US 3697023 A
A kite is formed from highly flexible sheet of material and has a pair of symmetrical wing sections which extend transversely from a central longitudinal keel. A bridle is connected to the kite at the lateral tips of each wing section and to the keel. The lines of the bridle are arranged so that, in flight, the wing sections will billow out in an arcuate pattern in which the outermost ends of each of the wing sections are disposed in a generally vertical attitude. Outwardly flared tabs are provided at the leading edge of the outermost ends of the wings to maintain the billowed configuration of the kite and to preclude inward buckling of the outer generally vertical regions of the wings.
Claims available in
Description (OCR text may contain errors)
United States Patent Jackson KITE  lnventor: Richard R. Jackson, 8 Trinity Road,
Marblehead, Mass. 01945 22 Filed: May 12,1971
211 Appl.No.: 142,492
 References Cited UNITED STATES PATENTS 3/1951 Rogallo et a1. ..244/153 R 6/1956 Rogallo et a1 ..244/153 R 3/1971 Jackson "244/153 R [151 3,697,023 51 Oct. 10, 1972 Primary Examiner-Milton Buchler Assistant Examiner-Paul E. Sauberer Attorney-Wolf, Greenfield, l-lieken & Sacks ABSTRACT A kite is formed from highly flexible sheet of material and has a pair of symmetrical wing sections which extend transversely from a central longitudinal keel. A bridle is connected to the kite at the lateral tips of each wing section and to the keel. The lines of the bridle are arranged so that, in flight, the wing sections will billow out in an arcuate pattern in which the outermost ends of each of the wing sections are disposed in a generally vertical attitude. Outwardly flared tabs are provided at the leading edge of the outermost ends of the wings to maintain the billowed configuration of the kite and to preclude inward buckling of the outer generally vertical regions of the wings.
12 Claims, 8 Drawing Figures PATENTEDHBI 10 4912 FIG. I
INVENTOR RICHARD R. JACKSON I f ATTORNEYS FIG. 8
BACKGROUND OF THE INVENTION This invention relates to kites and kitelike devices of the general type shown in U.S. Pat. No. 2,546,708 to Rogallo which shows a kite having a pair of symmetrical wings sections which are formed from a highly flexible sheet of material. This invention relates to improvements in the construction of such kites, which improvements are adapted to reduce materially any tendency for the wings to buckle, particularly in the outermost regions of the wing tips.
The kite includes a pair of symmetrical highly flexible wings which extend transversely from a longitudinal central line keel. A bridle, comprising a number of lines, is attached to the kite, there being one line attached to the lateral tip of each wing and at least one line attached to the central keel. Each of the bridle lines converge beneath the kite, when in flight, and are attached at a common point to the kite string. The wingspan and the dimensions of the lines making up the bridle are arranged so that when in flight, each of the wings will billow laterally from the keel in an are which is generally horizontal at the root of each wing, adjacent the keel, and which gradually and smoothly curves in its billowed configuration so that the lateral, outer ends of each wing is disposed in a generally vertical attitude. During flight, the center line keel of the kite is disposed at a slight angle to the horizontal to establish angle of attack sufficient to maintain flight. The lateral outer ends of the wings, however, are disposed in a generally vertical attitude and, therefore, ordinarily would make no angle of attack with the relative wind irrespective of the general attitude of the center keel and other portions of the kite. Thus, a portion of the leading edge at the outer region of the wings ordinarily makes a minimal or no angle attack with the relative wind and presents the leading edge directly to the relative wind. The wind may easily impinge on the outer surface of the wing which would cause that surface to buckle thus disrupting smooth flight and causin'g erratic flight behavior. In accordance with the invention, the foregoing difficulties are avoided by providing tabs formed integrally with and at the leading edge of each wing in the outer extremities thereof which, during flight are disposed normally in generally vertical attitude. The tabs are bent outwardly at an angle to the wings so that in flight it is insured that a positive angle of attack between the tabs and the relative wind will be maintained. The tabs are stiffened to insure that they will be maintained at the positive angle of attack at all times.
Additional advantage which is achieved by employing the tabs is that they enable the rearward sweep of the leading edge of the wings to be reduced. I have found that kites of the general type described tend to fly higher and develop less drag as the degree of wing sweep is reduced. Reduction of the degree of sweep, increases the tendency of the flexible wing to buckle. Provision of the outwardly bent tabs at the outer ends of the wings counteract the buckling tendency and enables the sweep of the leading edges of the wings to be reduced. Although the tabs develop a slightly increased drag, this is more than offset by the increase in lift achieved by reduced wing sweep. The resulting lift to drag ratio is effectively increased.
2 It is among the primary objects of the invention to provide an improved kite structure.
Another object of the invention is to provide an improved kite of thegeneral type described having means for eliminating any tendency for vertically disposed leading edges of the kite to buckle during flight.
A further object of the invention is to provide an improved kite construction which is adapted to fly in extremely light wind conditions yet which is very stable in heavy winds.
DESCRIPTION OF THE DRAWINGS These and other objects and advantages of the invention will be understood more fully from the following detailed description thereof, with reference to the accompanying drawings wherein:
FIG. 1 is a substantially scale illustration of a kite constructed in accordance with the invention, as viewed from the underside of the kite with the wings and heel portion spread out to show the preferred relative dimensions thereof;
FIG. 2 is a side elevation of the kite when in flight;
FIG. 3 is an elevation of the kite, when in flight, as seen along the line 33 of FIG. 2;
FIG. 4 is a section taken through the leading edge of the kite illustrating the tabs as seen along the line 4--4 of FIG. 1;
FIG. 5 is a sectional view of the tabs as seen along the lines 5-5 of FIG. 1;
FIG. 6 is an enlarged illustration of the manner in which the bridle lines may be attached to the like;
FIG. 7 is an illustration of the relative length of the lines in the bridle as employed in the preferred embodiment shown; and
FIG. 8 is a section through the keel.
DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1, the kite includes a pair of symmetrical wings 10 which extend laterally of a longitudinalcenter keel 12. The wings preferably are formed from a flexible sheet material which may be selected from a variety of commercially available plastic films or resins such as Mylar. The sheet material should be as thin as is practically possible to reduce the weight of the kite while retaining the desired degree of strength. I have found that Mylar sheets of approximately 0.00l to 0.0005 inches thick to be satisfactory. The kite also preferably includes a central heel 14 which is secured, at the underside of the kite, to the keel 12 as shown. The heel 14 is formed from the same sheet material as the wings 10.
In the illustrative embodiment shown, the keel 12 is formed from a pair of elongate wood or plastic rods 16 shown in enlarged cross-section in FIG. 8. The wings 10 may be formed from a single continuous sheet of material, if desired, which is folded along its center line to define the fold 18. This fold l8 and the upper edge 20 of the heel 14 may be sandwiched together between the rods 16 and the assembly may be stapled together firmly at a number of locations along the length of the keel 12. This secures the various elements of the kite firmly together. Alternatively, the wings 10 may be formed individually and their inner edges may be sandwiched together between the rods 16 with the upper edge of the heel 14 being sandwiched between the inner edges of the wings.
Each wing includes a freely flexible leading edge 22 and similarly flexible trailing edge 24. The various bridle lines 26, 28 and 30 are connected, respectively, to wing tip tabs 32, the heel tab 34 and the keel tab 36. The tabs each are formed from a sufficiently strong material such as reenforced tape which may be bonded to the kite as shown. The keel tab 36 preferably is sandwiched between the rods 16 of the keel l2 and is stapled firmly thereto. Each of the tabs 32, 34, 36 includes an eyelet 38 for attachment of its respective bridle line.
FIG. 6 shows a representative arrangement for detachably attaching the heel line 28 of the bridle and includes a lug 40 which is crimped or otherwise secured to the end of the line 28. The line 28 and lug 40 are attached so that the line extends from a point intermediate the lug. The cross sectional dimensions of the lug are such that the lug may be urged longitudinally through the eyelet. The line 28 and lug 40 then may assume a generally T-shaped configuration as shown in FIG. 6 which precludes inadvertent separation of the line from the tab.
As shown more clearly in FIGS. 2 and 3, when in flight, the wings l assume the generally billowed, arcuate shape shown in which the innermost root region 42 is disposed in a generally horizontal attitude whereas the outer region 44 of each wing tends to assume a generally vertical attitude. In flight, the kite may assume a representative angle of attack as suggested by the relative wind 46 in FIG. 2 and during flight this angle may vary somewhat. The angle of attack with regard to the horizontally disposed portions of the leading edge of the kite and, particularly, the
. root region 42, insures that these regions of the leading edge of the kite will meet the relative wind at a positive angle of attack, however small. The more vertically disposed outer regions of the leading edges of the wings, however, tend to make no appreciable angle of attack with the relative wind. Thus, any slight rapid windshift or slight yaw in the kite would tend to expose the outer surface of an end of the wing to the wind. Obviously, this would cause that region of the wing to buckle almost instantaneously and the buckling effect would be transferred along the full span of the buckled wing. This results in most erratic flight behavior and obviously is undesirable. The kite construction of the invention insures that the outer, vertically disposed regions 44 of the wings 10 will not buckle as the result of kite yaw, wind shifts or the like. As a result, flight is extremely stable. This is achieved by providing one or more tabs 48 at the leading edge of each wing in the outer region 44 thereof which is disposed in the generally vertical attitude during flight. The tabs 48 may be of triangular configuration as shown and project forwardly of the leading edge 22 of each wing. In the embodiment shown, the tabs 48 are formed integrally and continuously with the sheet material of the wings 10 but they may be formed as separate members attached subsequently to the wing during fabrication. Means are provided for stiffening the tabs in relation to the leading edge region of the wings so that they will be maintained in their outwardly bent configuration shown best in FIG. 3. The arrangement to stiffen the tabs is shown as a slender batten 50 in association with each of the tabs. The battens 50 may be formed from a slender piece of plastic or wood as shown more clearly in FIG. 4. The battens 50 extend from the forwardmost apex of each of the tabs 48 toward the trailing edge 24 of the wing 10. Each batten is parallel to the keel 12 so as not to interfere with the spanwise flexure of the wings during flight. The leading end 52 of each batten is bent at the angle at which it is desired to support the tabs 48 in relation to the surface of the wing. When the batten 50 is fabricated from wood, the leading end may be bent by slitting one side of the batten where the bend is to be made, bending the batten at the slit portion to the desired angle and then filling the other side of the batten with a gob of cement 54 to insure that the angle will be maintained. Each of the battens 50 may be secured to the outer surface of the wings by an appropriate adhesive which is compatible with the materials from which the wings and battens are made. I have found by experimentation that in order to achieve the best flight results, the tabs 48 should be disposed at an angle to the wing of between 14 and 16".
As mentioned above, I have found that by reducing the sweep of the leading edges of the wings, the kite develops an improved lift and, therefore, it flies higher and more directly overhead. Reducing the wing sweep, however, increases the tendency of the wings to buckle. It is believed that the buckling effect caused by reducing the wing sweep is a result of a tendency of the wings to twist so that their leading edges defined an arcuate pattern of reduced radius than the arcuate pattern defined by the trailing edges of the wings. This tends to present the leading edge of the reduced-sweep wings more directly to the relative wind. By providing the tabs at the outer regions of the leading edge of the wings, the twisting tendency is counteracted. The tabs are effective to urge the outer regions of the wings laterally and outwardly to the largest arcuate radius permitted by the bridle lines. I have found that utilization of the tabs enables the sweep of the leading edges of the wings to be reduced so that the outer lateral tips of the wings are swept back a distance equal to as little as about one quarter of the length of the kite. Although the invention may be practiced by employing a single tab 48 in association with each of the wings, it is preferred to employ a pair of such tabs, spaced along the span of the wings as shown.
I have found that best results as to stability and other flight characteristics of the kite are achieved when certain approximate relative dimensions are employed in its manufacture. For example, I have found that when the span of the kite is approximately equal to its spread out length, as shown in FIG. 1, the tips of the wings may be swept back from the forward tip of the keel a distance as little approximately equal to one fourth of the kite length, with this amount of sweep being preferred. Additionally, the tabs 48 should be included only in the outer third of the end of each wing and preferably are spaced apart in an amount equal to the width'of the tab. As mentioned earlier, the most effective angles between the tab and the wings lie between 14 and 16. The heel preferably should extend downwardly from the keel a distance approximately equal to one fourth of the fully extended wing span. The wing lines 26 and heel line 28 of the bridle should be of a length approximately equal to the length of the kite with the heel bridle line 28 being slightly shorter as suggested in FIG. 7. The keel bridle line 30 is somewhat longer and preferably is approximately one third longer than the other lines in the bridle. I prefer to locate the keel tab 36 forwardly of the tail end of the keel a distance approximately equal to one fourth of the length of the keel.
Thus, l have described an improved kite construction which is extremely stable in flight and which displays practically no variation in stability throughout a wide range of wind velocities. l have found the kite to fly equally well both in extremely light wind, as low as approximately 4 to 5 miles per hour and in much higher, stiff breezes. Additionally, the kite constructed in accordance with the invention is believed to provide an improved lift to drag ratio which results in the capability of higher, more directly overhead flight.
It should be understood that the foregoing description of the invention is intended merely to be illustrative thereof and that other embodiments and modifications may be apparent to those skilled in the art without departing from its spirit.
Having thus described the invention what I desire to claim and secure by Letters Patent is:
1. An aerodynamically supportable device comprisa rigid keel extending longitudinally of said device;
a pair of wing-like members, each having a leading edge and a trailing edge, each of said wing-like members being formed from a thin sheet of flexible material, said wing-like members being secured to said keel and extending transversely and symmetrically on either side of said keel;
a bridle line connected at one end to the tip of each of said wing-like members;
atleast one bridle line connected at one end to said keel, the other end of each of said bridle lines being connected to each other at a common juncture below said wing-like members and said keel;
said bridle lines and wing-like members being dimensioned so that in flight, each of said wing-like members will billow out in an arcuate pattern in which the outer region of each of said wing-like members is disposed in a generally vertical attitude;
at least one tab secured to each of said wing-like members at the outer regions thereof, each of said tabs extending forwardly of the leading edge of their associated wing-like members and being bent outwardly at a predetermined angle, to expose the inner surface of each of said tabs to the relative wind; and
means for stiffening each of said tabs with respect to their associated wings to maintain said tabs at said predetermined angle in relation to their associated wings.
2. A device as defined in claim 1 wherein said predetermined angle lies between 14 and 16.
3. A device as defined in claim 1 further comprising:
each of said tabs being formed integrally and continuously with said sheet material forming said wing-like members; and
said means for stifi'ening said tabs comprising a batten associated with each of said tabs, each batten b in ecured to the outer urface its associated wing -like member in parall el to said keel, each of said battens extending from the forward tip of its associated tab rearwardly toward the trailing edge of said wing, the forward end of each of said battens being bent at said predetermined angle.
4. A device as defined in claim 3 wherein said predetermined angle lies between 14 and 16.
5. A device as defined in claim 1 wherein said tabs are of triangular configuration.
6. A device as defined in claim 1 wherein each of said wing-like members has two of said tabs, each of which lies within the outer third portion of the leading edge, said tabs being spaced from each other along said leading edge.
7. A device as defined in claim 1 wherein said keel comprises:
a pair of parallel elongate members extending along the length of said device, said means joining said wing-like members to said keel comprising the inner longitudinal portions of each of said winglike members being disposed between and along said rods; and
means for securing said rods and said longitudinal portions of said wings together to sandwich said portions of said wings between said rods.
8. A device as defined in claim 7 wherein said wings are formed from a single continuous sheet, said inner longitudinal portions of said wings being folded between said rods.
9. A device as defined in claim 7 further comprising:
a heel member disposed at the forward end of said device and at the underside thereof, said heel member comprising a sheet of said flexible material, the upper longitudinal edge of said heel member being sandwiched between said rods, the lower end of said heel member extending downwardly between said wing-like members.
10. A device as defined in claim 1 wherein the wing span is substantially equal to the length thereof, said wing tips being swept rearwardly from the leading end of said device an amount equal to approximately onefourth of the length thereof.
11. A device as defined in claim 10 wherein said wing tip lines of said bridle and at least one of said keel bridle lines are each approximately equal in length to the wing span of said device.
12. A device as defined in claim 1 wherein said bridle lines are connected to said device by detachable means comprising:
eyelet means secured to said device at each point of attachment of said bridle lines;
each of said bridle lines having an elongate lug secured to an end thereof, each of said lines being connected to its associated lug at a point intermediate the ends of said associated lug; and
the cross-sectional dimension of said lug being of smaller size than the size of said eyelet, and the length of each of said lugs being greater than the size of said eyelet.