is¡¡the¡¡comparatively¡¡small¡¡head¡¡resistance£»¡¡due
to¡¡the¡¡entire¡¡absence¡¡of¡¡vertical¡¡supporting¡¡posts£»
which¡¡latter¡¡are¡¡necessary¡¡with¡¡the¡¡biplane¡¡type¡£
The¡¡bracing¡¡supports¡¡which¡¡hold¡¡the¡¡outer¡¡ends
of¡¡the¡¡planes¡¡are¡¡composed¡¡of¡¡wires£»¡¡which¡¡offer
but¡¡little¡¡resistance£»¡¡comparatively£»¡¡in¡¡flight¡£
ITS¡¡ADVANTAGES¡£Then¡¡the¡¡vertical¡¡height¡¡of
the¡¡machine¡¡is¡¡much¡¡less¡¡than¡¡in¡¡the¡¡biplane¡£¡¡As
a¡¡result¡¡the¡¡weight£»¡¡which¡¡is¡¡farther¡¡below¡¡the
supporting¡¡surface¡¡than¡¡in¡¡the¡¡biplane£»¡¡aids¡¡in
maintaining¡¡the¡¡lateral¡¡stability£»¡¡particularly
since¡¡the¡¡supporting¡¡frame¡¡is¡¡higher¡£
Usually£»¡¡for¡¡the¡¡same¡¡wing¡¡spread£»¡¡the¡¡monoplane
is¡¡narrower£»¡¡laterally£»¡¡which¡¡is¡¡a¡¡further
aid¡¡to¡¡prevent¡¡tilting¡£
ITS¡¡DISADVANTAGES¡£But¡¡it¡¡also¡¡has¡¡disadvantages
which¡¡must¡¡be¡¡apparent¡¡from¡¡its¡¡structure¡£
As¡¡all¡¡the¡¡supporting¡¡surface¡¡is¡¡concentrated
in¡¡half¡¡the¡¡number¡¡of¡¡planes£»¡¡they¡¡must
be¡¡made¡¡of¡¡greater¡¡width¡¡fore¡¡and¡¡aft£»¡¡and¡¡this£»
as¡¡we¡¡shall¡¡see£»¡¡later¡¡on£»¡¡proves¡¡to¡¡be¡¡a¡¡disadvantage¡£
It¡¡is¡¡also¡¡doubted¡¡whether¡¡the¡¡monoplane¡¡can
be¡¡made¡¡as¡¡strong¡¡structurally¡¡as¡¡the¡¡other¡¡form£»
owing¡¡to¡¡the¡¡lack¡¡of¡¡the¡¡truss¡¡formation¡¡which¡¡is
the¡¡strong¡¡point¡¡with¡¡the¡¡superposed¡¡frame¡£¡¡A
truss¡¡is¡¡a¡¡form¡¡of¡¡construction¡¡where¡¡braces¡¡can
be¡¡used¡¡from¡¡one¡¡member¡¡to¡¡the¡¡next£»¡¡so¡¡as¡¡to
brace¡¡and¡¡stiffen¡¡the¡¡whole¡£
THE¡¡BIPLANE¡£Nature¡¡does¡¡not¡¡furnish¡¡a¡¡type
of¡¡creature¡¡which¡¡has¡¡superposed¡¡wings¡£¡¡In¡¡this
particular¡¡the¡¡inventor¡¡surely¡¡did¡¡not¡¡follow¡¡nature¡£
The¡¡reasons¡¡which¡¡led¡¡man¡¡to¡¡employ¡¡this
type¡¡may¡¡be¡¡summarized¡¡as¡¡follows£º
In¡¡experimenting¡¡with¡¡planes¡¡it¡¡is¡¡found¡¡that
a¡¡broad¡¡fore¡¡and¡¡aft¡¡surface¡¡will¡¡not¡¡lift¡¡as¡¡much
as¡¡a¡¡narrow¡¡plane¡£¡¡This¡¡subject¡¡is¡¡fully¡¡explained
in¡¡the¡¡chapter¡¡on¡¡The¡¡Lifting¡¡Surfaces¡¡of
Planes¡£¡¡In¡¡view¡¡of¡¡that¡¡the¡¡technical¡¡descriptions
of¡¡the¡¡operation¡¡will¡¡not¡¡be¡¡touched¡¡upon
at¡¡this¡¡place£»¡¡except¡¡so¡¡far¡¡as¡¡it¡¡may¡¡be¡¡necessary
to¡¡set¡¡forth¡¡the¡¡present¡¡subject¡£
This¡¡peculiarity¡¡is¡¡due¡¡to¡¡the¡¡accumulation¡¡of
a¡¡mass¡¡of¡¡moving¡¡air¡¡at¡¡the¡¡rear¡¡end¡¡of¡¡the¡¡plane£»
which¡¡detracts¡¡from¡¡its¡¡lifting¡¡power¡£¡¡As¡¡it
would¡¡be¡¡a¡¡point¡¡of¡¡structural¡¡weakness¡¡to¡¡make
the¡¡wings¡¡narrow¡¡and¡¡very¡¡long£»¡¡Wenham¡¡many
years¡¡ago¡¡suggested¡¡the¡¡idea¡¡of¡¡placing¡¡one¡¡plane
above¡¡the¡¡other£»¡¡and¡¡later¡¡on¡¡Chanute£»¡¡an
engineer£»¡¡used¡¡that¡¡form¡¡almost¡¡exclusively£»¡¡in
experimenting¡¡with¡¡his¡¡gliders¡£
It¡¡was¡¡due¡¡to¡¡his¡¡influence¡¡that¡¡the¡¡Wrights
adopted¡¡that¡¡form¡¡in¡¡their¡¡gliding¡¡experiments£»
and¡¡later¡¡on¡¡constructed¡¡their¡¡successful¡¡flyers
in¡¡that¡¡manner¡£¡¡Originally¡¡the¡¡monoplane¡¡was
the¡¡type¡¡generally¡¡employed¡¡by¡¡experimenters£»
such¡¡as¡¡Lilienthal£»¡¡and¡¡others¡£
STABILITY¡¡IN¡¡BIPLANES¡£Biplanes¡¡are¡¡not¡¡naturally
as¡¡stable¡¡laterally¡¡as¡¡the¡¡monoplane¡£
The¡¡reason¡¡is£»¡¡that¡¡a¡¡downward¡¡tilt¡¡has¡¡the¡¡benefit
of¡¡only¡¡a¡¡narrow¡¡surface£»¡¡comparable¡¡with¡¡the
monoplane£»¡¡which¡¡has¡¡broadness¡¡of¡¡wing¡£
To¡¡illustrate¡¡this£»¡¡let¡¡us¡¡assume¡¡that¡¡we¡¡have
a¡¡biplane¡¡with¡¡planes¡¡five¡¡feet¡¡from¡¡front¡¡to¡¡rear£»
and¡¡thirty¡six¡¡feet¡¡in¡¡length¡£¡¡This¡¡would¡¡give
two¡¡planes¡¡with¡¡a¡¡sustaining¡¡surface¡¡of¡¡360¡¡square
feet¡£¡¡The¡¡monoplane¡¡would£»¡¡probably£»¡¡divide
this¡¡area¡¡into¡¡one¡¡plane¡¡eight¡¡and¡¡a¡¡half¡¡feet¡¡from
front¡¡to¡¡rear£»¡¡and¡¡42¡¡feet¡¡in¡¡length¡£
In¡¡the¡¡monoplane¡¡each¡¡wing¡¡would¡¡project¡¡out
about¡¡three¡¡feet¡¡more¡¡on¡¡each¡¡side£»¡¡but¡¡it¡¡would
have¡¡eight¡¡and¡¡a¡¡half¡¡feet¡¡fore¡¡and¡¡aft¡¡spread
to¡¡the¡¡biplane's¡¡five¡¡feet£»¡¡and¡¡thus¡¡act¡¡as¡¡a¡¡greater
support¡£
THE¡¡ORTHOPTER¡£The¡¡term¡¡orthopter£»¡¡or¡¡ornithopter£»
meaning¡¡bird¡¡wing£»¡¡is¡¡applied¡¡to¡¡such
flying¡¡machines¡¡as¡¡depend¡¡on¡¡wing¡¡motion¡¡to¡¡support
them¡¡in¡¡the¡¡air¡£
Unquestionably£»¡¡a¡¡support¡¡can¡¡be¡¡obtained¡¡by
beating¡¡on¡¡the¡¡air¡¡but¡¡to¡¡do¡¡so¡¡it¡¡is¡¡necessary¡¡to
adopt¡¡the¡¡principle¡¡employed¡¡by¡¡nature¡¡to¡¡secure
an¡¡upward¡¡propulsion¡£¡¡As¡¡pointed¡¡out¡¡elsewhere£»
it¡¡cannot¡¡be¡¡the¡¡concaved¡¡type¡¡of¡¡wing£»
or¡¡its¡¡shape£»¡¡or¡¡relative¡¡size¡¡to¡¡the¡¡weight¡¡it¡¡must
carry¡£
As¡¡nature¡¡has¡¡furnished¡¡such¡¡a¡¡variety¡¡of¡¡data
on¡¡these¡¡points£»¡¡all¡¡varying¡¡to¡¡such¡¡a¡¡remarkable
degree£»¡¡we¡¡must¡¡look¡¡elsewhere¡¡to¡¡find¡¡the¡¡secret¡£
Only¡¡one¡¡other¡¡direction¡¡offers¡¡any¡¡opportunity£»
and¡¡that¡¡is¡¡in¡¡the¡¡individual¡¡wing¡¡movement¡£
NATURE'S¡¡TYPE¡¡NOT¡¡UNIFORM¡£When¡¡this¡¡is
examined£»¡¡the¡¡same¡¡obscurity¡¡surrounds¡¡the¡¡issue¡£
Even¡¡the¡¡speeds¡¡vary¡¡to¡¡such¡¡an¡¡extent¡¡that¡¡when
it¡¡is¡¡tried¡¡to¡¡differentiate¡¡them£»¡¡in¡¡comparison
with¡¡form£»¡¡shape£»¡¡and¡¡construction£»¡¡the¡¡experimenter
finds¡¡himself¡¡wrapt¡¡in¡¡doubt¡¡and¡¡perplexity¡£
But¡¡birds¡¡do¡¡fly£»¡¡notwithstanding¡¡this¡¡wonderful
array¡¡of¡¡contradictory¡¡exhibitions¡£¡¡Observation
has¡¡not¡¡enabled¡¡us¡¡to¡¡learn¡¡why¡¡these¡¡things
are¡¡so¡£¡¡High¡¡authorities£»¡¡and¡¡men¡¡who¡¡are¡¡expert
aviators£»¡¡tell¡¡us¡¡that¡¡the¡¡bird¡¡flies¡¡because
it¡¡is¡¡able¡¡to¡¡pick¡¡out¡¡ascending¡¡air¡¡currents¡£
THEORIES¡¡ABOUT¡¡FLIGHT¡¡OF¡¡BIRDS¡£Then¡¡we
are¡¡offered¡¡the¡¡theory¡¡that¡¡the¡¡bird¡¡has¡¡an¡¡instinct
which¡¡tells¡¡it¡¡just¡¡how¡¡to¡¡balance¡¡in¡¡the
air¡¡when¡¡its¡¡wings¡¡are¡¡once¡¡set¡¡in¡¡motion¡£
Frequently£»¡¡what¡¡is¡¡taken¡¡for¡¡instinct£»¡¡is¡¡something
entirely¡¡different¡£
It¡¡has¡¡been¡¡assumed£»¡¡for¡¡instance£»¡¡that¡¡a¡¡cyclist
making¡¡a¡¡turn¡¡at¡¡a¡¡rapid¡¡speed£»¡¡and¡¡a¡¡bird¡¡flying
around¡¡a¡¡circle¡¡will¡¡throw¡¡the¡¡upper¡¡part¡¡of¡¡the
body¡¡inwardly¡¡to¡¡counteract¡¡the¡¡centrifugal¡¡force
which¡¡tends¡¡to¡¡throw¡¡it¡¡outwardly¡£
Experiments¡¡with¡¡the¡¡monorail¡¡car£»¡¡which¡¡is
equipped¡¡with¡¡a¡¡gyroscope¡¡to¡¡hold¡¡it¡¡in¡¡a¡¡vertical
position£»¡¡show¡¡that¡¡when¡¡the¡¡car¡¡approaches¡¡a
curve¡¡the¡¡car¡¡will¡¡lean¡¡inwardly£»¡¡exactly¡¡the¡¡same
as¡¡a¡¡bird£»¡¡or¡¡a¡¡cyclist£»¡¡and¡¡when¡¡a¡¡straight¡¡stretch
is¡¡reached£»¡¡it¡¡will¡¡again¡¡straighten¡¡up¡£
INSTINCT¡£Now£»¡¡either¡¡the¡¡car£»¡¡so¡¡equipped
possesses¡¡instinct£»¡¡or¡¡there¡¡must¡¡be¡¡a¡¡principle
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of¡¡action¡£
In¡¡like¡¡manner¡¡there¡¡must¡¡be¡¡some¡¡principle
that¡¡is¡¡entirely¡¡independent¡¡of¡¡the¡¡form¡¡of¡¡matter£»
or¡¡its¡¡arrangement£»¡¡which¡¡enables¡¡the¡¡bird
to¡¡perform¡¡its¡¡evolutions¡£¡¡We¡¡are¡¡led¡¡to¡¡believe
from¡¡all¡¡the¡¡foregoing¡¡considerations¡¡that¡¡it¡¡is
the¡¡manner¡¡or¡¡the¡¡form¡¡of¡¡the¡¡motion¡£
MODE¡¡OF¡¡MOTION¡£In¡¡this¡¡respect¡¡it¡¡seems¡¡to
be¡¡comparable¡¡in¡¡every¡¡respect¡¡to¡¡the¡¡great¡¡and
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Thus£»¡¡light£»¡¡heat¡¡and¡¡electricity¡¡are¡¡the¡¡same£»¡¡the
manifestations¡¡being¡¡unlike¡¡only¡¡because¡¡they
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Everything¡¡in¡¡nature¡¡manifests¡¡itself¡¡by¡¡motion¡£
It¡¡is¡¡the¡¡only¡¡way¡¡in¡¡which¡¡nature¡¡acts¡£
Every¡¡transformation¡¡from¡¡one¡¡thing¡¡to¡¡another£»
is¡¡by¡¡way¡¡of¡¡a¡¡movement¡¡which¡¡is¡¡characteristic
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Why£»¡¡then£»¡¡should¡¡this¡¡great¡¡mystery¡¡of¡¡nature£»
act¡¡unlike¡¡the¡¡other¡¡portions¡¡of¡¡which¡¡it¡¡is
a¡¡part£¿
THE¡¡WING¡¡STRUCTURE¡£The¡¡wing¡¡structure¡¡of
every¡¡flying¡¡creature¡¡that¡¡man¡¡has¡¡examined£»¡¡has
one¡¡universal¡¡point¡¡of¡¡similarity£»¡¡and¡¡that¡¡is¡¡the
manner¡¡of¡¡its¡¡connection¡¡with¡¡the¡¡body¡£¡¡It¡¡is¡¡a
sort¡¡of¡¡universal¡¡joint£»¡¡which¡¡permits¡¡the¡¡wing
to¡¡swing¡¡up¡¡and¡¡down£»¡¡perform¡¡a¡¡gyratory¡¡movement
while¡¡doing¡¡so£»¡¡and¡¡folds¡¡to¡¡the¡¡rear¡¡when
at¡¡rest¡£
Some¡¡have¡¡these¡¡movements¡¡in¡¡a¡¡greater¡¡or
less¡¡degree£»¡¡or¡¡capable¡¡of¡¡a¡¡greater¡¡range£»¡¡but
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When¡¡the¡¡stroke¡¡of¡¡the¡¡wing¡¡is¡¡downwardly¡¡the
rear¡¡margin¡¡is¡¡higher¡¡than¡¡the¡¡front¡¡edge£»¡¡so
that¡¡the¡¡downward¡¡beat¡¡not¡¡only¡¡raises¡¡the¡¡body
upwardly£»¡¡but¡¡also¡¡propels¡¡it¡¡forwardly¡£
THE¡¡WING¡¡MOVEMENT¡£The¡¡moment¡¡the¡¡wing
starts¡¡to¡¡swing¡¡upwardly¡¡the¡¡rear¡¡end¡¡is
depressed£»¡¡and¡¡now£»¡¡as¡¡the¡¡bird¡¡is¡¡moving¡¡forwardly£»
the¡¡wing¡¡surface¡¡has¡¡a¡¡positive¡¡angle¡¡of
incidence£»¡¡and¡¡as¡¡the¡¡wing¡¡rises¡¡while¡¡the¡¡forward
motion¡¡is¡¡taking¡¡place£»¡¡there¡¡is¡¡no¡¡resistance
which¡¡is¡¡effective¡¡enough¡¡to¡¡counteract¡¡the
momentum¡¡which¡¡has¡¡been¡¡set¡¡up¡£
The¡¡great¡¡problem¡¡is¡¡to¡¡put¡¡this¡¡motion¡¡into¡¡a
mechanical¡¡form¡£¡¡The¡¡trouble¡¡is¡¡not¡¡ascribable
to¡¡the¡¡inability¡¡of¡¡the¡¡mechanic¡¡to¡¡describe¡¡this
movement¡£¡¡It¡¡is¡¡an¡¡exceedingly¡¡simple¡¡one¡£
The¡¡first¡¡difficulty¡¡is¡¡in¡¡the¡¡material¡¡that¡¡must
be¡¡used¡£¡¡Lightness¡¡and¡¡strength¡¡for¡¡the¡¡wing
itself¡¡are¡¡the¡¡first¡¡requirements¡£¡¡Then¡¡rigidity
in¡¡the¡¡joint¡¡and¡¡in¡¡the¡¡main¡¡rib¡¡of¡¡the¡¡wing£»¡¡are
the¡¡next¡¡considerations¡£
In¡¡these¡¡respects¡¡the¡¡ability¡¡of¡¡man¡¡is¡¡limited¡£
The¡¡wing¡¡ligatures¡¡of¡¡flying¡¡creatures¡¡is¡¡exceedingly
strong£»¡¡and¡¡flexible£»¡¡the¡¡hollow¡¡bone¡¡formation
and¡¡the¡¡feathers¡¡are¡¡extremely¡¡light£»¡¡compared
with¡¡their¡¡sustaining¡¡powers¡£
THE¡¡HELICOPTER¡¡MOTION¡£The¡¡helicopter£»¡¡or
helix¡wing£»¡¡is¡¡a¡¡form¡¡of¡¡flying¡¡machine¡¡which¡¡depends
on¡¡revolving¡¡screws¡¡to¡¡maintain¡¡it¡¡in¡¡the
air¡£¡¡Many¡¡propellers¡¡are¡¡now¡¡made£»¡¡six¡¡feet¡¡in
length£»¡¡which¡¡have¡¡a¡¡pull¡¡of¡¡from¡¡400¡¡to¡¡500
pounds¡£¡¡If¡¡these¡¡are¡¡placed¡¡on¡¡vertically¡disposed
shafts¡¡they¡¡would¡¡exert¡¡a¡¡like¡¡power¡¡to
raise¡¡a¡¡machine¡¡from¡¡the¡¡earth¡£
Obviously£»¡¡it¡¡is¡¡difficult¡¡to¡¡equip¡¡such¡¡a¡¡machine
with¡¡planes¡¡for¡¡sustaining¡¡it¡¡in¡¡flight£»¡¡after¡¡it¡¡is
once¡¡in¡¡the¡¡air£»¡¡and¡¡unless¡¡such¡¡means¡¡are¡¡provided
the¡¡propellers¡¡themselves¡¡must¡¡be¡¡the
mechanism¡¡to¡¡propel¡¡it¡¡horizontally¡£
This¡¡means¡¡a¡¡change¡¡of¡¡direction¡¡of¡¡the¡¡shafts
which¡¡support¡¡the¡¡propellers£»¡¡and¡¡the¡¡construction
is¡¡necessarily¡¡more¡¡complicated¡¡than¡¡if¡¡they
were¡¡held¡¡within¡¡non¡changeable¡¡bearings¡£
This¡¡principle£»¡¡however£»¡¡affords¡¡a¡¡safer¡¡means
of¡¡navigating¡¡than¡¡the¡¡orthopter¡¡type£»¡¡because
the¡¡blades¡¡of¡¡such¡¡an¡¡instrument¡¡can¡¡be¡¡forced
through¡¡the¡¡air¡¡with¡¡infinitely¡¡greater¡¡speed¡¡than
beating¡¡wings£»¡¡and¡¡it¡¡devolves¡¡on¡¡the¡¡inventor¡¡to
devise¡¡some¡¡form¡¡of¡¡apparatus¡¡which¡¡will¡¡permit
the¡¡change¡¡of¡¡pull¡¡from¡¡a¡¡vertical¡¡to¡¡a¡¡horizontal
direction¡¡while¡¡in¡¡flight¡£
CHAPTER¡¡VI
THE¡¡LIFTING¡¡SURFACES¡¡OF¡¡AEROPLANES
THIS¡¡subject¡¡includes¡¡the¡¡form£»¡¡shape¡¡and¡¡angle
of¡¡planes£»¡¡used¡¡in¡¡flight¡£¡¡It¡¡is¡¡the¡¡direction¡¡in
which¡¡most¡¡of¡¡the¡¡energy¡¡has¡¡been¡¡expended¡¡in
developing¡¡machines£»¡¡and¡¡the¡¡true¡¡form¡¡is¡¡still
involved¡¡in¡¡doubt¡¡and¡¡uncertainty¡£
RELATIVE¡¡SPEED¡¡AND¡¡ANGLE¡£The¡¡relative
speed¡¡and¡¡angle£»¡¡and¡¡the¡¡camber£»¡¡or¡¡the¡¡curved
formation¡¡of¡¡the¡¡plane£»¡¡have¡¡been¡¡considered¡¡in
all¡¡their¡¡aspects£»¡¡so¡¡t
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