EP4613627A1

EP4613627A1 - Underwater elements of a marine vessel and methods for mounting the underwater elements

Info

Publication number: EP4613627A1
Application number: EP24382246.7A
Authority: EP
Inventors: Carlos Manuel BLANCO SEIJO; Aitor RAMIL VIZOSO; Álvaro DEIBE DÍAZ; Jose Ramón MÉNDEZ SALGUEIRO
Original assignee: Navantia SA SME
Current assignee: Navantia SA SME
Priority date: 2024-03-07
Filing date: 2024-03-07
Publication date: 2025-09-10

Abstract

In one aspect, an underwater element of a marine vessel is provided. The underwater element is to be mounted on a marine vessel in a predetermined mounting orientation. The underwater element comprises a body with such a weight and volume that when the underwater element is in water, the buoyant force acting is between 80% and 120% of the gravitational force acting on the underwater element; and a mass distribution such that, in the predetermined mounting orientation of the body, the center of buoyancy and the center of gravity of are vertically aligned.

In a further aspect, a method is provided, for mounting an underwater element on a marine vessel afloat in a predetermined mounting position and a predetermined mounting orientation.

Description

The present disclosure relates to underwater elements of a marine vessel and methods for mounting the underwater elements.

BACKGROUND

Periodically, marine vessels need maintenance or, in case of damage, repair of hull elements.
Maintenance includes maintenance of the hull, the propeller, the rudder and any parts which are immersed in water and are normally inaccessible by the marine vessel's crew when the marine vessel is operative (e.g., at sea).
Maintenance and / or reparation of marine vessel is usually carried out in dry-docks. A dry-dock is a structure that can be flooded to allow a marine vessel to be floated in, then drained to allow the marine vessel to rest on a dry platform. As a result, maintenance and / or reparation of a marine vessel element such as a piece of the hull of the marine vessel or any underwater element of the marine vessel can be carried out.
For changing a part of the marine vessel such as a fairwater or any other underwater elements, marine vessels have to be dry-docked, e.g. because these elements cannot be handled by divers. Dry-docking implies sailing to a dry-dock and putting the marine vessel out of service and ceasing all activities carried out via the marine vessel.
Furthermore, dry-docks have limited availability, which may lead to further delays just to get the marine vessel into the dry-dock.
When dry-docking is being carried out, resting the marine vessel on the dry platform is a critical step. If done incorrectly, there may be unexpected repairs which further delay the time in which the marine vessel is in dry-dock. In addition, maintenance and / or repairs have to be carried out by a specialized workforce, which increases the cost of dry-docking the marine vessel. While the marine vessel is in dry-dock, the crew has to be paid but cannot perform their regular duties during the time required for maintenance or repairs. Consequently, dry-docking a marine vessel is a high-cost operation.
In summary, nowadays changing an underwater element such as a fairwater involves dry-docking the marine vessel, which is a time consuming, expensive process that has to be carried out by a specialized workforce.
Examples of the present disclosure seek to reduce at least partially one or more of the aforementioned problems.

SUMMARY

In a first aspect, an underwater element of a marine vessel is provided. The underwater element is to be mounted on a marine vessel, e.g. attached to a marine vessel element, in a predetermined mounting orientation. The underwater element comprises a body. The body has a weight and a volume such that, when the underwater element is in sea water, a buoyant force acting on the underwater element is between 80% and 120% of a gravitational force acting on the underwater element; and a mass distribution such that, in the predetermined mounting orientation of the body, the center of buoyancy and the center of gravity of the body are vertically aligned.
By virtue of this configuration, the body of the underwater element, when released into water, for example in the sea, floats or remains near the water surface; and the body adopts the predetermined mounting orientation, by virtue of the specific mass distribution that has been given to the body of the underwater element.
This allows heavy underwater elements of a marine vessel, such as a fairwater, to be released into the water in the vicinity of a marine vessel that is afloat, and to be effortlessly conveyed and mounted at a target position of the submerged hull, without the need of dry-docking the vessel.
The present disclosure takes advantage of the physical principle that a body submerged in water, once it reaches a state of equilibrium, adopts a certain orientation, that depends on its mass distribution: more specifically, it adopts the orientation in which the center of gravity of the body and the center of buoyancy of the body are vertically aligned.
This physical principle is used in the present disclosure to design the body of the underwater element, and in particular its mass distribution, in such a way that its center of buoyancy and its center of gravity are vertically aligned when the body is in a predetermined desired orientation, suitable for assembling the underwater element at a mounting or target position of the vessel. As a consequence, once the underwater element is submerged in water, the body tilts and/or turns until its center of buoyancy and center of gravity align vertically, whereby the body adopts the predetermined mounting orientation for which it was designed. There is no need to exert a large force on the body to tilt or rotate it towards the correct mounting orientation with respect to the intended target on which it has to be mounted, because this orientation is known and is used to design the body, so the body automatically adopts the predetermined mounting orientation when it is in sea water.
The predetermined mounting orientation may be a predetermined angular orientation of the body of the underwater element. The angular orientation of the body may be understood as the angle or the angles (e.g. according to cartesian coordinates) between the surface of the water and the body of the underwater element.
The mass distribution of the body may be designed such that the center of buoyancy coincides with or is above the center of gravity. As a result, there is no restoring moment acting on the underwater element. Consequently, not only the body adopts the predetermined mounting orientation when it is submerged in the water, but this orientation corresponds to a situation of stable equilibrium.
In practice, after the underwater element is brought into contact with water, e.g. released or plunged into the sea or other body of water, a diver may displace the underwater element to a target position of the marine vessel. Since the body of the underwater element adopts the predetermined mounting orientation when submerged in water, the underwater element may be easily mounted on the marine vessel, as the underwater element is already in the suitable orientation for being fitted on the marine vessel. Therefore, dry-docking the marine vessel for changing or mounting an underwater element of the marine vessel is no longer required. As a result, repairs or maintenance such as changing an underwater element, may be carried out while the marine vessel remains operative. Furthermore, such repairs or maintenance may be carried out by divers instead of a specialized workforce such as mechanics, welders or a dry-docking crew.
In some examples, the weight and the volume of the body of the underwater element may be such that the buoyant force is between 100% and 120% of the gravitational force. Therefore, by selecting the buoyant force to be only slightly greater than the gravitational force, the underwater element, when submerged in water, has a neutral or slightly positive buoyancy, so it tends to float and not sink, but at the same time it may be easily displaced to the target position without the diver having to exert excessive effort.
In some examples, the body of the underwater element may comprise an internal cavity. The internal cavity may be provided within the body of the underwater element. In some examples the cavity may be an open cavity, in fluid communication with the outside of the body (e.g., water such as sea water, the surrounding environment of the underwater element, etc.). In some of these examples, the body may comprise a closing element for closing the open cavity. In these examples, the cavity may be configured to receive a load or to be filled with water.
In examples, the cavity may be designed such that the body of the underwater element meets the two above conditions, for floating near the surface of water and for adopting the predetermined mounting orientation once the cavity is loaded with a load or filled with water.
The underwater element comprising the cavity may thus be lighter than a solid underwater element, more easily transportable or storable, and the cavity may be filled shortly before use.
In some examples, the body of the underwater element may comprise two or more regions, with a density of the material in the first region being higher than a density of the material in the second region. Consequently, the mass distribution of the body may be adjusted to meet the above condition that the body adopts the predetermined mounting orientation, while at the same time the body may have the shape and volume required by its function.
In some examples, the underwater element may be formed by two or more bodies. The bodies forming the underwater element may all have substantially the same external shape, or substantially symmetrical external shapes, and substantially the same volume. However, the mass distribution of each body, e.g., of a first body and of a second body, may be adjusted such that, once the first body and second body are in water and the center of buoyancy and the center of gravity align vertically for the first body and for the second body, the first body adopts a first predetermined mounting orientation while the second body adopts a second predetermined mounting orientation, because the mass distribution of the first body is different from the mass distribution of the second body. For example, the first predetermined mounting orientation may be tilted or rotated relative to the second predetermined mounting orientation.
Adjusting the mass distribution of each body of the underwater element may be achieved by providing a cavity in the two or more bodies, which may be selectively filled or loaded. For example, the cavity of the first body may be filled or loaded, while the cavity of the second body is not filled or loaded, this resulting in two bodies with different mass distributions and, therefore, different predetermined mounting orientations.
In some examples, a first body of the underwater element may comprise a cavity, and a second body of the underwater element may comprise no cavities, or may comprise a cavity with a different shape, volume, and/or position from those of the cavity of the first body.
In some examples, the body or the bodies of an underwater element may each comprise two or more cavities, and each cavity may be either loaded or left empty, e.g. after manufacturing the bodies and before releasing them into water, in order to adjust the mass distribution and the orientation adopted by the body when submerged in water.
This allows underwater elements, such as fairwaters, that may comprise two bodies with the same external shape and volume, to be designed in such a way that once the first and second bodies are in sea water, and their centers of buoyancy and centers of gravity align vertically, the two bodies adopt different predetermined mounting orientations.
In one example, a fairwater may be formed by two bodies that are manufactured with substantially the same external shape and with substantially the same volume, and e.g. with the same open cavities. As manufactured, the fairwater comprises two identical or similar bodies that will float and be in the same predetermined mounting orientation when released into the water. As a result, the two bodies as manufactured cannot match with each other and the fairwater cannot be assembled (as if there were two right-hand parts). However, selectively filling or loading a cavity of the first body differently from the cavity of the second body results in a different mass distribution between the two bodies and, therefore, a different orientation when they are in the water. As a result, it may be achieved that when the first body and the second body are fully immersed in water and their respective centers of buoyancy and centers of gravity align vertically, the first body adopts a first orientation while the second body adopts a second, different orientation because the mass distribution of the first body is different from the mass distribution of the second body. Consequently, the two bodies may be e.g. a right-hand part and a left-hand part of the fairwater, each in the correct orientation to be assembled to the vessel and to each other.
Therefore, manufacturing and storage may be facilitated as the bodies forming the underwater element may be manufactured substantially identical.
In some examples, the mass distribution of each body of the two or more bodies may be adjusted, alternatively or additionally to filling a cavity, by attaching weights to the bodies, in a suitable position on each body, after manufacture and before their release into water. Mass distribution may also be adjusted by forming the bodies with different materials in different regions (leading to regions with a higher or a lower density). Other alternative or additional solutions for adjusting the mass distribution may be bodies formed by the same material with different densities of the materiel (i.e., solid material or carved material), or cavities may be provided in regions of the body and not in another region, or any combinations of the disclosed examples.
Providing bodies with one or more cavities allows obtaining a lightweight underwater element, more easily transportable and/or storable, compared with an underwater element with one or more solid bodies.
In some examples, the bodies forming the underwater element may be configured with matching guiding or self-alignment features to facilitate assembly of the bodies to each other, such as a conical pin and an opening, or others. In some of these examples, the first body may comprise an opening and the second body may comprise a protrusion for insertion into the opening of the first body such that the first body is fixedly coupled to the second body.
In some examples, the underwater element of the marine vessel may be a fairwater. The fairwater may be configured to be mounted over a drive shaft or propeller shaft of the marine vessel. The fairwater may comprise two matching bodies, allowing the fairwater to be easily mounted around the drive shaft.
By virtue of the configuration disclosed in examples herein, the bodies of the fairwater, when released into the water, float or remain near the water surface and adopt suitable predetermined mounting orientations, achieved as disclosed by adjusting the mass distribution of each body of the fairwater.
This allows installing a fairwater about a bearing arranged on a drive shaft of the marine vessel by a simple operation, involving divers who effortlessly convey and mount the fairwater parts at the target position of the submerged hull. In case of a hit resulting in a damaged fairwater, the damaged fairwater may therefore be changed at sea, without the need of dry-docking of the marine vessel.
In a further aspect, a method is provided for mounting an underwater element in a predetermined mounting or target position and in a predetermined mounting orientation on a marine vessel, with the marine vessel being afloat. The method comprises providing the underwater element which comprises a body, wherein the body has a mass distribution such that, in the predetermined mounting orientation of the body, the center of buoyancy and the center of gravity of the body are vertically aligned. The method further comprises submerging the underwater element in the water in a vicinity of the marine vessel; displacing the underwater element to a target position of the marine vessel; and mounting the underwater element on the marine vessel at the target position.
By virtue of the configuration of the mass distribution of the underwater element, causing the underwater element to adopt the predetermined mounting orientation when submerged, the underwater element may be easily mounted by divers on the marine vessel hull at the target position, without requiring from the divers an effort to tilt or rotate the underwater element to a suitable mounting orientation of non-equilibrium, and to maintain this orientation until it is attached to the hull.
Therefore, no dry-docking of the marine vessel is required for mounting the underwater element of the marine vessel. As a result, the method may be carried out while the marine vessel remains operative. Furthermore, mounting of the underwater element may be carried out by divers instead of a specialized workforce such as mechanics, welders, or a dry-docking crew.
The underwater element may be mounted at the target position on the vessel while the vessel is afloat, e.g. anchored at a port, or even at sea. The vessel may carry underwater elements as spare parts in case they need to be changed, or an underwater element may be transported to the vessel location, when needed.
The body of the underwater element may be configured as disclosed in any of the examples of the present disclosure, e.g. such that a buoyant force is between 80% and 120% of the gravitational force. In examples, it may also be configured with a weight and volume such that the underwater element has a neutral or a slightly positive buoyancy, e.g. the buoyant force may be between 100% and 120% of the gravitational force. This further facilitates the mounting operation, because the step of displacing the underwater element to a target position of the marine vessel may be safely performed, without the risk of the underwater element sinking, but without requiring that the divers exert high forces to displace it vertically or horizontally in the water.
In some examples, providing the underwater element may comprise providing two bodies for forming the underwater element. The two bodies may be configured as disclosed in any of the examples of the present disclosure. Mounting the underwater element on the marine vessel at the target position may comprise arranging the first body at a first target position and arranging the second body at a second target position. The method may further comprise assembling the first body and the second body to each other to complete the mounting of the underwater element on the marine vessel.
In some examples, the underwater element is a fairwater, and mounting the underwater element on the marine vessel at the target position may comprise arranging the body or bodies of the fairwater around a propeller shaft or drive shaft of the marine vessel. Therefore, it is possible to install a fairwater about a bearing arranged on a drive shaft of the marine vessel by a simple operation involving divers who displace and mount the fairwater to a target position, without the need of dry-docking of the marine vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

Figs. 1 is a schematic view of an underwater element according to an example of the present disclosure;
Figs. 2a, 2b, 2c are schematic views of an underwater element according to examples of the present disclosure;
Figs. 3 (3a, 3b), 4 (4a, 4b, 4c) and 5 schematically represent underwater elements, particularly fairwaters, according to examples of the present disclosure;
Fig. 6 schematically represents a method for mounting an underwater element to a marine vessel afloat according to an example of the present disclosure;
Fig. 7 schematically shows a block diagram of a method for mounting an underwater element to a marine vessel afloat according to an example of the present disclosure; and
Fig. 8 schematically shows a block diagram of a method for mounting a fairwater to a marine vessel afloat according to an example of the present disclosure.

Non-limiting examples of the present disclosure will be described in the following, with reference to the appended drawings, in which:

DETAILED DESCRIPTION OF EXAMPLES

In the figures, the same reference signs have been used to designate similar elements.
The present disclosure is concerned with examples of underwater elements of a marine vessel, such as fairwaters, grills, or other, and especially underwater elements that may need to be installed or changed at a target position of the submerged part of the vessel.
Fig. 1 shows a very schematic view of a generic underwater element 1, to illustrate features of the present disclosure.
In fig. 1 the underwater element 1 comprises a body 2. The body 2 of the underwater element 1 has a weight or mass, a volume, and a mass distribution.
When a body is placed in water, as known, the body is subject to a downward gravitational force Fg resulting from its mass, and also to an upward buoyant force Fb, which according to Archimedes' principle is equal to the weight of the water displaced by the body. Depending on the balance between the two forces, the body tends to sink or tends to float.
The mass of the body 2 is: $m = \int ρ (x) dV$ where V is the volume, and ρ is the density function in the body 2. The density function depends on the materials forming the body 2 and on their geometric distribution in the body 2.
Referring to the mass distribution, the mass distribution of the body 2 of the underwater element 1 defines the center of mass 52 of the body 2, which for the underwater elements of the present disclosure coincides with the center of gravity.
The center of mass or center of gravity 52 of the body 2 is: $r_{cm} = \frac{1}{m} \int r ρ (x) dV$ where r is the position vector, r_cm is the position vector of the center of mass 52, m is the mass of the body 2, V is the volume, and ρ is the density function as defined above.
The gravitational force (Fg) 50 acting on the body 2, applied at the center of mass 52 is: $F_{g} = mg$ where m is the mass of the body 2, and g is the acceleration due to gravity.
The center of buoyancy of a body is the center of mass of the volume of water that the body displaces, and it is the geometric point through which the resultant buoyant force Fb on the immersed body is assumed to act.
The center of buoyancy 42 of the body 2 is: $r_{cb} = \frac{ρ_{w}}{m_{w}} \int rd V_{s}$ where r is the position vector, r_cb is the position vector of the center of buoyancy 42, m_w is the mass of displaced water, ρ_w is the density of water, and V_s is the volume of the submerged portion 3 of the body 2. The center of buoyancy 42 is the point at which the buoyant force (Fb) 40 acts on the submerged portion 3.
The buoyant force (Fb) 40 applied at the center of buoyancy 42 may be defined as: $F_{b} = - m_{w} g$ where m_w is the mass of displaced water, and g is the acceleration due to gravity.
The buoyant force Fb depends on the density of the water. The density of surface sea water varies depending e.g. on temperature and salinity, ranging between about 1020 and1029 kg/m³, with an average of about 1025 kg/m³; in the present disclosure, for the purpose of determining buoyant forces and floatability, the density of sea water is considered to be 1025 kg/m³.
It may be noted that that the buoyant force 40 and the gravitational force 50 act along g but in opposite directions.
For the underwater element 1 to float in water 20, the buoyancy force has to be equal to or greater than the gravitational force, so the resultant force on the body is zero, or is upwards (neutral floatability or positive floatability, respectively); the condition the forces have to meet for the underwater element to float is therefore: $|F_{b}| \geq F_{g}$
In the present disclosure, the weight and the volume of the body 2 are designed in such a way that when the underwater element 1 is released into water 20, for example sea water, the buoyant force 40 acting on the underwater element 1 is between 80% and 120% of the gravitational force 50 acting on the underwater element 1. In other words, the body is designed to have a buoyancy that is relatively close to neutral: when submerged in water it will tend to slowly rise and remain at the surface, if designed with slightly positive floatability, or slowly sink, if designed with relatively negative floatability, or remain at the depth where it is placed, if designed with neutral floatability.
Furthermore, the body 2 may be easily displaced underwater, both horizontally and vertically, e.g. by divers, that need to exert only relatively small forces.
In some examples, the body 2 may be designed with a floatability very close to neutral, i.e. with the buoyant force 40 between 95% and 105% of the gravitational force 50, such that the body may tend to remain suspended at any depth at which it is placed, without rising or sinking, unless subject to outer forces such as waves or impacts.
In some examples, the body 2 may be designed with a floatability that is slightly positive, e.g. with the buoyant force 40 between 100% and 120% of the gravitational force 50, or with the buoyant force 40 between 100% and 110% of the gravitational force 50; this reduces the risk of the body sinking, for example if subject to external forces.
The floatability is also configured for each particular underwater element 1 according to the present disclosure, such that the force a diver needs to exert on the body 2 for taking it from the water surface to the assembly position on the hull is within a diver's physical abilities: a diver should need to exert less than 20 kg, and preferably less than 10 kg, usually downwards (when the floatability is slightly positive), or possibly upwards (if the floatability is slightly negative).
For example, a body 2 having a weight and gravitational force Fg of 100 kg may be configured to have a buoyant force Fb of 108 kg (108% of Fg), such that a single diver may handle the body by pulling it downwards in the water with a force of 8 kg.
A heavier body 2, for example having a weight and gravitational force Fg of 400 kg, may be configured to have e.g. a buoyant force Fb of 12 kg (103% of Fg), to be handled by a single diver exerting a force of 8 kg, or it may be configured to have e.g. a buoyant force Fb of 420 kg (105% of Fg), to be handled by two divers each exerting a force of 10 Kg; many other configurations are possible.
In practice, when designing a body 2 of a specific underwater element 1, the weight of the body as well as the number of divers foreseen in the handling of the underwater element may be taken into account, such that the force needed to displace the body in sea water may be tailored to enable the divers to perform the operation safely and with a reasonable effort.
In fig. 1, the underwater element 1 comprising body 2 is depicted in a condition of stable equilibrium, in which the resultant of the forces and torques on the body is zero; that is, in the position and orientation the body 2 naturally adopts once it is released in water; and to which the body 2 tends to return, if it is displaced from this position and orientation by external forces.
In this example, the position of stable equilibrium the body adopts is partially immersed in the water 20, with a portion 3 that sinks below a surface 22 of the water 20 and a portion 4 that remains above the surface 22 of the water 20. The waterline 30 is the imaginary line dividing the submerged portion 3 from the portion 4 above the surface 22.
The body 2 adopts this position with respect to the surface because in this position the volume of the portion 3 that is submerged is such that the weight of water it displaces causes a buoyant force that equals the gravitational force caused by the weight of the body 2.
Furthermore, in a condition of stable equilibrium the center of buoyancy 42 and the center of gravity 52 of the body 2 are aligned along the direction of g, i.e., along a vertical axis 80. The buoyant force Fb and the gravitational force Fg are therefore on the same vertical line of action, as shown in fig. 1, and the resultant torque acting on the body 2 is therefore zero: the body has no tendency to rotate or tilt in the water.
In summary, when a body of any shape is released in water it naturally adopts a certain stable position with respect of the surface of the water, in which the resultant force on the body is zero; and a certain stable orientation in the three-dimensional space in the water, in which the resultant torque on the body is zero. If the body is displaced from this state of equilibrium by exerting an external force on the body, it will tend to return to the same position and orientation.
The orientation of a body in the three-dimensional space is the angular orientation of the body about the three horizontal cartesian axes. However, only the angular orientation about the two horizontal cartesian axes is relevant in this case, because the buoyant and the gravitational forces cause no torque about the vertical cartesian axis.
The orientation naturally adopted by the body when placed in water, with the centers of gravity and buoyance vertically aligned, depends on the mass distribution of the body. This principle is used in the present disclosure to purposively configure the body 2 of the underwater element 1 with a specific mass distribution that results in the centers of gravity and buoyance of the body 2 being vertically aligned when the body is an orientation in the three-dimensional space that is particularly suitable for handling and mounting the body on a marine vessel afloat, in sea water. This orientation is referred to herein as the predetermined mounting orientation 60 of the body 2. Consequently, when the body 2 is released in sea water it spontaneously adopts the predetermined mounting orientation 60; if it is displaced from this stable equilibrium by an external force, it will tend to tilt (about one or two cartesian axes) to return to the same orientation.
The size and outer shape of a body of an underwater element will generally be conditioned by its function. However, according to the present disclosure, in order to provide the body with the desired floatability and suitable orientation of stable equilibrium in sea water, it is possible to adjust in several ways the inner shape and the mass distribution of the body. For example, the body may be designed with hollow parts, and/or using materials of suitable densities for manufacturing the body, e.g. lightweight materials such as polymers, as well as purposively arranging materials of suitable densities across the body. Moreover, weights may be provided inside the body and/or attached to the body. Other solutions, or combinations of different solutions, are also possible.
For a body of an underwater element having a certain external shape and, and knowing the floatability and the predetermined mounting orientation that are desired for the body, there are several techniques to determine the mass distribution of the body that is suitable for achieving that the center of buoyancy and the center of gravity be vertically aligned when the body is in the desired orientation: e.g. mathematical modelling using computer-implemented methods, such as finite elements method (FEM).
In the following, some of the possibilities for configuring a body of an underwater element are disclosed in more detail, by way of example.
Fig. 2a shows a very schematic view of the underwater element 10, to illustrate features of the present disclosure.
In fig. 2a, the body 12 of the underwater element 10 comprises two regions 18a, 18b, with a density of the material of the body 12 in the first region 18a is higher than a density of the material of the body 12 in the second region 18b.
In the figures, parts with a higher density of material, such as region 18a, are shown by dash-dotted lines, while parts of lower density, such as region 18b, are shown white.
By selecting the volume and shape of the regions 18a, 18b, and the density of the material or materials forming said regions, the mass distribution of the body 12 of the underwater element 10 may be adapted so that the center of buoyancy 42 and the center of gravity 52 of the body 12 are vertically aligned in the predetermined mounting orientation of the body: when in water, the body 12 will therefore adopt this desired orientation.
Furthermore, the weight and volume of body 12 are configured so that the buoyant force 40 is between 100% and 110% of the gravitational force 50 (neutral or slightly positive floatability), so the body 12 floats as shown in fig. 2a. In other examples, the body 12 may be configured to have a slightly negative floatability.
In some examples, a body of an underwater element may comprise one or more cavities, either enclosed within the body, or in fluid communication with the environment surrounding the underwater element, such as the sea water. A closing element may be provided for closing this kind of open cavities and isolating them from the environment. Cavities, especially open cavities, may be configured to receive a load, or to be filled with water.
Cavities are defined herein as hollow spaces inside a mass of the material forming a body, which are larger than the pores of the material itself, e.g. at least 100 times larger than the pores of the material. In examples, the volume of a cavity may be of at least 10 cm³, or of at least 100 cm³, or of at least 1000 cm³.
Cavities, especially open cavities that can be selectively filled or be left empty, may be useful for altering the mass distribution of the body of the underwater element: an empty cavity reduces the density of the region of the body where it is placed, while a cavity filled with a heavy material, e.g. ballast, may increase the density of the region of the body where it is placed. Therefore, cavities may be useful to configure the body of an underwater element two be able to adopt two or more different predetermined mounting orientations, wherein the stable equilibrium position and orientation adopted by the body when released in sea water depends on how the cavities have been selectively filled or left empty.
Fig. 2b and 2c illustrate examples of how cavities may be used in this regard. They show an underwater element 101 with a body 121, with the same outer shape as the body 12 of the underwater element 10 of fig. 2a. Like in fig. 2a, the body 121 may have a weight and a volume providing neutral or slightly positive floatability, and two regions where the material of the body has different densities.
In fig. 2b, the body 121 of the underwater element 101 comprises the first region 181a and the second region 181b, where the density of the material of the body 121 in the first region 181a is greater than the density of the material of the body 121 in the second region 181b. However, in the example of fig2b the body 121 of the underwater element 101 comprises an internal cavity 90, within region 181b, which is empty, i.e., it is filled with air. With this configuration, the mass distribution of body 121 is different from that of body 12 of fig. 2b, and the body 121 will tilt slightly, as indicated by arrow A, to adopt a stable equilibrium orientation that will be slightly different from that of the body 12 in fig. 2a, even though both bodies have the same outer shape.
Fig. 2c shows the same underwater element 101 and body 121, of fig. 2b; however, in this case the cavity 90 has been filled with a load 91, for example a heavy bulk material of the kind usually employed as ballast, like gravel or any other, or filled with water. The load inside the cavity 90 increases the overall density of region 181b: depending on the materials of the body 121, the size of the cavity 90, and the load 91, the increase in density and mass due to the presence of load 91 may alter the mass distribution of the body 121 to the point that stable equilibrium corresponds to a completely different orientation from that of fig. 1. The stable orientation in this case may be for example as shown in fig. 2c: rotated by about 180° with respect to fig. 2a.
In figures 2b and 2c, only the orientation of the body 121 in the plane of the drawing, i.e, only around one horizontal axis perpendicular to the drawing, has been discussed. However, it will be understood that the same principle may be applied if the body of an underwater element has to be oriented in two planes in the three-dimensional space, i.e., around two cartesian axes.
Different loads 91 may be employed to fill the cavity 90, e.g. water or metal beads, each providing a different mass distribution to the body 121, to allow obtaining different desired predetermined mounting orientations. Furthermore, the body 121 may be provided with several cavities, of several sizes or shapes and in different parts of the body 121, to be selectively filled.
Thus, an underwater element with a desired outer shape may be caused to adopt two or more different predetermined mounting orientations, as may be required, by simply providing cavities in a body of the underwater element, and by selectively filling the cavities as convenient. This may be useful, for example, if the same underwater element may need to be mounted on a marine vessel in different orientations; or when an underwater element is formed by two bodies (e.g. left and right or up upper and lower) to be assembled to each other enclosing a part of the vessel, and therefore have to be in different mounting orientations during assembly. An example of an underwater element for which this may be useful is a fairwater, that may be formed by two generally semi-cylindrical bodies to be assembled around a propeller shaft that may be inclined an angle with respect to the horizontal.
In examples according to the present disclosure, an underwater element may comprise two or more bodies, in general to be assembled to each other and to the marine vessel, such as a fairwater. Each body may be configured as described herein to adopt a predetermined mounting orientation.
In the following, with reference to figures 3 to 5, examples of fairwaters are described. These fairwaters are examples of underwater elements according to the present disclosure, generally comprising two bodies.
Fig. 3 and fig. 4 (including figs. 3a, 3b, 4a, 4b, 4c) schematically represent example fairwaters 200, 300 to illustrate features of the present disclosure. In each of Figs. 3 and 4, the fairwater comprises two bodies 210, 212 and 310, 312. In other examples, the fairwater may comprise more than two bodies. In other examples, the fairwater may comprise a single body, e.g. a body with two relatively symmetrical parts and a hinge part joining them.
The external shape of bodies 210, 212 and 310, 312 of fairwaters 200 and 300 in figs. 3 and 4 is substantially the same and comprises a generally channel shape, i.e. with a generally U-shaped cross section, with a central web region and with a leg region encompassing the two walls or legs on either side of the web region.
In practice, the outer shape of the bodies is configured according to the function of the fairwater, and to allow the two bodies to be assembled to each other and around the propeller shaft and bearing. In other examples, the two or more bodies forming a fairwater may have different external shapes. For example, the bodies of fairwaters as disclosed herein may each have a semi-frustoconical shape, to form a fairwater that is at least partly frustoconical, rather than cylindrical as schematically depicted in the figures.
In the examples of fig. 3 and in fig. 4 each body may be configured such that the density of the body in the web region is different from the density of the body in the leg region. The mass distribution resulting from this difference in density between the two regions of a body causes each body to adopt a predetermined orientation when submerged in sea water.
In the example of fig. 3a, each of the two bodies 210 and 212 is a solid part, either made using different materials for different regions or using the same material but with different density, e.g. different porosity, in different regions. In the figure, parts with a higher density of material are shown by dash - dotted lines, while parts of lower density are shown white.
In fig. 3a the bodies 210 and 212 have the same overall external shape, but the regions of higher density are not the same in the two bodies, and therefore body 210 has a different mass distribution from that of body 212. In one example, body 210 is configured with a web region 220 of lower density and a leg region 222 of higher density, and body 212, on the contrary, is configured with a web region 220 of higher density and a leg region 222 of lower density.
Since the two bodies 210 and 212 have different mass distributions, when submerged in sea water they will adopt different orientations: as shown in the figure, body 210 will tend to float with its higher density leg region 222 at the bottom, while body 212 will tend to float in the opposite orientation, with its higher density web region 230 at the bottom.
It will be understood that by further adjusting the mass distribution within the bodies (e.g. by a higher density towards one end of the length of the body), it is also possible to cause them to tilt a certain angle around an axis perpendicular to the drawing.
The mass distribution of each body 210, 212 may thus be configured such that the bodies 210, 212 tend to adopt orientations that bring them to face each other when submerged in sea water, as shown in fig. 3a. As a result, once the bodies 210, 212 are released into the water in the vicinity of a marine vessel they can be handled by divers, to be displaced to a target position and easily assembled around a propeller shaft.
In another example, shown in fig. 3b, the difference in density may be achieved by manufacturing the bodies of a fairwater with the same material and substantially uniform material density and with cavities in some regions, e.g. at least one region, such that the density of the body is lower in these regions. In fig. 3b, two bodies 210' and 212' of a fairwater 200', which are identical in external shape to bodies 210 and 212 of fig. 3a, are made of the same material, of uniform material density, and with internal, enclosed cavities, formed inside the material of the bodies and suitably arranged in each body such that the body tends to adopt the desired orientation when submerged. For example, in order to adopt the orientations shown in fig. 3b, body 210' may have an enclosed cavity 240' along the center of the web region 220', while body 212' may have cavities 241' and 242' towards the free ends of the legs in the leg region 232'.
In further examples (not shown), the different mass distributions causing the bodies to adopt the desired predetermined mounting orientations may be achieved by using weights or loads in some regions of the bodies, e.g. weights to be attached to the outer surface of the body.
In one such example, in order to make the bodies 210, 212 float in the predetermined orientations of figs. 3a and 3b, the leg region 222 of body 210 may include an enclosed or attached weight, e.g. towards the free end of the legs; while web region 230 of body 212 may include an enclosed or attached weight, e.g. along the central part of the web. In the case of weights to be attached to the surface of the body, the body may be configured with suitable seats or attachment fixtures, to receive and securely attach a weight.
A weight is defined herein as a solid object, e.g. in the shape of a plate, a rod, a tube, a block, etc., in general made of a material that is heavier than the material of the bodies of the fairwater, for example a metal or alloy such as lead, brass, stainless steel, bronze, or others, when the bodies are made of a polymer. On the other hand, a load of the kind to be used to selectively fill open cavities of a body of a fairwater, is defined herein as a bulk material, such as water, sand, gravel, metal beads, or the like, such as bulk materials commonly used as ballast.
In figs. 4a, 4b, 4c another example fairwater 300 is shown, similar to fairwater 200 of fig. 4 in that it comprises two bodies 310, 312 with the same overall external shape, with body 310 comprising a web region 320 and a leg region 322, and body 312 comprising a web region 330 and a leg region 332.
Contrary to fig. 3, however, in the examples of fig. 4 it is foreseen that the two bodies 310 and 312 of fairwater 300 both have the same mass distribution, for example with the same cavities, as shown: body 310 comprises cavities 340 and 341 in leg region 322, and body 312 comprises inner cavities 342 and 343 in the corresponding leg region 332. Thus, the two bodies are substantially identical. This has the advantage that a smaller number of bodies needs to be manufactured, transported and stored, as each body may serve as upper/lower body or right/left body of the fairwater. For example, only one body needs to be provided and stored in a marine vessel, instead of two, to allow repairing the fairwater in case of damage to one of the bodies caused by an impact.
However, as shown in fig. 4a, the bodies 310, 312 if submerged in sea water, would tend to adopt the same orientation, in both cases with the denser web portions 320, 330 at the bottom: this means that in order to mount the fairwater around the propeller shaft of a marine vessel, one of the bodies would need to be rotated under water and forced into an unstable orientation, and then maintained in this orientation during assembly, which may require forces that divers cannot exert.
In order to benefit from a reduction in the number of bodies to be stored, and still retain the advantage of facilitating the operation of mounting the fairwater to the marine vessel, or replacing one of the bodies of the fairwater, while the vessel is at sea, the mass distribution of the two bodies 310 and 312 may be altered before use, such that the mass distribution of body 310 and the mass distribution of body 312 are different, as required for their suitable orientation.
For example, cavities 340, 341, 342, 343 may be configured as open cavities, with an opening 349 in fluid communication with the outside of the body 310 or 312, i.e., with any surrounding environment such as air or water. Only the openings 349 of cavities 340 and 342 are visible in fig. 4a. Openings 349 allow each cavity 340, 341, 342, 343 to be selectively filled with a load at any time before use.
As a result, in a final configuration of use, the bodies 310 and 312 of fairwater 300 may have different mass distributions, simply by filling only some of the cavities 340, 341, 342, 343 with a load, while others are left empty. Each opening 349 may have a corresponding closure element 350 (see fig. 4c) to isolate the corresponding cavity from the environment and prevent the load from flowing out.
Fig. 4b and fig. 4c, wherein fig. 4c is a cross section along the plane AA' of fig. 4b, show an example of the fairwater 300once the cavities 342 and 343 of the body 312 have been filled with a load, for example sea water, while the cavities 340 and 341 of the body 310 have been left empty. The load or filling is represented with crosses in figs. 4b and 4c.
As shown in fig. 4b and fig. 4c, as a result of the selective filling with a load of the cavities 342 and 343 of the body 312, the body 312 tends to adopt the opposite orientation from that of the body 310 when submerged in sea water, such that the two bodies 310 and 312 adopt different and matching mounting orientations, and may be easily handled underwater and assembled on the marine vessel.
In examples, if open cavities such as 342, 343 of body 312 are to be filled with sea water, they may be configured such that the sea water may enter through the openings 349 and fill the cavities once the body is placed in the water in the vicinity of the marine vessel. Thus, at the time of releasing the fairwater bodies in the sea to be assembled on a marine vessel, and depending on the orientation desired for each body, the cavities of each body may be selectively left open so they fill with water once the bodies are submerged, or closed with a closure element before they are released in the sea, so they remain empty.
Fig. 5 shows in cross-section a first body 410 and a second body 412 of a fairwater 400 according to another example of the present disclosure. Bodies 410 and 412 may have a general external shape similar to that of the bodies shown in figs. 3 and 4.
In the example of Fig. 5 the two bodies 410 and 412 of fairwater 400 are first manufactured with the same general external shape and the same mass distribution: each of the bodies 410 and 412 comprises a web region of lower density, respectively 420 and 430, and a leg region of higher density, respectively 422 and 432, such that both bodies 410 and 412 would tend to become oriented as shown for body 410 on the left of fig. 5, when submerged in sea water. However, each body 410, 412 may also comprise a seat or recess 440, e.g. a channel-shaped recess formed along at least part of the web region 420 and 430.
As shown on the right of fig. 5, before the fairwater 400 is placed in water to be assembled at a target on a marine vessel, a weight 460 may be arranged in the recess 440 of body 412 and held in place therein, e.g. with a suitable closure element 450. The presence of the weight 460 in the recess 440 of body 412 causes a change in the mass distribution of this body, which is different from the mass distribution of body 410. For example, as shown on the right of fig. 5, the web region 430 of body 412 may now have a higher density than its leg region 432, such that the body 412, when submerged, tends to adopt the illustrated orientation, that is different from the orientation of body 410, to which no weight is attached.
It will be understood that, in other examples, the weight 460 may be attached to a suitable surface of the body without the presence of a dedicated seat or recess, by using fasteners such as screws, or with suitable attachment fixtures provided on the body.
In other examples, foreseen in the present disclosure but not illustrated in detail, one body of a fairwater may comprise no cavities, or may comprise a cavity with a different shape, volume, and / or position from those of another body of the fairwater; each body may also comprise multiple cavities, to be selectively loaded before use, depending on the stable equilibrium orientation desired for each body, and the mass distribution required to provide this orientation.
Similarly, one or several bodies of a fairwater may be configured with suitable mass distributions by combining several described solutions, i.e. different materials or different material densities, and/or enclosed cavities, and/or open cavities with or without a load, and/or weights.
In the examples illustrated and described herein, the fairwater is configured with bodies that adopt predetermined mounting orientations bringing them face to face to be assembled vertically, e.g. an "upper body" 312 and a "lower body" 310. Alternatively, the bodies of fairwaters according to the present disclosure may be configured to adopt other predetermined orientations to be assembled: for example a "right-side body" and a "left-side body", to be assembled facing each other horizontally. In this case, for example, each body 310, 312 could have a first region, formed by a half body including one of the legs of the U-shaped cross section, and a second region formed by a half body including the other leg of the U-shaped cross section: the mass distribution of each body would then be configured to adopt suitable orientations, e.g. by loading the open cavity 340 of body 310 and the open cavity 342 of body 312, while leaving cavities 341 and 343 empty. Other orientations for assembly, and the corresponding differences in mass distributions of the bodies to achieve these orientations, are also possible. Furthermore, each body may be configured with suitable mass distributions with respect to two horizontal Cartesian coordinate axes, to cause the bodies to adopt, when in sea water, predetermined orientations in two directions in space.
In all of the above examples of fig. 3, fig. 4 and fig. 5, each body is additionally configured with a floatability that is close to neutral, as discussed above, e.g. in relation with fig. 1. Thus, when placed into the sea, they are easily displaced both horizontally and vertically, e.g. by divers.
Underwater elements according to the present disclosure, such as the examples of figures 3 to 5, may comprise two or more bodies, wherein the two or more bodies with the same volume and the same outer shape or symmetrical shapes, and different mass distributions, such that the bodies in water tend to adopt orientations different from one another. In such cases, the two or more bodies may have the same mass or weight and the same volume, and therefore the same floatability, and differ only in the distribution of the mass across the body. Alternatively, the bodies may have different floatabilities.
Furthermore, the bodies of example fairwaters as disclosed herein may comprise matching guiding or self-alignment features (such as a conical pin and an opening, or others) to facilitate assembly of the bodies to each other.
Underwater elements according to the present disclosure, and particularly according to any of the examples described herein, may have bodies made of materials selected from polymers, composition of cements, metals, metals alloys, or combinations thereof.
The bodies may be manufactured by any technology suitable to the size, shape, materials, etc. of the body; in some examples, they may be manufactured at least partly by 3D printing, e.g. with commercially available large format 3D printers. For example, 3D-printing may be convenient for manufacture bodies of complex shapes, bodies comprising a gradient in the material density, bodies with cavities and/or metal inserts, etc.
Fig. 6 schematically illustrates a method for mounting in a predetermined mounting position, or target position, and in a predetermined mounting orientation, a fairwater 100 on a marine vessel 110 that is afloat. In fig. 6, for illustration and for ease of understanding, a rudder of the marine vessel 110 is not shown.
The fairwater 100 is an underwater element according to the present disclosure, comprising two bodies 12a and 12b, each configured with a weight and a volume resulting in a floatability in sea water that is close to neutral (in this example, neutral or slightly positive); and with a mass distribution resulting in that, in the condition of stable equilibrium of the body in sea water, with the centers of buoyancy and gravity vertically aligned, the body is in the desired or predetermined mounting orientation. The fairwater 100 may be similar to any of the fairwaters 200, 200', 300 or 400 described above, or may have different features.
In a first step S1, the fairwater 100 comprising the two bodies 12a - 12b is released into water 20 in the vicinity of marine vessel 110, that is afloat. When released into water, for example in the sea, each body 12a - 12b floats at the water surface. Furthermore, each of the bodies 12a - 12b tilts or turns until its center of buoyancy 42a - 42b and center of gravity 52a - 52b align vertically, whereby each of the bodies 12a - 12b adopts the predetermined mounting orientation for which it was designed.
For example, in fig. 6, the predetermined mounting orientation is the concave side of each body 12a - 12b facing against an upper side of a propeller shaft and a lower side of the propeller shaft, respectively: i.e., the bodies adopt opposite orientations around a horizontal axis lying in the plane of the drawing.
In a second step S2, divers 120 may fully submerge the two bodies 12a - 12b. During this movement, the bodies may tilt due to the force exerted on them by the divers; however, once the external force ceases, e.g. when the diver has brought the body near to the target and releases it, each body recovers its predetermined mounting orientation.
In a third step S3, the diver 120 displaces the bodies 12a - 12b to the target position. In fig. 6, the target position is in the vicinity of a bearing arranged on the propeller shaft. Divers 120 do not need to exert a large force on the bodies to submerge them to the target position, by virtue of their floatability close to neutral.
When the bodies 12a - 12b are in their respective target position (i.e., in fig. 6, the target position is in the vicinity of a bearing arranged on the propeller shaft), the fairwater 100 is mounted on the marine vessel 110 at the target position.
In fig. 6, the bodies 12a - 12b of the fairwater 100 are shown in three different positions: at the sea surface after being released, e.g. from a ship; near the target position after being submerged by divers; and after being mounted around the target and assembled together.
As a result, dry-docking the marine vessel 110 for changing or mounting the fairwater 100 of the marine vessel 110 is no longer required. As a result, repairs or maintenance such as changing an underwater element, may be carried out while the marine vessel remains operative. Furthermore, substitution of the fairwater 100 may be carried out by divers 120.
Fig. 7 schematically represents a block diagram of a method 700 for mounting in a predetermined mounting position and in a predetermined mounting orientation an underwater element on a marine vessel afloat in the sea. The method of fig. 7 may be performed in combination with underwater elements according to any of the above examples, or others within the scope of the present disclosure.
In the example of fig. 7, the method 700 for mounting an underwater element on a marine vessel afloat comprises, at block 710, providing the underwater element comprising a body, wherein the body has a weight and a volume such that the buoyant force is between 80% and 120% of the gravitational force, and a mass distribution such that, in the desired or predetermined mounting orientation, the center of buoyancy and the center of gravity of the body are vertically aligned.
At block 720, the underwater element is released in water and submerged in a vicinity of the marine vessel. In the water, the underwater element tilts and/or turns and adopts the predetermined mounting orientation.
At block 730, the underwater element is displaced to a predetermined mounting position, or target position, of the marine vessel, for example by divers.
At block 740, the underwater element, still in the predetermined mounting orientation, is mounted on the marine vessel at the target position.
In some examples, block 710 may comprise providing two or more bodies for forming the underwater element, wherein at least one of the bodies comprises a cavity. In some of these examples, the method 700 may further comprise loading with a load the cavity of the two or more bodies or filling with water the cavity of the two or more bodies (e.g., of only one body or of each body). In some of these examples, the first body may comprise the cavity while the second body does not comprise the cavity or comprises a different cavity.
In some examples, block 740 may comprise arranging the first body of the two or more bodies at a first target position, and arranging the second body of the two or more bodies at a second target position.
In some examples, the method 700 may further comprise assembling the first body of the two or more bodies with the second body of the two or more bodies.
Fig. 8 is similar to fig. 7, but relates to a fairwater: fig. 8 schematically represents a block diagram of a method 800, according to an example of the present disclosure, for mounting in a predetermined mounting position and orientation a fairwater on a marine vessel that is afloat. The method of fig. 8 may be performed in combination with fairwaters according to any of the above examples, or others within the scope of the present disclosure.
In the example of fig. 8, the method 800 comprises, at block 810, providing the fairwater comprising a body with a weight, volume and mass distribution according to the present disclosure.
At block 820, the fairwater is submerged in a vicinity of the marine vessel.
At block 830, the fairwater is displaced to a predetermined mounting or target position of the marine vessel.
At block 840, the fairwater is mounting on the marine vessel at the target position, the target position being about a propeller shaft of the marine vessel.
In some examples, block 810 may comprise providing two or more bodies for forming the fairwater.
In some examples, block 840 may comprise arranging a first body of the two or more bodies at a first target position in the vicinity of a bearing arranged on the propeller shaft, and arranging a second body of the two or more bodies at a second target position in the vicinity of the bearing arranged on the propeller shaft.
In some of these examples, the method 800 may further comprise facing the first body of the two or more bodies against the second body of the two or more bodies, and displacing the first body of the two or more bodies towards the second body of the two or more bodies such that the first body of the two or more bodies is fixedly coupled to the second body of the two or more bodies.
In some of these examples, the method 800 may further comprise assembling the first body of the two or more bodies with the second body of the two or more bodies.
Although only a number of examples have been disclosed herein, other alternatives, modifications, uses and/or equivalents thereof are possible. Furthermore, all combinations of the described examples are also covered. Thus, the scope of the present disclosure should not be limited by particular examples, but should be determined only by a fair reading of the claims that follow. If reference signs related to drawings are placed in parentheses in a claim, they are solely for attempting to increase the intelligibility of the claim, and shall not be construed as limiting the scope of the claim.

Claims

Underwater element of a marine vessel, to be mounted on a marine vessel in a predetermined mounting orientation, the underwater element comprising a body, wherein the body has:
▪ a weight and a volume such that when the underwater element is in sea water, a buoyant force acting on the underwater element is between 80% and 120% of a gravitational force acting on the underwater element;
and

▪ a mass distribution such that, in the predetermined mounting orientation of the body, the center of buoyancy and the center of gravity of the body are vertically aligned.
Underwater element according to claim 1, wherein the weight and volume of the body are such that the buoyant force is between 100% and 110% of the gravitational force.
Underwater element according to claim 1 or claim 2, wherein the body comprises an internal cavity.
Underwater element according to claim 3, wherein the cavity is an open cavity in fluid communication with the outside of the body.
Underwater element according to claim 4 or, wherein the body comprises a closing element for closing the cavity.
Underwater element according to any of claims 1 to 5,
wherein the body of the underwater element comprises two or more regions, and

wherein a density of the body in the first region is higher than a density in the second region.
Underwater element according to any of claims 1 to 6,
wherein the underwater element comprises two or more bodies,

the two or more bodies having the same volume and the same external shape or symmetrical external shapes, and

wherein the two or more bodies have different mass distributions, such that in the bodies tend to adopt, when in water, orientations different from one another.
Underwater element according to claim 7, wherein the two or more bodies further have the same internal shape, or symmetrical internal shapes, and wherein the mass distribution of each body of the two or more bodies is adjusted by at least one of selectively attaching weights to the bodies or by selectively filling cavities of the body.
Underwater element according to any of claims 1 to 8,
wherein the underwater element comprises two or more bodies, and

wherein the two or more bodies are configured with matching guiding or self-alignment features to facilitate the assembly of the bodies to each other.
Underwater element according to any of claims 1 to 9, wherein the underwater element is a fairwater.
Method for mounting an underwater element, comprising a body, on a marine vessel that is afloat, in a predetermined mounting position and in a predetermined mounting orientation of the body, the method comprising:
providing the underwater element comprising a body, wherein the body has such a mass distribution that, in the predetermined mounting orientation of the body, the center of buoyancy and the center of gravity of the body are vertically aligned,

submerging the underwater element in a vicinity of the marine vessel;

displacing the underwater element to a target position of the marine vessel; and

mounting the underwater element on the marine vessel at the target position.
Method according to claim 11,
wherein the underwater element is according to any of claims 1 to 10.
Method according to claim 11 or claim 12,
wherein providing the underwater element comprises providing two or more bodies for forming the underwater element, wherein at least one of the bodies comprises a cavity; and

wherein mounting the underwater element on the marine vessel at the target position comprises arranging the first body of the two or more bodies at a first target position and arranging the second body of the two or more bodies at a second target position.
Method according to claim 13, the method further comprising:
assembling the first body of the two or more bodies with the second body of the two or more bodies.
Method according to any of claims 11 to 14,
wherein the underwater element is a fairwater, and

wherein mounting the underwater element on the marine vessel at the target position comprises arranging the fairwater around a propeller shaft of the marine vessel.