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1； and four intermediate vertical lines are then
drawn； as 2； 3； 4； 5； thus providing five divisions；
each eight feet wide。 In the first division the
planes A； B； are placed； and the tail； or elevator
C； is one…half the width of the last division。
_Fig。 58。 Plan of Monoplane。_
The frame is 3 1/2 feet wide at its forward end；
and tapers down to a point at its rear end； where
the vertical control plane D is hinged； and the
cross struts E； E； are placed at the division lines
3； 4； 5。
The angles of the planes； with relation to the
frame； are usually greater than in the biplane；
for the reason that the long tail plane requires
a greater angle to be given to the planes when
arising； or； instead of this； the planes A； B； are
mounted high enough to permit of sufficient angle
for initiating flight without injuring the tail D。
Some monoplanes are built so they have a support
on wheels placed fore and aft。 In others
the tail is supported by curved skids； as shown
at A； Fig。 59； in which case the forward
supporting wheels are located directly beneath the planes。
As the planes are at about eighteen degrees
angle； relative to the frame； and the tail plane
B is at a slight negative angle of incidence； as
shown at the time when the engine is started； the
air rushing back from the propeller； elevates the
tail； and as the machine moves forwardly over
the ground； the tail raises still higher； so as to
give a less angle of incidence to the planes while
skimming along the surface of the ground。
_Fig。 59。 Side Elevation； Monoplane。_
In order to mount； the tail is suddenly turned
to assume a sharp negative angle； thus swinging
the tail downwardly； and this increases the angle
of planes to such an extent that the machine leaves
the ground； after which the tail is brought to the
proper angle to assure horizontal flight。
The drawing shows a skid at the forward end；
attached to the frame which carries the wheels。
The wheels are mounted beneath springs so that
when the machine alights the springs yield sufficiently
to permit the skids to strike the ground；
and they； therefore； act as brakes； to prevent the
machine from traveling too far。
CHAPTER X
POWER AND ITS APPLICATION
THIS is a phase of the flying machine which has
the greatest interest to the boy。 He instinctively
sees the direction in which the machine has its
life；its moving principle。 Planes have their
fascination； and propellers their mysterious elements；
but power is the great and absorbing question
with him。
We shall try to make its application plain in
the following pages。 We have nothing to do here
with the construction and operation of the motor
itself； as； to do that justice； would require pages。
FEATURES IN POWER APPLICATION。It will be
more directly to the point to consider the following
features of the power and its application：
1。 The amount of power necessary。
2。 How to calculate the power applied。
3。 Its mounting。
WHAT AMOUNT OF POWER IS NECESSARY。In the
consideration of any power plant certain calculations
must be made to determine what is required。
A horse power means the lifting of a certain
weight； a definite distance； within a specified
time。
If the weight of the vehicle； with its load； are
known； and its resistance； or the character of the
roadway is understood； it is a comparatively easy
matter to calculate just how much power must be
exerted to overcome that resistance； and move the
vehicle a certain speed。
In a flying machine the same thing is true； but
while these problems may be known in a general
way； the aviator has several unknown elements
ever present； which make estimates difficult to
solve。
THE PULL OF THE PROPELLER。Two such factors
are ever present。 The first is the propeller
pull。 The energy of a motor； when put into a
propeller； gives a pull of less than eight pounds
for every horse power exerted。
FOOT POUNDS。The work produced by a motor
is calculated in Foot Pounds。 If 550 pounds
should be lifted； or pulled； one foot in one second
of time； it would be equal to one horse power。
But here we have a case where one horse power
pulls only eight pounds； a distance of one foot
within one second of time； and we have utilized
less than one sixty…fifth of the actual energy produced。
SMALL AMOUNT OF POWER AVAILABLE。This is
due to two things： First； the exceeding lightness
of the air； and its great elasticity； and； second；
the difficulty of making a surface which； when it
strikes the air； will get a sufficient grip to effect
a proper pull。
Now it must be obvious； that where only such
a small amount of energy can be made available；
in a medium as elusive as air； the least change； or
form； of the propeller； must have an important
bearing in the general results。
HIGH PROPELLER SPEED IMPORTANT。Furthermore；
all things considered； high speed is important
in the rotation of the propeller； up to a certain
point； beyond which the pull decreases in
proportion to the speed。 High speed makes a
vacuum behind the blade and thus decreases the
effective pull of the succeeding blade。
WIDTH AND PITCH OF BLADES。If the blade is
too wide the speed of the engine is cut down to a
point where it cannot exert the proper energy； if
the pitch is very small then it must turn further to
get the same thrust； so that the relation of diameter；
pitch and speed； are three problems far from
being solved。
It may be a question whether the propeller form；
as we now know it； is anything like the true or
ultimate shape； which will some day be discovered。
EFFECT OF INCREASING PROPELLER PULL。If the
present pull could be doubled what a wonderful
revolution would take place in aerial navigation；
and if it were possible to get only a quarter of
the effective pull of an engine； the results would
be so stupendous that the present method of flying
would seem like child's play in comparison。
It is in this very matter；the application of
the power； that the bird； and other flying creatures
so far excel what man has done。 Calculations
made with birds as samples； show that many
of them are able to fly with such a small amount
of power that； if the same energy should be applied
to a flying machine； it would scarcely drive
it along the ground。
DISPOSITION OF THE PLANES。The second factor
is the disposition or arrangement of the planes
with relation to the weight。 Let us illustrate this
with a concrete example：
We have an aeroplane with a sustaining surface
of 300 square feet which weighs 900 pounds；
or 30 pounds per square foot of surface。
DIFFERENT SPEEDS WITH SAME POWER。Now； we
may be able to do two things with an airship under
those conditions。 It may be propelled through
the air thirty miles an hour； or sixty miles； with
the expenditure of the same powe