US3790112A - Kites - Google Patents

Abstract

A kite uses wooden sticks having a figure-8 cross section made of two round sectioned sticks glued together side by side, producing freedom from stick breakage and uniformity of stick bending deflection, using materials available commercially in large quantities. The construction applies most advantageously to kites having strongly bent sticks and to kites of high aspect ratio and especially to kites as taught in U.S. Pat. No. 3,335,984.

Description

United States Paten Holland, Jr.

[ KITES [76] Inventor: Raymond Prunty Holland, .lr., 1702 W.'Third St., Roswell, N. Mex., 88201 [22] Filed: Nov. 11, 1971 21 Appl. No.: 197,838

[52] U.S. C1 244/153 R [51] Int. Cl. B64c 31/06 [58] Field of Search 244/153 R, 154; 161/172; 156/166, 180; 52/730 [56] References Cited UNITED STATES PATENTS 648,544 5/1900 2,238,427 4/1941 2,442,417 6/1948 3,335,984 8/1967 1,021,278 3/1912 1,346,956 7/1920 Hale....l 244/154 Feb. 5, 1974 1,892,985 1/1933 Hughes 244/153 R 2,785,870 3/1957 Green 244/153 R 3,055,622 9/1962 Harmon 244/155 R FOREIGN PATENTS 0R APPLICATIONS 561,856 10/1923 France 244/153 R 1,408,652 7/1965 France 244/155 R Primary Examiner-Duane A. Reger Assistant Examiner-Paul E. Sauberer [57] ABSTRACT A kite uses wooden sticks having a figure-8 cross section made of two round sectioned sticks glued together side by side, producing freedom from stick breakage and uniformity of stick bending deflection, using materials available commercially in large quantities. The construction applies most advantageously to kites having strongly bent sticks and to kites of high aspect ratio and especially to kites as taught in U.S. Pat. No. 3,335,984.

2 Claims, 11 Drawing Figures ll KITES The present invention relates to improvements in kites, particularly kites having strongly bent sticks and to high aspect ratio kites requiring uniformly symmetrical wing bending in order to maintain symmetrical lateral trim in flight. The improvements apply especially to the type of kite taught in U.,S. Pat. No. 3,335,984, which is a kite of high aspect ratio employing an exposed forward-extending nose stick, which, until the present invention, was subject to breakage.

The problem of obtaining good kite sticks is as old as kite flying and has become severe as kites have been produced in large quantities and have employed lifting surfaces of increased aspect ratio and as the supply of defect-free straight grained wood, obtainable only from large trees, has diminished. Especially in manufacturing high quality kites in large quantities the problem of obtaining good sticks has become critical, sometimes forcing suspension of production.

The well-known problems of breakage of kite sticks due to rough handling by children is serious in itself,

- but the stick problem faced by the kite industry goes beyond this. Wooden sticks commonly bend unevenly, warp, splinter, and split. Even the best grades of lumber are not of uniform quality. The stiffness of sticks varies from board to board, and from one end of a board to the other. Where the proper form of a kite depends on the correct relative amount of bend of two. or more bent sticks, as in the case of high performance high aspect ratio kites, the desired results have been obtained only by testing each completed stick for symmetry of bend, proper stiffness, and freedom from twist. In this process, many completed sticks are found to be unsatisfactory and must be discarded; this is an expensive and wasteful process, unsuited to mass production.

. The basic problem of the kite stick stems from the fact that the kite stick is a very slender structural member, such that any defect, such as a tiny knot in the natural wood, causes a disproportionaly large loss of strength at that section of the stick, so that it snaps when bent only slightly. Similarly, cross grain angling only slightly out of parallel from the line of the stick emerges from the surface of the stick in only a short distance, so that the stick breaks along the cross grain when bent, or the portion of the stick having such cross grain is relatively soft in bending, producing a stick having excessive deflections and uneven bending. Similarly, slight cross grain which would not be serious in a member having larger cross sectional dimensions, causes the kite stick to twist when bent, the twist in turn often causing uneven bending as one end of the stick twists over relative to the other end. Uneven bending, whatever the reason, causes correspondingly irregular flight characteristics in the kite.

Conventional kite sticks are sawed from boards, producing sticks having rectangular cross sections. The saw cuts are not perfectly smooth, with the result that the corners of the sticks are slightly ragged or serrated. From such corners, almost unavoidably, the kite flier gets splinters in his hands. If the kite stick is threaded through a hole in the kite lifting surface material in the process of assembly, fine splinters rise from the serrated corners of the stick and snag the material preventing further passage of the stick, sometimes splitting the stick. When the stick is bent, the stresses in the corners, particularly on the tension side of the stick, cause minute local failures to occur at the discontinuities caused by the rough serrated edge and the stick is made susceptible to early failure.

In the past, a large number of remedies for the faults of wooden kite sticks have been tried, none of which has been completelysatisfactory. Lumber used for cutting sticks has been hand-selected, board by board, by an expert; this is a slow expensive process unsuited to mass production. It is especially frustrating when the supply of good boards dwindles or disappears. Kite sticks have been milled instead of being sawed, to round the corners to reduce splintering and splitting; this also increases costs. Other materials have been tried. Split bamboo is too flexible and too heavy. The same is true of the stiffest, lightest plastic materials, such as PVC (polyvinyl chloride), even when extruded in thin-walled section having high section moments of inertia. Plastics filled with fibers such as glass, (or the new carbon or boron filaments) are too expensive. Metal sticks are relatively low resistance conductors of electricity; this introduces a prohibitive risk when a kite falls across bare electric wires and the kite flier attempts to recover it.

Prior to this invention, the kite stick problem was unsolved. Some quantity manufacturers of kites adopted plastic sticks for their kites, despite the fact that the resulting kites were too heavy to fly in light winds and too rubbery to fly in strong winds. Other manufacturers designed kites with straight sticks that do not bend appreciably. Most manufacturers limited themselves to kites of low aspect ratio which are insensitive touneven bends in the sticks and they did not use construction in which the sticks pass through holes in the lifting surface material. Others avoided sticks by the use of inflatable kites; these were of inferior flight performance because of their high aerodynamic drag and poor lift. Flexible wind-formed kites appeared, like the Scott Sled, using straight sticks and the Rogallo kite (U.S. Pat. No. 2,546,078) using no sticks at all.

In attempting to solve the stick problem the Airplane Kite Company decided that unless plastics become stiffer, lighter and cheaper, the best material is wood, and that some type of lamination is necessary to obtain uniformity of quality for mass production. Special plywood was constructed having three plies all having the grain running parallel, out of which sticks were to be sawed. Uniformity and a mass source of supply were achieved but the problems of corner splintering were made worse, because now each rectangular cross section, with its three plies, had a total of twelve corners instead of four, where grain separation could start. Lamination of wood without corners was seen to be necessary; the present invention accomplishes this resuit.

The objects of the present invention include the following:

To produce kites having sticks which a. Greatly reduce or eliminate unsymmetrical stick bending and thereby greatly reduce kite dissymmetry due to this cause, especially on kites of high aspect ratio, on which such dissymmetry produces large changes of lateral trim.

b. Greatly reduce or eliminate stick breaking, in a stick which is of light weight and which has a high degree of structural stiffness, without the known faults of plastic or metal sticks.

c. Greatly reduce or eliminate splintering and grain separation in wooden sticks.

d. Are available in large quantities for mass production.

e. Are of uniform quality, free of damaging defects.

f. Permit insertion through the lifting surface of the kite, without snagging, in the process of assembly of the kite.

g. Permit the kite design to be sporty, maneuverable and spirited in its flight, exciting to fly, and able to strike the ground at full speed without stick breakage.

FIGS. 1, 2, 3 and show kites embodying the present invention. The front or leading edge of each kite is toward the top of the paper. The kites in FIGS. 1 and 2 are seen from above. The kite in FIG. 3 is seen from beneath. The kite in FIG. 5 is reversible, either side serving as either top or bottom. I FIGS. 1 and 2 show kites as taught by US. Pat. No. 3,335,984. These kites have forms which are concave upwardly, this concavity being present both laterally (side to side on the drawing)'and longitudinally v(bottom to top on the drawing). FIG. 3 shows a keel kite having a strongly bent vwing stick, with the keellaid over to one side, for purposes of illustration, flat against the kite. FIG. 4 shows the keel for the kite of FIG. 3. FIG. 5 shows a flexible wind-formed kite with curved sticks.

FIGS. 6 through 11 show details of the nonsplintering laminated dual-rounded kite stick of this invention. FIGS. 6 and 7 are partial views at sections 6-6 and 7-7, respectively, of FIGS. 1, 2, 3 and 5, showing cross sections of the wing stick and the body stick respectively. FIGS. 8 and 10 are partial views at 8--8 and 10-10, respectively, of FIGS. 1, 2, 3 and 5. FIGS. 8 and 9show the slotting of the tips of the wing sticks and FIGS. '10 and 1 1 show the slotting of the nose sticks and body sticks.

The novel kite stick in the present invention consists of two or more smooth-surfaced round wooden members glued together side by side full length along the line of tangent contact, to form a unified structural beam. Such a stick has no ragged or serrated edges, and has no corners where stress concentrations can build up, which can cause grain separation and splinters, leading to splitting or snapping of sticks. The sticks of this invention have smooth rounded surfaces which can be pushed through openings in the lifting surface material of the kite without snagging. This property enables the kite innovator to offer numerous new kites, which are light, efficient and inexpensive, using the new high strength synthetic fabric materials, such as the DuPont product, TYVEK, for the lifting surface material of the kite.

The dual structural beam construction of the kite stick provides the advantages of lamination without the disadvantage of easy separation of the plies, common in conventional plywood. A defect in one of the two members of the beam is reinforced by the other member of the beam, so that, with the elimination of corner stresses as described above, and with this reinforcement against local defects, remarkably large bends can be tolerated by the sticks without failure, and the problems of uneven bending disappear for all practical purposes.

Flight tests comparing routine production dualrounded sticks, as taught here, against selected high quality mahogany sticks of rectangular section showed a clear ability of the dual rounded stick of this invention to maintain trimmed flight to higher wind speeds, due to the improved symmetry of wing bending. As a result, the hand selection of lumber and the testing of sticks is no longer necessary when the new dualrounded sticks are used.

Novel kites using these new sticks make use of their property of bending easily in one direction while remaining stiff in a direction perpendicular to the plane of the easy bend. Typically, the body stick or longitudinal stick of a bird-like kite is installed flat relative to the lifting surface material, in position to bend easily, concave up, and the lateral stick or wing stick is installed on edge relative to the lifting surface material, in a position to resist wing bending. In typical rough treatment of a kite causing a stick to break, it is the body stick which is usually broken, and not the wing stick. In this invention, the body stick, placed flat in the position for easy bending, is rendered immune to breakage. Tests were made of kites like FIGS. 1 and 2, having projecting nose sticks of the new dual-round construction. These test kites were deliberately flown straight down into the ground in high winds. The kites hit the ground and bounced. In no case was there a stick failure. Kites of this invention have been tested intensively over an elapsed period of six months, and no stick has yet broken in testing.

The new dual-round kite sticks have also proven to be attractive for manufacturing. Individual members of the sticks are often crooked, yet the unified dual stick is straight. The supply problem is solved; good quality birch dowels for use in making these sticks can be obtained without delay in quantities up to car loads. Unlike plastics, the sticks are stiff and light. Unlike metals, they are not good conductors of electricity. They permit the kite innovator to use strongly bent sticks, and to use long slender wings, making the best aerodynamic forms available for kites.

Now referring specifically to the drawing:

In FIG. 1 a bird kite of this invention is shown, consisting of lifting surface 1 of a bird-like silhouette, supported by dual-rounded lateral beam 2, serving as the wing stick, and dual-rounded longitudinal beam 3, serving as the body stick. Wing stick 2 is placed on edge and body stick 3 is placed flat relative to lifting surface 1. Border string 4 forms a closed loop engaging slots in the ends of sticks 2 and 3, and is secured to lifting surface 1 by means of several lengths of adhesive tape 5. The kite is seen from above; the ends of sticks 2 and 3 are higher than their midsections, producing a general upward-facing concavity in the kite surface both laterally and longitudinally. Wing stick 1 is also bent rearward at the tips, producing rearward-facing concavity in this stick. Sticks 2 and 3 are bound together where they cross. An opening is provided in surface 1 just rearward of the point where the sticks cross, to permit the flying string beneath the kite to be tied up around stick 3 at that point. The construction shown in FIG. 1 is suitable for kites using a soft plastic film material for lifting surface 1.

FIG. 2 shows another bird kite of somewhat different construction, suitable for use with a strong tearresistant material for lifting surface 1, with features suitable for large kites. Wing sticks 7, nose stick 8, and body stick 9 engage in central four-way socket fitting 6 which is attached adhesively to lifting surface 1. The

use of the central fitting 6 reduces the maximum stick length and resulting package length to about half of that otherwise required. Wing sticks 7 and body stick 9 are each threaded through two holes 10 in lifting surface 1, to position them accurately and to stabilize them against sideward buckling. Each of wing sticks 7 engages lifting surface 1 by means of a slot at its outer end, entering a hole in the wing tip region of lifting surface I. The rearmost portion of body stick 9 fits in a socket formed of adhesive tape attached by such tape at the tail of lifting surface 1. In FIG. 2 nose string 11 is taped to lifting surface 1 at the shoulders of the bird-like silhouette. The functions performed by border string 4 in FIG. 1 are performed by nose string 11 and the tough material of lifting surface 1 in FIG. 2.

FIG. 3 shows a keel kite making use of multiple holes in tough tear resistant lifting surface 1 through which wing stick 2 is threaded, giving stick 2 a pronounced curvature. Stick 12, which may be a simple round sectioned dowel of small size, is threaded through matching holes in lifting surface 1 and in keel 13, which is also made of tear resistant material, lacing these parts together securely. The ends of stick 12 are slotted; each slot engages two thicknesses of tear resistant material, one thickness of the lifting surface 1 and one thickness of the keel 13.

FIG. 4 shows keel 13 from FIG. 3 laid out fiat. Holes 14 through which stick 12 is threaded (FIG. 3) may be seen to lie along a curved line. The function of the curve is to place more tension in some portions of the keel than in other portions, and to use this distribution of tension to bend stick 12 to the cambered line required by the kite design. When the kite is flying and the wind is light stick 12 tends to straighten, causing portions of keel 13 to go slack. When the wind is stronger, and string tension is greater, slackness disappears from the keel and the desired camber is produced in stick 12 and in lifting surface LBy means of the cambered keel, as described above a response to wind speed is achieved which the kite designer may use advantageously both in light winds and strong winds, applying well known aerodynamic principles. It may be seen that the kite of FIG. 3 consists entirely of surface parts which may be stamped out, and round sectioned sticks, and requires no factory assembly labor, this invention thereby permitting the kite to be produced at low cost.

In FIG. 5, a wind formed kite is shown, also of low cost construction. Tear resistant lifting surface material is used, through which dual-rounded sticks 15 are threaded, and engaged to the surface material by means of slots at their ends. The surface material is stretched out flat, laterally, bending sticks 15 as shown.

Sticks 2, 3, 7, 8, 9, and 15 as shown in FIGS. 1, 2, 3, and 5 are all of the dual-rounded construction, and stick 12 in FIG. 3 would also be of this construction if the bend imposed on it by keel 13 were very large.

FIG. 6 is a partial sectional view showing the cross section of the dual rounded stick, taken at sections 6-6 of FIGS. 1, 2, 3, and 5. At these locations, the dual-rounded stick is in its stiff position, on edge relative to the lifting surface, supporting the wing in FIGS. 1, 2, and 3.

FIG. 7 is a partial sectional view, taken at sections 7-7 of FIGS. 1 and 2. In these locations the dualrounded stick is in a position for easy bending, lying flat relative to the lifting surface.

As described previously, the dual rounded stick is a unified structural member consisting of long roundsectioned sticks in tangent contact side-by-side, forming a figure-8 structural cross section, rigidly glued together along substantially the entire lengths of the two round members, along the line of tangent contact. As compared to conventional plywood the glue area between the glued parts is much reduced while the results are improved. No evidence of glue is apparent on the completed dual-round stick.

The individual members which make up the dual stick are smooth, and free from all corners edges, splinters, and splits. The assembled dual stick is similarly free of these defects so that the dual stick may be threaded through holes in the lifting surface material without snagging and without cutting or sawing the material. As structural beams the properties of the dualrounded sticks of FIGS. 6 and 7 are superb, due to the elimination of corner stresses, splintering, and splitting, and also due to the FIG. 8 cross section, producing a stiff direction of installation (FIG. 6) and a flexible direction of installation (FIG. 7). Uniform bending and freedom from stick breakage are achieved by this construction, as described earlier.

FIG. 8 is partial view taken at 8-8 of FIGS. 1, 2, 3 and 5, showing tip slots 6 at the ends of the dual-round stick when it is installed in its stiff position, edgewise to the general plane of the lifting surface material.

FIG. 9 is a side view of the dual-round stick showing the same slotting as in FIG. 8. Either one of these two slots is used, avoiding a slot which would place a load on the glued joint between the two round-sectioned members.

FIG. 10 is a partial view taken at 10-10 of FIGS. 1 and 2, showing tip slot 17, at the end of the dual round stick when it is installed flat relative to the lifting surface material, in its easily bent position.

FIG. 11 is a side view of the dual-round stick showing the same slot as in FIG. 10.

I claim:

1. A kite comprising a lifting surface, a longitudinally positioned stick supporting said lifting surface, and a generally triangular keel beneath said kite, said keel being attached to said kite by said stick threaded through holes along the upper edge of said keel and through matching holes in said lifting surface.

2. In the kite of claim 1, said holes along the upper edge of said keel being arranged along a curved line, to distribute tension in said keel member and to distribute bending in said longitudinally positioned stick member,

as described.

Claims (2)

1. A kite comprising a lifting surface, a longitudinally positioned stick supporting said lifting surface, and a generally triangular keel beneath said kite, said keel being attached to said kite by said stick threaded through holes along the upper edge of said keel and through matching holes in said lifting surface.

2. In the kite of claim 1, said holes along the upper edge of said keel being arranged along a curved line, to distribute tension in said keel member and to distribute bending in said longitudinally positioned stick member, as described.

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