ACTIVE BOW FOIL FOR SHIP MOTION CONTROL

Abstract

A bow foil stabilizer system is provided where the foil is configured to be mounted relatively close to the vessel hull, preferably less than three times a maximum thickness below the keel of the vessel in the area the foil is mounted to, more preferably the foil is mounted in a recess of the vessel, which recess is in the keel of the vessel. In certain embodiments, a lowest point of the foil is approximately level with the extended keel line and a control flap of the foil is configured to rotate at least partially into a recess of the vessel in the keel area. In further aspects, the foil is mounted with a chord thereof at an angle relative to the running trim of the vessel.

Description

FIELD OF THE INVENTION

The present disclosure relates to stabilizers and control systems for marine vessels. In certain embodiments, a foil stabilizer mounted towards the bow is envisioned for controlling pitch in monohull vessels and pitch and/or roll in multi hull vessels.

BACKGROUND

Traditional T-foils are often located near the bow of a vessel and may be used to control pitch and/or trim. These T-foils are spaced from the keel of the vessel hull with a strut and then a foil/wing extends from the strut in a generally outwards direction. The foil/wing in this T-foil design is positioned such that its centerline/chord line is parallel to the water surface or waterline of the vessel in at rest/flat conditions, particularly, the foil/wing is parallel to the running trim of the vessel so as to minimize drag and then control surfaces can be manipulated to create a pitch force. The strut is used to place the foil/wing well below the surface of the water and also out of the way of flow diversions caused by the hull.

This T-foil configuration creates several problems to which complicated solutions have been devised. Generally, the positioning of the foil below the keel line reduces the clearance the vessel may have in shallow harbors-essentially increasing the draft of the vessel. In order to solve for this, retractable T-foils have been designed whereby the strut is on a pivot that can rotate the foil up into the hull when the vessel is in a shallow location or otherwise generally not underway. This retractable feature requires the vessel to have openings to accommodate the retractable T-foil and also complicated and expensive attachment mechanisms which allow for the manipulation of the T-foil to allow retractability.

While fixed foils have been envisioned, these fixed foils are again mounted with a strut that increases the draft of the vessel such that the foil can be positioned in what is considered relatively clean flow that is not significantly impacted by the presence of the vessel. The fixed T-foil may be easier to attach to the vessel, but suffers the disadvantage of increasing the draft.

While the T-foil does provide desirable pitch and trim control capabilities to the overall stabilizer system, the tradeoffs of reduced draft can reduce the overall capabilities of the vessel when docked in terms of which harbors the vessel can enter and how close to land a vessel can be moored.

SUMMARY

The following presents a simplified summary of the claimed subject matter in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview of the claimed subject matter. It is intended to neither identify key or critical elements of the claimed subject matter nor delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts of the claimed subject matter in a simplified form as a prelude to the more detailed description that is presented later.

The foil/wing system described hereinbelow, according to various embodiments, addresses various challenges facing previously employed T-foil systems. A particular advantage of the system described herein is that the foil/wing is mounted in a fixed location directly to the keel of the vessel and also very close to that keel. This offers several advantages such as mounting the lift producing item to what is often the strongest (or one of the strongest) portions of the boat—the keel. Further, the foil is in some embodiments recessed into the keel to minimize drag. More generally, the foil is mounted in a manner that it does not increase the draft of the vessel. For example, the foil is mounted at or above the lowest point of the vessel where that “lowest point of the vessel” is not on the foil itself. Stated, differently, the propeller or keel or skeg is often the lowest point of the vessel and thus the bottom of the improved foil is at or above the lowest point of the vessel. This foil may be bolted to a mounting area of the keel that is recessed into the keel line or such that the lower surface of the foil is even with the keel. The foil also has a control surface/flap which can move up and down to create pitch forces on the vessel. Furthermore, since the foil is mounted relatively close to the vessel hull, the local flow is impacted by the hull, accordingly, the foil's centerline may be pitched permanently at an angle that renders the foil at an angle relative to waterline of the vessel, particularly, the foil is pitched at an angle such that it is not parallel to the running trim of the vessel. Depending on the vessel and its configuration and performance, the running trim may be determined based on a defined speed, for example a speed that is the ordinary or most common setting for operating in ideal conditions and based on a pre-determined weight and/or weight distribution of the vessel and thus the pitch/angle of the foil may be set relative to this running trim.

Thus, it is an object of the invention to provide pitch stabilizing control with reduced vessel draft compared to other bow mounted stabilizers and to provide a stabilizer that does not require retraction to achieve this reduced draft. It is further an object to provide the foil at a fixed non-zero pitch relative to the running trim of the vessel in order to reduce drag and/or undesirable lift forces.

These and other objects are achieved by providing a stabilizer foil for a vessel which includes a foil configured to articulate based on one or more control inputs to generate a control force, the foil having a lower surface, an upper surface and a maximum foil thickness. The foil is configured to attach to the vessel in a fixed position such that a lowest point of the lower surface is positioned less than three times the maximum thickness below a keel of the vessel in an area adjacent to the foil.

In certain aspects the lowest point is positioned less than three times the maximum foil thickness above the keel of the vessel in the area adjacent the foil. In other aspects, the foil is configured to be mounted in the fixed position at least partially in a recess of the hull, the recess located in a forward portion of the vessel. In still other aspects, the recess is in the keel and the lowest point of the lower surface is even with an extended keel line at the recess and a flap of the foil (or control horn thereof) is configured to rotate at least partially into the recess. In yet other aspects, the foil includes a mounting area comprising holes therethrough and bolts are configured to pass through the holes and into holes in keel support structure of the vessel. In still other aspects, the foil articulates by a control horn of the foil rotating to generate the control force. In still further aspects, port and starboard sides of the foil share a common center plane.

The above described and other objects are additionally achieved by providing a stabilizer for a vessel including a foil having a flap which is configured to articulate relative to the foil based on one or more control inputs. The foil is configured to mount to a bow area of the vessel in a fixed position such that a chord line of the foil is positioned at a non-zero angle relative to a running trim of the vessel.

In certain aspects, the non-zero angle is at least 1 degree, more preferably at least 3 degrees and in certain aspects in a range of 3-10 degrees, more preferably 3-8 degrees. In certain aspects the foil has a substantially symmetrical cross section (relative to the chord/centerline). In other aspects port and starboard sides of the foil share a common center plane. In still other aspects the foil is configured to attach to the vessel such that a lowest point of a lower surface of the foil is positioned less than three times the maximum foil thickness below a keel of the vessel in an area adjacent to the foil. In other aspects the lowest point is positioned less than three times the maximum foil thickness above the keel of the vessel in the area adjacent the foil. In yet further aspects, the foil includes a mounting area comprising holes therethrough and bolts are configured to pass through the holes and into holes in keel support structure of the vessel.

The above described and other objects are additionally achieved by providing a stabilizer foil for a vessel including a foil system mounted in a bow area of the vessel and including foil sections which extend outwards on port and starboard sides of the vessel and the foil sections have a maximum foil thickness. The stabilizer may be mounted on a vessel where the lowest point of the vessel is a point other than on the foil sections. In certain aspects a lowest point of the foil sections is no more than three times the maximum foil thickness below the lowest point of the vessel.

In certain aspects, the lowest point of the foil sections is at or above the lowest point of the vessel. In still other aspects, foil sections of the foil system share a common center plane. In yet other aspects, a highest point of the foil sections is no more than three times the maximum foil thickness above a lowest point of a keel of the vessel. In still other aspects, foil sections of the foil system share a common center plane. In still other aspects, the foil includes a flap which is articulated based on one or more control inputs to cause the flap to rotate to generate a control force.

DRAWINGS

FIG. 1 shows a perspective view of a bow of a vessel having a stabilizer according to the present disclosure.

FIG. 2 shows a bottom perspective view of FIG. 1.

FIG. 3 shows a top view of FIG. 1.

FIG. 4 shows a bottom view of FIG. 1.

FIG. 5 shows a side detail view of FIG. 1.

FIG. 6 shows a side detail view of the stabilizer of FIG. 1.

FIG. 7 shows a perspective view of the stabilizer of FIG. 1 during manufacture.

FIG. 8 shows a vessel with the stabilizer of FIG. 1 thereon.

FIG. 9 shows a perspective cross section view of a portion of the vessel of FIG. 8.

FIG. 10 shows a bottom detail view of the vessel of FIG. 8.

FIG. 11 is a side view of FIG. 9.

FIG. 12 is a functional flow diagram of an exemplary control system for the foil described herein.

DETAILED DESCRIPTION

Reference will now be made in detail to specific embodiments illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth to provide a thorough understanding. However, it will be apparent to one of ordinary skill in the art that embodiments may be practiced without these specific details. In other instances, known methods, procedures and/or components have not been described in detail so as not to unnecessarily obscure aspects of the embodiments.

As set forth above, FIGS. 1-4 show the portion 2 of the bow area of the vessel below the waterline 11 thereof. The bow 1 as shown is a bulbous bow, but the foil according to the present disclosure can be mounted on vessels with a variety of bow shapes. Further, it is envisioned that a multi hull vessel could use the foil described herein, for example with multiple foils. The foil 3 includes a first section 5 and a second section 4 which pivots/hinges relative to the first section. There may be several hinges 10 provided between the first and second sections. The foil 3 has a leading edge 6 and a trailing edge 13 and the chord of the foil is defined between the leading 6 and trailing 13 edges foil. An example of the chord line 22 is shown in more detail in FIG. 6. In certain aspects, the foil is mounted such that this chord line 22 is at an angle relative to the running trim of the vessel. The waterline 800 may represent the running trim in some examples. This angled mounting of the foil is provided since the foil is relatively close to the vessel hull. As a result, localized flow over the vessel means that the foil is not seeing a flow direction that is parallel to the running trim of the vessel. As a result of these localized flow directions/distortions, the foil is mounted in a pre-pitched manner such that at normal cruising speeds the foil is generating relatively low lifts with the flap 4 in a neutral position. Generation of lift creates drag and thus the pitching of the foil is designed to account for the localized flow variations. In traditional T-foil bodies which are mounted relatively far away from the vessel hull, these localized flow variations are not an issue as the foil is positioned in clean or relatively clean flows of water (e.g. not significantly disturbed by the vessel). However, these traditional T-foils create issues of higher drafts by virtue of seeking out this relatively clean water flow. Accordingly, to reduce the vessel draft by mounting the fin close to the vessel hull, problems not seen in T-foils may result and a pre-pitched foil mounting can be provided to avoid requiring significant and constant control input when underway at operating/cruising speeds in flat water. While there may be various modifications and permutations of the angle and mounting, if the foil were mounted flat the localized flow would create lift at cruising speed that would need to be counteracted by the control flap 4 to maintain equilibrium, thus the need for control input at cruising speed is reduced by mounting the foil at an angle relative to the running trim of the vessel.

The lower surface 7 of the foil is relatively close to the level of the keel of the vessel. In the embodiment shown, the lower surface is actually flush with the keel, more particularly, the keel 9 is the lowest point of the keel and the foil 3 is mounted in a break/recess of the keel. In this manner the extended keel line where the keel would otherwise be if not for the recess is approximately level with the lowest point of the lower surface 7 (for example, within several inches or less). This is best shown in FIG. 5 where the extended keel line 16 is depicted as a dashed line. Depending on the shape of the vessel and particularly the keel shape, this line 16 may be flat or may have a curved shape. Therefore, with the lowest point of the foil 3 flush with the keel, the upper surface 12 of the foil 3 is above this keel line. This arrangement is a departure of common T-foils as explained previously in that most bow foils and T-foils are mounted on a strut which moves the foil below the vessel hull. While such a mounting may allow the foil to operate free of disturbance of the vessel hull (e.g. water flow variations due to the hull), this strut mounting can increase the draft of the vessel. As can be seen, the foil 3 is designed with a foil shape, typically a NACA (National Advisory Committee for Aeronautics) foil or a shape derived from a NACA foil design. This generally teardrop or streamlined shape will often be a symmetrical foil in the present design in that the top and bottom shapes (above/below chord) are designed to be the same.

The foil cross section is typically designed from a symmetrical cross section, symmetrical about the chord line, usually a NACA foil shape. When manufactured, the foil is substantially symmetrical in its cross section in that manufacturing tolerances may result in a foil that is not perfectly symmetrical. The flap 4 at the back of the foil changes the effective shape of the overall combination of the foil and flap such that this variation in effective shape creates lift. When the flap is neutral it is preferred that the lift generated by the foil be minimized.

As shown in FIG. 5, the lower most point of the foil 14 is preferable at or above the extended keel line 16. Furthermore, the vessel includes a cutout 18 which allows for the foil's control flap 4 to pivot up without interference. FIG. 6 shows the range of motion 20 of the control flap 4 and the chord line 22 of the foil. Referring to FIG. 7, the structural components of the foil are shown. Namely spar 86 extends along the span of the foil and provides significant bending resistance and ribs 84 are spaced along the spar. Leading edge 6 is smooth and rounded. Furthermore, mounting plate 82 is provided with several through holes 80 which allow bolts to attach the foil to the vessel at the keel area of the vessel. The bolts used are preferably of a strength which causes the foil to break away before forces on the foil bend the structure of the vessel. Referring to FIG. 8, an exemplary vessel 2 is shown with the foil 3 mounted in the forward area of the vessel, close to the bulbous bow 1. Preferably the present foil 3 is mounted in the forward half, more preferably in the forward 40% or more preferably forward 30% of the vessel length.

Referring to FIGS. 9-11, exemplary internal structure of the vessel 2 is shown, namely support plates 98, 99 and 100 are arranged to create a gap in the keel area and support structure for the foil. Ribs 101 and plates 101′ are provided in the vessel and create a space in the keel area for the foil and its mounting plate 82. As shown, the space in the keel area is wider at the keel than above in that the foil is larger at its chord than at the mounting plate 82. A piston 96 is provided with a rod 102 connected at rod end 94 to tab 92 on the control flap 4 of the foil. The piston 96 forces the rod 102 in and out to control the flap. This control flap 4 rotates about pivot/hinge 90. The piston 96 is controlled by a controller to counteract pitch forces and/or to trim the vessel. As shown in FIG. 10, the vessel includes fairings 104, 106 that close the space provided for mounting the stabilizer. These fairings provide a smooth transition between the vessel hull and the foil. The rear fairing 106 however is provided with enough space to allow for the notch such that the control flap 4 can rotate through the necessary range of motion 20. The interior sides of the fairings 106/104 can be seen in FIG. 11.

FIG. 12 shows an exemplary control system for the vessel. The controller 1202 may be a dedicated computer or part of the ship's computer or other processor/computing device which has software 1201 thereon. The software will receive data from sensors 1200 which may include pitch and roll data, sea state data, throttle/power data, weather data and various other sensor data which would be useful to the control system's determination of control instructions. The controller may allow for various settings for desired control outcomes and may also allow for manual trimming/intervention. For example, the extent to which pitch fluctuations are removed by control may be set as an input to the controller. For example, the most active control (e.g. the one designed to eliminate as much pitching as possible) would be expected to also cause the largest increase in drag, and this may not be desirable in some cases, depending on the needs of the crew and passengers at the time. Thus, a more moderate control scheme to reduce pitch may also be expected to cause less overall increase in drag in comparison. Such inputs/selections may be user selectable. Furthermore, depending on how rough the water is, certain levels of control may not be available. For example, if the controller is attempting to reduce pitch, this will result in the foil pushing the bow down into wave crests and up into valleys which may be undesirable if the waves are too large. The control instructions 1210 are sent to the various stabilizers 1206, 1208, 3 as shown. These foils may send back confirmations 1211 and/or other data to confirm implementation of the control instructions. In the case of the bow foil 3, these control instructions will manipulate the piston 96 to adjust the control flap 4.

There are no limitations in terms of the particular embodiments described in this application, which are intended as illustrations of various aspects only. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and apparatuses, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and variations are intended to fall within the scope of the appended claims. Only the terms of the appended claims are intended to be limiting, along with the full scope of equivalents to which such claims are entitled. It is also to be understood that the terminology used herein, e.g., “and”, “or”, “including”, “at least” as well as the use of plural or singular forms, etc., is for the purpose of describing examples of embodiments and is not intended to be limiting.

Claims

1. A stabilizer foil for a vessel comprising: a foil which is configured to articulate based on one or more control inputs to generate a control force, the foil having a lower surface, an upper surface and a maximum foil thickness;the foil is configured to attach to the vessel in a fixed position such that a lowest point of the lower surface is positioned less than three times the maximum thickness below a keel of the vessel in an area adjacent to the foil.

2. The stabilizer foil of claim 1 wherein the lowest point is positioned less than three times the maximum thickness above the keel of the vessel in the area adjacent the foil.

3. The stabilizer foil of claim 1 wherein the foil is configured to be mounted in the fixed position at least partially in a recess of the hull, the recess located in a forward portion of the vessel.

4. The stabilizer foil of claim 3 wherein the recess is in the keel and the lowest point of the lower surface is even with an extended keel line at the recess and a flap of the foil is configured to rotate at least partially into the recess.

5. The stabilizer foil of claim 1 wherein the foil includes a mounting area comprising holes therethrough and bolts are configured to pass through the holes and into holes in keel support structure of the vessel.

6. The stabilizer of claim 1 wherein the foil articulates by a flap of the foil rotating to generate the control force.

7. The stabilizer of claim 1 wherein port and starboard sides of the foil share a common center plane.

8. A stabilizer foil for a vessel comprising: a foil having a flap which is configured to articulate relative to the foil based on one or more control inputs;the foil configured to mount to a bow area of the vessel in a fixed position such that a chord line of the foil is positioned at a non-zero angle relative to a running trim of the vessel.

9. The stabilizer foil of claim 8 wherein the non-zero angle is at least 3 degrees.

10. The stabilizer foil of claim 8 wherein the foil has a substantially symmetrical cross section.

11. The stabilizer of claim 8 wherein port and starboard sides of the foil share a common center plane.

12. The stabilizer of claim 8 wherein the foil is configured to attach to the vessel such that a lowest point of a lower surface of the foil is positioned less than three times the maximum thickness below a keel of the vessel in an area adjacent to the foil.

13. The stabilizer foil of claim 12 wherein the lowest point is positioned less than three times the maximum thickness above the keel of the vessel in the area adjacent the foil.

14. The stabilizer foil of claim 8 wherein the running trim is determined based on a predefined speed and weight distribution in ideal conditions.

15. A stabilizer foil for a vessel comprising: a foil system mounted in a bow area of the vessel and including foil sections which extend outwards on port and starboard sides of the vessel and the foil sections have a maximum foil thickness;the vessel comprising a lowest point of the vessel which lowest point of the vessel is a point on the vessel other than on the foil sections;a lowest point of the foil sections is no more than three times the maximum foil thickness below the lowest point of the vessel.

16. The stabilizer foil of claim 15 wherein the lowest point of the foil sections is at or above the lowest point of the vessel.

17. The stabilizer of claim 15 wherein foil sections of the foil system share a common center plane.

18. The stabilizer of claim 15 wherein a highest point of the foil sections is no more than three times the maximum foil thickness above a lowest point of a keel of the vessel.

19. The stabilizer of claim 18 wherein foil sections of the foil system share a common center plane.

20. The stabilizer of claim 1 wherein the foil includes a flap which is articulated based on one or more control inputs to cause the flap to rotate to generate a control force.