Patent Description:
The described embodiments relate generally to towed marine arrays. More particularly, the present embodiments relate to system and techniques for controlling hydrodynamic foil orientation in the marine array.

In towed marine seismic exploration, a hydrophone array is typically towed behind a marine vessel near the sea surface. The hydrophones are mounted to multiple sensor cables, commonly referred to as streamers. The streamers serve as platforms or carriers for the hydrophones, which are distributed along the length of each streamer in the array.

A set of seismic sources, also towed near the sea surface, are operated to periodically emit acoustic energy. The acoustic energy of interest propagates downward through the seawater (or other water column), penetrates the ocean floor, reflects from the subsea strata and other underlying structures, and returns upward through the water column to the hydrophone array.

The reflected seismic energy (or acoustic wave energy) arrives at receiver points in the towed hydrophone array. The array includes many such receiver points, distributed along each of the streamer cables, with sensors configured to generate data records characterizing the upward-traveling acoustic wavelets (or seismic waves) received from the subsurface structures beneath the seabed, at each of the receiver points. The hydrophone data recordings are later processed to generate seismic images of the underlying structure.

In the field of subsea seismic exploration, there has recently been a demand for seismic equipment operators to conduct their surveys with the seismic equipment submerged below the depths at which most seismic surveys have been conducted in the past. These new, deeper operating targets can now lie well below the depth of the surface-referenced equipment (i.e., the vessel and the paravanes) that is used to tow and laterally spread the seismic sensors.

Typical marine depressors for maintaining equipment at a substantially constant submerged depth tend to be fairly small with very poor aspect ratios, thus resulting in low lift. Aspect ratio is defined as the span of the depressor divided by its chord line length. Wings with high aspect ratios generate high downward lift forces for minimal drag (such that lift-to-drag ratios as high as <NUM>:<NUM> or more are possible), whereas wings with aspect ratios as low as <NUM> or <NUM> (i.e., where span and chord are roughly the same scale) will typically have lift-to-drag ratios as low as <NUM>:<NUM>, or even lower. Conventional depressors can often also provide payload bays which can be used to hold additional ballast to supplement the downforce generated by the depressor.

The problem with using deadweight to generate downforce is that it does not scale with tow speed-it provides a constant downforce regardless of how fast the depressor is moving through the water. This is often disadvantageous for those applications where a range of operational speeds is expected, with the requirement that the towed equipment maintain a stable depth over that speed range. Consequently, there is no easy, economical, or ideal way to submerge and operate seismic equipment, such as towed streamer cables, at the desired lower depths. <CIT> relates to a hydrodynamic foil system for a sensor streamer array including at least two tow ropes each coupled at one end to a survey vessel and at the other end to a paravane. <CIT> relates to a commercial fishing trawl having a net and a mouth opening defined by a head line, a foot line, and side lines. The mouth opening is spread by a plurality of foil segments threaded on one or more of the head line, foot line, or side lines. <CIT> relates to a segmented-foil divertor having a plurality of longitudinally stackable foil segments with an internal conduit extending along the span of each segment to receive a cable passing therethrough. <CIT> relates to a hydrofoil apparatus comprising a first hydrofoil member having positive hydrodynamic pitching moments, a second hydrofoil member having positive hydrodynamic pitching moments, connection means for connecting the first and second hydrofoil members together such that they are able to articulate about the connection means, and first and second bridle members which are for enabling the hydrofoil apparatus to be towed. Documents <CIT> and <CIT> constitute other relevant prior art.

According to the present invention, there is provided a marine array as defined in claim <NUM>.

Embodiments described in the present disclosure are directed to controlling an angle of attack for submerged foils of a marine array. Foil sections may be coupled to one another by a pair of cables that converge toward one another at connection points adjacent to opposing ends of the foils. An actuator may be coupled to the cables and configured to adjust tension in the cables, thereby altering an angle of attack of the foils.

In an embodiment, a marine array is disclosed. The marine array includes a cable configured to be towed by a vessel and carry a payload through a marine environment. The marine array further includes a modular foil system coupled with the cable and configured to bias the payload toward a target position. The modular foil system includes a group of foil sections collectively defining an angle of attack. The modular foil system further includes a pair of through cables supporting the group of foil sections within the modular foil system and converging toward a connection point.

In another embodiment, the marine array may further include an actuator configured to alter a tension in one or both of the pair of through cables, thereby altering the angle of attack. In some cases, the group of foil sections is a first group of foil sections defining a first angle of attack. The pair of through cables is a first pair of through cables. In this regard, the modular foil system may further include a second group of foil sections collectively defining a second angle of attack. The modular foil system may further include a second pair of through cables supporting the second group of foil sections within the modular foil system and converging toward the connection point.

In another embodiment, the second angle of attack is distinct from the first angle of attack. The marine array may further include an actuator configured to alter a tension in one or both of the first pair of through cables, thereby altering the first angle of attack relative to the second angle of attack.

In another embodiment, the payload is an instrument configured to at least one of either collect data or transmit data. The target position may include at least one of a lateral position or a depth position.

In another embodiment, the cable may be a first cable towed by the vessel. The marine array may further include a second cable towed by the vessel. The modular foil system may be arranged substantially between submerged portions of the first cable and the second cable.

In another embodiment, the cable is a separator cable. The marine array may further include streamer cables configured to be towed behind the separator cables. The payload may include seismic receivers carried by the streamer cables. The angle of attack may be configured to maintain the seismic receivers at a desired depth.

In another embodiment, the cable is a lateral cable of the marine array under tension. The lateral cable includes an end portion positioned along an edge of the marine array. As such, the modular foil system may be coupled with the lateral cable adjacent the end portion.

In another embodiment, the marine array may further include a spur line connected to the end portion of the lateral cable. The modular foil system may be connected to the spur line opposite the lateral cable.

In another embodiment, the cable is an upper cable. The marine array may further include a lower cable. In some cases, the upper cable and the lower cable cooperate to form a mouth of a fishing trawl. The modular foil system may be configured to increase a separation between the upper cable and the lower cable at the mouth of the fishing trawl. Additionally or alternatively, the modular foil system may be configured to laterally spread the upper cable and the lower cable.

In another embodiment, a modular foil system for biasing a cable of a marine array is disclosed. The modular foil system includes a group of foil sections defining a foil shape having a leading edge and a trailing edge. The modular foil system further includes a first through cable extending through the group of foil sections along the leading edge. The modular foil system further includes a second through cable extending through the group of foil sections along the trailing edge. The modular foil system further includes an actuator configured to adjust a tension in one or both of the first through cable or the second through cable. The first through cable and the second through cable converge at connection points adjacent opposing ends of the group of foil sections.

In another embodiment, the actuator may be a dynamic actuator configured to alter the tension in one or both of the first pair of through cables while submerged in a marine environment. Each of the connection points may be configured to couple a pair of through cables from another modular foil system of the marine array to the first through cable and the second through cable. In some cases, at least one of the connection points is defined by a ring and at least one of the pair of through cables extends through the ring.

In another embodiment, the group of foil sections defines a first duct along the leading edge of the foil shape and a second duct along the trailing edge of the foil shape. The first through cable extends through the first duct. The second through cable extends through the second duct. The group of foil sections may be configured to move within the foil system along the first through cable and the second through cable.

In another embodiment, the actuator is coupled to the first through cable. The actuator is a first actuator. The foil system further comprises a second actuator coupled to the second through cable. The first through cable and the second through cable are integral portions of a continuous cable.

In another embodiment, a method of positioning a modular foil system in a marine array is disclosed. The method includes launching an array into a marine environment, the array comprising a cable configured to carry a payload and a modular foil system coupled to the cable. The method includes acquiring submerged positional data associated with the modular foil system. The method includes determining an adjustment parameter for the modular foil system by comparing the submerged positional data with an operational target. The method includes adjusting an angle of attack of a first group of foil sections of the modular foil system using the adjustment parameter.

In another embodiment, the group of foil sections is supported within the modular foil system by a pair of through cables that converge toward a connection point. The method may further include controlling a tension in one or both of the first pair of through cables using a dynamic actuator. The dynamic actuator may be responsive to the adjustment parameter.

In another embodiment, a marine array is disclosed. The marine array includes a cable configured to be towed by a vessel and a submerged payload through a marine environment. The marine array includes a modular foil system coupled with the cable and configured to bias the submerged payload toward a target position. The modular foil system includes a first group of foil sections having a first angle of attack. The modular foil system further includes a second group of foil sections having a second angle of attack. The first angle of attack is adjustable relative to the second angle of attack.

In another embodiment, the modular foil system further comprises a first pair of through cables. The first group of foil sections is supported in the modular foil system by the first pair of through cables. The first pair of through cables converge toward a connection point, and the connection point couples the first group of foil sections to a discrete assembly of the marine array.

In another embodiment, the marine array includes an actuator configured to alter a tension in one or both of the first pair of through cables, thereby altering the first angle of attack. The actuator may be a dynamic actuator configured to alter the tension in one or both of the first pair of through cables while submerged in the marine environment. In some cases, the actuator is a turnbuckle coupled to one of the first pair of through cables.

In another embodiment, the modular foil system further comprises a second pair of through cables. The second group of foil sections is supported in the modular foil system by the second pair of through cables. The second pair of through cables converge toward the connection point. The second group of foil sections is the discrete assembly coupled to the first group of foil sections at the connection point.

In another embodiment, the cable is a separator cable. The marine seismic array further includes streamer cables configured to be towed behind the separator cables. The payload includes seismic instruments carried by the streamer cables. Both of the first angle of attack and the second angle of attack are configured to maintain the seismic receivers at a desired depth.

In another embodiment, the marine array includes a pair of diverters positioned at opposing ends of the separator cable and configured to laterally spread the separator cable when towed in the marine environment. The pair of diverters may be configured to provide a positive lift to the separator cables along a substantially vertical direction. The modular foil system may be configured to provide a negative lift to the separator cable along the substantially vertical direction, the negative lift operating to counteract the positive lift provided by the pair of diverters.

In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following description.

The use of cross-hatching or shading in the accompanying figures is generally provided to clarify the boundaries between adjacent elements and also to facilitate legibility of the figures. Accordingly, neither the presence nor the absence of cross-hatching or shading conveys or indicates any preference or requirement for particular materials, material properties, element proportions, element dimensions, commonalities of similarly illustrated elements, or any other characteristic, attribute, or property for any element illustrated in the accompanying figures.

Additionally, it should be understood that the proportions and dimensions (either relative or absolute) of the various features and elements (and collections and groupings thereof) and the boundaries, separations, and positional relationships presented therebetween are provided in the accompanying figures merely to facilitate an understanding of the various embodiments described herein and, accordingly, may not necessarily be presented or illustrated to scale, and are not intended to indicate any preference or requirement for an illustrated embodiment to the exclusion of embodiments described with reference thereto.

The description that follows includes sample systems, methods, and apparatuses that embody various elements of the present disclosure. However, it should be understood that the described disclosure may be practiced in a variety of forms in addition to those described herein.

The following disclosure describes systems, devices, and techniques related to controlling an orientation of foil systems of a marine array. The foil systems may be used to control movements and/or maintain a position of various instruments, devices, assemblies and so forth of the marine array. For example, a foil system may include a group of foil sections that cooperate to define a foil shape having a leading edge and a trailing edge. The group of foil sections may be coupled to instruments of the array. When towed, the group of foil sections may generate lift (e.g., including a lateral lift, a perpendicular lift and so on), due in part to an orientation or "angle of attack" of the foil shape. In turn, this lift may be used to correspondingly move instruments coupled to the foil system. The foil sections defining the foil shape may be coupled together by a through cable and/or other mechanism allowing the foil sections to move relative to one another in a dynamic marine environment. However, such movement may limit the orientation of the foil shape and/or other otherwise distort the shape due to hydrodynamic forces.

The foil system of the present disclosure may mitigate such hindrances, thereby allowing the group of foil sections to be arranged at a variety of orientations (e.g., a variety of attack angles). The foil system may be configured to generate different lifts for each orientation or angle of attack. For example, at a first angle of attack the foil system may generate a first lift, whereas at a second angle of attack the foil system may generate a second lift, distinct from the first lift. The foil system may be coupled with instruments of the marine array, as described herein, and thus each of the first lift, the second lift, or other lift may cause the coupled instruments to be steered or positioned in a desired manner. The orientation or angle of attack may be adjusted while the foil system is towed. Accordingly, the foil system may be adaptable to dynamic conditions of a marine environment and/or to particular instruments and requirements of the marine array.

To facilitate the foregoing, the foil system of the present disclosure may be configured to adjust a tension in one or more cables that support the foil sections within the marine array. For the sake of non-limiting illustration, the foil system may include a group of foil sections that are arranged adjacent one another to define the foil shape. A pair of through cables may extend through one or more of, or each of, the group of foil sections, thereby coupling the foil sections to one another and allowing for relative movement between adjacent foil sections.

When deployed, the pair of through cables may have a tension that generally allows the foil sections to orientate at an equilibrium position. The tension in one or both of the through cables may be adjusted in order to modify the orientation or angle of attack, and therefore modify a lift generated by the foil system. For example, one or more actuators may be coupled with the pair of through cables. The actuator may be configured to increase a tension in one or both of the pair of through cables. As the tension is increased, movement of foil sections relative to one another may be diminished, and the group of adjacent foil sections may collectively orientate toward, for example, an enhanced attack. The enhanced angle of attack may generate greater lift, and thus the foil system may exert a greater force on coupled instruments of the array, which may help steer or depress the instruments toward a desired position.

In turn, the foil system may also operate to diminish the angle of attack by reducing tension in the pair of through cables. For example, the actuator may operate to reduce the tension in one or both of the pair of through cables. The reduced tension may allow the foil sections to return toward the equilibrium position, thereby resulting in a diminished angle of attack. The diminished angle of attack may generate less lift, and thus the foil system, may exert a lesser force on the coupled instruments of the array. This may help steer or depress the instruments toward a desired position.

The actuator, as described herein, may be substantially any appropriate component that is used to adjust a tension in a cable. In one embodiment, the actuator may be a mechanical component, such as a turnbuckle. The turnbuckle may be manually adjusted, for example, prior to deployment of array, in order to set a desired angle of attack of the foils. Additionally or alternatively, the foil system may include various dynamic actuator, such as a pneumatic, hydraulic, or electromechanical controller that is used to modify a tension in the pair of through cables. It will be appreciated, however, that other actuators are possible and contemplated with the scope of the present disclosure.

In some cases, the actuator may be configured to adjust a tension of the cable while the array is deployed in a marine environment. For example, the actuator may be configured to receive a signal from another source, such as a vessel towing the array, or another remote source. The actuator may use the signal to adjust a tension in the cable. For example, in a first configuration, the signal may be indicative of a first desired orientation and the actuator may adjust a tension in the through cable in order for the foil section to match the first desired orientation. Likewise, in another configuration, the signal may be indicative of a second desired orientation and the actuator may adjust a tension in the through cable in order for the foil section to match the second desired orientation.

The actuator may therefore be used for dynamic or real-time, "on-the-fly" positioning of instrument of the marine array. Continuing the non-limiting illustration, the first desired orientation of the group of foil sections may correspond to a target lift generated by the foil section in order to position instruments of the array in a desired location (or submerged depth). Conditions may change in the marine environment, for example, due to unpredictable hydrodynamic forces, marine debris or obstacles, and so forth, including changes in course for the vessel itself. It may thus be desirable to reposition instruments of the array. Stated differently, it may be desirable to exert different forces on the instrument in order to account for the changing conditions.

The second desired orientation of the above illustration may correspond to such different force, and thus the actuator may help account for the changing condition. In some cases, the array may employ various sensors to detect the changing conditions. The actuator may be coupled with these sensors, and thus automatically compensate for the changing condition by altering the tension in the coupled through cables.

The foil systems of the present disclosure may serve a variety of functions in a marine array, as describe herein. For example, in one configuration, the foil sections may define a foil shape that extends substantially laterally through a marine environment. When orientated at a negative angle of attack, the foil sections may generate negative lift that biases the foil sections deeper into a marine environment. The foil section in such configuration may therefore function as a depressor that operates to maintain coupled instruments at a desired depth. As another example, in a second configuration, the foil sections may define a foil shape that extends substantially perpendicularly through the marine environment. When orientated at an angle of attack, the foil section may generate a lift that biases the foil sections laterally in the marine environment. The foil section in such configuration may therefore function as a steering or positioning device that operates to cause coupled instruments to move toward a desired position. In other configurations, other lifts may be possible, including a configurations in which the foil sections generate combination of perpendicular and lateral lifts.

In order to facilitate coupling of the foil systems described herein to various instruments of that array, the through cables converge toward a connection point For example, the group of foil sections may be arranged adjacent to one another to define a foil shape having a first end (e.g., a first longitudinal end) and a second end (e.g., a second longitudinal end). The through cables extend through ducts defined in the foil sections and may converge toward one another at each of the first end and the second end. In particular, the pair of through cables converge toward one another at a first connection adjacent the first end of the foil shape. Likewise, the pair of through cables may converge toward one another at second connection adjacent the second end of the foil shape. The convergence of the cables may help regulate tension in the through cables, and therefore allow for more accurate or precise control of foil shape angle of attack.

The pair of through cables may converge toward a connection point adjacent an end of a foil section groups, and as such, define a triangular shape with an endmost one of the foil sections. As described herein, the triangular shape may change according to a magnitude of the tension in one or both of the through cables of the foil system. For example, the actuator may be associated with a through cable adjacent a leading edge of the foil sections, and when in a neutral or unactuated state, the through cables may form a triangle shape with the endmost foil section that substantially resembles a right triangle (e.g., with a substantially ninety degree angle formed between the leading edge through cable and the endmost foil section). As the actuator operates to decrease the tension in the leading edge cable, thereby increasing tension in the trailing edge cable (e.g., to adjust the angle of attack), the triangular shape will change, such as changing into a shape substantially resembling an isosceles triangle. Yet further, the actuator may operate to increase or decrease the tension, and further manipulate the angle defined by the leading edge through cable and the endmost foil section. This dynamic triangular shape may help facilitate fine control of the angle of attack, while also allowing the foil section angle of attack to be modified relative to other modules of a modular foil array.

For example, the convergence of the through cable may allow the foil system to be an assembly of a modular foil system. For example, as described herein, a first group of foil sections may define a first foil shape and a second, distinct group of foil sections may define a second foil shape. The first group of foil sections may be coupled to the second group of foil sections by one or more pairs of through cables that converge at a connection point positioned substantially between the distinct groups of foils. In this manner, distinct groups of foil sections may be "daisy-chained" to one another across a span of the marine array. This may also allow for more accurate or precise control of a tension in the through cables as the tension may be adjusted in each individual "module" (e.g., adjacent each distinct group of foil sections).

Adjusting the tension in through cables adjacent individual groups of foil sections may allow for distinct angles of attack of foil sections along the modular system. For example, a first group of foil sections may have a first angle of attack based on a first tension in the through cable supporting the first foil sections in the array. Further, a second group of foil sections may have a second angle of attack based on a second, distinct tension in the through cable supporting the second foil section in the array. As such, a first portion of the modular foil system (e.g., the first group of foil sections) may generate a first lift, whereas a second portion of the modular foil system (e.g., the second group of foil section) may generate a second, distinct lift. This may allow, in some embodiments, the modular foil system to extend over a substantial span of the array, and generate specific or targeted lifts at particular areas of the array. And as described herein, the tension may be dynamically adjusted on-the-fly, and thus each portion of the modular foil system may be configured to compensate for dynamic conditions for an associated area within the array.

According to embodiments described herein, the foil systems, modular foil systems, and so on may be implemented with a marine array. A marine array may be towed through a marine environment by a vessel. In some embodiments, the marine array may be a seismic array. Broadly, a seismic array may include various sources and streamers used to study rock strata and other structures below the surface of the ocean or other bodies of water. One or more marine vessels are typically used to tow the source and/or receiver arrays in order to obtain relevant geological data covering a desired surface area of the ocean floor. For example, a single surface vessel may simultaneously tow both a source array and an array of seismic streamers, or different vessels can be used to tow separate source and receiver arrays. Alternatively, a towed source array can be used in conjunction with stationary receivers, for example, an array of ocean-bottom nodes, or with ocean-bottom cables deployed on the seabed.

It will be appreciated that a seismic array is one application of a marine array. In other embodiments, a marine array may be, or refer to, substantially any collection of components that are towed by a vessel through a body of water. For example, a marine array may include a fishing trawl that includes cables, nets, and/or other components configured to capture fish in the marine environment. The modular foil system of the present disclosure may be coupled with cables of the fishing trawl (e.g., upper cable and lower cables to widen the vertical opening of the trawl mouth, and port and starboard cables to widen the lateral opening of the trawl mouth) in order to facilitate its operation. This may include using the lift generated by the modular foil system to increase (or otherwise manipulate) a size of the mouth of the fishing trawl. One or more dynamic actuators may control one or more modular foil system attached to the cables forming the mouth of the fishing trawl and steer the fishing trawl up or down and side to side. The modular foil systems can also be used to change the rate of descent and ascent of the trawl through the marine environment to increase or decrease deployment and retrieval times.

Other marine arrays are contemplated herein. In some cases, the marine array may be a towed payload used in a military application. As another example, the marine array may be a towed instrument or other payload used in oceanographic studies and the like. Accordingly, while the following figures may describe the modular foil systems in the context of a particular embodiment of a marine seismic array, this is for purposes of illustration. As such, any discussion of a modular foil system, foil section, and so on with respect to a particular embodiment of a marine array, may apply to other embodiments of marine arrays, and should not be construed as limiting.

Reference will now be made to the accompanying drawings, which assist in illustrating various features of the present disclosure. The following description is presented for purposes of illustration and description. Furthermore, the description is not intended to limit the inventive aspects to the forms disclosed herein. Consequently, variations and modifications commensurate with the following teachings, and skill and knowledge of the relevant art, are within the scope of the present inventive aspects.

One embodiment of a towed three-dimensional, high-resolution, marine seismic array <NUM> is depicted in <FIG> and <FIG>. The array <NUM> is towed by a marine vessel <NUM>. A number of cables, ropes, or other lines may be attached to the marine vessel <NUM>. For example, an umbilical cable <NUM> with acoustic signal source generators (e.g., air guns) may trail directly behind the marine vessel <NUM>. A pair of tow ropes <NUM> or cables may splay out to port and starboard from the rear of the marine vessel <NUM>. A cross-cable <NUM> may extend between and connect to the tow ropes <NUM> adjacent to the aft ends of the tow ropes <NUM>. A number of streamer cables <NUM> may be connected to the cross-cable <NUM> at a number of locations along the length of the cross-cable <NUM> between the tow ropes <NUM>. In some embodiments, the streamer cables <NUM> may be evenly spaced apart from adjacent streamer cables <NUM> along the length of the cross-cable108. In a typical embodiment, there may be up to <NUM> streamer cables <NUM> and they may be spaced anywhere between <NUM> and <NUM> or more apart. Respective tail buoys <NUM> may be affixed to the ends of each of the streamer cables <NUM> which may help aid in maintaining a position of the streamer cables <NUM>, providing a visual marker for the array, and so on.

The cross-cable <NUM> may extend beyond the port-most and starboard-most streamer cables <NUM> to attach to the tow ropes <NUM>. These lateral sections of the cross-cable <NUM> may be referred to as spur lines <NUM>. In some embodiments, the spur lines <NUM> may be separate ropes or cables that connect to and extend between the lateral ends of the cross-cable <NUM> and the tow ropes <NUM>.

Paravanes <NUM> may further be attached to the tow ropes <NUM> at or adjacent to the connection between the tow ropes <NUM> and the spur lines <NUM> on each of the port and starboard sides. The paravanes <NUM> are winged hydrofoils that move outward in the water in an oblique direction to the direction of travel of the marine vessel <NUM>, thus providing lateral spread to the cross-cable <NUM> and the streamer cables <NUM> attached thereto. In other configurations, alternative spreading devices may be employed to maintain separation of the streamer cables <NUM>, including foil wings as described in U. Patent Application Publication No. <CIT>.

A signal cable <NUM> may extend from the marine vessel <NUM> on one side of the array <NUM> to connect to the cross-cable <NUM> and return signals received by the sensors <NUM> on the streamer cables <NUM>. On an opposite side of the array <NUM>, a recovery rope <NUM> may extend from the marine vessel <NUM> and connect with the cross-cable <NUM> adjacent to the last streamer <NUM>. Surface floats <NUM> may be attached to the cross-cable <NUM> at or adjacent to the lateral ends thereof via a cable with a length corresponding to a desired depth of the streamer cables <NUM>. The surface floats <NUM> act to ensure that the cross-cable <NUM>, and thus the streamer cables <NUM>, do not submerge too deeply when the array <NUM> is towed.

Unfortunately, the port and starboard ends of the cross-cable <NUM>, and thus the streamer cables <NUM> attached thereto, may not achieve a desired depth beneath the surface due to the pull of the paravanes <NUM> on the spur lines <NUM>. The paravanes <NUM> remain at the surface of the water and thus pull the lateral ends of the cross-cable upward as well as laterally outward.

To counteract the effect of the paravanes <NUM> on the cross cable <NUM>, a positioning device or depressor <NUM> designed to provide downward lift may be attached to the cross-cable <NUM>, the spur line <NUM>, or both, as shown in <FIG>. The depressor <NUM> may be composed of a number of foils <NUM> pivotably attached to the cross-cable <NUM> or the spur line <NUM>. The collection of foils <NUM> forming depressor <NUM> are referred to herein as a "modular foil depressor. " As shown in <FIG>, the modular foil depressors <NUM> may fill the entire length of the spur line <NUM>. Alternatively, the modular foil depressor <NUM> may only fill a portion of the spur line <NUM> and may be situated either laterally outward closer to the paravanes <NUM> or more inward closer to the streamer cables <NUM>. As noted above, the modular foil depressor <NUM> may also be positioned on the cross-cable <NUM>, inside the port-most and starboard-most streamer cables <NUM>. The location of the modular foil depressor <NUM> may be selected based upon a number of factors including the amount of downward lift generated by the modular foil depressor <NUM>, the separation distance of the streamer cables <NUM>, the mass of the sensors <NUM>, streamer cables <NUM>, and cross-cable <NUM>, and the lift force generated by the paravanes <NUM> among other factors.

In addition to the depth control discussed, as shown in <FIG>, a modular foil depressor <NUM> deployed on the spur line <NUM> also provides "lift assist" to the paravanes <NUM> attached by a bridle <NUM> to the intersection of the tow lines <NUM> and spur lines <NUM>. That is, since the modular foil depressor <NUM> induces a downward catenary to the spur line <NUM>, as shown in <FIG>, a first component <NUM> of the lift force <NUM> acts downward as discussed above, but a second component <NUM> of the lift force <NUM> also acts horizontally (i.e. outboard). This horizontal "lift assist" of the second component <NUM> provided by the modular foil depressor <NUM> means that the existing standard paravanes <NUM> will now be able to spread the seismic array <NUM> wider than previously possible. Alternatively, the configuration including the modular foil depressor <NUM> on the spur line <NUM> may achieve the same spread but at a shorter offset behind the marine vessel towing the array <NUM>. In another implementation, the same spread and offset may be achieved, but a more efficient setting for the bridle <NUM> attaching the paravanes <NUM> may be used and hence reduce fuel consumption of the marine vessel.

In addition to the use of a series of depressor sections on spur lines to achieve depression forces to submerge streamer heads down to desired depths for seismic arrays, the modular foil depressor may provide a number of other features and advantages.

The modular foil depressor can readily be installed on existing in-water equipment, such as, for example, by threading the individual depressor sections onto existing spur lines between paravanes and outboard streamer cable heads. Modular foil depressors may also be installed on numerous other existing ropes.

The modular foil depressor can be deployed over the side of the marine vessel, or down the gun chute, and will then self-orient and generate lift without operator intervention. Handling, deployment, and recovery operations are essentially hands-free with no special davits or dedicated winches or cranes required. It is also compact and can be easily and efficiently stowed on the vessel when onboard.

In other embodiments, a foil system may be used to generate a lift along a lateral direction. This may allow a foil system to steer or position a component of the marine array. For purposes of illustration, a schematic illustration of a dynamic wing foil system <NUM>, composed of a number of adjacent foil sections <NUM>, is shown in <FIG>. The dynamic wing foil system <NUM> may generally extend perpendicularly into a marine environment and generate lift that is used to steer components of the array.

To facilitate the foregoing, the dynamic wing foil system <NUM> is shown in <FIG> as including a representative the adjustment mechanism <NUM> The adjustment mechanism <NUM> may include various components that may be used to manipulate the wing foil system <NUM>, such as manipulate an orientation of the wing foil system <NUM> to generate a target lift when towed through the marine environment. In an embodiment, the adjustment mechanism may include a turnbuckle <NUM> and a pulley <NUM>, ratchet, winch, or similar cable guide and feed mechanism may be mounted to the floatation apparatus <NUM>, e.g., between a control cable <NUM> and an aft anchor point <NUM> on the back or rear section of the floatation apparatus <NUM> (in the trailing edge direction of the foil sections <NUM>). The forward cable <NUM> and through cable <NUM> extending through the foil sections <NUM> are mounted to a forward anchor <NUM> attached to the front section of the floatation apparatus <NUM> (in the leading edge direction of the foil sections <NUM>).

The adjustment mechanism <NUM> can be configured for adjusting either the forward cable <NUM> or the aft cable <NUM>; both embodiments are encompassed. Another option is to use an adjustment mechanism <NUM> that provides differential adjustments to both forward and aft cabled <NUM>, <NUM>; e.g., by shortening one cable while lengthening the other at the same time. In some designs a single control cable may be used, extending from the forward cable anchor <NUM> down along a forward cable section <NUM>, then passing through a cable return or wrapping or inflecting around a cable connector <NUM> attached to a submerged cable <NUM>, and back up along an aft cable section <NUM> to the forward anchor <NUM> through the pulley <NUM>. Alternatively, separate forward and aft control cables <NUM>, <NUM> may be provided, e.g., individually attached at the submerged cable connector <NUM>. The submerged cable <NUM> can be provided either as a tow line for a streamer cable <NUM> or as an umbilical for a source gun array.

A control device <NUM> for the adjustment mechanism <NUM> may be located at either the top or bottom end of the foil wing system <NUM>, for example, inside the floatation apparatus <NUM>. Suitable control devices <NUM> include processor, memory, and software components configured to direct the adjustment mechanism <NUM> to selectively vary the length and/or tension in the forward and aft cables <NUM>, <NUM>, in order to regulate the lift and steering forces generated by the foil wing system <NUM> by changing the angle of attack along individual foil sections <NUM>. For example, the control device <NUM> may be configured to control an electric motor or similar drive in order to actuate the adjustment mechanism <NUM>, providing for automated steering by adjustment of the relative length and tension in the forward and aft control cables <NUM>, <NUM>. Other control options include, but are not limited to, hydraulic and pneumatically controlled ram or piston mechanisms, electric winch drives, and motor-driven rack and pinion arrangements. For example, in some cases, control systems and configurations such as those described in U. Patent Application Publication No. <CIT> may be employed to facilitate tensioning of the cables described with respect to <FIG>.

In the context of a seismic survey as described above, a number of seismic energy source devices and/or a number of sensor nodes may be attached along the length of cables deployed and towed behind the marine vessel. Each of the cables, or the seismic equipment attached to the cables, may have a steering device associated therewith in order to adjust the position of the cable or seismic devices within the water. In some implementations, it may be very important that the towed marine equipment such as the cables with seismic equipment closely follow a predetermined course (e.g., in order to accurately map a subsurface formation). In addition, if multiple cables are deployed behind a marine vessel it may be important to maintain a constant separation distance between the cables. To meet these needs, steering mechanisms may be attached to each cable and further or alternatively attached to the equipment towed by the cable.

The foil wing systems <NUM> are just one exemplary implementation of a steering mechanism that may be employed to steer and position cables, seismic energy sources, sensor nodes, buoys and floats in the seismic array, etc. Other steering mechanisms for attachment to such sensor array components exist. These may include paravanes, hydrofoils, rudders, wings, elevators, and various other devices. The orientations of each of these devices while being towed through the water may be adjusted for steering. Such adjustments may be made by increasing or decreasing tension on control cables (i.e., making them more taught or more slack), engaging actuators to physically move a steering element; engaging motors to drive rotating elements, etc. In each case, the steering mechanisms are controlled by signals calculated to alter their orientation appropriately to maintain a proper course for the seismic array elements within the water. These signals are determined by sophisticated navigation and control systems that work in concert with the navigation of the marine vessel in order to ensure that the elements of the seismic array stay on course and maintain proper separation distances between adjacent elements.

<FIG> depict embodiments of foil systems of the present disclosure. In particular, <FIG> depict embodiments of foil systems that define a group foil shape configured to have an adjustable angle of attack or orientation. In this regard, the foil system or systems of the present disclosure may generate a variety of distinct lifts based on the adjustable angle of attack of the group foil shape. It will be appreciated that that foil systems and configurations described with respect to <FIG> may be used with any of the marine arrays described herein. In this regard, the foil systems described with respect to <FIG> may be used as, or define a component or assembly of, a modular foil depressor (e.g., depressor <NUM> of <FIG>), a wing foil system (e.g., wing foil system <NUM> of <FIG>), and so forth as may be appropriate for a given application.

With reference to <FIG>, a tensioned cable <NUM> is shown. The tensioned cable <NUM> may be any appropriate cable of a marine array, such as a cable that is in tension and forming a component of a seismic array or fishing trawl assembly, among other applications. The tensioned cable <NUM> is shown towed along a direction of tow <NUM>. At a first end, the tensioned cable may be tensioned in a first tensioning direction 582a. At a second end, opposite the first end, the tensioned cable may be tensioned in a second tensioning direction 582b.

<FIG> further shows a foil system <NUM>, which is further depicted in different variations of deployment in <FIG>. The foil system <NUM> may be coupled with, or substantially replace, the tensioned cable <NUM>. This may allow the foil system to provide lift to the portion of the marine array associated with the tensioned cable <NUM>. The foil system <NUM> may include a number of foil sections <NUM>. Each foil section <NUM> has a span, a chord, and a foil cross-section, which may be a standard hydrofoil cross-section, as shown and described further herein with respect to <FIG>, or may be any other desired foil cross-section, such as NACA, Eppler, Gottingen, or any other custom foil cross-section suitable for the desired application.

The foil sections <NUM> may be arranged or stacked adjacent one another. In this regard, the foil sections <NUM> may be a group of foil sections that collectively define a foil shape. The foil shape may have a leading edge <NUM> and a trailing edge <NUM>. The foil shape of the foil system <NUM> may be arranged at a variety of orientations or angles of attack relative to a direction of a flow, for example, as described in greater detail below with respect to <FIG> and <FIG>. This may cause the foil system <NUM> to generate lift that is used to manipulate components of a marine array (e.g., seismic cables, receivers, and so on) in order to steer, move, position, and/or depress the components, as may be appropriate for a given application.

In the embodiments of <FIG>, the foil sections <NUM> are coupled to one another using a pair of through cables, such as a first through cable 526a and a second through cable 526b. The first through cable 526a and the second through cable 526b extend through the foil sections <NUM>, thereby supporting the foil sections <NUM> within the foil system <NUM>. As one example, the foil sections <NUM> define ducts that extend through the foil sections <NUM>. The ducts may extend along and just aft of each of the leading edge <NUM> and just forward of the trailing edge <NUM> of the foil shape. The first through cable 526a and the second through cable 526b are therefore be positioned within and threaded through the ducts of the foil section <NUM>. In turn, the first through cable 526a and the second through cable 526b may be coupled to another component or assembly of a marine array, and thereby help support the foil sections <NUM> with the array.

In the embodiment of <FIG>, the first through cable 526a and the second through cable 526b may couple the foil sections <NUM> to connection points within a marine array. In a particular embodiment, <FIG> shows a first connection point <NUM> and a second connection point <NUM>. The first connection point <NUM> and/or the second connection point <NUM> may be a hook, a tie, a pulley, a fixed connection, and so on of the marine array; however, other configurations are possible. The connection points <NUM>, <NUM> may generally define a module of a modular foil system (e.g., such as that described in greater detail with respect to <FIG>) and, as such, other groups of foil sections <NUM> may be connected to one another at the connection points <NUM>, <NUM>.

Each of the connection points <NUM>, <NUM> may be coupled with distinct connection cables. This may allow the foil system to be coupled to substantially any other cable, rope, assembly and so on of the marine array, including components of seismic array, a fishing trawl, and so on. For example, <FIG> shows a first connection cable 554a and a second connection cable 554b that are coupled to respective ones of the connection points <NUM>, <NUM>. In turn, the first connection cable 554a and the second connection cable 554b may be coupled to other components of the marine array, according to embodiment described herein.

In the embodiment shown in <FIG>, the through cables may converge at the connection points adjacent opposing ends of the foil sections. For example, the first through cable 526a and the second through cable 526b may converge toward the first connection <NUM>. Also, the first through cable 526a and the second through cable 526b may converge toward the second connection <NUM>. This may allow for more precise or accurate control of an orientation of the foil sections.

For example, the first through cable 526a may extend from the first connection point <NUM> to the second connection point <NUM>. Between the first connection point <NUM> and the second connection point <NUM>, the first through cable 524a extends through a duct of the foil sections <NUM> (e.g., a duct defined along and just aft of the leading edge <NUM>). The second through cable 526b may extend from the second connection point <NUM> to the second connection point <NUM>. Between the first connection point <NUM> and the second connection point <NUM>, the second through cable 526b extends through a duct of the foil sections <NUM> (e.g., a duct defined along and just forward of the trailing edge <NUM>).

Accordingly, a position or orientation of each foil section <NUM> may be defined (or constrained by) the through cables 526a, 526b. For example, each foil section <NUM> may be subjected to dynamic hydrodynamic forces and thus move relative to one another. When the through cables 526a, 526b are substantially slack or otherwise permit movement between each of the foil sections <NUM>, each foil section <NUM> may migrate apart from one another. However, by applying tension in one or both of the cables 526a, 526b, the cables 526a, 526b may form a triangular shape that may act to constrain the movement of foil sections <NUM> relative to one another. The increased tension may also help each foil section <NUM> to stack adjacent to one another, for example, in order to define the foil shape having the leading edge <NUM> and the trailing edge <NUM>. In some cases, one or both of the cables 526a, 526b may be tensioned in order to define a catenary of the foil shape.

In certain embodiments, the tension may be increased in one or both of the through cables 526a, 526b in order to adjust an angle of attack of the foil shape. As one possibility, a tension in one or both of the through cables 526a, 526b may be increased, which, in turn, may increase an angle of attack of the foil shape defined by the foil sections <NUM>. The increased angle of attack may generally cause the foil system <NUM> to generate additional lift. As such, the tension of one or both of the through cables 526a, 526b (or any other cables or ropes supporting the foil sections <NUM> within the array) may be adjusted in order to manipulate lift generated by the foil system <NUM>.

To facilitate the foregoing, <FIG> depict embodiments in which the first and second through cables 524a, 524b converge at the connection points <NUM>, <NUM>, which are adjacent opposing ends of the foil system <NUM>. Converging the through cables 524a, 524b toward common connection points <NUM>, <NUM>, may allow an actuator to control the tension in one or both of the through cables 524a, 524b in a precise, accurate, and potentially dynamic manner.

With particular reference to <FIG>, the tensioned cable <NUM> is arranged substantially parallel to, and connected with, the foil sections <NUM>. In this regard, the foil system may be "piggy-backed" onto an existing high-tensioned cable (e.g., tensioned cable <NUM>) for installation into a marine array, including any of the seismic arrays, fishing trawls, military vessels, and so on, described herein.

For example, the tensioned cable <NUM> may be a cable of a marine array and the foil system <NUM> may be coupled with the tensioned cable <NUM> to provide lift at a target region of the array. As shown in <FIG>, the first connection cable 554a may be coupled with the tensioned cable <NUM> at a first end. Further, the second connection cable 554b may be coupled with the tensioned cable <NUM> at a second end. In this manner, the foil sections <NUM> may generate lift, as described herein, that in turn lifts the tensioned cable <NUM> in a specified manner. Lift may therefore be delivered to a particular region of the marine array by attaching the foil system <NUM> to existing structures and components of the array, rather than modifying components of the array to accommodate the foil system.

With reference to <FIG>, another embodiment of the foil system <NUM> is shown in which the foil system <NUM> includes an actuator <NUM>. The actuator <NUM> may be used to adjust a tension in one or both of the first through cable 526a or the second through cable 526b, which, in turn, may adjust an angle of attack of a foil shape defined by the foil section <NUM>. The actuator <NUM> is shown in <FIG> as coupled to or positioned on the first through cable 524a at a first end <NUM> of the foil system <NUM>. Positioning the actuator <NUM> on the first through cable 526a may help orientate the leading edge <NUM> in one or more directions in order to generate a target lift for the foil system <NUM>. In other cases, actuators may be arranged at various other positions of the foil system <NUM>, including being positioned on the second through cable 524b, for example, as shown with another actuator <NUM>' (shown in phantom).

The actuator <NUM>, may be substantially any appropriate component that is used to adjust a tension in a cable. For example, the actuator may be a mechanical component, such as a turnbuckle. The turnbuckle may be manually adjusted, for example, prior to deployment of the array, in order to set a desired angle of attack of the foils. Additionally or alternatively, the foil system may include various dynamic actuators, such as a pneumatic or electromechanical controller that is used to modify a tension in the pair of through cables, for example, as described in <CIT>. It will be appreciated, however, that other actuators are possible and contemplated with the scope of the present disclosure.

In some cases, the actuator may be configured to adjust a tension of the cable while the array is deployed in a marine environment. For example, the actuator may be configured to receive a signal from another source, such as a vessel towing the array, or another remote source. The actuator may use the signal to adjust a tension in the cable. For example, in a first configuration, the signal may be indicative of a first desired orientation and the actuator may adjust a tension in the through cable in order for the foil section to match the first desired orientation. Likewise, in another configuration, the signal may be indicative of a second desired orientation and the actuator may adjust a tension in the through cable in order for the foil section to match the second desired orientation. In this regard, the actuator <NUM> may, more broadly, be a component of the adjustment mechanism (e.g., adjustment mechanism <NUM> of <FIG>) or other steering or positioning system described herein.

With reference to <FIG>, another embodiment of the foil system <NUM> is shown. In the embodiment of <FIG>, the actuator <NUM> is shown connected to the second connection cable 554b. It will be appreciated that the second connection cable 554b is a continuation of one of the first or second through cables 526a, 526b. By connecting the actuator <NUM> to the second connection cable 554b, the actuator <NUM> may be positioned outside of the triangle formed by the first and second through cables 526a, 526b. By positioning the actuator outside of the triangle formed by the through cables 526a, 526b, an angle of attack of the foil section <NUM> may be manipulated in a controlled manner, in certain embodiments. For example, in the embodiment of <FIG>, the actuator <NUM> functions as an external tensioning member and therefore operates to control an angle of attack of the foil section <NUM> in a manner that is different from that of the internal tension member configuration described herein.

To facilitate the foregoing, <FIG> and <FIG> provide further implementation details of the system shown in <FIG>. For example, <FIG> shows the foil system <NUM> having the external tension member described with respect to <FIG> having three anchor points. By way of illustration, a first anchor point <NUM> is positioned adjacent to a first end <NUM> of the foil system <NUM>. A second anchor point <NUM> and a third anchor point <NUM> are positioned adjacent to a second end <NUM> of the foil system <NUM>. Each of the anchor points may represent a region or point of a marine array that is "fixed" with respect to the foil system <NUM>, for example, such that movement of the cable or other associated component is constrained. At the first end <NUM>, the foil system <NUM> may be connected to the first anchor point <NUM> by cable 554a. And at the second end <NUM>, the foil system <NUM> may be connected to the second anchor point <NUM> by cable 554b and to the third anchor point <NUM> by another connecting cable <NUM>.

The second anchor point <NUM> and the third anchor point <NUM> may help arrange the actuator <NUM> within the foil system <NUM>. For example, the actuator <NUM> may be positioned substantially between the second anchor point <NUM> and the third anchor point <NUM>. This may allow the actuator to be connected with one of the through cables 526a, 526b and define an external tensioning member for the foil system <NUM>.

In the embodiment of <FIG>, the actuator <NUM> is connected with the first through cable 526a. As shown in the detail of <FIG>, the first through cable 526a and the second through cable 526b may each converge toward a connection point defined at the second anchor point <NUM>. At the second anchor point <NUM>, a ring <NUM>' may be positioned for engaging each of the first through cable 526a and the second through cable 526b. In the embodiment of <FIG>, the second through cable 526b may terminate or be tied off at the ring <NUM>'. The first through cable 526a, however, may be engaged with the ring <NUM>', such as extending through the ring <NUM>' and continue beyond the second anchor point <NUM> for connection with the actuator <NUM>. As shown in <FIG>, a connection cable 554b may connect the actuator <NUM> to the third anchor point <NUM>.

<FIG> shows another example implementation of the actuator <NUM> as an external tension member. For example, <FIG> shows the foil system <NUM> having an external tensioning member described with respect to <FIG> and having two anchor points. In this regard, the embodiment of the foil system <NUM> of <FIG> may be substantially analogous as that shown with respect to <FIG>. Notwithstanding, as shown in the detail of <FIG>, the ring <NUM>' may be uncoupled with a fixed connection, such as the second anchor point <NUM> of <FIG>. In this regard, a connection cable <NUM> may be employed in order to connect the ring <NUM>' to the actuator <NUM> and stabilize a position of the ring <NUM>' along the first through cable 526a.

<FIG> and <FIG> depict a perspective view of foil system <NUM>. The foil system <NUM> may be substantially analogous to any of the foil systems described herein, such as the foil system <NUM> of <FIG>. In this regard, the foil system <NUM> may be configured to generate lift in a marine environment and may include: foil sections <NUM>, a leading edge <NUM>, a trailing edge <NUM>, a first through cable <NUM>, a second through cable <NUM>, a connection point <NUM>, and an actuator <NUM>. Redundant explanation of such components is omitted here for clarity.

<FIG> and <FIG> also depict the foil section <NUM> having a first duct <NUM> and a second duct <NUM>. The first through cable <NUM> is positioned within and threaded through the first duct <NUM>, and the second through cable <NUM> is positioned within and threaded through the second duct <NUM>. As shown in <FIG> and <FIG>, the first through cable <NUM> and the second through cable <NUM> may converge toward the connection point <NUM>. This may facilitate adjusting a tension in one or both of first through cable <NUM>, <NUM>, as described herein. Extending from the connection point may be an attachment cable <NUM>. The attachment cable <NUM> may be a component or assembly of a marine array, such as the seismic arrays described herein. In other cases, such as that described with respect to <FIG>, the cable <NUM> may be a connection to, or be used to connect, the foil system <NUM> with other foil systems in order to form a modular foil system.

<FIG> and <FIG> depict the foil system <NUM> in embodiments in which an angle of attack of the foil system <NUM> may be adjusted. For example, as described herein, a tension in one or both of the through cables of <NUM>, <NUM> may be adjusted by the actuator <NUM>. The adjustment in tension may cause the foil section <NUM> to alter an angle of attack relative to a flow F.

<FIG> and <FIG> also depict a change in a triangular shape formed by the through cables <NUM>, <NUM>, and an end of the foil section <NUM> adjacent the connection point <NUM>. As described herein, the triangular shape may change according to a magnitude of tension in one or both of the through cables <NUM>, <NUM>. In the examples shown in <FIG> and <FIG>, the actuator <NUM> is associated with the first through cable <NUM>. In a neutral or unactuated state, the first through cable <NUM> may form a substantially ninety degree angle (e.g., θ) with the end of the foil section <NUM>, and thus the triangular shape may resemble a right triangle. As the actuator <NUM> operates to decrease tension exhibited by the first through cable <NUM>, the triangular shape may change, for example, such as by representing an isosceles triangle. As is evidenced by the changing form of the triangular shape, an angle of attack of the foil system <NUM> may be modified without reliance on, or substantially unhindered by, adjacent foil systems or other components of the seismic array, and so on.

With reference to <FIG>, the foil system <NUM> is shown at a first angle of attack α. For example, the actuator <NUM> may adjust the tension in one or both of the first through cable <NUM> or the second through cable <NUM>. The adjustment may be an increase in tension, for example, from a slack or equilibrium tension, which in turn causes individual foil sections <NUM> to orientate at the angle α from the direction of the flow F.

When arranged at the first angle of attack α, the foil system <NUM> may generate a first lift. For example, the foil sections <NUM> may be a standard NACA or other foil shape, as described herein, and as such, when orientated at the angle of attack α, the foil sections <NUM> may generate the first lift. The first lift may be a lift that is targeted to steer, position, and/or otherwise maintain or manipulate components or assemblies of a marine array. In this regard, the actuator <NUM> may be coupled with either the first through cable <NUM> or the second through cable <NUM>, and adjust the tension in one or both of the first through cable <NUM>, or the second through cable <NUM> such that the foil system <NUM> generates the required lift.

As shown in <FIG>, when the foil system <NUM> is arranged at the first angle of attack α, the first through cable <NUM> may generally form an angle θ with the adjacent end of the foil section <NUM>. While the angle θ is shown in <FIG> as being substantially ninety degrees, it will be appreciated that angles of various magnitudes are possible, for example, based on a tension in the first through cable <NUM>.

Accordingly, the actuator <NUM> may be a dynamic actuator that is configured to adjust the tension in one or both of the first through cable <NUM> and the second through cable <NUM> in response to a signal. The signal may be from another source, such as a vessel, that causes the actuator <NUM> to adjust the tension in one or both of the through cables <NUM>, <NUM> to a certain value. Additionally or alternatively, the actuator <NUM> may be responsive to dynamic conditions and operate to facilitate maintenance of the foil system <NUM> along a desired course or position. For example, various sensors may be integrated with the foil system <NUM>, including within the foil sections <NUM>, and output various data such as position and speed of the foil system in addition to information concerning, for example, a marine environment, such as pressure, temperature, currents, and so forth. Such data from sensors incorporated with the foil system <NUM> may be used by the actuator <NUM> (or other associated system) in order to manipulate the foil system <NUM>. To illustrate, such sensors may detect that the foil system <NUM> is undesirably positioned within a marine array (e.g., due to unanticipated hydrodynamic forces). In turn, a processing element, controller, and so forth (local and/or remote) may determine a new target lift for the foil system <NUM> to generate in order to obtain its desirable position. The actuator <NUM> may receive information regarding the new target lift and adjust the tension in one or both of the through cables accordingly.

In this regard, with reference to <FIG>, the foil system <NUM> is shown at a second angle of attack α'. At the second angle of attack α', the foil system <NUM> may generate a second lift. The second lift may be the new target lift, for example, described above with respect to the operation of the actuator <NUM> in <FIG>. In other cases, the second lift may be desired or predetermined lift for the marine array.

To facilitate the foregoing, the actuator <NUM> may be coupled with either the first through cable <NUM> or the second through cable <NUM>, and adjust the tension in one or both of the first through cable <NUM> or the second through cable <NUM>. The adjustment may be an increase in tension, for example, from a tension of the cables of <FIG>. In turn, this may cause individual foil sections to orientate at a greater angle relative to the flow F than that shown above with respect to <FIG>. Accordingly, the second lift may be greater than the first lift, and thus used to steer, position, and/or otherwise maintain or manipulate components or assemblies of a marine array in a manner distinct from the first lift.

As shown in <FIG>, when the foil system <NUM> is arranged at the second angle of attack α', the first through cable <NUM> may generally form an angle θ' with the adjacent end of the foil section <NUM>. While the angle θ' is shown in <FIG> as being an acute angle, it will be appreciated that angles of various magnitudes are possible, for example, based on a tension in the first through cable <NUM>.

As described above with respect to <FIG>, the actuator <NUM> may be a dynamic actuator or otherwise configured to adjust a tension in one or both of the first through cable <NUM> or second through cable <NUM> when the foil system <NUM> is submerged or deployed in the marine array. Accordingly, while the actuator <NUM> is described above as increasing a tension in the first through cable <NUM> or second through cable <NUM>, it will be appreciated that the actuator <NUM> may decrease a tension in the cables. For example, the actuator <NUM> may decrease a tension in one or both of the first through cable <NUM> or the second through cable <NUM> in order to decrease a magnitude of the angle of the attack. This may be desirable in order to decrease lift generated by the foil system <NUM>. As such, rather than binary configurations, <FIG> and <FIG> show two possible angles of attack along a spectrum of possibilities. The tension in the through cables is varied in order to modify the angle of attack to generate a target lift, and as such, the tension may be varied in any appropriate manner in order to achieve a desired positioning or other manipulation of marine array components using the lift generated by the foil system <NUM>.

The foil systems described herein may be used to define modules of a modular foil system, such as the modular foil system <NUM> described with respect to <FIG>. For example, groups of foil sections may be "daisy-chained" or otherwise linked to one another in order to create a modular foil system. Each group of foil sections may be tunable in order to generate a particular lift that may be different than other groups of foil sections of the modular foil system. This construction may enhance the adaptability and precision of the system. For example, as described herein, each group of foil sections may be supported within the modular foil system by through cables and the tension may be distinctly controlled for each respective group of foil sections. In this manner, not only may each group of foil sections (module) have a distinct tension (and therefore distinct angle of attack), the through cables may be more responsive to actuators configured to adjust the tension, for at least because the tension is adjusted over a shorter, more isolated span of cable. The daisy-chaining or linking of the groups of foil sections may allow the modular foil system to generate lift over a larger span within the marine array, thereby enhancing the possibilities for array designs that implement foil systems over a large span.

To illustrate the foregoing, <FIG> depicts the modular foil system <NUM>. The modular foil system <NUM> may include modules that are daisy-chained or linked to one another in order to form the modular foil system <NUM>. In the example of <FIG>, the modular foil system <NUM> includes a first module 700a, a second module 700b, and a third modular 700c; however in other embodiments, more or fewer modules may be used. Broadly each of the modules 700a, 700b, 700c may include a group of foil sections, such as any of the foil sections described herein, that cooperate to form a foil shape and generate lift. In this regard, each of the modules 700a, 700b, 700c may be configured to have an angle of attack with respect to a direction of flow. The angle of attack for each of the module 700a, 700b, 700c may be adjustable. This may allow each module 700a, 700b, 700c to have a distinct angle of attack, and subsequently generate a distinct lift. This may allow the modular foil system <NUM> to tune the lift generated along specific regions of the system, for example such as increasing the lift generated at a first or second end, without necessarily adjusting the lift in other or adjacent regions of the system. As such, the modular foil system <NUM> may more precisely control lift generation along its entire length or span, and also allow for differential lift generation, which may be appropriate, for example, where distinct components or assemblies of the marine array (having different lift or positioning requirements) are attached along different region of the system <NUM>.

It will be appreciated that each of the modules 700a, 700b, 700c may include components substantially analogous to the component described herein with respect to various other foil systems, such as the foil system <NUM> and the foil system <NUM> of <FIG> and <FIG>, <FIG>, respectively. For purposes of illustration, the module 700a is shown as having foil sections <NUM>, a leading edge <NUM>, a trailing edge <NUM>, a first pair of through cables 726a, 726b, an actuator <NUM>, and a connection <NUM>; redundant explanation of such components is omitted here for clarity. Accordingly, the modules 700b and 700c may also include such components, such as a second pair of through cables 752a, 752b, and associated functionality; however, this is not required.

The modules 700a, 700b, 700c may be daisy-chained or linked to one another, in part, due to the convergence of through cables (that support the groups of foil section) toward connection points. For example, a connection point (e.g., connection point <NUM>) may be a ring, a knot, a pulley, or other point situated between adjacent groups of foil sections. The adjacent groups of foil sections may be connected to one another using the connection point.

In the example of <FIG>, the modular foil system <NUM> includes the first pair of through cables 726a, 726b that supports the foil sections of the module 700a. The modular foil system <NUM> also includes the second pair of through cables 752a, 752b that supports the foil sections of the module 700b. The first pair of through cables 726a, 726b may converge toward the connection point <NUM>. This may allow the module 700a to attach to a discrete assembly of the marine array at the connection point <NUM>. For example, the discrete assembly may be the second module 700b, as shown in <FIG>. As such, the second pair of through cables 752a, 752b may also converge toward the connection point <NUM>. As described herein, because each of the first pair of through cables 726a, 726b and the second pair of through cables 752a, 752b converge toward the connection point <NUM>, foils of the module 700a may articulate relative to foils of the module 700b.

Despite being connected to one another using the connection point <NUM>, the first module 700a may move (or pivot) generally independent from the adjacent module 700b. Further, the connection point <NUM> may provide a demarcation between the first pair of through cables 726a, 726b and the second pair of through cables 752a, 752b, thereby allowing for each of the modules 700a, 700b to have distinct tensions. For example, an actuator associated with the first module 700a may be configured to alter a tension in one or both of the pair of through cables 726a, 726b, and an actuator associated with second module 700b may be configured to alter a tension in one or both of the second pair of through cables 752a, 752b generally independent of the actuator associated with the first module 700a. As described herein, the adjustment of tension in the through cables may influence an angle of attack of the foil sections, and hence the lift generated. Accordingly, because the tension in the first pair of through cables 726a, 726b may be adjusted independent of an adjustment in tension of the second pair of through cables 752a, 752b, an angle of attack (and generated lift) may also be different in each respective module of system <NUM>.

It will be appreciated that the adjustable angle of attack of the modules 700a, 700b is shown and described for purposes of illustration. As shown in <FIG>, the modular foil system <NUM> also includes the third module 700c, which may also have an adjustable angle of attack, for example, substantially analogous to that described with respect to the modules 700a, 700b. In yet other case, the modular foil system <NUM> may have a fourth, fifth, sixth, seventh, or any appropriate number of modules, each linked to one another. In such cases, some or all of the individual modules may also have an adjustable angle of attack.

An exemplary form of a single foil section <NUM> of a modular wing foil system is depicted in <FIG>. The foil section <NUM> is scalable to suit a wide range of lift requirements, while also offering very high aspect ratios. The foil section <NUM> has a body <NUM> with a foil shape having a leading edge <NUM> and a trailing edge <NUM>. The line connecting the leading edge <NUM> and the trailing edge <NUM> passing through the mid-thickness of the body <NUM> is referred to as the "chord line" of the foil shape. When viewed from a top plan perspective, the foil section <NUM> may appear rectangular in shape. A first surface <NUM> extends between the leading edge <NUM> and the trailing edge <NUM> and may be cambered. A second surface <NUM> of the body <NUM> extends between the leading edge <NUM> and the trailing edge <NUM> and may be relatively flat with respect to the first surface <NUM>.

The body <NUM> has two lateral sides <NUM>, <NUM> that extend between the lateral edges of the first surface <NUM> the second surface <NUM> and between the leading edge <NUM> and the trailing edge <NUM>. The body <NUM> may be made from solid cast polyurethane for near-neutral buoyancy and high abrasion resistance and durability. However, the body <NUM> may still be slightly negatively buoyant, such that the body <NUM> will influence the equilibrium angle of attack, especially at low tow speeds. Thus, the downforce achieved by the foil section <NUM> may be influenced by selecting the composition of the body <NUM>.

A first tubular conduit <NUM> may be defined within the body <NUM> and extend laterally through the body <NUM> adjacent to the leading edge <NUM> and open to each of the first and second lateral sides <NUM>, <NUM>. The first tubular conduit <NUM> is sized to receive ropes or cables (such as separation ropes and/or spur lines) of a seismic array therethrough.

A second tubular conduit <NUM> may be defined within the body <NUM> forward of the trailing edge <NUM> and extend laterally therein parallel to the first tubular conduit <NUM> and open to each of the first and second lateral sides <NUM>, <NUM>. The first tubular conduit <NUM> may be positioned within the aft <NUM> percent of the of the cord length of the foil section <NUM>. The second tubular conduit <NUM> may be similarly sized to receive a rope or cable therethrough.

The number of foil sections <NUM> in a modular foil depressor <NUM> or a wing foil system <NUM> is scalable to suit a wide range of lift requirements, while also offering very high aspect ratios. In some cases, this can avoid the need for a supplementary ballast. In other cases, supplementary ballast can be desirable, and integrated with one or more foil sections of the present disclosure, such as those shown below with reference to <FIG>. The foil sections <NUM> may rotate in a flow field. The angle of attack at which the modular foil depressor <NUM> or wing foil system <NUM> can achieve equilibrium will be a function of the moment coefficient of the particular cross-section of the foil <NUM> being used, and the comparative tensions established in the forward through cable <NUM> versus the aft through cable <NUM>. When the aft through cable is completely slack, the center of rotation for the foil section <NUM> will be the forward through hole <NUM>. As the tension balance changes between the forward through cable <NUM> and the aft through cable <NUM>, the center of rotation is transferred to the aft through hole <NUM>, at which point the forward through cable <NUM> acts to prevent further rotation of the foil <NUM> about its center of rotation, thereby setting the new equilibrium angle of attack.

Consequently, the magnitude of downforce generated by a modular foil depressor <NUM> or outward force generated by a wing foil system <NUM> formed by foil sections <NUM> can be controlled by various factors including the following:.

The second rope or cable threaded through the second tubular conduit <NUM> in the foil sections <NUM> of the modular foil depressor <NUM> or wing foil system <NUM> allows for adjustment of the lift by controlling the catenary (billow) of the modular foil depressor <NUM> wing foil system <NUM>. The pair of ropes may be adjusted in length to effect controllable adjustments in lift. The equilibrium angle of attack achieved is a function of the relative lengths of the dual ropes. For example, if the aft rope passing through the second tubular conduit <NUM> in the aft half of the foil sections <NUM> is shortened with respect to the rope passing through the first tubular conduit <NUM>, the trailing edges <NUM> of the depressor sections <NUM> will be pushed closer together laterally as compared to spacing between the foil sections <NUM> at the leading edges <NUM>. This causes the modular foil depressor <NUM> or wing foil system <NUM> to billow and change the angle of attack along the length of the modular foil depressor <NUM> or wing foil system <NUM>.

The modular foil depressor offers high aspect ratios and high lift-to-drag efficiency. The modular foil depressor offers a high degree of flexibility in terms of the number of choices available, including pivot location, camber, chord length, and tail fin size and angle, to selectively adjust the downforce to suit operational requirements and specifications. Lift is also adjustable by adjusting the tension in the cables running through the foils.

The modular foils of the present disclosure can also be adapted to receive a ballast material and/or to add buoyance to the foil. For example, in particular applications, it can be desirable to selectively increase a weight in the foil section. This can enhance the stability of the foil and/or facilitate orientating the foil in a particular configuration. Additionally or alternatively, it can be desirable to add pockets to the foil section that operate to enhance the buoyance of the foil section. In some cases, the same structure of the foil section can be used to facilitate buoyancy enhancement and ballast adding. For example, a pocket, tube, channel, or the like can be formed in the foil section. This pocket or other like structure can define an enhanced buoyance portion of the foil section. The pocket can also be adapted to receive a ballast material, based on the desired application.

<FIG> show example cross-sections of a foil section that can include a buoyancy pocket and/or be adapted to receive ballast material. It will be appreciated that the foil sections show in <FIG> can be used with any of modular foil system described herein. For example, the modular foil systems of the present disclosure can include a plurality of foil sections, and some or all of the plurality of foil sections can include a foil section adapted to include a buoyance pocket and/or to receive a ballast material. In some cases, this can include a combination of foil sections, some of which have a buoyance pocket and/or ballast materials, along with other foil sections that do not necessarily include such features. The example geometries of foil sections of <FIG> are therefore presented for purposes of illustration; in other embodiments, other geometries are contemplated herein.

With reference to <FIG>, a foil section <NUM> is shown. The foil section <NUM> can be substantially analogous to the foil section <NUM> described above, and as such include similar components and/or perform similar functions. In this regard, the foil section <NUM> includes a leading edge <NUM>, a trailing edge <NUM>, a first surface <NUM>, a second surface <NUM>, a first tubular conduit <NUM>, and a second tubular conduit <NUM>. <FIG> also shows the foil section including a first pocket <NUM> and a second pocket <NUM>. The first and second pockets <NUM>, <NUM> can be features formed into a body of the foil section <NUM>. For example, the first and second pockets <NUM>, <NUM> can be channels, bores, through-portions, or other like features that extend through some or all of a cross-dimension of the foil section <NUM>. The first and second pockets <NUM>, <NUM> can be adapted to define a buoyancy-enhanced portion of the foil section <NUM>, such as may be the case where the pockets <NUM>, <NUM> are filled with a material having a less density of the fluid within which the foil section <NUM> is immersed or partially immersed. In other cases, the first and second pockets <NUM>, <NUM> can be adapted to receive a ballast material. The ballast material can generally have a density that is similar to or greater than a density of the fluid within which the foil section is immersed or partially immersed.

With reference to <FIG>, a foil section <NUM> is shown. The foil section <NUM> can be substantially analogous to the foil section <NUM> described above, and as such include similar components and/or perform similar functions. In this regard, the foil section <NUM> includes a leading edge <NUM>, a trailing edge <NUM>, a first surface <NUM>, a second surface <NUM>, a first tubular conduit <NUM>, and a second tubular conduit <NUM>. <FIG> also shows the foil section <NUM> as including a first pocket <NUM>, a second pocket <NUM>, and a third pocket <NUM>. The pockets <NUM>, <NUM>, <NUM> can be substantially analogous to the pockets <NUM>, <NUM> described above in relation to <FIG>. Notwithstanding, the pockets <NUM>, <NUM>, <NUM> can have a different geometry and arrangement on the foil section <NUM>. For example, as shown in <FIG>, the first and second pockets <NUM>, <NUM> are arranged generally between the first and second tubular conduits <NUM>, <NUM>, and the third pocket <NUM> is arranged generally between the second tubular conduit <NUM> and the trailing edge <NUM>. The pockets <NUM>, <NUM>, <NUM> can generally assume a larger cross-sectional area of the foil section than that of the pockets of <FIG>, and thus can be adapted to provide enhanced buoyance or ballast as may be appropriate for a given application.

With reference to <FIG>, a foil section <NUM> is shown. The foil section <NUM> can be substantially analogous to the foil section <NUM> described above, and as such include similar components and/or perform similar functions. In this regard, the foil section <NUM> includes a leading edge <NUM>, a trailing edge <NUM>, a first surface <NUM>, a second surface <NUM>, a first tubular conduit <NUM>, and a second tubular conduit <NUM>. A third tubular conduit <NUM> and a fourth tubular conduit <NUM> are also shown, which may be adapted to receive one or ropes or cables, as described herein in relation to other forward-most conduits of the foil sections described herein. <FIG> also shows the foil section <NUM> as including a first pocket <NUM> and a second pocket <NUM>. The pockets <NUM>, <NUM> can be substantially analogous to the pockets <NUM>, <NUM> described above in relation to <FIG>. Notwithstanding, the pockets <NUM>, <NUM> can have a different geometry and arrangement on the foil section <NUM>. For example, as shown in <FIG>, the first pocket <NUM> can have a first shape and be arranged generally between the collection of the tubular conduits <NUM>, <NUM>, <NUM> and the tubular conduit <NUM>. The second pocket <NUM> can have a second shape and be arranged generally between the fourth tubular conduit <NUM> and the trailing edge <NUM>. With the differing shape of the first and second pockets <NUM>, <NUM> the foil section <NUM> can be adapted to exhibit buoyance and ballast properties that can be different from those exhibited, for example, by the foil section <NUM>. In other cases, other geometries are possible and contemplated herein.

Modular foil depressors applied to umbilicals or other similar type cables can also be scaled by how many are deployed, for example, by daisy-chaining depressor sections at intervals along the cable. As described herein, modular foil depressors, including various combination of foil sections, shapes, systems, and so forth may be used to generate a negative lift (e.g., along a perpendicular direction) that depresses or maintains components of a marine array at a submerged depth.

To facilitate the reader's understanding of the various functionalities of the embodiments discussed herein, reference is now made to the flow diagram in <FIG>, which illustrates process <NUM>. While specific steps (and orders of steps) of the methods presented herein have been illustrated and will be discussed, other methods (including more, fewer, or different steps than those illustrated) consistent with the teachings presented herein are also envisioned and encompassed with the present disclosure.

In this regard, with reference to <FIG>, process <NUM> relates generally to positioning a modular foil system in a marine array. The process <NUM> may be used with any of the foil systems, modular foil systems, and so forth, described herein, such as the foil systems <NUM>, <NUM> and modular foil system <NUM>, and variations and embodiments thereof.

At operation <NUM>, a towed marine, system, array or device is launched. In some cases, the array may include a cable configured to carry a payload and a modular foil system coupled to the cable.

As one example and with reference to <FIG> the seismic array <NUM> may be launched into a marine environment. The seismic array <NUM> may include various cables, such as the cross cable <NUM>. The seismic array <NUM> may also include a modular foil system coupled to the cable, such as the modular foil depressor <NUM>.

At operation <NUM>, positional data is acquired for the towed cable, payload, or other towed device. For example and with reference to <FIG>, one or more sensors of the seismic array <NUM> may determine or detect a position of an instrument payload towed by a vessel.

At operation <NUM>, the acquired positional data is compared with an operational target, such as a target position, for the towed cable, payload, or other towed device. For example and with reference to <FIG>, the seismic array may include one or more processing units, including computer executable instructions, that operate to compare the acquired positional data with a target position. In turn, at operation <NUM>, the processing unit or other associated equipment, may determine the positional data is within operational tolerances. For example, the processing unit and/or other associated component may determine an adjustment parameter for the modular foil system based on the comparing of the acquired positional data and the target position. This adjustment parameter may in turn be used to adjust an angle of attack and control lift of the modular foil system.

For example, at operation <NUM>, an angle of attack may be adjusted for one or more modular foil systems of the array. This may involve adjusting an angle of attack of a foil section relative to other components of the array. For example and with reference to <FIG>, a group of foil sections of a first module 700a may be adjusted relative to an angle of attack of a second group of foil sections 700b. To facilitate the foregoing, a tension in through cables supporting the first group of foil sections may be adjusted independent of a tension in a second pair of through cables that supports the second group of foil sections. Accordingly, the first group of foil sections may generate a lift that is distinct from a lift generated by the second group of foil sections. This may be facilitated by an actuator, such as a dynamic actuator, that uses the adjustment parameter to control the tension and adjust the angle of attack.

The method of <FIG> may, subsequent to the operation <NUM>, return to the operation <NUM>. At the second iteration of the operation <NUM>, the method <NUM> may proceed by acquiring positional data for the towed payload subsequent to the adjustments to the angle of attack of the operation <NUM>. In this regard, the method <NUM> may continue and determine whether the adjustments to the angle of attack achieved the appropriate or desired position of the towed payload. For example, at the second iteration of the operation <NUM> the acquired positional data (for the payload influenced by the adjusted angle of attack of operation <NUM>) is compared with a target position for the towed cable, payload, or other towed device. In turn, at the second iteration of the operation <NUM>, the subsequently acquired positional data is determined to be within operation tolerance.

In this regard, upon a determination at the operation <NUM> that the acquired positional data is within operation tolerance, the method <NUM> may proceed to operation <NUM>. At the operation <NUM>, towing may be continued (or commenced) for the marine system, array, or device.

<FIG> depicts another embodiment of a marine array. In particular, <FIG> shows a marine array <NUM>. The marine array <NUM>, as within any of the marine arrays described herein, may be, or be associated with, a seismic array, a fishing trawl, a military application, an oceanographic study, and/or substantially any other maritime application. The embodiment of <FIG> shows the marine array having towed cable and payload that is steered or positioned within a marine environment by a starboard and a port biased foil system.

To facilitate the foregoing, the marine array includes a vessel <NUM>. The vessel <NUM> is shown positioned along a surface of an marine environment <NUM>. Attached to the vessel <NUM> is a tow cable <NUM>. The tow cable <NUM> may be towed through the marine environment <NUM> by the vessel <NUM>. The tow cable <NUM> may carry or pull a towed body or other payload <NUM> through the marine environment <NUM>. In some cases, a streamer cable <NUM> may be pulled by the towed body <NUM> through the marine environment <NUM>.

It may be desirable to steer, position, stabilize, and so on the towed body <NUM> and associated components within the marine environment <NUM>. In this regard, <FIG> shows the marine array <NUM> including a first foil system <NUM> and a second foil system <NUM> coupled with the towed cable <NUM>. The first foil system <NUM> and the second foil system <NUM> may be substantially analogous to any of the foil systems described herein. As such, the first foil system <NUM> and the second foil system <NUM> may each include a group of foil sections collectively defining an angle of attack and thus be configured to generate lift.

In one embodiment, the first foil system <NUM> may have an angle of attack that causes the first foil system <NUM> to generate lift that biases the towed cable <NUM> toward a starboard direction. Further, the second foil system <NUM> may have an angle of attack that causes the second foil system <NUM> to generate lift that biases the towed cable <NUM> toward a port direction. In this regard, the first foil system <NUM> and the second foil system <NUM> may counteract one another and thus help stabilize or otherwise control a position of the towed body <NUM> in the marine environment <NUM>. In some cases, the angle of attack of one or both of the first foil system <NUM> or the second foil system <NUM> may have an adjustable angle attack, which may be manipulated to help steer the towed body <NUM>, as may be appropriate for a given application.

For example, features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations. Also, as used herein, including in the claims, "or" as used in a list of items prefaced by "at least one of indicates a disjunctive list such that, for example, a list of "at least one of A, B, or C" means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Further, the term "exemplary" does not mean that the described example is preferred or better than other examples.

Claim 1:
A marine array (<NUM>, <NUM>), comprising
a cable (<NUM>, <NUM>, <NUM>) configured to be towed by a vessel (<NUM>, <NUM>) and carry a submerged payload (<NUM>) through a marine environment (<NUM>); and
a modular foil system (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) coupled with the cable (<NUM>) and configured to bias the submerged payload (<NUM>) toward a target position,
wherein the modular foil system (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) includes a group of foil sections (<NUM>, <NUM>, <NUM>) collectively defining an angle of attack, and a pair of through cables (526a, 526b, <NUM>, <NUM>, 726a, 726b) coupling the foil sections (<NUM>, <NUM>, <NUM>) within the group of foil sections (<NUM>, <NUM>, <NUM>) to one another within the modular foil system (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) and converging toward a connection point (<NUM>, <NUM>, <NUM>, <NUM>),
wherein the modular foil system (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) includes a first duct (<NUM>) and a second duct (<NUM>), each duct extending through the group of foil sections (<NUM>, <NUM>, <NUM>), and
wherein the pair of through cables (526a, 526b, <NUM>, <NUM>, 726a, 726b) includes a first through cable (<NUM>) and a second through cable (<NUM>) extending through the first and second ducts respectively.