GB2098948A

GB2098948A - Reefing a tethered sail for marine or other use

Info

Publication number: GB2098948A
Application number: GB8214704A
Authority: GB
Original assignee: BP PLC
Current assignee: BP PLC
Priority date: 1981-05-21
Filing date: 1982-05-20
Publication date: 1982-12-01

Abstract

A spar-less elevated sail is controlled by encircling the shroud lines of the sail with a reefing ring 9 attached to a rigid spar or snuffing stick 8. The spar is attached to the flying lines 5 of the sail whereby operation of the flying lines causes the spar reefing ring assembly to move so as to cause the shroud lines to separate or be drawn together thus opening or drawing in the canopy. <IMAGE>

Description

SPECIFICATION Elevated sails and their control The present invention relates to elevated sails and more particularly to the deployment of elevated sails for the propulsion of water going vessels.

The ever increasing cost of energy particularly in the form of increasing oil prices have led to renewed interest in the total or partial propulsion of water going vessels such as cargo ships, tankers and yachts by use of wind energy. In particular, elevated sails or kites which have been proposed and used for the propulsion of ships have certain advantages over, say, vessel mounted sails. These advantages include the ability to fly at an altitude where the winds are generally strong and stable.

The present invention relates to improved means for the control of elevated sails suitable for use in the total or partial propulsion of water going vessels. By the term sail it is intended to include elevated sails and any tethered flying surface.

Thus, according to one aspect of the present invention, there is provided an elevated sail assembly comprising a sail having a plurality of shroud lines attached around the periphery of the canopy, a flying line for the sail, means for drawing the shroud lines together attached to the flying line, the-drawing means being remotely operable, the drawing means comprising a ring capable of encircling the shroud lines, the openable ring being attachable by a rigid member to the flying line.

The invention also includes a method of controlling a spar-less sail comprising the steps of (a) encircling the shroud lines of the sail with means for drawing the shrouds together (b) connecting the drawing means through a rigid member to the flying lines and (c) operating the flying lines so as to cause the drawing means to allow the shroud lines to separate or be drawn together and thus opening or drawing in the canopy.

Elevated sails may also be used to provide aerial platforms to lift equipment for photography, surveying, air pollution monitoring, gas sampling, crop spraying, radar operation or communications. Where the loads to be supported exceed, a weight of several kilograms the sizes of the sails then required can result in line forces in excess of those readily manhandled.

The invention will now be described by way of example only with reference to Figures 1 to 6 of the accompanying drawings.

A vessel 1 is fitted with qgpair of winches 2. A sail 3 of the lifting or ascent parachute type is launched from the vessel 1 by means of, e.g. a compressed air launch gun (not shown). The sail 3 carries a flying block 4 (pulley system) over which pass twin flying lines 5 which pass around turning blocks 6 and which are connected to the winches 2. The sail 3 can then be let out or handed in by appropriate operation of the winches 2, (Figure 1).

When the sail 3 is to be reefed, a snuffing stick is fitted to the flying lines, for example, by tying a short piece of line 7 or by operating a clamp system. The snuffing stick comprises a spar 8 to which a line is attached, the head of the spar 8 carrying a reefing ring 9 of internal diameter just greater than that of the flying block 4. The reefing ring 9 carries a gate 10 enabling the ring 9 to be opened or closed, (Figure 2). The gate 10 on the ring 9 is opened and the ring 9 moved over the flying lines 5, (the ring towards the sail). The gate 10 is then closed and the short line 7 which has been previously fixed to the lower end of the spar 8 is tied with, for example, a rolling hitch knot, to one of the flying lines 5.By appropriately using the winches 2 to pay out one of the flying lines 5 and reel in the other, the snuffing stick can be caused to move along the flying lines 5. The reefing ring 9 can pass over the flying block 4, progressively drawing in the shroud lines 11 to thereby reef and deflate the parachute sail system 3. The reverse procedure may be used to unreef the kite, (Figure 3).

The reefing ring is desirably smooth with a fair shape so as to avoid under friction and chafe on the lines. The snuffing stick may be a single spar or tube or multiple spars or tubes so as to give strength in compression to push the ring up along the shroud lines typically up to 25% of the total line tension. Additional rings, each with a gate, may be fitted on the snuffing stick to resist bending forces. Alternatively an opening or hinged tube may be used as the reefing ring. The reefing ring or tube may be made without a gate system, the snuffing stick being permanently located around the flying lines in use.

In certain applications the flying lines are used to control the direction of flight of the sail. For example, movement of the flying lines by means of winches can be used to operate wires attached to the vents or trailing edges of the sail thereby enabling control of the sail's direction and hence of the towed vessel to be obtained. In this case, paying out of the flying line by one winch and take up by the other winch to operate a snuffing stick would clearly involve loss of control of the sail direction and may even lead the sail to crash.

Thus a modification of the system to enable the flying lines to control both the said direction and said reefing is desirable and such a modification is described as follows.

In Figure 4, the flying lines 13 are connected between the flying block and the winches by means of two latching cleats 1 4 which are arranged to form a type of ratchet action. Thus, upon operation of the winches, line is allowed to pass down through the cleat 14 but is stopped when the line direction is reversed. Upon this line direction reversal occurring, any subsequent movement of the flying lines 13 causes the attached snuffing stick 1 5 to effectively "walk up" the line 13. By oscillating the flying wires over a short distance by means of the winches the ring 1 6 of the snuffing stick 1 5 can be made to walk up or down the flying wires and thereby reef or unreef the sail whilst leaving the sail control lines and hence the sail direction unaffected.It is desirable to oscillate the flying wires over only a short travel so as to cause minimum movement of the associated control wires and thereby avoid excessive flight direction deviation. By use of reversibly latching (jamming) cleats, the reefing operation may be reversed by remote control operation of the direction of the latching or ratchet mechanism. For example, by the use of optical, radio or other means.

In a second method of use of the snuffing stick or tube (Figure 5), the lower end of the snuffing stick 17 may be located on the vessel 18 and the parachute sail 19 flown on one or more lines 20 which pass from the winch 21 and up through the reefing ring to the flying sail 19. Upon operation of the winch to pull in the sail, the shroud lines 22 from the canopy are progressively reefed as they pass through the ring. If the snuffing stick 17 is longer than the distance from the flying block to the crown of the parachute canopy, upon retraction of the kite by use of the winch, the kite may be drawn into and stored within the tube or snuffing stick for storage and for subsequent redeployment (Figure 5a, b, c). Also the snuffing tube may be mounted through a universal joint onto the vessel so that it may point up the flying line. When the system is not required the tube may be laid on the deck or removed.

In sail applications where the twin flying line system cannot be used but where a source of power is available or extracted at the sail, the reefing ring may be driven up the shrouds to reef the sail by use of an extendable spar either under remote control from the operating vessel or automatically in response to line tension measurement. An example of such a device is shown in Figure 6. The spar 23 is driven through the actuator box 24 by a radio controlled electric motor (not shown) to force the reefing ring 25 up the shrouds 26 as required.

Claims

1. An elevated sail assembly comprising a sail having a plurality of shroud lines attached around the periphery of the canopy, a flying line for the sail, means for drawing the shrould lines together attached to the flying line, the drawing means being remotely operable, the drawing means comprising a ring capable of encircling the shroud lines, the ring being attachable by a rigid member to the flying line.

2. An elevated sail assembly according to claim 1 in which the ring is openable.

3. An elevated sail assembly according to claim 1 or claim 2 in which the shrould lines are attached symmetrically around the periphery of the canopy.

4. An elevated sail assembly according to any of the preceding claims in which the shroud lines are attached to the flying line by a pulley and block or the like.

5. An elevated sail assembly according to any of the preceding claims in which the rigid member is a wooden or metal spar.

6. An elevated sail assembly according to any of the preceding claims in which the flying line is attached to a winch.

7. An elevated sail assembly according to any of the preceding claims in which the rigid member is attached to the flying line by a short line.

8. An elevated sail assembly according to any of the preceding claims in which the length of the rigid member is the same as the length of the shroud lines.

9. An elevated sail assembly according to claim 4 in which the rigid member of the drawing means is attached to the flying lines by means of a ratchet mechanism whereby movement of the lines over the pulley causes the drawing means to be moved up or down the shroud lines.

10. An elevated sail assembly according to claim 9 in which the ratchet mechanism comprises a pair of latching cleats attached to the flying lines.

11. An elevated sail assembly according to any of the preceding claims in which the drawing means is remotely operable by optical or radio controlled means.

12. An elevated sail assembly as hereinbefore described and with reference to Figures 1 to 6 of the accompanying drawings.

13. A vessel whenever fitted with an elevated sail assembly according to any of claims 1 to 12.

14. A method of controlling a spar-less sail comprising the steps of (a) encircling the shroud lines of the sail witch means for drawing the shrouds together (b) connecting the drawing means through a rigid member to the flying lines and (c) operating the flying lines so as to cause the drawing means to allow the shroud lines to separate or be drawn together and thus opening or drawing in the canopy.

1 5. Methods of controlling elevated sails as hereinbefore described and with reference to Figures 1 to 6 of the accompanying drawings.