the hulls

bevelled across the fairing, which would effectively limit the fairing of performance in terms of drag reduction.

Advantageously, each section comprises at least one end hull (head or tail) comprising a bevelled edge. Other hulls are not beveled hulls. They do not include first bearing edge bevel. The support edge is the trailing edge and is substantially parallel to the leading edge throughout its length. In a not claimed embodiment, a shroud comprising a single section as defined above may comprise a hull with a tapered abutment edge. This section extends for example over a length less than the length of the cable from the end intended to be submerged. In this case, the section of the head hull is preferably a fairing comprising a beveled support edge arranged as for the head of hull described above.

In another unclaimed embodiment, the section extends over the entire cable length.

In all fairing configurations (the type comprising a section, several segments or comprising all free keels in rotation relative to each other around the elongate member), all the hulls could be bevelled keels. This would facilitate the tilting of each hull breach of intercarène connection downstream of the hull to the pulley when the hulls are initially bonded. In case the keels are free in rotation relative to each other, this facilitates the tilting of each hull to arrive on a guide device More generally, the beveled hull avoids having to linking the hulls to each other and therefore can limit the costs of the fairing and fairing assembly time.

If we want to facilitate the reorientation of hulls in the event of cable winding, the bevel is formed so that the distance between the leading edge BA and the first beveled edge support decreases, along the axis xc since the end of the first closest support edge of the cable end to be immersed to the opposite end of the bearing edge at the end of the cable intended to be submerged and conversely if wishes facilitates tilting during wire unwinding.

In the embodiment of Figures 12a and 12b, the BAPA supporting edge is the trailing edge TE. Comprising the first tapered bearing edge BZA and a second bearing edge Bla which extends parallel to the x axis and is located at a fixed distance from the leading edge along the x axis. The first beveled edge support is connected to the lateral face 180 and the second bearing edge Bla, in the direction of the edge, by rounded connecting or chamfers. LC maximum chord length is the distance between this second Bla bearing edge and the leading edge. Alternatively, the supporting rim does not present a second support edge Bla extending parallel to the x axis. The bevel extends substantially over the entire width of the hull and is advantageously, but not necessarily, connected to the side faces by fillets or chamfers connection.

As seen in Figure 12c and 12d representing the hull sections according to respective planes N and Q, represented Figure 12a, parallel to the leading edge and perpendicular to the side faces 170, 180, the hull comprises a first thick portion 130a1 visible in Figure 12c and a second thin portion 130a2 having a second thickness e2 less than the first thickness e 1 of the thick portion. The second thickness e 2 is substantially equal to the thickness of the end of the shank 15 opposite the end of the shank 14 connected to the nose of the hull. The first edge comprises a first portion Bza1 extending in the first thick portion 130a1 of the hull and a second portion Bza2 extending into the thin portion. The first portion of the first bearing edge Bza1 is connected to the longitudinal sides 122, 123 by respective chamfers 132, 133 respectively. In other words, the hull comprises chamfer connecting the first portion of the first bearing edge Bza1 to the longitudinal faces 122, 123 respectively. This helps thin the trailing edge in the thick part of the hull and thus reduce the risk that the hull will come get stuck on the guide device. Alternatively, the chamfers extend along the entire length of the first bearing edge.

Alternatively, the first portion of the edge of Bza1 attack is connected to the side faces by respective bulging surfaces. By means swollen surfaces of the convex curved surfaces. This embodiment also allows limiting the thickness of the support board. Alternatively, the curved surfaces extend over the entire length of the first bearing edge.

The chamfers and curved surfaces are two non-limiting technical solutions allow to obtain the feature that at least a first portion of the first bearing edge Bza1 has a thickness e1 smaller than the thickness of the hull in any longitudinal plane parallel to the edge attack and perpendicular to the side faces of the hull intersecting the first portion of the first bearing edge Bza1. The thickness of the hull in a cutting plane is the distance between the first longitudinal side 122 of the second longitudinal side 123 in a direction perpendicular to the chord CO in the section of the hull plan. Advantageously, the first portion Bza1 has the same thickness as the second Bla support edge which extends parallel to the x axis and is located at a fixed distance from the leading edge along the x axis.

We now describe a support edge of a hull according to a second embodiment of the invention with reference to Figure 13. All that has been said about the implementation of the hull on a fairing configuration fairing, on the thickness of the supporting edge and on the arrangement between the first bearing edge and the second edge support remains valid.

In Figure 13, the bearing edge BAPB connects the two side faces

270, 280. The hull 230 is formed of two parts 231, 232 side by side along the first abutment edge Bzb bevel. The hull is configured to be maintained in an expanded configuration (visible in Figure 13), when subjected to the hydrodynamic flow of water, wherein the two parts 231, 232 are arranged, relative to each other around the first bearing edge, so that the hull has an edge parallel to the trailing edge and a constant section along the leading edge. In other words, the chord length is constant. The hull is maintained in the extended position until the pivot relative torque between the two parts about an axis formed by the first bearing edge Bzb is less than or equal to a predetermined threshold. The longitudinal direction of the first bearing edge is the direction of the axis formed by the bearing edge. The threshold is greater than the torque which can be exerted by the hydrodynamic flow of water on the hull when the hull is immersed and optionally towed along the axis trailing edge, leading edge. The hull is also configured to allow the relative pivoting between the two portions 231, 232 around the first bearing edge Bzb (see arrow), when pivoting relative torque between the two parts 231, 232, applied around the axis formed by the first bearing edge Bzb exceeds the threshold so that the hull end passes from the extended configuration to a folded configuration about the bearing edge. The axis formed by the first bearing edge is an axis contained in the first bearing edge and parallel to the longitudinal axis of the first bearing edge. In the folded configuration the hull does not have a constant section and the trailing edge is not parallel to the leading edge throughout its length. In the folded position, the hull is folded according to the first bearing edge Bzb. In the extended position, the hull is unfolded. This embodiment can limit or prevent the performance of reductions in terms of reduced hydrodynamic drag of the hull while facilitating the progression of the hull in the pulley and its upturn.

The first portion 231 extends from one side of the first bearing edge defined by the first bearing edge Bzb, the second bearing edge (if it exists) Blb, the leading edge BA, one face side 280 and the portion of the other side face 270 extending between the leading edge BA and the first bearing edge Bzb.

The second portion 232 is delimited by the first bearing edge Bzb, the portion of the first side face 270 extending from Bzb to the trailing edge TE and the portion of the trailing edge TE located between the first face and Bzb side 270.

The first part 231 is for example made of rigid material and the second portion 232 is made of flexible or soft material which does not substantially deform when pivoting relative torque between the two parts around the first bearing edge is less than or equal the threshold and that folds when the torque exceeds the threshold, in particular when the point of intersection between the trailing edge and the first side face 270 abuts against a guide device. The second part may, for example, be made of polyurethane. The first part may be made of polyurethane with a higher stiffness of the first part or POM or PET. Alternatively, the two parts have a stiffness such that they do not deform under the effect of a torque greater than the threshold, but are linked by a pivot link around the first bearing edge and the hull comprises a stabilizing device configured to hold the two parts in the extended relative position when the pivot relative torque is less than or equal to the threshold and so as to allow rotation between the two parts so that they pass in the folded relative position around the first edge support when the pair exceed the threshold. The coupling device is for example a device including a fuse or a compression spring.

Advantageously, at least one bevelled hull or each beveled keel is sized so as to be more resistant to a compressive force applied in a direction perpendicular to the leading edge connecting the leading edge and parallel to an axis to the trailing edge that other hulls of the respective section (not bevelled). This feature allows to limit the risk of deformation and fracture of hulls when engaging in the guide device, and turn and through this guiding device. To this end, this hull is for example made of a harder material than the other keels and / or it comprises ribs providing this extra reinforcement. Advantageously, the shroud comprises at least one bevelled end reinforced hull and cooperating with the fixing device. This reduces costs and possibly the weight of the shroud as the one or the hulls beveled Differ (es) of others, all the others being identical.

The invention also relates to an assembly comprising a vessel, the towing package being on board the ship. The ship is designed to move at a nominal speed with nominal sea state. The tow package is installed on the vessel so that the towing point is located at a nominal height.

CLAIMS

Shroud for shrouding an elongate object to be at least partially immersed, characterized in that it comprises a plurality of fairing sections (12), each shroud segment (12) comprising a plurality keels (13), the keel comprising a channel (1 6) for receiving the elongated object and being shaped so as to reduce the hydrodynamic drag of the elongate object at least partially immersed, said keels (13) being intended to be pivotally mounted on the elongate member around the longitudinal axis of the channel (1 6), said keels (13) being bonded together along the axis of the channel and being hinged together, the fairing sections (12) being free to rotate around the channel from each other.

Fairing according to Claim 1 wherein the hulls of the same shroud portion are interconnected by means of a plurality of individual coupling devices (19), each individual coupling device for connecting one of said keels section to another of said hull adjacent said hull section.

Fairing according to any one of the preceding claims, wherein the fairing sections have respective heights along the axis of the channel, defined according to the angular stiffness k of the respective fairing sections and according to the chord length LC of said keels said respective sections so as to prevent the formation of a complete twist on said respective sections.

Fairing according to any one of the preceding claims, wherein at least one fairing section has a height along the axis of the channel, set according to the angular stiffness k of said shroud portion and a function of the LC chord length of said said hull portion so as to prevent the formation of a complete air twist on said shroud section when the shroud segment is subjected to a torque of twisting or less equal to a predetermined torque.

5. A shroud as claimed in any one of claims 1 to 2, wherein at least one section has a height along the axis of the channel, set according to the angular stiffness k of said shroud portion, depending on the length of LC rope of said hulls of said section so that the portion is capable of undergoing complete and torsion so as to prevent the formation of a complete air twist on said shroud section when the shroud segment is subjected to a lower torque or equal to a predetermined torque.

6. A shroud as claimed in any one of claims 3 to 5, wherein the fairing sections have respective heights below a maximum height hmax such that:

p * k

where F is a constant between 250 and 500.

7. A shroud as claimed in any one of the preceding claims, wherein at least one section of said sections includes at least one end free surface, adjacent to one another belonging to said hull portion, being a beveled keel so that it has a support edge comprising a first bearing edge (BZA) bevelled relative to the leading edge (BA), the first bearing edge (BZA) being arranged so that the distance between the leading edge (BA) and the first bearing edge (BZA), taken perpendicular to the leading edge (BA), continuously decreases along an axis parallel to the leading edge, from a first end (E1) of the first support edge (BZA) to a second end (E2) of the first bearing edge (BZA) more remote from the other hull (130b) that the first end (E1) according axis parallel to the edge of attack.

8. A shroud as claimed in claim 7, wherein each beveled keel is an end hull.

9. A shroud as claimed in any one of claims 7 to 8, wherein the end free surface is dimensioned to be more resistant to a compressive force applied in a direction perpendicular to the leading edge and the connecting edge attack at the trailing edge, as the other hull of the section.

10. A shroud as claimed in claim 7, wherein the end free surface comprises two parts (231, 232) joined together along the first abutment edge (Bzb), the end free surface being configured to be maintained in a deployed configuration when subjected to the hydrodynamic flow of water, the two parts (231, 232) being arranged, relative to each other around the first bearing edge (Bzb), so that the end free surface has a trailing edge parallel to the leading edge (BA) and a constant section along the leading edge and configured to permit relative pivoting between the two parts (231, 232) about the first support edge (Bzb) when a torque relative pivoting between the two parts (231, 232) applied about an axis formed by the first bearing edge (Bzb) exceeds a predetermined threshold so that the hull of end moves from the deployed configuration to a configuration rep bound around the bearing edge.

January 1. Fairing according to any one of claims, wherein the supporting edge is the trailing edge.

12. ducted elongate element intended to be at least partially immersed, comprising an elongated member ducted by means of the fairing according to any one of the preceding claims, the elongate member being received in the channel (1 6), said keels (13) being pivotally mounted on the elongate member about the longitudinal axis of the channel (1 6) and being immobilized in translation relative to the elongate element along the axis of the elongate member.

13. Tow assembly comprising an elongate member ducted fan according to the preceding claim, and a towing device and handling designed to pull the elongate member ducted while the latter is partially immersed, the towing device comprising a winch (5) for of winding and unwinding the elongate member (1) ducted through a guide device (4) for guiding the elongate member (1).

14. Tow assembly according to the preceding claim, wherein the guide device (4) is configured so as to allow to modify the orientation of a hull (13a) of the shroud (12) relative to the guide device (4 ) by rotation of the hull (13a) about the axis of the elongate element (1) under the effect of the tension of the elongate element (1) relative to the guide device (4) when the keel ( 13a) has an orientation in which it rests on the guide device (4) and wherein the line of action developed by the elongate element (1) on the pulley (4) extends substantially along the axis extending from the axis of the elongate member to the trailing edge (BF).

15. Tow assembly according to the preceding claim, wherein the guide device including a first groove (24) whose bottom (26) is formed by the bottom of the groove of a pulley (4), the first groove (24 ) being delimited by a first surface (25) having a concave profile in a radial plane of the pulley, the width of the first groove and the curvature of the profile of the first curved surface in the radial plane being determined so as to allow to switch the hull, by rotation of the hull about the axis x of the elongate member under the effect of traction of the elongated member relative to the guiding device along its longitudinal axis from an inverted position wherein the hull trailing edge is oriented towards the bottom of the first groove, to an acceptable position in which it is orientated leading edge towards the bottom of the first groove.

6. Towing arrangement according to any one of claims 14 to 15, wherein the hull comprises a hull comprising a nose (14) receiving the elongated member and comprising a leading edge (BA) a shank (15) having a tapered shape extending from the nose (14) and comprising a trailing edge (BF), the first curved surface forming a first concave curve in the radial plane of the pulley, the first concave curve is defined in a radial plane (BB) of the pulley so that when the hull extending leading edge (BA) perpendicular to the radial plane (BB), whatever the position of a hull in the first groove (24), when the nose (14) of the hull (13) is supported on the first concave curve and that the elongate member (1) exerts on the hull (13) in the radial plane, a plating stress of the nose (14) of the hull (13) against the pulley, said Fp plating effort CP comprising a component perpendicular to the axis of the pulley and a lateral component CL the trailing edge (BF) of the hull (13) is not in contact with the first concave curve or is in contact with a portion (251) of the first concave curve forming, with a dp of the right radial plane perpendicular to the axis x extending from the axis x of the elongate member to the trailing edge of the hull, at an angle γ of at least one slip angle this. The slip angle is given by the following formula:

this = Arctan (Cf)

Where Cf is the friction coefficient between the material forming the outer portion of the tail of the hull and the material forming the surface delimiting the groove of the pulley.