DOC.
86
FEBRUARY
1908 59
ribs
here the air that
passes
through
the
rotor
is
forced to
pass
j_
through
the latter.
*
I have it in mind
to
make the
ribs 40
cm high,
and the
blades
20
cm
[high],[3]
thus
a
shock does not
hit the
blades; thus,
for
the
purposes
of
examination it
can
be assumed
that the
pipe is
very long,
with
a
pump
inside.
It
seems
to
me as
though
the needed
output
is
the
same as
before.
(Of
course,
the
external
pressure
on
the
pipe
does not
interest
me.)
How
do
things
stand? This
is
a
question
of the
utmost
importance
because the usefulness
depends
on
it.-
I shall
assume
that the
motor
does
not
need
more
power
to
keep
it
suspended
when the
thing
is
in
motion
than
when
it
stands still.
And
let the
forward
speed
be
36 km/h
=
10
m/sec,
then
in
an example
where
160
kg
are
lifted with
10.5
7
=
20 HP
e,
and
c
=
4.9
m/sec,
the distance
between the
two
propellers must
be only
10
=
6
x
= ~
4.9
x
3
m
for
the
lower
rotor
not
to be
hit
by any
air
whatever
from
the
upper rotor.
This
is
how I
imagine
such
a
flying
machine
6
m
10
m/sec
I-
1
propeller
propellers
rudder
Motor~