flying machines-第4部分

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the　concave　surface　downward；　a　sort　of　inverted　bowl

is　formed　in　which　the　air　gathers　and　exerts　a　buoyant

effect。　Just　what　the　ratio　of　the　curve　should　be　is　a

matter　of　contention。　In　some　instances　one　inch　to　the

foot　is　found　to　be　satisfactory；　in　others　this　is　doubled；

and　there　are　a　few　cases　in　which　a　curve　of　as　much　as

3　inches　to　the　foot　has　been　used。



Right　here　it　might　be　well　to　explain　that　the　word

〃plane〃　applied　to　flying　machines　of　modern　construction

is　in　reality　a　misnomer。　Plane　indicates　a　flat；

level　surface。　As　most　successful　flying　machines　have

curved　supporting　surfaces　it　is　clearly　wrong　to　speak

of　〃planes；〃　or　〃aeroplanes。〃　Usage；　however；　has　made

the　terms　convenient　and；　as　they　are　generally　accepted

and　understood　by　the　public；　they　are　used　in　like　manner

in　this　volume。



Getting　Under　Headway。



A　bird；　on　first　rising　from　the　ground；　or　beginning

its　flight　from　a　tree；　will　flap　its　wings　to　get　under

headway。　Here　again　we　have　another　illustration　of

the　manner　in　which　a　flying　machine　gets　under　headway

the　motor　imparts　the　force　necessary　to　put　the

machine　into　the　air；　but　right　here　the　similarity　ceases。

If　the　machine　is　to　be　kept　afloat　the　motor　must　be

kept　moving。　A　flying　machine　will　not　sustain　itself；

it　will　not　remain　suspended　in　the　air　unless　it　is

under　headway。　This　is　because　it　is　heavier　than　air；

and　gravity　draws　it　to　the　ground。



Puzzle　in　Bird　Soaring。



But　a　bird；　which　is　also　heavier　than　air；　will　remain

suspended；　in　a　calm；　will　even　soar　and　move　in　a

circle；　without　apparent　movement　of　its　wings。　This

is　explained　on　the　theory　that　there　are　generally　vertical

columns　of　air　in　circulation　strong　enough　to　sustain

a　bird；　but　much　too　weak　to　exert　any　lifting　power

on　a　flying　machine；　It　is　easy　to　understand　how　a

bird　can　remain　suspended　when　the　wind　is　in　action；

but　its　suspension　in　a　seeming　dead　calm　was　a　puzzle

to　scientists　until　Mr。　Chanute　advanced　the　proposition

of　vertical　columns　of　air。



Modeled　Closely　After　Birds。



So　far　as　possible；　builders　of　flying　machines　have

taken　what　may　be　called　〃the　architecture〃　of　birds　as

a　model。　This　is　readily　noticeable　in　the　form　of

construction。　When　a　bird　is　in　motion　its　wings　（except

when　flapping）　are　extended　in　a　straight　line　at　right

angles　to　its　body。　This　brings　a　sharp；　thin　edge

against　the　air；　offering　the　least　possible　surface　for

resistance；　while　at　the　same　time　a　broad　surface　for

support　is　afforded　by　the　flat；　under　side　of　the　wings。

Identically　the　same　thing　is　done　in　the　construction　of

the　flying　machine。



Note；　for　instance；　the　marked　similarity　in　form　as

shown　in　the　illustration　in　Chapter　II。　Here　A　is　the

bird；　and　B　the　general　outline　of　the　machine。　The

thin　edge　of　the　plane　in　the　latter　is　almost　a　duplicate

of　that　formed　by　the　outstretched　wings　of　the　bird；

while　the　rudder　plane　in　the　rear　serves　the　same　purpose

as　the　bird's　tail。







CHAPTER　IV。



VARIOUS　FORMS　OF　FLYING　MACHINES。



There　are　three　distinct　and　radically　different　forms

of　flying　machines。　These　are：



Aeroplanes；　helicopters　and　ornithopers。



Of　these　the　aeroplane　takes　precedence　and　is　used

almost　exclusively　by　successful　aviators；　the　helicopters

and　ornithopers　having　been　tried　and　found　lacking　in

some　vital　features；　while　at　the　same　time　in　some

respects　the　helicopter　has　advantages　not　found　in　the

aeroplane。



What　the　Helicopter　Is。



The　helicopter　gets　its　name　from　being　fitted　with

vertical　propellers　or　helices　（see　illustration）　by　the

action　of　which　the　machine　is　raised　directly　from　the

ground　into　the　air。　This　does　away　with　the　necessity

for　getting　the　machine　under　a　gliding　headway　before

it　floats；　as　is　the　case　with　the　aeroplane；　and　consequently

the　helicopter　can　be　handled　in　a　much　smaller

space　than　is　required　for　an　aeroplane。　This；　in　many

instances；　is　an　important　advantage；　but　it　is　the　only

one　the　helicopter　possesses；　and　is　more　than　overcome

by　its　drawbacks。　The　most　serious　of　these　is　that　the

helicopter　is　deficient　in　sustaining　capacity；　and　requires

too　much　motive　power。



Form　of　the　Ornithopter。



The　ornithopter　has　hinged　planes　which　work　like

the　wings　of　a　bird。　At　first　thought　this　would　seem

to　be　the　correct　principle；　and　most　of　the　early　experimenters

conducted　their　operations　on　this　line。　It

is　now　generally　understood；　however；　that　the　bird　in

soaring　is　in　reality　an　aeroplane；　its　extended　wings

serving　to　sustain；　as　well　as　propel；　the　body。　At　any

rate　the　ornithoper　has　not　been　successful　in　aviation；

and　has　been　interesting　mainly　as　an　ingenious　toy。

Attempts　to　construct　it　on　a　scale　that　would　permit

of　its　use　by　man　in　actual　aerial　flights　have　been　far

from　encouraging。



Three　Kinds　of　Aeroplanes。



There　are　three　forms　of　aeroplanes；　with　all　of　which

more　or　less　success　has　been　attained。　These　are：



The　monoplane；　a　one…surfaced　plane；　like　that　used

by　Bleriot。



The　biplane；　a　two…surfaced　plane；　now　used　by　the

Wrights；　Curtiss；　Farman；　and　others。



The　triplane；　a　three…surfaced　plane　This　form　is

but　little　used；　its　only　prominent　advocate　at　present

being　Elle　Lavimer；　a　Danish　experimenter；　who　has　not

thus　far　accomplished　much。



Whatever　of　real　success　has　been　accomplished　in

aviation　may　be　credited　to　the　monoplane　and　biplane；

with　the　balance　in　favor　of　the　latter。　The　monoplane

is　the　more　simple　in　construction　and；　where　weight…

sustaining　capacity　is　not　a　prime　requisite；　may

probably　be　found　the　most　convenient。　This　opinion　is

based　on　the　fact　that　the　smaller　the　surface　of　the

plane　the　less　will　be　the　resistance　offered　to　the　air；

and　the　greater　will　be　the　speed　at　which　the　machine

may　be　moved。　On　the　other　hand；　the　biplane　has　a

much　greater　plane　surface　（double　that　of　a　monoplane

of　the　same　size）　and　consequently　much　greater　weight…

carrying　capacity。



Differences　in　Biplanes。



While　all　biplanes　are　of　the　same　general　construction

so　far　as　the　main　planes　are　concerned；　each　aviator

has　his　own　ideas　as　to　the　〃rigging。〃



Wright；　for　instance；　places　a　double　horizontal　rudder

in　front；　with　a　vertical　rudder　in　the　rear。　There

are　no　partitions　between　the　main　planes；　and　the

bicycle　wheels　used　on　other　forms　are　replaced　by　skids。



Voisin；　on　the　contrary；　divides　the　main　planes　with

vertical　partitions　to　increase　stability　in　turning；　uses

a　single…plane　horizontal　rudder　in　front；　and　a　big　box…

tail　with　vertical　rudder　at　the　rear；　also　the　bicycle

wheels。



Curtiss　attaches　horizontal　stabilizing　surfaces　to　the

upper　plane；　has　a　double　horizontal　rudder　in　front；

with　a　vertical　rudder　and　horizontal　stabilizing　surfaces

in　rear。　Also　the　bicycle　wheel　alighting　gear。







CHAPTER　V。



CONSTRUCTING　A　GLIDING　MACHINE。



First　decide　upon　the　kind　of　a　machine　you　want

monoplane；　biplane；　or　triplane。　For　a　novice　the　biplane

will；　as　a　rule；　be　found　the　most　satisfactory　as

it　is　more　compact　and　therefore　the　more　easily　handled。

This　will　be　easily　understood　when　we　realize　that　the

surface　of　a　flying　machine　should　be　laid　out　in　proportion

to　the　amount　of　weight　it　will　have　to　sustain。

The　generally　accepted　rule　is　that　152　square　feet　of

surface　will　sustain　the　weight　of　an　average…sized　man；

say　170　pounds。　Now　it　follows　that　if　these　152　square

feet　of　surface　are　used　in　one　plane；　as　in　the　monoplane；

the　length　and　width　of　this　plane　must　be　greater

than　if　the　same　amount　of　surface　is　secured　by　using

two　planesthe　biplane。　This　results　in　the　biplane

being　more　compact　and　therefore　more　readily　manipulated

than　the　monoplane；　which　is　an　important　item

for　a　novice。



Glider　the　Basis　of　Success。



Flying　machines　without　motors　are　called　gliders。　In

making　a　flying　machine　you　first　construct　the　glider。

If　you　use　it　in　this　form　it　remains　a　glider。　If　you

install　a　motor　it　becomes　a　flying　machine。　You　must

have　a　good　glider　as　the　basis　of　a　successful　flying

machine。



It　will　be　well　for　the　novice；　the　man　who　has　never

had　any　experience　as　an　aviator；　to　begin　with　a　glider

and　master　its　construction　and　operation　before　he

essays　the　more　pretentious　task　of　handling　a　fully…

equipped　flying　machine。　In　fact；　it　is　essential　that　he

should　do　so。



Plans　for　Handy　Glider。



A　glider　with　a　spread　（advancing　edge）　of　20　feet；　and

a　breadth　or　depth　of　4　feet；　will　be　about　right　to　begin

with。　Two　planes　of　this　size　will　give　the　152　square

yards　of　surface　necessary　to　sustain　a　man's　weight。

Remember　that　in　referring　to　flying　machine　measurements

〃spread〃　takes　the　place　of　what　would　ordinarily

be　called　〃length；〃　and　invariably　applies　to　the　long

or　advancing　edge　of　the　machine　which　cuts　into　the　air。

Thus；　a　glider　is　spoken　of　as　being　20　feet　spread；　and

4　feet　in　depth。　So　far　as　mastering　the　control　of　the

machine　is　concerned；　learning　to　balance　one's　self　in

the　air；　guiding　the　machine　in　any　desired　direction　by

changing　the　position　of　the　body；　etc。；　all　this　may　be

learned　just　as　readily；　and　perhaps　more　so；　with　a　20…

foot　glider　than　with　a　larger　apparatus。



Kind　of　Material　Required。



There　are　three　all…important　features　in　flying　machine

construction；　viz。：　lightness；　strength　and　extreme

rigidity。　Spruce　is　the　wood　generally　used　for　glider

frames。　Oak；　ash　and　hickory　are　all　stronger；　but　they

are　also　considerably　heavier；　and　where　the　saving　of

weight　is　essential；　the　difference　is　largely　in　favor　of

spruce。　This　will　be　seen　in　the　following　table：