GB2218956A - Sea anchor having vanes of curved cross-section - Google Patents

Abstract

A kite or drogue for marine use comprises divergent side panels 18 (optionally extending rearwardly into integral fins connected by four vanes 19, 20, 21, 22 of curved cross-section, through which passes a central pillar 23. A rigid structure including an apertured tow bar 28 extends forwardly of the vanes and provides a selection of points of connection for a pair of wire strops 30. For use as a sea anchor the kite may be deployed from a vessel by a single line connected to both strops: for use as emergency steering gear each strop is preferably connected by a separate line to a respective side vessel's stern, means, such as a sheet winch, being provided to adjust the length of each line independently. <IMAGE>

Description

IMPROVEMENTS RELATING TO SEA ANCHORS This invention relates to sea anchors.

Defined in the most general terms a sea anchor is any body that may be deployed from a vessel in heavy weather to provide resistance as it is dragged through the water and thus helps to keep the vessel in a desired orientation. Although a sea anchor is usually veered from the vessel's bow to hold the bow to the wind and reduce the rate of drift, it may be streamed from the stern of a vessel running before the wind to help to hold the vessel stern on, and to reduce the vessel's forward speed.

It is common practice in minesweeping, for the purposes of keeping towed gear at a desired depth below the surface, to use a kite comprising a framework having planar side (vertical) members connected by top, bottom and one or more intermediate (horizontal) members (hereinafter referred to as vanes) of curved cross-section, the concave faces of which face upwardly and slightly forwardly, for example at an angle of 25 to the horizontal. The kite is towed in a generally vertical attitude through the water by a tow rope connected to a bridle attached to each upper, forward corner and which is adjustable so that the fore-and-aft inclination of the kite to the vertical may be altered, and hence the depth at which the kite is towed at a given speed may be varied.

According to the present invention such a kite is used as a sea anchor by veering it from the vessel's bow or by streaming it, preferably centrally, from a vessel's stern; unlike any conventional sea anchor it has the advantage that the heavier the load placed upon it, the deeper it dives and the greater the resistance offered to the pull exerted by the vessel.

Although a suitably-sized kite of conventional type could be used according to the present invention it is preferred to adapt a conventional kite of the above-described frame type for use as a sea anchor by replacing the original bridle with attachment means which are maintained in a fixed position in relation to the vanes. Such attachment means preferably take the form of a rigid structure comprising a towing bar positioned parallel to, and forwardly of, the top (horizontal) vane. A pennant is detachably connectable to each side of the attachment means, conveniently at an adjustable position on the tow bar. The free ends of both pennants may be connected to the outer end of a single towing line.

Alternatively, a conventional kite may be adapted by providing a greater number of attachment points for the bridle in order to resist effectively any tendency to rotation, six being the preferred number. The points may be positioned one at each corner, one at the mid-point of the top and one in a central position.

It is preferred, in a sea anchor according to the present invention that the vertical frame members diverge in a direction away from the bridle or attachment means. The directional stability of a kite may be increased by extending the side (vertical) members rearwardly, preferably in the same plane as the side members, thus providing a fin rearwardly of each side member.

Other arrangements for providing fins could of course be adopted, and the fins need not necessarily be positioned aft of the frame.

Preferably again the bottom vane is heavier than the other vanes to impart greater stability to the kite in its normal, vertical attitude.

Furthermore, the cross-sectional curvature of the vanes is desirably greater than that of a conventional multi-vane kite, there preferably being a change in angle of at least 30 over each vane; also the angle of inclination of the vanes to a plane normal to the height direction of the kite is preferably less than the previously-mentioned 250 found in the known naval kites.

A vessel which -suffers irreparable damage to her steering gear when at sea is clearly imperilled without some form of emergency steering gear.

According to a further aspect of the present invention there is provided emergency steering gear for a vessel comprising a sea-anchor, port and starboard lines connected to the anchor each line being led, preferably through a guide, to adjustment means for adjusting the length of each line. The adjustment means may take the form of, for example, a tackle or sheet winch, and by hauling on one of the lines the stern is displaced with respect to the direction of travel thus enabling the vessel to be steered. Preferably, the sea anchor is one having great directional stability, for example a kite, and most preferably a kite according to the present invention. If a kite having a flexible bridle is used the port and starboard lines are connected to a single towing line at a point outboard of the stern of the vessel.If the kite has rigid attachment means according to the present invention, then the port and starboard lines may be longer and connected to the attachment means, desirably through pennants.

According to a further aspect of the present invention there is thus provided a method of steering a vessel comprising towing a sea anchor from the stern of a vessel and laterally displacing the effective point of attachment of a single towing line to the stern or altering the relative lengths of a pair of towing lines.

The invention thus provides not only a very effective sea anchor but one which can easily be adapted to serve as an emergency steering gear.

According to a yet further aspect of the present invention there is provided a kite in which all the horizontal members (including the top and bottom members) are vanes which are upwardly inclined in the rearward direction.

Although the invention may be carried out in a variety of ways, one particular embodiment thereof is now described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is an elevation of the stern of a boat trailing a sea anchor, according to the invention; Figure 2 is a perspective view, at enlarged scale, of the sea anchor shown in Figure 1; Figure 3 is a plan of the sea anchor shown in Figure 2; Figure 4 is a section along the line III-III in Figure 3; and Figure 5 is a plan of the boat and sea anchor shown in Figure 1, rigged to function as an emergency steering mechanism.

In Figure 1, there is shown a vessel 10, adrift under storm conditions on the sea 11, and having a winch 12 from which towing line 13 passes round a post or eye 14 to a sea anchor in the form of a kite 15. The line 13 is connected to the kite 15 by a rigid attachment structure 16, to be described later.

The kite 15 shown in more detail in Figures 2, 3 and 4 is fabricated from sheet aluminium, stainless steel, other protected and proofed metal, or reinforced plastic; and includes a rigid rectangular peripheral frame formed of flat side panels 17,18 and top and bottom vanes 19,20. The side panels 17,18 are rearwardly divergent at an included angle which is preferably around 380, but which can depart from this value within the scope of the invention.

The top vane 19 and double-thickness bottom vane 20 are parallel and curved upwardly towards the rear of the kite 15, having a camber angle between tangents at the front and rear edges of typically 30, but are not limited to this value.

Two intermediate vanes 21,22 are fastened within the peripheral frame, equidistant from and parallel to the vanes 19,20.

It will be seen that the peripheral frame constitutes a flow passage which is divergent from entry to exit, particularly in the vertical dimension. This divergence promotes lateral stability of the kite 15.

A rod 23 is fastened through the centres of the curved vanes 19,20,21,22 and has its upper end drilled at 24 to provide an attachment point for a lifting line (not shown). The attachment structure 16 projects forwardly of the peripheral frame and comprises a pair of upper struts 26 and a pair of lower struts 27 bolted at their points of intersection to the respective ends of a horizontal towing bar 28 drilled with a series of holes 29. Two wire strops 30 are each connected at one end to selected holes 29 by a ring 31 and at their other ends (not shown) to the towing line 13.

For steering purposes each is connected to a separate rudder line as will be described later. For fine adjustment a short strop may be run from the free end of strops 30 to one of the other holes 29.

In a modification each side panel 17,18 is formed as shown in chain-dotted line in Fig. 2 with an integral rearward extension or fin 32,33 respectively, which gives improved directional stability.

Being made of heavy material, the kite 15 will tend to sink and will be urged to the upright orientation shown in the drawings by the relative weight of the bottom vane 20 which is of double thickness. Furthermore, the curvature of the vanes 19,20,21,22 will initially hasten the sinking, as the kite 15 is pulled through the water. However, as the latter sinks, the downforce on the vanes 19,20,21,22 will eventually achieve equilibrium with the upward component of the force exerted by the towing line 13, thus stabilising the depth at which the kite 15 operates for a given speed of the vessel 10 in the sea 11. The depth at a given speed can be adjusted by adjusting the length of the towing wire or rope 13.

When the kite 15 is to be used simply to retard and steady the vessel 10, the single line 13 is towed centrally, as shown in Fig. 1. However, as shown in Fig. 5, an emergency steering mechanism can be rigged by attaching two rudder lines 34 to the towing bar 28, the rudder lines 34 each being led through a block 35 on the quarter to a sheet winch 36. By winching in, for example, the starboard line 34 as shown, the kite 15 is caused to steer to starboard, thus causing the vessel to be turned to port.

It is not in fact necessary for the rudder lines 34 to be led over the respective quarters but they may be led through a single fairlead, which is convenient for example in the case of canoe-sterned vessels.

Although the kite 15 is rigid when in use, it may be constructed so that it can be collapsed or dismantled for ease of storage.

Claims (20)

1. A method of deploying a sea anchor from a vessel characterised in that the sea anchor is a kite.

2. A method as claimed in Claim 1, in which the kite is veered from the bow of the vessel or streamed from the stern of the vessel.

3. A kite for use as a sea anchor or as part of an emergency steering gear and having improved resistance to rotation, the kite comprising side members (which in use assume a generally vertical attitude) connected

by vanes of the curved cross-section, the concave faces of the vanes facing upwardly and slightly forwardly, and a bridle attached to the side members, characterised in that the bridle has more than four attachment points to the frame and/or is formed as a rigid structure.

4. A kite as claimed in Claim 3, in which the rigid structure includes a tow bar extending parallel to the vanes.

5. A kite as claimed in Claim 4, in which the tow bar provides a selection of attachment points.

6. A kite for use as a sea anchor or as part of an emergency steering gear and having improved resistance to rotation, the kite comprising side members which.

in use assume a generally vertical attitude connected by vanes of curved cross-section, the concave faces of the vanes facing upwardly and slightly forwardly, and a bridle attached to the side members, characterised in that the side members extend rearwardly of the vanes.

7. A kite as claimed in any one of Claims 3 to 6, in which the side members diverge in a rearward direction.

8. A kite as claimed in any one of Claims 3 to 7, in which the bottom vane is heavier than the other vanes.

9. A kite as claimed in any one of Claims 3 to 8, in which the angle of the vanes to a plane normal to the height direction of the kite is generally less than 250.

10. A kite as claimed in any one of Claims 3 to 9, in which the vanes have a camber angle between tangents at their front and rear edges of at least 30.

11. A kite as claimed in. any one of Claims 3 to 10 and which is at least partially collapsible or dis

mantled for ease of storage.

12. A method of steering a vessel comprising towing a sea anchor from the stern of the vessel and adjusting the relative drag exerted by the anchor on each quarter of the vessel.

13. An emergency steering gear for a vessel, comprising a sea anchor and port and starboard lines for connection at their inner ends to respective sides of the stern of the vessel and at their other ends to the anchor.

14. A steering gear as claimed in Claim 14, in which the lines are attached to horizontally spaced points on the anchor.

15. A method of deploying a sea anchor as claimed in Claim 1, substantially as herein described.

16. A kite as claimed in Claim 3 or in Claim 6 and substantially as herein described.

17. A method of steering a vessel as claimed in Claim 12 and substantially as herein described.

18. An emergency steering gear as claimed in Claim 13 and substantially as herein described.

19. A kite for use as a sea anchor or as part of emergency steering gear, substantially as herein described with reference to the accompanying drawings.

20. The features as herein described, or their equivalents, in any novel selection.