aeroplanes-第14节

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of　which　is　a　right…angled　triangle。



_Fig。　44。　and　45。　Deltoid　Formation。_



The　peculiarity　of　this　formation　is；　that　it　has

remarkable　stability　when　used　as　a　kite；　with

either　end　foremost。　If　a　small　weight　is　placed

at　the　pointed　end；　and　it　is　projected　through　the

air；　it　will　fly　straight；　and　is　but　little　affected

by　cross　currents。



THE　DUNNE　FLYING　MACHINE。A　top　view　of

this　biplane　is　shown　in　Fig。　46。　The　A…shaped

disposition　of　the　planes；　gives　it　good　lateral

stability；　but　it　has　the　disadvantage　under　which

all　aeroplanes　labor；　that　the　entire　body　of　the

machine　must　move　on　a　fore　and　aft　vertical

plan　in　order　to　ascend　or　descend。



_Fig。　46。　The　Dunne　Bi…plane。_



This　is　a　true　deltoid　formation；　as　the　angle　of

incidence　of　the　planes　is　so　disposed　that　when

the　planes　are　horizontal　from　end　to　end；　the　inclination

is　such　as　to　make　it　similar　to　the　deltoid

kite　referred　to。



ROTATING　KITE。A　type　of　kite　unlike　the

others　illustrated　is　a　rotating　structure；　which

gives　great　stability；　due　to　the　gyroscopic　action

on　the　supporting　surfaces。



Fig。　47　shows　a　side　view　with　the　top　in　section。

The　supporting　surface　is　umbrella…shaped。

In　fact；　the　ordinary　umbrella　will　answer　if　not

dished　too　much。　An　angularly…bent　piece　of　wire

A；　provided　with　loops　B；　B；　at　the　ends；　serve　as

bearings　for　the　handle　of　the　umbrella。



At　the　bend　of　the　wire　loop　C；　the　cord　D　is

attached。　The　lower　side　of　the　umbrella　top　has

cup…shaped　pockets　E；　near　the　margin；　so　arranged

that　their　open　ends　project　in　the　same

direction；　and　the　wind　catching　them　rotates　the

circular　plane。



_Fig。　47。　Rotable　Umbrella　Kite。_



KITE　PRINCIPLES。A　careful　study　of　the　examples

here　given；　will　impress　the　novice　with

one　important　fact；　which；　in　its　effect　has　a　more

important　bearing　on　successful　flight；　than　all

the　bird　study　and　speculations　concerning　its

mysteries。



This　fact；　in　essence；　is；　that　the　angle　of　the

kite　is　the　great　factor　in　flight　next　to　the　power

necessary　to　hold　it。　Aside　from　this；　the

comparison　between　kites　and　aeroplanes　is　of　no

practical　value。



Disregarding　the　element　of　momentum；　the

drift　of　a　machine　against　a　wind；　is　the　same；

dynamically；　as　a　plane　at　rest　with　the　wind

moving　past　it。　But　there　is　this　pronounced

difference：　The　cord　which　supports　the　kite

holds　it　so　that　the　power　is　in　one　direction　only。



When　a　side　gust　of　wind　strikes　the　kite　it

is　moved　laterally；　in　sympathy　with　the　kite；

hence　the　problem　of　lateral　displacement　is　not

the　same　as　with　the　aeroplane。



LATERAL　STABILITY　IN　KITES。In　the　latter　the

power　is　definitely　fixed　with　relation　to　the　machine

itself；　and　if　we　should　assume　that　a　plane

with　a　power　on　it　sufficient　to　maintain　a　flight

of　40　miles　an　hour；　should　meet　a　wind　moving

at　the　same　speed；　the　machine　would　be　stationary

in　space。



Such　a　condition　would　be　the　same；　so　far　as

the　angles　of　the　planes　are　concerned；　with　a

kite　held　by　a　string；　but　there　all　similarity　in

action　ends。



The　stabilizing　quality　of　the　kite　may　be　perfect；

as　the　wind　varies　from　side　to　side；　but　the

aeroplane；　being　free；　moves　to　the　right　or　to

the　left；　and　does　not　adjust　itself　by　means　of　a

fixed　point；　but　by　a　movable　one。



SIMILARITY　OF　FORE　AND　AFT　CONTROL。Fore

and　aft；　however；　the　kite　and　aeroplane　act　the

same。　Fig。　48　shows　a　diagram　which　illustrates

the　forces　which　act　on　the　kite；　and　by　means

of　which　it　adjusts　its　angle　automatically。



Let　us　assume　that　the　kite　A　is　flown　from

a　cord　B；　so　that　its　angle　is　22　1/2　degrees；　the

wind　being　15　miles　per　hour　to　maintain　the

cord　B　at　that　angle。　When　the　wind　increases

to　20　miles　an　hour　there　is　a　correspondingly

greater　lift　against　the　kite。



_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

a