AEROFOILS FOR FLOATING VESSELS

Abstract: An aerofoil structure for wind propulsion of a ship or boat characterised by a carrier angularly movable about an upright axis on the ship or boat, a forward aerofoil set comprising at least one main upright aerofoil member, a rear aerofoil set comprising at least one upright aerofoil member, there being at least three aerofoil members altogether, both sets being supported directly or indirectly on the carrier, at least one of the sets being movable relative to the carrier between first and second positions, such that in each said position the forward end of the member, or at least one member, of the rear set is positioned adjacent the rear end(s) of at least one member, or the member, of the forward set, so that at least one cambered aerofoil is defined, the aerofoil(s) so defined in the first position being cambered in the opposite sense, and being defined by different members of at least one of the sets, from the aerofoils so defined in the second position.

Description: "AEROFOILS FOR FLOATING VESSELS" This invention relates to aerofoils for floating vessels and more particularly to aerofoil propulsion of ships and boats and to aerofoil structures which may be used for this purpose. The aerofoil propulsion may assist engine propulsion, and may also have the beneficial, and fuel saving effect of improving a ship's motion- German Patent No 403 416 discloses a system of parallel rigid sail areas rotatable together about a common axis. Rotation about the axis may be brought about by an artificial power source or using wind power and steering sails. In some embodiments (Figure 25) movable sail parts are pivoted at the rear ends of main sail parts so as selectively to allow creation of a partial vacuum on one side or the other. German Patent Specification No 1 531 655 discloses use of sets of symmetrical rigid sails which are pivotally mounted and adapted to present similar effects regardless of which edge leads into the wind. According to the present invention, there is provided an aerofoil structure for wind propulsion of a ship or boat characterised by a carrier angularly movable about an upright axis on the ship or boat, a forward aerofoil set comprising at least one main upright aerofoil member, a rear aerofoil set comprising at least one upright aerofoil member, there being at least three aerofoil members altogether, both sets being supported directly or indirectly on the carrier, at least one of the sets being movable relative to the carrier between first and second positions, such that in each said position the forward end of the member, or at least one member, of the rear set is positioned adjacent the rear end(s) of at least one member, or the member, of the forward set, so that at least one cambered aerofoil is defined, the aerofoil(s) so defined in the first position being cambered in the opposite sense, and being defined by different members of at least one of the sets, from the aerofoils so defined in the second position. With the invention, there are forward and rear sets of aerofoil members. While each set need only have one member, there must be at least three members altogether and in preferred embodiments one set, preferably the forward one, has one more aerofoil member than the other set. A particularly suitable arrangement has three members in the forward set and two in the rear set. One or both sets is movable between first and second positions, in which members from the two sets come together to define cambered aerofoils. In the two positions, the camber is in the opposite sense and, to some extent, different ones of the aerofoil members are involved. For instance, to take the simplest case, where one set has one member and the other set has two, the one member combines alternatively with the two members. In the example of three members in the forward set and two in the rear, the two rear ones combine with different .pairs of members in the front set. Generally, all the members of the rear set will combine with members of the front set in both positions, but it is possible for members to remain uncombined, though in that situation they are of relatively little use. The combined members preferably create a slotted aerofoil structure, with a slot between the members. This improves the effect of the aerofoil, by allowing air to flow through the slot from the high pressure, concave, side to the low pressure convex, side of the aerofoil, where it reenergises the boundary layer, keeping the boundary layer moving and remaining attached to the aerofoil surface which is a necessary condition for lift. Thus with the invention, the camber of the combined aligned, front and rear aerofoil members is of opposite hand for the two positions and provide "mirror image" conformations permitting sailing on either tack. Normally, each aerofoil member of each set should be symmetrical about its median plane unless particular performance is required on one tack. By the term "wind propulsion" is contemplated both wind assistance and, conceivably, propulsion by wind alone. Further, since both sets of aerofoils are carried directly or indirectly by the angularly movable carrier, the array of aerofoil members will always lie within an envelope surface of revolution centred on the axis about which the carrier can be turned. .This envelope will be ^ cylindrical, if full rotation is considered. The aim will be to maximise lift for a given diameter of cylinder, thereby reducing the deck area and airspace which is blighted by the aerofoil structure. Preferably, the or each main aerofoil member of the forward set has a tail flap pivotally mounted about an axis which is adjacent the leading edge of such tail flap and adjacent the trailing edge of the main aerofoil member. Such tail flaps can be used to change the camber of the aerofoil. They can also be used to re-energise the boundary layer by defining a slot with the main member. The tail flaps can be of relatively thin aerofoil section as compared with the main aerofoil members, and each surface of the flap forms a substantially continuous extension of the corresponding surface of the main aerofoil member in the respective one of the two said positions. Small additional aerofoils may be provided at the rear edges of the forward set of aerofoils, so that they form flaps to such aerofoils aftd improve boundary layer regeneration and lift. In one form, such small additional aerofoils are mounted on arms attached to the rear portions of the tail flaps just described where these are provided. Otherwise they can be mounted on the main aerofoil members. In another form the small additional aerofoils are rearward of such tail flaps and supported by the main aerofoil members. In such cases, when the forward aerofoil(s), including the tail flaps, where provided, and small additional aerofoils, combine with aerofoils of the rear set to create combined cambered aerofoils there are, therefore, two slots in the combined aerofoils, by which reenergisation of the boundary layer on the low pressure side can be effected, these slots being firstly between the main aerofoil (or tail flap) and the small additional aerofoil, and secondly between the small additional aerofoil and the leading edge of the aerofoil member of the rear set. In place of, or possibly in addition to, the provision of the small additional aerofoils at the rear ends of the forward aerofoils, small additional aerofoils may be mounted at the leading edges of the rear aerofoils, and thereby act as slats to such aerofoils, again for the purpose of providing slots via which the boundary layer can be reenergised and, again, by which one slot of a double slotted combined aerofoil can be provided, the other slot being between such slat and the rear edge of the member of the forward set, or a tail flap thereon. Preferably, the structure has a pair of small aerofoils adjustably positioned near the leading or trailing edge of a larger aerofoil member of the forward or rear set, also to improve air flow re-energization and lift. Each such small aerofoil may have its own flap, being a member pivoted to its trailing edge. These adjustble small aerofoils are to relieve pressure on the leading edge which might otherwise lead to stalling, and thus allows operation at higher angles of incidence. There may also be, on at least one of the aerofoil members, a symmetrical leading edge and a modifying device therefor comprising a nosing contiguous to the leading edge and which can be moved between positions on opposite sides of the median plane of the leading edge. Certain embodiments may have, at the trailing edge of at least one aerofoil member, a wedge shaped flap, movable from side to side so as to assist generation of upward lift on alternate sides of the aerofoil member. This may act as a plain tail flap on a main member of the forward set in place of the pivotted tail flaps already described and can also be used with the small additional flaps. Where the aerofoil structures of the invention are used for the propulsion of a ship or boat, it is highly advantageous that the movable aerofoil members are securable in a neutral mid position both for engine powered propulsion into a head wind and when hove-to in high winds. In use, the aerofoil angles of incidence to the wind will be governed by actuators on the basis of sensed wind and ship motion. In order that the invention may be more clearly understood, the following description is given, by way of example only, with reference to the acς mpanying drawings, which represent the position where the wind blows from left to right, and in which:- Figure 1A is a plan view of an aerofoil assembly in its neutral position for facing into a wind coming from the left; Figure IB shows the aerofoil assembly of Figure 1A adjusted to generate a positive lift towards the top of the Figure; Figures 2A and 2B, and Figures 3A and 3B are views similar to Figures 1A and IB respectively of alternative constructions; Figure 4 is a sectional view showing a modifying element for the leading edge of a thick aerofoil; Figure 5A is a view similar to Figure 4 of a different arrangement for modifying the leading edge of an aerofoil, in a neutral disposition; Figure 5B shows the device of Figure 5A in one operative position; Figures 6 and 7 show two alternative bracing arrangements for use in Figures 1 to 3 as seen in side elevation; Figures 8A and B, and 8C and D, and 8E and F show three alternative trailing edge constructions for aerofoils; and Figures 9A and 9B are respectively a schematic view and a more detailed partial schematic view of the provision of a slat at the leading edge of a rear aerofoil. The aerofoil assembly shown in Figures 1A and B comprises a circular carrier base 1 which in use is supported by means of a turntable bearing arrangement on the hull of a ship with its axis vertical. There may be computer-controlled driving means for moving the base angularly about the axis to the required position in relation to the wind and the direction of the ship movement. A carrier comprising an upright support from which other parts of the assembly depend can be employed in place of the circular carrier base shown. Mounted on the base 1 is a forward array of fixed, relatively thick, aerofoil members comprising, in this case, main aerofoil members comprising a central aerofoil 2 and two outer aerofoils 3A and 3B although other numbers of main aerofoils in this forward array may be contemplated. Each of the main aerofoil members 2 and 3 is symmetrical about its median plane. The main aerofoils 2 and 3 are interconnected by an appropriate bracing structure indicated by broken lines 4 to provide the necessary rigidity, examples of this being more fully described below in connection with Figures 6 and 7. As indicated in the case of the aerofoil member 2, the aerofoil members 2 and 3 may be reinforced by structural elements such as tubes 5. Hinged to the trailing edge of each of the main forward aerofoil members 2 and 3 is a relatively thinner tail flap 6, 7A and 7B. In the neutral position shown in Figure 1A, each lateral surface of the tail flaps 6 and 7 makes an obtuse angle with the corresponding lateral surface of its associated main aerofoil 2, 3. The vertical pivotal axes of the tail flaps 6 and 7 are shown at 8 and 9 respectively, being at the rear edges of main forward aerofoil members 2 and 3 and at the front edges of tail flaps 6 and 7. Two small additional aerofoils 10A and 10B are pivotally mounted on arms 11A and 11B which are attached on opposite sides of the rear portion of the tail flap 6. In a similar way, respective further small additional aerofoils 12A and 12B are connected by arms 13A and 13B to the tail flaps 7A and 7B. These improve lift by providing slots which cause boundary layer re-energisation. To cooperate with the forward set of aerofoil members including in this case the main aerofoils and their tail flaps and additional small aerofoils, there are provided two rear aerofoil members 14A and 14B. These are pivoted near their leading edges to the rear ends of respective arms 15A and 15B which are in turn pivoted to the base structure 1 about axe ' s 16A and 16B. The assembly of rear aerofoil members 14 can adopt a neutral position as shown in Figure 1A, in which the rear members are restrained, and is movable to two operating positions in which the rear members 14A and 14B are aligned with different members of the front set, such movement being " brought about by pivotting of arms 15A and 15B about axes 16A and 16B and pivotting of the rear aerofoil members upon those arms. In an operative position, one of which is shown in Figure IB, the aerofoil members adopt and are restrained in an essentially triplane configuration. The aerofoil elements 3B, 7B, 12B of the front set and the rear element 14B, form a doubly slotted wing of high camber. The upper, surfaces of the members 3B and 7B merge smoothly, thereby reducing centrifugal accelerations in the boundary layer flow passing over the junction between the members 3B and 7B. The slots between the elements 7B and 12B, and 12B and 14B ensure boundary layer re-energisation. The middle wing of the triplane is formed by the elements 2, 6, 10A of the forward set and the other rear element 14A, again with boundary layer re-energisation through the slots on each side of the element 10A and further enhancement by the element 10B. Here again the outer surfaces of the elements 2 and 6 merge smoothly. The 'third wing of the triplane arrangement is formed only by the forward elements 3A and 7A (the outer surfaces of which again merge smoothly) and 12A. It will be appreciated that the elements can be adjusted to the mirror image formation to that shown in Figure IB, in which one wing will be formed only by the elements 3B, 7B and 12B of the forward set, the central wing will now be formed by the elements 2, 6, 10A, 10B and 14B and the third by the elements 3A, 7A, 12A and 14A. As mentioned above, the entire assembly can be moved angularly about the central axis A by angular movement of the base 1. In all such angular positions of the base 1, and all relative positions of the aerofoil members, all of the aerofoil elements lie within an imaginary cylinder here of radius equal to that of the base 1. Figures 2A and 2B show a simpler form of aerofoil assembly. In this arrangement, relative to that shown in Figures 1A and IB, the small additional aerofoils 10A and 10B and 12A and 12B downstream of the tail flaps, 6, 7A, 7B, are omitted from the first set. The aerofoils 14A and 14B are pivotally mounted on a triangular frame 21 which is itself pivoted to the base 1 at 22 in the region of the leading edge of the aerofoil 2. In use of this aerofoil assembly, as shown in Figure 2B, actuators turn the frame.21 and flaps 6, 7A, 7B, 14A and 14B to the positions shown in Figure 2B. On this tack, the element formed of members 3B, 7B and 14B forms one slotted plane, the element formed of members 2, 6 and 14A forms a second slotted plane and the elements formed of members 3A and 7A forms a third cambered plane. On the opposite tack, the member 14A forms a cambered slotted plane with the members 3A and 7A as does the member 14B with the members 2 and 6. Another arrangement, shown in Figures 3A and 3B, retains the central main aerofoil member 2 and flap 6, but the outer main members 33A and 33B of the forward set are not provided with tail flaps. The frame 21 is replaced by a bracing arrangement 31 which is fixed relative to the turntable base 1 and supports pivots for the aerofoil members 14A and 14B. For alternative alignment, main members 33A and 33B are carried on outrigger frames 32A and 32B attached to pivoted tail flap 6. In operation, on one tack, as shown in Figure 3B, the aerofoil elements 33B and 14B form one slotted cambered plane while the elements 2, 6 and 14A form a central cambered and slotted plane. On the opposite tack, the central plane is formed by the elements 2, 6 and 14B while the other plane is formed by the aerofoil elements 33A and 14A. Figure 4 shows a leading edge device which may be applied to the leading edge of an aerofoil such as that shown at 41 to increase lift. Pivoted to the leading eclge is a symmetrical nosing 42, the concave surface of which substantially conforms to the convex leading edge 43 of the aerofoil 41. The nosing 42 is mounted on arms 44 which are pivoted to the aerofoil 41 on ' a pivot axis 45 which forms the axis of curvature of the central portion of leading edge 41. The assembly formed by the nosing 42 and arms 44 can be swung from the lower position shown in Figure 4 and in which it provides positive upward lift, through a central position of zero incidence with the arms 44 coinciding with the median plane 46, providing zero lift, to a mirror image position (relative to the plane 46) to that shown in Figure 4, to provide negative upward lift as seen in the Figure. Figures 5A and 5B show another leading edge device. This may be provided alone or used in conjunction with the device shown in Figure 4. As can be seen in Figure 5A, a fixed frame or arm 51 projects forwardly from the leading edge 52 of the aerofoil 53. A beam structure 54 is pivoted at its mid point to the leading edge of the arm or frame 51 and supports a small aerofoil 55A, 55B at each end. Each of the aerofoils 55A, 55B preferably has hinged to it a relatively thin tail flap 56A, 56B to form an assembly resembling that formed by the aerofoil members 2 and 6 in Figure 1. Figure 5B shows the operating position for generating upward lift (as seen in the Figure) . The beam structure 54 has been turned relative to the arms 51 and the aerofoils 55A * and 55B have been turned relative to the beam structure 54 while the flap 56A has been turned relative to the aerofoil member 55A. The neutral position is shown in Figure 5A and there is a mirror image position for that shown in Figure 5B to provide downward lift. Figure 6 shows in vertical elevation one conventional form of bracing which may be provided between the aerofoil members 2 , 3A and 3B which are fixed to the turntable base 1 in Figures 1 and 2. This takes advantage of the stagger between the central aerofoil member 2 and the aerofoil members 3 to form the bracing indicated at 4 in Figures 1 and 2. In addition to the vertical columns formed either by tubular columns 5 within the aerofoil members or by appropriate structural design of the aerofoil members themselves, such as the member 3 shown in Figure 6, the bracing comprises horizontal struts 61 interconnecting the elements 5 and 3 and capable of withstanding loads in compression, and ties 62 for example formed by tensioned cable. In an alternative construction shown in Figure 7, where the column 5 and structural aerofoils 3 are capable of withstanding bending moments, the bracing comprises vertically spaced inclined struts 71 fixed, for instance by welding, to the columns 5 or appropriate portions of the aerofoil members. At their upper ends, the members 3 and 5 can be interconnected by a horizontal frame or strut 72. Figures 8A, C, E show three forms of trailing edge for aerofoils with reversible slotted flaps, useful as alternatives to the pivotted plain tail flaps such as 6, 7A, 7B. In the arrangement shown in Figures 8A and B, the trailing edge of an aerofoil 80 is formed by a pair of members 81A and 81B of generally J-cross section, that is to say comprising a semi-circular part with a generally straight part extending from one end of the semi-circle, pivoted about axes 82A and 82B. In the neutral position shown in Figure 8A, the straight parts of the members 81A and 81B form continuations of the surfaces 80A and 80B of the aerofoil member 80. In one operative position shown in Figure 8B, the member 81A has been swung towards the axis 82B while the member 81B remains in the same position. In the mirror image position for the opposite tack, the member 81A will be in the position shown in Figure 8A while the member 8IB will be swung down towards the member 81A. To provide a double slotted flap arrangement when a rear aerofoil combines with the front one, a further flap 82C is pivoted to the main member rearwardly of members 81A and 81B to be swung into alignment with whichever member is in the operative position. Such an arrangement would be particularly helpful in, for instance, the Figure 2 and 3 embodiments e.g. in place of flap 6. The members 81A and 81B can also be shaped to offer an essentially smooth surface for the flow past them, eg. through the slot which they can define with the flap 82C. The arrangement shown in Figures 8C and 8D may be used either as an alternative to the arrangement in Figures 8A and 8B or to provide a connection between a front aerofoil member (such as the members 2 or 3 in Figures 1 and 2) and a thin tapered tail ' flap (such as the members 6 and 7) . A relatively thin wedge-shaped tail flap 83 is connected to the trailing edge face 84 of an aerofoil 80 by a quadrilateral articulation comprising strips 85A and 85B hinged at 86 and 87 to the members 80 and 83 respectively. Figure 8C shows the neutral position of the assembly while Figure 8D shows the cambered position for assisting the generation of upward lift as seen in the Figure, where the upper surfaces of the aerofoil member 80 and 83 and the strip 85B form an effectively continuous surface. The hinges 86 and 87 may be of the flexure type, i.e. involving a thinner zone of material between integral thicker parts thereof, the outer surface of the tail flap being continuous. In the arrangement shown in Figure 8E and 8F, the flap 88 is again wedge-shaped and is here pivoted on an axis 89 (by means of suitable outriggers from the aerofoil 80) at its extreme rear edge. The rear face 84 of the aerofoil 80 is arcuate (centred on the axis 89) and the surfaces 80A and 80B of the aerofoil 80 can be continued at 90A and 90B for a short distance to shield the leading edge of the element 88 so as to form a continuous upper surface when in the position shown in Figure 8F. Improved performance may be obtained by the- provision of a slat at the leading edges of the aerofoils of the rear set, such as the aerofoils 14A, 14B of any of Figures 1, 2 and 3 as well as, or instead of, the trailing edge arrangements for the forward set of aerofoils just described. Such additional leading edge slat is preferably pivotally mounted on an axis forward of the leading edge of the rear aerofoil, for instance on an axis supported by external ribs extending forwardly from the rear aerofoil. The slat defines a slot with the front end of the rear aerofoil and thereby improves lift by regeneration of boundary layer flow. Desirably, the slat is in two parts, one pivoted to the other, so as to provide a double slotted flap. Essentially, the same arrangement could be used with the forward aerofoil set. Figure 9A schematically shows such additional slat 100 forward of a rear flap 14 and rearward of a forward flap. Figure 9B more clearly shows the flap 100 to be mounted on a pivot axis 101 on a looped rib 102 extending forward of the rear aerofoil 14. There may be a number of such ribs spaced along the leading edge of the rear aerofoil. The flap 100 is movable within the loop, either freely rotatable or powered. At the rear end of slat 100 is a freely pivoted second slat 103, allowing camber modification. This or a similar arrangement can be applied to any rear aerofoil, particularly though not exclusively those of Figures 3 and 2, in order to give a double slotted arrangement when the rear aerofoil including the forward slat 100 is aligned with an aerofoil of the forward set. In addition such an arrangement can be applied to any front aerofoil to give a slat allowing a higher angle of incidence, and increased lift, ' before the aerofoil stalls.

Claims: C L A I M S 1. An aerofoil structure for wind propulsion of a ship or boat characterised by a carrier angularly movable about an upright axis on the ship or boat, a forward aerofoil set comprising at least one main upright aerofoil member, a rear aerofoil set comprising at least one upright aerofoil member, there being at least three aerofoil members altogether, both sets being supported directly or indirectly on the carrier, at least one of the sets being movable relative to the carrier between first and second positions, such that in each said position the forward end of the member, or at least one member, of the rear set is "positioned adjacent the rear end(s) of at least one member, or the member, of the forward set, so that at least one cambered aerofoil is defined, the aerofoil(s) so defined in the first position being cambered in the opposite sense, and being defined by different *' members of at least one of the sets, from the aerofoils so defined in the second position. 2. An aerofoil structure according to claim 1, characterised in that the or each said cambered aerofoil is slotted in the region where the aerofoil members which it comprises are adjacent each other. 3. An aerofoil structure according to claim 1 or 2, characterised in that the or each main aerofoil member of the forward set has a tail flap pivotally mounted about an axis which is adjacent the leading edge of such tail flap and adjacent the trailing edge of the main aerofoil member. 4. A structure according to claim 1 or 2, characterised in that at the trailing edge of at least one aerofoil member, a wedge shaped flap is provided, movable from side to side so as to assist generation of upward lift on alternate sides of the aerofoil member. 5. An aerofoil structure according to claim 3, characterised in that the forward set of aerofoil members includes additional small aerofoils mounted on arms attached to the rear portions of said tail flaps to improve air regeneration and lift. 6. An aerofoil structure according to claim 3 or 4 characterised in that the forward set of aerofoil members includes additional small aerofoils rearward of the flaps and supported by the main aerofoil members. 7. A structure according to any preceding claim characterised by slats mounted at the leading edge of the forward or rear aerofoil(s). 8. An aerofoil structure according to any preceding claim, characterised in that the aerofoil members of said rear set are pivotally mounted on respective arms in turn pivoted to said carrier. 9. An aerofoil structure according to any preceding claim characterised in that the aerofoil members of said rear set are pivotally mounted on a frame, the frame being pivoted adjacent the forward end of the carrier base. 10. An aerofoil structure according to claim 1, characterised in that a central aerofoil member of the forward set of aerofoil members has a tail flap pivoted to its rear edge, and in that outer ones of the forward set of aerofoil members are mounted on a frame attached to said tail flap. 11. An aerofoil structure according to any preceding claim, characterised by a pair of small aerofoils adjustably positioned near the leading or trailing edge of a larger aerofoil member of the forward or rear set to improve air flow re-energization and lift. 12. An aerofoil structure according to any preceding claim, characterised in that at least one of the aerofoil members has a symmetrical leading edge and a modifying device therefor comprising a nosing contiguous to the leading edge and which can be moved between positions on opposite sides of the median plane of the leading edge.

Inventors: SATCHWELL CHRISTOPHER JOHN, SATCHWELL, CHRISTOPHER, JOHN
Applicants: UNIV SOUTHAMPTON, THE UNIVERSITY OF SOUTHAMPTON
Application year: 1986
Main classification: B63H9
IPC codes: B63H9