KRONFELD ON GLIDING AND SOARING.pdf - Lakes Gliding Club

286 KRONFELD ON GLIDING & SOARING
to make some contribution to the development of the sailplane
of the future. I worked on the theory that any
marked improvement in efficiency could only be through a
proper wing section in conjunction with a suitable span and
aspect ratio. Careful calculations have shown that an
increase of these results in a decrease of sinking speed, a
better gliding angle, and a greater range between maximum
and minimum flying speed, while at the same time it helps
towards he attainment of greater stability. Such innovations
will greatly increase the chances, on a cross-country
flight, of reaching many up-currents which could not be
reached by sailplanes of another type, and also of soaring
in districts where the up-currents would be too light for
other machines. My latest machine which Dr. Kupper, of
Munich, the designer of the " Kakadu," designed for me
on these principles and which was built by the " Fieseler
Flugzeugbau " at Kassel, should show a thirty per cent,
all-round improvement in flying qualities. This is a
remarkable achievement in view of the fact that the difference
in quality between the other sailplanes at present in
use is practically negligible, even those which show the
best practical results being but little superior to their rivals.
The argument against such an increase in span over the
dimensions which have hitherto been proved feasible is,
of course, that it will inevitably increase the difficulties of
flying. Naturally both the danger of crashes and the
expenses are considerably increased, but all such drawbacks
can be overcome by increased flying efficiency. It is a
mistake to expect only the beginners to learn ; expert pilots
must also train themselves to fly these special machines.
This latest machine of mine, which came out in the spring
of 1930, has a span of 99 ft. The wing has very pointed
tips and a pronounced camber ; it is built in four parts.
The ailerons run the whole length of the wing-surface.
To obviate any possibility of jamming which might be caused
by the great flexibility of this cantilever wing, the ailerons
are divided into six flaps and are operated separately.
Like the rudder and elevators, these are constructed of steel
tubing covered with fabric and hinged on ball-bearings.
The surface of the wing itself is entirely covered over with