Anti-Heeling Apparatus for Sailboats
An apparatus for a sailboat which can be used to oppose heeling caused by the wind on the sail. The apparatus includes hydrofoils which are substantially aligned with the leeway angle. In one embodiment, the hydrofoils can be withdrawn from holders and re-inserted or shifted in position when the boat tacks and the wind comes from the other side. In another embodiment, the hydrofoils can automatically assume a position substantially parallel to the leeway angle when the boat is sailing.
This application claims the benefit of U.S. Provisional Application 61/614,875 filed on Mar. 23, 2012.
OBJECTIVEThe apparatus provides a safe and stable means of increasing the sail area of a single or double-handed dinghy class sailboat by using an anti-heeling apparatus which is simple, effective and inexpensive. Meeting this objective will enhance the enjoyment of sailing games such as sailball or sailing frisbee and will result in faster and more exciting racing boats for young and old alike.
TECHNICAL FIELDSmall monohull sailing vessels and specifically dinghy class vessels and increasing the speed and stability of such vessels.
BACKGROUNDA sailboat cannot sail directly into the wind. The wind must come from one side of the boat or the other, or, in a special case, directly from behind. Since the wind usually hits the sail from the side, the boat heels to leeward. This causes some of the wind to spill over the top the sail thereby reducing the forward driving force of the sail. Also the sail area presented to the wind is less, reducing the force generated. In addition because the boat is tipped, the forward force generated by the sail is normally centered off to leeward and therefore often causes the boat's bow to try to turn into the wind. To counter this effect, the helmsman must pull on the tiller to adjust the rudder so the boat goes straight. This has a braking effect on the boat due to induced drag, additionally causing it go more slowly than if the mast were straight up.
In large monohulls, heeling is countered by using a heavy weight on the keel. The heavier the weight, the more upright the boat will be, but it will go more slowly because of the bigger keel, which increases the displacement and frictional drags of the hull. In monohulls with daggerboards or centerboards, the crew hikes out to windward to reduce heeling. However, as the wind speed increases, the crew reaches the limit on how far they can hike so the boat heels anyway.
In catamarans, the hulls are a large distance apart. This enables the crew to get farther out to windward to reduce heeling. Because the catamaran design produces greater anti-heeling force, it enables the use of taller masts and more sail area, which results in boats which go faster than monohulls. A tall mast also allows a smaller attack angle to the wind, similar to operation of long wings on gliders. In sailing, going at a smaller angle to the wind is called pointing up. When beating, boats which point higher will usually reach their destinations sooner. However, the catamaran design sometimes results in inconveniently wide boats. Also they are more difficult to tack.
An object is to provide an apparatus which facilitates anti-heeling so tall masts and large sail areas can be used, resulting in fast boats which can point high, thus performing comparably to catamarans.
SUMMARYIn one embodiment, a Sunfish® sailboat, shown in
When both hydrofoils are used for anti-heeling, the leeward one also lifts the hull toward the surface of the water, thereby reducing displacement and skin friction hull drags. The hydrofoils can be manually adjusted up and down to accommodate different wind and boat speeds and wind directions.
On the windward side of the boat, the hydrofoil is usually inserted for negative lift. On the leeward side the hydrofoil is usually set for positive lift. The hydrofoils provide forces which counter the heeling force of the wind on the sail.
If inwardly curved hydrofoils are used for both lift and leeway control such as on catamarans or trimarans, the flow of water around the hydrofoils which produces the hydrodynamic force to prevent sideslipping is interfered with by the flow which produces lift. Leeway control is provided by a daggerboard and lift by the hydrofoils.
When the boat comes about from starboard tack to port tack, the hydrofoil on the windward side of the boat, is partly withdrawn, rotated to the positive lift position and pushed back down, and the hydrofoil on the leeward side is changed from the positive to the negative position. This shifts the anti-heeling function from one side to the other.
The slots in the hydrofoil holders through which the hydrofoils pass are designed such that the slot the upper level of the holder allows the hydrofoil to be rotated without the hydrofoil being completely removed from the holder. This reduces the chances that the crew will accidentally drop the hydrofoil into the water. The slot in the lower level is designed so that the hydrofoil cannot accidentally transfer between the positive and negative lift positions. This functionality is enabled by having the center of rotation at the upper level, and the lower level is at a sufficient distance from the center of rotation so that the hydrofoil cannot shift from negative lift to positive or vice versa while it is immersed.
In other embodiments the hydrofoil holding assemblies automatically move the hydrofoils to an angle substantially parallel to the leeway angle as water flows across them. One such embodiment is shown in
The hydrofoils can be manually adjusted up and down to engage or disengage them from the water.
On the windward side of the boat, the hydrofoil attack angle is usually positioned for negative lift. On the leeward side the attack angle is usually set for positive lift. The leeway angle is set by a daggerboard, keel or centerboard.
When the boat comes about from starboard tack to port tack, the hydrofoil on the windward side of the boat is rotated to the positive lift position, and the hydrofoil on the leeward side is changed from the positive to the negative position.
This shifts the anti-heeling function from one side to the other. Since the hydrofoil holding assemblies can rotate in the plane of the deck, the water flowing past them forces them to assume the proper leeway angle.
A bar connects the two hydrofoil holders so that they are both at the same angle. This is necessary because since the hydrofoils are canted outward, drag generated at their outward extremities would cause them to deviate from the proper leeway angle. Since the rotational forces are equal but opposite on the two hydrofoils, the bar forces the two hydrofoils to be at the same leeway angle.
On a run, the two hydrofoils should be set to have the same attack angle, either positive or negative, or they can be withdrawn. The leeway angle is substantially zero, and the daggerboard is usually fully withdrawn. If both hydrofoils are set for positive lift, the boat will rise up, reducing the form and skin friction drags of the hull, which will cause the boat to go faster. For greater boat stability, the attack angles can both be negative.
An additional advantage is that as the wind increases, thereby increasing heeling force, the boat will speed up, and the hydrofoils will exert greater anti-heeling force. A similar effect occurs in monohulls with heavy keels in which the anti-heeling effect of the keel increases as the boat heels more in increasing winds; however, in that case the boat suffers loss of speed due to increased heeling angle, whereas using the apparatus, the boat stays upright as long as the increased boat speed equals the increased wind speed. If the change in boat speed lags the increased wind speed, additional righting moment can be generated by lowering curved hydrofoils or increasing attack angle of “L” shaped ones.
The Sunfish® is a single-handed sailboat approximately 14 feet long, manufactured by the Laser Performance Company located in Portsmouth, R.I.
Referring to
In
A typical holder is shown in
A view of the top level of a hydrofoil holder is shown in
The hydrofoil is the black area, 4-3, in
The bottom level, 5-1, of the hydrofoil holder is shown in
The apparent wind, 7a-1, VA, propels the boat forward at a velocity, 7a-2, VS. This produces a headwind, 7a-3, VHD. The true wind velocity is VT, 7a-4. When wind velocity is steady, the heeling component of the apparent wind must be balanced by a force produced by the daggerboard, 7a-5, in the opposite direction of the heeling force so the boat will be in equilibrium. This force is generated by the daggerboard operating at the leeway angle, λ, 7a-6. The leeway angle is the angle between the centerline of the boat, 7a-7 and the direction of travel, 7a-8. For optimal operation, the hydrofoils, 7a-9, must be substantially parallel to the leeway angle with respect to the centerline of the boat because otherwise when hydrofoils are curved outward, there is conflict between the flow of water which sets the leeway and the flow of water which produces lift.
The settings of the hydrofoils for starboard and port operation are shown in
In both figures the starboard foil generates negative lift and the port one positive lift.
In
As the boat moves forward, the foils must assume a lateral attack angle, the leeway angle, relative the direction of boat motion, which produces pressure differentials, 7c-7 and 7c-9, that produce a force, 7c-6, to balance the force of the wind, 7c-1.
Note that the on the starboard side the high and low pressures producing negative lift and leeway control are both on the same side of the foil, and a similar situation occurs on the port side.
However, examination of
Note that in
As illustrated in
Generally the leeway angle does not vary substantially with apparent wind angle and varies little with wind velocity so for any particular sailboat a fixed leeway angle used for the hydrofoils, though not perfect, will perform fairly well. For more ideal performance an embodiment which incorporates automatic leeway angle adjustment, as described later, can be used. For the Sunfish® embodiment with a large sail, the leeway angle varies +−15% over apparent wind angles from 65 to 25 degrees. At apparent wind angles of less than 65 degrees, heeling is not as great a problem so the hydrofoils generally can be pulled up, which reduces their drag.
Referring to
The starboard negative lift, 8-3, of the windward hydrofoil causes the boat to appear heavier than it is, which would result in slower speed due to increased displacement and skin friction drags. To overcome this effect the hydrofoil, 8-6, is submerged into the water, and produces a lifting force, 8-5. This force opposes the combined downward forces of the starboard hydrofoil, 8-3, the weight of the crew, 8-4, and the weight of the boat, 8-7. The buoyancy of the hull, 8-8, also opposes the downward forces. The hydrodynamic force, 8-9, is generated by the daggerboard leeway angle and equals the heeling force, 8-1. Leeway angle forces on the hydrofoils are minimal since the hydrofoils are set at the leeway angle.
The two hydrofoils are adjusted so the boat remains upright and floats high enough in the water for optimum speed while maintaining stability.
When the boat goes on port tack, the hydrofoils, 8-2 and 8-6, are retracted, rotated and reinserted in their holders so their attack angles to the water are reversed. And, they are set for the port tack leeway angle.
The forward force generated by the sail depends on the speed of the wind and the attack angle of the sail, as does the heeling force. Each part of the boat generates drags, which oppose the forward force. The hull generates displacement and skin friction drag. Each part which produces aerodynamic or hydrodynamic lift produces fluid dynamic drag, displacement drag and skin friction drag.
The invention increases the forward driving force of the sail while increasing the sum of all drags by a smaller amount than the increase in driving force and improving the pointing capability.
For each combination of wind speed and angle, the settings of the hydrofoils, the sail and the daggerboard can be adjusted for optimum performance. Also in various embodiments the boat's mast height, sail area and sail shape can be designed for best performance.
In moderate to heavy winds, the settings of the hydrofoils are shown in
In light wind on a beat the crew hikes out on the windward side. The wind in
As the wind increases, the crew hikes out as far as possible, as shown in
In
If the wind continues to increase, it is ultimately necessary to lower the negative lift generating hydrofoil to keep the boat upright as shown in
The hydrofoil settings in light to moderately heavy winds with the boat on a run are shown in
Normally best performance of the boat is achieved if the hydrofoils are submerged a little as necessary because the drag produced by the hydrofoil will oppose the driving force of the sail. However, the hydrofoils may be submerged more than optimum for speed considerations in situations where a crew may want to sacrifice speed for stability and safety.
An embodiment which enables the hydrofoils to automatically conform to the leeway angle at which the boat is operating is illustrated in
In these drawing the dotted lines represent the boat. The apparatus straddles the hull of the boat as shown in
Referring to
A hydrofoil holder apparatus rotates to conform to the leeway angle of the boat, just as a weathervane conforms to the direction of the wind. To avoid conflict between the hydrodynamic forces generated by the daggerboard and the hydrofoils, the hydrofoils should conform to the leeway angle. It is a primary object of this embodiment that the hydrofoils substantially assume the leeway angle by virtue of the water passing along them as the boat moves forward. Thus the invention utilizes a mechanism which is similar to that used to mount the rudder on a small sailboat. Just as the rudder will align with the flow of water if the tiller is unconstrained, the hydrofoil will align if the holder assembly is free to rotate in the x-y plane, 20a-11. The mounting mechanism uses a gudgeon and pintle, 20a-12, arrangement like those employed to hang shutters on a house or rudders on boat. In the invention the pintle must be constrained at both ends since the pressures produced by the hydrofoil can be either upward or downward. Also so that the entire hydrofoil holder apparatus can be detached from the boat when the boat is stored or beached, the pintle must be detachable from the gudgeon. A gudgeon/pintle arrangement with this property is used employed on the Sunfish® sailboat and other boats and the small boats and can be obtained from Annapolis Performance Sailing in Annapolis Md.
If each hydrofoil is allowed to freely rotate, since the tip, 20a-13, of a hydrofoil experiences displacement and skin friction drags as water passes by it, the starboard hydrofoil will tend to rotate clockwise as viewed from above, causing it to deviate from the proper leeway angle. The port hydrofoil will rotate in the counterclockwise. If the two hydrofoil holder assemblies are connected by a rod, 20a-14, and if both hydrofoils are immersed by equal amounts, the two rotating forces will cancel each other, and both hydrofoils will both assume the desired leeway angle. This rod should be detachable from the hydrofoil holder apparatuses, to facilitate storage. In
The apparatus can be further understood by examining
FIG. 21-b shows the attack angle adjustment assembly. The back wall, 21b-2, fits inside the leeway adjustment assembly's slot, 21a-5. The assembly rotates in the x-z plane, 21b-3, as shown in the diagram of the coordinates, 21a-7. This rotation sets the attack angle.
The assembly contains a top slot, 21b-4 and a bottom slot, 21b-6 into which the hydrofoil, 21c-1 fits. The cross-sectional profile of the hydrofoil is rectangular in the illustration, which would be acceptable in embodiments having very thin hydrofoils, but in other embodiments an NACA defined shape such as used in airplane wings is preferred as seen in
The operation of the invention can be further understood by examining orthogonal views shown in
Other features to facilitate use and manufacturing of the apparatus can be incorporated into the embodiments described above as would be apparent to a person of ordinary skill in the art. For example, the hydrofoils can be spring loaded so that the retract or rotate to the level of the hull when the boat is beached. In addition, the connector connecting the hydrofoil holders in the automatically adjusting embodiment can be a removable rod. Also, an additional hydrofoil can be placed on the rudder to provide enhanced operation when running.
A Sunfish® with a normal sail and the invention is shown in
In
The invention can take be implemented in other ways and on different boats. In one embodiment the hydrofoil holders are installed on the hull of a boat. In another embodiment, the holders are integral with the hull.
In another embodiment the invention can be applied to single-handed dinghies such as the Laser, two-handed monohulls such as the Laser 2, or larger boats.
Still another embodiment could be applied to a catamaran, such as a Class A catamaran or Tornado. In this embodiment, the hulls of the catamaran could be brought closer together to make it easier for the crew to adjust the positions of the hydrofoils and to decrease the weight of the boat and improve its maneuverability. For catamarans, the daggerboards must be retained to provide leeway angle control.
In yet another embodiment, the starboard and port hydrofoil holders can use separate positive and negative hydrofoil holder slots on each side of the boat, and when coming about the hydrofoil is shifted from one to the other.
For varying wind conditions the holders can be designed for easy removal and replacement so holders set for different attack angles can be used.
The invention can be used on monohulls with keels.
Further embodiments which exhibit self-alignment to the leeway angle appear in
The foregoing description of the preferred embodiments of the invention have been presented only for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to enable others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention only be limited by the claims appended hereto.
Claims
1. An apparatus for a sailboat comprising:
- a. at least two hydrofoil holders, one on the starboard side of the boat and one on the port side, each of which is configured to adjustably hold a hydrofoil in at least two positions; and
- b. the hydrofoils holders and hydrofoils are configured such that the hydrofoils can be retained in the hydrofoil holders substantially parallel to the leeway angle and oriented to extend at least in part away from the hull.
2. The apparatus of claim 1, where the apparatus is configured to resist heeling of the sailboat.
3. The apparatus of claim 1, wherein the holders are configured to adjustably hold the hydrofoils in either a positive lift position or negative lift position.
4. The apparatus of claim 1, wherein one holder is configured to adjustably hold a hydrofoil in a positive lift position and another holder is configured to adjustably hold and a hydrofoil in a negative lift position.
5. The apparatus of claim 1, wherein the hydrofoils are curved and the hydrofoil holders are configured to hold the hydrofoils, so that the center of curvature of the hydrofoils is at or near deck level.
6. The apparatus of claim 1, wherein the hydrofoils are straight and the hydrofoil holders are configured to hold the hydrofoils so that the hydrofoil makes an angle of greater than 30 degrees to a plane defined by the surface of the water.
7. The apparatus of claim 1, wherein the hydrofoil holder and hydrofoils are configured such that the hydrofoils can be retained in the hydrofoil holders parallel to the leeway angle.
8. The apparatus of claim 1, wherein the holders are mounted on the starboard and port gunwales of the hull of the sailboat.
9. The apparatus of claim 1, wherein the holders are integral with the hull.
10. The apparatus of claim 1, wherein the hydrofoils are curved.
11. The apparatus of claim 1, wherein the hydrofoils are straight.
12. The apparatus of claim 1, wherein the hydrofoils are configured to be manually withdrawn and set in a different position when the boat tacks.
13. The apparatus of claim 1, wherein the holders are configured to allow the altitude of the hydrofoils to be altered for either starboard or port operation by partially withdrawing the hydrofoils from the holders.
14. The apparatus of claim 1, wherein the hydrofoil holder is hollow to allow water to pass through it fore to aft, and there is a single slot on the top of the hydrofoil holder and single slot in the bottom, to position the hydrofoils for starboard and port tack operation.
15. The apparatus of claim 1, wherein there are a pair of slots in each hydrofoil holder which define the orientation of the hydrofoil, thereby requiring the hydrofoils to be completely removed from their holders when tacking from starboard to port or from port to starboard.
16. The apparatus of claim 1, wherein there are three possible hydrofoil positions allowing for starboard, port and running operation of the boat.
17. The apparatus of claim 1, wherein the hydrofoil holders are spring loaded so that when the boat is beached, the hydrofoils rotate to the level of the sand.
18. The apparatus of claim 1, wherein there is a lifting hydrofoil on the boat's rudder to provide stability when the boat is riding on its hydrofoils above the plane of the water.
19. The apparatus of claim 1, wherein the hydrofoil holders can be detached from the hull.
20. The apparatus of claim 1, wherein the hydrofoil holders are configured to enable the hydrofoils to automatically adjust to an angle substantially parallel to the leeway angle.
21. The apparatus of claim 20, wherein the hydrofoil holders are attached to the boat by a gudgeon and pintle and the gudgeon and pintle allow automatic adjustment of the hydrofoils to an angle substantially parallel to the leeway angle.
22. The apparatus of claim 20, wherein the hydrofoil holders on the starboard and port sides of the boat are connected and the hydrofoils are constrained to assumed the same leeway angle by the connector.
23. The apparatus of claim 20, wherein the hydrofoil holders are configured to adjustably hold the hydrofoils in either a positive lift position or negative lift position.
24. The apparatus of claim 20, wherein one hydrofoil holder is configured to adjustably hold the hydrofoil in a positive lift position and another hydrofoil holder is configured to adjustably hold the hydrofoil in a negative lift position.
25. The apparatus of claim 20, wherein the hydrofoil holders adjustably hold the hydrofoils in either a positive lift position or negative lift position through use of an attack angle adjustment assembly.
26. The apparatus of claim 21, wherein the gudgeon and pintle enables the hydrofoil holder apparatus to be detached from the boat for operation in light wind or for storage.
27. The apparatus of claim 20, wherein “L” shaped hydrofoils are used.
28. The apparatus of claim 20, wherein curved hydrofoils are used.
29. The apparatus of claim 20, wherein inverted “T” shaped hydrofoils are used.
30. The apparatus of claim 20, wherein hydrofoils with straight vertical sections and curved lower sections are used.
31. The apparatus of claim 20, wherein the starboard and port hydrofoil holders are connected so that the hydrofoils both assume the same leeway angle.
32. The apparatus of claim 31, wherein hydrofoil holders are connected by a connecting rod that is detachable to facilitate storage.
33. The apparatus of claim 20, wherein the hydrofoil holders are spring loaded such that the hydrofoils automatically rotate when the boat rides up on the beach.
Type: Application
Filed: Feb 13, 2013
Publication Date: Sep 26, 2013
Inventor: Jason H. Eveleth (Mountain Lakes, NJ)
Application Number: 13/765,894
International Classification: B63B 1/24 (20060101);