GB2098951A

GB2098951A - Launching a tethered sail for marine and other uses

Info

Publication number: GB2098951A
Application number: GB8214707A
Authority: GB
Original assignee: BP PLC
Current assignee: BP PLC
Priority date: 1982-05-20
Filing date: 1982-05-20
Publication date: 1982-12-01

Abstract

Launching of a skysail is achieved by initially launching a pilot kite 1 on a flying line 3 and attaching one or more elements 6, 7 of the skysail to the flying line. The flying line is then reeled out until the skysail elements are at suitable altitude. The elements of the skysail are then set. To prevent their surging, some or all of the elements 7 may by packed furled or reefed on the line(s) 3 prior to being set. Once set, the pilot kite 1 may be recovered or hauled into a stowage tube at the head of the stack of main sail elements. <IMAGE>

Description

SPECIFICATION Elevated sails 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 lead 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 stronger and more stable than those close to the ground.

Launching of large sails of the skysail type from the land is fairly straight forward, the sails being laid out along the ground and launched by exposing the leading edge of one element to the wind which lifts, the rest of the connected elements being raised in sequence. However, when launching these sails from a ship for the purposes of ship propulsion, there is usually insufficient space to spread out these large area sails. The present invention is directed towards overcoming this problem.

Thus, according to the present invention, there is provided a method of launching an elevated sail of the skysail type comprising the steps of (a) launching a pilot kite on one or more flying lines (b) attaching one or more elements of the skysail to the line of the pilot kite (c) paying out the line until the elements are at a suitable position and (d) causing the elements to become unfurled and flying.

By the term skysail is meant a kite of the general type described in GB Patents Nos 1 585099 and 2055049. The pilot kite is prefereably of the parachute type.

The invention also includes an elevated sail assembly comprising (a) a pilot kite (b) means for launching the pilot kite (c) a flying line capable of attachment to the pilot kite (d) an elevated sail of the skysail type (e) means for attaching the elevated sail to the flying lines and, (f) means for controlling the flying line.

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. There the loads to be supported exceed a weight of several kilograms the sizes of the kites then required can result in line forces in excess of those readily manhandled.

The invention will now be described by way of example only and with reference to figures 1 to 4 of the accompanying drawings.

Figure 1 illustrates the steps in one method of deploying an elevated sail of the skysail type. A pilot kite 1 of the parachute type is launched conventionally, e.g. by use of a compressed air driven launch gun from the deck of a water going vessel 2. The pilot kite 1 is controlled by flying lines 3 connected through turning blocks 4 connected to twin winches 5 (figure 1(a)).

Alternatively two pilot kites may be launched on two adjacent lines.

The flying lines 3 are then paid out until the position for the top main (skysail) sail element leaves the winch turning blocks 4. The first element 6 is attached to the flying lines 3 by tying or clamping. The flying lines 3 are then paid out further until the next element position is reached when the second element is attached. This process is continued until all elements are attached to the flying lines 3 and are remote from the vessel (figure 1(b)). A spreader spar 8 of length similar to the length of the main sail elements may be used to resist the compressive forces of a pair of flying lines to a single pilot parachute. To avoid the main sail elements surging on the flying lines which may result in breakage or tangling of lines, some or all of the elements 7 may be packed, furled or reefed on the lines 3.The reefing or packing of the sail elements is released and the pilot kite 1 recovered onto the vessel (figure 1(c)). To recover the skysail system, the above process may be reversed.

Figure 2 shows a second method of deploying the skysail in which the pilot kite 13 is flown with one flying line 9. One end of each of the main sail elements 10 are then attached to the flying line 9 while the opposite ends of the elements are attached to a slack flying line 11. As the tensioned flying line 9 is paid out, the elements 10 are lifted from the deck of the vessel 12 and hang downwind (figure 2). When all elements 10 are attached to both lines and well clear of the vessel, the second line 11 is rapidly tensioned to cause the stack of elements 10 to inflate and fly.

The pilot kite 13 is then recovered on the vessel 1 2 using subsidiary flying lines (not shown).

As an alternative to recovering the pilot kite or kites on the vessel, they may be packed into containers or tubes at the head of the stack of main sail elements reducing their drag due to windage but ensuring that they are readily available to stabilise the stack of kite elements for recovery. An example of this method is shown in figure 3. After the pilot kite 14 has been used to lift all main sail elements 1 5 from the deck and these are inflated the pilot control lines 1 6 are moved differentially to cause the pilot 14 to be drawn into one of the tubes 1 7 at the head of the stack. This pilot kite 14 is held in the tube 17 until required holding it down in the tube for recovery when the control line 1 6 is released and it is drawn out of the tube 17 assisted with tension on the second pilot control line.The extent of release of the control lines of the pilot kite 14 is restricted by the presence of stoppers 18 on the lines 16.

A further method of deploying elevated sails of the skysail type is shown in figure 4. A stable pilot kite 1 9 is deployed with twin flying lines 20 to à position clear of vessel turbulence. The flying lines 20 are then passed through rings 21 at the ends of the main sail elements 22 which are bunched together and held with low breaking strength cords 23 or bands while the uppermost elements of the kites is tied or clamped to the line 20. Each element 22 of the main sail stack is linked to its adjacent neighbouring element by short lengths 24 of main flying line 25. The lowest element is fixed to the main flying lines 25 which pass through turning blocks 26 and lead to the main winches 27.

The pilot flying lines 20 are then paid out and the main flying lines 25 kept slack by paying out on these simultaneously so that the bundle of skysail elements is lifted clear of the deck of the vessel.

The bundle is lifted to such a height by the pilot kite 19 that, when the main sail system is deployed the lowest element will be clear of and above the vessel. When the main sail system is required, the main flying lines 25 are tensioned to cause the lines 23 holding the bundle together to break and allow the elements to slide down the pilot flying lines 20 under control (figure 4(b)). As the elements 22 infiate and pull strongly, the pilot kite system recovered and the main sail system allowed to fly and pull the vessel.

To recover the main sail, the pilot kite 19 is reconnected to the top element of the skysail and the pilot lines 20 tensioned to cause the stack of elements 22 to be drawn down to the deck of the vessel whilst being controlled by the presence of the rings 21 through the pilot flying lines 20. The pilot kite 19 is then recovered.

Claims

1. A method of launching an elevated sail of the skysail type comprising the steps of (a) launching a pilot kite on one or more flying lines (b) attaching one or more elements of the skysail to the line of the pilot kite (c) paying out the line until the elements are at a suitable position and (d) causing the elements to become unfurled and flying.

2. A method of launching an elevated sail according to claim 1 in which the pilot kite is recovered or disengaged when the skysail is flying in a stable configuration.

3. A method of launching an elevated sail according to claim 1 or claim 2 in which the pilot kite is launched on a plurality of flying lines there being one or more furled elements of the skysail attached to the lines at pre-determined positions, there also being means for unfurling the elements of the skysail when the pilot kite is at a suitable altitude.

4. A method according to claims 1 to 3 in which the flying lines are paid out from winches.

5. A method according to any of the preceding claims in which the elements are tied or clamped to the flying lines.

6. A method according to any one of the preceding claims in which a bar is to connect the flying lines between the elements and the pilot kite.

7. A method according to any one of the preceding claims wherein a plurality of elements are packed together into a bundle each being attached at the ends to the flying lines of the pilot line, there being means for releasing the bundle when the kite is at a suitable altitude.

8. A method according to claim 7 in which the bundle is held together by low breaking strength cords of the like.

9. Method for launching elevated sails according to claim 1 or 2 in which the pilot kite is launched on a single flying iine, there being one or more furled elements of the skysail attached to and hanging down from the line at predetermined positions there also being a slack second flying line linking the pilot kite and the furled elements of the skysail and means capable of causing rapid tensioning of the second flying line whereby the elements are unfurled and inflate and fly.

1 0. Method for launching elevated sails according to claim 9 in which the pilot kite is recovered or disengaged subsequent to launch of the skysail.

11. Method for launching elevated sails as hereinbefore described and with reference to Figures 1 to 4 of the accompanying drawings.

1 2. An elevated sail assembly suitable for a vessel comprising (a) a pilot kite (b) means for launching the pilot kite (c) a flying line capable of attachment to the pilot kite (d) an elevated said of the skysail type (e) means for attaching the elevated said to the flying lines and (f) means for controlling the flying line.

13. An elevated sail assembly according to claim 12 in which the means for launching the pilot kite is a launch gun.

1 4. An elevated sail assembly according to claim 12 or 13 in which the elevated sail comprises a bundle of skysail elements.

1 5. An elevated sail assembly according to claim 14 in which the bundle is held together by low breaking strength cords.

16. An elevated sail assembly as hereinbefore described and with reference to Figures 1 to 4 of the accompanying drawings.

1 7. Vessels whenever fitted with an elevated sail assembly according to any of claims 12 to 16.