KRONFELD ON GLIDING AND SOARING.pdf - Lakes Gliding Club

212 KRONFELD ON GLIDING & SOARING
can distinguish between two different methods of obtaining
contact. The original method was to cross from the
slope to the cloud just as the latter was passing directly over
the former. We call this " a hop across " in the direction
of the cloud course, and our best preparation for it is to
climb as high as possible while the cloud is still approaching.
We soar up into the highest layer of air to which we can
attain by means of slope flying, and as we cannot rise higher
and do not sink deeper, we may describe such layers as
" floating layers/' because we neither rise nor sink, but
simply float. Then comes the cloud ; if we keep our
plane more or less over the same position, we suddenly
begin to feel jerking gusts of upward wind, which will lift
us for a short time until we reach a boundary layer between
the sphere of action of the slope and that of the cloud.
Our problem is to slip from the one to the other, and this
can often be done quite easily with vigorous movements.
But often we find it necessary to make skilled use of one
of the gusts by pulling ourselves into it as far as is feasible
and then trying to climb with it. The altimeter shows us
whether we have succeeded, for in that case it begins to
mount steadily. We climb jerkily in sharp upward gusts,
and at last we attain the realm of the clouds. From this
moment we must change our manoeuvres, for it is not
possible to tack in figures of eight as we do above the
slopes.
The upward wind on a slope rises in the form of a more
or less broad stream in front of and above the line of the
hills or mountains. Cloud upwind, however, may be
pictured as rising like a tube beneath the cloud. Its
shape is determined by that of the base of the cloud, which
is generally round, or nearly so. The best figure to describe
is therefore a circle, and so we fly in vast rings under the
clouds. Our movements resemble those of the birds,
which sail upward in the same way but can make use of
smaller upwind tubes because of their own smaller size.
These smaller tubes are usually too insignificant to be used
by our big machines.
There are considerable advantages in this method of
getting into contact with a cloud by passing on with it from