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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