60
DOC.
86
FEBRUARY
1908
This
drawing
is
lousy
see
the other
one
on
the enclosed
sheet
Now,
I
don't
like
the horizontal
propeller,
and
I
had
the
following
idea.
Imagine
that
one
is
high up,
then
one
sets
both
propellers
somewhat
aslant,
turns
off
the
motor
and brakes the
propellers
tightly;
we can
thus
view
the
propellers
as
slanted
surfaces.
The
thing
will
now
start
to
glide
and
acquire
a
quite
respectable
speed.
(The
slanting
is produced,
for
example,
by
the
person's
moving
from the
rear
toward the
front.)
To take
advantage
of
the
swing,
one
may change
the
position
of the
surfaces,
and
then
one
will
ascend
for
a
stretch.
Imagine
that
one now
turns
on
the
motor
again,
then
I ask
myself
will
this
forward
motion
now
continue
upwards?
one
could
think
so.
(Of
course,
one
has
to
imagine
that the
motor is
so powerful
that the machine
will ascend
when it
is
in
the horizontal
position.)
How do
you
think
the
thing
behaves?
This
is
the 2d
important point
of
the
problem,
because
to be able
to
dispense
with
a
propeller-a
propeller
that,
in
addition,
would have
to
run
at
different velocities-means
to
save
weight,
room,
and
power;
indeed,
I believe
that
this
is
a
vital
question
for this machine. But
let's
hope
that
this
slanting
of the
surfaces does work
out,
and
then
we
have
augmented
and
improved upon
the
way
birds
fly.
I would
consider
such
a
machine
as completely
safe. I have
done
a
little bit
of
constructing
and
calculating,
and the
thing
promises to
come
along very
well.
Now
I
come
to
still
another
matter
of the
greatest importance,
namely,
the
use
of
ribs with
ship
propellers.
Ship
propellers
cannot
run
faster than
a
maximum
of
200
revolutions,
for
otherwise
the
efficiency
drops too
much. This
is
the factor that hinders
the
immediate introduc-
tion
of
steam turbines, because if
one
has
to
build steam
turbines
making
200
revolutions/min,
which in fact
happens,
then
they
also
become
expensive
and
heavy.
If
one
could
increase
the
efficiency by applying
such
ribs,
and this
seems
to
me
certain,
so
that
e.g.
500
revolutions
would be
permitted,
then
an
extraordinary
gain
would be
achieved.
What
do
you
think? Should
I
take
out
a
patent immediately?
Or
publish
without
a
patent
or
start
negotiations
without
a
patent?
Or be
annoyed
if
someone
else
brings
the
thing
out
5
years
from now?
Now
one more
drawing
of the
flying
machine.
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