GB2618343A

GB2618343A - Buoyant Stern Structure

Info

Publication number: GB2618343A
Application number: GB2206463.8A
Authority: GB
Inventors: Mathieson Mark
Original assignee: Mathwall Engineering Ltd
Current assignee: Mathwall Engineering Ltd
Priority date: 2022-05-03
Filing date: 2022-05-03
Publication date: 2023-11-08
Also published as: GB202207793D0; GB2619608A; GB202206463D0; GB202306559D0

Abstract

A boat 100 has a hull 101 comprising a stern 102 and a sealable powertrain container 103 housing a drive mechanism 104 for driving the boat. The sealable powertrain container is located at the stern of the boat and is mounted relative to the hull so as to increase the buoyancy of the boat when the boat is under way. The sealable powertrain container may comprise an opening for providing access to an interior of the container and a closure 105 movable to close the opening in a watertight manner. The application also discloses a boat having a transom (401, Fig 4) and a base, with a rigid brace (402, Fig 4) attached between the stern and the base of the hull, for reinforcing the structure of the boat and a hollow pole (405, Fig 4) comprising an upper end and an opening coupled to an internal combustion engine to serve as an inlet.

Description

Buoyant Stern Structure This invention relates to a sealable powertrain container for a boat, mounted to increase the buoyancy of the boat.

There are two broad categories that describe powertrain placement in marine vessels: inboard and outboard. Inboard motors are mounted inside a boat, typically in the hull. They may be above a deck or hidden below a deck. The placement of an inboard motor affects the weight distribution and consequently the boat's pitch and steerage behaviour when the boat is afloat. Outboard motors are placed outside of a boat, usually at the rear of the craft. Positioning a motor at the rear of a boat can increase power control and steering, as well as pushing down the stern and raising the bow. However, this additional weight at the stern can drag the back of the boat down so at low speeds the efficiency of the boat's propulsion is reduced. This is particularly an issue with four-stroke outboard engines since they tend to be relatively heavy. Stern drag is particularly problematic in regulated-speed areas such as a harbour where the lower efficiency means that relatively higher power is required for a given speed, thereby consuming a larger amount of electric power or fuel.

Inboard motors typically have a higher upfront capital cost, they are relatively expensive to install and do not allow easy access for maintenance or servicing. Existing outboard motors can obstruct rescue operations by reducing accessibility from the stern to the water, they may also impede docking and the loading / unloading of cargo from the rear of the boat to a dock or land. For the inboard installation the powertrain is usually fixedly attached, leading to issues with servicing and replacement.

The tendency of boat propulsion systems to draw water from the surface can lead to cavitation, where air as well as water pass through the propellor, reducing the efficiency of the propulsion. Outboard motors and stern drives (used with inboard installations) may have a cavitation plate positioned to travel across the surface of the water when the boat is moving to prevent cavitation.

There is a need for an improved propulsion system which can at least partially address one or more of the problems identified above.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a boat having a hull comprising a stern; and a sealable powertrain container housing a drive mechanism for driving the boat, the sealable powertrain container being located at the stern of the boat and mounted relative to the hull so as to increase the buoyancy of the boat when the boat is under way.

There is provided a sealable powertrain container comprising an opening for providing access to an interior of the container and a closure movable to close the opening in a watertight manner.

The drive mechanism may be removable from the powertrain container through the opening.

The container defines an exterior underside surface thereof, the container may be located so that there is a stepped transition from a major underside surface of the hull to the underside surface of the container.

The exterior underside surface of the powertrain container may be located at a shallower draft than the exterior underside surface of the hull at the stern thereof.

The powertrain container may carry a propellor drivingly coupled to a powertrain located in the container, the propellor being located at a greater draft than the exterior underside surface of the powertrain container.

The powertrain container may further comprise an upper surface defining a walk-on platform.

The powertrain container may comprise a deployable walk-on platform.

The deployable platform may comprise a substantially rigid surface element and at least one hinge whereby the surface element is attached to a body of the container The deployable platform may be inflatable.

The deployable platform may be telescopic.

The powertrain container may have a width equal to or less than the width of the stern of the hull of the boat The powertrain container may be removably mounted to the stern.

The boat may further comprise a mounting structure at a transom for attaching the powertrain container.

The drive mechanism may be removably attached to at least one internal surface of the container.

A boat having: a hull comprising a stern and a base; a rigid brace attached between the stern and base of the hull for reinforcing the structure of the boat; and a hollow pole comprising an upper end and an opening coupled to an internal combustion engine to serve as an inlet.

There may be provided a sealable container for enclosing a powertrain, the container located at the stern of a boat and mounted relative to a hull so as to increase the buoyancy of a boat. The container may have a hydrodynamic underside which may improve the quality of the water flow to the propellor, reduce drag and improve performance.

DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example with reference to the accompanying drawings. In the drawings: Figure 1 shows a side view of a boat with a sealable powertrain container at the stern.

Figures 2a and 2b show a cutaway section of a boat and two closures of a sealable powertrain container.

Figure 3 shows a top-down view of a boat with a sealable powertrain container and deployable platform.

Figure 4 shows a cutaway section of a boat with a transom reinforcement.

Figure 5 shows a cross section of a rigid inflatable boat.

Figure 6 shows a series hybrid layout of motors and generators within a sealable container.

Figures 7a, 7b and 7c show different configurations of drive systems within sealable containers.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art.

The general principles defined herein may be applied to other embodiments and applications without departing from the present invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

In the present specification the term "engine" is used to mean a combustion engine, which burns fuel to generate power. The term "motor" is used to mean a device that uses electrical energy to generate power. A boat may be propelled by an engine or a motor. The terms "drive mechanism" are used to mean any form of drive for a marine powertrain. A drive mechanism may comprise one or more engines and/or motors. A "powertrain" may comprise one or more of an engine, a motor and a gearbox.

Figure 1 shows a boat 100 having a hull 101 comprising a stern 102. A powertrain container 103 is provided. The powertrain container houses a drive mechanism 104 for driving the boat. The powertrain container is sealable to exclude water from entering. The powertrain container is located at the stern 102 of the boat. The powertrain container is mounted relative to the hull so as to increase the buoyancy of the boat. The sealable container 103 has an opening for permitting access to its interior. The opening can be closed and sealed by a lid 105.

The drive mechanism 104 is connected to a driveshaft 106. The driveshaft is coupled to and transmits drive to a propellor 107. The propellor is located outside the container. Moulded protrusions in the container 103 serve as securing means 108 that support the drive mechanism 104 in the container and hold it securely. The drive mechanism 104 may be removable from the container 103. The two securing means 108 shown on either side of a drive mechanism are illustrative, but the number, configuration and position of securing means varies with the particular drive mechanism and additional components in the container. An attachment for the drive mechanism 109 is shown extending from an internal surface of the container to the drive mechanism 104. The attachment for the drive mechanism 109 may penetrate the transom of the boat and be cantilevered from inside the hull.

The propellor may be mounted so that it is located below the base of the container. 25 The propellor may be located under the container or rearward of and lower than the container.

An underside 110 of the sealable powertrain container is shown stepped relative to an underside of the boat. The forward edge of the underside of the powertrain container abuts the transom. The base of the powertrain container is offset from and above the underside of the hull where the underside of the hull meets the transom. There is a portion of the transom exposed to the exterior of the boat and located vertically between the underside of the hull and the base of the powertrain container. That portion of the transom extends in a generally upright direction when the boat is in its static floating attitude. When the boat is in its static floating attitude the underside 110 of the powertrain container is shallower in the water than the deepest part of the underside of the hull where it meets the transom. When the boat is in motion, the stepped transition from the underside of the hull to the base of the container can result in laminar flow of water from the base of the hull to the region under the container and rearward thereof. The propellor can be located in that region. This can result in improved efficiency of the propellor.

Figure 2a shows a section of a boat 200 and a sealable powertrain container 201. The container has an opening through which the interior of the container can be accessed, for example for servicing equipment located in the container. The container is provided with a movable lid or cover 202. The lid is configured so that it can be fitted to the opening so as to close the opening in a watertight manner. This can seal the container so that it is watertight. The movable cover 202 may be connected to a body of the powertrain container 201, for example by hinges 203 or slidably on rails (not shown), or it may be entirely removable. The movable cover 202 acts as a lid to the container.

Equipment for propelling the boat can be located in the container. That equipment may, for example, include any one or more of: a drive mechanism such as an engine or a motor; a cooling system for a drive mechanism; an energy source for a drive mechanism, such as a fuel tank or a battery; a control system for a drive mechanism such as an engine control unit (ECU) or a motor control unit (MCU); a gearbox, which may be coupled between an output shaft of the drive mechanism and a propellor output shaft; a fuel pump and an oil pump.

The propellor output shaft may extend through the container to convey drive to the propellor. A sealed bearing may be provided where the propellor output shaft penetrates the wall of the container.

Part of the internal volume of the container is not occupied by the drive mechanism 204 or other equipment as identified above, but is empty and filled with air. The container is mounted to the boat so that in at least an operational state of the boat, when the boat is being propelled forwards, the total weight of the container and its contents is less than the weight of the water displaced by the submerged volume of the container, meaning that the container provides buoyancy to the boat. For a typical powered boat there is a tendency for the stern to go lower in the water when the boat is under power than when it is in its static floating attitude. The container is mounted to the boat so that at least when the boat is in an under-way configuration the container provides additional buoyancy to the boat. The container may be mounted so as to provide additional buoyancy to the boat in most or all under way configurations or when the boat is in its static floating attitude. When the container provides additional buoyancy to the boat in this way, it can have the effect of reducing the drag to the stern of the boat in comparison to a boat with a similar powertrain mounted in a similar location. The buoyancy of the container can cause the stern of the boat to ride higher in the water than the stern of a comparable boat without the container.

The opening for providing access to the interior of the container may conveniently be located on an upper face and/or on a side face of the container. The cover for closing the opening me be constituted by a single solid piece for acting as a lid to the box, or by a plurality of pieces such as two doors. Such pieces may be connected by hinges. In all embodiments, the container is watertight when the opening is closed. Figure 2a shows a single lid 202 attached to the container with hinges 203 positioned on the rearmost side of the container. When the lid is closed, it may lie generally parallel with (i) a horizontal plane when the boat is in its static floating configuration and/or (H) a deck of the boat. When the lid is closed, the forward edge of the lid may lie adjacent the transom. In a closed configuration, the lid 202 can extend the useable area of the hull. In a closed configuration the lid 202 can provide a step-on platform. A user of the boat can stand on the platform to embark or disembark the boat or to enter the water. The upper face of the container may serve as a bathing or swim plafform. The upper face of the container may be equipped with a surface for increasing grip when a user of the boat steps on the platform. In this way the powertrain container can in effect extend the length of the boat.

The exterior of the container may be provided with protruding ribs extending generally along the longitudinal axis of the boat. These ribs may help to increase the stability of the boat in roll and pitch. The ribs may be located on the underside and/or the sides of the container.

The lid 202 may be moved away from the opening 205 defined by the container walls. When the lid is moved away, the opening is open so that the interior of the container can be accessed. An internal stay-hinge may be positioned in the container for supporting the lid in an open position. In the open position, the contained powertrain 204 may be accessed for servicing and repair. The lid 202 may be sized to exceed the external dimension of the opening 205. The lid may have a flexible gasket on an internal perimeter so that it fits tightly to seal the container. Alternatively the container may be provided with a flexible gasket that fits tightly to the lid.

Figure 2b shows an alternative closure for the container 201 with two doors 202 that are hinged about axes running generally along the longitudinal axis of the boat. In an open configuration, an opening 205 defined by the internal walls of the container is visible. In figure 2b attachment of the doors 202 to the container 201 is shown by hinges 203. A powertrain 204 is contained within the container 201 and surrounded by air.

The powertrain or drive mechanism 204 may be removable from the container 201. In one embodiment, the drive mechanism is removably attached to at least one internal surface of the container. The powertrain may comprise an electric motor, a cooling system, and drivetrain. The drivetrain may couple the drive mechanism to a propellor that is outside of the container. The electric motor may connect to one or more batteries in the hull of the boat by cables, suitably high voltage cables. Within the container components of the powertrain may be secured by the internal base having a moulded shape that corresponds to the shape of the component. Alternatively, removable attachments such as clips or hooks may be used to hold the powertrain in a fixed position within the container. The drive mechanism may be housed in the container such that access for servicing and repair is possible without removal of the drivetrain from the container.

The container 201 housing the powertrain 204 is readily removable from the main hull. This removal of the complete unit allows replacement and allows remote servicing of the powertrain and container. Quick connects and/or dry break couplings are used between the container and boat. The removal and replacement of the container and powertrain is simplified by the use of these connections.

Figure 3 shows an aft section of a boat 300 with a sealable powertrain container 301 equipped with a deployable platform 302 for extending the hull. In a stowed (undeployed) configuration, the platform 302 is folded away and rests on the lid of the sealable powertrain container. The platform may extend the boat's length, being deployable from the stowed configuration, shown by the dashed line in figure 3, to a deployed configuration where it is positioned above a propellor. The platform functions as a dive platform. It may facilitate easy access to the water for search and rescue operations as well as leisure activities. The platform may be equipped with a swim ladder which can extend into the water to assist a swimmer in boarding. In a further embodiment also shown in figure 3, a deployable platform 303 is attached to a side of the powertrain container such that in a deployed position it extends the boat's beam.

There may be two such platforms on opposing sides of the container.

In one embodiment, the deployable platform 302 comprises a substantially rigid surface and at least one hinge 304 for attachment to an upper surface of the container. As an alternative, the deployable platform may be inflatable. In a stored configuration the platform is not inflated. The platform may be manually inflated. Alternatively, there may be an automatic inflation system that can be activated by a triggering mechanism accessible from the boat. The triggering mechanism may, for example, be a pull cord or button.

In another embodiment the deployable platform may comprise a plurality of hollow rigid units telescoped within each other. In an undeployed configuration each sub-unit is housed within a larger unit. The sub-units can be withdrawn from each other to extend the platform. In a deployed configuration each unit provides a rigid surface.

As seen in figure 3, the powertrain container has a beam less than the beam of the stern. The beam of the container may be less than that of the boat's transom and/or less than the maximum beam of the boat's hull. The part of the container below the boat's waterline may be entirely within the projection of the transom and/or the hull on to a plane perpendicular to the longitudinal axis of the boat.

In an embodiment, the powertrain container is removably mounted to the stern of the boat. A mounting structure at a transom for attaching the container may be built into the transom board or provided as an additional component to an existing stern structure. A structural fixing system for supporting the container and its contents may be used.

Figure 4 shows a structural fixing system for reinforcing a transom. The structural fixing may be a rigid brace. The structural fixing may be a reinforcing beam for strengthening the transom of a boat. A central reinforcing beam 402 is attached to the main hull by bolts 409 into a plate and insert 407 and by bolts 409 at the transom 401. There may be additional struts on either side of the reinforcing beam for increasing the structural support. The struts may be rigid braces. The struts may be made of a rigid, low-density material such as aluminium. The struts may be fitted to existing structural stringers in the main hull of a boat. The reinforcing beam 402 may comprise a horizontal brace plate 403, it may further comprise a vertical brace plate 404.

Existing outboard engine mounting holes in the transom may be used to fasten the mounting plate 408 and structural support. The bolts 409 may be inserted through existing mounting holes in the transom 401. Alternatively, new holes may be drilled in the transom for fastening the reinforcing beam 402 to the transom. A mounting plate 408 may be disposed between the reinforcing beam 402 and the transom 408. The mounting plate may increase the grip between the bolted components. A container as shown in Figures 1 to 3 may be attached on the opposing side of the transom to the structural support. i.e. outside of the hull. The structural support may cantilever the weight of the container on the transom.

Figure 4 shows a pole 405 extending from a horizontal brace plate 403, mounted on a plate 406. The pole 405 may be hollow. The pole may have an upper end provided with an opening and be coupled to an internal combustion engine (ICE) to serve as an inlet. An ICE may be cooled by air drawn through the hollow pole 405. The pole may have an integrated ICE air intake system. The upper end of the air intake system is positioned away from water to prevent water entering and damaging the ICE. The air intake system may comprise a shut-off valve. The shut-off valve may be a float valve activated if the craft is inverted.

The pole 405 has a surface for mounting equipment such as a light, navigation equipment and for towing loads positioned outside of the vessel. The pole may be used as a grab rail for access on and off of the sealable powertrain container.

The container may support one or more than one propellor. The propellor may be of any convenient form.

The vessel may be a rigid inflatable boat (RIB) provided with inflated tubes disposed on opposing sides. The inflated tubes may be extended to accommodate the length of the container. The extended inflated tubes may be a separate tube attachable to each of the existing tubes on the RIB. Figure 5 shows a cross section of a RIB with side tubes 504 and hull 501. There is a container 502 within the profile of the hull 501.

An internal combustion engine 503 is disposed in the container 502. The engine 503 may be fixed to the inside of the container by an attachment 506. The container is preferably positioned centrally within the cross section of the boat. The engine 503 may be removable from the attachment 506. The container 503 may be removable with the engine inside by lifting it up, this allows easy servicing of the drive components. A drive unit 505 may be positioned such that it is submerged below a water line 508 when the boat is in water. The drive unit 505 may be a linear jet propulsion system. An outrigger section of the hull 507 acts as a stabiliser and hydrofoil surface with minimal wetted surface area.

Figure 6 shows a series hybrid layout within a container 601. The container 601 may have a subsection 607, this subsection may be removable from the container. The subsection 607 may contain a generator or plurality of generators 606 and an engine 603. The container hay house electric motors 605. The motor 605 may be coupled to a drive unit 602 by a driveshaft 604 for transferring mechanical drive. The drive unit 602 may be enclosed, for example it may be a linear jet propulsion system with high efficiency, it may be a conventional propellor. The series hybrid layout has a central engine 603 with twin drive systems 602 on either side, this configuration improves the steering performance, weight distribution and manoeuvrability. The hybrid layout is preferable to a linear configuration of the engine and drive unit as it is more compact. The electric motors 605 may be connected to batteries. In this configuration, the weight of the batteries may be optimally positioned in the main hull to reduce drag at the stern.

Figure 7 shows three alternative configurations of drive systems within a sealable container 701. Figure 7a shows a mechanical hybrid configuration with an engine 703 positioned opposite a generator 702. Mechanical drive is transferred by the driveshaft 704 to the propellor 705. The length of the container 701 relative to the length of the boat is shorter than if a series drive system were used. In one embodiment, the length of the container 701 is less than 70cm. The short container allows increased manoeuvrability of the boat.

Figure 7b shows a hybrid configuration with an engine 703 and generator 702. The generators 702 may be connected to batteries positioned within the hull of the boat.

Figure 7c shows a twin mechanical drive configuration with two engines 703 each connected to a drive shaft 704 powering a propellor 705. This configuration allows high power performance while maintaining a relatively short container 701. The container is removable from the boat for easy servicing and replacement of the drive components.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description, it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

CLAIMS1 A boat having: a hull comprising a stern; and a sealable powertrain container housing a drive mechanism for driving the boat, the sealable powertrain container being located at the stern of the boat and mounted relative to the hull so as to increase the buoyancy of the boat when the boat is under way.
2 A boat as claimed in claim 1, wherein the sealable powertrain container comprises an opening for providing access to an interior of the container and a closure movable to close the opening in a watertight manner.
3. A boat as claimed in claim 1 or 2, wherein the drive mechanism is removable from the powertrain container through the opening.
4 A boat as claimed in any preceding claim, wherein the container defines an exterior underside surface thereof, the container being located so that there is a stepped transition from a major underside surface of the hull to the underside surface of the container.
5. A boat as claimed in claim 4, wherein the exterior underside surface of the powertrain container is located at a shallower draft than the exterior underside surface of the hull at the stern thereof.
6 A boat as claimed in claim 5, wherein the powertrain container carries a propellor drivingly coupled to a powertrain located in the container, the propellor being located at a greater draft than the exterior underside surface of the powertrain container.
7. A boat as claimed in any preceding claim, wherein the powertrain container comprises an upper surface defining a walk-on platform.
8. A boat as claimed in any preceding claim, wherein the powertrain container comprises a deployable walk-on platform.
9 A boat as claimed in claim 8, wherein the deployable platform comprises a substantially rigid surface element and at least one hinge whereby the surface element is attached to a body of the container
10 A boat as claimed in claim 8, wherein the deployable platform is inflatable.
11 A boat as claimed in claim 8, wherein the deployable platform is telescopic.
12. A boat as claimed in any preceding claim wherein the powertrain container has a width equal to or less than the width of the stern of the hull of the boat.
13. A boat as claimed in any preceding claim wherein the powertrain container is removably mounted to the stern.
14. A boat as claimed in any preceding claim further comprising a mounting structure at a transom for attaching the powertrain container.
15. A boat as claimed in any preceding claim wherein the drive mechanism is removably attached to at least one internal surface of the container.
16. A boat having: a hull comprising a stern and a base; a rigid brace attached between the stern and base of the hull for reinforcing the structure of the boat; and a hollow pole comprising an upper end and an opening coupled to an internal combustion engine to serve as an inlet.