aeroplanes-第12章

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_Fig。　48。　Action　of　Wind　forces　on　Kite。_



As　its　angle　is　fixed　by　means　of　the　loop　C；

it　cannot　change　its　angle　with　reference　to　the

cord；　or　independently　of　it；　and　its　only　course

is　to　move　up　higher　and　assume　the　position

shown　by　the　figure　at　D；　and　the　angle　of　incidence

of　the　kite　is　therefore　changed　to　15　degrees；

or　even　to　10　degrees。



In　the　case　of　the　aeroplane　the　effect　is　similar

from　the　standpoint　of　power　and　disposition

of　the　planes。　If　it　has　sufficient　power；　and　the

angle　of　the　planes　is　not　changed；　it　will　ascend；

if　the　planes　are　changed　to　15　degrees　to　correspond

with　the　kite　angle　it　will　remain　stationary。



GLIDING　FLIGHT。The　earliest　attempt　to　fly

by　gliding　is　attributed　to　Oliver；　a　Monk　of

Malmesbury　who；　in　1065　prepared　artificial

wings；　and　with　them　jumped　from　a　tower；　being

injured　in　the　experiment。



Nearly　700　years　later；　in　1801；　Resnier；　a

Frenchman；　conducted　experiments　with　varying

results；　followed　by　Berblinger；　in　1842；　and

LeBris；　a　French　sailor；　in　1856。



In　1884；　J。　J。　Montgomery；　of　California；　designed

a　successful　glider；　and　in　1889　Otto　and

Gustav　Lilienthal　made　the　most　extended　tests；

in　Germany；　and　became　experts　in　handling

gliders。



Pilcher；　in　England；　was　the　next　to　take　up　the

subject；　and　in　1893　made　many　successful　glides；

all　of　the　foregoing　machines　being　single　plane

surfaces；　similar　to　the　monoplane。



Long　prior　to　1896　Octave　Chanute；　an

engineer；　gave　the　subject　much　study；　and　in　that

year　made　many　remarkable　flights；　developing

the　double　plane；　now　known　as　the　biplane。



He　was　an　ardent　believer　in　the　ability　of　man

to　fly　by　soaring　means；　and　without　using　power

for　the　purpose。



It　is　doubtful　whether　gliders　contributed　much

to　the　art　in　the　direction　of　laterally　stabilizing

aeroplanes。　They　taught　useful　lessons　with　respect

to　area　and　fore　and　aft　control。



The　kite　gave　the　first　impulse　to　seek　out　a

means　for　giving　equilibrium　to　planes；　and

Montgomery　made　a　kite　with　warping　wings　as

early　as　1884。



Penaud；　a　Frenchman；　in　1872；　made　a　model

aeroplane　which　had　the　stabilizing　means　in　the

tail。　All　these　grew　out　of　kite　experiments；　and

all　gliders　followed　the　kite　construction；　or　the

principles　involved　in　them；　so　that；　really；　there

is　but　one　intervening　step　between　the　kite　and

the　flying　machine；　as　we　know　it；　the　latter　being

merely　kites　with　power　attached；　as　substitutes

for　the　cords。



ONE　OF　THE　USES　OF　GLIDER　EXPERIMENTS。

There　is　one　direction　in　which　gliders　are　valuable

to　the　boy　and　to　the　novice　who　are　interested

in　aviation。　He　may　spend　a　lifetime　in

gliding　and　not　advance　in　the　art。　It　is

questionable　whether　in　a　scientific　way　it　will　be　of

any　service　to　him；　but　experiments　of　this　character

give　confidence；　the　ability　to　quickly　grasp

a　situation；　and　it　will　thus　teach　self　reliance　in

emergencies。



When　in　a　glider　quick　thinking　is　necessary。

The　ability　to　shift　from　one　position　to　another；

to　apply　the　weight　where　required　instantaneously；

to　be　able　during　the　brief　exciting　moment

of　flight　to　know　just　what　to　do；　requires　alertness。



Some　are　so　wedded　to　the　earth　that　slight

elevation　disturbs　them。　The　sensation　in　a

glider　while　in　flight　is　unlike　any　other　experience。

It　is　like　riding　a　lot　of　tense　springs；　and　the

exhilaration　in　gliding　down　the　side　of　a　hill；

with　the　feet　free　and　body　suspended；　is　quite

different　from　riding　in　an　aeroplane　with　power

attached。



HINTS　IN　GLIDING。It　seems　to　be　a　difficult

matter　to　give　any　advice　in　the　art　of　gliding。　It

is　a　feat　which　seems　to　necessitate　experiment

from　first　to　last。　During　the　hundreds　of　tests

personally　made；　and　after　witnessing　thousands

of　attempts；　there　seems　to　be　only　a　few　suggestions

or　possible　directions　in　which　caution　might

be　offered。



First；　in　respect　to　the　position　of　the　body　at

the　moment　of　launching。　The　glider　is　usually

so　made　that　in　carrying　it；　preparatory　to　making

the　run　and　the　leap　required　to　glide；　it　is　held

so　that　it　balances　in　the　hands。



Now　the　center　of　air　pressure　in　gliding　may

not　be　at　the　same　point　as　its　sustaining　weight

when　held　by　the　hand；　and　furthermore；　as　the

arm…pits；　by　which　the　body　of　the　experimenter

are　held　while　gliding；　are　not　at　the　same　point；

but　to　the　rear　of　the　hands；　the　moment　the　glider

is　launched　too　great　a　weight　is　brought　to　the

rear　margin　of　the　planes；　hence　its　forward　end

lifts　up。



This　condition　will　soon　manifest　itself；　and　be

corrected　by　the　experimenter；　but　there　is　another

difficulty　which　is　not　so　easy　to　discover

and　so　quick　to　remedy；　and　that　is　the　swing　of

the　legs　the　moment　the　operator　leaves　the

ground。



The　experimenter　learns；　after　many　attempts；

that　gliding　is　a　matter　of　a　few　feet　only；　and　he

anticipates　landing　too　soon；　and　the　moment　he

leaps　from　the　ground　the　legs　are　swung　forwardly

ready　to　alight。



This　is　done　unconsciously；　just　as　a　jumper

swings　his　legs　forwardly　in　the　act　of　alighting。

Such　a　motion　naturally　disturbs　the　fore　and　aft

stability　of　the　gliding　machine；　by　tilting　up　the

forward　margin；　and　it　banks　against　the　air；

instead　of　gliding。



The　constant　fear　of　all　gliders　is；　that　the

machine　will　point　downwardly；　and　his　motion；

as　well　as　the　position　of　the　body；　tend　to　shoot

it　upwardly；　instead。







CHAPTER　IX



AEROPLANE　CONSTRUCTION





As　may　be　inferred　from　the　foregoing　statements；

there　are　no　definite　rules　for　the　construction

of　either　type　of　flying　machine；　as　the

flying　models　vary　to　such　an　extent　that　it　is

difficult　to　take　either　of　them　as　a　model　to　represent

the　preferred　type　of　construction。



LATERAL；　AND　FORE　AND　AFT。The　term　lateral

should　be　understood；　as　applied　to　aeroplanes。

It　is　always　used　to　designate　the　direction　at

right　angles　to　the　movement　of　the　machine。

Fore　and　aft　is　a　marine　term　meaning　lengthwise；

or　from　front　to　rear；　hence　is　always　at　right

angles　to　the　lateral　direction。



The　term　transverse　is　equivalent　to　lateral；

in　flying　machine　parlance；　but　there　is　this

distinction：　Transverse　has　reference　to　a　machine

or　object　which；　like　the　main　planes　of　an　aeroplane；

are　broader；　（that　is；from　end　to　end）

than　their　length；　（from　front　to　rear）。



On　the　other　hand；　lateral　has　reference　to　side

branches；　as；　for　instance；　the　monoplane　wings；

which　branch　out　from　the　sides　of　the　fore　and

aft　body。



STABILITY　AND　STABILIZATION。These　terms　constantly

appear　in　describing　machines　and　their

operations。　If　the　flying　structure；　whatever　it

may　be；　has　means　whereby　it　is　kept　from　rocking

from　side　to　side；　it　has　stability；　which　is　usually

designated　as　lateral　stability。　The　mechanism

for　doing　this　is　called　a　stabilizer。



THE　WRIGHT　SYSTEM。The　Wright　machine　has

reference　solely　to　the　matter　of　laterally　controlling

the　flying　structure；　and　does　not　pertain

to　the　form　or　shape　of　the　planes。



In　Fig。　49　A　designates　the　upper　and　lower

planes　of　a　Wright　machine；　with　the　peculiar

rounded　ends。　The　ends　of　the　planes　are　so

arranged　that　the　rear　margins　may　be　raised　or

lowered；　independently　of　the　other　portions　of

the　planes；　which　are　rigid。　This　movement　is

indicated　in　sketch　1；　where　the　movable　part　B

is；　as　we　might　say；　hinged　along　the　line　C。



The　dotted　line　D　on　the　right　hand　end；　shows

how　the　section　is　depressed；　while　the　dotted

lines　E　at　the　left　hand　end　shows　the　section

raised。　It　is　obvious　that　the　downturned　ends；

as　at　D；　will　give　a　positive　angle　at　one　end　of　the

planes；　and　the　upturned　wings　E　at　the　other　end

will　give　a　negative　angle；　and　thus　cause　the　right

hand　end　to　raise；　and　the　other　end　to　move

downwardly；　as　the　machine　moves　forwardly

through　the　air。



CONTROLLING　THE　WARPING　ENDS。Originally

the　Wrights　controlled　these　warping　sections　by

means　of　a　cradle　occupied　by　the　aviator；　so　that

the　cradle　would　move　or　rock；　dependent　on　the

tilt　of　the　machine。　This　was　what　was　termed

automatic　control。　This　was　found　to　be　unsatisfactory；

and　the　control　has　now　been　placed　so

that　it　connects　with　a　lever　and　is　operated　by

the　aviator；　and　is　called　Manually…operated　control。



In　all　forms　of　control　the　wings　on　one　side　are

depressed　on　one　side　and　correspondingly　elevated

on　the　other。



THE　CURTIS　WINGS。Curtis　has　small　wings；

or　ailerons；　intermediate　the　supporting　surfaces；

and　at　their　extremities；　as　shown　in　sketch　2。

These　are　controlled　by　a　shoulder　rack　or　swinging

frame　operated　by　the　driver；　so　that　the　body

in　swinging　laterally　will　change　the　two　wings

at　the　same　time；　but　with　angles　in　different

directions。



THE　FARMAN　AILERONS。Farman's　disposition

is　somewhat　different；　as　shown　in　sketch　3。　The

wings　are　hinged　to　the　upper　planes　at　their　rear

edges；　and　near　the　extremities　of　the　planes。

Operating　wires　lead　to　a　lever　within　reach　of　the

aviator；　and；　by　this　means；　the　wings　are　held　at

any　desired　angle；　or　changed　at　will。



The　difficulty　of　using　any　particular　model；　is

true；　also；　of　the　arrangement　of　the　fore　and　aft

control；　as　well　as　the　means　for　laterally　stabilizing

it。　In　view　of　this　we　shall　submit　a　general

form；　which　may　be　departed　from　at　will。



FEATURES　WELL　DEVELOPED。Certain　features

are　fairly　well　developed；　however。　One　is　the

angle　of　the　supporting　plane；　with　reference　to

the　frame　itself；　and　the　other　is　the　height　at

which　the　tail　and　rudder　should　be　placed　above

the　surface　of　the　ground　when　the　machine　is　at

rest。



DEPRESSING　THE　REAR　END。This　latter　is　a

matter　which　must　be　taken　into　consideration；

because　in　initiating　flight　the　rear　end　of　the

frame　is　depressed　in　order　to　give　a　sufficient

angle　to　the　supporting　planes　so　as　to　be　able　to

inaugurate　flight。



In　order　to　commence　building　we　should　have

some　definite　idea　with　respect　to　the　power；　as

this　will；　in　a　measure；　determine　the　area　of　the

supporting　surfaces；　as　a　whole；　and　from　this

the　sizes　of　the　different　planes　may　be　determined。



DETERMINING　THE　SIZE。Suppose　we　decide　on

300　square　feet　of　sustaining　surface。　This　may

require　a　30；　a　40　or　a　50　horse　power　motor；

dependent　on　the　speed　required；　and　much　higher

power　has　been　used　on　that　area。



However；　let　us　assume　that　a　forty　horse　power

motor　is　available；　our　300　square　feet　of　surface

may　be　put　into　two　planes；　each　having　150　square

feet　of　surface；　which　would　make　each　5'　by　30'

in　size；　or；　it　may　be　decided　to　make　the　plane