aeroplanes- 第2部分

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　i