Swing Keel for Multi-Hull Boats to Enhance Steering and Docking Maneuverability

Abstract

A swing keel system for multi-hull boats, including but not limited to pontoons, tritoons, and multi-hull houseboats, is disclosed. The keel is pivotally mounted and can be deployed during docking to improve maneuverability and retracted when not in use. It enhances steering by limiting lateral movement and acting as a turning fulcrum, reducing turn radius and improving tracking in crosswinds. The keel swings forward or backward upon impact with obstacles to minimize damage. Deployment may be manual or powered via a winch, motor, or hydraulic system. The keel may be constructed from marine-grade aluminum, fiberglass-reinforced composites, or carbon fiber for strength and durability. A weighted distal end aids gravitational deployment, while a bolt sleeve reduces friction and enhances operation. This system allows for retrofitting onto existing vessels without hull modifications and may also be incorporated into new boat construction.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to marine steering and stability systems, specifically to a swing keel mechanism for multi-hull boats, including but not limited to pontoons, tritoons, and multi-hull houseboats. The invention enhances maneuverability and tracking by providing a deployable keel that limits lateral movement and reduces the turning radius during docking or low-speed operation. The design allows the keel to retract when not in use and pivot upon impact to minimize damage.BACKGROUND OF THE INVENTION

[0002] Boats with multiple hulls, such as pontoons and tritoons, are widely used for recreational and commercial purposes due to their stability and spacious decks. However, these vessels often lack precise maneuverability, especially at low speeds and during docking. Unlike monohull boats, which rely on a single hull and deeper keel, multi-hull boats have a shallow draft and tend to drift laterally when turning, making close-quarters handling challenging.

[0003] Retractable swing keels are a well-known feature on sailing monohulls, particularly in the 20-to-25-foot range, and some sailing catamarans. These keels are integrated into the hull during construction and recede into a dedicated chamber when retracted. Their primary function is to improve upwind sailing performance by increasing lateral resistance in the water. In monohulls, swing keels are often weighted to act as ballast, reducing heel and improving stability under sail. While monohull sailboats do experience enhanced docking agility when their swing keels are deployed, this benefit is secondary to their primary sailing function.

[0004] Unlike these built-in swing keels for sailboats, the present invention is an add-on swing keel system designed to be mounted between the hulls on the underside of the deck of multi-hull boats, including but not limited to pontoon, triton, and multi-hull houseboats. This invention improves low-speed maneuverability and docking by creating a turning fulcrum that reduces turn radius and limits lateral drift. Additionally, the keel is designed to retract when not needed and to pivot upon impact with underwater obstacles, preventing damage. The design allows for retrofitting onto existing boats without modifying the hull structure while also offering an integrated steering enhancement option for manufacturers.

[0005] Traditional swing keels require extensive structural integration. In contrast, this invention provides a straightforward retrofit solution, reducing installation costs and expanding accessibility. For example, the Catalina 22 sailboat is one of the most popular trailerable sailboats ever produced. This well-known sailboat incorporates a cast-iron swing keel weighting approximately 500 pounds designed primarily as ballast and for upwind sailing in a monohull. In contrast, the present invention is significantly lighter and intended specifically for powerboats to enhance maneuverability rather than stability. Unlike the Catalina 22's integrated design, this invention can be retrofitted onto existing vessels without hull modifications.

[0006] Swing keels have historically been used in monohull sailing vessels as fundamental design components rather than as optional retrofits for powerboats. The present invention is uniquely designed for power-driven multi-hull vessels, including but not limited to pontoons, tritoons, and multi-hull houseboats, to improve low-speed maneuverability and docking. This application is non-obvious because traditional swing keels focus on upwind sailing performance and stability, whereas this present invention utilizes a minimally weighted design, with weight serving only to assist in deploying the keel rather than providing ballast, without excessively increasing drag or the weight of the boat. The novel combination of these design elements, along with multiple deployment mechanisms tailored for powerboats, demonstrates a significant advancement over prior art.SUMMARY OF THE INVENTION

[0007] The invention is a swing keel system installed on multi-hull boats. The system employs a bolt or similar axis as the pivot point for the swing keel. The axis is securely attached to the mounting assembly, which is affixed to the underside of the deck and between the hulls of a multi-hull boat.

[0008] A manual control line or automated mechanism, including but not limited to an electric motor or hydraulic system, allows the keel to be lowered into the water during docking operations and raised completely out of the water when not required. This system ensures the keel does not impede the boat's performance during high-speed operation or shallow-water navigation. Additionally, the design allows the keel to swing forward or backward upon contacting an underwater obstruction, thereby absorbing and dispersing impact forces and minimizing damage to the keel and the vessel.

[0009] The swing keel improves steering and maneuverability during docking by reducing lateral movement of the vessel during turns, effectively acting as a turning fulcrum. During a starboard turn, the keel's resistance causes the bow of the vessel to move to starboard and the stern to move to port. Conversely, during a port turn, the bow moves to port, and the stern moves to starboard. This results in a smaller turning radius and quicker completion of turns, critical for precise docking maneuvers. When the helm is set to a straight-ahead position, the keel helps maintain a straight course by reducing lateral drift when encountering a crosswind or following a 90-degree turn. This characteristic is particularly beneficial when maneuvering in tight spaces, such as marinas, or when entering a boat slip.

[0010] The keel and mounting assembly are constructed of any lightweight, durable material able to withstand corrosion, including but not limited to marine-grade aluminum, fiberglass-reinforced composites, and carbon fiber-reinforced composites. These materials ensure longevity and resistance to corrosion and impact. The distal end of the keel farthest from the mounting assembly may be weighted with lead or a similar material to assist in gravitational deployment, allowing the keel to lower smoothly when released. The pivot axis (bolt) is made of stainless steel or other corrosion-resistant alloys to maintain strength and reliability in a marine environment. The pivot axis bolt passes through a bolt sleeve to reduce friction during raising and lowering of the keel and to prevent the keel from contacting the pivot bolt. This design improves durability and extends the lifespan of the system.

[0011] This invention differs from prior swing keel designs by incorporating a modular retrofit system, enabling installation on pre-existing hulls with minimal alterations. Unlike prior swing keel designs, such as the Catalina 22 sailboat's cast-iron swing keel, which serves primarily as ballast for sailing performance, the present invention is constructed from lighter materials and does not require hull modifications. This novel design enhances maneuverability for powerboats, providing docking agility and improved tracking without adding excessive weight.BRIEF DESCRIPTION OF THE DRAWINGS:

[0012] FIG. 1: Perspective view of the swing keel system in the lowered position, showing the keel and mounting assembly.

[0013] FIG. 2: Side view of the swing keel system in the raised position, illustrating the keel and mounting assembly.

[0014] FIG. 3: Bottom view of the mounting assembly in the raised keel position, highlighting additional structural elements for stability.

[0015] FIG. 4: Alternative view of the keel incorporating a weight at its distal end, showing the bolt sleeve.

[0016] FIG. 5: Front view of a pontoon boat with the swing keel, showing the boat floor, pontoon tubes, and water level.

[0017] FIG. 6: Front view of a tritoon boat illustrating three pontoon tubes and the placement of the swing keels between them.

[0018] FIG. 7: Side view of a pontoon boat with the swing keel, showing its mounting between the pontoon tubes beneath the boat floor.

[0019] FIG. 8: Method of raising and lowering the keel using a control line and blocks to guide the line to the captain's chair.

[0020] FIG. 9: Hydraulic system for raising and lowering the keel, including hydraulic cylinder and control mechanism.

[0021] FIG. 10: Electric motor system for raising and lowering the keel, showing the motor and user control.DETAILED DESCRIPTION OF THE DRAWINGS

[0022] The following detailed description provides examples of presently contemplated modes of implementing embodiments of the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating general principles of embodiments of the invention.

[0023] FIG. 1 illustrates a perspective view of the swing keel system in its assembled state in the lowered position. The keel (10) is pivotally attached to the mounting assembly, which consists of a base (11), two mounting assembly sides (12, 13), and structural reinforcement elements (two of which are visible as elements 14 and 15). The base (11) includes holes (11a) for securing the assembly to the underside of a multi-hull boat with fasteners including but not limited to screws, bolts, or brackets. The keel (10) rotates around a pivot bolt (20), allowing it to be raised or lowered as needed. The keel (10) is designed to minimize hydrodynamic drag while providing sufficient lateral resistance when deployed. The distal end of the keel (10), opposite the pivot bolt (20), may include a weight (30) as shown in FIG. 4 to assist in deployment.

[0024] FIG. 2 provides a side view of the swing keel system in the raised position, showing the relationship between the keel (10), the mounting assembly base (11), and the mounting assembly side (12). The pivot bolt (20) is positioned near the upper portion of the keel (10), enabling smooth rotation. The structural reinforcement elements (14, 15) are visible, adding rigidity to the mounting assembly. Although not visible in this figure, a bolt sleeve (21), as shown in FIG. 4, may be fitted around the pivot bolt (20) to reduce friction during deployment and retraction and to prevent direct contact between the keel (10) and pivot bolt (20), thereby improving durability.

[0025] FIG. 3 presents a bottom view of the mounting assembly in the raised keel position, showing additional structural elements (14, 15, 16, 17) that provide increased stability and durability. The mounting assembly base (11) features multiple bolt holes (11a) for secure attachment to the boat. The mounting assembly sides (12, 13) extend upward to house the pivot bolt (20), ensuring the keel (10) remains properly aligned during operation.

[0026] FIG. 4 illustrates an alternative view of the keel (10) incorporating a weight (30) positioned at the distal end of the keel, opposite the pivot bolt (20). This weight (30) may be composed of lead or a similar high-density material to improve stability and ensure the keel (10) remains in the deployed position. In embodiments where the keel (10) is constructed from wood, the weight (30) may be recessed into the structure of the keel and encapsulated with fiberglass or another protective covering to ensure durability and resistance to water intrusion. The weight (30) serves multiple functional benefits, including assisting in lowering the keel (10) through gravitational force and counteracting hydrodynamic forces that might otherwise cause the keel to rise when the boat is moving. This is particularly beneficial for keels constructed of wood, which may have natural buoyancy. By incorporating the weight (30), the keel (10) is more effectively maintained in its intended vertical position. Unlike conventional swing keels that require significant ballast, the present design utilizes only a minimal amount of weight necessary to facilitate lowering without affecting the vessel's performance. The majority of the keel (10) features a streamlined shape to minimize hydrodynamic drag and optimize performance in water. However, the portion of the keel (10) that fits between the mounting assembly sides (12, 13) is rectangular to ensure proper alignment during operation, preventing unintended lateral movement. A bolt sleeve (21) reduces friction and prevents direct contact between the keel (10) and pivot bolt, enhancing durability and smooth operation.

[0027] FIG. 5 illustrates a front view of a pontoon boat equipped with the swing keel (10). The boat floor (40) is shown above the pontoon tubes (41), which provide buoyancy and stability. The mounting assembly (11, 12, 15) secures the swing keel (10) beneath the boat, allowing for controlled deployment and retraction. The water level (42) is indicated to show the keel's position relative to the boat's flotation line.

[0028] The swing keel system is designed for straightforward installation on multi-hull vessels. The mounting assembly (11, 12, 13) is secured to the underside of the deck (40) between the pontoon tubes (41) using marine-grade fasteners including but not limited to stainless steel bolts, screws, or corrosion-resistant brackets. Alignment is crucial to ensure that the keel (10) remains properly centered for optimal performance. To facilitate this, templates or pre-drilled mounting points may be provided. For newly manufactured vessels, the system can be integrated into the deck structure during construction, ensuring a seamless fit and enhanced durability.

[0029] FIG. 6 presents a front view of a tritoon boat with the swing keel (10). Similar to FIG. 5, the boat floor (40) is positioned above three pontoon tubes (41), with two swing keels (10) mounted between the three pontoon tubes beneath the boat floor. The mounting assembly (11, 12, 15) is affixed to the boat's structure, ensuring stable attachment. The water level (42) is again represented to show how the keel interacts with the water during operation.

[0030] FIG. 7 provides a side view of a pontoon boat featuring the swing keel (10). The keel (10) is mounted beneath the boat floor (40) and between the pontoon tubes (41), ensuring it is positioned centrally for optimal steering assistance. The mounting assembly (11, 12, 14, 15) secures the keel (10) in place, allowing it to pivot as necessary. The keel (10) enhances steering by reducing lateral movement and acting as a turning fulcrum. During a starboard turn, the keel's resistance causes the bow of the vessel to move to starboard while the stern moves to port. Conversely, during a port turn, the bow moves to port, and the stern moves to starboard. This results in a smaller turning radius and quicker completion of turns, critical for precise docking maneuvers.

[0031] FIG. 8 illustrates a method of raising and lowering the swing keel (10) using a control line (50). The control line (50) is attached to the keel (10) at an attachment point (51), which may be an eye bolt or a similar connector. The line is routed through one or more blocks (52) that direct it within reach of the captain's chair (43), facilitating manual adjustment of the keel's position. This allows the operator to quickly deploy or retract the keel (10) as needed for docking or maneuvering. The boat floor (40) and supporting structure are shown to provide context for the mounting arrangement. Control lines (50) should be composed of high-strength, synthetic rope, such as nylon.

[0032] FIG. 9 depicts an alternative method for raising and lowering the swing keel (10) using a hydraulic system. A hydraulic cylinder (56) is connected to the keel (10), allowing for controlled movement based on user input. A control mechanism (55), which may take the form of a switch, button, or remote, is used to actuate the hydraulic system, providing an efficient and effortless means of adjusting the keel's position. The system may be configured with a pressure relief valve to absorb sudden impacts from underwater obstacles. The boat floor (40) and surrounding structural components are included for reference.

[0033] FIG. 10 illustrates another alternative method for adjusting the swing keel (10), this time using an electric motor (57). The motor (57) is connected to the keel (10) and controlled via a user-operated interface (55), which may include a switch, button, or remote. The mounting assembly (11, 12, 14, 15) ensures the keel (10) remains securely positioned while allowing for powered adjustments. The boat floor (40) is again shown to provide spatial context for the installation.

[0034] Hydraulic (56) and electric (57) components are sealed against moisture ingress to ensure reliable operation in marine environments. Routine maintenance ensures the longevity and proper function of the swing keel system. Key maintenance tasks include periodic inspection of the pivot bolt (20) and sleeve bolt (21) for signs of wear or corrosion, especially in saltwater environments. Lubrication of moving parts with marine-grade grease reduces friction and extends component life. The control mechanisms—whether mechanical (50), hydraulic (56), or electric (57)—should be checked regularly for proper operation. If the system is equipped with a control line (50), operators should inspect it for fraying or weakening over time. In the event of impact with underwater obstacles, users should verify that the keel (10) pivots freely and that no structural damage has occurred to the mounting assembly.

[0035] The dimensions, materials, and specific configurations described herein are exemplary and may be modified to optimize performance or suit particular applications without departing from the scope of the invention. Various modifications, additions, and alternative embodiments may be employed, including different combinations of features and implementations that do not include all described features. The present invention is intended to encompass all such alternatives, modifications, and variations that fall within the scope of the appended claims and their equivalents.

Claims

1. A swing keel system for multi-hull boats, comprising:a. A keel pivotally mounted to the underside of the boat via a pivot bolt and bracket assembly, allowing for controlled deployment and retraction; andb. A deployment mechanism for lowering and raising the keel, which may include a manually operated control line routed through guide blocks, a winch system, an electric motor with a geared mechanism, or a hydraulic actuator, enabling precise positioning; andc. The keel being weighted at its distal end to assist with deployment; andd. The keel configured to reduce lateral drift and enhance maneuverability during low-speed operation, particularly docking and close-quarters handling.

2. The swing keel system of claim 1, wherein the keel improves steering by acting as a turning fulcrum, reducing turn radius and enhancing maneuverability.

3. The swing keel system of claim 1, wherein the keel maintains a straight course by limiting lateral drift when the helm is in a straight-ahead position, including in crosswind conditions.

4. The swing keel system of claim 1, wherein the keel and pivot axis are constructed from marine-grade aluminum, fiberglass-reinforced composites, carbon fiber-reinforced composites, or another corrosion-resistant material capable of withstanding hydrodynamic forces.

5. The swing keel system of claim 1, wherein the system is retrofit-capable and designed for installation onto existing multi-hull vessels without requiring modifications to the hull structure, utilizing mounting brackets or other fastening means that attach to the boat's existing framework.

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