''
``Yes,'' said the Dihedral Angle, ``that's what would
happen if they would only make me large enough; but
they won't do it because it would too greatly decrease the
horizontal equivalent, and therefore the Lift, and incidentally
it would, as Aeroplanes are built to-day, produce
an excess of Keel Surface above the turning axis, and that
in itself would spoil the Lateral Stability. The Keel Surface
should be equally divided above and below the longitudinal
turning axis (upon which the Aeroplane rolls sideways),
or the side upon which there is an excess will get
blown over by the gusts. It strikes me that my future
isn't very promising, and about my only chance is when
the Junior Draughtsman makes a mistake, as he did the
other day. And just think of it, they call him a Designer
now that he's got a job at the Factory! What did he do?
Why, he calculated the weights wrong and got the Centre
of Gravity too high, and they didn't discover it until the
machine was built. Then all they could do was to give
me a larger Angle. That dropped the bottom of the V
lower down, and as that's the centre of the machine, where
all the Weight is, of course that put the Centre of Gravity
in its right place. But now there is too much Keel Surface
above, and the whole thing's a Bad Compromise, not at all
like Our Efficiency.''
And Efficiency, blushing very prettily at the compliment,
then asked, ``And how does the Centre of Gravity affect
matters?''
``That's easy,'' said Grandfather Gravity.
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