flying machines-第7章

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them　exactly　opposite　the　struts。　Screw　the　sockets　into

position　with　wood　screws；　and　then　put　the　eye…bolts　in

place。　Repeat　the　operation　on　the　rear　frame。　Next

put　the　sockets　for　the　upper　plane　frame　in　place。



You　are　now　ready　to　bring　the　two　planes　together。

Begin　by　inserting　the　stanchions　in　the　sockets　in　the

lower　plane。　The　ends　may　need　a　little　rubbing　with

sandpaper　to　get　them　into　the　sockets；　but　care　must

be　taken　to　have　them　fit　snugly。　When　all　the　stanchions

are　in　place　on　the　lower　plane；　lift　the　upper

plane　into　position；　and　fit　the　sockets　over　the　upper

ends　of　the　stanchions。



Trussing　with　Guy　Wires。



The　next　move　is　to　〃tie〃　the　frame　together　rigidly

by　the　aid　of　guy　wires。　This　is　where　the　No。　12　piano

wire　comes　in。　Each　rectangle　formed　by　the　struts　and

stanchions　with　the　exception　of　the　small　center　one；

is　to　be　wired　separately　as　shown　in　the　illustration。

At　each　of　the　eight　corners　forming　the　rectangle　the

ring　of　one　of　the　eye…bolts　will　be　found。　There　are

two　ways　of　doing　this　〃tieing；〃　or　trussing。　One　is　to

run　the　wires　diagonally　from　eye…bolt　to　eye…bolt；　depending

upon　main　strength　to　pull　them　taut　enough；

and　then　twist　the　ends　so　as　to　hold。　The　other　is　to

first　make　a　loop　of　wire　at　each　eye…bolt；　and　connect

these　loops　to　the　main　wires　with　turn…buckles。　This

latter　method　is　the　best；　as　it　admits　of　the　tension　being

regulated　by　simply　turning　the　buckle　so　as　to　draw

the　ends　of　the　wire　closer　together。　A　glance　at　the

illustration　will　make　this　plain；　and　also　show　how　the

wires　are　to　be　placed。　The　proper　degree　of　tension

may　be　determined　in　the　following　manner：



After　the　frame　is　wired　place　each　end　on　a　saw…horse

so　as　to　lift　the　entire　frame　clear　of　the　work…shop

floor。　Get　under　it；　in　the　center　rectangle　and；　grasping

the　center　struts；　one　in　each　hand；　put　your　entire

weight　on　the　structure。　If　it　is　properly　put　together

it　will　remain　rigid　and　unyielding。　Should　it　sag　ever

so　slightly　the　tension　of　the　wires　must　be　increased

until　any　tendency　to　sag；　no　matter　how　slight　it　may

be；　is　overcome。



Putting　on　the　Cloth。



We　are　now　ready　to　put　on　the　cloth　covering　which

holds　the　air　and　makes　the　machine　buoyant。　The　kind

of　material　employed　is　of　small　account　so　long　as　it　is

light；　strong；　and　wind…proof；　or　nearly　so。　Some　aviators

use　what　is　called　rubberized　silk；　others　prefer

balloon　cloth。　Ordinary　muslin　of　good　quality；　treated

with　a　coat　of　light　varnish　after　it　is　in　place；　will　answer

all　the　purposes　of　the　amateur。



Cut　the　cloth　into　strips　a　little　over　4　feet　in　length。

As　you　have　20　feet　in　width　to　cover；　and　the　cloth　is

one　yard　wide；　you　will　need　seven　strips　for　each　plane；

so　as　to　allow　for　laps；　etc。　This　will　give　you　fourteen

strips。　Glue　the　end　of　each　strip　around　the　front

horizontal　beams　of　the　planes；　and　draw　each　strip　back；

over　the　ribs；　tacking　the　edges　to　the　ribs　as　you　go

along；　with　small　copper　or　brass　tacks。　In　doing　this

keep　the　cloth　smooth　and　stretched　tight。　Tacks　should

also　be　used　in　addition　to　the　glue；　to　hold　the　cloth　to

the　horizontal　beams。



Next；　give　the　cloth　a　coat　of　varnish　on　the　clear；　or

upper　side；　and　when　this　is　dry　your　glider　will　be

ready　for　use。



Reinforcing　the　Cloth。



While　not　absolutely　necessary　for　amateur　purposes；

reinforcement　of　the　cloth；　so　as　to　avoid　any　tendency

to　split　or　tear　out　from　wind…pressure；　is　desirable。　One

way　of　doing　this　is　to　tack　narrow　strips　of　some

heavier　material；　like　felt；　over　the　cloth　where　it　laps

on　the　ribs。　Another　is　to　sew　slips　or　pockets　in　the

cloth　itself　and　let　the　ribs　run　through　them。　Still　another

method　is　to　sew　2…inch　strips　（of　the　same　material

as　the　cover）　on　the　cloth；　placing　them　about　one

yard　apart；　but　having　them　come　in　the　center　of　each

piece　of　covering；　and　not　on　the　laps　where　the　various

pieces　are　joined。



Use　of　Armpieces。



Should　armpieces　be　desired；　aside　from　those　afforded

by　the　center　struts；　take　two　pieces　of　spruce；　3　feet

long；　by　1　x　1　3/4　inches；　and　bolt　them　to　the　front　and

rear　beams　of　the　lower　plane　about　14　inches　apart。

These　will　be　more　comfortable　than　using　the　struts；

as　the　operator　will　not　have　to　spread　his　arms　so

much。　In　using　the　struts　the　operator；　as　a　rule；　takes

hold　of　them　with　his　hands；　while　with　the　armpieces；

as　the　name　implies；　he　places　his　arms　over　them；　one

of　the　strips　coming　under　each　armpit。



Frequently　somebody　asks　why　the　ribs　should　be

curved。　The　answer　is　easy。　The　curvature　tends　to

direct　the　air　downward　toward　the　rear　and；　as　the　air

is　thus　forced　downward；　there　is　more　or　less　of　an　impact

which　assists　in　propelling　the　aeroplane　upwards。







CHAPTER　VI。



LEARNING　TO　FLY。



Don't　be　too　ambitious　at　the　start。　Go　slow；　and

avoid　unnecessary　risks。　At　its　best　there　is　an　element

of　danger　in　aviation　which　cannot　be　entirely　eliminated；　but　it

may　be　greatly　reduced　and　minimized　by

the　use　of　common　sense。



Theoretically；　the　proper　way　to　begin　a　glide　is　from

the　top　of　an　incline；　facing　against　the　wind；　so　that

the　machine　will　soar　until　the　attraction　of　gravitation

draws　it　gradually　to　the　ground。　This　is　the　manner　in

which　experienced　aviators　operate；　but　it　must　be　kept

in　mind　that　these　men　are　experts。　They　understand

air　currents；　know　how　to　control　the　action　and　direction

of　their　machines　by　shifting　the　position　of　their

bodies；　and　by　so　doing　avoid　accidents　which　would　be

unavoidable　by　a　novice。



Begin　on　Level　Ground。



Make　your　first　flights　on　level　ground；　having　a　couple

of　men　to　assist　you　in　getting　the　apparatus　under

headway。　Take　your　position　in　the　center　rectangle；

back　far　enough　to　give　the　forward　edges　of　the　glider

an　inclination　to　tilt　upward　very　slightly。　Now　start

and　run　forward　at　a　moderately　rapid　gait；　one　man　at

each　end　of　the　glider　assisting　you。　As　the　glider　cuts

into　the　air　the　wind　will　catch　under　the　uplifted　edges

of　the　curved　planes；　and　buoy　it　up　so　that　it　will　rise

in　the　air　and　take　you　with　it。　This　rise　will　not　be

great；　just　enough　to　keep　you　well　clear　of　the　ground。

Now　project　your　legs　a　little　to　the　front　so　as　to　shift

the　center　of　gravity　a　trifle　and　bring　the　edges　of　the

glider　on　an　exact　level　with　the　atmosphere。　This；　with

the　momentum　acquired　in　the　start；　will　keep　the　machine

moving　forward　for　some　distance。



Effect　of　Body　Movements。



When　the　weight　of　the　body　is　slightly　back　of　the

center　of　gravity　the　edges　of　the　advancing　planes　are

tilted　slightly　upward。　The　glider　in　this　position　acts

as　a　scoop；　taking　in　the　air　which；　in　turn；　lifts　it　off　the

ground。　When　a　certain　altitude　is　reachedthis　varies

with　the　force　of　the　windthe　tendency　to　a　forward

movement　is　lost　and　the　glider　comes　to　the　ground。

It　is　to　prolong　the　forward　movement　as　much　as　possible

that　the　operator　shifts　the　center　of　gravity　slightly；

bringing　the　apparatus　on　an　even　keel　as　it　were　by

lowering　the　advancing　edges。　This　done；　so　long　as

there　is　momentum　enough　to　keep　the　glider　moving；　it

will　remain　afloat。



If　you　shift　your　body　well　forward　it　will　bring　the

front　edges　of　the　glider　down；　and　elevate　the　rear　ones。

In　this　way　the　air　will　be　〃spilled〃　out　at　the　rear；　and；

having　lost　the　air　support　or　buoyancy；　the　glider　comes

down　to　the　ground。　A　few　flights　will　make　any　ordinary

man　proficient　in　the　control　of　his　apparatus　by　his

body　movements；　not　only　as　concerns　the　elevating　and

depressing　of　the　advancing　edges；　but　also　actual　steering。　You

will　quickly　learn；　for　instance；　that；　as　the

shifting　of　the　bodily　weight　backwards　and　forwards

affects　the