Patent Application
20240251769
This invention relates to the retrieval of items in a water body, and in particular devices and methods for retrieving fishing gear and other equipment fixed on the floor of a water body.
Many objects need to be retrieved from bodies of water. For example, many commercial fishing industries target bottom dwelling creatures, such as lobsters and other crustaceans. Often, weighted box-shaped traps, which are usually connected in series, are attached to a groundline, which is connected by another long rope, which is commonly made of a synthetic or natural material, that is in turn shackled or tied to a floatation buoy at the surface. Fishing crews on a boat access the buoy to access the line and retrieve the traps.
This method of retrieval is effective, both in terms of cost and practicalities, but has faced increasing scrutiny and limitations due to the ability of these retrieval lines to entangle marine animals, especially the North Atlantic Right Whale.
Efforts to reconcile the economic importance of pot fisheries with the survival of endangered whale species have led to the development and promotion of several novel ropeless gear inventions, which generally rely on lobster traps connected to remotely activated tethered floats restrained at the sea bottom that when triggered expand or are released causing rapid ascend to the surface. Activation is triggered via electronic or acoustic signals. Once at the surface, the buoy is retrieved and the attached line is hauled bringing the seafloor based gear with it to the surface.
Commonalities across ropeless fishing gears include use of electronics and space-based navigation services. The reliability and economics of ropeless fishing gear is a subject of investigation, though initial studies suggest incompatibility with small lobstering operations. Additionally, the incorporation of “breakaway links” has been promoted by regulators. These chain-shaped links are designed to break at a tensile load theoretically calibrated to promote release of an animal during an entanglement event. There are also concerns from lobster harvesters about the reliability of these links in storms or otherwise rough seas, as well as false breakages resulting from boat entanglement or tensile forces on heavily loaded retrieval lines, which may have more than 40 traps attached at once.
What is needed, therefore, is a device and method of trap retrieval that limits bycatch and entanglement that is cost-effective and reliable.
The invention is a semi-rigid retrieval line made from fiber reinforced plastic generally comprised of stiff fibers and related method of trap retrieval. The stiff fibers may take a number of forms, such as, for example, glass, aramid, and/or carbon, and which may be non-uniformly distributed to achieve the desired combination of tensile and bending strength, and a binding resin. The resulting semi-rigid retrieval line, a “composite line”, features bending stiffnesses much higher than fiber ropes, an inability to form knots, and failure in bending within a specified curvature.
The composite line may be vertically oriented and attached to a surface buoy and long enough to nearly reach the seafloor, i.e. the composite line ideally terminating at least 2 meters above the seafloor to prevent abrasion with seafloor sediments. The composite vertical line has a termination fitted on either end. A synthetic fiber ground line may be attached at the bottom end, to which standard fishing traps are attached. To maintain floatation and visibility from the surface, standard buoys may be used.
The method of trap retrieval includes the utilization of a number of accessories needed for bringing the loaded traps aboard a boat. In general, a mechanically actuated winch with a large diameter drum allows for controlled coiling and uncoiling of the composite line. This winch is fitted with an outer cage surrounding the drum that restricts unwanted uncoiling of lines when tension on the coiled line is released. To mitigate the likelihood of bending stresses that may trigger mechanical failure during hauling and deployment, a variety of fairlead systems may be utilized to handle the line between the water and mechanical winch system. To ensure a clean fracture in the event of a marine mammal interaction, a series of specially engineered rigid disks may be attached to the composite line.
The present invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. The drawings are not drawn to scale.
The present invention will now be described more fully in detail with reference to the accompanying drawings, in which the preferred embodiments of the invention are shown. This invention should not, however, be construed as limited to the embodiments set forth herein; rather, they are provided so that this disclosure will be complete and will fully convey the scope of the invention to those skilled in the art.
The semi-rigid line 100 is made of composite material, e.g. fiber-reinforced plastic, and may be any suitable length needed to operate in water of any depth. The composite material itself may be manufactured via pultrusion or extrusion methods, and delivered to the end-user in a long-length coil.
The specific construction of the line 100 may vary slightly depending on particular needs. For dimensional and structural stability during storage while coiled, a Coefficient of Thermal Expansion (CTE) less than or equal to 6.0E-6/° C., alternatively identified as 6.0×10{circumflex over ( )}−6/° C. or 6.0 μm/m/° C. where ° C. represents degrees Celsius, is desired. The polymer is chosen to have minimal degradation of mechanical properties with prolonged submergence in fresh, brackish, or salt water. Low surface roughness also aids resistance to snagging or knotting, with an average roughness (Ra) of 1.0±0.25 micrometers, as well as lowering friction and abrasion during contact with handling machinery and/or sea creatures. The flexural modulus is sufficiently low, likely less than 42 Newton meter squared (N-m2) for handling and coiling, with an approximately 1.5 meter safe coil diameter, yet substantially stiffer, likely greater than 8 N-m2, than traditional lines to reduce entanglement risks. The semi rigid line is designed such that it can be manually coiled at 1.5 m diameter safely, and such that bending stresses at this diameter will be significantly lower than those that would cause failure.
The line 100 has a high tensile load capacity, likely greater than 60 kiloNewtons (kN), to support dynamic loads in excess of 40 kN during hauling operations and normal deployment conditions. Depending specifically on the handling characteristics and the required bending stiffness, several options for composite construction exist. For higher stiffness requirements, i.e. having flexural modulus ˜42 N-m2, commercially available pultruded fiberglass (GFRP) rods may be suitable, such as those used as rebar in concrete construction like “TUF-BAR 60 GPa Straight Bar”.
On the other hand, for situations where lower bending stiffness, i.e. those having flexural modulus ˜8-10 N-m2, is preferred, a more complex composite rod may be utilized. For example, the composite may have an aramid-vinylester core, and pure vinylester exterior coating. This construction meets the tensile load requirements, while being approximately 35% of the linear mass of the comparable GFRP option. Its minimum bending radius is also considerably lower at 0.1 m which must also be matched to the typical fishing operations in which it is employed and the associated entanglement risks and desired behavior. This construction may be achieved in a two-step pultrusion process, with the aramid core being constructed initially and cured, followed by a thinner application of the neat resin to both protect the aramid fibers from the environment, and reduce the global bending stiffness compared to GFRP for easier handling, while still being appreciably stiffer than traditional ropes and lines.
Upon receipt by the end-user, the composite line 100 may be uncoiled and cut to length, and end termination fittings fitted and/or attached. A variety of terminations are available depending on end-user preference, such as but not limited to custom composite threaded end connections, bonded custom composite end fittings, and traditional metallic cable fittings.
Threaded terminations require custom shouldering fittings to address stress concentrations in tensile and bending loads between the threaded portion of the composite line and the remainder of the line, with the local load transfer between the threads of the joint in compression to the shouldering fitting transferring tensile and bending loads between the line and hardware attached to the termination. Additional features are incorporated to ensure that the threaded joint will not come undone under cyclical light loadings expected during normal deployed conditions, such as locations for lock-wire to be installed. Bonded terminations feature a female socket that forms a clearance fitting over the cut end of the composite rod. After abrading and cleaning both surfaces adequately, a suitable thixotropic adhesive can be used to permanently bond the two components together.
The custom terminations are designed for easy field installation, and utilize material properties as well as geometric features to reduce the likelihood of a creation of a stress concentration at the joint between the composite rod and end fitting. “Traditional” terminations such as crimped fittings and spelter sockets are also suitable but must be evaluated for mechanical compatibility with the composite material being used. The finished connecting line may be coiled and attached to the rest of the trap line assembly. The assembled line and its terminations are compatible with standard crustacean traps and their attachment methods. The trap is deployed in its usual manner, and the line is fully submerged when in use.
Another key component of the invention is the redesigned vessel components that enable fishers to work with the composite lines with minimal interference to typical operations. These primary vessel components are a revised larger diameter, e.g. 1.5 m, winch system that can accommodate reeling the composite line aboard, and a radiused fairlead to redirect the line being hauled, whether composite or traditional, towards the winch without creating stress concentrations.
The fairlead assembly is primarily intended to be a retrofitted fixture onto existing vessels, allowing the large diameter winch to pull the composite line, which is appreciably stiffer in bending than traditional ropes used today, and traps aboard. Where existing trap haulers pull the trawl line directly aboard and the traps hang before being manually pulled aboard and disconnected, the newly designed fairlead also positions the traps for disconnection without manual lifting while also supporting them for more controlled handling. The fairlead's radius of curvature, e.g. 0.75 m, is tuned to produce low bending stresses, i.e. to prevent unintentional failure in the composite line, while also providing enough space to accommodate all traditional trap gear. Alternatively, a system of large diameter, e.g. approximately 1.5 m, rollers placed at the deck edge of the vessel could be used to further alleviate wear on the composite lines.
A roller with a horizontal axis of rotation is inset in the vessel deck while rollers with vertical axes of rotation are fixed on either side of an opening in the vessel topsides at deck level. The opening formed by the rollers is large enough to allow entry of the traps. Made from a high strength, wear resistant and low friction plastic material such as HMPE or Polyoxymethylene, such as Delrin, the rollers or fixed fairlead is resistant to corrosion and prevent wear on the composite line material. The fairlead system can be positioned and oriented either for stern or side-hauling as needed. In cases where the fairlead system is positioned for side-hauling and extends outboard, it is either easily repositionable so as to reduce risk of wave impact during vessel transit, such as in the case of a fixed fairlead as 350 shown in
The mechanized winch, which may be electrically and/or hydraulically powered depending on the fishing vessels' systems, has several key features: 1) a large drum diameter (approximately 1.5 m) to reduce the bending stresses imparted on the composite line, 2) features to allow banding of the coiled bundle to restrict the composite line from uncontrolled uncoiling including axially oriented slots in the drum surface, 3) an open or removable end to allow the coiled and banded bundle to be removed or inserted, 4) a fixed framework surrounding the rotating drum which contains the coil once bundling bands have been released and before tension has been applied during deployment, 5) an actuated level wind mechanism which controls the lay of the composite line on the drum, thereby preventing cross-over or self tangling of the composite line during deployment and 6) an integral tether and initial guidance system that allows for the fisher to attach the captured fishing line to the winch, and ensure the buoy and near-surface gear remains accessible.
The level wind mechanism's rotation is tied into the rotation of the drum via internal gearing, and transits the drum's axial direction. The level wind guide bars can be raised as needed to disengage from the composite line, thus allowing easier removal and installation of the coiled and bundled line. This tether keeps the composite line in tension during coiling or uncoiling, thereby preventing the coil from springing open and disrupting the orderly unspooling or coiling of the line during deployment or recovery.
As noted, a primary design criterion for the composite line is the failure during potential marine mammal entanglement events. However, testing and data to support this behavior in all interaction events is not easily achieved given the multitude of potential interaction types. To better control for desirable breaking performance during an interaction, mechanisms can be added to semi-rigid lines or traditional synthetic fiber ropes during deployment. When pressed against a whale body in an entanglement event, a breakaway disk, shown in
These breakaway disks would be automatically attached and removed as the line is deployed or recovered. Mechanisms for doing so could be integrated with the specialized fairleads described above. To maintain an orientation perpendicular to the axis of the line, flexible bracing material, such as high density neoprene, would surround the rigid plastic disk, made from HDPE or PVC, in a toroidal shape with a triangular cross section such that the edge pressing against the line is wider than the edge connected to the outer edge of the rigid disk. The entire disk and bracing wedge could be hinged or slotted such that the line can be seated within the hole in the center of the device. Once seated, the device would be clamped shut. These disks would be positioned approximately every 3 m along the length of the line, ensuring that if a large marine mammal were to interact with any part of the line, at least one of these devices would be engaged. The performance of these devices will be a function of the tension applied on the line passing through the device, the curvature of the engaged animal body, and the diameter of the rigid disk. The diameter can be chosen to best suit the morphology of the animals of interest; but will typically range from 0.25 to 0.5 m. The rigidity of the flexible bracing material can be adjusted to best suit the anticipated tensile force and line curvature characteristic of an entanglement event with the animal of interest.
The termination 200 shown in
It is understood that the embodiments described herein are merely illustrative of the present invention. Variations in the construction of the semi-rigid line and apparatus may be contemplated by one skilled in the art without limiting the intended scope of the invention herein disclosed and as defined by the following claims.
| Number | Date | Country | |
|---|---|---|---|
| 63482101 | Jan 2023 | US |
