GB2478313A - Automatically controlled self-trimming wingsail - Google Patents

Abstract

A wingsail sailset comprises a main symmetrical wing 1 which is freely rotatable 360 degrees about an upright axis 5 and a tail vane 3 which is settable about an upright axis spaced from the axis of the main aerofoil to cause the main aerofoil to adopt an angle of attack to the direction of the wind. The setting of the tail vane is adjusted by a pushrod 9 or wires connected to a circular cam 4, mounted eccentrically to the sailset pivot. The cam can be moved by the operator from an eccentric position to a concentric position to allow the tail vane to lessen its effect or assume a zero angle of attack, and in so doing, lessen the thrust of the main wing or bring the thrust to zero for parking purposes.

Description

I

Mechanical Automatic Control for Self-Trimming Wingsail.

Field of the Invention

The invention relates to self-trimming wingsails, which are aerodynamic devices that use the wind to provide propulsion for boats or land vehicles. They work in principle in a similar way to aircraft wings, but are arranged vertically instead of horizontally.

Background of the Invention

To provide thrust, a wingsail needs to be presented to the airflow at a favourable angle of attack to push in the required direction.

On some designs this angle is adjusted manually whilst others known as "self-trimming" use a supplementaiy, smaller airfoil surface or tail, mounted downwind, arid attached to the main wing, and the whole assembly, or "sailset" pivots vertically at or near the centre of pressure of the main wing and automatically aligns the main wing to the correct angle to the wind, operating in a similar way to a weathervane.

On the self-trimming type, the main wing, or wings, are pivoted about a vertical axis on or very near their centre of pressure and therefore the force required to change the angle of attack is small.

The tailvane, which is connected to the main wing by an ann or arms, is distant from the pivot point at the centre of pressure, thus introducing a mechanical advantage or lever.

This means that by varying the angle of attack of the tail it is possible to move the whole assembly, easily bringing the main wing to a suitable angle alignment, in a similar way to how a rudder controls the direction of a boat. (See figure 1) In the case of an aircraft, the wings (in normal flight) only need to provide lift in one direction, but to propel a boat, there is a requirement for lift to be provided from wind on either side of the aerofoil. In an aircraft this would be equivalent to having the ability to equally well fly upside down as well as the right way up. This means that on a boat the aerofoil must be symmetrical in the vertical plane, or, have a variable configuration to work as a mirror image on either side.

To provide lift from winds on either side of the boat, as mentioned above, the tail needs to be deflected accordingly, (See figure 1) and this invention provides a mechanical, automatic means of doing that.

Statement of invention

It is an object of this invention to provide a simpler way of automatic tacking and adjustment for a sailset, in a mechanical way, and without the aid of a computer, producing an integrated self-trimming/self-tacking fully automatic system that requires no input from the sailor apart from adjusting power levels in forward or reverse.

A further purpose of this invention is to provide the pilot with a way of putting the sailset into "neutral", with the main wing at zero angle of attack, where it provides no thrust in any direction, no matter what direction the wind comes from, for parking when the boat is moored and not in use.

Advantages These objects, when realised, provide a sailset which is controlled by only one lever, with variation from "neutral" to "full power" in forward and reverse.

This lever may also be connected to a wind-sensing device, mechanical or electronic, which would lessen the thrust setting if the level of thrust becomes liable to cause capsize or threatens to overpower the boat.

Using this system, the pilot does not need to have any knowledge of traditional sailing techniques, nor does he have to differentiate between left and right tack, as he can allow the system to adjust itself to eveiy wind direction.

This makes the system particularly suitable for older people who find traditional sailing too arduous, the disabled, and sailors without previous experience, and in third world countries where it would be easy to construct. It would also be suitable for robot autonomous boats.

As this system is fully automatic and requires no manual adjustment for different points of sailing and different tacks, it is also vely suitable as a fuel saving device to be fitted to any boat as it requires no attention and will automatically give thrust from the wind coming in all strengths and directions at all times.

Although the primary purpose of the invention is to simplify the process of sailing, there are other benefits, in that rigid wings are acknowledged to be more efficient than traditional flexible sails and enable a boat to sail closer to the wind and obtain higher speeds due to the better lift to drag ratio.

Description with reference to the drawings

Figures 1 -4 Are an aid to background understanding and an example of how self-trimming wingsails work in general and does not incorporate the invention.

Fig I Shows an example of a basic wingsail assembly or sailset in side elevation mounted on a boat, with the main wing 1, which pivots around its axis 2 relative to the boat or land vehicle through the action of the tail 3 responding to changes in the direction of the wind. (weathercocking).

Fig 2 Shows the same in plan view with the tail adjusted in line with the main wing and keeping the main wing at a zero angle of attack and thus providing no thrust to the boat -sometimes known as the "parking position".

Fig 3 Shows the same boat when the wind blows from the right hand side with the tail deflected, thus forcing the main wing 1 to an angle of attack which provides thrust to drive the boat.

Fig 4 Shows the same boat when the wind blows from the left with the tail deflected the other way, thus pushing the wing 1 to an opposite angle of attack to drive the boat.

Figures 5 to 9 Incorporates the invention.

FigS Shows a plan view of the sailset in a parking position with the wing providing no thrust to drive the boat.

The main wing 1 (shown dotted) is connected to the tail 3 as in Fig 1.

The cam, which is perfectly circular 4 is mounted on runners which allow it to slide in the direction of the fore and aft axis of the boat. (Its centre is slotted to allow for the movement). The rotational axis of the sailset 5 can lie in the centre of the cam, but the cam can also be moved either way to move its centre away from the sailset centre, thus making it eccentric.

There are two parallel followers 6 connected together by a crosspiece 7 which is pivoted on the base of the main wing (shown dotted) at its centreS. The two followers are adjusted to make gentle sliding contact with the cam.

A control rod 9 is connected to one end of the crosspiece, and at the other end is connected to an arm 10 which pivots the tail on its vertical axis.

In this drawing the cam is shown in a concentric position to the vertical axis of the main wing and because of this, rotation of the sailset by the wind does not cause the tail to be deflected.

Fig 6 shows how, with the cam in the same concentric position to the vertical axis of the main wing as in Fig 5, the same parking position is achieved even when the sailset has moved 90° in response to a wind coming from 900 to the left of the boat.

Fig 7 Shows the cam when it is moved rearwards by the pilot to become eccentric to the main axis in order to provide thrust to drive the boat forwards, with the wind coming from the left. The rearwards movement of the cam has caused the follower/crosspiece assembly to rotate about axis 8 thus pulling the control rod 9 and changing the angle of the tail to an advantageous position to bring the main wing to a forward thrust angle of attack.

Fig 8 Is a mirror image of Fig 7 and shows the cam in the same position as in Fig 7 but with the wind coming from the right and in this case the follower/crosspiece assembly has rotated the other way pushing the arm 9 and also giving an advantageous position causing the wing to develop forward thrust on the other tack.

Fig 9 Shows that with the cam set rearwards, as in Fig 7 and the wind coming from straight ahead, the follower/crosspiece assembly 6 and 7 comes to the central position and effectively puts the tail 3 into a neutral position, therefore causing the main wing to adopt a zero degree angle of attack, which is desirable because the wind cannot drive the boat when it is coming from directly ahead. In this position the wing and tail are in the lowest drag position to help alleviate the tendency for the wind to drive the boat backwards.

Therefore, with the cani moved rearwards, (in this example to obtain forward drive) the tail is deflected the most when the sailset moves in response to the wind blowing from 900 either side of the boat, progressively reducing to zero when the wind blows directly ahead of the boat or directly astern.

The above equally applies, but in the opposite direction, when the cam is displaced forwards, giving reverse drive to the boat.

(If it happened to be more convenient, it would be perfectly possible to modify the system to work in the opposite sense, i.e. cam forward for forward or rearwards for reverse) To summarise: The cam, (which apart from its sliding motion is connected to the boat and not allowed to pivot), converts the relative circular motion of the sailset as it rotates around it, into reciprocating motion which adjusts, through a control rod, (or control lines), the angle of the tail to provide thrust from the wing in the required direction automatically, whether the wind is coming from the right, left, or straight ahead.

The cam is able to slide in a fore and aft direction and its movement from concentric to eccentric position relative to the main axis, is pilot controlled via the power lever.

Thus, the pilot is able to adjust the eccentric effect of the cam, and in the middle position achieve a neutral setting where no thrust comes from the wing at all.

To enable the cam to be moved from concentric to eccentric, the cam is mounted on runners which allow it to slide to the required position, and it has a slotted centre to allow the movement. The sliding movement of the cam can be actuated from the power lever by suitable means such as cable, wire, or rod.

Claims 1. A freely rotating sailset which can rotate 360 degrees comprising main wing/wings and downwind tailvane, where deflection of the tailvane is mechanically adjusted directly by the rotation of the whole assembly as it follows the wind direction.

2. A sailset as in claim I above where the adjustment of the tailvane is accomplished by a circular non-rotating cam which is mounted eccentrically to the axis of the main sailset.

3. A sailset as in claim I above where the aforementioned circular cam can be moved at will to become concentric with the main axis, thus bringing the deflection of the tailvane to zero to provide a non-thrust position for the main wing.

Claims (3)

1. Claims 1. A freely rotating sailset which can rotate 360 degrees comprising main wing/wings and downwind tailvane, where deflection of the tailvane is mechanically adjusted directly by the rotation of the whole assembly as it follows the wind direction.
2. 2. A sailset as in claim I above where the adjustment of the tailvane is accomplished by a circular non-rotating cam which is mounted eccentrically to the axis of the main sailset.
3. 3. A sailset as in claim I above where the aforementioned circular cam can be moved at will to become concentric with the main axis, thus bringing the deflection of the tailvane to zero to provide a non-thrust position for the main wing.