US20120285354A1

US20120285354A1 - Adjusting rigid foil spar system

Info

Publication number: US20120285354A1
Application number: US13/180,622
Authority: US
Inventors: John Garrison Hoyt
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-05-09
Filing date: 2011-07-12
Publication date: 2012-11-15

Abstract

A rigid foil sail having a full length vertical leading edge whose trim angle/angle of attack is controlled by the main sheet and at least two trailing edge flaps attached rearwardly of the leading edge, each of which can be independently trimmed from a convenient deck level control tray to achieve easily adjustable camber. The design of the rigid foil sail allows depowering of the sail without altering mainsheet trim by decreasing the camber of the upper trailing flap thus also decreasing the heeling force created by the power of the upper trailing flap. Such an arrangement allows the boat to be driven without the loss of upwind pointing performance and without the loss of power caused by luffing of the sail. Similarly, the boat can be better balanced by allowing the boat to be driven to windward more efficiently with a minimum heel angle.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and claims priority from earlier filed U.S. Provisional Patent Application No. 61/483,996, filed May 9, 2011, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to rigid foil sails for boats. More specifically, the present invention relates to a rigid foil sail system for boats that has independently controllable sections that allow optimum control over the lift force generated by the soil in varying wind conditions and directions.
Although the appearance of the conventional sail is quite different from that of an aircraft wing, its function in generating a positive force is based on the same aerodynamic principles as those applied to a wing. The sail, however, is considerably the less efficient foil of the two partly because the sail utilizes a single surface air foil as opposed to the more efficient double surface air foil of the wing. Another factor that reduces the efficiency of a conventional sail is that its external bracing, mast and rigging disturb the flow of air around its surface, resulting in an energy loss to turbulence and drag.
Despite its much greater efficiency, a standard wing does not make a good sail when mounted in a vertical position so that the lift that it generates can be used as thrust to drive a boat or vehicle. This is because of the shape of the wing and the fact that in use wind is directed against both sides of the wing at various angles. In this regard, it should be appreciated as the wind approaches a conventional wing at a positive angle of attack from what was its bottom surface, the wing will produce good results and significantly improve the efficiency over the conventional sail. But when the wind is directed from a direction where the same impinges on the upper surface of a conventional wing, its efficiency drops well below that of the sail.
Consequently, it follows that in order to provide an all around efficient wing for “sailing purposes”, it would be desirable to design the same to have a changeable air foil, or variable camber. This would enable the wing to have the high efficiency referred to with the wind approaching the same from either side. It should be noted that the provision of a variable camber wing for a vessel has been provided in the past. A close review of the prior art in this area reveals that the design and construction of such variable camber wings have been complex and in fact impractical when considered on a commercial production basis. However, because of the increases in efficiency achieved by such a variable camber wing, it is highly desirable that a relatively simple and easy to use design be provided that lends itself to commercial production.
Such rigid sail designs have been created for use on specialty boats usually intended for racing events as is known, with rigid sails commonly called wing sails on account of their sectional profile duplicating basically that of an airplane wing. It has been observed that this type of sail can improve the aerodynamic qualities of a sailboat and afford higher cruising speeds to be attained and maintained. It has, however, a fault in that it is difficult to handle and troublesome to lower.
This prior approach, while substantially achieving its objective, still has some shortcomings as pointed out below. In the first place, sail area cannot be reduced, or the sail be reefed down, in a continuous fashion. Further, the airfoil shape of the sail can only be achieved effectively with the various segments fully extended vertically. Further shortcomings originate from the excessively complicated construction of the sail, which is also the cause for high cost and low reliability. Finally, such sail arrangements are generally heavy. Should the vessel overturn the prior art rigid sails risk filling with water, compromising both the floatation of the sail and the boat.
There is therefore a need for a rigid foil sail that has adjustable camber that is also capable of being detuned to allow its use in heavier wind conditions. There is a further need for a self-supporting rigid foil sail that includes adjustable camber to increase or decrease the power generated by the foil shape. The is still a further need for a rigid foil sail that includes at least two adjustable trailing sections to allow independent adjustment of the sail camber.

BRIEF SUMMARY OF THE INVENTION

In this regard, the present invention provides for a three dimensional rigid foil sail design. As such, the general purpose of the present invention, which will be described subsequently in greater detail, is to provide at least a three part rigid foil sail having a full length vertical leading edge whose trim angle/angle of attack is controlled by the main sheet and at least two trailing edge flaps attached rearwardly of the leading edge, each of which can be independently trimmed from a convenient deck level control tray to achieve easily adjustable camber.
The design of the rigid foil sail of the present invention allows depowering of the sail without altering mainsheet trim by decreasing the camber of the upper trailing flap thus also decreasing the heeling force created by the power of the upper trailing flap. Such an arrangement allows the boat to be driven without the loss of upwind pointing performance and without the loss of power caused by lulling of the sail. Similarly, the boat can be better balanced by trimming the lower trailing flap for optimum performance and simultaneously trimming the upper trailing flap neutral or even to leeward to create an opposing force that will counter the heeling moment of the sail allowing the boat to be driven to windward more efficiently with a minimum heel angle.
Therefore, it is an object of the present invention to provide a rigid foil sail that has adjustable camber that is also capable of being detuned to allow its use in heavier wind conditions. It is a further object of the present invention to provide a self-supporting rigid foil sail that includes adjustable camber to increase or decrease the power generated by the foil shape. It is still a further object of the present invention to provide a rigid foil sail that includes at least two adjustable trailing sections to allow independent adjustment of the sail camber in a manner that better balances the boat without compromising upwind pointing performance.
These together with other objects of the invention, along with various features of novelty which characterize the invention, are pointed out with particularity in the claims annexed hereto and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings which illustrate the best mode presently contemplated for carrying out the present invention:

FIG. 1 is a perspective view of a boat with a rigid foil sail in accordance with the present disclosure;

FIG. 2 is an exploded vies of the rigid foil sail of the present disclosure;

FIG. 3 is a diagrammatic plan view of the rigid foil sail depicting the various positions of the trailing flaps;

FIG. 4 depicts the relative position of the rigid foil sail when sailing up wind and the forces that result;

FIG. 5 depicts the rigid foil sail in a downwind sailing configuration; and

FIG. 6 depicts the rigid foil sail in an upwind sailing configuration.

DETAILED DESCRIPTION OF THE INVENTION

Now referring to the drawings, the three dimensional rigid foil sail design is generally shown and illustrated at 10. As can be seen at FIG. 1, the present invention generally provides at least a three part rigid foil sail 10 having a full length vertical leading edge 12 whose trim angle/angle of attack is controlled by the main sheet and at least two trailing edge flaps 14, 16 attached rearwardly of the leading edge 12, each of which can be independently trimmed from a convenient deck level control tray to achieve easily adjustable camber. Further, the rigid foil sail 10 can be seen to include control trays 18 at the bottom of each of the trailing edge flaps 14 and 16 that allow independent adjustment of the camber for each section of the rigid foil sail 10 independently of one another.
It can be seen from FIG. 1 that the rigid foil sad 10 provides a squared geometry as compared to the prior art sails. Such squared geometry can be achieved due to the rigid nature of the construction of the rigid foil sail. Such a squared geometry is more efficient in that the sail does not need to be triangular to get the necessary support in order to maintain trim. As can best be seen at FIG. 2, the entire rigid foil sail is received and supported by a rotating mast 20. It should be noted that the mast 20 may be rigidly affixed to the leading edge 12 such that they rotate as a single unit or the leading edge 12 may rotate about the mast 20. The mast 20 serves to support the entire rigid foil sail 10 in a freestanding, aerodynamically clean manner. The freestanding mast 20 arrangement eliminates the needs for side, fore and aft stays as were required in the prior art thereby reducing the aerodynamic drag typically generated in such conventional sailing rigs. To further increase the efficiency of the rigid foil sail, a top winglet 28 can be seen. Such a winglet 28 prevents the formation of a wing tip vortex as the high pressure (windward) air spills across the top of the foil to the lower pressure (leeward) side of the rigid foil. In this manner, the winglet serves to increase the efficiency of the upper portion of the rig thereby allowing a reduction in overall size of the rigid foil sail 10.
The mast 20 can be seen to support the leading edge 12 of the rigid foil sail. The leading edge 12 is preferably a symmetrical two sided airfoil. The mast 20 can be seen positioned slightly aft of the leading edge 12. This creates a semi-balanced rig arrangement that allows a forward positioning of the rigid foil rig 10 as well as a reduction in the dynamic forces generated when the sail changes sides of the boat during a maneuver such as a tack or jibe. This forward position of the rig means that jibing can be accomplished with no danger of the boom hitting the skipper during the jibe as was a risk in the prior art with full extension booms over the length of the cockpit. Still further, due to the shortened overall length of the rig and its balanced nature, the rig automatically weathercocks (turns its leading edge into the wind) when at rest allowing the boat to be docked and stored with the rig remaining in the boat. This is to be contrasted with prior art rigid foil arrangements that require removal of the rig each time the boat is docked.
The rear of the leading edge 12 includes recesses 22 that in turn receive the forward ends of the trailing edge flaps 14, 16 in a smooth and aerodynamically efficient manner while also allowing the trailing edge flaps 14, 16 the freedom to rotate as will be further discussed below. The trailing edge flaps are received and supported about a pivot or shaft 14 that firmly retains the trailing edge flaps 14, 16 yet allows them rotational movement.
As can best be seen in FIG. 3, the trailing edge flaps 14, 16 have a rotational range of motion that allows the trailing edge flaps 14, 16 to be adjusted relative to the leading edge 12 from a neutral position as depicted at 26 a to a positive camber position 26 b relative to the prevailing wind direction and a negative camber direction 26 c relative to the wind direction. This allows the lift force of the rigid foil sail to be fully adjusted from a maximum power position having a high positive camber to a neutral power position to still further a negative lift position having negative camber. Further, the sail components are formed from a rigid, moldable material that is highly durable creating a permanent sail that never needs replacement. The components may be formed from any molded material known in the boat building art. Most preferably the components are formed from a carbon fiber composite material. These molded components also are hollow thereby trapping air pockets therein which in turn provides positive floatation should the boat capsize. This positive flotation in turn prevents the rig from fully inverting in the water in the event of capsize.
Returning now to FIG. 1, the rigid foil sail 10 can be easily controlled using only three lines that are routed through fairleads to a convenient position that is accessible by the skipper of the boat. The first line is the traditional main sheet 30. The main sheet 30 controls the overall rotation of the entire rigid foil sail 10 relative to the boat as it rotates around the mast 20. Adjustment of the main sheet 30 serves to adjust the angle of attack of the entire rigid foil sail 10 relative to the wind direction. An upper control line 32 serves to control the camber of the upper trailing flap 14 relative to the leading edge 12 as between a neutral position 26 a, a positive camber position 26 b and a negative camber position 26 c to increase, decrease or generate negative lift respectively. The upper control line preferably runs from both the port and starboard sides of the upper trailing flap 14, through the upper control tray 18 and then through fairleads to allow symmetrical control of the upper trailing flap depending on which jibe or tack the boat is travelling. Similarly, a lower control line 34 serves to control the camber of the lower trailing flap 16 relative to the leading edge 12 as between a neutral position 26 a, a positive camber position 26 b and a negative camber position 26 c to increase, decrease or generate negative lift respectively. The lower control line 34 preferably runs from both the port and starboard sides of the lower trailing flap 16, to the lower control tray 18 and then through fairleads to allow symmetrical control of the upper trailing flap depending on which jibe or tack the boat is travelling.
Turning to FIG. 4 the arrangement of the rigid foil sail 10 of the present invention allows a great deal of flexibility over the power generated by the sail. This allows the skipper of the boat to effectively reef the boat by depowering the sail without ever leaving his seated position at the helm. As can be appreciated, the power of the sail can be adjusted without ever adjusting the main sheet 30 or changing the angle of attack of the sail. In FIG. 4, the foil is shown with the same angle of attach relative to the wind direction. However, position 26 a depicts a neutral camber generating little to no lift, position 26 b shows positive camber resulting in greater positive lift forces and in turn heeling moments applied to the boat and position 26 c shows negative camber with a resulting negative lift and a reduction in heeling forces. In this manner, a skipper can balance the positioning of the upper and lower trailing flaps 14, 16 to balance the pointing ability of the boat, the power generated by the rigid foil sail 10 and the overall heeling force on the boat. In this manner, the rigid foil sail 10 can be de-powered without altering the trim of the mainsheet 30. Simply easing the control line 32 of the upper flap removes the camber and thus the heeling force of the upper flap. This means that the lower rear flap can continue to provide drive and pointing ability without the loss of power incurred by the normal process of luffing the sail to counter heeling. Similarly, the camber created by trimming the lower flap to windward provides forward drive plus a substantial heeling force. By trimming the upper flap to the opposite side of the upper tray control panel an opposing lift force is created that will have the effect of countering the heeling moment created by the camber of the lower flap. This means a sailboat can be driven to windward more efficiently-with minimum heeling. One skilled in the art will also appreciate that more precise “twist” control is obtained by completely separating upper sail camber from lower sail camber, enabling adjustment for greater wind velocity aloft. Previously these adjustments required the adjustment of a boom yang, a Cunningham, a down haul, an outhaul and backstay tension. Notably, the present invention eliminates the need for all of the above noted controls as well as halyards, running rigging and battens.
FIGS. 5 and 6 are provided to show additional context for the present invention wherein FIG. 5 depicts the rigid foil sail positioned for downwind sailing of the boat and FIG. 6 depicts a reaching configuration.
One skilled in the art should appreciate that the structures shown herein can be duplicated in a vertical fashion to employ two, three or more trailing edge flaps and respective controls arranged in a vertical fashion. Further, such a rigid foil sail may be placed in duplication forward and rear of one another or side to side relative to one another without departing from the spirit and scope of the invention.
It can therefore be seen that the present invention provides a rigid foil sail that has adjustable camber that is also capable of being detuned to allow its use in heavier wind conditions. Further the present invention provides a self-supporting rigid foil sail that includes adjustable camber to increase or decrease the power generated by the foil shape and includes at least two adjustable trailing sections to allow independent adjustment of the sail camber in a manner that better balances the boat without compromising upwind pointing performance. For these reasons, the instant invention is believed to represent a significant advancement in the art, which has substantial commercial merit.
While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.

Claims

1. A rigid foil sail comprising:

a free-standing rotatable mast;

a leading edge having a symmetrical airfoil shape supported by said mast;

a lower control tray affixed to said mast proximate a bottom edge of said leading edge;

at least one additional control tray affixed to said mast in spaced apart vertical relation to said lower control tray;

a lower trailing edge flap rotatably supported between said lower control tray and said at least one additional control tray adjacent a rear edge of said leading edge; and

at least one upper trailing edge flap rotatably supported above said additional control tray adjacent a rear edge of said leading edge.

2. The rigid foil sail of claim 1, further comprising:

a main sheet for controlling rotation of said mast.

3. The rigid foil sail of claim 2, wherein said main sheet is affixed to a bottom surface of said lower control tray proximate a rear end thereof.

4. The rigid foil sail of claim 1, further comprising:

a lower control to control rotation of said lower trailing edge flap relative to said leading edge; and

an upper control to control rotation of said upper trailing edge flap relative to said leading edge.

5. The rigid foil sail of claim 4, wherein said lower control and upper control are operated independent of one another.

6. The rigid foil sail of claim 4, wherein said upper control and lower control are run through fair leads to a single control location.

7. The rigid foil sail of claim 1, wherein said rear edge of said leading edge includes a recess therein to receive a forward edge of said lower and at least on upper trailing edge flaps.

8. The rigid foil sail of claim 1, wherein a portion of said leading edge extends forward of said mast thereby creating a semi-balanced sail.

9. The rigid foil sail of claim 1, further comprising:

a winglet affixed to said mast in spaced apart vertical relation to said at least one additional control tray and adjacent said at least one upper trailing edge flap.

10. The rigid foil sail of claim 1, wherein said leading edge, lower trailing edge flap and at least one upper trailing edge flap are formed of rigid material.

11. The rigid foil sail of claim 1, wherein said lower trailing edge flap and said at least one upper trialing edge flap are rotatably adjustable independent of one another and relative to said leading edge to a range of negative camber, neutral and positive camber positions, wherein said negative camber positions generate a lift force to a windward direction relative to the sail and said positive camber positions generate a lift force to a leeward direction relative to the sail.