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11 Aeroplanes
by J. S. Zerbe
Scanned by Charles Keller with OmniPage Professional OCR software
AEROPLANES
This work is not intended to set forth the exploits of aviators
nor to give a history of the Art. It is a book of instructions
intended to point out the theories of flying, as given by the
pioneers, the practical application of power to the various
flying structures; how they are built, the different methods of
controlling them; the advantages and disadvantages of the types
now in use; and suggestions as to the directions in which
improvements are required.
It distinctly points out wherein mechanical flight differs
from bird flight, and what are the relations of shape, form, size
and weight. It treats of kites, gliders and model aeroplanes,
and has an Interesting chapter on the aeroplane and its uses In
the great war. All the illustrations have been specially prepared
for the work.
Every Boy's Mechanical Library
AEROPLANES
BY
J. S. ZERBE, M. E.
Author of Automobiles--Motors
COPYRIGHT, 1915, BY
CUPPLES & LEON COMPANY
NY
CONTENTS
INTRODUCTORY
CHAPTER I. THEORIES AND FACTS ABOUT FLYING
The "Science" of Aviation. Machine Types. Shape
or Form not Essential. A Stone as a Flying Machine.
Power the Great Element. Gravity as Power. Mass
and Element in Flying. Momentum a Factor. Resistance.
How Resistance Affects Shape. Mass and Resistance.
The Early Tendency to Eliminate Momentum.
Light Machines Unstable. The Application of
Power. The Supporting Surfaces. Area not the Essential
Thing. The Law of Gravity. Gravity. Indestructibility
of Gravitation. Distance Reduces Gravitational
Pull. How Motion Antagonizes Gravity. A
Tangent. Tangential Motion Represents Centrifugal
Pull. Equalizing the Two Motions. Lift and Drift.
Normal Pressure. Head Resistance. Measuring Lift
and Drift. Pressure at Different Angles. Difference
Between Lift and Drift in Motion. Tables of Lift and
Drift. Why Tables of Lift and Drift are Wrong.
Langley's Law. Moving Planes vs. Winds. Momentum
not Considered. The Flight of Birds. The
Downward Beat. The Concaved Wing. Feather Structure
Considered. Webbed Wings. The Angle of Movement.
An Initial Movement or Impulse Necessary. A
Wedging Motion. No Mystery in the Wave Motion.
How Birds Poise with Flapping Wings. Narrow-
winged Birds. Initial Movement of Soaring Birds.
Soaring Birds Move Swiftly. Muscular Energy
Exerted by Soaring Birds. Wings not Motionless.
CHAPTER II. PRINCIPLES OF AEROPLANE FLIGHT
Speed as one of the Elements. Shape and Speed.
What "Square of the Speed" Means. Action of a
"Skipper." Angle of Incidence. Speed and Surface.
Control of the Direction of Flight. Vertical Planes.
CHAPTER III. THE FORM OR SHAPE OF FLYING MACHINES
The Theory of Copying Nature. Hulls of Vessels.
Man Does not Copy Nature. Principles Essential, not
Forms. Nature not the Guide as to Forms. The Propeller
Type. Why Specially-designed Forms Improve
Natural Structures. Mechanism Devoid of Intelligence.
A Machine Must Have a Substitute for Intelligence.
Study of Bird Flight Useless. Shape of
Supporting Surface. The Trouble Arising From Outstretched
Wings. Density of the Atmosphere. Elasticity
of the Air. "Air Holes." Responsibility for
Accidents. The Turning Movement. Centrifugal Action:
The Warping Planes.
CHAPTER IV. FORE AND AFT CONTROL
The Bird Type of Fore and Aft Control. Angle and
Direction of Flight. Why Should the Angle of the
Body Change. Changing Angle of Body not Safe. A
Non-changing Body. Descending Positions by Power
Control. Cutting off the Power. The Starting Movement.
The Suggested Type. The Low Center of Gravity.
Fore and Aft Oscillations. Application of the
New Principle. Low Weight not Necessary with Synchronously-
moving wings.
CHAPTEB V. DIFFERENT MACHINE TYPES AND THEIR CHARACTERISTICS
The Helicopter. Aeroplanes. The Monoplane. Its
Advantages. Its Disadvantages. The Bi-plane. Stability
in Bi-planes. The Orthopter. Nature's Type
not Uniform. Theories About Flight of Birds. Instinct.
The Mode of Motion. The Wing Structure.
The Wing Movement. The Helicopter Motion.
CHAPTER VI. THE LIFTING SURFACES OF AEROPLANES
Relative Speed and Angle. Narrow Planes Most Effective.
Stream Lines Along a Plane. The Center of
Pressure. Air Lines on the Upper Side of a Plane.
Rarefied Area. Rarefaction Produced by Motion. The
Concaved Plane. The Center of Pressure. Utilizing
the Rarefied Area. Changing Center of Pressure.
Plane Monstrosities. The Bird Wing Structure.
Torsion. The Bat's Wing. An Abnormal Shape. The
Tail as a Monitor.
CHAPTER VII. ABNORMAL FLYING STUNTS AND SPEEDS
Lack of Improvements in Machines. Men Exploited
and not Machines. Abnormal Flying of no Value.
The Art of Juggling. Practical Uses the Best Test.
Concaved and Convex Planes. How Momentum is a
Factor in Inverted Flying. The Turning Movement.
When Concaved Planes are Desirable. The Speed
Mania. Uses of Flying Machines. Perfection in Machines
Must Come Before Speed. The Range of its
Uses. Commercial Utility.
CHAPTER VIII. KITES AND GLIDERS
The Dragon Kite. Its Construction. The Malay
Kite. Dihedral Angle. The Common Kite. The Bow
Kite. The Box Kite. The Voison Bi-plane. Lateral
Stability in Kites, not Conclusive as to Planes. The
Spear Kite. The Cellular Kite. Tetrahedral Kite.
The Deltoid. The Dunne Flying Machine. Rotating
Kite. Kite Principles. Lateral Stability in Kites.
Similarity of Fore and Aft Control. Gliding Flight
One of the Uses of Glider Experiments. Hints in
Gliding.
CHAPTER IX. AEROPLANE CONSTRUCTION
Lateral and Fore and Aft. Transverse. Stability
and Stabilization. The Wright System. Controlling
the Warping Ends. The Curtiss Wings. The Farman
Ailerons. Features Well Developed. Depressing the
Rear End. Determining the Size. Rule for Placing
the Planes. Elevating Plane. Action in Alighting.
The Monoplane. The Common Fly. Stream Lines.
The Monoplane Form.
CHAPTER X. POWER AND ITS APPLICATION
Features in Power Application. Amount of Power
Necessary. The Pull of the Propeller. Foot Pounds
Small Amount of Power Available. High Propeller
Speed Important. Width and Pitch of Blades. Effect
of Increasing Propeller Pull. Disposition of the
Planes. Different Speeds with Same Power. Increase
of Speed Adds to Resistance. How Power Decreases
with Speed. How to Calculate the Power Applied.
Pulling Against an Angle. The Horizontal and the
Vertical Pull. The Power Mounting. Securing the
Propeller to the Shaft. Vibrations. Weaknesses in
Mounting. The Gasoline Tank. Where to Locate the
Tank. The Danger to the Pilot. The Closed-in Body.
Starting the Machine. Propellers with Varying Pitch.
CHAPTER XI. FLYING MACHINE ACCESSORIES
The Anemometer. The Anemograph. The Anemometrograph.
The Speed Indicator. Air Pressure Indicator.
Determining the Pressure From the Speed.
Calculating Pressure From Speed. How the Figures
are Determined. Converting Hours Into Minutes.
Changing Speed Hours to Seconds. Pressure as the
Square of the Speed. Gyroscopic:Balance. The Principles
Involved. The Application of the Gyroscope.
Fore and Aft Gyroscopic Control. Angle Indicator.
Pendulum Stabilizer. Steering and Controlling
Wheel. Automatic Stabilizing Wings. Barometers.
Aneroid Barometer. Hydroplanes. Sustaining Weight
of Pontoons. Shape of the Pontoon.
CHAPTER XII. EXPERIMENTAL WORK IN FLYING
Certain Conditions in Flying. Heat in Air. Motion
When in Flight. Changing Atmosphere. "Ascending
Currents." "Aspirate Currents." Outstretched Wings.
The Starting Point. The Vital Part of the Machine.
Studying the Action of the Machine. Elevating the
Machine. How to Practice. The First Stage. Patience
the Most Difficult Thing. The Second Stage.
The Third Stage. Observations While in Flight. Flying
in a Wind. First Trials in a Quiet Atmosphere.
Making Turns. The Fourth Stage. The Figure 8.
The Vol Plane. The Landing. Flying Altitudes.
CHAPTER XIII. THE PROPELLER
Propeller Changes. Propeller Shape. The Diameter.
Pitch. Laying Out the Pitch. Pitch Rule. Laminated
Construction. Laying up a Propeller Form.
Making Wide Blades. Propeller Outline. For High
Speeds. Increasing Propeller Efficiency.
CHAPTER XIV. EXPERIMENTAL GLIDERS AND MODEL AEROPLANES
The Relation of Models to Flying Machines. Lessons
From Models. Flying Model Aeroplanes. An
Efficient Glider. The Deltoid Formation. Racing
Models. The Power for Model Aeroplanes. Making
the Propeller. Material for the Propeller. Rubber.
Propeller Shape and Size. Supporting Surfaces.
CHAPTER XV. THE AEROPLANE IN THE GREAT WAR
Balloon Observations. Changed Conditions in Warfare.
The Effort to Conceal Combatants. Smokeless
Powder. Inventions to Attack Aerial Craft. Functions
of the Aeroplane in War. Bomb-throwing Tests.
Method for Determining the Movement of a Bomb.
The Great Extent of Modern Battle Lines. The Aeroplane
Detecting the Movements of Armies. The Effective
Height for Scouting. Sizes of Objects at Great
Distances. Some Daring Feats in War. The German
Taube. How Aeroplanes Report Observations. Signal
Flags. How Used. Casualties Due to Bombs
From Aeroplanes.
GLOSSARY
INTRODUCTORY
In preparing this volume on Flying Machines
the aim has been to present the subject in such a
manner as will appeal to boys, or beginners, in
this field of human activity.
The art of aviation is in a most primitive state.
So many curious theories have been brought out
that, while they furnish food for thought, do not,
in any way, advance or improve the structure of
the machine itself, nor are they of any service
in teaching the novice how to fly.
The author considers it of far more importance
to teach right principles, and correct reasoning
than to furnish complete diagrams of the details
of a machine. The former teach the art, whereas
the latter merely point out the mechanical
arrangements, independently of the reasons for
making the structures in that particular way.
Relating the history of an art, while it may be
interesting reading, does not even lay the foundations
of a knowledge of the subject, hence that
field has been left to others.
The boy is naturally inquisitive, and he is interested
in knowing WHY certain things are
necessary, and the reasons for making structures in
particular ways. That is the void into which
these pages are placed.
The author knows from practical experience,
while experimenting with and building aeroplanes,
how eagerly every boy inquires into details.
They want the reasons for things.
One such instance is related to evidence this
spirit of inquiry. Some boys were discussing the
curved plane structure. One of them ventured
the opinion that birds' wings were concaved on the
lower side. "But," retorted another, "why are
birds' wings hollowed?"
This was going back to first principles at one
leap. It was not satisfying enough to know that
man was copying nature. It was more important
to know why nature originated that type of formation,
because, it is obvious, that if such structures
are universal in the kingdom of flying creatures,
there must be some underlying principle
which accounted for it.
It is not the aim of the book to teach the art
of flying, but rather to show how and why the
present machines fly. The making and the using
are separate and independent functions, and of
the two the more important is the knowledge how
to make a correct machine.
Hundreds of workmen may contribute to the
building of a locomotive, but one man, not a
builder, knows better how to handle it. To
manipulate a flying machine is more difficult to
navigate than such a ponderous machine, because
it requires peculiar talents, and the building is
still more important and complicated, and requires
the exercise of a kind of skill not necessary
in the locomotive.
The art is still very young; so much is done
which arises from speculation and theories; too
much dependence is placed on the aviator; the
desire in the present condition of the art is to exploit
the man and not the machine; dare-devil exhibitions
seem to be more important than perfecting
the mechanism; and such useless attempts as
flying upside down, looping the loop, and characteristic
displays of that kind, are of no value to
the art.
THE AUTHOR.
AEROPLANES
CHAPTER I
THEORIES AND FACTS ABOUT FLYING
THE "SCIENCE" OF AVIATION.--It may be
doubted whether there is such a thing as a "science
of aviation." Since Langley, on May 6,
1896, flew a motor-propelled tandem monoplane
for a minute and an half, without a pilot, and the
Wright Brothers in 1903 succeeded in flying a
bi-plane with a pilot aboard, the universal opinion
has been, that flying machines, to be successful,
must follow the structural form of birds, and
that shape has everything to do with flying.
We may be able to learn something by carefully
examining the different views presented by
those interested in the art, and then see how they
conform to the facts as brought out by the actual
experiments.
MACHINE TYPES.--There is really but one type
of plane machine. While technically two forms
are known, namely, the monoplane and the
bi-plane, they are both dependent on outstretched
wings, longer transversely than fore and aft, so
far as the supporting surfaces are concerned, and
with the main weight high in the structure, thus,
in every particular, conforming to the form
pointed out by nature as the apparently correct
type of a flying structure.
SHAPE OR FORM NOT ESSENTIAL.--It may be
stated with perfect confidence, that shape or form
has nothing to do with the mere act of flying. It
is simply a question of power. This is a broad
assertion, and its meaning may be better understood
by examining the question of flight in a
broad sense.
A STONE AS A FLYING MACHINE.--When a stone
is propelled through space, shape is of no importance.
If it has rough and jagged sides its speed
or its distance may be limited, as compared with
a perfectly rounded form. It may be made in
such a shape as will offer less resistance to the air
in flight, but its actual propulsion through space
does not depend on how it is made, but on the
power which propelled it, and such a missile is a
true heavier-than-air machine.
A flying object of this kind may be so constructed
that it will go a greater distance, or require
less power, or maintain itself in space at
less speed; but it is a flying machine, nevertheless,
in the sense that it moves horizontally through the
air.
POWER THE GREAT ELEMENT.--Now, let us examine
the question of this power which is able to
set gravity at naught. The quality called energy
resides in material itself. It is something within
matter, and does not come from without. The
power derived from the explosion of a charge of
powder comes from within the substance; and so
with falling water, or the expansive force of
steam.
GRAVITY AS POWER.--Indeed, the very act of the
ball gradually moving toward the earth, by the
force of gravity, is an illustration of a power
within the object itself. Long after Galileo
firmly established the law of falling bodies it began
to dawn on scientists that weight is force.
After Newton established the law of gravitation
the old idea, that power was a property of each
body, passed away.
In its stead we now have the firmly established
view, that power is something which must have
at least two parts, or consist in pairs, or two elements
acting together. Thus, a stone poised on
a cliff, while it exerts no power which can be
utilized, has, nevertheless, what is called potential
energy. When it is pushed from its lodging place
kinetic energy is developed. In both cases,
gravity, acting in conjunction with the mass of
the stone, produced power.
So in the case of gunpowder. It is the unity of
two or more substances, that causes the expansion
called power. The heat of the fuel converting
water into steam, is another illustration of the
unity of two or more elements, which are necessary
to produce energy.
MASS AN ELEMENT IN FLYING.--The boy who
reads this will smile, as he tells us that the power
which propelled the ball through the air came
from the thrower and not from the ball itself.
Let us examine this claim, which came from a real
boy, and is another illustration how acute his mind
is on subjects of this character.
We have two balls the same diameter, one of
iron weighing a half pound, and the other of cotton
weighing a half ounce. The weight of one
is, therefore, sixteen times greater than the other.
Suppose these two balls are thrown with the
expenditure of the same power. What will be the
result! The iron ball will go much farther, or,
if projected against a wall will strike a harder
blow than the cotton ball.
MOMENTUM A FACTOR.--Each had transferred
to it a motion. The initial speed was the same,
and the power set up equal in the two. Why this
difference, The answer is, that it is in the
material itself. It was the mass or density which accounted
for the difference. It was mass multiplied
by speed which gave it the power, called, in
this case, momentum.
The iron ball weighing eight ounces, multiplied
by the assumed speed of 50 feet per second, equals
400 units of work. The cotton ball, weighing 1/2
ounce, with the same initial speed, represents 25
units of work. The term "unit of work" means
a measurement, or a factor which may be used to
measure force.
It will thus be seen that it was not the thrower
which gave the power, but the article itself. A
feather ball thrown under the same conditions,
would produce a half unit of work, and the iron
ball, therefore, produced 800 times more energy.
RESISTANCE.--Now, in the movement of any body
through space, it meets with an enemy at every
step, and that is air resistance. This is much
more effective against the cotton than the iron
ball: or, it might be expressed in another way:
The momentum, or the power, residing in the
metal ball, is so much greater than that within the
cotton ball that it travels farther, or strikes a
more effective blow on impact with the wall.
HOW RESISTANCE AFFECTS THE SHAPE.--It is because
of this counterforce, resistance, that shape
becomes important in a flying object. The metal
ball may be flattened out into a thin disk, and now,
when the same force is applied, to project it forwardly,
it will go as much farther as the difference
in the air impact against the two forms.
MASS AND RESISTANCE.--Owing to the fact that
resistance acts with such a retarding force on an
object of small mass, and it is difficult to set up a
rapid motion in an object of great density, lightness
in flying machine structures has been considered,
in the past, the principal thing necessary.
THE EARLY TENDENCY TO ELIMINATE MOMENTUM.--
Builders of flying machines, for several
years, sought to eliminate the very thing
which gives energy to a horizontally-movable
body, namely, momentum.
Instead of momentum, something had to be
substituted. This was found in so arranging the
machine that its weight, or a portion of it, would
be sustained in space by the very element which
seeks to retard its flight, namely, the atmosphere.
If there should be no material substance, like
air, then the only way in which a heavier-than-air
machine could ever fly, would be by propelling it
through space, like the ball was thrown, or by
some sort of impulse or reaction mechanism on
the air-ship itself. It could get no support from
the atmosphere.
LIGHT MACHINES UNSTABLE.--Gradually the
question of weight is solving itself. Aviators are
beginning to realize that momentum is a wonderful
property, and a most important element in
flying. The safest machines are those which have
weight. The light, willowy machines are subject
to every caprice of the wind. They are notoriously
unstable in flight, and are dangerous even
in the hands of experts.
THE APPLICATION OF POWER.--The thing now to
consider is not form, or shape, or the distribution
of the supporting surfaces, but HOW to apply
the power so that it will rapidly transfer a machine
at rest to one in motion, and thereby get
the proper support on the atmosphere to hold it
in flight.
THE SUPPORTING SURFACES.--This brings us to
the consideration of one of the first great problems
in flying machines, namely, the supporting
surfaces,--not its form, shape or arrangement,
(which will be taken up in their proper places), but
the area, the dimensions, and the angle necessary
for flight.
AREA NOT THE ESSENTIAL THING.--The history
of flying machines, short as it is, furnishes many
examples of one striking fact: That area has
but little to do with sustaining an aeroplane when
once in flight. The first Wright flyer weighed
741 pounds, had about 400 square feet of plane
surface, and was maintained in the air with a 12
horse power engine.
True, that machine was shot into the air by a
catapult. Motion having once been imparted to it,
the only thing necessary for the motor was to
maintain the speed.
There are many instances to show that when
once in flight, one horse power will sustain over
100 pounds, and each square foot of supporting
surface will maintain 90 pounds in flight.
THE LAW OF GRAVITY.--As the effort to fly
may be considered in the light of a struggle to
avoid the laws of nature with respect to matter,
it may be well to consider this great force as a
fitting prelude to the study of our subject.
Proper understanding, and use of terms is very
desirable, so that we must not confuse them.
Thus, weight and mass are not the same. Weight
varies with the latitude, and it is different at various
altitudes; but mass is always the same.
If projected through space, a certain mass
would move so as to produce momentum, which
would be equal at all places on the earth's surface,
or at any altitude.
Gravity has been called weight, and weight
gravity. The real difference is plain if gravity
is considered as the attraction of mass for mass.
Gravity is generally known and considered as a
force which seeks to draw things to the earth.
This is too narrow.
Gravity acts in all directions. Two balls suspended
from strings and hung in close proximity
to each other will mutually attract each other.
If one has double the mass it will have twice the
attractive power. If one is doubled and the other
tripled, the attraction would be increased six
times. But if the distance should be doubled the
attraction would be reduced to one-fourth; and
if the distance should be tripled then the pull
would be only one-ninth.
The foregoing is the substance of the law,
namely, that all bodies attract all other bodies
with a force directly in proportion to their mass,
and inversely as the square of their distance from
one another.
To explain this we cite the following illustration:
Two bodies, each having a mass of 4
pounds, and one inch apart, are attracted toward
each other, so they touch. If one has twice the
mass of the other, the smaller will draw the larger
only one-quarter of an inch, and the large one
will draw the other three-quarters of an inch,
thus confirming the law that two bodies will attract
each other in proportion to their mass.
Suppose, now, that these balls are placed two
inches apart,--that is, twice the distance. As
each is, we shall say, four pounds in weight, the
square of each would be 16. This does not mean
that there would be sixteen times the attraction,
but, as the law says, inversely as the square of
the distance, so that at two inches there is only
one-sixteenth the attraction as at one inch.
If the cord of one of the balls should be cut, it
would fall to the earth, for the reason that the
attractive force of the great mass of the earth is
so much greater than the force of attraction in
its companion ball.
INDESTRUCTIBILITY OF GRAVITATION.--Gravity
cannot be produced or destroyed. It acts between
all parts of bodies equally; the force being
proportioned to their mass. It is not affected by
any intervening substance; and is transmitted
instantaneously, whatever the distance may be.
While, therefore, it is impossible to divest matter
of this property, there are two conditions
which neutralize its effect. The first of these is
position. Let us take two balls, one solid and
the other hollow, but of the same mass, or density.
If the cavity of the one is large enough to receive
the other, it is obvious that while gravity is still
present the lines of attraction being equal at
all points, and radially, there can be no pull which
moves them together.
DISTANCE REDUCES GRAVITATIONAL PULL.--Or
the balls may be such distance apart that the attractive
force ceases. At the center of the earth
an object would not weigh anything. A pound
of iron and an ounce of wood, one sixteen times
the mass of the other, would be the same,--absolutely
without weight.
If the object should be far away in space it
would not be influenced by the earth's gravity;
so it will be understood that position plays an
important part in the attraction of mass for mass.
HOW MOTION ANTAGONIZES GRAVITY.--The second
way to neutralize gravity, is by motion. A
ball thrown upwardly, antagonizes the force of
gravity during the period of its ascent. In like
manner, when an object is projected horizontally,
while its mass is still the same, its weight is less.
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