aeroplanes-第15节

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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　planes

narrower；　and　proportionally　longer。　This　is　immaterial。

The　shorter　the　planes　transversely；

the　greater　will　be　the　stability；　and　the　wider　the

planes　the　less　will　be　the　lift；　comparatively。



RULE　FOR　PLACING　THE　PLANES。The　rule　for

placing　the　planes　is　to　place　them　apart　a　distance

equal　to　the　width　of　the　planes　themselves；

so　that　if　we　decide　on　making　them　five　feet　wide；

they　should　be　placed　at　least　five　feet　apart。

This　rule；　while　it　is　an　admirable　one　for　slow

movements　or　when　starting　flight；　is　not　of　any

advantage　while　in　rapid　flight。



If　the　machine　is　made　with　front　and　rear

horizontally…disposed　rudders；　or　elevators；　they

also　serve　as　sustaining　surfaces；　which；　for　the

present　will　be　disregarded。



Lay　off　a　square　A；　Fig。　49a；　in　which　the　vertical

lines　B；　B；　and　the　horizontal　lines　C；　C；　are

5'　long；　and　draw　a　cross　D　within　this；　the　lines

running　diagonally　from　the　corners。



Now　step　off　from　the　center　cross　line　D；　three

spaces；　each　five　feet　long；　to　a　point　E；　and　join

this　point　by　means　of　upper　and　lower　bars　F；

G；　with　the　upper　and　lower　planes；　so　as　to　form

the　tail　frame。



_Fig。　49a。　Rule　for　spacing　Planes。_



As　shown　in　Fig。　50；　the　planes　should　now　be

indicated；　and　placed　at　an　angle　of　about　8　degrees

angle；　which　are　illustrated；　H　being　the

upper　and　I　the　lower　plane。　Midway　between　the

forward　edges　of　the　two　planes；　is　a　horizontal

line　J；　extending　forwardly；　and　by　stepping　off

the　width　of　two　planes；　a　point　K　is　made；　which

forms　the　apex　of　a　frame　L；　the　rear　ends　of　the

bars　being　attached　to　the　respective　planes　H；　I；

at　their　forward　edges。



_Fig。　50。　Frame　of　Control　Planes。_



_Fig。　51。　and　Fig。　52。_



ELEVATING　PLANES。We　must　now　have　the　general

side　elevation　of　the　frame；　the　planes；　their

angles；　the　tail　and　the　rudder　support；　and　the

frame　for　the　forward　elevator。



To　this　may　be　added　the　forward　elevating

plane　L；　the　rear　elevator；　or　tail　M；　and　the　vertical

steering　rudder　N。



The　frame　which　supports　the　structure　thus

described；　may　be　made　in　a　variety　of　ways；　the

object　being　to　provide　a　resilient　connection　for

the　rear　wheel　O。



Fig。　52　shows　a　frame　which　is　simple　in　construction

and　easily　attached。　The　lower　fore

and　aft　side　bars　P　have　the　single　front　wheel

axle　at　the　forward　end；　and　the　aft　double　wheels

at　the　rear　end；　a　flexible　bar　Q；　running　from　the

rear　wheel　axle　to　the　forward　end　of　the　lower

plane。



A　compression　spring　R　is　also　mounted　between

the　bar　and　rear　end　of　the　lower　plane　to

take　the　shock　of　landing。　The　forward　end　of

the　bar　P　has　a　brace　S　extending　up　to　the　front

edge　of　the　lower　plane；　and　another　brace　T　connects

the　bars　P；　S；　with　the　end　of　the　forwardly…

projecting　frame。



_Fig。　53。　Plan　view。_



The　full　page　view；　Fig。　53；　represents　a