Embodiments of the present disclosure generally relate to marine propulsion systems. More specifically, the present disclosure relates to modular, replaceable parts enclosing the propeller shaft and extending from the propeller housing (e.g., the skeg, leading edge, and/or trailing edge of a propeller housing).
Historically, the lower unit (torpedo) and skeg section of an outboard motor has a geometry that is determined from manufacture and cannot be changed without significant challenges. Typically, a traditional propulsion system is optimized for one design of propeller operating within specific RPM ranges. Variations between propellers include, but not limited to, diameter, pitch (distance travelled per revolution), rake and hub diameter. Historically, the skeg is manufactured as a single unit with the bullet, therefore, creating challenges if the dimensions require changing. For protection to the propeller, the skeg extends at least as deep as the propeller to inhibit submerged bodies striking the propeller. This limits the size of propeller that can be used as it cannot exceed the depth of the skeg. It is detrimental to use a skeg that is significantly larger than the propeller used as it will increase drag and will increase the draft of the boat (the vertical distance between the water line and deepest point). The leading edge of the torpedo, in some embodiments referred to as a nose cone, pushes through the flow and is designed to minimize drag while allowing water intakes to ingest water for cooling circulation. The optimal profile for a nose cone can change drastically depending on the application. Traditional outboard systems are limited in their ability to change the contour and in many embodiments rely on additional components to be added to adjust the shape. Other variations include the location of water intakes. The tail cone is used to channel the fluid flow from across the body of the torpedo to the hub of the propeller. Traditional outboard systems are optimized for a single hub design, limiting the ability to function efficiently with a range of propellers. Traditionally, outboard motors have been combustion driven and therefore require somewhere to vent exhaust. Often, outboards will use a thru-hub exhaust propeller design that uses a round barrel to which the blades are attached. The exhaust is routed through the gear case and center of the propeller. This has advantages with dampening the exhaust noise and minimizes the induced ventilation on the propeller. However, it requires a larger hub and therefore reduces the frontal blade area of the propeller.
Embodiments of the present disclosure are intended to address the above challenges as well as others.
The purpose and advantages of the disclosed subject matter will be set forth in and apparent from the description that follows, as well as will be learned by practice of the disclosed subject matter. Additional advantages of the disclosed subject matter will be realized and attained by the methods and systems particularly pointed out in the written description and claims hereof, as well as from the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the disclosed subject matter, as embodied and broadly described, the disclosed subject matter includes A marine propulsion apparatus, the apparatus including a lower unit, the lower unit including a center body, the center body comprising a leading edge disposed at a first end of the center body and a trailing edge disposed at a second end of the center body, defining a substantially cylindrical portion therebetween. The lower unit including a modular nose cone member releaseably coupled to the leading edge of the center body, the modular nose cone further comprising a first curved conical surface and a first mating surface. The lower unit including a modular tail cone member releaseably coupled to the trailing edge of the center body, the modular tail cone further comprising a second conical surface and a second mating surface, the second mating surface oriented towards and parallel to the first mating surface and a skeg affixed to a bottom side of the center body.
To achieve these and other advantages and in accordance with the purpose of the disclosed subject matter, as embodied and broadly described, the disclosed subject matter includes A marine propulsion apparatus including a torpedo. The torpedo including a center body, the center body including a leading edge disposed at a first end of the center body and a trailing edge disposed at a second end of the center body, defining a substantially cylindrical portion therebetween. The torpedo including a modular nose cone member releaseably coupled via at least one fastener to the leading edge, the modular nose cone further including a first curved conical surface and a first mating surface, the first mating surface having a first diameter substantially the same as the leading edge. The torpedo including a modular tail cone member releaseably coupled via at least one fastener to the trailing edge, the modular tail cone further including a second conical surface and a second mating surface, the second mating surface oriented towards and parallel to the first mating surface and wherein the second mating surface includes a second diameter substantially the same as the trailing edge. The torpedo including a propeller shaft disposed axially within the center body, terminating at the modular nose cone at a first end, and extending through the trailing edge at a second end. The torpedo including a propeller rotatably fixed to the propeller shaft aft of the modular tail cone, the propeller including a plurality of blades. The torpedo including a propeller cone rotatably fixed to the propeller shaft aft of the propeller and a skeg affixed to a bottom side of the cylindrical portion of the center body.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the disclosed subject matter claimed.
The accompanying drawings, which are incorporated in and constitute part of this specification, are included to illustrate and provide a further understanding of the method and system of the disclosed subject matter. Together with the description, the drawings serve to explain the principles of the disclosed subject matter.
A detailed description of various aspects, features, and embodiments of the subject matter described herein is provided with reference to the accompanying drawings, which are briefly described below. The drawings are illustrative and are not necessarily drawn to scale, with some components and features being exaggerated for clarity. The drawings illustrate various aspects and features of the present subject matter and may illustrate one or more embodiment(s) or example(s) of the present subject matter in whole or in part.
The present disclosure details the components and their benefits that comprise a system of modular fairings for an outboard motor. The fairings of an outboard motor include any component affixed to the main structure of the outboard. This includes, but is not limited to, a nose cone at the leading edge of the lower unit. A skeg that protrudes below the lower unit, a tail cone that affixes to the rear of the lower unit, a prop cone that affixes aft of the propeller, onto the propeller shaft. This system of modular components is designed such that equivalent components can be interchanged with the goal of optimizing the propulsion system for different use case applications. Parameters that can be changed between components include, the length of the skeg, the outer contour of the nose cone and tail cone and the diameter and shape of the prop cone. In some embodiments, additional cooling elements can be added to the system to increase the thermal dissipation capabilities of the system.
The drag on the submerged portion of an outboard motor opposes the thrust generated by the propeller. The relationship between the speed of the object and the drag created is not a linear relationship and is highly dependent on the frontal area size, shape and orientation to the flow of water. The leading edge and trailing edge work in conjunction with each other to transmit a high energy flow across the propeller while minimizing the drag. Using a modular design, the nose cone and tail cone can be changed together or separately to modify the flow that is reaching the propeller. Variations include but are not limited to, changes in the focal point and radius of the curve to optimize the drag effect for a certain flow velocity. The tail cone works in conjunction with the nose cone to bend the flow to meet the propeller blades in a continuous high energy flow path. A modular tail cone allows the torpedo to optimize the flow for different hub diameters. The present disclosure enables one propulsion system to operate at higher efficiency across multiple different operational profiles.
The powertrain of an outboard motor generally includes a prime mover, such as a combustion engine or electric motor, a vertical drive shaft, bevel gear, clutch, and propeller shaft (to which a propeller is attached). Bevel gears are gears between two intersecting shafts where the tooth-bearing faces of the gears are conical in shape. Bevel gears offer higher efficiency than other gear options and may allow for a gear reduction between the intersecting shafts. A clutch is used to allow the prime mover to operate in a single direction but also may allow the propeller shaft to rotate in both clockwise and counterclockwise directions. In various embodiments, outboards may use a dog clutch to switch between forward, neutral and reverse. This requires engaging and disengaging the shifting gears, leading to expedited wear on the teeth of the gear. To minimize this wear, the entire assembly may be submerged in an oil or lubricant that can be harmful to the environment and difficult to dispose of. Heat dissipation from key components including but not limited to, the prime mover, gears and bearings may be integral for reliable operation of this type of outboard motor. Outboard motors may ingest fluid (e.g., sea water) from the body of fluid (e.g., the sea) in which it operates to circulate the fluid around the system and cool components. However, this external fluid intake can bring in contaminants, including but not limited to salt, sand, and/or dirt that can expedite the wear and corrosion process. In some embodiments, the prime mover may be housed within the lower unit, below the water line. This configuration brings advantages with simplicity but may limit heat transfer capability. In various embodiments, other means of power transmission in place of a vertical drive shaft and bevel gears include, for example, chain-driven and belt-driven systems. In various embodiments, synchronous belts may be strong and durable, enabling potential use in higher power marine engine transmissions. In various embodiments, implementation of such belt or chain technologies may present challenges in physical housing arrangements and mechanical assembly as frontal area and hydrodynamic shape of submerged portions of marine propulsion systems greatly affects system drag and efficiency.
Accordingly, marine propulsion systems are needed that are optimized for belt-driven and chain-driven motors while reducing drag (e.g., improving hydrodynamic qualities) and improving heat dissipation. Embodiments of the present disclosure are intended to address the above challenges as well as others.
In various embodiments, a sterndrive or outboard marine propulsion system includes a prime mover that transmits power to a driven shaft through a synchronous belt, an anti-ventilation plate, a lower unit housing, one or more skegs extending from the bottom of the lower unit housing, and a set of struts (e.g., two struts) that connects the lower unit housing to the anti-ventilation plate and attachment point on the cowling (and/or frame structure within the cowling). In various embodiments, the set of struts may be substantially aligned (e.g., parallel) with one another. In various embodiments, each strut may include one or more (e.g., a plurality) of removably attachable and modular trailing edge pieces. In various embodiments, removably attachable trailing edge pieces may allow for fine tuning of hydrodynamic properties.
In various embodiments, the attachment point connects the midsection to the lower unit and prime mover in the embodiment of an outboard marine propulsion system or connects the lower unit and outdrive in the case of a sterndrive marine propulsion system. In various embodiments, particular variables of the system enable lower drag, higher performance, and efficient accommodation of belt drive technologies. In various embodiments, components of the marine propulsion system may be modular, replaceable, and/or built such they have integrated cooling channels. In various embodiments, integration of heat dissipation functionality into a multi-strut (e.g., dual-strut) architecture may provide increased surface area from the multiple struts to optimize heat transfer capability. In various embodiments, multiple struts (e.g., two struts) increases the surface area of the struts in contact with water, thereby improving heat transfer (e.g., conduction) with the water (similar to the heat transfer of fins).
In various embodiments, frontal area and hydrodynamic shape of submerged portions of marine propulsion systems may affects system drag and efficiency. Reducing the drag on a marine propulsion system has direct improvement on the net efficiency of the system. In various embodiments, as the set of struts may be submerged when in use, the set of struts may have any suitable hydrodynamic shape to thereby reduce and/or optimize drag. For example, each strut may include an airfoil shape where the leading edge of the airfoil corresponds to the leading side of the strut.
When in operation, a belt generally has a tight side and a slack side. In various embodiments, the belt may be isolated (i.e., sealed) from the surrounding body of water in which the motor operates. In various embodiments, both sides of the belt may be supported to provide tension to the belt. In various embodiments, providing tension to the belt may reduce (e.g., stop) contamination from the surrounding water. In various embodiments, the marine propulsion system may include, among other things, a continuous loop power transmission device. For example, the prime mover may be mechanically (e.g., rotationally) coupled to the propeller via a belt or chain.
In various embodiments, each strut may be positioned at a predetermined distance from one another to thereby allow fluid flow between the struts. For example, in a dual-strut arrangement, the struts may be positioned about 2 to about 24 inches from one another. In various embodiments, the struts may be positioned about 1.5 to 6 inches from one another. In various embodiments, in larger applications (e.g., yachts, tugboats, etc.), the struts may be positioned several feet apart. In various embodiments, the struts may be positioned up to about 12 feet apart. In various embodiments, the spacing of the struts may be dependent on one or more performance factors, such as, e.g., (1) hydrodynamic interactions between the struts and/or (2) hydrodynamic drag of the lower unit. In various embodiments, as struts become wider, fewer fluid interactions may occur between the multiple struts (interference). In various embodiments, wider struts may improve certain performance factors. In various embodiments, the size (e.g., drag area) of the lower unit may be minimized to thereby minimize drag. In various embodiments, the size of the lower unit may be minimized by providing a small frontal area of the lower unit. In various embodiments, the size of the lower unit may be proportional to the size of the struts. For example, for wider struts, a larger lower unit may be provided. In various embodiments, the struts may not be parallel. For example, the struts may be non-linear or disposed at an angle (e.g., a ‘V’ shape) with respect to the horizontal (sea level).
In various embodiments, each strut may include a cross-sectional profile of the vertical struts that minimizes the drag through water. In various embodiments, the cross-sectional profile may reduce (e.g., minimize) the drag area while allowing for enough void space to house the continuous loop (e.g., belt or chain). In various embodiments, each strut may include an airfoil shape. In various embodiments, any struts (e.g., some or all struts) may have a substantially uniform shape along its length. In various embodiments, any struts (e.g., some or all struts) may have a varying shape along its respective length. For example, a strut may taper, from the leading to trailing edges, from a wider airfoil (having a higher drag area) to a thinner airfoil (having a lower drag area) or vice versa. In various embodiments, any struts (e.g., some or all struts) may have a substantially uniform width (in the direction of flow) along the length of the strut. For example, an airfoil shape may have a substantially similar (e.g., equal) chord length and/or camber line along the entire length of the strut. In various embodiments, any struts (e.g., some or all struts) may have a varying width (in the direction of flow) along the length of the strut. For example, an airfoil shape may have a varying chord length and/or camber line along the entire length of the strut. The struts can have mirroring shapes that are symmetrical about a central axis passing through the struts: alternatively, each strut can be formed with a unique shape/profile relative to the adjacent strut.
In various embodiments, each strut may include separate void spaces configured to house each side of the continuous loop (i.e., the slack side and the taut side). In various embodiments, the separate void spaces within either one or all of the vertical struts may be configured to transfer fluid (e.g., a heat transfer fluid) throughout the outboard.
In various embodiments, one or more of the struts may include a parting line to thereby separate the strut into two or more pieces. In various embodiments, parting lines allow for ease of access so that a continuous loop (e.g., chain or belt) may be installed or removed during or after manufacture (e.g., for repairs). The parting line(s) can be extend along the entire portion of the strut (e.g. between nose cone and anti-ventilation plate).
Recent advancements in material technologies have enabled the development of more robust synchronous belt drives which have the potential to increase efficiency, decrease noise, reduce maintenance, and lower cost. The present disclosure enables the use of a synchronous belt in a marine propulsion system, through a multi-strut body arrangement where each side of the belt travels through a different strut. Additionally, the present disclosure also provides a method for using electronic reversing from an electric prime mover, thereby eliminating the need for a complex mechanical shifting solution.
In various embodiments, the multi-strut design minimizes fluid flow obstruction to the propeller while moving. In various embodiments, the multi-strut (e.g., dual-strut) design reduces drag-inducing frontal area (i.e., the drag area) while increasing robustness of the entire system. In various embodiments, the strut 116 and anti-ventilation plate 120 interface is integrally formed. In various embodiments, the strut 116 and anti-ventilation plate 120 interface is mechanically fastened (e.g., with bolts and nuts). In various embodiments, the bottom of the struts may be integrally formed with the lower unit 114. In various embodiments, the lower unit 114 may be bullet-shaped (a bullet+bullet casing). In various embodiments, a first portion (e.g., the taut side) and a second portion (e.g., the slack side) of a synchronous belt 130 is protected from water and/or external fluids inside a void space within first and second struts 116. Thus the belt 130 extends (vertically when in operation) through the first strut 116, into the lower unit 114, where it engages and drives the propeller 110 forward/reverse), and up through the second strut 116, and back into the cowling 107.
In various embodiments, drag may be reduced through hydrodynamic shapes applied to the leading edges 117 and trailing edges 118 of the struts 116. In various embodiments, convex surfaces on the sides of the struts 116 between the leading edges 117 and the trailing edges 118 reduce form drag and wave creation. In various embodiments, the profile of the convex surfaces does not have to be symmetric between struts and could be changed for different applications (i.e., not all struts have to be identical in shape). In various embodiments, struts 116 may be reflections of one another (e.g., a first strut may be a reflection of a second strut). In various embodiments, the sides of the struts 116 may be substantially parallel and of equivalent lengths. In various embodiments, the struts could be non-parallel. In various embodiments, the space between the struts may increase or decrease over the height of the struts.
In various embodiments, the sides of the struts 116 may have no concavity. In various embodiments, the leading edges 117 can be integrally formed with the strut 116. In various embodiments, the leading edges 117 may be separately manufactured and removably fastened to the strut 116. In various embodiments, the trailing edges 118 may be integrally formed with the strut 116. In various embodiments, the trailing edges 118 may be separately manufactured and removably fastened (e.g., with a screw, bolt, etc.) to the strut 116 via, for example, a strut attachment point. In various embodiments, the leading edges 117 and/or the trailing edges 118 may be modular and swappable for performance optimization. Additionally or alternatively, the strut(s) can include an access panel to allow repair and inspection of the belt. The access panel can be spaced from the leading/trailing edge and located within the generally planar section of the strut(s).
In various embodiments, the strut(s) may include active control of surface shapes of the leading and/or trailing edges during operation. For example, an electronic control (e.g., real time or manual) may change a camber or chord length of an airfoil shape. In another example, an electronic control (e.g., real time or manual) may change a width (e.g., drag area) of an airfoil shape such that the continuous loop (e.g., belt) has enough room to operate in the void space.
Further aiding in hydrodynamic drag reduction and increasing propulsive efficiency is the overall shape of the architecture. In various embodiments, incoming fluid flow interacts with the nose cone 115 first. In various embodiments, the nose cone 115 geometry may be designed with a smooth transition from the nose cone 115 over the nose cone/lower unit interface and to the lower unit 114. In various embodiments, the nose cone 115 is removable and swappable. In various embodiments, the nose cone 115 may include any suitable shape. For example, the nose cone 115 may include a blunt bullet-like shape. In various embodiments, a center body 113 of the lower unit 114 may have a substantially cylindrical shape (e.g., a bullet casing shape). In another example, the nose cone 115 may be substantially conical with a sharper point. In various embodiments, as fluid flow passes the lower unit 114, the tail fairing 112 may minimize loss-inducing boundary layer separation over the tail fairing/lower unit interface as boundary layer separation may cause turbulent flow thus increasing pressure drag on the propulsion system 100. In various embodiments, the tail fairing 112 is shaped such that the tail fairing/propeller hub interface hydrodynamically meshes with the propeller hub to optimize flow entering the propeller. Thus, the struts 116, lower unit 114, nose cone 115 and tail faring 112 can be configured with a virtually seamless design in which there are no abrupt changes in size/shape/diameter, with the assembly of these components forming a continuous outer surface area to minimize drag.
In various embodiments, the tail fairing may be a frustoconical shape tapering from a larger diameter at the center body 113 to a smaller diameter at the propeller 110. In various embodiments, as the propeller 110 spins and generates regions of high and low pressure, flow is directed over a propeller tail cone 111 to reduce turbulent flow and thus further minimize drag on the propulsion system 100. In typical combustion-type marine engines, engine exhaust is generally directed down through a singular piece and out through the center of the propeller. The present disclosure eliminates this style of exhaust and allows for a more efficient overall hydrodynamic approach.
In various embodiments, one or more skeg 124 may be attached to the center body 113 of the lower unit 114. In various embodiments, the center body 113 may include one or more skeg attachment points configured to allow attachment of one or more skegs 124. In various embodiments, the skeg 124 may have a generally fin-like shape. In various embodiments, the skeg 124 may have a constant thickness along its length. In various embodiments, the skeg 124 may have a varying depth along its length. For example, the skeg 124 may taper from a first, larger depth, d1, to a second, smaller depth, d2. In various embodiments, one side of the skeg 124 may be vertical while the other side tapers. In various embodiments, both sides of the skeg 124 may taper. In various embodiments, the skeg 124 may have a curvilinear or airfoil shape, similar to the struts 116. In various embodiments, the skeg 124 is removable and replaceable at the skeg/lower unit interface. In various embodiments, the skeg 124 can be integrally formed at the skeg/lower unit interface. In various embodiments, the skeg 124 contributes to stability and hydrodynamic flow interaction by having a trailing edge that minimizes flow disturbances going into the propeller 110. In various embodiments, the bottom-most edge of the skeg 124 may be lower than the blades of the propeller 110, providing protection to the propeller 110 from physical object strikes. Additionally or alternatively, the location of the skeg 124 can be adjusted up/down stream relative to the lower unit 114.
In various embodiments, coolant can flow bi-directionally through the struts 116 and to the thermal circuit 140 via the coolant passage 117a. In various embodiments, the coolant passage 117a may comprise tubing, hosing, pipes, and/or other methods of fluid transfer. In various embodiments, the thermal circuit may include an electronic controller pump and/or heat producing components including but not limited to the power electronics and prime mover. In various embodiments, a set of coolant port seals ensures the heat transfer fluid does not become contaminated. In various embodiments, additional voids may be provided in the trailing edge(s) 118, belt accommodation void 131, tail fairing 112, and/or lower unit 114 that can be used for additional coolant passages. In various embodiments, the longitudinal width of the belt accommodation void 131 can be varied for belts of different sizes. In various embodiments, the trailing edge 118 may be mechanically fastened by a set of trailing edge fasteners 118a configured to anchor into an anchor panel 118b (e.g., a T-block). In various embodiments, this method of attachment allows the trailing edges 118 to be separated from the struts 116 for installation and removal of the belt 130. In various embodiments, the belt accommodation void 131 may be optimized such that the size (e.g., width of the void space) of the void is minimized. In various embodiments, less void space may be better from a hydrodynamic standpoint (e.g., less drag area). In various embodiments, the belt accommodation void 131 may be about ⅛ inch on either side of the belt 130. In various embodiments, the sprocket gap 125 may have a similar ⅛″ gap. In various embodiments, the sprocket gap 125 may be smaller than the space between the belt 130 and an interior side of the belt accommodation void 131 as the belt may not have as much motion around the sprocket 126. In various embodiments, the belt accommodation void 131 may include a spacing (e.g., width) of about 0.01 inch to about 0.25 inch on either side of the belt. For example, 0.25 inch on either side of the belt 130 would result in 0.25 in+0.25 in+belt thickness (in inches) for the total width of the belt accommodation void 131. In various embodiments, the belt accommodation void 131 may include a spacing (e.g., width) of about 0.01 inch to about 6 inches on either side of the belt. In various embodiments, the spacing may scale with system size. In various embodiments, the spacing (e.g., width) may be about 12 inches on either side of the belt.
In various embodiments, any struts may include non-linear shapes. In various embodiments, to accommodate a non-linear shape, the belt may remain substantially straight, but and the width of the belt accommodation void 131 (space between the belt and inside walls of the strut voids) may vary. In various embodiments, the struts may include pulleys (e.g., roller pulleys) configured to create a curve for the belt 130 to follow. In various embodiments, low friction pads can be positioned at any suitable position within the belt accommodation void 131. In various embodiments, any combination of the above three methods could work together to achieve a non-linear strut shape. In various embodiments, the leading edge of the struts may include a non-uniform profile (viewing from the top-down).
The various components disclosed herein (e.g., struts, nose cone, fairing, skeg) can be formed from a variety of materials including metals (e.g., aluminum, steel, titanium, etc.) rigid polymers and plastics, wood, etc. In various embodiments, the various components may include composite materials (e.g., carbon fiber, fiberglass, etc.). In various embodiments, the various components may include rubber. In various embodiments, the various components may include thermoplastics. In various embodiments, the various components may include any suitable metal-based alloys. In various embodiments, the various components may include materials with high thermal conductivity and high corrosion resistance. In various embodiments, the various components may include one or more coatings (anodize, powder coat, chemical vapor deposition, paint, etc.). In various embodiments, the various components may be formed from more than one material (i.e., nose cone could be mostly aluminum with a rubber based tip).
In various embodiments, the tail cone 1205 is connected to the lower unit 1203 via fasteners (e.g., screws, clips, nut and bolt, latch, etc.) or using other non-permanent attachment methods. In various embodiments, the tail cone 1205 follows a continuous contour to the lower unit 1203. In various embodiments, the tail cone 1205 tapers from a larger diameter (e.g., diameter of the lower unit 1203) to a smaller diameter (e.g., the diameter of the propeller hub). In various embodiments, aft of the tail cone 1203, the propeller shaft 1204 extends outwardly from the lower unit and tail cone 1205 to support a propeller 1312. In various embodiments, the tail cone
In various embodiments, the skeg 1207 extends at least as deep as the propeller to thereby reduce the risk of submerged objects striking the propeller during operation. In various embodiments, the skeg 1207 is connected to the torpedo using mechanical fasteners that can be removed to replace the skeg to suit the size of the particular propeller (e.g., the longest radial length of the propeller).
In various embodiments, the nose cone 1208 acts as the leading edge of the lower unit 1203. In various embodiments, the nose cone 1208 may be shaped to optimize fluid flow around the lower unit 1203 and to the propeller 1312. In various embodiments, an outer contour of the nose cone 1208 includes a curve of constant or varying radius.
In various embodiments, the nose cone 1208 may be formed with a void space to house a fluid volume capable of dissipating thermal energy into the surrounding body of water. In various embodiments, the fluid may be a working fluid (e.g., a fluid having properties suitable to absorb energy and transfer the energy somewhere else). In various embodiments, the nose cone 8 connects to the lower unit 1203 with a continuous contour using either mechanical fasteners or other non-permanent bonding component. The leading edge 1210 of the vertical struts follows a curved profile. In some embodiments the curve is consistent along the length of the strut.
When moving through a fluid, drag is the resistive force that a body experiences. Drag typically has two causes: Friction forces, a shear stress acting parallel to the boundary layer between the body and fluid and Pressure forces, a stress acting normal (perpendicular) to the boundary layer. The coefficient of drag Cd is the sum of the total pressure (CP) and friction (Cf) across the entire surface area of the submerged body. This is calculated using the Drag Equation below:
Referring now to
The design of the tail cone is key to maintaining an attached, laminar flow that the propeller can use to generate forward thrust. As with the nose cone, different operating conditions will have different optimal propeller designs. Depending on the intended application, an optimal propeller may vary in blade shape/number or use a different hub diameter. Using a modular tail cone, it is now possible to select a tail cone profile that is optimized for a specific propeller.
Referring now to
While the disclosed subject matter is described herein in terms of certain preferred embodiments, those skilled in the art will recognize that various modifications and improvements may be made to the disclosed subject matter without departing from the scope thereof. Moreover, although individual features of one embodiment of the disclosed subject matter may be discussed herein or shown in the drawings of the one embodiment and not in other embodiments, it should be apparent that individual features of one embodiment may be combined with one or more features of another embodiment or features from a plurality of embodiments.
In addition to the specific embodiments claimed below, the disclosed subject matter is also directed to other embodiments having any other possible combination of the dependent features claimed below and those disclosed above. As such, the particular features presented in the dependent claims and disclosed above can be combined with each other in other manners within the scope of the disclosed subject matter such that the disclosed subject matter should be recognized as also specifically directed to other embodiments having any other possible combinations. Thus, the foregoing description of specific embodiments of the disclosed subject matter has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosed subject matter to those embodiments disclosed.
It will be apparent to those skilled in the art that various modifications and variations can be made in the method and system of the disclosed subject matter without departing from the spirit or scope of the disclosed subject matter. Thus, it is intended that the disclosed subject matter include modifications and variations that are within the scope of the appended claims and their equivalents.
This application is a Continuation of, and claims the benefit of priority under 35 USC 120 to Patent Cooperation Treaty Patent Application No. PCT/US22/46751 filed Oct. 14, 2022, which claims the benefit of priority under 35 USC 119 to U.S. Provisional Patent Application No. 63/256,404, filed on Oct. 15, 2021, the entirety of which are hereby incorporated by reference.
Number | Date | Country | |
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63256404 | Oct 2021 | US |
Number | Date | Country | |
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Parent | PCT/US22/46751 | Oct 2022 | WO |
Child | 18634105 | US |