KITES AND GLIDERS
KITES are of very ancient origin, and in China,
Japan, and the Malayan Peninsula, they have been
used for many years as toys, and for the purposes
of exhibiting forms of men, animals, and particularly
dragons, in their periodical displays.
THE DRAGON KITE.--The most noted of all are
the dragon kites, many of them over a hundred
feet in length, are adapted to sail along majestically,
their sinuous or snake-like motions lending
an idea of reality to their gorgeously-colored appearance
in flight.
ITS CONSTRUCTION.--It is very curiously
wrought, and as it must be extremely light, bamboo
and rattan are almost wholly used, together
with rice paper, in its construction.
Fig. 33 shows one form of the arrangement, in
which the bamboo rib, A, in which only two sections
are shown, as B, B, form the backbone, and
these sections are secured together with pivot
pins C. Each section has attached thereto a
hoop, or circularly-formed rib, D, the rib passing
through the section B, and these ribs are
connected together loosely by cords E, which run
from one to the other, as shown.
These circular ribs, D, are designed to carry a
plurality of light paper disks, F, which are attached
at intervals, and they are placed at such
angles that they serve as small wing surfaces or
aeroplanes to hold the structure in flight.
_Fig. 33. Ribs of Dragon Kite_
THE MALAY KITE.--The Malay kite, of which
Fig. 34 shows the structure, is merely made up of
two cross sticks, A, B, the vertical strip, A, being
bent and rigid, whereas the cross stick, B, is light
and yielding, so that when in flight it will bend,
as shown, and as a result it has wonderful stability
due to the dihedral angles of the two surfaces. This kite
requires no tail to give it stability.
_Fig. 34. The Malay Kite._
DIHEDRAL ANGLES.--This is a term to designate
a form of disposing of the wings which has been
found of great service in the single plane machines.
A plane which is disposed at a rising
angle, as A, A, Fig. 35, above the horizontal line,
is called dihedral, or diedral.
_Fig. 35. Dihedral Angle._
This arrangement in monoplanes does away
with the necessity of warping the planes, or
changing them while in flight. If, however, the angle
is too great, the wind from either quarter is liable
to raise the side that is exposed.
THE COMMON KITE.--While the Malay kite has
only two points of cord attachment, both along
the vertical rib, the common kite, as shown in
Fig. 36, has a four-point connection, to which the
flying cord is attached. Since this form has no
dihedral angle, it is necessary to supply a tail,
which thus serves to keep it in equilibrium, while
in flight.
_Fig. 36. Common Kite._
Various modifications have grown out of the
Malay kite. One of these forms, designed by
Eddy, is exactly like the Malay structure, but instead
of having a light flexible cross piece, it is
bent to resemble a bow, so that it is rigidly held
in a bent position, instead of permitting the wind
to give it the dihedral angle.
THE BOW KITE.--Among the different types are
the bow kite, Fig. 37, and the sexagonal structure,
Fig. 38, the latter form affording an especially
large surface.
_Fig. 37. Bow Kite.-
_Fig. 38. Hexagonal Kite._
THE BOX KITE.--The most marked improvement
in the form of kites was made by Hargreaves,
in 1885, and called the box kite. It has wonderful
stability, and its use, with certain modifications,
in Weather Bureau experiments, have proven its
value.
It is made in the form of two boxes, A, B, open
at the ends, which are secured together by means
of longitudinal bars, C, that extends from one to
the other, so that they are held apart a distance,
approximately, equal to the length of one of the
boxes.
_Fig. 39. Hargreave Kite._
Their fore and aft stability is so perfect that
the flying cord D is attached at one point only,
and the sides of the boxes provide lateral stability
to a marked degree.
THE VOISON BIPLANE.--This kind of kite furnished
the suggestion for the Voison biplane,
which was one of the earlier productions in flying
machines.
Fig. 40 shows a perspective of the Voison plane,
which has vertical planes A, A, at the ends, and
also intermediate curtains B, B. This was found
to be remarkably stable, but during its turning
movements, or in high winds, was not satisfactory,
and for that reason was finally abandoned.
LATERAL STABILITY IN KITES NOT CONCLUSIVE AS
TO PLANES.--This is instanced to show that while
such a form is admirably adapted for kite purposes,
where vertical curtains are always in line
with the wind movement, and the structure is held
taut by a cord, the lateral effect, when used on a
machine which does not at all times move in line
with the moving air current. A condition is thus
set up which destroys the usefulness of the box
kite formation.
_Fig. 40. Voison Biplane._
THE SPEAR KITE.--This is a novel kite, with
remarkable steadiness and is usually made with
the wings on the rear end larger than those on
the forward end (Fig. 41), as thereby the cord
A can be attached to the spear midway between
the two sets of wings.
_Fig. 41. Spear Kite._
THE CELLULAR KITE.--Following out the suggestion
of the Hargreaves kite, numerous forms
embodying the principle of the box structure were
made and put on the market before the aeroplane
became a reality.
_Fig. 42. Cellular Kite._
A structure of this form is illustrated in Fig.
42. Each box, as A, B, has therein a plurality of
vertical and horizontal partitions, so that a number
of cells are provided, the two cell-like boxes
being held apart by a bar C, axially arranged.
This type is remarkably stable, due to the small
cells, and kites of this kind are largely used for
making scientific experiments.
THE TETRAHEDRAL KITE.--Prof. Bell, inventor
of the telephone, gave a great deal of study to
kites, which resulted in the tetrahedral formation,
as shown in Fig. 43.
_Fig. 43. Tetrahedral Kite._
The structure, apparently, is somewhat complicated,
but an examination of a single pair of
blades, as shown at A, shows that it is built up of
triangularly-formed pieces, and that the openings
between the pieces are equal to the latter, thereby
providing a form of kite which possesses equilibrium
to a great degree.
It has never been tried with power, and it is
doubtful whether it would be successful as a sustaining
surface for flying machines, for the same
reasons that caused failure with the box-like formation
of the Voison Machine.
THE DELTOID.--The deltoid is the simplest, and
the most easily constructed of all the kites. It is
usually made from stiff cardboard, A-shaped in
outline, as shown in Figs. 44 and 45, and bent along
a central line, as at A, forming two wings, each
of which is a right-angled triangle.
_Fig. 44. and 45. Deltoid Formation._
The peculiarity of this formation is, that it has
remarkable stability when used as a kite, with
either end foremost. If a small weight is placed
at the pointed end, and it is projected through the
air, it will fly straight, and is but little affected
by cross currents.
THE DUNNE FLYING MACHINE.--A top view of
this biplane is shown in Fig. 46. The A-shaped
disposition of the planes, gives it good lateral
stability, but it has the disadvantage under which
all aeroplanes labor, that the entire body of the
machine must move on a fore and aft vertical
plan in order to ascend or descend.
_Fig. 46. The Dunne Bi-plane._
This is a true deltoid formation, as the angle of
incidence of the planes is so disposed that when
the planes are horizontal from end to end, the inclination
is such as to make it similar to the deltoid
kite referred to.
ROTATING KITE.--A type of kite unlike the
others illustrated is a rotating structure, which
gives great stability, due to the gyroscopic action
on the supporting surfaces.
Fig. 47 shows a side view with the top in section.
The supporting surface is umbrella-shaped.
In fact, the ordinary umbrella will answer if not
dished too much. An angularly-bent piece of wire
A, provided with loops B, B, at the ends, serve as
bearings for the handle of the umbrella.
At the bend of the wire loop C, the cord D is
attached. The lower side of the umbrella top has
cup-shaped pockets E, near the margin, so arranged
that their open ends project in the same
direction, and the wind catching them rotates the
circular plane.
_Fig. 47. Rotable Umbrella Kite._
KITE PRINCIPLES.--A careful study of the examples
here given, will impress the novice with
one important fact, which, in its effect has a more
important bearing on successful flight, than all
the bird study and speculations concerning its
mysteries.
This fact, in essence, is, that the angle of the
kite is the great factor in flight next to the power
necessary to hold it. Aside from this, the
comparison between kites and aeroplanes is of no
practical value.
Disregarding the element of momentum, the
drift of a machine against a wind, is the same,
dynamically, as a plane at rest with the wind
moving past it. But there is this pronounced
difference: The cord which supports the kite
holds it so that the power is in one direction only.
When a side gust of wind strikes the kite it
is moved laterally, in sympathy with the kite,
hence the problem of lateral displacement is not
the same as with the aeroplane.
LATERAL STABILITY IN KITES.--In the latter the
power is definitely fixed with relation to the machine
itself, and if we should assume that a plane
with a power on it sufficient to maintain a flight
of 40 miles an hour, should meet a wind moving
at the same speed, the machine would be stationary
in space.
Such a condition would be the same, so far as
the angles of the planes are concerned, with a
kite held by a string, but there all similarity in
action ends.
The stabilizing quality of the kite may be perfect,
as the wind varies from side to side, but the
aeroplane, being free, moves to the right or to
the left, and does not adjust itself by means of a
fixed point, but by a movable one.
SIMILARITY OF FORE AND AFT CONTROL.--Fore
and aft, however, the kite and aeroplane act the
same. Fig. 48 shows a diagram which illustrates
the forces which act on the kite, and by means
of which it adjusts its angle automatically.
Let us assume that the kite A is flown from
a cord B, so that its angle is 22 1/2 degrees, the
wind being 15 miles per hour to maintain the
cord B at that angle. When the wind increases
to 20 miles an hour there is a correspondingly
greater lift against the kite.
_Fig. 48. Action of Wind forces on Kite._
As its angle is fixed by means of the loop C,
it cannot change its angle with reference to the
cord, or independently of it, and its only course
is to move up higher and assume the position
shown by the figure at D, and the angle of incidence
of the kite is therefore changed to 15 degrees,
or even to 10 degrees.
In the case of the aeroplane the effect is similar
from the standpoint of power and disposition
of the planes. If it has sufficient power, and the
angle of the planes is not changed, it will ascend;
if the planes are changed to 15 degrees to correspond
with the kite angle it will remain stationary.
GLIDING FLIGHT.--The earliest attempt to fly
by gliding is attributed to Oliver, a Monk of
Malmesbury who, in 1065 prepared artificial
wings, and with them jumped from a tower, being
injured in the experiment.
Nearly 700 years later, in 1801, Resnier, a
Frenchman, conducted experiments with varying
results, followed by Berblinger, in 1842, and
LeBris, a French sailor, in 1856.
In 1884, J. J. Montgomery, of California, designed
a successful glider, and in 1889 Otto and
Gustav Lilienthal made the most extended tests,
in Germany, and became experts in handling
gliders.
Pilcher, in England, was the next to take up the
subject, and in 1893 made many successful glides,
all of the foregoing machines being single plane
surfaces, similar to the monoplane.
Long prior to 1896 Octave Chanute, an
engineer, gave the subject much study, and in that
year made many remarkable flights, developing
the double plane, now known as the biplane.
He was an ardent believer in the ability of man
to fly by soaring means, and without using power
for the purpose.
It is doubtful whether gliders contributed much
to the art in the direction of laterally stabilizing
aeroplanes. They taught useful lessons with respect
to area and fore and aft control.
The kite gave the first impulse to seek out a
means for giving equilibrium to planes, and
Montgomery made a kite with warping wings as
early as 1884.
Penaud, a Frenchman, in 1872, made a model
aeroplane which had the stabilizing means in the
tail. All these grew out of kite experiments; and
all gliders followed the kite construction, or the
principles involved in them, so that, really, there
is but one intervening step between the kite and
the flying machine, as we know it, the latter being
merely kites with power attached, as substitutes
for the cords.
ONE OF THE USES OF GLIDER EXPERIMENTS.--
There is one direction in which gliders are valuable
to the boy and to the novice who are interested
in aviation. He may spend a lifetime in
gliding and not advance in the art. It is
questionable whether in a scientific way it will be of
any service to him; but experiments of this character
give confidence, the ability to quickly grasp
a situation, and it will thus teach self reliance in
emergencies.
When in a glider quick thinking is necessary.
The ability to shift from one position to another;
to apply the weight where required instantaneously;
to be able during the brief exciting moment
of flight to know just what to do, requires alertness.
Some are so wedded to the earth that slight
elevation disturbs them. The sensation in a
glider while in flight is unlike any other experience.
It is like riding a lot of tense springs, and the
exhilaration in gliding down the side of a hill,
with the feet free and body suspended, is quite
different from riding in an aeroplane with power
attached.
HINTS IN GLIDING.--It seems to be a difficult
matter to give any advice in the art of gliding. It
is a feat which seems to necessitate experiment
from first to last. During the hundreds of tests
personally made, and after witnessing thousands
of attempts, there seems to be only a few suggestions
or possible directions in which caution might
be offered.
First, in respect to the position of the body at
the moment of launching. The glider is usually
so made that in carrying it, preparatory to making
the run and the leap required to glide, it is held
so that it balances in the hands.
Now the center of air pressure in gliding may
not be at the same point as its sustaining weight
when held by the hand, and furthermore, as the
arm-pits, by which the body of the experimenter
are held while gliding, are not at the same point,
but to the rear of the hands, the moment the glider
is launched too great a weight is brought to the
rear margin of the planes, hence its forward end
lifts up.
This condition will soon manifest itself, and be
corrected by the experimenter; but there is another
difficulty which is not so easy to discover
and so quick to remedy, and that is the swing of
the legs the moment the operator leaves the
ground.
The experimenter learns, after many attempts,
that gliding is a matter of a few feet only, and he
anticipates landing too soon, and the moment he
leaps from the ground the legs are swung forwardly
ready to alight.
This is done unconsciously, just as a jumper
swings his legs forwardly in the act of alighting.
Such a motion naturally disturbs the fore and aft
stability of the gliding machine, by tilting up the
forward margin, and it banks against the air,
instead of gliding.
The constant fear of all gliders is, that the
machine will point downwardly, and his motion,
as well as the position of the body, tend to shoot
it upwardly, instead.