Swallowtail kite

A kite of the swallowtail sled type, comprising a central panel, or canopy of light-weight sheet material, such as paper or thin plastic film, generally in a rectangular shape. It has two long parallel sides, with shorter leading and trailing edges. The leading edge is similar to a shallow isosceles triangle. The trailing edge is cut away also in the form of an isosceles triangle but with the height of the triangle greater than that of the leading edge. Two triangular lateral panels are attached, one to each of the sides of the central panel. At least three slender stiffening battens are attached, one to each of the long sides of the central canopy and one along the center line. A tension cord means or halter, shorter than the width of the central panel is tied between the trailing ends of the two battens.

CROSS-REFERENCE TO RELATED APPLICATION 
This application is related to my co-pending application, filed on the same 
date as this application, entitled: Hooded Kite, Ser. No. 043109, filed on 
May 29, 1979. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention. 
This invention lies in the field of kites. More particularly it concerns 
improvements in a type of kite called a sled. The improvements tending to 
make the kite fly more smoothly, even in turbulent wind and to fly at a 
shallower angle of attack, and thus at greater elevation, to avoid 
collapse, than prior art models. 
2. Description of the Prior Art. 
The prior art is described in books, such as that by Brummitt, entitled 
"Kites", Golden Press, New York, New York 1971. 
In the prior art there have been examples of sled type kites which are 
principally rectangular sheets of thin material stiffened by two parallel 
strips or battens one on each of the longitudinal edge of the sheet of the 
central panel. There are two triangular side panels or laterals with bases 
that equal in length to the long sides of the central panel and attached 
thereto. Cords are attached to each of the points of the side panels and 
these are joined together to form a bridle. The bridle is attached to a 
flight line in a conventional manner. 
These kites have been shown to be sensitive to collapse in turbulent wind. 
They also tend to fly at a high angle of attack, providing small 
lift-to-drag ratio, and thus fly at low elevation. 
SUMMARY OF THE INVENTION 
It is the primary object of this invention to provide an improved kite of 
the sled type, which has superior flying characteristics with extremely 
simple construction. 
A further object of this invention is to improve the collapse resistance of 
the sled type kite. 
These and other objects are realized, and the limitations of the prior art 
are overcome in this invention, by making several important modifications 
to the basic design of the sled type kite. 
In this invention the shape of the central panel has been altered from a 
rectangle, to one which is the shape of a swallowtail. That is, along the 
central axis of the central panel, the leading edge has been moved forward 
a selected distance in the shape of an isosceles triangle. The trailing 
edge has been cut back also in the shape of an isosceles triangle. 
However, the lead of the trailing edge is greater than the lead of the 
front edge. This provides for a projecting front tip of the central panel 
that is in the clear, and is well adapted to catch the wind and to 
reinflate the kite if it should collapse. The modification to the trailing 
edge provides enough opportunity for the wind to spill over the trailing 
edge and provides additional stability to the flying. 
A further improvement of this invention lies in the use of a cord in 
tension, or halter, across the trailing ends of the two outboard 
stiffening battens. The length of the cord is of the order of 0.6 of the 
nominal width of the central panel. This forces the sheet into a trough 
even with the slightest wind, and therefor provides a stronger reaction of 
the kite at low wind velocities. 
Because of the triangular shape of the leading edge, it is necessary to 
have a third stiffening rod or batten along the axis of the central panel, 
or canopy, to support the point.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, and in particular, to FIG. 1, there is shown 
a plane view of one embodiment of this invention, indicated generally by 
numeral 10. The kite 10 comprises a central panel or canopy indicated 
generally by the numeral 12, which has two long sides 26A and 26B, which 
are attached to two longitudinal stiffening battens 28A and 28B. 
The embodiment shown in FIG. 1 has a central stiffening batten 28C along 
the longitudinal axis of the canopy, and the smaller sub-panels are mirror 
images of each other, and are identified by the numerals 16A and 16B. 
In this embodiment the leading edge is a broken line, made up of two 
segments 17A and 17B, joined together at the central tip 21 of the canopy. 
The lines 17A and 17B form the two equal sides of a shallow isosceles 
triangle, the base of which is equal to the width 32 of the canopy at the 
front ends of the battens, 28A and 28B. 
The trailing edge is similarly cut back in the form of an isosceles 
triangle, the two equal sides of which are 20A and 20B, which join 
together at point 23 which is at the trailing edge of the central batten 
28C. The height of the rear triangle is indicated at 24, which is of 
greater dimension than the height 22 of the leading edge triangle. Thus 
the central batten is shorter than the two side battens. 
There are two side panels or laterals, indicated generally by the numerals 
14A and 14B. The bases of these triangles are equal in length to the side 
edges of the canopy and are attached thereto. The points 50A and 50B of 
the side laterals 14A and 14B are closer to the leading edge 17A, 17B of 
the kite, than to the trailing edge, 20A, 20B. Means are provided to 
attach two cords 38A and 38B at these two tips of the laterals, which, as 
shown in FIGS. 2 and 3, can be joined together at point 48, and to a 
flight line 44, so as to provide a bridle, to hold the side panels 
somewhat parallel to each other. Thus there would be a more-or-less 
semicylindrical shape to the canopy when there is at least a weak wind 
blowing into the underside of the kite. 
A tension member or halter 40, which may be a cord, is tied between the two 
trailing ends of the side battens 28A, 28B. The length of the halter can 
be in the range of 50% to 70% of the width 32 of the canopy at the 
trailing edge. A preferred value is 60% of 32. 
Like conventional models of the sled type kites, this embodiment has no 
lateral stiffening members. 
So far as general dimensions are concerned, the kite can of course be made 
of any desired size, however some general ratio of dimensions are 
preferred as follows. 
The width 32 is in the range of 0.75 to 0.85 of the length 30 with a 
preferred value of 0.8. The dimension 36 is in the range of 0.2 to 0.35 of 
the length 30. The dimension 34 is in the range of 0.2 to 0.3 of the 
length 30. The position of the points of attachment 50A, 50B of the bridle 
should be such that a line drawn between these points, such as dashed line 
20 will divide the area of the canopy into two areas, a front area A, and 
a rear area B, such that the ratio of A to the total area (A & B) is in 
the range of 0.25 to 0.35, with a preferred value of 0.3. 
In the sled type kites their greatest difficulty is their tendency to 
collapse. If wind conditions are so unfavorable as to cause a collapse, 
the kite of this invention automatically reopens without the need for 
manipulation of the flying line by the flyer. This occurs because in a 
collapsed state, with the two outboard battens and most of the canopy 
brought together, and parallel to the wind, the center batten and apex 
area still catch the wind and cause the entire canopy to reopen. The whole 
episode of collapse and reopening usually occurs in a time interval of 
less than two seconds. 
I have found that an additional contributor to collapse is the fact that 
the battens are floppy at the trailing end. Even in mild turbulence, they 
occasionally flop outwardly, simultaneously both spilling the necessary 
pressure on the windward side of the canopy, and also causing the leading 
ends of the battens to come together. The result is collapse. This is 
prevented by the use of the halter 40 that ties the trailing ends of the 
battens with a fixed maximum spacing. 
FIGS. 2 and 3 show views of the kite of FIG. 1 under flying conditions, 
with the wind blowing in accordance with arrows 46 for example. It will be 
seen that the bridle 38A, and 38B tends to hold the side panels more or 
less parallel, therefore forming the kite into a cylindrical shape. The 
halter 40 aids this by limiting the maximum spacing between the trailing 
ends of the side battens. 
While the invention has been described with a certain degree of 
particularity, it is manifest that many changes may be made in the details 
of construction and the arrangement of components without departing from 
the spirit and scope of this disclosure. It is understood that the 
invention is not limited to the embodiments set forth herein for purposes 
of exemplification, but is to be limited only by the scope of the attached 
claim or claims, including the full range of equivalency to which each 
element thereof is entitled.