Assembly for at least acoustically camouflaging an underwater element to be protected, and use thereof

Abstract

The rudder systems of yachts are increasingly being damaged by Iberian orcas off the French, Spanish and Portuguese Atlantic coasts and in the Alboran Sea. Attempted countermeasures are insufficient or forbidden. The invention proposes camouflaging the rudder (04), as an underwater element (02) to be protected, especially acoustically by a rudder protection means (03) as a camouflaging element (44) and thereby protecting the rudder from damage. For this purpose, a curtain (06) which, in the event of use, completely or at least partially axially surrounds the rudder (04) is provided as the rudder protection means (03), the bodies (08) of which curtain have a significantly different characteristic acoustic impedance (r) than water. The curtain produces strong echoes of the biosonar of the orcas, and said echoes obscure (generation of blurred contours for confusion) and / or conceal (generation of invisibility) the echo signal of the rudder (04). The rudder protection means (03) can be in the form of a hanging curtain (07) composed of chains (09) or lines (41) (acoustic, visual and haptic protective effect) or in the form of a rising curtain (27) (with bubble curtain (26), acoustic and visual protective effect). The rudder protection means (03) can be installed and activated very quickly in the event of use or can also be permanently integrated into the rudder (04).

Description

[0001] Applicant

[0002] Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany

[0003] Designation

[0004] Arrangement for at least acoustic camouflage of an underwater element to be protected and application thereof

[0005] Description

[0006] The invention relates to an arrangement for at least acoustic camouflage of an underwater element to be protected against human animals emitting biosonar signals by providing a camouflage element with a characteristic acoustic impedance different from water, which surrounds the underwater element to be protected and generates acoustic reflections of the biosonar signals, and to an application of the arrangement.

[0007] Echolocation in animals, also called echolocation or biosonar, serves their orientation in space and the localization of prey. To do this, they actively emit sound waves in the form of biosonar signals (e.g. "echolocation clicks"), whose echoes they detect and process (presumably for imaging purposes). Echoes arise at interfaces between volumes with different acoustic impedances (characteristic value, defined as the product of the density of the volume and the speed of sound in the volume), such as at the transition from water to air bubbles, between animal soft tissue and swim bladders, or between animal soft tissue and bones of male animals. The greater the difference in acoustic impedance between different volumes, the more intense the echo. Among male animals, echolocation is used by toothed whales (including sperm whales, orcas, porpoises, and dolphins).Iberian orcas are currently attracting media attention, particularly for their unwanted interactions with the rudders (the underwater elements that need to be protected) of sailing yachts.

[0008] In general, the intensity of reflection at an interface between two transmission media 1 and 2 is described by the dimensionless sound reflection factor r. This is defined – under the boundary condition of perpendicular sound incidence – as the ratio of the sound pressures PT of the reflected wave and p eof the incident wave at the interface. The sound reflection factor r is calculated from the characteristic sound impedance Zi (characteristic sound impedance "wave resistance" of the transmission medium) of the transmission medium 1 in front of (from the direction of the emitted sound signals) the sound-reflecting interface (in the invention, water) and Z2 of the transmission medium 2 behind (from the direction of the emitted sound signals) the sound-reflecting interface (in the invention, the camouflage element or its material). r = (Z2-Zi) / (Z2+Zi)

[0009] The absolute value of the sound reflection factor 1 cannot exceed the value 1. In the special case where the sound impedance Z2 approaches infinity, the sound reflection factor r assumes its largest possible value: r = (+)1 (sound-hard interface). The same applies to the special case where the sound impedance Z2 is 0: r = (-)1 (sound-soft interface). In both cases, the incident sound signals are completely reflected, resulting in particularly effective sound insulation for the transmission medium 2 behind the sound-reflecting interface. It is not reached by any sound signals and therefore cannot reflect any. The sound impedances Zi of the transmission media i are in turn the product of their density pi and the speed of sound Vi of the signal in the respective transmission medium i.Accordingly, the invention allows the sound reflection factors r for the transfer of water into the corresponding transmission medium at the interface to be calculated for various transmission media behind the interface (in the invention, the camouflage element) and for the transmission medium in front of the interface (in the invention, water). A table is provided in the specific description.

[0010] In the context of the present invention, the term "camouflage" by a camouflage element is divided into two sub-terms: Firstly, the camouflage element can "disguise" the underwater element and allows some or all of the sound energy to pass through, while the remaining sound energy is reflected by the camouflage element. Toothed whales can only perceive unclear contours of the underwater element, as if through a veil. Secondly, the camouflage element can "cover" the underwater element and prevent any sound energy from passing through, resulting in complete "concealment" for the toothed whales. The toothed whales can no longer perceive the underwater element. It is completely concealed.

[0011] State of the art

[0012] The closest prior art to the invention is known from US 11 311 004 B2. Here, live fish without swim bladders (specifically sablefish, Greenland turbot, and halibut) are used as underwater elements, acoustically camouflaged by a special rigid net cage suspended in the water column as a camouflage element, i.e., their reflected sound signals are partially covered or attenuated. The net yarn used for this purpose is made of UHMWPE (ultra-high-molecular-weight polyethylene, density approximately 0.97 kg dm -3 ) or polyamide 6 or 6.6 (density approximately 1.15 kg dm -3 ), whose densities and derived acoustic impedances differ only slightly from the density (approximately 1 .03 kg dm' 3) and acoustic impedance of sea water. The sonar pattern of the fish trap created in this way overlaps with the sonar pattern of the fish in the trap, which is intended to make it more difficult for the orcas to perceive the fish (whose reflection signal is weak anyway, as they have no swim bladder and thus roughly the same density as water) in the trap. However, no empirical confirmation of successful use has been provided. It can be assumed, however, that due to the small differences in acoustic impedance, the reflection signals are only disturbed, so that the perception of the fish in the trap is at best disguised rather than hidden. The familiar fish trap cage is a passive element and can only protect fish that actively swim into it. It cannot adapt to underwater elements.

[0013] A scientific publication on camouflaging gillnets with acoustic reflectors to minimize bycatch of toothed whales is by IMF Kratzer et al.: "Determination of Optimal Acoustic Passive Reflectors to Reduce Bycatch of Odontocetes in Gillnets" (in Frontiers in Marine Science, July 2020, Volume 7, Article 539). In this study, the underwater object (gillnet) is made echolocatable by the toothed whales using acoustic reflectors. This attracts their special attention and prevents them from accidentally swimming into the gillnets.

[0014] Since 2020, Iberian orcas (a killer whale population (Orcinus orca) classified as "critically endangered" on the Red List, which feeds primarily on bluefin tuna (Thunnus thynnus) and is native to the French, Spanish, and Portuguese Atlantic coasts and the Alboran Sea) have increasingly been damaging the rudders of smaller yachts and boats. See, for example, the publication by R. Esteban et al.: "Killer whales of the Strait of Gibraltar, an endangered subpopulation showing a disruptive behavior" (Mar Mam Sci. 2022;38: 1699-1709). This often damages not only the rudder blade but also its mounting, which has led to water ingress into the yachts and, in some cases, their sinking. Accordingly, the expert community is searching for solutions for effective rudder protection. From Bobby Schenk’s blog (“Defense tools against orca attacks? (accessed on June 13, 2023, at https: / / www.bobbyschenk.de / trick / trick152.html), for example, it is known that ropes, sand, pingers, explosives, or sound tubes have been used to scare away orcas. However, these measures are either ineffective or strictly prohibited, as is the already used shooting of orcas with signal ammunition. The Cruising Association's freely accessible webinar "Orca and Yachts: Fact, Fiction, and Fear" (in English, 7:00 p.m., May 18, 2023, video available at https: / / www.theca.org.uk / news / rats / orca-webinar-vi- deo , as of July 27, 2023, link on YouTube: youtu.be / dwi_O9m2394; ) shows that orcas usually swim up to the rudder from behind and scout it out before damaging it.It is speculated that deploying warps and lines, anchor chains, dropping sand, and generating propeller movements could be a way to ward off orcas, either through the resulting haptic distraction or by disrupting the rudder's sonar pattern (recording from 1h:23min:24s). However, no specific implementation details are given below. Furthermore, it is suggested that the rudder shape could be mechanically altered by spikes or a "mite chain" (recording from 1h:41min:15s) to trigger negative haptic sensations upon contact.

[0015] From DE 10 2017 104457 A1, it is also known to create a bubble curtain underwater using an air hose in order to minimize the propagation of anthropogenic noise (e.g., drilling noise) through the air bubbles. From DE 2008 017418 A1, it is known to stretch a net with gas-filled buoyancy bodies around the noise source for the same purpose. The buoyancy bodies impede the propagation of sound away from the noise source. Finally, from DE 102 05 159 A1, it is known to reduce vibrations and pressure waves on a ship's hull by providing gas outlet elements in the ship's hull near the propeller, with escaping gas bubbles inhibiting sound propagation. All three applications involve reducing the sound level of anthropogenically generated noise in the ocean in order to protect marine fauna.The principles of echolocation and camouflage - which form the basis of the present invention - do not apply.

[0016] From DE 103 02 219 B4 it is known to surround a pile to be driven into the waterbed with hose rings arranged one above the other, which have knobs for sound reflection on the inner side facing the pile. In one embodiment, the hose rings can hang in the water column. From DE 10 2012 013 443 A1 it is known to lay a multi-perforated ring line on the waterbed around a pile, with compressed air escaping from the holes and forming a bubble curtain. From DE 10 2008 017 418 A1 it is known to surround a driven pile with a net into which air-filled hollow bodies are integrated. From DE 10 2014 113 676 A1 a hydro sound damper is known which has sound reduction elements connected to a flexible support structure, for example a net, and to holding elements.All of the aforementioned intellectual property rights have in common that they are intended to reduce the propagation of sound underwater during pile-driving. CH 671 788 A5 discloses a net for intercepting objects, which is positioned in a river using retaining elements. CN 2 04 514 567 U discloses a simulator for a bubble field behind the propeller of a model ship. The compressed air escapes through a microporous rudder imitation.

[0017] Task

[0018] Based on the generic arrangement described above, the object of the present invention is to further develop it so that effective, cost-effective, and easy-to-use protection of a specific underwater element can be achieved by means of at least acoustic camouflage. The inventive solution to this problem is set out in the main claim. Advantageous further developments of the inventive arrangement are set out in the subclaims. A preferred application is shown in the application claim and its subclaim.To achieve the object, the invention provides that the camouflage element is designed as a rudder protection in the form of a flexible curtain, by which the underwater element to be protected, which is designed as a rudder of a boat, can be completely or partially surrounded axially while forming a radial distance, wherein the sound characteristic impedance of the rudder protection is characterized by a sound reflection factor r as a measure of the strength of the reflection of the biosonar signals at the rudder protection, which has a value equal to or greater than 0.5.

[0019] The invention achieves the stated object by providing a rudder protection in the form of a curtain around the rudder to be camouflaged, which at least acoustically (and optionally also visually and haptically, see below) conceals the rudder, which has a significantly higher sound reflection factor than the prior art (|r| between 0.5 and 1.0 inclusive of 0.5) and thus results in significantly better camouflage of the rudder to be protected. The following applies: the closer the value of the sound reflection factor is to 1, the better the camouflage effect. Therefore, according to a first modification of the invention, it is particularly advantageous and preferred if the sound reflection factor r is equal to or greater than 0.75. To achieve this particularly good camouflage effect, the curtain is located between the rudder to be camouflaged and the bioacoustic sound source, i.e. the male animals using bioecholocation, in order to disguise or conceal the rudder from their biosonar.The rudder guard according to the invention can be easily adapted to any rudder to be camouflaged. The strength of the camouflage achieved by the rudder guard depends on its sound reflection factor, in particular on its structural design and material. With "acoustic camouflage," the echo of the rudder when exposed to biosonar is masked by the echoes of other nearby underwater objects (e.g., the air bubbles of the rising curtain), making it more difficult to detect or identify as such. With "acoustic masking," the rudder is partially or completely shielded from the biosonar of the male animal, so that, in the best case, it becomes completely "invisible" to the animal. The following table provides an overview of characteristic parameters:

[0020] In particular, the materials according to 2, 3, and 4 are suitable for use in the invention. The materials according to 5 and 6 refer to the closest prior art to the invention. The significant differences in the sound reflection factor r (last column of the table) are clearly visible, with the sound reflection factors r of materials 5 and 6 lying well outside the range claimed by the invention and unable to ensure adequate camouflage of an underwater element to be protected.

[0021] In the invention, the rudder to be camouflaged is simply covered with a rudder protector in the form of a "curtain." This rudder protector completely or partially encloses the rudder, which can be stationary or movable, at a radial distance, thus forming a cylindrical shell around it. The radial distance of the curtain from the rudder is intended to reliably prevent physical contact between the male animal and the rudder. Even water movements or movements of the rudder do not significantly open the curtain; rather, they contribute to a blurring of the acoustic (or possibly also optical) reflection signal from the curtain, further enhancing the camouflage.By designing the curtain with elements whose acoustic impedance differs significantly from the acoustic impedance of seawater, so that the resulting value of the sound reflection factors r optimally approaches the value 1, the curtain generates a sonar echo that is perceived as dominant by the echolocating male animals and thus significantly reduces or even eliminates the detectability of the rudder to be camouflaged.

[0022] The rudder protection according to the invention, in the form of a simple curtain open on one side, is flexible and can move in the water like a curtain in the air. It can camouflage any type of rudder, even those with very complex structures and contours. According to a further advantageous and preferred modification of the invention, the rudder protection is designed either as a hanging curtain composed of a plurality of adjacently arranged bodies or as a rising curtain composed of a plurality of rising air bubbles. Thus, the curtain either hangs independently in the water column if it consists of downforce-weighted bodies, or it continuously rises independently in the water column if it consists of buoyancy-driven elements.In the first embodiment, the bodies are arranged in a fixed position in the hanging curtain, deliberately avoiding a horizontally and vertically knotted net in which the marine animals could become entangled. In the second embodiment, the buoyancy-driven elements ("air bubbles") in the ascending curtain continuously migrate toward the water surface, with new bubbles constantly being generated at the lower end of the curtain. Although the air bubbles are not connected to each other, they remain close together due to the vertically upward buoyancy force acting on them and swirl, which significantly disrupts the reflected sonar image, thus beneficially disrupting it.

[0023] The curtain-shaped rudder protection claimed in the invention guarantees, during operation, at least acoustic (and possibly also optical and haptic, see below) camouflage (from effective concealment to complete concealment) of boat rudder systems from echolocating marine animals (toothed whales) and offers several advantages over previously discussed proposals. Both the hanging and the rising curtain

[0024] • are legal,

[0025] • are easy to handle,

[0026] • are cost-effective due to their simple construction,

[0027] • can be sold or rented commercially,

[0028] • In contrast to firecrackers or sea rescue rockets, they avoid the risk of acoustic trauma to the animals,

[0029] • can be used repeatedly and for as long as necessary, unlike most other proposed measures (such as sand releases, firecrackers and sea-launched rockets, which are limited in supply), and

[0030] • allow the integration of additional devices to prevent toothed whales or other marine creatures from becoming entangled, if necessary by means of predetermined breaking points integrated into the curtain.

[0031] In addition, the hanging curtain

[0032] • intrinsically risk-free with regard to entanglement of toothed whales or other marine life, as the curtain consists of individual strands that can be freely moved against each other,

[0033] • constructed from only the simplest technical components (chains or cords with acoustic reflectors, buoyancy and lines) and

[0034] • purely passive and therefore technically very easy to handle without any special aids, while the rising curtain

[0035] • is intrinsically risk-free with regard to entanglement of toothed whales or other marine life, since the curtain primarily consists of air bubbles, • is constructed from only the simplest technical components (air compressor, air-conducting elements, lines),

[0036] • can be operated especially during possible movement of the rudder to be protected.

[0037] The hanging curtain can be designed in various modifications. It is advantageous and preferred if it consists of a plurality of adjacently arranged chains with vertically interconnected links or of a plurality of adjacently arranged cords. In the case of chains with links, these can preferably and advantageously be formed from rings (solid or hollow), beads (solid), or spheres (hollow). The links can form the chains themselves or be attached to them. In these embodiments, the hanging curtain takes the form of a simple "fly curtain." It consists of a series of individually suspended chains or cords whose acoustic impedance differs significantly from the acoustic impedance of seawater. Therefore, the biosonar signal of the toothed whales is reflected by them, and the underwater element behind them is masked or shielded.Density and acoustic impedance of the materials used in the invention can be either higher than the density and acoustic impedance of sea water (density approximately 1.0 kg drrr. 3 ), for example stainless steel (density approximately 7.9 kg drrr 3 , resulting sound reflection factor + 0.940), aluminum (density approximately 2.7 kg drrr 3 resulting sound reflection factor + 0.846 or corresponding plastics, or it can be significantly lower, e.g. air-filled spheres (density approximately = 0.001 kg drrr 3 , resulting sound reflection factor of the enclosed air - 0.999). This results in corresponding sound reflection factors whose magnitude is equal to or above 0.75 and as close as possible to 1.

[0038] If the hanging curtain with its chains or cords does not already have sufficient buoyancy (so that it hangs vertically in the water column), it is preferable and advantageous to also provide the chains or cords with buoyancy elements. These can be, for example, small weights or chain links at the end of each chain or cord. The chains and cords are not connected to each other, so the curtain does not form a net-like structure in which marine life could become entangled.

[0039] To optimize the individual suspension of the chains or cords, a further modification can preferably and advantageously provide for all chains or cords to be attached at a distance from one another to a connecting element that can be arranged in the water above the rudder, wherein the chains or cords are of such a length that they extend below the rudder when arranged. The connecting element can be, for example, a bracket, a rail, or a tube. The length of the chains or cords ensures that the rudder is completely acoustically camouflaged over its entire height. Should the inherent buoyancy of the connecting element be insufficient, it can preferably and advantageously have buoyancy elements.

[0040] These hold the hanging curtain on the water surface and stretched out. Their volume must be adjusted to the weight of the curtain in the water. The buoyancy elements can be, for example, individual fenders (oval or cylindrical, optionally supplemented by fiberglass rods to stretch the curtain as horizontally as possible, e.g. plug-in tent poles) or a buoyancy aid ("pool noodle"). To ensure that the connecting element securely surrounds the rudder axially, it can be curved and made of one piece. It can also preferably and advantageously be foldable and / or multi-part. With a foldable design, the connecting element can be mounted on or on a device and folded into the water when necessary. It can also have multiple joints and be folded together for storage. Alternatively, it can also be made of several parts, so that the rudder is axially protected by several curtains.

[0041] In addition to the hanging curtain, the invention also claims the alternative variant of the rising curtain, which operates according to the same principle of concealment or masking. The rising curtain is formed from air bubbles and provides very good acoustic camouflage for the underwater element to be protected, since air (density approximately 0.001 kg / cm³) 3 ) a significantly lower density than water (density approx. 1 .0 kg drrr 3). Consequently, the rising air bubbles reflect the biosonar of the echolocating male animals very well, creating an intense sonar pattern that conceals the rudder well and, due to the individual movement of the bubbles, is dynamic and blurred. Due to the particularly strong reflection of the biosonar on air bubbles, the bubbles also conceal the rudder to be protected very well. The interaction of concealment and masking makes the rudder to be camouflaged completely unrecognizable and invisible to the echolocating male animals (see also the sonar images in Fig. 9 and 10). Furthermore, the strong light refraction on the air bubbles in the water also makes the rudder to be protected visually unrecognizable, see below.

[0042] The rising air bubbles of the rising curtain are generated beneath the rudder to be protected. The structural implementation basically consists of an extending rigid element with air nozzles (air outlet openings), which can be arranged as horizontally as possible beneath the rudder to be protected, and an air supply via which the air is pumped under pressure through the openings into the water. According to a preferred and advantageous embodiment, the rising curtain can be provided with an air hose having a plurality of openings, which is connected to a compressed air supply and can be arranged largely horizontally beneath the rudder, wherein the size, number, and density of the openings, as well as the compressed air supply, are variable. The air pressure can even be changed on-site and thus adapted to the current situation; the structural measures must be optimized in advance through experiments.This allows the effectiveness of the rising curtain in terms of acoustic (and also visual camouflage, see below) to be varied and adjusted. With appropriate weighting, a perforated air hose is an extremely simple means of creating the bubble curtain with the rising curtain. The air hose is either already so stiff that it can be aligned as horizontally as possible and remains so, or it is stiffened accordingly. In the simplest case, the air hose can simply be thrown out in an arc behind the rudder to be protected. With a moving rudder, the thrown air hose can also simply be pulled behind it. To supply compressed air, the air hose can preferably and advantageously be connected to a largely vertically arranged air supply pipe.This can be connected to a compressed air supply device, for example a compressor, and can simply be immersed in the water from a location above the water and the rudder to be protected.

[0043] The air tube can be constructed in multiple parts and assembled in a polygonal configuration. It can also be constructed in one piece, with the air supply tube attached to one or both sides of the air tube. This ensures that the entire air tube is well filled with air. The air tube can also be curved, for example, in a semicircle. This allows it to surround the rudder to be protected rearward (i.e., opposite the toothed whales' preferred swimming direction) with the resulting rising bubble curtain.

[0044] For all external (outside the rudder to be protected) design measures for implementing the rudder protection, it is preferred and advantageous, according to a further modification, if the protection comprises a fastening device with a predetermined breaking element. This allows the rudder protection to be securely attached in the vicinity of the rudder to be protected, but it can also be easily and, above all, quickly removed in the event of an accident. Any loss of the rudder protection is a calculable risk. As an alternative to an external temporary device for generating the bubble curtain of the rising curtain, the invention can also advantageously provide for the rising curtain to comprise an air outlet device that can be permanently integrated into the rudder to be protected and that is connected to a compressed air supply directly or via the rudder (the steering system).The design measures are certainly more complex than with an external device for generating the bubble curtain, but handling is easier because only the compressed air supply needs to be activated (deactivated) to generate and deactivate the rising curtain. This can be done very quickly. The immersion of external structural elements to generate the rising curtain is eliminated. Preferably and advantageously, according to a further modification of the invention, the air outlet device can comprise an air plate having openings, which can be permanently arranged at a lower end of the rudder. The compressed air supply can be fed directly to the air plate via a dedicated supply line or through the rudder to be protected. The term "air plate" used is to be understood merely as a placeholder for a suitable structural element.It can be a plate, a ring, a tube, a type of "winglet," or a "foil" at the end of the rudder, with the air outlets positioned at a distance from the rudder. However, the attached air plate must not interfere with the function of the rudder. The shape of the rising curtain can be adjusted by the number and density of the openings, as well as the compressed air supply.

[0045] The invention relates to a technical arrangement for at least acoustic (and possibly also visual and even haptic) camouflage of a boat's rudder for its protection. As explained above, the invention primarily achieves acoustic camouflage. Acoustic camouflage is to be regarded as a primary measure. Furthermore, the arrangement claimed by the invention is also capable of visually camouflaging the rudder to be protected. The difference in density between the rudder and the water is also associated with a reflection of optical waves. This can also be perceived by the eyesight of echolocating marine animals. In other words, by providing the rudder protection according to the invention, orcas are less able to see the rudder to be protected, or even unable to see it at all.It is therefore advantageous and preferred according to a next development of the invention if the rudder protection also has optical reflective properties. The visual camouflage then adds to the acoustic camouflage, and the combination can encourage the male animals to refrain from interacting with the rudder to be protected. The visual camouflage is achieved via strong surface reflection on the rising or hanging curtain. This prevents light rays detectable by the marine animals from falling onto the rudder to be camouflaged. The reflective surfaces can be formed, for example, by metals or high-gloss plastics. Air bubbles in the water, with their "metallic" appearance, also have a high optical reflectivity due to the high density difference to water.

[0046] In addition to acoustic and visual camouflage and shielding, the rudder guard claimed by the invention, in its suspended form with chains or cords, also provides haptic protection for the underwater element to be protected. The chains or cords are tactilely perceptible to marine animals upon contact and can irritate and deter them accordingly. Thus, the invention of the rudder guard in the rising curtain form can provide double protection (acoustic and visual, with the air bubbles also being able to provide haptic protection) and triple protection (acoustic, visual, and haptic) in the hanging curtain form.

[0047] The rudder protection claimed in the invention, in the form of a hanging or rising curtain, serves to protect a boat's rudder from damage by echolocating marine animals, primarily toothed whales. The term "rudder" refers to both the rudder blade and the rudder system and rudder suspension in the water area. Yacht rudder blades are usually made of an air-filled foam core or hollow aluminum body, both of which have a very high echo intensity (echo strength) that can only be concealed by a camouflage element with an equally strong or stronger echo intensity (and thus sound reflection factor). As already mentioned at the beginning, rudders and rudder blades of boats, in addition to fishing boats, increasingly also private boats and yachts, are increasingly being contacted by orcas, which are echolocating toothed whales, although the reason for this behavior is still completely unclear.This has resulted in and can result in massive damage to the rudder and hull, requiring expensive repairs and even sinking the boat. The invention offers a design solution that can effectively reduce the risk of such damage. While the physical and sensory principles of the invention are understood and plausible, the reaction of orcas to the rudder protection claimed in the invention is still unknown and can only be verified through future field studies.

[0048] The initial recommendations issued by official sources in sailing circles were to bring the boat to a standstill and play "dead." However, this approach was not particularly successful, and affected sailors (in the passage area along the currently particularly endangered French-Spanish-Portuguese Atlantic coast, as well as in the Alboran Sea, western Mediterranean, and in contact with Iberian orcas) attempted and discussed further legal and illegal measures (throwing lines, sand or fireworks, using pingers or sound tubes). Later, official sources recommended speeding up and sailing into shallow, near-shore waters because toothed whales do not follow them there, although this has not yet been systematically proven. It should be noted that most of the yachts damaged by orcas to date only travel significantly slower than orcas can swim, meaning they cannot be "left behind."According to a modified application of the invention, it is advantageous and preferred if the rudder protection in the form of a hanging curtain is used on a stationary boat and the rudder protection in the form of a rising curtain is used on a stationary or moving boat. When the boat is stationary, the hanging curtain cannot become jammed in the rudder system or the drive. Likewise, when the boat is stationary, the rising curtain with its bubble curtain can also be used, although this requires an air compressor. On a moving boat, however, the rising curtain should preferably be used to eliminate the risk of the chains or cords of the hanging curtain becoming tangled and to avoid slowing down the boat. When traveling very slowly, the type of curtain used is a matter of discretion.The hanging curtain can be attached to a stationary or slowly moving boat, depending on its design, using a fastening device, for example, on the railing, the pushpit, or the backstay. The attachment can be made using ropes, for example. These can be supplemented with spacers, such as fiberglass rods, to ensure the curtain remains taut. The lines are attached to the boat, for example, at the base of the railing, using a slip knot and / or lightweight snap hook. This allows for quick or automatic release if a toothed whale catches the hanging curtain. A predetermined breaking element, such as a pre-notched connecting plate, can then also be located in the area of ​​the attachment. Further explanations of the present invention and its respective modifications and applications can be found in the exemplary embodiments shown below.

[0049] The acute risk of damage to a yacht's rudder by killer whales requires the camouflaged rudder protection to be deployed quickly and safely for the sailors. For this purpose, the rudder protection claimed in the invention can be stored pre-assembled in the form of a hanging curtain, for example, in a tube similar to a jib cover, on the boat. Securing lines (floating lines, short and long floating lines) are used for deployment. During deployment, for example, the zip of the tarpaulin is opened and, at slow speed, the curtain is thrown overboard to the side aft. The curtain unfolds aft / downward. As soon as it is fully deployed, the engine is stopped, and the longer floating line on the opposite bow is pulled in tightly until the hanging curtain forms a semicircle around the rudder. The hanging curtain can also simply be thrown overboard and then secured on board.To deploy the rising curtain, the hose assembly located on deck can be deployed and the air supply (compressor and compressed air cylinder) can be started. If an air outlet device is permanently integrated into the rudder blade, only the compressed air supply needs to be started for the rising curtain to form a bubble curtain.

[0050] This invention is based on reports suggesting that orcas first explore a rudder acoustically before attempting to damage it. This led to the idea that these attacks would be less likely if the orcas could not detect the rudder acoustically (and possibly also visually), meaning it was camouflaged (disguised and / or concealed). However, use of the system is at your own risk and without guarantee of success, and is the responsibility of the respective captain. Toothed whales, especially orcas, are intelligent, learning creatures whose behavior is unpredictable.Possible, but based on current knowledge, unlikely, reactions could include: biting or becoming entangled in the curtain, increased curiosity due to the unfamiliar situation, increased aggression due to a lack of success (damage or destruction of the rudder), and increased playfulness due to the buoyancy bodies on the surface. It is assumed that the curtain claimed in the invention poses no danger to the animals and can protect both animals and boats from injury and damage.

[0051] Examples of implementation

[0052] In the following, the rudder protection claimed with the present invention for the acoustic camouflage of a rudder and its preferred modifications and applications in exemplary embodiments are explained in more detail for a better understanding of the invention.

[0053] Fig. 1 is a schematic side view of a hanging curtain on a boat with a rudder as the underwater element to be protected with three detailed views,

[0054] Fig. 2 is a schematic plan view of the hanging curtain according to Fig. 1,

[0055] Fig. 3 is a schematic side view of a rising curtain on a boat with a rudder as the underwater element to be protected,

[0056] Fig. 4 is a schematic plan view of the rising curtain according to Fig. 3,

[0057] Fig. 5 is a schematic view of an arrangement for generating an ascending process with a detail,

[0058] Fig. 6 is a schematic view of another arrangement for generating an ascending process in a first embodiment,

[0059] Fig. 7 is a schematic view of another arrangement for producing a rising curtain in a second embodiment,

[0060] Fig. 8 a sonar image of a stern of a boat and a rudder as an underwater element to be protected (state of the art),

[0061] Fig. 9 a sonar image of the stern and rudder according to Fig. 8 with a hanging curtain and

[0062] Fig. 10 a sonar image of the stern and rudder according to Fig. 8 with a rising curtain.

[0063] Fig. 1 schematically shows an arrangement 01 for the acoustic camouflage of an underwater element 02 against echolocating male animals (in the example, Iberian orcas as a subgroup of toothed whales). The arrangement 01 comprises a camouflage element 44 in the form of a rudder guard 03, which surrounds the underwater element 02 and has a significantly different acoustic impedance than water and thus very good acoustic reflection properties. These allow the rudder guard 03 to appear prominently in the orcas' biosonar. As a result, other objects detectable by the orcas and located in the same direction are both acoustically obscured (blurred contours) and acoustically concealed (invisible), making them difficult or even impossible for the orcas to detect.The underwater element 02 to be protected is a rudder 04 (this refers to the rudder blade, the rudder system, the rudder rods) of a boat 05 (in the illustrated embodiment, this is a small yacht). The rudder protection 03 is intended in particular to protect against damage caused by orcas. For this purpose, the rudder protection 03 is designed as a curtain 06 that completely or partially surrounds the rudder 02 axially (in direction A). Furthermore, the curtain 06 has a radial distance (in direction R, compare Fig. 2, for example, approx. 1 m) from the rudder 04 in order to create a spatial distance between the two. In the illustrated embodiment, the rudder protection 03 is designed as a hanging curtain 07, which consists of a plurality of bodies 08 arranged next to one another. In Fig. 1 it can be seen that the hanging curtain 07 hangs vertically downwards and projects below the rudder 04 and completely covers it.The hanging curtain 07 shown not only provides acoustic camouflage, but also visual camouflage and a haptic distraction.

[0064] In addition to the bodies 08, which in the illustrated embodiment consist of metal chains 09 hanging side by side (left detailed view), the hanging curtain 07 also comprises a connecting element 10 and propulsion elements 11. These are used when the inherent propulsion of the bodies 08 is not sufficient to position them vertically in the water. In the illustrated embodiment, the connecting element 10 consists of a continuous rope 12 to which buoyancy elements 13 are attached. This holds the rope 12 at the water surface 14 and the hanging curtain 07 begins there, so that the rudder 04 is reliably concealed. The buoyancy elements 13 are designed as elongated fenders 15. In the illustrated embodiment, the connecting element 10 is shown in one piece. However, it can also be designed in several parts and / or be foldable (down from the boat 05).In the illustrated embodiment, the propulsion elements 11 are formed by individual weights 16, which allow the curtain 07 to "float through" and minimize the risk of entanglement. The hanging curtain 07 is attached to the boat 05 by means of a fastening device 17. In the illustrated embodiment, these are two short floating lines 18 and two long floating lines 19. They are attached to the boat 05 via predetermined breaking elements 20. In the illustrated embodiment, these are shackles 21 that can be released depending on the load force.

[0065] The left-hand detailed view in Fig. 1 shows a first embodiment in the area of ​​the bodies 08 that make up the hanging curtain 07. Shown are chains 09 whose links 24 consist of interlocking rings 25 made of shiny aluminum. The chains 09 are arranged next to one another but are not connected to one another to prevent the formation of a net. The chain 09 shown is a simple, commercially available insect screen. The central detailed view in Fig. 1 shows a variant of the hanging curtain 07 with cords 41, wherein the cords 41 have a significantly greater acoustic impedance than the surrounding water so that they generate a detectable acoustic echo. The right-hand detailed view shows an embodiment of the hanging curtain 07 with solid beads 42 as bodies 08, whose acoustic impedance is also greater than that of water.They can also be air-filled spheres with a characteristic acoustic impedance that is significantly lower than that of water, in which case output elements 11 are required. All of the basic elements of all embodiments are commercially available and, due to their design, exhibit good acoustic and optical reflection properties underwater, so that they can be advantageously used for acoustic and optical camouflage of the rudder 04. All of the elements shown also serve well to haptically distract the orcas from the rudder 04. Fig. 2 shows the rope 12 with the fenders 15 in a top view. It can be clearly seen that the entire stern 22 of the boat 05 is surrounded by the hanging curtain 07. The rudder 04 is thus protected axially all around towards the water, since, due to the design, the rudder 04 is protected by the hull 23 towards the bow 43 of the boat 05 (see also Fig. 1).This prevents the orcas from hearing or seeing the rudder 04 from any direction, reducing the risk of damage by the orcas. Also visible are the floating lines 18 and 19, which are attached to the boat 05 via shackles 21.

[0066] Fig. 3 shows the arrangement 01 in the embodiment in which a rising curtain 27 with a bubble curtain 26 is created as rudder protection 03. Once again, the underwater element 02 to be protected is a rudder 04 (in the form of the rudder blade, rudder system, rudder rods) of a boat 05. Here, too, protection is to be guaranteed, in particular against damage by orcas. It can be seen that the rising curtain 27 surrounds the entire stern 22 of the boat 05 and has a height of, for example, 1.3 m, so that the rudder 04 is acoustically reliably masked. In the embodiment shown, the rising curtain 27 comprises an air hose 28 which is arranged in the water below the rudder 04. The material of the air hose 28 is so strong that it remains aligned as horizontally as possible below the boat 05 and does not kink or sink.If necessary, the air hose 28 can be stabilized by another element or supported on both sides. The air hose 28 is connected to a compressed air supply 31 via two largely vertically aligned air supply pipes 29 and corresponding connecting hoses 30. This regulates the air supply to the air hose 28. The provision of two air supply pipes 29 at both ends of the air hose 28 supports its as horizontal arrangement as possible in the body of water. The air supply pipes 29 are fastened to a pushpit 33 of the boat 05 via the fastening device 17, in the illustrated embodiment each a toggle screw 32. The depth position of the air hose 28 in the water is adjusted by clamping the two air supply pipes 29 in the toggle screws 32. The predetermined breaking element 20 is provided in the area of ​​the fastening device 17.Each of these is a gripping cleat 34, from which the air supply pipes 29 are torn out if excessive force is applied. To retrieve the deployed assembly 01, two hauling lines 35 are provided on the side of the boat 05, which are attached to the air supply pipes 29.

[0067] Fig. 4 shows a top view of the arrangement 01 with the rudder protection 03 in the form of a rising curtain 27. The curvature of the air hose 28 is visible, so that the rising curtain 27 axially surrounds the entire stern 22 and thus the rudder 04. The air hose 28 is constructed in one piece, with the air supply pipes 29 arranged at both ends of the air hose 28. Also visible are the connecting hoses 30 and two compressed air supplies 31.

[0068] Fig. 5 shows a detailed illustration of the assembly 01 for creating the rudder protection 03 in the form of the rising curtain 27. The rigid air hose 28 and the laterally connected air supply pipe 29, from which the connecting hose 30 branches off, can be seen. The air supply pipe 29 and the air hose 28 are connected to each other at approximately a right angle, so that the air hose 28, after being lowered via the air supply pipe 29, can be aligned as horizontally as possible below the rudder 04. This process can be carried out very quickly in the event of an acute risk of damage to the rudder 04 by killer whales, particularly if the assembly 01 is already pre-positioned to the side of the boat 05 via the outhaul line 35. To ensure that the air hose 28 retains its curvature, its ends are connected to each other by a line 36. The assembly 01 can be assembled using commercially available components that can be purchased, for example, at any hardware store.In the inserted detail of the air hose 28, openings 37 arranged in a row can be seen, through which the air escapes into the water during use and forms the rising bubble curtain 26. It is understandable that the bubble curtain 26 will not remain as precise as the hanging curtain 07. Rather, the air bubbles in the water will evaporate in all directions, thereby forming a dense, acoustically and visually concealing and disguising rising curtain 27, which particularly confuses and deters orcas. The shape of the rising curtain 27 can be easily adjusted by the number, distribution, and density of the openings 37, as well as by adjusting the compressed air supply 31.

[0069] Fig. 6 schematically shows another arrangement 01 for generating the rising curtain 27. Here, an air plate 38 - similar to the wings on a wing keel - is firmly connected to the lower end of the rudder 04. The air plate 38 has the openings 37 in its edge. Additional openings are also arranged on the edge and in the surface of the air plate 38. In the area of ​​the width of the rudder 04, the air plate 38 has such dimensions that the rising air bubbles axially enclose the rudder 04 well. This results in complete camouflage (360°) of the rudder 04. In the embodiment shown, the compressed air supply 31 is via the air supply pipe 29 through the interior of the rudder 04 (through a hollow rudder stock). However, this can also be positioned outside the rudder 04.Alternative designs to the air plate 38 can be an air ring or foil- or winglet-like (stabilizing elements at the ends of aircraft wings) designed structures at the end of the rudder 04.

[0070] Fig. 7 schematically shows an alternative embodiment for generating the rising curtain 27. The rudder 04 is shown from the rear. A foil-like attachment 39 is arranged on each side. Further foil-like attachments 39 can be provided. The foil-like attachments 39 have - analogous to the embodiment according to Fig. 6 - openings 37 through which air can escape and generate the bubble curtain 26. Here, too, the air is supplied via the air supply pipe 29 from the compressed air generator 31. Once again, a rising curtain 27, which provides good acoustic and visual masking, is formed from a multitude of swirling air bubbles as rudder protection 03. The provision of foil-like attachments on rudder 04 is known, for example, from high-speed yachts, whose centerboards are designed as foils on which the boat 05 can glide over the water.The lugs serve to stabilize the boat 05 and to keep the rudder 04 in the water.

[0071] 9 and 10 show the effectiveness of the rudder protection 03 claimed by the invention in the two alternative embodiments compared to the prior art without this measure (Fig. 8). For this purpose, sonar images were taken which depict the water area at the stern 22 of a boat 05 as a plan view, analogous to how an orca would perceive it acoustically. For this purpose, a multi-beam sonar (720 kHz, 20° vertical aperture angle, 120° horizontal aperture angle) was positioned behind the stern 22 of the boat 05 using a remotely operated underwater vehicle (ROV). Fig. 8 (regarding the prior art) shows a sonar image without rudder protection 03 according to the invention. The blade of the rudder 04, the area of ​​the stern 22 of the hull 23 of the boat 05 and the water surface 14 are clearly visible. The sonar 40 is located at the bottom at the obtuse angle of the sonar image.It can be seen that rudder 04 emits a dominant echo with acoustic masking of the hull 22 behind it (bright areas in the echo of the area of ​​the stern 22 of the hull 23). This results from the highly reflective foam core base (high target strength, i.e., strong echo signal) of rudder 04 and its orientation perpendicular to the propagation direction of the sonar wave. The water surface and the flat hull 23 of boat 05, on the other hand, are detected tangentially by the sonar, resulting in weaker reflections from these areas.

[0072] Fig. 9 shows a sonar image of the arrangement from Fig. 7 with an additional hanging curtain 07. This consisted of chains 09 with links 24 made of aluminum. The hanging curtain 07 leads to a clearly visible, but moderate acoustic masking of the rudder 04 (the sonar image of the rudder becomes blurred) and an additional masking sonar echo from the hanging curtain 07 and the connecting element 10 (simple rod) of the hanging curtain 07. Fig. 10 shows a sonar image of the rising curtain 27 with bubble curtain 26. It shows very strong acoustic shielding and camouflage of the rudder 04 through masking and concealment, the position of which can only be guessed at. The air hose 28 itself is not shown because its material density (plastic) differs only very slightly from the density of the water, consequently it does not generate a clear echo signal.By adjusting the hole density and size of the openings 37 and the air pressure, the acoustic and optical camouflage by the rising curtain 27 with the bubble curtain 26 can be optimized.

[0073] 9 and 10 clearly show that both the hanging curtain 07 and the rising curtain 27 as rudder protection 03 according to the invention provide partial (hanging curtain) to complete (rising curtain) camouflage of the rudder blade 04 and thus proven acoustic concealment and masking as plausible, i.e. physically verifiable rudder protection, particularly against damage by orcas. In addition, the biosonar of the orcas is lower frequency (30 kHz - 70 kHz) than the sonar used for the detection (720 kHz), which leads to a greater blurring of the biosonar image perceived by the orcas compared to the sonar images shown here, whereby the effect of the curtains 07, 27 is further enhanced. Both curtains 07, 27 also provide good optical camouflage.While the rising curtain 27 has significantly better acoustic camouflage properties than the hanging curtain 07, it also offers good tactile rudder protection thanks to its physical design with chains 09 or cords 41. It is up to the user and their specific application (particularly against which male animals they need to protect their rudder) to decide which of the designs to choose. Reference symbols list.

[0074] 01 Arrangement

[0075] 02 underwater element to be protected

[0076] 03 Rudder protection (as 44)

[0077] 04 Rudder (rudder blade, rudder system, rudder rods, as 02)

[0078] 05 Boat

[0079] 06 Curtain

[0080] 07 hanging curtain (as 03)

[0081] 08 Body

[0082] 09 Chain

[0083] 10 Connecting element

[0084] 11 Output element

[0085] 12 dew

[0086] 13 Buoyancy element

[0087] 14 Water surface

[0088] 15 fenders

[0089] 16 weight (as 11 )

[0090] 17 Fastening device

[0091] 18 short swimming line

[0092] 19 long swimming line

[0093] 20 predetermined breaking element

[0094] 21 shackles

[0095] 22 rear (of 05)

[0096] 23 hull (of 05)

[0097] 24 members (of 09)

[0098] 25 rings (as 24)

[0099] 26 bubble curtains (at 27)

[0100] 27 rising curtain (as 03)

[0101] 28 Air hose

[0102] 29 Air supply pipe

[0103] 30 Connection hose 1 Compressed air supply 2 Toggle screw 3 Pushpit 4 Grab cleat 5 Outhaul line 6 Line 7 Opening 8 Air plate (on 04) 9 Foil-like attachment (on 04) 0 Sonar 1 Line 2 Bead (as 24) 3 Bow (from 05) 4 Camouflage element

[0104] R radial direction

[0105] A axial direction

Claims

Patent claims 1. Arrangement (01) for at least acoustic camouflage of an underwater element (02) to be protected against human animals emitting biosonar signals by providing a camouflage element (44) with a characteristic acoustic impedance different from water, which surrounds the underwater element (02) to be protected and generates acoustic reflections of the biosonar signals, characterized in that the camouflage element (44) is designed as a rudder guard (03) in the form of a flexible curtain (06), by which the underwater element (02) to be protected, which is designed as a rudder (04) of a boat (05), can be completely or partially surrounded axially (A) while forming a radial distance (R), wherein the characteristic acoustic impedance of the rudder guard (3) is characterized by a sound reflection factor r as a measure of the strength of the reflection of the biosonar signals at the rudder guard (03), which has a value equal to or greater than 0.

5.

2. Arrangement (01) according to claim 1, characterized in that the value of the sound reflection factor r is equal to or greater than 0.

75.

3. Arrangement (01) according to claim 1 or 2, characterized in that the rudder protection (03) is designed as a hanging curtain (07) made up of a plurality of bodies (08) arranged next to one another or as a rising curtain (27) with a plurality of rising air bubbles (26).

4. Arrangement (01) according to claim 3, characterized in that the hanging curtain (07) consists of a plurality of juxtaposed chains (09) with vertically interconnected links (24) or of a plurality of juxtaposed cords (41).

5. Arrangement (01) according to claim 4, characterized in that the members (24) are formed from rings (25), beads (42) or balls.

6. Arrangement (01) according to claim 4 or 5, characterized in that the chains (09) or cords (41) have output elements (11).

7. Arrangement (01) according to one of claims 4 to 6, characterized in that all chains (09) or cords (41) are attached at a distance from one another to a connecting element (10) which can be arranged in the water above the rudder (04) of the boat (05), the chains (09) or cords (41) having a length such that, in the arranged state, they project downwards beyond the rudder (04) of the boat (05).

8. Arrangement (01) according to claim 7, characterized in that the connecting element (10) has buoyancy elements (13).

9. Arrangement (01) according to claim 7 or 8, characterized in that the connecting element (10) is foldable and / or made up of several parts.

10. Arrangement (01) according to claim 3, characterized in that the rudder protection (03) in the form of the rising curtain (27) comprises an air hose (28) having a plurality of openings (37), which is connected to a compressed air supply (31) and can be arranged largely horizontally below the rudder (04) of a boat (05), wherein the size, number and density of the openings (37) and the compressed air supply (31) are variable.

11. Arrangement (01) according to claim 10, characterized in that the air hose (28) is connected to one or more air supply pipes (29) which can be arranged largely vertically and / or is bent.

12. Arrangement (01) according to one of claims 1 to 11, characterized in that the rudder protection (03) comprises a fastening device (17, 19) with a predetermined breaking element (20).

13. Arrangement (01) according to one of claims 3 to 12, characterized in that the rudder protection (03) in the form of the rising curtain (27) comprises an air outlet device (08) which can be permanently integrated into the rudder (04) of the boat (05) and which is connected directly or via the rudder (04) to a compressed air supply (31).

14. Arrangement (01) according to claim 13, characterized in that the air outlet device (08) comprises an air plate (38) having openings (37) which can be permanently arranged at a lower end of the rudder (04) of the boat (05).

15. Arrangement (01) according to one of claims 1 to 14, characterized in that the rudder protection (03) additionally has optical reflection properties.

16. Application of the arrangement (01) according to one of claims 3 to 15, characterized in that the rudder protection (03) is used in the form of the hanging curtain (07) for a stationary boat (05) or in the form of the rising curtain (27) for a stationary or a moving boat (05).

17. Application of the arrangement (01) according to claim 16, characterized in that damage to the rudder (04) of the boat (05) by orcas as marine animals is to be avoided.

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