aeroplanes by james slough zerbe

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Aeroplanes

by J. S. Zerbe***

September, 1998 [Etext #1445]

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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 aviatorsnor to give a history of the Art. It is a book of instructionsintended to point out the theories of flying, as given by thepioneers, the practical application of power to the variousflying structures; how they are built, the different methods ofcontrolling them; the advantages and disadvantages of the types


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now in use; and suggestions as to the directions in whichimprovements are required.

It distinctly points out wherein mechanical flight differsfrom bird flight, and what are the relations of shape, form, sizeand weight. It treats of kites, gliders and model aeroplanes,and has an Interesting chapter on the aeroplane and its uses Inthe great war. All the illustrations have been specially preparedfor the work.

Every Boy's Mechanical Library

AEROPLANES

BYJ. S. ZERBE, M. E.Author of Automobiles--Motors

COPYRIGHT, 1915, BYCUPPLES & LEON COMPANYNY

CONTENTS

INTRODUCTORY

CHAPTER I. THEORIES AND FACTS ABOUT FLYING

The "Science" of Aviation. Machine Types. Shapeor Form not Essential. A Stone as a Flying Machine.Power the Great Element. Gravity as Power. Massand 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 ofPower. The Supporting Surfaces. Area not the EssentialThing. The Law of Gravity. Gravity. Indestructibilityof Gravitation. Distance Reduces GravitationalPull. How Motion Antagonizes Gravity. ATangent. Tangential Motion Represents CentrifugalPull. Equalizing the Two Motions. Lift and Drift.Normal Pressure. Head Resistance. Measuring Liftand Drift. Pressure at Different Angles. DifferenceBetween 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. Momentumnot Considered. The Flight of Birds. TheDownward Beat. The Concaved Wing. Feather StructureConsidered. Webbed Wings. The Angle of Movement.An Initial Movement or Impulse Necessary. AWedging 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


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Exerted by Soaring Birds. Wings not Motionless.

CHAPTER II. PRINCIPLES OF AEROPLANE FLIGHTSpeed 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 MACHINESThe Theory of Copying Nature. Hulls of Vessels.Man Does not Copy Nature. Principles Essential, notForms. Nature not the Guide as to Forms. The PropellerType. Why Specially-designed Forms ImproveNatural Structures. Mechanism Devoid of Intelligence.A Machine Must Have a Substitute for Intelligence.Study of Bird Flight Useless. Shape ofSupporting Surface. The Trouble Arising From OutstretchedWings. Density of the Atmosphere. Elasticityof the Air. "Air Holes." Responsibility forAccidents. The Turning Movement. Centrifugal Action:

The Warping Planes.

CHAPTER IV. FORE AND AFT CONTROLThe Bird Type of Fore and Aft Control. Angle andDirection of Flight. Why Should the Angle of theBody Change. Changing Angle of Body not Safe. ANon-changing Body. Descending Positions by PowerControl. Cutting off the Power. The Starting Movement.The Suggested Type. The Low Center of Gravity.Fore and Aft Oscillations. Application of theNew Principle. Low Weight not Necessary with Synchronously-moving wings.

CHAPTEB V. DIFFERENT MACHINE TYPES AND THEIR CHARACTERISTICSThe Helicopter. Aeroplanes. The Monoplane. ItsAdvantages. Its Disadvantages. The Bi-plane. Stabilityin Bi-planes. The Orthopter. Nature's Typenot 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 AEROPLANESRelative Speed and Angle. Narrow Planes Most Effective.Stream Lines Along a Plane. The Center ofPressure. Air Lines on the Upper Side of a Plane.Rarefied Area. Rarefaction Produced by Motion. TheConcaved 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. TheTail as a Monitor.

CHAPTER VII. ABNORMAL FLYING STUNTS AND SPEEDSLack of Improvements in Machines. Men Exploitedand not Machines. Abnormal Flying of no Value.The Art of Juggling. Practical Uses the Best Test.Concaved and Convex Planes. How Momentum is a


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Factor in Inverted Flying. The Turning Movement.When Concaved Planes are Desirable. The SpeedMania. Uses of Flying Machines. Perfection in MachinesMust Come Before Speed. The Range of itsUses. Commercial Utility.

CHAPTER VIII. KITES AND GLIDERSThe Dragon Kite. Its Construction. The MalayKite. Dihedral Angle. The Common Kite. The BowKite. The Box Kite. The Voison Bi-plane. LateralStability in Kites, not Conclusive as to Planes. TheSpear Kite. The Cellular Kite. Tetrahedral Kite.The Deltoid. The Dunne Flying Machine. RotatingKite. Kite Principles. Lateral Stability in Kites.Similarity of Fore and Aft Control. Gliding FlightOne of the Uses of Glider Experiments. Hints inGliding.

CHAPTER IX. AEROPLANE CONSTRUCTIONLateral and Fore and Aft. Transverse. Stability

and Stabilization. The Wright System. Controllingthe Warping Ends. The Curtiss Wings. The FarmanAilerons. Features Well Developed. Depressing theRear End. Determining the Size. Rule for Placingthe Planes. Elevating Plane. Action in Alighting.The Monoplane. The Common Fly. Stream Lines.The Monoplane Form.

CHAPTER X. POWER AND ITS APPLICATIONFeatures in Power Application. Amount of PowerNecessary. The Pull of the Propeller. Foot PoundsSmall Amount of Power Available. High PropellerSpeed Important. Width and Pitch of Blades. Effectof Increasing Propeller Pull. Disposition of thePlanes. Different Speeds with Same Power. Increaseof Speed Adds to Resistance. How Power Decreaseswith Speed. How to Calculate the Power Applied.Pulling Against an Angle. The Horizontal and theVertical Pull. The Power Mounting. Securing thePropeller to the Shaft. Vibrations. Weaknesses inMounting. The Gasoline Tank. Where to Locate theTank. The Danger to the Pilot. The Closed-in Body.Starting the Machine. Propellers with Varying Pitch.

CHAPTER XI. FLYING MACHINE ACCESSORIESThe Anemometer. The Anemograph. The Anemometrograph.The Speed Indicator. Air Pressure Indicator.

Determining the Pressure From the Speed.Calculating Pressure From Speed. How the Figuresare Determined. Converting Hours Into Minutes.Changing Speed Hours to Seconds. Pressure as theSquare of the Speed. Gyroscopic:Balance. The PrinciplesInvolved. The Application of the Gyroscope.Fore and Aft Gyroscopic Control. Angle Indicator.Pendulum Stabilizer. Steering and ControllingWheel. Automatic Stabilizing Wings. Barometers.Aneroid Barometer. Hydroplanes. Sustaining Weight


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of Pontoons. Shape of the Pontoon.

CHAPTER XII. EXPERIMENTAL WORK IN FLYINGCertain Conditions in Flying. Heat in Air. MotionWhen in Flight. Changing Atmosphere. "AscendingCurrents." "Aspirate Currents." Outstretched Wings.The Starting Point. The Vital Part of the Machine.Studying the Action of the Machine. Elevating theMachine. How to Practice. The First Stage. Patiencethe Most Difficult Thing. The Second Stage.The Third Stage. Observations While in Flight. Flyingin 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 PROPELLERPropeller Changes. Propeller Shape. The Diameter.Pitch. Laying Out the Pitch. Pitch Rule. LaminatedConstruction. Laying up a Propeller Form.Making Wide Blades. Propeller Outline. For High

Speeds. Increasing Propeller Efficiency.

CHAPTER XIV. EXPERIMENTAL GLIDERS AND MODEL AEROPLANESThe Relation of Models to Flying Machines. LessonsFrom Models. Flying Model Aeroplanes. AnEfficient Glider. The Deltoid Formation. RacingModels. The Power for Model Aeroplanes. Makingthe Propeller. Material for the Propeller. Rubber.Propeller Shape and Size. Supporting Surfaces.

CHAPTER XV. THE AEROPLANE IN THE GREAT WARBalloon Observations. Changed Conditions in Warfare.The Effort to Conceal Combatants. SmokelessPowder. Inventions to Attack Aerial Craft. Functionsof the Aeroplane in War. Bomb-throwing Tests.Method for Determining the Movement of a Bomb.The Great Extent of Modern Battle Lines. The AeroplaneDetecting the Movements of Armies. The EffectiveHeight for Scouting. Sizes of Objects at GreatDistances. Some Daring Feats in War. The GermanTaube. How Aeroplanes Report Observations. SignalFlags. How Used. Casualties Due to BombsFrom Aeroplanes.

GLOSSARY

INTRODUCTORY

In preparing this volume on Flying Machinesthe aim has been to present the subject in such amanner as will appeal to boys, or beginners, inthis field of human activity.

The art of aviation is in a most primitive state.So many curious theories have been brought out


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that, while they furnish food for thought, do not,in any way, advance or improve the structure ofthe machine itself, nor are they of any servicein teaching the novice how to fly.

The author considers it of far more importanceto teach right principles, and correct reasoningthan to furnish complete diagrams of the detailsof a machine. The former teach the art, whereasthe latter merely point out the mechanicalarrangements, independently of the reasons formaking the structures in that particular way.

Relating the history of an art, while it may beinteresting reading, does not even lay the foundationsof a knowledge of the subject, hence thatfield has been left to others.

The boy is naturally inquisitive, and he is interestedin knowing WHY certain things are

necessary, and the reasons for making structures inparticular ways. That is the void into whichthese 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 thisspirit of inquiry. Some boys were discussing thecurved plane structure. One of them venturedthe opinion that birds' wings were concaved on thelower side. "But," retorted another, "why arebirds' wings hollowed?"

This was going back to first principles at oneleap. It was not satisfying enough to know thatman was copying nature. It was more importantto know why nature originated that type of formation,because, it is obvious, that if such structuresare universal in the kingdom of flying creatures,there must be some underlying principlewhich accounted for it.

It is not the aim of the book to teach the artof flying, but rather to show how and why the

present machines fly. The making and the usingare separate and independent functions, and ofthe two the more important is the knowledge howto make a correct machine.

Hundreds of workmen may contribute to thebuilding of a locomotive, but one man, not abuilder, knows better how to handle it. Tomanipulate a flying machine is more difficult tonavigate than such a ponderous machine, because


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it requires peculiar talents, and the building isstill more important and complicated, and requiresthe exercise of a kind of skill not necessaryin the locomotive.

The art is still very young; so much is donewhich arises from speculation and theories; toomuch dependence is placed on the aviator; thedesire in the present condition of the art is to exploitthe man and not the machine; dare-devil exhibitionsseem to be more important than perfectingthe mechanism; and such useless attempts asflying upside down, looping the loop, and characteristicdisplays of that kind, are of no value tothe art.

THE AUTHOR.

AEROPLANES

CHAPTER I

THEORIES AND FACTS ABOUT FLYING

THE "SCIENCE" OF AVIATION.--It may bedoubted whether there is such a thing as a "scienceof aviation." Since Langley, on May 6,1896, flew a motor-propelled tandem monoplanefor a minute and an half, without a pilot, and theWright Brothers in 1903 succeeded in flying abi-plane with a pilot aboard, the universal opinionhas been, that flying machines, to be successful,must follow the structural form of birds, andthat shape has everything to do with flying.

We may be able to learn something by carefullyexamining the different views presented bythose interested in the art, and then see how theyconform to the facts as brought out by the actualexperiments.

MACHINE TYPES.--There is really but one typeof plane machine. While technically two formsare known, namely, the monoplane and thebi-plane, they are both dependent on outstretched

wings, longer transversely than fore and aft, sofar as the supporting surfaces are concerned, andwith the main weight high in the structure, thus,in every particular, conforming to the formpointed out by nature as the apparently correcttype of a flying structure.

SHAPE OR FORM NOT ESSENTIAL.--It may bestated with perfect confidence, that shape or formhas nothing to do with the mere act of flying. It


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is simply a question of power. This is a broadassertion, and its meaning may be better understoodby examining the question of flight in abroad sense.

A STONE AS A FLYING MACHINE.--When a stoneis propelled through space, shape is of no importance.If it has rough and jagged sides its speedor its distance may be limited, as compared witha perfectly rounded form. It may be made insuch a shape as will offer less resistance to the airin flight, but its actual propulsion through spacedoes not depend on how it is made, but on thepower which propelled it, and such a missile is atrue heavier-than-air machine.

A flying object of this kind may be so constructedthat it will go a greater distance, or requireless power, or maintain itself in space atless speed; but it is a flying machine, nevertheless,

in the sense that it moves horizontally through theair.

POWER THE GREAT ELEMENT.--Now, let us examinethe question of this power which is able toset gravity at naught. The quality called energyresides in material itself. It is something withinmatter, and does not come from without. Thepower derived from the explosion of a charge ofpowder comes from within the substance; and sowith falling water, or the expansive force ofsteam.

GRAVITY AS POWER.--Indeed, the very act of theball gradually moving toward the earth, by theforce of gravity, is an illustration of a powerwithin the object itself. Long after Galileofirmly established the law of falling bodies it beganto dawn on scientists that weight is force.After Newton established the law of gravitationthe old idea, that power was a property of eachbody, passed away.

In its stead we now have the firmly establishedview, that power is something which must haveat least two parts, or consist in pairs, or two elementsacting together. Thus, a stone poised on

a cliff, while it exerts no power which can beutilized, has, nevertheless, what is called potentialenergy. When it is pushed from its lodging placekinetic energy is developed. In both cases,gravity, acting in conjunction with the mass ofthe stone, produced power.

So in the case of gunpowder. It is the unity oftwo or more substances, that causes the expansioncalled power. The heat of the fuel converting


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water into steam, is another illustration of theunity of two or more elements, which are necessaryto produce energy.

MASS AN ELEMENT IN FLYING.--The boy whoreads this will smile, as he tells us that the powerwhich propelled the ball through the air camefrom the thrower and not from the ball itself.Let us examine this claim, which came from a realboy, and is another illustration how acute his mindis on subjects of this character.

We have two balls the same diameter, one ofiron weighing a half pound, and the other of cottonweighing a half ounce. The weight of oneis, therefore, sixteen times greater than the other.

Suppose these two balls are thrown with theexpenditure of the same power. What will be theresult! The iron ball will go much farther, or,

if projected against a wall will strike a harderblow than the cotton ball.

MOMENTUM A FACTOR.--Each had transferredto it a motion. The initial speed was the same,and the power set up equal in the two. Why thisdifference, The answer is, that it is in thematerial itself. It was the mass or density which accountedfor the difference. It was mass multipliedby speed which gave it the power, called, inthis case, momentum.

The iron ball weighing eight ounces, multipliedby the assumed speed of 50 feet per second, equals400 units of work. The cotton ball, weighing 1/2ounce, with the same initial speed, represents 25units of work. The term "unit of work" meansa measurement, or a factor which may be used tomeasure force.

It will thus be seen that it was not the throwerwhich gave the power, but the article itself. Afeather ball thrown under the same conditions,would produce a half unit of work, and the ironball, therefore, produced 800 times more energy.

RESISTANCE.--Now, in the movement of any body

through space, it meets with an enemy at everystep, and that is air resistance. This is muchmore effective against the cotton than the ironball: or, it might be expressed in another way:The momentum, or the power, residing in themetal ball, is so much greater than that within thecotton ball that it travels farther, or strikes amore effective blow on impact with the wall.

HOW RESISTANCE AFFECTS THE SHAPE.--It is because


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of this counterforce, resistance, that shapebecomes important in a flying object. The metalball 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 differencein the air impact against the two forms.

MASS AND RESISTANCE.--Owing to the fact thatresistance acts with such a retarding force on anobject of small mass, and it is difficult to set up arapid motion in an object of great density, lightnessin flying machine structures has been considered,in the past, the principal thing necessary.

THE EARLY TENDENCY TO ELIMINATE MOMENTUM.--Builders of flying machines, for severalyears, sought to eliminate the very thingwhich gives energy to a horizontally-movablebody, namely, momentum.

Instead of momentum, something had to besubstituted. This was found in so arranging themachine that its weight, or a portion of it, wouldbe sustained in space by the very element whichseeks to retard its flight, namely, the atmosphere.

If there should be no material substance, likeair, then the only way in which a heavier-than-airmachine could ever fly, would be by propelling itthrough space, like the ball was thrown, or bysome sort of impulse or reaction mechanism onthe air-ship itself. It could get no support fromthe atmosphere.

LIGHT MACHINES UNSTABLE.--Gradually thequestion of weight is solving itself. Aviators arebeginning to realize that momentum is a wonderfulproperty, and a most important element inflying. The safest machines are those which haveweight. The light, willowy machines are subjectto every caprice of the wind. They are notoriouslyunstable in flight, and are dangerous evenin the hands of experts.

THE APPLICATION OF POWER.--The thing now toconsider is not form, or shape, or the distributionof the supporting surfaces, but HOW to apply

the power so that it will rapidly transfer a machineat rest to one in motion, and thereby getthe proper support on the atmosphere to hold itin flight.

THE SUPPORTING SURFACES.--This brings us tothe consideration of one of the first great problemsin flying machines, namely, the supportingsurfaces,--not its form, shape or arrangement,(which will be taken up in their proper places), but


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the area, the dimensions, and the angle necessaryfor flight.

AREA NOT THE ESSENTIAL THING.--The historyof flying machines, short as it is, furnishes manyexamples of one striking fact: That area hasbut little to do with sustaining an aeroplane whenonce in flight. The first Wright flyer weighed741 pounds, had about 400 square feet of planesurface, and was maintained in the air with a 12horse power engine.

True, that machine was shot into the air by acatapult. Motion having once been imparted to it,the only thing necessary for the motor was tomaintain the speed.

There are many instances to show that whenonce in flight, one horse power will sustain over100 pounds, and each square foot of supporting

surface will maintain 90 pounds in flight.

THE LAW OF GRAVITY.--As the effort to flymay be considered in the light of a struggle toavoid the laws of nature with respect to matter,it may be well to consider this great force as afitting prelude to the study of our subject.

Proper understanding, and use of terms is verydesirable, so that we must not confuse them.Thus, weight and mass are not the same. Weightvaries with the latitude, and it is different at variousaltitudes; but mass is always the same.

If projected through space, a certain masswould move so as to produce momentum, whichwould be equal at all places on the earth's surface,or at any altitude.

Gravity has been called weight, and weightgravity. The real difference is plain if gravityis considered as the attraction of mass for mass.Gravity is generally known and considered as aforce 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 proximityto each other will mutually attract each other.If one has double the mass it will have twice theattractive power. If one is doubled and the othertripled, the attraction would be increased sixtimes. But if the distance should be doubled theattraction would be reduced to one-fourth; andif the distance should be tripled then the pullwould be only one-ninth.


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The foregoing is the substance of the law,namely, that all bodies attract all other bodieswith a force directly in proportion to their mass,and inversely as the square of their distance fromone another.

To explain this we cite the following illustration:Two bodies, each having a mass of 4pounds, and one inch apart, are attracted towardeach other, so they touch. If one has twice themass of the other, the smaller will draw the largeronly one-quarter of an inch, and the large onewill draw the other three-quarters of an inch,thus confirming the law that two bodies will attracteach other in proportion to their mass.

Suppose, now, that these balls are placed twoinches apart,--that is, twice the distance. Aseach is, we shall say, four pounds in weight, thesquare 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 ofthe distance, so that at two inches there is onlyone-sixteenth the attraction as at one inch.

If the cord of one of the balls should be cut, itwould fall to the earth, for the reason that theattractive force of the great mass of the earth isso much greater than the force of attraction inits companion ball.

INDESTRUCTIBILITY OF GRAVITATION.--Gravitycannot be produced or destroyed. It acts betweenall parts of bodies equally; the force beingproportioned to their mass. It is not affected byany intervening substance; and is transmittedinstantaneously, whatever the distance may be.

While, therefore, it is impossible to divest matterof this property, there are two conditionswhich neutralize its effect. The first of these isposition. Let us take two balls, one solid andthe other hollow, but of the same mass, or density.If the cavity of the one is large enough to receivethe other, it is obvious that while gravity is stillpresent the lines of attraction being equal atall points, and radially, there can be no pull which

moves them together.

DISTANCE REDUCES GRAVITATIONAL PULL.--Orthe balls may be such distance apart that the attractiveforce ceases. At the center of the earthan object would not weigh anything. A poundof iron and an ounce of wood, one sixteen timesthe mass of the other, would be the same,--absolutelywithout weight.


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If the object should be far away in space itwould not be influenced by the earth's gravity;so it will be understood that position plays animportant part in the attraction of mass for mass.

HOW MOTION ANTAGONIZES GRAVITY.--The secondway to neutralize gravity, is by motion. Aball thrown upwardly, antagonizes the force ofgravity during the period of its ascent. In likemanner, when an object is projected horizontally,while its mass is still the same, its weight is less.

Motion is that which is constantly combatingthe action of gravity. A body moving in a circlemust be acted upon by two forces, one which tendsto draw it inwardly, and the other which seeks tothrow it outwardly.

The former is called centripetal, and the lattercentrifugal motion. Gravity, therefore, represents

centripetal, and motion centrifugal force.

If the rotative speed of the earth should be retarded,all objects on the earth would be increasedin weight, and if the motion should be acceleratedobjects would become lighter, and if sufficientspeed should be attained all matter would fly offthe surface, just as dirt dies off the rim of awheel at certain speeds.

A TANGENT.--When an object is thrown horizontallythe line of flight is tangential to the earth,or at right angles to the force of gravity. Sucha course in a flying machine finds less resistancethan if it should be projected upwardly, or directlyopposite the centripetal pull.

_Fig 1. Tangential Flight_

TANGENTIAL MOTION REPRESENTS CENTRIFUGALPULL.--A tangential motion, or a horizontalmovement, seeks to move matter away from thecenter of the earth, and any force which impartsa horizontal motion to an object exerts a centrifugalpull for that reason.

In Fig. 1, let A represent the surface of the

earth, B the starting point of the flight of an object,and C the line of flight. That represents atangential line. For the purpose of explainingthe phenomena of tangential flight, we will assumethat the missile was projected with a sufficientforce to reach the vertical point D, whichis 4000 miles from the starting point B.

In such a case it would now be over 5500 milesfrom the center of the earth, and the centrifugal


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pull would be decreased to such an extent that theball would go on and on until it came within thesphere of influence from some other celestialbody.

EQUALIZING THE TWO MOTIONS.--But now let usassume that the line of flight is like that shownat E, in Fig. 2, where it travels along parallelwith the surface of the earth. In this case theforce of the ball equals the centripetal pull,--or,to put it differently, the centrifugal equals thegravitational pull.

The constant tendency of the ball to fly off ata tangent, and the equally powerful pull ofgravity acting against each other, produce amotion which is like that of the earth, revolvingaround the sun once every three hundred andsixty-five days.

It is a curious thing that neither Langley, norany of the scientists, in treating of the matter offlight, have taken into consideration this qualityof momentum, in their calculations of the elementsof flight.

_Fig. 2 Horizontal Flight_

All have treated the subject as though thewhole problem rested on the angle at which theplanes were placed. At 45 degrees the lift anddrift are assumed to be equal.

LIFT AND DRIFT.--The terms should be explained,in view of the frequent allusion whichwill be made to the terms hereinafter. Liftis the word employed to indicate the amountwhich a plane surface will support while in flight.Drift is the term used to indicate the resistancewhich is offered to a plane moving forwardlyagainst the atmosphere.

_Fig. 3. Lift and Drift_

In Fig. 3 the plane A is assumed to be movingforwardly in the direction of the arrow B. Thisindicates the resistance. The vertical arrow C

shows the direction of lift, which is the weightheld up by the plane.

NORMAL PRESSURE.--Now there is another termmuch used which needs explanation, and that isnormal pressure. A pressure of this kindagainst a plane is where the wind strikes it atright angles. This is illustrated in Fig. 4, inwhich the plane is shown with the wind strikingit squarely.


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It is obvious that the wind will exert a greaterforce against a plane when at its normal. On theother hand, the least pressure against a plane iswhen it is in a horizontal position, because thenthe wind has no force against the surfaces, andthe only effect on the drift is that which takesplace when the wind strikes its forward edge.

_Fig. 4. Normal Air Pressure_

_Fig. 5. Edge Resistance_

HEAD RESISTANCE.--Fig. 5 shows such a plane,the only resistance being the thickness of theplane as at A. This is called head resistance,and on this subject there has been much controversy,and many theories, which will be consideredunder the proper headings.

If a plane is placed at an angle of 45 degreesthe lift and the drift are the same, assumedly, because,if we were to measure the power requiredto drive it forwardly, it would be found to equalthe weight necessary to lift it. That is, supposewe should hold a plane at that angle with a heavywind blowing against it, and attach two pairs ofscales to the plane, both would show the samepull.

_Fig. 6. Measuring Lift and Drift_

MEASURING LIFT AND DRIFT.--In Fig. 6, A is theplane, B the horizontal line which attaches theplane to a scale C, and D the line attaching it tothe scale E. When the wind is of sufficient forceto hold up the plane, the scales will show the samepull, neglecting, of course, the weight of theplane itself.

PRESSURE AT DIFFERENT ANGLES.--What everyone wants to know, and a subject on which agreat deal of experiment and time have been expended,is to determine what the pressures are atthe different angles between the horizontal, andlaws have been formulated which enable the pressures

to be calculated.

DIFFERENCE BETWEEN LIFT AND DRIFT IN MOTION.--Thefirst observation is directed to the differencesthat exist between the lift and drift,when the plane is placed at an angle of less than45 degrees. A machine weighing 1000 poundshas always the same lift. Its mass does notchange. Remember, now, we allude to its mass,or density.


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We are not now referring to weight, becausethat must be taken into consideration, in theproblem. As heretofore stated, when an objectmoves horizontally, it has less weight than whenat rest. If it had the same weight it would notmove forwardly, but come to rest.

When in motion, therefore, while the lift, sofar as its mass is concerned, does not change, thedrift does decrease, or the forward pull is lessthan when at 45 degrees, and the decrease is lessand less until the plane assumes a horizontal position,where it is absolutely nil, if we do not considerhead resistance.

TABLES OF LIFT AND DRIFT.--All tables of Liftand Drift consider only the air pressures. Theydo not take into account the fact that momentumtakes an important part in the translation of an

object, like a flying machine.

A mass of material, weighing 1000 pounds whileat rest, sets up an enormous energy when movingthrough the air at fifty, seventy-five, or one hundredmiles an hour. At the latter speed the movementis about 160 feet per second, a motion whichis nearly sufficient to maintain it in horizontalflight, independently of any plane surface.

Such being the case, why take into account onlythe angle of the plane? It is no wonder thataviators have not been able to make the theoreticalconsiderations and the practical demonstrationsagree.

WHY TABLES OF LIFT AND DRIFT ARE WRONG.--A little reflection will show why such tables arewrong. They were prepared by using a planesurface at rest, and forcing a blast of air againstthe plane placed at different angles; and for determiningair pressures, this is, no doubt, correct.But it does not represent actual flying conditions.It does not show the conditions existingin an aeroplane while in flight.

To determine this, short of actual experiments

with a machine in horizontal translation, is impossible,unless it is done by taking into accountthe factor due to momentum and the elementattributable to the lift of the plane itself due to itsimpact against the atmosphere.

LANGLEY'S LAW.--The law enunciated byLangley is, that the greater the speed the less thepower required to propel it. Water as a propellingmedium has over seven hundred times


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more force than air. A vessel having, for instance,twenty horse power, and a speed of tenmiles per hour, would require four times thatpower to drive it through the water at double thespeed. The power is as the square of the speed.

With air the conditions are entirely different.The boat submergence in the water is practicallythe same, whether going ten or twenty miles anhour. The head resistance is the same, substantially,at all times in the case of the boat; with theflying machine the resistance of its sustainingsurfaces decreases.

Without going into a too technical descriptionof the reasoning which led to the discovery of thelaw of air pressures, let us try and understandit by examining the diagram, Fig. 7.

A represents a plane at an angle of 45 degrees,

moving forwardly into the atmosphere in thedirection of the arrows B. The measurementacross the plane vertically, along the line B,which is called the sine of the angle, representsthe surface impact of air against the plane.

In Fig. 8 the plane is at an angle of 27 degrees,which makes the distance in height across the lineC just one-half the length of the line B of Fig. 7,hence the surface impact of the air is one-half thatof Fig. 7, and the drift is correspondingly decreased.

_Fig. 7. Equal Lift and Drift in Flight._

_Fig. 8. Unequal Lift and Drift._

MOVING PLANES VS. WINDS.--In this way Boisset,Duchemin, Langley, and others, determinedthe comparative drift, and those results have beenlargely relied upon by aviators, and assumed tobe correct when applied to flying machines.

That they are not correct has been proven bythe Wrights and others, the only explanation beingthat some errors had been made in the calculations,or that aviators were liable to commit errors

in observing the true angle of the planeswhile in flight.

MOMENTUM NOT CONSIDERED.--The great factorof momentum has been entirely ignored, and it isour desire to press the important point on thosewho begin to study the question of flying machines.

THE FLIGHT OF BIRDS.--Volumes have beenwritten concerning observations on the flight of


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birds. The marvel has been why do soaring birdsmaintain themselves in space without flappingtheir wings. In fact, it is a much more remarkablething to contemplate why birds which dependon flapping wings can fly.

THE DOWNWARD BEAT.--It is argued that thedownward beat of the wings is so much morerapid than the upward motion, that it gets an actionon the air so as to force the body upwardly.This is disposed of by the wing motion of manybirds, notoriously the crow, whose lazily-flappingwings can be readily followed by the eye, and thedifference in movement, if any, is not perceptible.

THE CONCAVED WING.--It is also urged that theconcave on the under side of the wing gives thequality of lift. Certain kinds of beetles, and particularlythe common house fly, disprove that theory,as their wings are perfectly flat.

FEATHER STRUCTURE CONSIDERED.--Then thefeather argument is advanced, which seeks toshow that as each wing is made up of a pluralityof feathers, overlapping each other, they form asort of a valved surface, opening so as to permitair to pass through them during the period oftheir upward movement, and closing up as thewing descends.

It is difficult to perform this experiment withwings, so as to show such an individual feathermovement. It is certain that there is nothing inthe structure of the wing bone and the featherconnection which points to any individual feathermovement, and our observation is, that eachfeather is entirely too rigid to permit of such anopening up between them.

It is obvious that the wing is built up in thatway for an entirely different reason. Soaringbirds, which do not depend on the flapping motion,have the same overlapping feather formation.

WEBBED WINGS.--Furthermore, there are numerousflying creatures which do not havefeathered wings, but web-like structures, or like the

house fly, in one continuous and unbrokenplane.

That birds which fly with flapping wings derivetheir support from the air, is undoubtedly true,and that the lift produced is due, not to the form,or shape, or area of the wing, is also beyond question.The records show that every conceivabletype of outlined structure is used by nature; thematerial and texture of the wings themselves differ


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to such a degree that there is absolutely nosimilarity; some have concaved under surfaces,and others have not; some fly with rapidly beatingwings, and others with slow and measuredmovements; many of them fly with equal facilitywithout flapping movements; and the proportionsof weight to wing surface vary to such an extentthat it is utterly impossible to use such data as aguide in calculating what the proper surfaceshould be for a correct flying machine.

THE ANGLE OF MOVEMENT.--How, then, it maybe asked, do they get their support? There mustbe something, in all this variety and diversity ofform, of motion, and of characteristics, whichsupplies the true answer. The answer lies in theangle of movement of every wing motion, whichis at the control of the bird, and if this is examinedit will be found that it supplies the correctanswer to every type of wing which nature has

made.

AN INITIAL IMPULSE OR MOVEMENT NECESSARY.--Let A, Fig. 9, represent the section of a bird'swing. All birds, whether of the soaring or theflapping kind, must have an initial forward movementin order to attain flight. This impulse isacquired either by running along the ground, orby a leap, or in dropping from a perch. Soaringbirds cannot, by any possibility, begin flight,unless there is such a movement to change from aposition of rest to one of motion.

_Fig. 9. Wing Movement in Flight._

In the diagram, therefore, the bird, in movingforwardly, while raising the wing upwardly, depressesthe rear edge of the wing, as in position1, and when the wing beats downwardly the rearmargin is raised, in relation to its front margin,as shown in position 2.

A WEDGING MOTION.--Thus the bird, by awedge-like motion, gives a forwardly-propellingaction, and as the rear margin has more or lessflexure, its action against the air is less during itsupward beat, and this also adds to the upward lift

of the body of the bird.

NO MYSTERY IN THE WAVE MOTION.--There isno mystery in the effect of such a wave-like motion,and it must be obvious that the hummingbird, and like flyers, which poise at one spot, areable to do so because, instead of moving forwardly,or changing the position of its body horizontally,in performing the undulatory motion ofthe wing, it causes the body to rock, so that at the


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point where the wing joins the body, an ellipticalmotion is produced.

_Fig. 10. Evolution of Humming-Bird's Wing._

HOW BIRDS POISE WITH FLAPPING WINGS.--Thisis shown in Fig. 10, in which eight successive positionsof the wing are shown, and wherein fourof the position, namely, 1, 2, 3, and 4, representthe downward movement, and 6, 7, 8, and 9, theupward beat.

All the wing angles are such that whether thesuspension point of each wing is moving downwardly,or upwardly, a support is found in somepart of the wing.

NARROW-WINGED BIRDS.--Birds with rapid flappingmotions have comparatively narrow wings,

fore and aft. Those which flap slowly, and arenot swift flyers, have correspondingly broaderwings. The broad wing is also typical of thesoaring birds.

But how do the latter overcome gravitationwithout exercising some sort of wing movement?

INITIAL MOVEMENT OF SOARING BIRDS.--Acuteobservations show that during the early stagesof flight, before speed is acquired, they dependon the undulating movement of the wings, andsome of them acquire the initial motion by flapping.When speed is finally attained it is difficultfor the eye to note the motion of the wings.

SOARING BIRDS MOVE SWIFTLY.--Now, the firstobservation is, that soaring birds are swiftly-moving creatures. As they sail overheadmajestically they seem to be moving slowly. Butdistance is deceptive. The soaring bird travelsat great speeds, and this in itself should be sufficientto enable us to cease wondering, when it isremembered that swift translation decreasesweight, so that this factor does not, under thoseconditions, operate against flight.

MUSCULAR ENERGY EXERTED BY SOARING BIRDS.--It is not conceivable that the mere will of thebird would impel it forwardly, without it exertedsome muscular energy to keep up its speed. Thedistance at which the bird performs this wonderfulevolution is at such heights from the observerthat the eye cannot detect a movement.

WINGS NOT MOTIONLESS.--While the wings appearto be absolutely motionless, it is more reasonable


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to assume that a slight sinuous movement,or a rocking motion is constantly kept up, whichwedges forwardly with sufficient speed to compelmomentum to maintain it in flight. To do so requiresbut a small amount of energy. The headresistance of the bird formation is reduced to aminimum, and at such high speeds the angle ofincidence of the wings is very small, requiring butlittle aid to maintain it in horizontal flight.

CHAPTER II

PRINCIPLES OF AEROPLANE FLIGHT

FROM the foregoing chapter, while it may berightly inferred that power is the true secret ofaeroplane flight, it is desirable to point out certain

other things which must be considered.

SPEED AS ONE OF THE ELEMENTS--Every boy,probably, has at some time or other thrown smallflat stones, called "skippers." He has noticedthat if they are particularly thin, and large indiameter, that there is a peculiar sailing motion,and that they move through the air in an undulatingor wave-like path.

Two things contribute to this motion; one is thesize of the skipper, relative to its weight, and theother is its speed. If the speed is slow it willquickly wend its way to the earth in a gradualcurve. This curved line is called its trajectory.If it is not very large diametrically, in proportionto its weight, it will also make a gradual curve indescending, without "skimming" up and downin its flight.

SHAPE AND SPEED.--It has been observed, also,that a round ball, or an object not flattened out,will make a regular curved path, whatever thespeed may be.

It may be assumed, therefore, that the shapealone does not account for this sinuous motion;

but that speed is the element which accounts forit. Such being the case it may be well to inquireinto the peculiar action which causes a skipperto dart up and down, and why the path thusformed grows more and more accentuated as thespeed increases.

As will be more fully described in a later chapter,the impact of air against a moving body doesnot increase in proportion to its speed, but in the


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ratio of the square of the speed.

WHAT SQUARE OF THE SPEED MEANS.--In mathematicsa figure is squared when it is multipliedby itself. Thus, 4 X 4= 16; 5 X 5 = 25; and soon, so that 16 is the square of 4, and 25 the squareof 5. It has been found that a wind moving at thespeed of 20 miles an hour has a striking or pushingforce of 2 pounds on every square foot of surface.

If the wind travels twice as fast, or 40 milesan hour, the pushing force is not 4 pounds, but8 pounds. If the speed is 60 miles an hour thepushing force increases to 18 pounds.

ACTION OF A SKIPPER.--When the skipper leavesthe hands of the thrower it goes through the airin such a way that its fiat surface is absolutelyon a line with the direction in which it is projected.

At first it moves through the air solely by forceof the power which impels it, and does not in anyway depend on the air to hold it up. See Fig.1, in which A represents the line of projection,and B the disk in its flight.

_Fig. 11. A Skipper in Flight._

After it has traveled a certain distance, andthe force decreases, it begins to descend, thus describingthe line C, Fig. 1, the disk B, in this casedescending, without changing its position, whichmight be described by saying that it merely settlesdown to the earth without changing its plane.

The skipper still remains horizontal, so that asit moves toward the earth its flat surface, whichis now exposed to the action of the air, meetswith a resistance, and this changes the angle ofthe disk, so that it will not be horizontal. Insteadit assumes the position as indicated at D,and this impinging effect against the air causesthe skipper to move upwardly along the line E,and having reached a certain limit, as at, say E,it automatically again changes its angle and movesdownwardly along the path F, and thus continuesto undulate, more or less, dependent on the combined

action of the power and weight, or momentum,until it reaches the earth.

It is, therefore, clear that the atmosphere hasan action on a plane surface, and that the extentof the action, to sustain it in flight, depends on twothings, surface and speed.

Furthermore, the greater the speed the less thenecessity for surface, and that for gliding purposes


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speed may be sacrificed, in a large measure,where there is a large surface.

This very action of the skipper is utilized bythe aviator in volplaning,--that is, where thepower of the engine is cut off, either by accident,or designedly, and the machine descends to theearth, whether in a long straight glide, or in agreat circle.

As the machine nears the earth it is caused tochange the angle of flight by the control mechanismso that it will dart upwardly at an angle, or downwardly,and thus enable the pilot to sail to anotherpoint beyond where he may safely land.This changing the course of the machine so thatit will glide upwardly, means that the incidenceof the planes has been changed to a positiveangle.

ANGLE OF INCIDENCE.--In aviation this is a termgiven to the position of a plane, relative to theair against which it impinges. If, for instance,an aeroplane is moving through the air with thefront margin of the planes higher than their rearmargins, it is said to have the planes at a positiveangle of incidence. If the rear margins arehigher than the front, then the planes have a negativeangle of incidence.

The word incidence really means, a fallingupon, or against; and it will be seen, therefore,that the angle of incidence means the tilt of theplanes in relation to the air which strikes it.

Having in view, therefore, that the two qualities,namely, speed and surface, bear an intimaterelation with each other, it may be understoodwherein mechanical flight is supposed to be analogousto bird flight.

SPEED AND SURFACE.--Birds which poise in theair, like the humming bird, do so because theybeat their wings with great rapidity. Thosewhich soar, as stated, can do so only by movingthrough the atmosphere rapidly, or by having alarge wing spread relative to the weight. It will

thus be seen that speed and surface become thecontrolling factors in flight, and that while thelatter may be entirely eliminated from the problem,speed is absolutely necessary under any andall conditions.

By speed in this connection is not meant highvelocity, but that a movement, produced by powerexpressed in some form, is the sole and most necessaryrequisite to movement through the air with


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all heavier-than-air machines.

If sufficient power can be applied to an aeroplane,surface is of no consequence; shape neednot be considered, and any sort of contrivancewill move through the air horizontally.

CONTROL OF THE DIRECTION OF FLIGHT.--But thecontrol of such a body, when propelled throughspace by force alone, is a different matter. Tochange the machine from a straight path to acurved one, means that it must be acted upon bysome external force.

We have explained that power is somethingwhich is inherent in the thing itself. Now, in orderthat there may be a change imparted to amoving mass, advantage must be taken of the mediumthrough which it moves,--the atmosphere.

VERTICAL CONTROL PLANES.--If vertically-arrangedplanes are provided, either fore or aft ofthe machine, or at both ends, the angles of incidencemay be such as to cause the machine toturn from its straight course.

In practice, therefore, since it is difficult to supplysufficient power to a machine to keep it in motionhorizontally, at all times, aeroplanes are providedwith supporting surfaces, and this aid inholding it up grows less and less as its speed increases.

But, however strong the power, or great thespeed, its control from side to side is not dependenton the power of the engine, or the speedat which it travels through the air.

Here the size of the vertical planes, and theirangles, are the only factors to be considered, andthese questions will be considered in their properplaces.

CHAPTER III

THE FORM OR SHAPE OF FLYING MACHINES

EVERY investigator, experimenter, and scientist,who has given the subject of flight study, proceedson the theory that in order to fly man mustcopy nature, and make the machine similar to thetype so provided.

THE THEORY OF COPYING NATURE.--If such is the


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case then it is pertinent to inquire which bird isthe proper example to use for mechanical flight.We have shown that they differ so radically inevery essential, that what would be correct in onething would be entirely wrong in another.

The bi-plane is certainly not a true copy. Theonly thing in the Wright machine which in anyway resembles the bird's wing, is the rounded endof the planes, and judging from other machines,which have square ends, this slight similarity doesnot contribute to its stability or otherwise helpthe structure.

The monoplane, which is much nearer the birdtype, has also sounded wing ends, made not somuch for the purpose of imitating the wing of thebird, as for structural reasons.

HULLS OF VESSELS.--If some marine architect

should come forward and assert that he intendedto follow nature by making a boat with a hull ofthe shape or outline of a duck, or other swimmingfowl, he would be laughed at, and justly so, becausethe lines of vessels which are most efficientare not made like those of a duck or other swimmingcreatures.

MAN DOES NOT COPY NATURE.--Look about you,and see how many mechanical devices follow theforms laid down by nature, or in what respectman uses the types which nature provides in devisingthe many inventions which ingenuity hasbrought forth.

PRINCIPLES ESSENTIAL, NOT FORMS.--It is essentialthat man shall follow nature's laws. He cannotevade the principles on which the operationsof mechanism depend; but in doing so he has, innearly every instance, departed from the formwhich nature has suggested, and made the machineirrespective of nature's type.

Let us consider some of these striking differencesto illustrate this fact. Originally pins werestuck upon a paper web by hand, and placed inrows, equidistant from each other. This necessitates

the cooperative function of the fingers andthe eye. An expert pin sticker could thus assemblefrom four to five thousand pins a day.

The first mechanical pinsticker placed over500,000 pins a day on the web, rejecting every bentor headless pin, and did the work with greateraccuracy than it was possible to do it by hand.There was not the suggestion of an eye, or a fingerin the entire machine, to show that nature furnished


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the type.

NATURE NOT THE GUIDE AS TO FORMS.--Naturedoes not furnish a wheel in any of its mechanicalexpressions. If man followed nature's formin the building of the locomotive, it would movealong on four legs like an elephant. Curiouslyenough, one of the first road wagons had "pushlegs,"--an instance where the mechanic tried tocopy nature,--and failed.

THE PROPELLER TYPE.--The well known propelleris a type of wheel which has no prototype innature. It is maintained that the tail of a fishin its movement suggested the propeller, but thelatter is a long departure from it.

The Venetian rower, who stands at the stern,and with a long-bladed oar, fulcrumed to theboat's extremity, in making his graceful lateral

oscillations, simulates the propelling motion ofthe tail in an absolutely perfect manner, but it isnot a propeller, by any means comparable to thekind mounted on a shaft, and revoluble.

How much more efficient are the spirally-formedblades of the propeller than any wing or fin movement,in air or sea. There is no comparison betweenthe two forms in utility or value.

Again, the connecting points of the arms andlegs with the trunk of a human body afford themost perfect types of universal joints which naturehas produced. The man-made universaljoint has a wider range of movement, possessesgreater strength, and is more perfect mechanically.A universal joint is a piece of mechanismbetween two elements, which enables them to beturned, or moved, at any angle relative to eachother.

But why multiply these instances. Like sampleswill be found on every hand, and in all directions,and man, the greatest of all of nature'sproducts, while imperfect in himself, is improvingand adapting the things he sees about him.

WHY SPECIALLY-DESIGNED FORMS IMPROVE NATURALSTRUCTURES.--The reason for this is, primarily,that the inventor must design the articlefor its special work, and in doing so makes it betteradapted to do that particular thing. Thehands and fingers can do a multiplicity of things,but it cannot do any particular work with the facilityor the degree of perfection that is possiblewith the machine made for that purpose.


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The hands and fingers will bind a sheaf ofwheat, but it cannot compete with the special machinemade for that purpose. On the other handthe binder has no capacity to do anything else thanwhat it was specially made for.

In applying the same sort of reasoning to thebuilding of flying machines we must be led to theconclusion that the inventor can, and will, eventually,bring out a form which is as far superior tothe form which nature has taught us to use asthe wonderful machines we see all about us aresuperior to carry out the special work they weredesigned to do.

On land, man has shown this superiority overmatter, and so on the sea. Singularly, the submarines,which go beneath the sea, are very farfrom that perfected state which have been attainedby vessels sailing on the surface; and while

the means of transportation on land are arrivingat points where the developments are swift andremarkable, the space above the earth has not yetbeen conquered, but is going through that sameperiod of development which precedes the productionof the true form itself.

MECHANISM DEVOID OF INTELLIGENCE.--The greaterror, however, in seeking to copy nature's formin a flying machine is, that we cannot invest themechanism with that which the bird has, namely,a guiding intelligence to direct it instinctively, asthe flying creature does.

A MACHINE MUST HAVE A SUBSTITUTE FOR INTELLIGENCE.--Such being the case it must be endowedwith something which is a substitute. Abird is a supple, pliant organism; a machine is arigid structure. One is capable of being directedby a mind which is a part of the thing itself; whilethe other must depend on an intelligence which isseparate from it, and not responsive in feeling ormovement.

For the foregoing reasons success can neverbe attained until some structural form is devisedwhich will consider the flying machine independently

of the prototypes pointed out as the correctthings to follow. It does not, necessarily, have tobe unlike the bird form, but we do know that thepresent structures have been made and insistedupon blindly, because of this wrong insistence onforms.

STUDY OF BIRD FLIGHT USELESS.--The study ofthe flight of birds has never been of any specialvalue to the art. Volumes have been written on


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the subject. The Seventh Duke of Argyle, andlater, Pettigrew, an Englishman, contributed avast amount of written matter on the subject ofbird flight, in which it was sought to show thatsoaring birds did not exert any power in flying.

Writers and experimenters do not agree on thequestion of the propulsive power, or on the formor shape of the wing which is most effective, orin the matter of the relation of surface to weight,nor do they agree in any particular as to the effectand action of matter in the soaring principle.

Only a small percentage of flying creatures usemotionless wings as in soaring. By far, thegreater majority use beating wings, a method oftranslation in air which has not met with successin any attempts on the part of the inventor.

Nevertheless, experimenting has proceeded on

lines which seek to recognize nature's form only,while avoiding the best known and most persistenttype.

SHAPE OF SUPPORTING SURFACES.--When we examinethe prevailing type of supporting surfaceswe cannot fail to be impressed with one feature,namely, the determination to insist on a broadspread of plane surface, in imitation of the birdwith outstretched wings.

THE TROUBLE ARISING FROM OUTSTRETCHEDWINGS.--This form of construction is what bringsall the troubles in its train. The literature onaviation is full of arguments on this subject, alldeclaring that a wide spread is essential, because,--birds fly that way.

These assertions are made notwithstanding thefact that only a few years ago, in the great exhibitof aeroplanes in Paris, many unique forms of machineswere shown, all of them capable of flying,as proven by numerous experiments, and amongthem were a half dozen types whose length foreand aft were much greater than transversely, andit was particularly noted that they had most wonderfulstability.

DENSITY OF THE ATMOSPHERE.--Experts declarethat the density of the atmosphere varies throughout,--that it has spots here and there which are,apparently, like holes, so that one side or theother of the machine will, unaccountably, tilt, andsometimes the entire machine will suddenly dropfor many feet, while in flight.

ELASTICITY OF THE AIR.--Air is the most elastic


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substance known. The particles constituting itare constantly in motion. When heat or cold penetratethe mass it does so, in a general way, so asto permeate the entire body, but the conductivityof the atmospheric gases is such that the heatdoes not reach all parts at the same time.

AIR HOLES.--The result is that varying strataof heat and cold seem to be superposed, and alsodistributed along the route taken by a machine,causing air currents which vary in direction andintensity. When, therefore, a rapidly-movingmachine passes through an atmosphere so disturbed,the surfaces of the planes strike a mass ofair moving, we may say, first toward the plane,and the next instant the current is reversed, andthe machine drops, because its support is temporarilygone, and the aviator experiences the sensationof going into a "hole."

RESPONSIBILITY FOR ACCIDENTS.--These so-called"holes" are responsible for many accidents. Theoutstretched wings, many of them over forty feetfrom tip to tip, offer opportunities for a tilt at oneend or the other, which has sent so many machinesto destruction.

The high center of gravity in all machines makesthe weight useless to counterbalance the risingend or to hold up the depressed wing.

All aviators agree that these unequal areas ofdensity extend over small spaces, and it is, therefore,obvious that a machine which is of such astructure that it moves through the air broadsideon, will be more liable to meet these inequalitiesthan one which is narrow and does not take in sucha wide path.

Why, therefore, persist in making a form which,by its very nature, invites danger? Because birdsfly that way!

THE TURNING MOVEMENT.--This structural arrangementaccentuates the difficulty when the machineturns. The air pressure against the wingsurface is dependent on the speed. The broad

outstretched surfaces compel the wing at the outerside of the circle to travel faster than the innerone. As a result, the outer end of the aeroplaneis elevated.

CENTRIFUGAL ACTION.--At the same time therunning gear, and the frame which carries it andsupports the machine while at rest, being belowthe planes, a centrifugal force is exerted, whenturning a circle, which tends to swing the wheels


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direction of flight. The former has reference tothe up and down movement of an aeroplane,whereas the latter is used to designate a turningmovement to the right or to the left.

WHY SHOULD THE ANGLE OF THE BODY CHANGE?--The first question that presents itself is, whyshould the angle of the aeroplane body change?Why should it be made to dart up and down andproduce a sinuous motion? Why should its nosetilt toward the earth, when it is descending, andraise the forward part of the structure while ascending?

The ready answer on the part of the bird-formadvocate is, that nature has so designed a flyingstructure. The argument is not consistent, becausein this respect, as in every other, it is notmade to conform to the structure which they seekto copy.

CHANGING ANGLE OF BODY NOT SAFE.--Furthermore,there is not a single argument which can beadvanced in behalf of that method of building,which proves it to be correct. Contrariwise, ananalysis of the flying movement will show that it isthe one feature which has militated against safety,and that machines will never be safe so long asthe angle of the body must be depended upon tocontrol the angle of flying.

_Fig. 11a Monoplane in Flight._

In Fig. 11a three positions of a monoplane areshown, each in horizontal flight. Let us say thatthe first figure A is going at 40 miles per hour,the second, B, at 50, and the third, C, at 60 miles.The body in A is nearly horizontal, the angle ofthe plane D being such that, with the tail E alsohorizontal, an even flight is maintained.

When the speed increases to 50 miles an hour,the angle of incidence in the plane D must bedecreased, so that the rear end of the frame mustbe raised, which is done by giving the tail an angleof incidence, otherwise, as the upper side of thetail should meet the air it would drive the rearend of the frame down, and thus defeat the attempt

to elevate that part.

_Fig. 12. Angles of Flight._

As the speed increases ten miles more, the tailis swung down still further and the rear end ofthe frame is now actually above the plane of flight.In order, now, to change the angle of flight, withoutaltering the speed of the machine, the tail isused to effect the control.


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Examine the first diagram in Fig. 12. Thisshows the tail E still further depressed, and theair striking its lower side, causes an upward movementof the frame at that end, which so much decreasesthe angle of incidence that the aeroplanedarts downwardly.

In order to ascend, the tail, as shown in the seconddiagram, is elevated so as to depress the rearend, and now the sustaining surface shoots upwardly.

Suppose that in either of the positions 1 or 2,thus described, the aviator should lose control ofthe mechanism, or it should become deranged or"stick," conditions which have existed in the historyof the art, what is there to prevent an accident?

In the first case, if there is room, the machinewill loop the loop, and in the second case the machine

will move upwardly until it is vertical, andthen, in all probability, as its propelling power isnot sufficient to hold it in that position, like ahelicopter, and having absolutely no wing supportingsurface when in that position, it will dartdown tail foremost.

A NON-CHANGING BODY.--We may contrast theforegoing instances of flight with a machine havingthe sustaining planes hinged to the body insuch a manner as to make the disposition of itsangles synchronous with the tail. In other words,see how a machine acts that has the angle of flightcontrollable by both planes,--that is, the sustainingplanes, as well as the tail.

_Fig. 13. Planes on Non-changing Body._

In Fig. 13 let the body of the aeroplane be horizontal,and the sustaining planes B disposed atthe same angle, which we will assume to be 15degrees, this being the imaginary angle for illustrativepurposes, with the power of the machineto drive it along horizontally, as shown in position1.

In position 2 the angles of both planes are now

at 10 degrees, and the speed 60 miles an hour,which still drives the machine forward horizontally.

In position 3 the angle is still less, being nowonly 5 degrees but the speed is increased to 80miles per hour, but in each instance the body ofthe machine is horizontal.

Now it is obvious that in order to ascend, ineither case, the changing of the planes to a greater


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angle would raise the machine, but at the sametime keep the body on an even keel.

_Fig. 14. Descent with Non-changing Body._

DESCENDING POSITIONS BY POWER CONTROL.--InFig. 14 the planes are the same angles in the threepositions respectively, as in Fig. 13, but now thepower has been reduced, and the speeds are 30,25, and 20 miles per hour, in positions A, B and C.

Suppose that in either position the power shouldcease, and the control broken, so that it would beimpossible to move the planes. When the machinebegins to lose its momentum it will descend on acurve shown, for instance, in Fig. 15, where position1 of Fig. 14 is taken as the speed and anglesof the plane when the power ceased.

_Fig. 15. Utilizing Momentum._

CUTTING OFF THE POWER.--This curve, A, mayreach that point where momentum has ceased asa forwardly-propelling factor, and the machinenow begins to travel rearwardly. (Fig. 16.) Ithas still the entire supporting surfaces of theplanes. It cannot loop-the-loop, as in the instancewhere the planes are fixed immovably to the body.

Carefully study the foregoing arrangement, andit will be seen that it is more nearly in accord withthe true flying principle as given by nature thanthe vaunted theories and practices now indulgedin and so persistently adhered to.

The body of a flying machine should not be oscillatedlike a lever. The support of the aeroplaneshould never be taken from it. While it may beimpossible to prevent a machine from comingdown, it can be prevented from overturning, andthis can be done without in the least detractingfrom it structurally.

_Fig. 16. Reversing Motion._

The plan suggested has one great fault, however.It will be impossible with such a structure

to cause it to fly upside down. It does not presentany means whereby dare-devil stunts can be performedto edify the grandstand. In this respectit is not in the same class with the present types.

THE STARTING MOVEMENT.--Examine this planfrom the position of starting, and see the advantagesit possesses. In these illustrations wehave used, for convenience only, the monoplanetype, and it is obvious that the same remarks apply


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to the bi-plane.

Fig. 17 shows the starting position of the stockmonoplane, in position 1, while it is being initiallyrun over the ground, preparatory to launching.Position 2 represents the negative angle at whichthe tail is thrown, which movement depresses therear end of the frame and thus gives the supportingplanes the proper angle to raise the machine,through a positive angle of incidence, of the plane.

_Fig. 17. Showing changing angle of body._

THE SUGGESTED TYPE.--In Fig. 18 the suggestedtype is shown with the body normally in a horizontalposition, and the planes in a neutral position,as represented in position 1. When sufficientspeed had been attained both planes areturned to the same angle, as in position 2, andflight is initiated without the abnormal oscillating

motion of the body.

But now let us see what takes place the momentthe present type is launched. If, by any error onthe part of the aviator, he should fail to readjustthe tail to a neutral or to a proper angle of incidence,after leaving the ground, the machine wouldtry to perform an over-head loop.

The suggested plan does not require this caution.The machine may rise too rapidly, or itsplanes may be at too great an angle for the poweror the speed, or the planes may be at too small anangle, but in either case, neglect would not turnthe machine to a dangerous position.

These suggestions are offered to the novice, becausethey go to the very foundation of a correctunderstanding of the principles involved in thebuilding and in the manipulation of flying machinesand while they are counter to the beliefs ofaviators, as is shown by the persistency in adheringto the old methods, are believed to be mechanicallycorrect, and worthy of consideration.

THE LOW CENTER OF GRAVITY.--But we have stillto examine another feature which shows the wrong

principle in the fixed planes. The question isoften asked, why do the builders of aeroplanesplace most of the weight up close to the planes?It must be obvious to the novice that the lowerthe weight the less liability of overturning.

FORE AND AFT OSCILLATIONS.--The answer is,that when the weight is placed below the planes itacts like a pendulum. When the machine is travelingforward, and the propeller ceases its motion,


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as it usually does instantaneously, the weight, beingbelow, and having a certain momentum, continuesto move on, and the plane surface meetingthe resistance just the same, and having no meansto push it forward, a greater angle of resistance isformed.

In Fig. 19 this action of the two forces is illustrated. Theplane at the speed of 30 miles is atan angle of 15 degrees, the body B of the machinebeing horizontal, and the weight C suspended directlybelow the supporting surfaces.

The moment the power ceases the weight continuesmoving forwardly, and it swings the forwardend of the frame upwardly, Fig. 20, and we nowhave, as in the second figure, a new angle of incidence,which is 30 degrees, instead of 12. It willbe understood that in order to effect a change inthe position of the machine, the forward end ascends,

as shown by the dotted line A.

_Fig. 20. Action when Propeller ceases to pull._

The weight a having now ascended as far aspossible forward in its swing, and its motionchecked by the banking action of the plan it willagain swing back, and again carry with it theframe, thus setting up an oscillation, which is extremelydangerous.

The tail E, with its unchanged angle, does not,in any degree, aid in maintaining the frame onan even keel. Being nearly horizontal while inflight, if not at a negative angle, it actually assiststhe forward end of the frame to ascend.

APPLICATION OF THE NEW PRINCIPLE.--Extendingthe application of the suggested form, let us seewherein it will prevent this pendulous motion atthe moment the power ceases to exert a forwardly-propelling force.

_Fig. 21. Synchronously moving Planes._

In Fig. 21 the body A is shown to be equippedwith the supporting plane B and the tail a, so

they are adjustable simultaneously at the sameangle, and the weight D is placed below, similar tothe other structure.

At every moment during the forward movementof this type of structure, the rear end ofthe machine has a tendency to move upwardly,the same as the forward end, hence, when theweight seeks, in this case to go on, it acts on therear plane, or tail, and causes that end to raise,


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and thus by mutual action, prevents any pendulousswing.

LOW WEIGHT NOT NECESSARY WITH SYNCHRONOUSLY-MOVING WINGS.--A little reflection will convinceany one that if the two wings move in harmony,the weight does not have to be placed low,and thus still further aid in making a compactmachine. By increasing the area of the tail, andmaking that a true supporting surface, instead ofa mere idler, the weight can be moved furtherback, the distance transversely across the planesmay be shortened, and in that way still furtherincrease the lateral stability.

CHAPTER V

DIFFERENT MACHINE TYPES AND THEIR CHARACTERISTICS

THERE are three distinct types of heavier-than-air machines, which are widely separated in alltheir characteristics, so that there is scarcely asingle feature in common.

Two of them, the aeroplane, and the orthopter,have prototypes in nature, and are distinguishedby their respective similarities to the soaringbirds, and those with flapping wings.

The Helicopter, on the other hand, has no antecedenttype, but is dependent for its raisingpowers on the pull of a propeller, or a pluralityof them, constructed, as will be pointed out hereinafter.

AEROPLANES.--The only form which has metwith any success is the aeroplane, which, inpractice, is made in two distinct forms, one witha single set of supporting planes, in imitation ofbirds, and called a monoplane; and the other havingtwo wings, one above the other, and calledthe bi-plane, or two-planes.

All machines now on the market which do notdepend on wing oscillations come under those

types.

THE MONOPLANE.--The single plane type hassome strong claims for support. First of theseis the comparatively small head resistance, dueto the entire absence of vertical supporting posts,which latter are necessary with the biplane type.The bracing supports which hold the outer endsof the planes are composed of wires, which offerbut little resistance, comparatively, in flight.


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ITS ADVANTAGES.--Then the vertical height ofthe machine is much less than in the biplane. Asa result the weight, which is farther below thesupporting surface than in the biplane, aids inmaintaining the lateral stability, particularlysince the supporting frame is higher.

Usually, for the same wing spread, the monoplaneis narrower, laterally, which is a furtheraid to prevent tilting.

ITS DISADVANTAGES.--But it also has disadvantageswhich must be apparent from its structure.As all the supporting surface is concentratedin half the number of planes, they mustbe made of greater width fore and aft, and this,as we shall see, later on, proves to be a disadvantage.

It is also doubted whether the monoplane can

be made as strong structurally as the other form,owing to the lack of the truss formation which isthe strong point with the superposed frame. Atruss is a form of construction where braces canbe used from one member to the next, so as tobrace and stiffen the whole.

THE BIPLANE.--Nature does not furnish a typeof creature which has superposed wings. In thisparticular the inventor surely did not follow nature.The reasons which led man to employ thistype may be summarized as follows:

In experimenting with planes it is found thata broad fore and aft surface will not lift as muchas a narrow plane. This subject is ful

aeroplanes by james slough zerbe

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