US3791329A

US3791329A - Lift structure

Info

Publication number: US3791329A
Application number: US00161443A
Authority: US
Inventors: P Bruning
Original assignee: ELECTRONIC MACHINING CO
Current assignee: ELECTRONIC MACHINING CO
Priority date: 1970-01-22
Filing date: 1971-07-12
Publication date: 1974-02-12
Anticipated expiration: 1991-02-12

Abstract

A lifting body in the general form of approximately a semicylinder is connected to the fuselage of an aircraft for providing lift during flight. The lifting surface is substantially free of camber and is concave on its lower face in a direction transverse to the flight direction so that with a small angle of attack a large volume of air is effectively trapped beneath the lifting body, and the side edges minimize loss of air laterally thereby providing lift over substantially all of the lifting surface. The lifting body has a length along the direction of flight greater than the width transverse to the direction of flight for providing a low aspect ratio. Conventional elevators and a rudder are provided for control. In another embodiment the lifting body is formed in a helical shape for acting in the manner of a propeller and in another embodiment a fuselage is integrally connected with the lifting body in an arrangement where the lifting body also has capacity for helium for lighter than air flight. In another embodiment the lifting body is provided along each side edge of a boat so as to provide lift as the boat moves through the water. In such an arrangement the lifting body is substantially continuously wetted and only incidental entrained air may be present on the convace lower face. In still another embodiment, a propeller incorporating principles of this invention has several lifting bodies arranged in a circular path for high thrust.

Description

ilnite States Patet 1191 Bruning 1 Feb. 12, 1974 [73] Assignee: Electronic Machining Company,

Pasadena, Calif.

22 Filed: July 12, 1971 21 Appl.No.:161,443

Related [15. Application Data [63] Continuation-impart of Ser. No. 4,796, Jan. 22,

1970, Pat. No. 3,653,609.

[52] US. Cl l14/66.5 R, 114/39, 114/61, 114/62, 416/189 [51] lint. Cl B63b l/20 [58] Field of Search l14/66.5, 67, 61, 62, 67 R, 114/67 A; 244/12 CW, 13, 35 R, 36, 40 R, 45, 48; 416/176, 189

Primary Examiner-Duane A. Reger Assistant ExaminerBarry L. Kelmachter Attorney, Agent, or Firm-Christie, Parker & Hale [57] ABSTRACT A lifting body in the general form of approximately a semi-cylinder is connected to the fuselage of an aircraft for providing lift during flight. The lifting surface is substantially free of camber and is concave on its lower face in a direction transverse to the flight direction so that with a small angle of attack a large volume of air is effectively trapped beneath the lifting body, and the side edges minimize loss of air laterally thereby providing lift over substantially all of the lifting surface. The lifting body has a length along the di' rection of flight greater than thewidth transverse to the direction of flight for providing a low aspect ratio.-

[56] References Cited Conventional elevators and a rudder are provided for UNITED STATES PATENTS control. In another embodiment the lifting body is 1,738 979 12/1929 Adelmann 114/61 x fomled in a helical Shape for acting the manner Of a 2,091Z677 3/1937 Fredericks 416/189 P am in another embodiment a fuselage is 2,645,436 7/1953 Brown 114/67 A x tegrally Connected with the lifting y in an arrange- 2,735,392 2/1956 Cox ll4/66.5 R merit where the lifting body also has capacity for he 3,051,250 8/1962 Jones 416/189 lium for lighter than air flight.

2/22 In another embodiment the lifting body is provided 1 3 5/1967 Dismukes". n 114,61 along each side edge of a boat so as to provide 11ft as 3,407,770 10/1968 Bailey 114/66.5 H the 1303* moves through the water In Such an 3,493,195 2 1970 Nelson... 244/12 arrangement the lifting y is Substantially 3,504,990 4/1970 Sugden 416/176 continuously wetted and only incidental entrained air 3,566,501 2/1971 Winchester... 416/176 may be present on the convace lower face. In still 3,653,609 4/1972 Bruning 244/13 h r embodiment, a propeller incorporating 1 L 12965 Allegra l14/66-5 H principles of this invention has several lifting bodies 3,584,590 6/1971 Rings et al. 114/61 arranged in a circular path for g thrust FOREIGN PATENTS OR APPLICATIONS 743,893 l/l956 Great Britain 114 62 17 Clams 10 Drawmg F'gures mafia-$21 I I l l T *W Q 45 j 37 445 PATENTEB FEB I 2 I974 sum 1 or 3 PATENTEU FEB 1 21974 SNEEI 3 or 3 LIFT STRUCTURE BACKGROUND This application is a Continuation-in-Part of my copending U. S. Pat. application Ser. No. 4,796, filed Jan. 22, 1970, and now U.S. Pat. No. 3,653,609.

In aircraft, lift is produced by a difference in pressure below a wing and above a wing with the enhanced pressure below the wing providing an upward force thereon for supporting the aircraft in flight. The difference in pressure above and below the wing is generally formed by a combination of camber in the wing and an angle of attack wherein the chord of the wing is pitched upwardly relative to the direction of flight. This latter is normally considered as a positive angle of attack. In conventional aircraft there is a substantial amount of tip losses due to air moving laterally from the center beneath the wing, thereby reducing efficiency. The trend has therefore been to long wings giving the aircraft a high aspect ratio with enhanced drag.

It is therefore desirable to produce an aircraft having minimized drag without sacrificing, and even in some cases improving, lift.

Therefore in practice of this invention according to a presently preferred embodiment there is provided a boat having parallel lifting bodies along each side and rigidly secured to the hull. Each lifting body has a downwardly facing, concave face extending substantially the entire length of the boat with side edges extending downwardly a substantial distance for inhibiting significant water flow laterally from the lifting bodies.

DRAWINGS These and other features and advantages of the present invention will be appreciated as the same becomes better understood by reference to the following detailed description of a presently preferred embodiment when considered in connection with the accompanying drawings wherein:

FIG. 1 illustrates in perspective an airplane constructed according to principles of this invention;

FIG. 2 illustrates an embodiment of this invention in the form of a lighter-than-air craft;

FIG. 3 illustrates a lifting body constructed according to principles of this invention adapted to be employed as a propeller;

FIG. 4 illustrates the propeller of FIG. 3 in perspective;

FIG. 5 is a side view of a boat constructed according to principles of this invention;

FIG. 6 is a bottom view of the boat of FIG. 5;

FIG. 7 is a transverse cross-section through the boat of FIG. 5;

FIG. 8 illustrates in perspective another boat constructed according to principles of this invention;

FIG. 9 is a fragmentary view of a lifting body for a boat constructed according to principles of this invention; and

FIG. 10 illustrates in perspective a propeller constructed according to principles of this invention.

DESCRIPTION FIG. 1 illustrates in perspective an airplane constructed according to principles of this invention. As illustrated in this presently preferred embodiment the aircraft has a conventional fuselage 10 having a motor 11 mounted on the front end for driving a conventional propeller 12. These and other conventional aspects of the inventionn are illustrated somewhat schematically in the drawings since their exact form is not critical to practice of this invention. Connected to the fuselage 10 by a plurality of transverse struts 13 is a lifting body or wing 14. Although illustrated schematically as boxshaped pieces, it will be apparent to one skilled in the art that the struts 13 and other structures encountering air flow are best streamlined on the fore and aft edges for minimizing air resistance.

Mounted on the aft end of the fuselage is a conventional empennage group including a horizontal stabilizer 16 having a movable elevator 17 for control of the angle of attack of the vehicle. A vertical rudder 18 provides for directional control. The control surfaces are preferably large and move through small angles to effect control for minimized drag.

The wing 14 in a preferred embodiment comprises a segment ofa right circular cylinder having a length substantially greater than width. The cylinder is open on its bottom side parallel to the cylinder axis so that air can enter the influence of the wing not only at its leading end but also throughout its length. It is preferred that the length of the wing along the direction of flight be greater than about three times the width of the wing in a direction transverse to the direction of flight. If the ratio of the length to width of the wing is less than about three to one, there is an increased loss of air from beneath the wing and the fulllift producing capability of the wing is not obtained.

It is of importance that the wing be less than a full cylinderand have side edges 19 extending substantially parallel to the cylinder axis substantially .the entire length of the wing for minimizing air losses. Although it is preferred that the wing be in the form of an open semi-cylinder having an arc length of about .180", it is possible to extend the side edges .19 further around the cylinder to as much as about 45 below the center line without substantially degrading the lift producing capabilities of the wing. If the side edges 19 are brought further down than about 45 an effect similar to a closed cylinder is obtained and insufficient air can enter the region within the nearly enclosed cylinder, and the lifting capability of the wing is degraded.

It is of importance that the wing is not less than about so that minimal loss of air at the sides is avoided. Although the wing is shown as a portion of a right circular cylinder in the illustrative embodiment and this is by far preferred because of the load carrying capabilities of such a uniformly curved structure, it is also possible to construct the wing in the form of a segment of an ellipse or of a polygonal cylinder or the like where instead of a smooth profile the wing is faceted. The making of some of the structural parts required for the wing is simplified in such a structure. When such a structure is employed the preferred arrangement of a wing extending over an arc of 180 may not be considered to be appropriate nomenclature and substantially the same effect is obtained by noting that the side edges 19 of the wing are lower than the center by a distance of approximately the same as one-half the distance between the opposite side edges, i.e., the wing is one-half as high as it is wide.

It will be apparent that since the preferred wing is in the form of a cylinder that there is no camber along the length of the wing. The wing itself must have some thickness in order to provide sufficient structural members internally to support the loads imposed on the wing during flight and therefore streamlining may be provided at the fore and aft edges of the wing in order to minimize drag. In the absence of lift obtained by camber the thickness of the wing need only be sufficient to provide the required structural stiffening and strength. If desired in order to minimize drag the leading edge of the wing can also be swept back somewhat from the center to the side edges.

In order to provide roll stability in the airplane, the center of gravity of the vehicle is preferably lower than the top of the wing a distance approximately the same as one-half the width of the wing. If the fuselage is located so that the center of gravity of the overall vehicle is much higher than this, roll stability must be provided by additional empennage surfaces which tend to increase drag. If the center of gravity is very much below this position the vehicle, is anything, is too stable in roll, and the ability to control the flight path of the vehicle may be impaired. Further, when the center of gravity of the vehicle is located a substantial distance below the center of lift the overall vehicle acts somewhat in the manner of a pendulum and it is found that the best dynamic stability is achieved when the center of gravity of the overall vehicle is below the top of the wing by a distance equal to about one-half the width of the wing. In a preferred embodiment, this places the center of gravity of the vehicle in substantially the same plane as the opposite side edges of the wing. It is also preferred that the vehicle center of gravity be approxi mately centered fore and aft relative to the wing. This or a position slightly aft of center provides the proper trim for the aircraft.

Lift is obtained by the wing 14 with a very low angle of attack since the wing has a great length in the direction of the line of flight. Adequate lift to support normal flight loads is obtained with a positive angle of attack of substantially less than about 7 with the wing in the form of a segment of the cylinder having a length to width ratio of about three and having the side edges of the wing extending down to about 15 below a semicylindrical form, that is, the total are of the wing is about 210.

With such an arrangement the drag introduced by the wing is relatively low since the aspect ratio is low and because of the low angle of attack of the vehicle. It is also believed that the drag is minimized due to a minimum of upper wing turbulence since the wing has no appreciable camber. Drag is also minimized since the thickness of the wing is less than that required for conventional wings since there is substantially uniform aerodynamic loading over a large portion of the wing surface and there is no long cantilevered structure that must be supported. The broad side aspect of the wing virtually completely prevents side slipping of the aircraft as may occur in conventional aircraft. Further, there are no problems of torsional rigidity about an axis along the length of the wing as are encountered in conventional wings. These beneficial effects are, to some extent counterbalanced however, due to drag by the struts 13 which must be stiff to carry the lifting load between the fuselage and the wing. In the illustrated embodiment the struts 13 are arranged in the plane of the side edges of the wing; however, this is by no means essential and drag can be somewhat reduced by joining the struts to the wing at a point above the wing edges so that they are in the form of upwardly facing broad Vs. Somewhat lighter struts can be used since the bending stresses are slightly lower.

Wind tunnel tests were conducted in the 32 inch by 45 inch three dimensional test section of the Merrill Wind Tunnel at the Guggenheim Aeronautical Laboratory, California Institute of Technology, on a lifting body constructed according to principles of this invention. The model had a length of 24 inches, a depth or height of 5.88 inches, and a width of 7.75 inches. The upper portion of the lifting body was in the form of a right circular semi-cylinder having a radius of 3.88 inches and the side edges extended straight downwardly for an additional 2 inches to give the total depth of 5.88 inches. The model was completely open at both the forward and rear ends.

A lift curve having a slope of coefficient of lift over angle of attack of 0.02 per degree was found. The maximum lift to drag ratio of about 4.2 occurred at a coefficient of lift of 0.14 and an angle of attack of about 7. Of particular interest was the complete absence of stalling of the lifting body up to the limit of the test apparatus at an angle of attack of 19. It is believed that this unusually high delay in stall is due to cross flow over the convex portion of the lifting body, which could cause fluid to feed into areas adjacent the lifting body which would normally have flow separation at a much lower angle of attack.

If desired, the same principles of the lift structure can be employed in a vehicle such as illustrated in FIG. 2 which is in the form of an open sided semi-cylinder having a length several times its width. As illustrated in this embodiment a central portion 21 is provided in the form of a large envelope which is filled with helium or the like for providing buoyant lift. Along each side edge of the buoyant central portion 21 is a cylindrical fuselage 22 for carrying cargo and which encompasses the principal structural weight of the vehicle. Small jet engines 23 on the aft ends of the fuselage sections 22 provide power for driving the vehicle through the air. Tension cables 24 between the two fuselage sections 22 are preferably employed for minimizing the structural members required in the central gas containing portion 21 of the vehicle. Movable elevators 26 and a movable rudder 27 provide for attitude and directional control of the vehicle. Roll stability is provided since the overall center of gravity of the vehicle is well below the center of lift.

In employing a vehicle such as illustrated in FIG. 2, the quantity of helium contained in the central region 21 may be sufficient that the overall vehicle is lighter than air; however, in a fully loaded vehicle, a portion of the weight may be supported by the buoyancy of the helium and the balance is supported by the lift provided by forward velocity of the vehicle. Because of the large frontal area of the gas containing volume 21 high air speeds are not feasible with the embodiment illustrated in FIG. 2. High speeds are not, however, necessary for obtaining adequate lift since a portion of the lift is provided by the buoyancy of the helium and high lift is obtained at relatively low speeds and low angle of attack because of the geometry of the semi-cylindrical lifting body.

The same high lift principles can be employed in making a propeller or similar driving member such as illustrated schematically in FIGS. 3 and 4. FIG. 3 is a rear view of such a propeller having a driving member 31 mounted on a shaft 32 and FIG. 4 is a perspective view of the driving member 31 separate from any hub.

The propeller can be considered as one half of a torus cut in a plane normal to its axis and also in a plane parallel to the axis on one side. The ends at this latter out are then displaced so that the semi-torus is distorted into a helical path. Such description is intended as a clarification of the geometry of the driving member and is in no way intended to specify a preferred manner of manufacturing the member.

It will be seen from these views that the driving member 31 is a lifting body incorporating principles of the lifting body 14 of the airplane hereinabove described. As before, the length of the body 31 as it rotates in a direction as indicated by the arrow 33 is several times as great as the width of the body in a direction transverse to the direction of travel. Also, the side edges 34 at any transverse cross-section are below the center therebetwcen by a substantial distance which in a preferred embodiment is approximately one-half the distance between the opposite side edges 34. In this manner the volume of fluid affected by the propeller is maximized.

The illustrated embodiment in FIGS. 3 and 4 is particularly useful in water as a propeller for a boat. In the illustrated embodiment the lifting body 31 extends a full 360 about a shaft and it will be apparent that if desired such a body can be provided with a greater pitch and extend less than 180 around the shaft so that a plurality of such bodies, such as for example three, each extending about 120 can be employed. In such an arrangement the angle of attack of each segment may be greater than the very few degrees angle of attack of either the full turn illustrated in FIG. 4 or an aircraft as illustrated in FIG. 1.

P16. 5 illustrates in side view a boat constructed according to principles of this invention. In FIG. 5 the at rest waterline 36 of the boat is shown to illustrate the approximate depth of the boat when supported substantially entirely by its own buoyancy; FIG. 6 shows a bottom view of the boat. FIG. 7 is a transverse crosssection of the boat, including the approximate waterline 37 of the boat when it is underway and the lifting bodies provided in practice of this invention are lifted in response to action of the water.

The boat illustrated in FIGS. 5 through '7 has a squared-off or blunt bow 38 and a blunt stern 39 as best seen in the bottom view of FIG. 6. In the illustrated embodiment a conventional outboard motor 41 is connected to the transom (illustrated in FIG. 5 only) for propulsion. It will be apparent that if desired one can employ an inboard motor or an inboard-outboard arrangement as may be desired in order to obtain propulsion. It might also be noted at this point that propulsion can be obtained by a sail as illustrated in the embodiment of H6. 8. It should also be noted that whereas the embodiment of FIGS. 5 through 7 is for a relatively small open boat, similar arrangements can be employed for larger vessels if desired. A mixture of conventional and unconventional terminology may be employed for describing the boat of FIGS. 5 to 7 because of its unconventional nature.

As best seen in FIG. 7, the top of the boat is open and the sides 42 are substantially vertical. If desired, the sides may be sloped outwardly to some extent to provide a slightly wider boat, without significantly increasing the width of the boat at the waterline. A pair of hollow seats 43 extend between the sides 42 to provide transverse rigidity as well as a place for passengers to sit. Being hollow, the seats provide buoyancy in case the boat is swamped. The bottom 44 of the hull is flat over its principal extent, and near the bow 38 it curves upwardly so as to have less water resistance when in motion at low speeds. At higher speeds, the bottom 44 lifts out of the water as hereinafter set forth in greater detail.

Along each lower side edge of the boat is a runner 46 which is preferably in the form of a hollow body for providing buoyancy in case the boat is swamped. Each of the runners 46 has substantially vertical side walls 47; however, some variation from this shape is acceptable if desired, for example, for providing a fairing between the inner side wall 47 and the boat bottom 44. The lower portion of each of the runners 46 is in the form of a downwardly facing concave face 48, which is preferably in the form of a portion of a right circular cylinder along a principal portion of the length of the boat. Nearer the forward end of the boat the runners gradually curve upwardly until the lowermost edges 49 of the runner blend into the upwardly curving boat bottom near the bow. The concave face 48 also curves upwardly and near the bow may diminish in depth of concavity at points above the normal at rest water line.

As mentioned hereinabove, when the boat is at rest it displaces a volume of water that yields a normal at rest waterline 36 higher than the boat bottom 44 so that the bottom is wetted over the principal length of the boat. When the boat is underway the downwardly facing concave faces 48 of the runners provide lift by reaction against the water through which the boat is moving. Because of this lift, the boat rises in the water until a normal waterline 37, as illustrated in FIG. 7, is reached, at which time the bottom 44 is not wetted and only the runners 46 are within the water. The water level is such that the downwardly facing concave faces 48 are wetted over most of their length and only minor quantities of air which may be entrained in the water actually passes along the length of the runners on the concave face. Thus, the lift obtained by the downwardly facing lifting runners is due to interaction of the lifting bodies along each side edge with the water rather than interaction with air. Because of the much greater density and substantial incompressibility of the water, much higher lift can be obtained by interaction therewith than with any air interaction at the speeds obtainable by the boat.

A boat, as illustrated in FIGS. 5 through 7, apparently moves at a higher speed with a given power than do comparable boats with flat or deep V-hulls. Such comparison is made with difficulty since definition of an appropriate comparable boat is not readily appar ent. The reason that the boat provided in practice of this invention is faster at a given power level than comparable boats is believed to be because of the lifting effect of the two lifting runners 46 along each edge which substantially reduces the wetted area of the boat when it is underway. A similar effect has been noted in hydrofoils; however, direct comparison to operating characteristics of a hydrofoil wherein lift is obtained by structures analogous to airfoils has not been possible to date.

Evidence of the relatively small amount of water displaced by the lifting bodies along side edge is given by the relatively small wake produced by this improved boat when underway. This is believed due to the side edges 49 of the runners, which are well below the center of the concave face 48. This effectively prevents water from being propelled laterally from beneath the runners, and lift is obtained throughout substantially the full length of the runners while the boat is underway. Thus, it is apparent that the lifting body provided by the downwardly facing concave face 48 with side edges 49 substantially below the midpoint thereof provides an effect in the water analogous to the lifting force provided by the lifting body 14 hereinabove described and illustrated in FIG. 1.

FIG. 8 illustrates in perspective a sailboat constructed according to principles of this invention. As illustrated in this embodiment, two separated hull portions 51 extend along the length of the boat at each side edge. The two hull portions 51 are interconnected by structural members 52 extending laterally therebetween. These structural members are illustrated as flat planks; however, it will be apparent that truss-like interconnection can be employed for greater rigidity if desired. A mast 53 is connected to one of the cross members 52 for supporting conventional sails 54 illus trated only schematically.

The bottom of each of the bulls 51 is formed as a lifting body having a downwardly facing concave face 56 having side edges 57 substantially below the center of the concave face 56. Thus, as each of the bulls 51 moves through the water, a substantial lifting force is provided on the concave face 56 so that the volume of water displaced by the boat while underway is substantially less than the displacement while the boat is at rest. Even when underway, the downwardly facing concave faces 56 are wetted throughout the principal portion of their length and only incidental air that may be trapped near the bow passes along the length of the lifting bodies. It will be apparent that the cross members 52 do not produce any substantial lift as they move through the air, and that virtually the entire lift that is produced by the boat while underway comes from interaction with the water by the downwardly facing concave faces 56 on the bottom of the hull portions 51.

FIG. 9 illustrates in a fragmentary view a portion of one runner 61 constructed according to principles of this invention, and particularly suitable for quite high speed boats. Such a runner 61 as illustrated in FIG. 9 can be substituted for the runners 46 in a boat such as that illustrated in FIGS. through 7, where the boat is intended for high speed operation. The fragmentary view of FIG. 9 is a view looking from the bow towards the runner 61 to show the principal downwardly facing concave face 62, which near the bow curves upwardly in the same manner as the face 48 of the runner 46 illustrated in FIGS. 5 through 7. Each of the side edges 63 of the principal concave face 62 is also provided with a smaller downwardly facing concave face 64, which also extends along the principal extent of the runner 61. Each of the minor concave faces 64 has an inner side edge 63 forming the side edge of the principal downwardly facing face 62 and an outer side edge 66 at the side edge of the runner.

When a boat fitted with a runner such as that illustrated in FIG. is underway at moderate speed, the lift produced by the interaction of the concave face 62 with the water lifts the boat so that the waterline 67 is below the at rest water line and above the uppermost portion of the principal concave face 62. it will be apparent that the waterline 67 illustrated in phantom in FIG. 9 is merely exemplary and its actual position may vary with the actual speed of the boat through the water; lower speeds resulting in greater displacement of water by the runner and higher speeds resulting in lesser displacement due to the higher lift produced by interaction of the downwardly facing concave faces on the water.

As the speed increases, lift also increases, and eventually a point is reached wherein the principal concave face 62 is no longer wetted throughout its full extent since the boat has lifted to the point that the waterline 68 is below the uppermost reach of the principal concave face 62. The minor concave faces 64 continue to provide lift to maintain the higher speed waterline 68 at a level wherein the principal portion of the larger concave face is not wetted but the minor concave faces 64 continue to be wetted. In this way the runner 61 behaves in a manner analogous to the entire boat illustrated in FIGS. 5 through 7, with each lifting body formed by the minor concave faces 64 with their side edges 63 and 66 behaving as an individual runner. The speed at which sufficient lift is obtained from the water for getting the described effect may be rather high and depends on the size and weight of the boat and the size of the lifting bodies along its edges.

In a variation of the structure of FIG. 9 for particularly high speed boats one of the two minor concave faces can be narrower than the other and also deeper in the water at rest. Thus at low speeds all three concave faces are wetted and providing lift. At intermediate speeds the largest, central concave face lifts clear of the water and only the medium and smallest faces are wetted. At highest speeds further lifting occurs so that only the smallest face remains in the water for minimum drag. Preferably the smallest, deepest face is at the outboard edge of the runner along each side of the boat for providing best stability.

FIG. 10 illustrates in perspective a propeller constructed according to principles of this invention. In many propellers, both for water and air usage, substantial losses are encountered due to fluid flowing laterally from the blades, that is, radially with respect to the pro peller. Ducted propellers have been provided wherein the tips of the blades are surrounded by a fixed housing for minimizing the tip losses at the outer ends of the blades. Close clearances are required for good efficiency.

In the propeller illustrated in FIG. 10, tip losses from the blades are minimized both in the direction of flow of fluid radially outwardly from the blades, and in the direction of radially inwardly directed flow. Thus, as illustrated in FIG. 10, the propeller comprises a hub 71 having a central hole 72 for connection to a propeller shaft (not shown). It should be recognized that the hub 71 is shown only generally and no means are illustrated for keying the hub to the shaft to assure rotation there with. Suitable means for connecting the propeller to a shaft in any conventional manner may be provided by one skilled in the art. Extending radially from the hub 71 are four spokes 73 of any desired cross section. The spokes 73 may be essentially flat or are preferably streamlined for minimized interference with fluid flow. If desired the spokes 73 may be skewed somewhat in a conventional manner for providing a minor amount of lift or thrust.

At the outer ends of the spokes 73 there is an inner ring 74 which is as thin as structurally feasible in a radial direction but extends a substantial distance in a direction parallel to an axis running through the central hole 72. Outwardly from the inner rings 74 is an outer ring 76 which is also as thin as feasible in a radial direction, and which also has an axial length in the same order of magnitude as the length of the inner ring 74. Between the inner and

outer rings

74 and 76, respectively, are a plurality of generally radially extending blades 77, two of which are illustrated in FIG. 10. Typically, eight such blades 77 are provided around the circumference of the propeller. Each blade 77 has a leading edge 78 so that as the propeller rotates in the direc tion indicated by the arrow 79, the leading edge 78 is the first to encounter the fluid in which the propeller is operating. The leading edge 7% is preferably in the same plane as the edges of the two

rings

74 and 76. If, as in some embodiments, the outer ring 76 is slightly longer than the inner ring 74, the leading edge 78 of each of the blades extends between the ends of the two rings and is not necessarily normal to an axis through the mounting hole 72.

Similarly, each of the blades 77 has a trailing edge 81 extending between the inner ring 74 and the outer ring 76. The trailing edge 81 is preferably in the plane formed by the aft ends of the inner and outer rings, or if the outer ring 7b is longer, the trailing edge 81 may extend between the ends of the two rings. If desired, the inner and

outer rings

74 and 76, respectively, can extend further aft than the trailing edge fill so that it is not in a line between the ends of one or both of the rings. Such an embodiment may further minimize tip losses and increase propeller efficiency.

Between the leading and trailing

edges

78 and 81, respectively, of each blade, the blade may follow a generally helical path so that it is in effect without camber. if desired, however, a degree of camber can be pro vided so that the angle of attack at the leading edge 78 is less than the angle of attack of the blade on the fluid at its trailing edge 8]. This introduces a degree of twist in the blade 71 and results in somewhat higher efficiency than obtained with a completely helical blade. In addition if desired, the pitch of the blade from the region adjacent the inner ring 74 to the outer ring 76 can be varied in a conventional manner to obtain optimum efficiency. Thus, the propeller may have constant or variable pitch in both circumferential and radial directions.

As the propeller operates by rotating in the direction of the arrow 79, each of the blades 77 and the adjacent portions ofthe inner and

outer rings

74 and 76, respectively, operate as a separate lifting body operating according to principles of this invention. Thus, in effect, each blade cooperates with the rings to provide a concave face (rearwardly in FIG. if and hence hidden) bounded by side edges formed by the

rings

74 and 76. These side edges operate in the manner of the side edges of the airfoil hereinabove described and illustrated in FIG. 1, and the propeller illustrated in H6. 4, for minimizing lateral flow of fluid and hence tip losses that rob efficiency.

Although only a few embodiments of a lifting body incorporating principles of this invention have been described and illustrated herein, it will be apparent that many modifications and variations can be made by one skilled in the art. Thus, for example, the lifting bodies on a boat may not extend the full length of the boat, but be truncated near the bow or stem or both for further reducing water drag. in an aircraft embodiment the wing provides sufficient lift at low speeds to operate successfully as a glider. This is advantageous in case of loss of power since the aircraft has an excellent glide path and roll stability. In another variation a lifting body constructed according to principles of this invention may be inverted and attached to a high speed car for holding down against a track. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. A boat comprising:

first and second parallel lifting bodies, one along each side edge of the boat;

means for rigidly interconnecting the lifting bodies and; wherein each lifting body comprises a downwardly facing concave face extending substantially the entire length of the boat; and

side edges on each concave face extending downwardly a sufficient distance beyond the middle of the concave face for inhibiting substantial flow of water laterally therefrom.

2. A boat as defined in claim 1 wherein the length of each of the lifting bodies is several times the width thereof.

3. A boat as defined in claim 1 wherein each lifting body further comprises:

second and third downwardly facing concave faces one along each side edge of the first concave face, the second and third concave faces being smaller than the first concave face and spaced downwardly therefrom.

4. A boat as defined in claim 1 wherein the means for securing the lifting bodies comprises a substantially continuous hull having a normal at-rest water line above the bottom portion of the hull; and wherein the water line when the boat is underway is approximately adjacent the upper portion of the concave faces on the lifting bodies.

5. A boat as defined in claim 1 wherein the means for securing the lifting bodies comprises a substantially open array of structural members permitting free air flow therethrough.

6. A planing boat comprising:

first and second lifting bodies along opposite side edges of the boat, each comprising an elongated member having a length along the direction of travel substantially greater than width transverse to the direction of travel, and having a downwardly facing concave face extending along the length, with parallel side edges sufficiently lower than the center of the lifting body for inhibiting substantial lateral flow of water therefrom; and

means for fixedly securing the first and second lifting bodies to extend generally parallel to each other along their length, said interconnecting means being above the normal water line ofthe boat when traveling.

7. A planing boat as defined in claim 6 wherein each lifting body has a principal portion of the length of the concave face in the form of a portion of a right circular cylinder.

8. A planing boat as defined in claim 6 wherein the means for securing comprises a watertight hull normally wetted when the boat is at rest, and the lifting bodies provide sufficient lift for elevating the hull free of the water surface as speed is attained.

9. A planing boat as defined in claim 6 wherein the concave face of each lifting body is approximately onehalf as high as it is wide' 10. A boat comprising:

a hull;

a first lifting body fixedly secured along one lower side edge of the hull;

a second lifting body similar to the first lifting body fixedly secured along the other lower side edge of the boat and parallel to the first lifting body, wherein each lifting body is in the form of an elongated member having a length along the direction of travel of the boat much greater than width transverse to the direction of travel and being substantially free of camber throughout most of its length, each lifting body being concave on the lower face when viewed in the direction of travel and having parallel opposite side edges of the concave face lower than the center of the concave face a distance of approximately the same as one-half the distance between the opposite side edges of the concave face, the side edges of the concave face extending substantially the entire length of the lift ing body; and

means for spacing the two lifting bodies a sufficient distance below the boat hull that lifting force applied to the lifting bodies by water as the boat moves is sufficient to assure clearance of the portion of the hull between the lifting bodies and the water.

11. A boat as defined in claim 10 wherein each lifting body comprises:

a relatively larger central downwardly facing concave face;

a relatively smaller downwardly facing concave face along each side edge of the central concave face, and wherein the lifting force applied on the concave faces is sufficient for lifting a portion of the central concave face above the waterline when the boat is under way 12. A boat as defined in claim 10 wherein each of said lifting bodies extends a principal portion of the length of the boat.

13. A boat as defined in claim 10 wherein each of the lifting bodies extends substantially the entire length of the boat in a direction parallel to the center line thereof.

14. A boat as defined in claim 10 wherein each lifting body is in the form of a segment of a right circular cylinder extending more than about around an are.

15. A boat as defined in claim 14 wherein the length of the lifting body is greater than about three times the width of the lifting body.

16. A boat as defined in claim 10 wherein the lifting force applied by the lifting bodies is less than enough to raise the boat above a level where the water line is below the center of the concave face.

17. A boat as defined in claim 16 wherein the means for securing the lifting bodies and hull each comprise substantially vertically extending sidewall portions extending upwardly from the side edges of the concave face to the boat hull.

Claims

1. A boat comprising: first and second parallel lifting bodies, one along each side edge of the boat; means for rigidly interconnecting the lifting bodies and; wherein each lifting body comprises a downwardly facing concave face extending substantially the entire length of the boat; and side edges on each concave face extending downwardly a sufficient distance beyond the middle of the concave face for inhibiting substantial flow of water laterally therefrom.

3. A boat as defined in claim 1 wherein each lifting body further comprises: second and third downwardly facing concave faces one along each side edge of the first concave face, the second and third concave faces being smaller than the first concave face and spaced downwardly therefrom.

6. A planing boat comprising: first and second lifting bodies along opposite side edges of the boat, each comprising an elongated member having a length along the direction of travel substantially greater than width transverse to the direction of travel, and having a downwardly facing concave face extending along the length, with parallel side edges sufficiently lower than the center of the lifting body for inhibiting substantial lateral flow of water therefrom; and means for fixedly securing the first and second lifting bodies to extend generally parallel to each other along their length, said interconnecting means being above the normal water line of the boat when traveling.

9. A planing boat as defined in claim 6 wherein the concave face of each lifting body is approximately one-half as high as it is wide.

10. A boat comprising: a hull; a first lifting body fixedly secured along one lower side edge of the hull; a second lifting body similar to the first lifting body fixedly secured along the other lower side edge of the boat and parallel to the first lifting body, wherein each lifting body is in the form of an elongated member having a length along the direction of travel of the boat much greater than width transverse to the direction of travel and being substantially free of camber throughout most of its length, each lifting body being concave on the lower face when viewed in the direction of travel and having parallel opposite side edges of the concave face lower than the center of the concave face a distance of approximately the same as one-half the distance between the opposite side edges of the concave face, the side edges of the concave face extending substantially the entire length of the lifting body; and means for spacing the two lifting bodies a sufficient distance below the boat hull that lifting force applied to the lifting bodies by water as the boat moves is sufficient to assure clearance of the portion of the hull between the lifting bodies and the water.

11. A boat as defined in claim 10 wherein each lifting body comprises: a relatively larger central downwardly facing concave face; a relatively smaller downwardly facing concave face along each side edge of the central concave face; and wherein the lifting force applied on the concave faces is sufficient for lifting a portion of the central concave face above the waterline when the boat is under way.

12. A boat as defined in claim 10 wherein each of said lifting bodies extends a principal portion of the length of the boat.

14. A boat as defined in claim 10 wherein each lifting body is in the form of a segment of a right circular cylinder extending more than about 180* around an arc.

16. A boat as defined in claim 10 wherein the lifting force applied by the lifting bodies is less than enough to raise the boat above a level where the water line is below the center of the concave face. 17. A boat as defined in claim 16 wherein the means for securing the lifting bodies and hull each comprise substantially vertically extending sidewall portions extending upwardly from the side edges of the concave face to the boat hull.