aeroplanes-第13章

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cannot　follow　the　curve　rapidly　enough　to　maintain

the　same　density　along　C；　hence　this　exerts



an　upward　pull；　due　to　the　rarefied　area；　which

serves　as　a　lifting　force；　as　well　as　the　compressed

mass　beneath　the　plane。



CHANGING　CENTER　OF　PRESSURE。The　center　of

pressure　is　not　constant。　It　changes　with　the

angle　of　the　plane；　but　the　range　is　considerably

less　on　a　concave　surface　than　on　a　flat　plane。



_Fig。　25。　Air　lines　above　a　convex　Plane。_



In　a　plane　disposed　at　a　small　angle；　A；　as　in

Fig。　26；　the　center　of　pressure　is　nearer　the　forward

end　of　the　plane　than　with　a　greater　positive

angle　of　incidence；　as　in　Fig。　27；　and　when

the　plane　is　in　a　normal　flying　angle；　it　is　at　the

center；　or　at　a　point　midway　between　the　margins。



PLANE　MONSTROSITIES。Growing　out　of　the　idea

that　the　wing　in　nature　must　be　faithfully　copied；

it　is　believed　by　many　that　a　plane　with　a

pronounced　thickness　at　its　forward　margin　is　one

of　the　secrets　of　bird　flight。



Accordingly　certain　inventors　have　designed

types　of　wings　which　are　shown　in　Figs。　28　and

29。



_Fig。　28　Changing　centers　of　Pressures。_



_Fig　29。　Bird…wing　structures。_



Both　of　these　types　have　pronounced　bulges；

designed　to　〃split〃　the　air；　forgetting；　apparently；

that　in　other　parts　of　the　machine　every　effort　is

made　to　prevent　head　resistance。



THE　BIRD　WING　STRUCTURE。The　advocates　of

such　construction　maintain　that　the　forward　edge

of　the　plane　must　forcibly　drive　the　air　column

apart；　because　the　bird　wing　is　so　made；　and　that

while　it　may　not　appear　exactly　logical；　still　there

is　something　about　it　which　seems　to　do　the　work；

and　for　that　reason　it　is　largely　adopted。



WHY　THE　BIRD'S　WING　HAS　A　PRONOUNCED

BULGE。Let　us　examine　this　claim。　The　bone

which　supports　the　entire　wing　surface；　called　the

（pectoral）；　has　a　heavy　duty　to　perform。　It　is　so

constructed　that　it　must　withstand　an　extraordinary

torsional　strain；　being　located　at　the　forward

portion　of　the　wing　surface。　Torsion　has

reference　to　a　twisting　motion。



In　some　cases；　as　in　the　bat；　this　primary　bone

has　an　attachment　to　the　rear　of　the　main　joint；

where　the　rear　margin　of　the　wing　is　attached　to

the　leg　of　the　animal；　thus　giving　it　a　support

and　the　main　bone　is；　therefore；　relieved　of　this

torsional　stress。



THE　BAT'S　WING。An　examination　of　the　bat's

wing　shows　that　the　pectoral　bone　is　very　small

and　thin；　thus　proving　that　when　the　entire　wing

support　is　thrown　upon　the　primary　bone　it　must

be　large　enough　to　enable　it　to　carry　out　its　functions。

It　is　certainly　not　so　made　because　it　is　a

necessary　shape　which　best　adapts　it　for　flying。



If　such　were　the　case　then　nature　erred　in　the

case　of　the　bat；　and　it　made　a　mistake　in　the

housefly's　wing　which　has　no　such　anterior　enlargement

to　assist　（？）　it　in　flying。



AN　ABNORMAL　SHAPE。Another　illustration　is

shown　in　Fig。　30；　which　has　a　deep　concave　directly

behind　the　forward　margin；　as　at　A；　so

that　when　the　plane　is　at　an　angle　of　about　22

degrees；　a　horizontal　line；　as　B；　passing　back　from

the　nose；　touches　the　incurved　surface　of　the　plane

at　a　point　about　one…third　of　its　measurement

back　across　the　plane。



_Fig。　30。　One　of　the　Monstrosities_



This　form　is　an　exact　copy　of　the　wing　of　an

actual　bird；　but　it　belongs；　not　to　the　soaring；

but　to　the　class　which　depends　on　flapping　wings；

and　as　such　it　cannot　be　understood　why　it　should

be　used　for　soaring　machines；　as　all　aeroplanes

are。



The　foregoing　instances　of　construction　are

cited　to　show　how　wildly　the　imagination　will

roam　when　it　follows　wrong　ideals。



THE　TAIL　AS　A　MONITOR。The　tendency　of　the

center　of　pressure　to　change　necessitates　a　correctional

means；　which　is　supplied　in　the　tail　of

the　machine；　just　as　the　tail　of　a　kite　serves　to

hold　it　at　a　correct　angle　with　respect　to　the　wind

and　the　pull　of　the　supporting　string。









CHAPTER　VII



ABNORMAL　FLYING　STUNTS　AND　SPEEDS





〃PEQUOD；　a　Frenchman；　yesterday　repeatedly

performed　the　remarkable　feat　of　flying　with　the

machine　upside　down。　This　exhibition　shows

that　the　age　of　perfection　has　arrived　in　flying

machines；　and　that　stability　is　an　accomplished

fact。〃News　item。





This　is　quoted　to　show　how　little　the　general

public　knows　of　the　subject　of　aviation。　It　correctly

represents　the　achievement　of　the　aviator；

and　it　probably　voiced　the　sentiment　of　many

scientific　men；　as　well　as　of　the　great　majority　of

aviators。



A　few　days　afterwards；　the　same　newspaper

published　the　following：





〃Lieutenant　；　while　experimenting　yesterday

morning；　met　his　death　by　the　overturning

of　his　machine　at　an　altitude　of　300　meters。

Death　was　instantaneous；　and　the　machine　was

completely　destroyed。〃



The　machines　used　by　the　two　men　were　of　the

same　manufacture；　as　Pequod　used　a　stock　machine

which　was　strongly　braced　to　support　the

inverted　weight；　but　otherwise　it　was　not　unlike

the　well　known　type　of　monoplane。



Beachy　has　since　repeated　the　experiment　with

a　bi…plane；　and　it　is　a　feat　which　has　many　imitators；

and　while　those　remarkable　exhibitions

are　going　on；　one　catastrophe　follows　the　other

with　the　same　regularity　as　in　the　past。



Let　us　consider　this　phase　of　flying。　Are　they

of　any　value；　and　wherein　do　they　teach　anything

that　may　be　utilized；



LACK　OF　IMPROVEMENTS　IN　MACHINES。It　is　remarkable

that　not　one　single　forward　step　has

been　taken　to　improve　the　type　of　flying　machines

for　the　past　five　years。　They　possess　the　same

shape；　their　stabilizing　qualities　and　mechanism

for　assuring　stability　are　still　the　same。



MEN　EXPEDITED；　AND　NOT　THE　MACHINE。The

fact　is；　that　during　this　period　the　man　has　been

exploited　and　not　the　machine。　Men　have　learned；

some　few　of　them；　to　perform　peculiar　stunts；

such　as　looping　the　loop；　the　side　glide；　the　drop；

and　other　features；　which　look；　and　are；　hazardous；

all　of　which　pander　to　the　sentiments　of　the　spectators。



ABNORMAL　FLYING　OF　NO　VALUE。It　would　be

too　broad　an　assertion　to　say　that　it　has　absolutely

no　value；　because　everything　has　its　use

in　a　certain　sense；　but　if　we　are　to　judge　from

the　progress　of　inventions　in　other　directions；

such　exhibitions　will　not　improve　the　art　of　building

the　device；　or　make　a　fool…proof　machine。



Indeed；　it　is　the　very　thing　which　serves　as　a

deterrent；　rather　than　an　incentive。　If　machines

can　be　handled　in　such　a　remarkable　manner；　they

must　be；　indeed；　perfect！　Nothing　more　is

needed！　They　must　represent　the　highest　structural

type　of　mechanism！



That　is　the　idea　sought　to　be　conveyed　in　the

first　paragraph　quoted。　It　is　pernicious；　instead

of　praiseworthy；　because　it　gives　a　false　impression；

and　it　is　remarkable　that　even　certain　scientific

journals　have　gravely　discussed　the　perfected

（？）　type　of　flying　machine　as　demonstrated

by　the　experiments　alluded　to。



THE　ART　OF　JUGGLING。We　may；　occasionally；

see　a　cyclist　who　understands　the　art　of　balancing

so　well　that　he　can；　with　ease；　ride　a　machine

which　has　only　a　single　wheel；　or　he　can；　with　a

stock　bicycle；　ride　it　in　every　conceivable　attitude；

and　make　it　perform　all　sorts　of　feats。



It　merely　shows　that　man　has　become　an

expert　at　juggling　with　a　machine；　the　same　as　he

manipulates　balls；　and　wheels；　and　other　artifices；

by　his　dexterity。



PRACTICAL　USES　THE　BEST　TEST。The　bicycle

did　not　require　such　displays　to　bring　it　to　perfection。

It　has　been　the　history　of　every　invention

that　improvements　were　brought　about；　not

by　abnormal　experiments；　but　by　practical　uses

and　by　normal　developments。



The　ability　of　an　aviator　to　fly　with　the　machine

in　an　inverted　position　is　no　test　of　the　machine's

stability；　nor　does　it　in　any　manner　prove　that

it　is　correctly　built。　It　is　simply　and