GB1581625A

GB1581625A - Hydrofoil sailing vessel

Info

Publication number: GB1581625A
Application number: GB52841/75A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-03-22
Filing date: 1977-03-22
Publication date: 1980-12-17

Description

(54) A HYDROFOIL SAILING VESSEL (71) I, JOHN GRAHAM WALKER, formerly of Ayias Lavras 10, Ano Glyfada, Greece, now of, 14 Winchmore Drive, Trumpington, Cambridgeshire, being of British nationality, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to hydrofoil sailing vessels.

The invention in its broadest aspect provides a sailing vessel comprising a hydrofoil assembly which is pivotally mounted on a support so that the pivot axis passes upstream of the hydrodynamic centre of the hydrofoil assembly to enable the assembly to weathercock.

According to the invention there is also provided a hydrofoil sailing vessel comprising a weathercocking, surface piercing, bow hydrofoil which is pivotally mounted so that the pivot axis passes upstream of the hydrodynamic centre of the bow hydrofoil, a fully immersed stern hydrofoil with an upright strut which comprises the vessel's rudder and a lateral hydrofoil mounted on a weathercocking strut.

The term weathercocking is used to imply aligning in the position of least resistance with respect to the flow or the relative flow of the water. "Surface piercing" or "fully immersed" refer to the type of hydrofoil, i.e.

a surface piercing hydrofoil is one which when in its operative position pierces the surface of the water and a fully immersed hydrofoil is one which when in its operative position is fully immersed in the water.

The vessel may be provided with two lateral hydrofoils or a single lateral hydrofoil may be mounted so that it can be swung from one side of the vessel to the other. Both the stern hydrofoil and the lateral hydrofoil may be retracted by pivoting aftwards. The lateral hydrofoil may be mounted on a lateral arm the span of which may be adjustable.

The invention is now described by way of example with reference to the accompanying drawings in which: Figure 1 is a perspective view of an embodiment of the invention, and Figure 2 is a view of the sailing vessel of Figure 1 from the stern.

The sailing vessel illustrated in Figure 1 has an arm A which carries a hydrofoil B the upper surface, of which, in this embodiment, is angled towards the vessel to react against both the overturning and the leeway producing effects of the sails of the sailing vessel.

Co-pending application no. 52842/75 Serial No. 1581626 describes and claims angled hydrofoil mountings, and also the pivotable lateral arm. In the figure the sails have been omitted for clarity. The arm A is mounted to the hull C of the vessel, this mounting may either be fixed or, as shown comprise a vertical or near vertical bearing D so that it can be swung around by wires or other means so as always to be on the required side, e.g. if it is a hydrofoil which provides lift this will be to the leeward side. Hydrofoil B is mounted to the arm A via a hydrofoil strut J, the strut J being mounted to the arm A by a low friction bearing K so that the axis of the bearing passes well ahead of the hydro-dynamic centre of the strut/hydrofoil combination.In embodiments in which a fixed lateral arm or arms are provided the lateral hydrofoils may be retracted and adjusted by pivoting afterwards, for example as described and claimed in co-pending application 52844/75. Serial No. 1581627.

A rudder E is fitted to the transom of the hull, and optionally for static and low speed stability light side floats F are fitted so that the hull may be as slender as possible for the lowest displacement mode resistance. A set of fixed immersed hydrofoils G are fitted to the lower portion of the rudder and the whole rudder assembly is arranged to pivot aft about pin H for retraction and adjustment of hydrofoil angle of incidence.

An extension L ahead of the stem of the vessel carries a surface piercing hydrofoil set M, which is mounted to the extension L by a free low friction bearing N, the upright axis of which lies in the plane of symmetry of the vessel and passes well ahead of the hydrodynamic centre of the hydrofoil set M so that the hydrofoil set will tend to weathercock and thus provide lift without affecting the directional or yaw stability of the vessel. A bearing P allows the hydrofoil set to be retracted and lowered by, for example, lines Q led to the cockpit, while some means such as a preset spring catch R holds the hydrofoil set down so that lines Q may be normally slack, leaving the hydrofoil set free to weathercock.

The bow hydrofoil set M is shown as a V type, however, other shapes such as a ladder type may also be used. An alternative mechanical arrangement of the bow hydrofoil mounting is illustrated in Figure la which has a horizontal lateral axis retraction pivot bearing P1 in the extension L, to which is mounted the free rotating vertical weathercock bearing N1, which in turn carries the hydrofoil set M. This arrangement avoids the need for lines Q to go slack, so that the catch R may be mounted elsewhere, but is otherwise similar to the previously described embodiment.

The stability of the vessel, when flying, may be analysed in the usual three senses, pitch, roll and yaw. The pitch stability is provided by setting the bow hydrofoil set M to work higher on its lift/incidence curve that the rudder hydrofoil set G. The yaw stability is provided by ensuring through the weathercocking that neither bow hydrofoil M or strut J can interfere in yaw stability, and by arranging the incidence of the arm foil B so that it is always working higher on its lift/incidence curve than is the rudder E.

Figure 2 shows schematically the lines of action of the forces acting on the vessel which affect the roll stability. The line of action of the arm hydrofoils output force represented by line T is arranged to pass through the intersection of the lines of action of the sail force V and the vessel's weight Y as viewed along the direction of the vessel's motion. Any bending of the sails and arm due to the forces being reacted will cause the intersection of T and V to move to, say, point X, and the resultant couple will cause the vessel to heel in the direction of arrow W until the line of action of Y once more interacts so as to produce equilibrium.Alteration of the line of action of the lateral hydrofoil's output force to some new line of action T1, for example by pulling on a wire Z and reducing the span of the arm which carries the lateral hydrofoil, enables the new hydrofoil output force direction Tl and the new sail force V1 to intersect at a point S once more vertically above the centre of gravity of the vessel so that upright sailing may once more be achieved.

In the case where a rigidly fixed lateral arm is used, the hydrofoil may be adapted to push up when to leeward and to pull down when to windward, or a second mirror image hydrofoil, strut and arm may be provided on the opposite side of the vessel. When a pair of lateral hydrofoils are provided the side floats F may be directly mounted to their arms, and either the windward hydrofoil may be retracted and unused until the vessel changes tack, or it may be lowered, and arranged to pull downwards and outwards, while the leeward hydrofoil pushes upwards and inwards.

WHAT WE CLAIM IS: 1. A hydrofoil sailing vessel comprising a weathercocking, surface piercing, bow hydrofoil which is pivotally mounted so that the pivot axis passes upstream of the hydrodynamic centre of the bow hydrofoil, a fully immersed stern hydrofoil with an upright strut which comprises the vessel's rudder and a lateral hydrofoil mounted on a weathercocking strut.

2. A vessel according to claim 1 in which the bow hydrofoil interacts full pitch stability with the stern hydrofoil.

3. A vessel according to claim 1 or claim 2 in which the bow hydrofoil is set to work higher on its lift/incidence curve than the stern hydrofoil.

4. A vessel according to any preceding claim in which the lateral hydrofoil interacts with the stern hydrofoil.

5. A vessel according to any preceding claim in which the lateral hydrofoil is set to work higher on its lift/incidence curve than the stern hydrofoil.

6. A vessel according to any preceding claim in which the strut is mounted on a laterally extending arm by a low friction bearing the axis of which passes ahead of the hydrodynamic centre of the strut and hydrofoil combination.

7. A vessel according to any preceding claim in which the span of the laterally extending arm is adjustable.

8. A vessel according to any preceding claim in which the line of action of the resultant force of the lateral hydrofoil is adjustable.

9. A vessel according to any preceding claim in which the weathercocking strut is mounted on a laterally extending arm which can be swung about an upright bearing from one side of the vessel to the other.

10. A vessel according to any one of claims 1 to 8 in which the lateral hydrofoil is adapted to push up when it is on the leeward side and to pull down when it is on the windward side.

11. A vessel according to any one of claims 1 to 8 in which lateral hydrofoils are provided on each side of the vessel.

12. A vessel according to claim 11 in which the lateral hydrofoils are used alternatively depending on the tack being sailed.

13. A vessel according to claim 11 in which both lateral hydrofoils sets are used

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the hydrofoil set will tend to weathercock and thus provide lift without affecting the directional or yaw stability of the vessel. A bearing P allows the hydrofoil set to be retracted and lowered by, for example, lines Q led to the cockpit, while some means such as a preset spring catch R holds the hydrofoil set down so that lines Q may be normally slack, leaving the hydrofoil set free to weathercock. The bow hydrofoil set M is shown as a V type, however, other shapes such as a ladder type may also be used. An alternative mechanical arrangement of the bow hydrofoil mounting is illustrated in Figure la which has a horizontal lateral axis retraction pivot bearing P1 in the extension L, to which is mounted the free rotating vertical weathercock bearing N1, which in turn carries the hydrofoil set M. This arrangement avoids the need for lines Q to go slack, so that the catch R may be mounted elsewhere, but is otherwise similar to the previously described embodiment. The stability of the vessel, when flying, may be analysed in the usual three senses, pitch, roll and yaw. The pitch stability is provided by setting the bow hydrofoil set M to work higher on its lift/incidence curve that the rudder hydrofoil set G. The yaw stability is provided by ensuring through the weathercocking that neither bow hydrofoil M or strut J can interfere in yaw stability, and by arranging the incidence of the arm foil B so that it is always working higher on its lift/incidence curve than is the rudder E. Figure 2 shows schematically the lines of action of the forces acting on the vessel which affect the roll stability. The line of action of the arm hydrofoils output force represented by line T is arranged to pass through the intersection of the lines of action of the sail force V and the vessel's weight Y as viewed along the direction of the vessel's motion. Any bending of the sails and arm due to the forces being reacted will cause the intersection of T and V to move to, say, point X, and the resultant couple will cause the vessel to heel in the direction of arrow W until the line of action of Y once more interacts so as to produce equilibrium.Alteration of the line of action of the lateral hydrofoil's output force to some new line of action T1, for example by pulling on a wire Z and reducing the span of the arm which carries the lateral hydrofoil, enables the new hydrofoil output force direction Tl and the new sail force V1 to intersect at a point S once more vertically above the centre of gravity of the vessel so that upright sailing may once more be achieved. In the case where a rigidly fixed lateral arm is used, the hydrofoil may be adapted to push up when to leeward and to pull down when to windward, or a second mirror image hydrofoil, strut and arm may be provided on the opposite side of the vessel. When a pair of lateral hydrofoils are provided the side floats F may be directly mounted to their arms, and either the windward hydrofoil may be retracted and unused until the vessel changes tack, or it may be lowered, and arranged to pull downwards and outwards, while the leeward hydrofoil pushes upwards and inwards. WHAT WE CLAIM IS:

1. A hydrofoil sailing vessel comprising a weathercocking, surface piercing, bow hydrofoil which is pivotally mounted so that the pivot axis passes upstream of the hydrodynamic centre of the bow hydrofoil, a fully immersed stern hydrofoil with an upright strut which comprises the vessel's rudder and a lateral hydrofoil mounted on a weathercocking strut.

simultaneously, the leeward set pushing upwards and inwards and the windward set pulling downwards and outwards.

14. A hydrofoil sailing vessel substantially as herein before described with reference to and as illustrated in the accompanying drawings.

15. A sailing vessel comprising a hydrofoil assembly which is pivotally mounted on a support so that the pivot axis passes upstream of the hydrodynamic centre of the hydrofoil assembly to enable the assembly to weathercock.

16. A sailing vessel according to claim 15 in which the hydrofoil assembly comprises a hydrofoil and a strut.

17. A sailing vessel according to claim 1 in which the hydrofoil assembly comprises a ladder-type hydrofoil.

18. A sailing vessel according to claim 1 in which the hydrofoil assembly comprises a V-type hydrofoil.

19. A hydrofoil sailing vessel according to claim 16 in which the strut is weathercocking.

20. A hydrofoil sailing vessel according to claim 19 in which the hydrofoil is inclined towards the vessel when the vessel is upright so that the line of action of its output force passes generally through the intersection of the lines of action of the vessel's weight and the sail force.

21. A hydrofoil sailing vessel according to claim 19 in which the hydrofoil is inclined towards the vessel when the vessel is upright so that the output force of the hydrofoil has a horizontal component.