WO2006019306A1

WO2006019306A1 - Propulsion device for exploiting a moving fluid

Info

Publication number: WO2006019306A1
Application number: PCT/NO2005/000274
Authority: WO
Inventors: Tore Lyngholm
Original assignee: WING SAIL AS
Current assignee: WING SAIL AS
Priority date: 2004-07-20
Filing date: 2005-07-19
Publication date: 2006-02-23
Anticipated expiration: 2007-01-20
Also published as: NO20043081L; NO20043081D0

Abstract

A propulsion device for exploiting a moving fluid, the propulsion device (3) comprising two congruent, essentially triangular sail halves (30, 30') with a luff (33, 33'), a leech (32, 32') and a foot (31, 31'). The luffs (33, 33') of the sail halves are joined in the longitudinal direction via extending means. The propulsion means (3) is via a head (40, 40'), a tack (41, 41') and a clew (42, 42') further fastened to a mast (2) and/or in the boat (1), and the sail halves (30, 30') can thus be moved between two main positions, namely: - a first main position, in which the tacks (41, 41') of the sail halves (30, 30') essentially run close to each other and overlap one another so that the sail halves (3, 3') together have a cross-section that forms a wing profile; and - a second main position in which the tacks (41, 41') of the sail halves (30, 30') run away from each other, wherein an upper area (D) of the sail (3) in the second main position is designed to obtain a shape roughly like a delta wing.

Description

Propulsion device for exploiting a moving fluid

The invention relates to a propulsion device for exploiting a moving fluid as disclosed in the preamble of claim 1.

A propulsion device in the form of a sail is shown on page 106 of Sail performance. Theory and practice, C. H. Marchaj, Adlard Coles Nautical, London 1996. This sail is a Bermuda sail with two sail halves or canvases of the same shape and size, whose luff is connected to a mast and whose leech and foot are not interconnected. When sailing close-hauled, the canvases can lie against each other, and the sail can then be used as an ordinary Bermuda sail. When reaching or running, the canvases can be moved apart so that they extend from the mast in different directions.

According to the aforementioned book, this sail has the advantageous properties that reefing can be carried out in a simple manner and that a foresail is unnecessary. Furthermore, the sail area can be doubled while sailing with the wind abaft the beam, i.e., when reaching or running.

It is well known that sailing with the wind abaft the beam, and in particular running, can be perilous in bad weather, as the boat may then be subjected to violent, often combined yawing and rolling motions. In Chapter 7 of the aforementioned book this instability phenomenon is described in more detail. Had improved sailing properties during such sailing been obtained with the known sail, this would in all probability have been mentioned in the book as it would have been of great general interest for both cruising boats and regatta boats, but especially for boats of the last-mentioned type which have a relatively large sail area and high rigging. Furthermore, the applicant's own Norwegian Patent Application No. 20025344 relates to a Bermuda sail with two mutually overlapping canvases of substantially the same shape and size, and reference will be made to this application for a more detailed description of this sail.

The present invention will now be described in the form of an embodiment with reference to the attached drawings, wherein:

Fig. Ia is an illustration of a boat with a propulsion device in accordance with the present invention;

Fig. Ib is an illustration of a boat with two such propulsion device in accordance with the invention, where the propulsion devices are fastened to the boat in different ways; Fig. 2 shows the configuration of two canvases which constitute the propulsion device according to the present invention;

Fig. 3 is a side view of the propulsion device, which in addition shows different horizontal cross-sectional profiles of the device, rotated 90° about a horizontal longitudinal axis of the cross-section;

Fig. 4 is a top view of the propulsion device in different positions, two of the positions showing profiles of the propulsion device with the wind coming from behind (the front of the boat is uppermost);

Fig. 5 is an illustration of the propulsion device with the wind from behind, the device forming an essentially unstable delta wing;

Fig. 6 is an illustration of the propulsion device with the wind from behind, where a lower area of the device has the form of an essentially unstable delta wing, whilst an upper area has the form of an essentially stable delta wing;

Fig. 7 is an illustration of the propulsion device with the wind from behind, the device having the form of an essentially stable delta wing.

In this embodiment of the invention, the propulsion device is a sail which exploits the wind as a moving fluid in order to provide propulsion for a boat. The word "sail" in this application will be used synonymously with the word "propulsion device". Fig. Ia shows a boat 1 with a stay or mast 2. A sail 3 is fastened to the boat 1 and to the mast 2.

The sail 3 in accordance with the present invention comprises two substantially triangular sail halves 30, 30' (Fig. 2). Each sail half 30, 30' comprises respectively a foot 31, 31', a leech 32, 32' and a luff 33, 33'. Fig. Ib shows another boat 1 with two sails 3a, 3b fastened respectively to a stay or a mast 2a or a line 2b and to the boat 1. The sail in accordance with the invention can thus be used as a mainsail and/or foresail.

Furthermore, the area where the leech 32 or 32' meets the luff 33 or 33' is called the head 40 or 40'. The area where the leech 32 or 32' meets the foot 31 or 31' is called the tack 41 or 41'. The area where the luff 33 or 33' meets the foot 31 or 31' is called the clew 42 or 42'.

In Fig. 1 it is shown that the sail 3 is fastened to the top of the mast 2 by one control line 10 secured to the head 40, 40'. The sail 3 is also fastened to a substantially forward area of the boat 1 by one control line 12 secured to the clew 42, 42', whilst each sail half 30, 30' is fastened to a substantially rear area of the boat 1 by control lines 11 secured to the tack 41 and 41', respectively. The control lines 10, 11, 12 are tightened or slackened during sailing as required.

The edges of the luff 33, 33' of each sail half 30, 30' are joined or in another way fastened to each other, or the sail halves 30, 30' are provided as a single unit. The junction of the luffs 33, 33' comprises extending means (not shown). The purpose of the extending means is to extend the sail halves in the horizontal direction of the sails.

Preferably, the extending means are arranged so that the extension varies along the length of the luff. The solid line in each sail half 30, 30' in Fig. 2 indicates the straight line between the head 40, 40' and the clew 42, 42'. The tightening of the control lines 10 and 12 will, because of the distance between the solid line and the joint at the edge of the luffs 30, 30', result in a tightening of the sail halves in a direction essentially parallel to the solid line. However, the luffs 30, 30' will also be moved apart through this tightening.

The distance between the solid line and the edge of the luff will thus indicate the degree of extension. Thus, there is a small degree of extension in the upper and lower areas of the luff, but maximum extension takes place in an area below half of the length of the luff. As the sail material in the area of the luffs 33, 33' is stretched out towards the leeches, the desired wing profile will be altered by slackening or tightening the control lines of the sail. The extending means may be incorporated into the sail material. Preferably, the extending means will comprise flexible ribs or hoops fastened to the sail halves 30, 30', and in particular to the luffs 33, 33'. The positioning of these means should be expedient for the furling of the sail.

When the boat sails close-hauled, the sail 3 will be in a first main position as shown in Fig. 3. The sail halves 30, 30' in this case have essentially the same shape when seen at right angles towards the plane of the sail material, and the sail halves 30, 30' overlap one another. Four cross profiles 51 - 54 of the sail 3 without wind action are shown in Fig. 3 for different degrees of tightening of the sail 3. It is presumed for the sake of simplicity that the degree of tightening is the same in both sail halves. When the sail 3 is tightened slightly, that is to say that the control lines 10 and 12 are relatively slack, a cross profile 54 is obtained. The cross profiles 53 and 52 are obtained on further tightening, and on maximum tightening, the cross profile 51 is obtained. It is seen here that the extending means cause the sail 3 to have a wing- shaped cross profile. Four more cross profiles 61 - 64 of the sail 3 with wind action are shown in Fig. 3 for different degrees of tightening of the sail 3. Here too, it is presumed for the sake of simplicity that the degree of tightening is the same in both sail halves. Each cross profile 61 - 64 is shown with the wind both from port and from starboard. When the sail 3 is tightened slightly, that is to say that the tension in the control lines 10 and 12 is relatively slack, a cross profile 64 is obtained. The cross profiles 63 and 62 are obtained on further tightening, and on maximum tightening, the cross profile 61 is obtained. It is seen here that the extending means also in this case cause the sail 3 to have a curved, wing-shaped cross profile, where the distance between the two sail halves 30, 30', and especially the distance between the luffs 33, 33', decreases with increasing tightening of the sail 3.

Closeable inlet openings (not shown) are preferably provided in the sail halves 30, 30' close to the luffs 33, 33'. When the wind comes towards one of the sides, the inlet openings in the sail half oriented substantially towards the wind direction will be opened whilst the inlet openings in the other sail half will be closed.

Consequently, air will flow into the space between the sail halves and maintain the volume of this space. The overpressure in this space will be vented out through the leeches of the sail halves 30, 30. When the wind comes from behind, the inlet openings in both sail halves will be closed. With the sail in this first loaded main position, a cross-sectional profile of the sail is obtained that is highly favourable. The cross-sectional profile is like a variable wing profile. This means that the sail has greatly reduced turbulence on the pressure side compared with an ordinary sail, which means greater force on the sail. When the boat runs, that is to say sails with the wind from behind, the sail will be in a second main position as shown in Fig. 4 (the wind direction is illustrated by the arrow A). In Fig. 4 it is seen that the sail halves 30, 30' are almost symmetrical about a vertical plane through the longitudinal axis of the boat. The second main position is obtained preferably in that the control lines 11 are fastened between the rear part of the boat 1 and the tack 41, 41', as shown in Fig. 4.

In the second main position, the leech 32 and the foot 31 are no longer close to the leech 32' and the foot 31'. The sail 3 thus obtains a working area in relation to the wind that is twice as big. The problem of instability when running, as mentioned above, can be avoided with the sail 3 in accordance with the present invention in the second main position. This will be described in connection with different tightening of the sail 3 to the positions shown in Figs. 6-7. In Fig. 6 the essentially unstable position is shown. The sail is essentially U- shaped with the opening of the U facing the wind. A large, unstable working area for the wind is obtained.

In Fig. 7 the essentially stable position is shown. This position is obtained by slackening one or more of the control lines 10, 11, 12 further in relation to the position shown in Fig. 6. The sail here is essentially V-shaped with the point facing the wind, and where the legs of the V are curved because of the action of the wind. A wing with a shape like that described and shown in connection with Fig. 7 is called a delta wing. A delta wing is described in Marchaj et al., mentioned above.

Fig. 7 shows a highly favourable position for the sail 3 in accordance with the present invention when running. On slackening the control line 10 compared with Fig. 6, the wind will push the tack (40, 40') of the sail 3 forwards and the solid line on the luff (shown in Fig. 2) will now be at an angle in relation to the horizontal axis. A lower area (E) of the sail 3 will still have a U-shape as shown in Fig. 6, whilst an upper area (D) of the sail 3 will have a V-shape as shown in Fig. 7.

Consequently, a good working area for the wind is obtained by means of the lower area (E) of the sail 3, whilst the top area (D) of the sail 3 has a shape that contributes to stability. Instability as described above will be avoided. Tightening the propulsion device can take place by controlling the lines 10, 11, 12 and/or by altering the curvature of the mast 2, 2a or the forestay 2b.

It should be noted that the invention is not limited to the exemplary embodiment described above and in the drawings. It will be clear to a person of skill in the field that the invention can be varied within the scope of the patent claims. For example, the sail halves are described as being essentially triangular, but the sail halves could of course have other configurations.

In the first and second main positions, the sail 3 can preferably be furled according to need, as can be done with other types of sails.

It should be noted that the second main position of the sail 3 can also be used when sailing with the wind at an angle from behind.

Claims

PATENT CLAIMS

1. A propulsion device for exploiting a moving fluid, the propulsion device (3) comprising two congruent, essentially triangular sail halves (30, 30') with a luff (33, 33'), a leech (32, 32') and a foot (31, 31'), wherein the luffs (33, 33') of the sail halves are joined in the longitudinal direction, wherein the propulsion device comprises extending means, wherein the sail (3) is via a head (40, 40'), a tack (41, 41') and a clew (42, 42') further fastened to a mast (2) and/or in the boat (1), and the sail halves (30, 30') can thus be moved between two main positions, namely: - a first main position, in which the tacks (41, 41') of the sail halves (30, 30') essentially run close to each other and overlap one another so that the sail halves (3, 3') together have a cross-section that forms a wing profile; and

- a second main position in which the tacks (41, 41') of the sail halves (30, 30') run away from each other, wherein an upper area (D) of the sail (3) in the second main position is designed to obtain a shape roughly like a delta wing.

2. A propulsion device in accordance with claim 1, characterised in that the sail halves (30, 30'),close to the luff (33, 33') have inlet openings designed to allow air into the space between the sail halves (30, 30'), which maintains the volume of the space.

3. A propulsion device in accordance with claim 1 or 2, characterised in that the extending means are incorporated into the sail material and/or comprise ribs or hoops.

4. A propulsion device in accordance with one of the preceding claims, characterised in that the sail alternates between the first and the second main position when the load direction is changed.