flying machines-第26节
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attracted little attention because the exact data and the
maneuvers required were not known and the feat had
not yet been performed by a man。 The puzzle has always
been to account for the observed act in very light
winds； and it is hoped that by the present selection of
the most difficult case to explaini。 e。； the soaring in a
dead horizontal calmsomebody will attempt the exploit。
Requisites for Soaring Flights。
The following are deemed to be the requisites and
maneuvers to master the secrets of soaring flight：
1stDevelop a dynamic flying machine weighing
about one pound per square foot of area； with stable
equilibrium and under perfect control； capable of gliding
by gravity at angles of one in ten （5 3/4 degrees） in still air。
2nd。Select locations where soaring birds abound and
occasions where rising trends of gentle winds are frequent
and to be relied on。
3rd。Obtain an initial velocity of at least 25 feet per
second before attempting to soar。
4th。So locate the center of gravity that the apparatus
shall assume a negative angle； fore and aft； of about 3 degrees。
Calculations show； however； that sufficient propelling
force may still exist at 0 degrees； but disappears entirely at
＋4 degrees。
5th。Circle like the bird。 Simultaneously with the
steering； incline the apparatus to the side toward which
it is desired to turn； so that the centrifugal force shall
be balanced by the centripetal force。 The amount of the
required inclination depends upon the speed and on the
radius of the circle swept over。
6th。Rise spirally like the bird。 Steer with the
horizontal rudder； so as to descend slightly when going
with the wind and to ascend when going against the
wind。 The bird circles over one spot because the rising
trends of wind are generally confined to small areas or
local chimneys； as pointed out by Sir H。 Maxim and
others。
7th。Once altitude is gained； progress may be made
in any direction by gliding downward by gravity。
The bird's flying apparatus and skill are as yet infinitely
superior to those of man； but there are indications that
within a few years the latter may evolve more accurately
proportioned apparatus and obtain absolute control over
it。
It is hoped； therefore； that if there be found no radical
error in the above computations； they will carry the conviction
that soaring flight is not inaccessible to man； as
it promises great economies of motive power in favorable
localities of rising winds。
The writer will be grateful to experts who may point
out any mistake committed in data or calculations； and
will furnish additional information to any aviator who
may wish to attempt the feat of soaring。
CHAPTER XXI。
FLYING MACHINES VS。 BALLOONS。
While wonderful success has attended the development
of the dirigible （steerable） balloon the most ardent
advocates of this form of aerial navigation admit that it
has serious drawbacks。 Some of these may be described
as follows：
Expense and Other Items。
Great Initial Expense。The modern dirigible balloon
costs a fortune。 The Zeppelin； for instance； costs more
than 100；000 （these are official figures）。
Expense of Inflation。Gas evaporates rapidly； and a
balloon must be re…inflated； or partially re…inflated； every
time it is used。 The Zeppelin holds 460；000 cubic feet
of gas which； even at 1 per thousand； would cost 460。
Difficulty of Obtaining Gas。If a balloon suddenly
becomes deflated； by accident or atmospheric conditions；
far from a source of gas supply； it is practically worthless。
Gas must be piped to it； or the balloon carted to
the gas housean expensive proceeding in either event。
Lack of Speed and Control。
Lack of Speed。Under the most favorable conditions
the maximum speed of a balloon is 30 miles an hour。
Its great bulk makes the high speed attained by flying
machines impossible。
Difficulty of Control。While the modern dirigible balloon is
readily handled in calm or light winds； its bulk
makes it difficult to control in heavy winds。
The Element of Danger。Numerous balloons have
been destroyed by lightning and similar causes。 One of
the largest of the Zeppelins was thus lost at Stuttgart
in 1908。
Some Balloon Performances。
It is only a matter of fairness to state that； under
favorable conditions； some very creditable records have
been made with modern balloons； viz：
November 23d； 1907； the French dirigible Patrie； travelled
187 miles in 6 hours and 45 minutes against a
light wind。 This was a little over 28 miles an hour。
The Clement…Bayard； another French machine； sold
to the Russian government； made a trip of 125 miles at
a rate of 27 miles an hour。
Zeppelin No。 3； carrying eight passengers； and having
a total lifting capacity of 5；500 pounds of ballast in
addition to passengers； weight of equipment； etc。； was
tested in October； 1906； and made 67 miles in 2 hours
and 17 minutes； about 30 miles an hour。
These are the best balloon trips on record； and show
forcefully the limitations of speed； the greatest being not
over 30 miles an hour。
Speed of Flying Machines。
Opposed to the balloon performances we have flying
machine trips （of authentic records） as follows：
Bleriotmonoplanein 190852 miles an hour。
DelagrangeJune 22； 190810 1/2 miles in 16 minutes；
approximately 42 miles an hour。
WrightsOctober； 1905the machine was then in its
infancy24 miles in 38 minutes； approximately 44 miles
an hour。 On December 31； 1908； the Wrights made 77
miles in 2 hours and 20 minutes。
Lambert； a pupil of the Wrights； and using a Wright
biplane； on October 18； 1909； covered 29。82 miles in 49
minutes and 39 seconds； being at the rate of 36 miles
an hour。 This flight was made at a height of 1；312 feet。
LathamOctober 21； 1909made a short flight； about
11 minutes； in the teeth of a 40 mile gale； at Blackpool；
Eng。 He used an Antoniette monoplane； and the official
report says： 〃This exhibition of nerve； daring and ability
is unparalled in the history of aviation。〃
FarmanOctober 20； 1909was in the air for 1 hour；
32 min。； 16 seconds； travelling 47 miles； 1；184 yards； a
duration record for England。
PaulhanJanuary 18； 190147 1/2 miles at the rate of
45 miles an hour； maintaining an altitude of from 1；000
to 2；000 feet。
Expense of Producing Gas。
Gas is indispensable in the operation of dirigible balloons；
and gas is expensive。 Besides this it is not always
possible to obtain it in sufficient quantities even in large
cities； as the supply on hand is generally needed for
regular customers。 Such as can be had is either water
or coal gas； neither of which is as efficient in lifting
power as hydrogen。
Hydrogen is the lightest and consequently the most
buoyant of all known gases。 It is secured commercially
by treating zinc or iron with dilute sulphuric or
hydrochloric acid。 The average cost may be safely placed
at 10 per 1；000 feet so that； to inflate a balloon of the
size of the Zeppelin； holding 460；000 cubic feet； would
cost 4；600。
Proportions of Materials Required。
In making hydrogen gas it is customary to allow 20
per cent for loss between the generation and the introduction
of the gas into the balloon。 Thus； while the
formula calls for iron 28 times heavier than the weight
of the hydrogen required； and acid 49 times heavier； the
real quantities are 20 per cent greater。 Hydrogen weighs
about 0。09 ounce to the cubic foot。 Consequently if we
need say 450；000 cubic feet of gas we must have 2；531。25
pounds in weight。 To produce this； allowing for the 20
percent loss； we must have 35 times its weight in iron；
or over 44 tons。 Of acid it would take 60 times the
weight of the gas； or nearly 76 tons。
In Time of Emergency。
These figures are appalling； and under ordinary conditions
would be prohibitive； but there are times when
the balloon operator； unable to obtain water or coal gas；
must foot the bills。 In military maneuvers； where the
field of operation is fixed； it is possible to furnish supplies
of hydrogen gas in portable cylinders； but on long
trips where sudden leakage or other cause makes descent
in an unexpected spot unavoidable； it becomes a question
of making your own hydrogen gas or deserting the balloon。
And when this occurs the balloonist is up against
another serious propositioncan he find the necessary
zinc or iron？ Can he get the acid？
Balloons for Commercial Use。
Despite all this the balloon has its uses。 If there is to
be such a thing as aerial navigation in a commercial
waythe carrying of freight and passengersit will
come through the employment of such monster balloons
as Count Zeppelin is building。 But even then the carrying
capacity must of necessity be limited。 The latest
Zeppelin creation； a monster
