WO1997015488A2

WO1997015488A2 - Propeller foil

Info

Publication number: WO1997015488A2
Application number: PCT/IL1996/000132
Authority: WO
Inventors: Amiram Steinberg
Original assignee: Steinberg, Gal; Steinberg, Hadar
Priority date: 1995-10-25
Filing date: 1996-10-25
Publication date: 1997-05-01
Also published as: IL115768A0; WO1997015488A3; AU7330496A

Abstract

This invention discloses an elevation foil mounted on a watercraft, wherein at least a portion of the elevation foil is located in the projected disk area of a propeller of the watercraft. A method for the stabilization of the orientation of a watercraft propeller with respect to the water is also disclosed.

Description

PROPELLER FOIL

The present invention relates to apparatus and methods for stabilization of watercraft, particularly of stabilization of the orientation of watercraft propellers with respect to the water surface, and for providing lift to the watercraft.

Many watercraft are driven by one or more propellers. The propeller is usually mounted on a propel¬ ler shaft cone of a controllable stern drive unit of an inboard or outboard engine. As is known in the art, the efficiency of a propeller depends, inter alia, upon the orientation of the propeller with respect to the water surface. The propeller has what is known as a designed waterline, that is, a design goal of an optimum amount of submersion into the water.

A fully submerged propeller operates with its entire diameter under the water surface at a certain preferred depth. A surface propeller operates with cer¬ tain portions thereof partially immersed in the water. Usually up to half of the propeller diameter is above the water. Deviations from the desired orientation of the propeller detrimentally affect the efficiency of the propeller.

Designers and manufacturers invest much time and effort to maintain the designed orientation of the propeller with respect to the water surface. However, the impact of waves on watercraft usually causes such severe pitching and heaving that the propeller deviates from the optimum orientation with respect to the water for a large part of the operating time.

The present invention seeks to provide improved apparatus and methods for stabilization of watercraft, particularly of stabilization of the orientation of watercraft propellers with respect to the water surface. and for providing lift to the watercraft.

It is noted that throughout the specification and the claims, the term propeller refers to any type of propulsion device, such as, for example, a propeller, fixed shaft propeller, Arneson drive, water jet or other propulsion device.

In accordance with a preferred embodiment of the present invention, an elevation foil is provided, which is at least partially located in the projected disk area of a propeller of a watercraft. Preferably, the elevation foil is mounted on a shaft cone of the propel¬ ler. The elevation foil may jut generally horizontally outwards from the shaft cone, or alternatively, may have an upward or downward dihedral angle.

It is noted that the "projected" disk area of the propeller refers to an imaginary infinitely long prism whose longitudinal axis is the axis of the propel¬ ler shaft and whose cross sectional area is the cross sectional area of the propeller.

In accordance with a preferred embodiment of the present invention, the underside of the propeller shaft cone is shaped like a hull with a planing surface and with an extended chine characterized by a large flare. Alternatively, the chine may be formed at the junction of the propeller shaft cone and the elevation foil, and may extend beyond this junction.

The designed waterline is such that the water is directed to flow under the planing surface with flow lines moving generally backwards and outwards only. The water is substantially prevented from flowing onto the upper surface of the cone due to the deflecting action of the extended flared chine. In many cases, the upper surfaces of the propeller shaft cone and the surfaces of structure which connects the cone to the underside of the watercraft are not in the way of the water flow and do not contribute to the overall drag. The chine thus helps increase the lift-to-drag ratio of the craft by causing water to flow under the cone, thereby increasing lift, and by substantially preventing water from flowing above the cone, thereby reducing cone drag. The hull shaped cone with planing surface also increases the lift-to-drag ratio of the cone in particular, and of the craft in general.

The elevation foil may be located so as to achieve the design waterline for either full submersion or partial submersion.

When the watercraft is in rough waters , the stern starts plunging deeper into the water, thereby causing water to completely cover a large portion of the elevation foil. The submerged elevation foil provides a large lifting force in excess of the balance of forces and moments exerted on the hull in its steady state cruise, and thus causes the aft portion of the hull to swing back relatively quickly to the desired elevation determined by the elevation foil position. Moreover, the hull swings back to the desired elevation without any substantial overswing. The deeper the immersion, the larger the portion of the foil area is operational and the greater the lift which is generated.

The elevation foil thus helps to stabilize the craft, such as against rolling, pitching and heaving, and to automatically maintain the desired waterline elevation of the propeller. The elevation foil helps to reduce the sensitivity of change of the trim angle with respect to the waterline. High propeller efficiency is maintained for a longer duration than the prior art.

Fences may be added to the elevation foil. The fences effectively separate the foil area into flow sections and prevent the flow from creeping from one section to another. This helps maintain more orderly flow across the foil.

The fences may be positioned with a slight angle between the fence surface and the longitudinal direction of flow. The slight angle deflects the flow of water as it leaves the aft portion of the underside of the elevation foil, and directs the flow into the propel¬ ler disk area. The propeller blade meets the deflected water flow in an improved angle of attack, thus increas¬ ing the propeller efficiency. This is a similar effect to the action of a counter-rotating pair of propellers used in some drives, in which the wake of a leading propeller is met by a trailing propeller rotating in an opposite direction.

A highly efficient fully submerged, lower foil may be added to achieve the desired total amount of lift along with minimum drag. The lower foil may also be provided with fences.

During cruising, the elevation foil is general¬ ly out of the water and the lower foil generally provides sufficient lift and stabilization of the watercraft and the propeller. During high waves, the elevation foil becomes from time to time at least partially submerged and generally provides the lifting and stabilizing forces required in excess of that of the lower foil.

There is thus provided in accordance with a preferred embodiment of the present invention, an eleva¬ tion foil mounted on a watercraft, wherein at least a portion of the elevation foil is located in the projected disk area of a propeller of the watercraft.

In accordance with a preferred embodiment of the present invention, the elevation foil is mounted on a shaft cone of the propeller.

In accordance with a preferred embodiment of the present invention, the elevation foil when forced to submerge in water provides an excessive lifting force sufficient to substantially regain the desired orienta¬ tion of the propeller with respect to the water.

In accordance with a preferred embodiment of the present invention, the elevation foil juts generally horizontally outwards. Alternatively, the elevation foil may be angled with respect to the horizontal.

In accordance with a preferred embodiment of the present invention, the elevation foil is located so as to achieve a design waterline for full submersion of the propeller.

Alternatively, in accordance with another preferred embodiment of the present invention, the eleva¬ tion foil is located so as to achieve a design waterline for partial submersion of the propeller.

In accordance with a preferred embodiment of the present invention, the shaft cone is shaped substan¬ tially like a hull with a planing surface.

In accordance with a preferred embodiment of the present invention, there is provided an extended chine at a junction of the shaft cone and the elevation foil. Preferably, the chine is characterized by a rela¬ tively large flare.

Additionally in accordance with a preferred embodiment of the present invention, the cone and the chine are shaped such that during cruising, water is substantially restricted to flow along a surface of the cone below the chine.

In accordance with a preferred embodiment of the present invention, the elevation foil includes at least one fence.

Additionally in accordance with a preferred embodiment of the present invention, the at least one fence is positioned with an angle between a fence surface and a longitudinal direction of flow of water.

Further in accordance with a preferred embodi¬ ment of the present invention, the at least one fence is adapted to deflect a flow of water flowing from an aft portion of an underside of the elevation foil into the propeller disk area. Still further in accordance with a preferred embodiment of the present invention, there is provided at least one secondary foil located outside of the projected disk area of the propeller. The second foil may have an upward or downward dihedral angle.

There is also provided in accordance with a preferred embodiment of the present invention, a method of stabilization of the orientation of watercraft propel¬ lers with respect to the water surface, including provid¬ ing an elevation foil which provides a lifting force sufficient to substantially attain a desired orientation of the propeller with respect to the water.

In accordance with a preferred embodiment of the present invention, the method includes locating at least a portion of the elevation foil in the projected disk area of the propeller.

In accordance with a preferred embodiment of the present invention, the method includes mounting the elevation foil on a shaft cone of the propeller.

Additionally in accordance with a preferred embodiment of the present invention, the method includes locating the elevation foil so as to achieve a design waterline for full submersion of the propeller.

Alternatively, in accordance with another preferred embodiment of the present invention, the method includes locating the elevation foil so as to achieve a design waterline for partial submersion of the propeller.

In accordance with a preferred embodiment of the present invention, the method includes providing an extended chine at a junction of the shaft cone and the elevation foil.

Further in accordance with a preferred embodi¬ ment of the present invention, the method includes shap¬ ing the shaft cone substantially like a hull with a planing surface.

In accordance with a preferred embodiment of the present invention, the method includes providing the elevation foil with at least one fence.

Additionally in accordance with a preferred embodiment of the present invention, the method includes using the at least one fence to deflect a flow of water flowing from an aft portion of an underside of the eleva¬ tion foil into the propeller disk area.

The present invention will be understood and appreciated from the following detailed description, taken in conjunction with the drawings in which:

Fig. 1 is a simplified pictorial illustration of an elevation foil constructed and operative in accord¬ ance with a preferred embodiment of the present inven¬ tion, as viewed from the stern and from above; and

Fig. 2 is a simplified pictorial illustration of the elevation foil of Fig. 1, as viewed from the bow and from below.

Reference is now made to Figs. 1 and 2 which illustrate an elevation foil 10 constructed and operative in accordance with a preferred embodiment of the present invention.

In accordance with a preferred embodiment of the present invention, elevation foil 10 is located at least partially in the projected disk area 12 of a pro¬ peller lk of a watercraft 15 (partially shown). Elevation foil 10 is preferably mounted on a propeller shaft cone 16 of propeller 14. Elevation foil 10 may jut generally horizontally outwards, or alternatively, may be have an upward or downward dihedral angle.

In accordance with a preferred embodiment of the present invention, the underside of shaft cone 16 is shaped like a hull with a planing surface 18. In accord¬ ance with a preferred embodiment of the present inven¬ tion, shaft cone 16 is formed with an extended chine 20. In the illustrated embodiment, chine 20 is formed at the junction of shaft cone 16 and elevation foil 10. It is appreciated that alternatively, shaft cone 16 may be formed with chine 20 without the elevation foil 10. Preferably extended chine 20 is characterized by a rela¬ tively large flare. Chine 20 may extend beyond the junc¬ tion of shaft cone 16 and elevation foil 10.

Propeller lk preferably has a designed water- line such that the water is directed to flow under plan¬ ing surface 18 with flow lines moving generally backwards and outwards only. The water is substantially prevented from flowing onto the upper surface of shaft cone 16 due to the deflecting action of extended flared chine 20. Upper surfaces 22 of shaft cone 16 and surfaces of a structure 2k which connects shaft cone 16 to a transom 25 of watercraft 15 generally do not interfere with the water flow and do not contribute to the overall drag.

Chine 20 thus helps increase the lift-to-drag ratio of watercraft 15 by causing water to flow under shaft cone 16, thereby increasing lift, and by substan¬ tially preventing water from flowing above shaft cone 16, thereby reducing drag. The hull shaped shaft cone 16 with planing surface 18 also increases the lift-to-drag ratio.

Elevation foil 10 may be located so as to achieve the design waterline for either full submersion or partial submersion.

When watercraft 15 is in rough waters, transom 2 and the rest of the stern (not shown) start plunging deeper into the water, thereby causing water to complete¬ ly cover elevation foil 10. The submerged elevation foil 10 provides a large lifting force in excess of the bal¬ ance of forces and moments exerted on the hull (not hown) in its steady state cruise, and thus causes the aft portion of the hull to swing back relatively quickly to the desired elevation determined by the position of elevation foil 10. Moreover, the hull swings back to the desired elevation without any substantial overswing. The deeper the immersion, the more the area of elevation foil 10 is operational and the greater the lift generated.

Elevation foil 10 thus helps to stabilize watercraft 15 and to automatically maintain the desired waterline elevation of propeller l k . High propeller efficiency is maintained for a longer duration than the prior art.

In accordance with a preferred embodiment of the present invention, one or more fences 30 may be added to elevation foil 10, as shown in Figs. 1 and 2. Fences 30 effectively separate the area of elevation foil 10 into flow sections and prevent the flow from creeping from one section to another. This helps maintain more orderly flow across elevation foil 10.

Fences 30 may be positioned with a slight angle 32 between a line "ik along a fence surface 3 and the longitudinal direction of flow, indicated by reference numeral 38. The slight angle 32 deflects the flow of water as it leaves the aft portion of the underside of elevation foil 10, and directs the flow into the propel¬ ler disk area 12. Propeller l k meets the deflected water flow in an improved angle of attack, thus increasing the propeller efficiency. This is a similar effect to the action of a counter-rotating pair of propellers used in some drives, in which the wake of a leading propeller is met by a trailing propeller rotating in an opposite direction.

A highly efficient fully submerged, lower foil kO may be added to achieve the desired total amount of lift along with minimum drag. Lower foil kO may also be provided with fences k 2 .

During cruising, elevation foil 10 is generally out of the water and lower foil k O generally provides sufficient stabilization of watercraft 15 and propeller l k . During high waves, elevation foil 10 becomes at least partially submerged and generally provides the lifting and stabilizing forces required in addition to that of lower foil kO .

It is appreciated that various features of the invention which are, for clarity, described in the con¬ texts of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, de¬ scribed in the context of a single embodiment may also be provided separately or in any suitable subcombination.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention is defined only by the claims that follow:

Claims

1. An elevation foil mounted on a watercraft, wherein at least a portion of said elevation foil is located in the projected disk area of a propeller of said watercraft.

2. An elevation foil according to claim 1 wherein said elevation foil is mounted on a shaft cone of said propeller.

3. A shaft cone of a propeller of a watercraft comprising an underside shaped like a hull with a planing surface.

k . A shaft cone of a propeller of a watercraft comprising an extended chine.

5. An elevation foil according to claim 2 and also comprising an extended chine located at a junction of said shaft cone and said elevation foil.

6. An elevation foil according to claim 5 and wherein said shaft cone comprises an underside shaped like a hull with a planing surface.

7. Apparatus according to any of claims 4 - 6, and wherein said chine is characterized by a relatively large flare.

8. Apparatus according to any of claims k - 7. and wherein at least one of said shaft cone and said chine is shaped such that during cruising of said watercraft, water is substantially restricted to flow along a surface of said shaft cone below said chine. 9- Apparatus according to any of claims 4 - 8, and wherein at least one of said shaft cone and said chine is shaped so as to increase a lift-to-drag ratio of said watercraft.

10. An elevation foil according to any of claims 1, 2 and 5 ~ 9. wherein said elevation foil, when submerged in water, provides a lifting force sufficient to substan¬ tially attain a desired orientation of said propeller with respect to the water.

11. An elevation foil according to any of claims 1, 2 and 5 " 10, wherein said elevation foil has an upward dihedral angle.

12. An elevation foil according to any of claims 1, 2 and 5 " 10, wherein said elevation foil does not have an upward dihedral angle.

13- An elevation foil according to any of claims 1,

2 and 5 ~ 12, wherein said elevation foil is located so as to achieve a design waterline for full submersion of said propeller.

l k . An elevation foil according to any of claims 1,

2 and 5 ~ 12, wherein said elevation foil is located so as to achieve a design waterline for partial submersion of said propeller.

15- An elevation foil according to any of claims 1, 2 and 5 ~ 14, and comprising at least one fence.

16. An elevation foil according to claim 15, and wherein said at least one fence is positioned with an angle between a surface of said fence and a longitudinal direction of flow of water. 17. An elevation foil according to either of claims 15 and 16, and wherein said at least one fence is adapted to deflect a flow of water flowing from an aft portion of an underside of said elevation foil into said propeller disk area.

18. An elevation foil according to any of claims 1, 2 and 5 ~ 17 and also comprising at least one secondary foil located outside of said projected disk area of said propeller.

19. An elevation foil according to claim 18, where¬ in said at least one secondary foil has an upward dihe¬ dral angle.

20. An elevation foil according to claim 18, where¬ in said at least one secondary foil does not have an upward dihedral angle.

21. An elevation foil according to claim 18 and wherein said at least one secondary foil also comprises at least one fence.

22 . A method of stabilization of the orientation of a watercraft propeller with respect to the water, com¬ prising providing an elevation foil which provides a lifting force sufficient to substantially attain a de¬ sired orientation of said propeller with respect to the water.

23- A method according to claim 22 and further comprising locating at least a portion of said elevation foil in the projected disk area of said propeller.

2k . A method according to either of claims 22 and

23, and further comprising mounting said elevation foil on a shaft cone of said propeller.

25. A method according to any of claims 22 - 2k , and further comprising locating said elevation foil so as to achieve a design waterline for full submersion of said propeller.

26. A method according to any of claims 22 - 24, and further comprising locating said elevation foil so as to achieve a design waterline for partial submersion of said propeller.

27. A method according to any of claims 22 - 26, and further comprising providing said elevation foil with at least one fence.

28. A method according to claim 27. and further comprising using said at least one fence to deflect a flow of water flowing from an aft portion of an underside of the elevation foil into the propeller disk area.

29- A method of stabilization of the orientation of a propeller of a watercraft with respect to the water, comprising mounting said propeller on a shaft cone with an extended chine, wherein at least one of said shaft cone and said chine is shaped such that during cruising of said watercraft, water is substantially restricted to flow along a surface of said shaft cone below said chine.

30. A method of increasing the lift-to-drag ratio of a watercraft, comprising mounting a propeller of said watercraft on a shaft cone with an extended chine, where¬ in at least one of said shaft cone and said chine is shaped so as to increase a lift-to-drag ratio of said watercraft. 31. A method of increasing the lift-to-drag ratio of a watercraft, comprising mounting a propeller of said watercraft on a shaft cone, wherein said shaft cone is substantially like a hull with a planing surface.