EP1412244A1

EP1412244A1 - Method and device for the aerodynamic control of a multi-hull sailing vessel

Info

Publication number: EP1412244A1
Application number: EP01923414A
Authority: EP
Inventors: Christophe Van Laethum
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-04-05
Filing date: 2001-04-05
Publication date: 2004-04-28
Also published as: WO2002081296A8; WO2002081296A1

Abstract

The invention relates to a method and a device for the aerodynamic control of the attitude of a multi-hull sailing vessel, independently of the sailing vessel. For this purpose, mobile aerodynamic flaps are disposed in the superstructure, preferably to the rear of the sailing vessel. Said flaps can be used to control the list and the trim.

Description

METHOD AND DEVICE FOR AERODYNAMIC CONTROL OF A MULTIHULL SAILING YACHT

The invention relates to a sailboat, or multihull sailing boat, and more particularly to a method and a device for aerodynamically controlling, independently of the sail, the attitude of the boat, that is to say its trim and its list.

In general, a multihull sailing boat, that is to say a catamaran or trimaran, is intended to sail, at cruising speed, with sufficient heel to rely essentially only on a single lateral hull, the hull "wet", the opposite hull (located facing the wind) on the other hand being lightened or lifted, and as far as possible leveled off, or out of water, so as to reduce drag. The angle of heel results on the other hand essentially from the balance between the capsizing torque due to the force of the wind on the wing, and the return torque due to the weight of the planed hull, located facing the wind.

When you want to sail on a single hull, controlling the heeling angle is important. Indeed, as the angle of heel increases, the return torque, and therefore the stability, decrease.

A typical countermeasure to reduce the angle of heel consists - apart from a displacement of the load of the boat by displacement of the people on board - to reduce the force of the wind on the wing, by reducing it, or even by modifying the angle of incidence of the wind on the sails.

This reduction of the wind force on the wing simultaneously reduces the wind propulsion force on the boat, and is therefore accompanied by a loss of speed, which is not desirable.

It would therefore be desirable to have a means of controlling the angle of heel independently of the airfoil, so as to allow the upper limit of this angle to be pushed back while maintaining the airfoil, or even to increase the angle of heel when it is too low.

On the other hand, the inclination of the boat in the longitudinal direction, or trim, also varies according to the navigation conditions, including the state of the sea or the body of water, and the parameters of the sail, and it is also desirable to be able to control the trim of the boat independently of the sail. The object of the invention is therefore to provide such a boat, comprising an aerodynamic means, independent of the wing, for controlling the attitude of the boat, namely the angle of heel and the trim.

According to the invention, this is achieved by generating in the superstructure of the boat, and independently of the wing, an additional aerodynamic force, substantially perpendicular to the direction of movement of the boat, and therefore non-propulsive, adjustable in direction and in size. .

According to the invention, this additional aerodynamic force is obtained by at least one, and preferably two adjustable aerodynamic flaps, integral with a superstructure spanning the hulls of the boat, at the rear of the latter, and arranged symmetrically by relative to the longitudinal axis of the boat. For the attitude correction, the flaps will normally be pivoted in the same direction, downwards to tend to raise the stern of the boat and counteract a too strong rearward movement, or upwards to strengthen the otherwise the rearing, for example in heavy sea, with risk of charging. For the heel correction, it is preferable to activate only the flap located on the windward side, the furthest away from the hull serving as a support, flap whose force has the longest lever arm relative to the pivot axis capsizing, and therefore ensuring the best torque, 1 actuation taking place in the desired direction to obtain the desired straightening / lifting effect. Other aspects, characteristics and advantages of the invention will appear from the description which follows, and from the appended drawings in which:

Figure 1 is a schematic perspective view of a trimaran according to the invention, Figure 2 is a front view intended to show the forces at play.

Referring to FIG. 1, the aerodynamic control device of the invention is shown mounted at the rear of a trimaran generally designated by the reference numeral 1.

This device comprises a superstructure 2, spanning the three hulls 3, 3 ', 3 "of the trimaran, and provided with mobile aerodynamic flaps 4, 5.

The mast is on the other hand sketched at 6, the terminal at 7, and the sail at 8.

As mentioned above, the object of the invention is to provide aerodynamic control of the attitude of the boat, and particularly of its list, to keep it within a desirable range, taking into account that the '' we want to sail the boat as much as possible while resting on a single hull - the wet hull - so as to reduce drag. To this end, and as can be seen more clearly in the diagram in Figure 2, at least one flap (generally the flap located on the windward side, the furthest away from the wet hull) is inclined in the desired direction to exert a stabilizing torque in relation to the longitudinal axis of the boat.

In the diagram of Figure 2, the wind force, represented by arrow A, is assumed to be too large to maintain the heeling angle oL in the desired range, and the flap 4 is therefore raised to exert a force, represented by arrow B, opposing the capsizing torque due to the force A of the wind.

When the boat begins to sail, and is still more or less symmetrical on its outer hulls, it is also interesting to orient the flap located on the windward side (flap 4 in Figure 2) towards the bottom, to favor the lifting of the hull 3. Indeed, the initial planing of a hull requires a greater effort than what happens at cruising speed, insofar as the speed of the boat is at this moment lower , and its greater contact surface with water, and therefore its drag. When planing, the drag decreases suddenly, with a sudden gain in speed. The flaps 4 and 5 are identical, and arranged symmetrically with respect to the longitudinal axis of the boat.

In normal operation, only the flap 4, whose aerodynamic force then has the largest lever arm relative to the pivot axis located in the wet hull, will be advantageously used when the boat is sailing in abutment on the starboard hull 3 " , and only the flap 5 will be used when the boat is resting on the port hull 3.

However, the two flaps 4, 5 can also be used simultaneously if desired, the simultaneous and symmetrical action of the flaps can be used to correct the attitude, or attitude of the boat in the longitudinal direction, or to reduce the angle trim by reducing the stern of the boat, when the boat tends to pitch up too much, or to reinforce the nose up, for example in the event of risk of charging.

The flaps can be controlled by known devices, such as jacks or racks, controlled directly by the pilot or even automatically, taking into account parameters such as the speed of the boat, the angle of heel, its speed. variation, wind speed, and the like.

The superstructure 2 on which the flaps are mounted will advantageously be a boat structure beam, so as not to unnecessarily increase the aerodynamic drag of the superstructure. If necessary, the superstructure 2 can however also be provided in addition, being then designed to withstand only aerodynamic forces.

In the latter case, it is the whole of the superstructure which can constitute the flaps, by being divided into two elements articulated to one another and at their junctions with the shells.

In the drawing, a trimaran has been shown, but it is clear that the invention applies to multihull sailboats in general, and in particular to catamarans. The invention thus also applies to multihulls with hydrofoils, still allowing a gain in drag and speed compared to conventional multihulls. To better understand the invention, we will describe below an illustrative example of application of the invention, during navigation of a multihull as shown in Figures 1 and 2. The wind is assumed to come from port, as illustrated in figure 2.

At the start, the flaps 4, 5 are in the neutral, non-active position, in the axis of the superstructure 2, and the boat rests essentially symmetrically on its side hulls 3, 3 ".

As soon as the relative wind speed is deemed sufficient for an aerodynamic effect on the flaps, the flaps 4, 5 are advantageously actuated to improve the attitude. Thus, on a calm body of water, the flaps will generally be lowered to the maximum, to generate an aerodynamic force working in the direction of a reduction in the stern of the boat, thus reducing the pitch up, while at the same time tending to reduce the wet surface, and therefore the hydrodynamic drag, so as to accelerate the speed gain. On a stirred body of water, on the other hand, with the risk of charging, the flaps will be advantageously raised to increase the pitch-up, and thus reduce the risk of charging.

As the speed, and therefore the aerodynamic effect on the flaps, increases, the flap 5 can be gradually brought back to the neutral position to reduce aerodynamic drag, while the flap 4 is lowered, to promote planing of the hull 3, thanks to an unbalanced aerodynamic force relative to the longitudinal axis of the boat.

The planing of the hull 3 causes an abrupt reduction in the drag, and thus an abrupt increase in the speed. The boat is then in cruising speed, with sufficient heel so that the hulls 3, 3 'are essentially out of the water, and that buoyancy is no longer ensured except by the hull 3 "which is then the support hull. At this stage , and as a function of navigation parameters of the boat such as the angle of the wind relative to the direction of movement of the boat, and the direction of movement, in a straight line or in a curve, the flap 4 located on the side of the hull 3 planed, will be pivoted up or down, respectively to assist a righting or a lifting of the boat.

The flaps must be controlled independently, and can be controlled by any known means, for example by double-stroke cylinders, or by racks, controlled by the pilot or automatically. Such control systems are known in the art, and need not be described in more detail here.

In the present description, the term “shutter” generally means a movable, adjustable profiled member, intended to generate an aerodynamic effect, whether it is a profiled member articulated to a fixed structure, as shown diagrammatically in the drawing, or the whole of a profiled structure. mobile, as could be the structure 2, made in two parts hinged to each other and at their junctions with the shells.

As regards the number of flaps, these are preferably two in number, to take advantage of a possible effect of asymmetry with respect to the longitudinal axis of the boat. They may however be in greater number, without this providing a practical advantage within the framework of the invention

Claims

claims

1. A method of controlling the attitude of a multihull, sailing boat, characterized in that it consists in generating in the superstructure of the boat, independently of the airfoil, an additional aerodynamic force, and in adjusting the size and the direction of said aerodynamic force to modify the attitude of the boat.

2. Method according to claim 1, characterized in that it consists in generating an aerodynamic righting torque, opposite to a capsizing torque produced by the airfoil, when a heeling angle approaches an upper limit, and an aerodynamic lifting torque, in the same direction as the capsizing torque due to the airfoil, when the angle of heel approaches a lower limit.

3. Method according to claim 1 or 2, characterized in that it consists in generating the aerodynamic torque by means of at least one aerodynamic component. 3. Method according to claim 2, characterized in that it consists in providing the aerodynamic component on a superstructure spanning the hulls of the multihull boat, at the rear part thereof.

4. Device for controlling the attitude of a multihull, sailing boat, characterized in that it comprises at least one aerodynamic flap mounted on a superstructure spanning the hulls, designed to generate an additional aerodynamic force, and a means for controlling the pivoting of said flap, for adjusting its angle of attack

5. Device according to claim 4, characterized in that it comprises two flaps, mounted on said superstructure, symmetrically to the longitudinal axis of the boat.

6. Device according to claim 5, characterized in that it comprises an independent control means for each flap

7. Device according to any one of the preceding claims, characterized in that said superstructure is mounted at the rear of the boat.