Whether the ski then runs on in the direction in which it is pointing, or comes to a standstill, of course depends on whether it is pointing downhill or not.
It is obvious, then, that when a ski is in motion across a slope the runner, by means of the side-slip, can make it turn in either direction and to any extent up to a certain limit, and can in this way either come to a standstill, slightly alter his direction, or run straight downhill. It is equally obvious that no matter what means are employed for starting a turn (there are more ways of doing so than I have yet described), the distribution of the runner’s weight on the ski or skis which carry it may make all the difference to the success or failure of the manœuvre.
I have already said that when a ski is running straight downhill it may be made to turn by the runner jerking it somewhat broadside on. He can of course do the same with the two skis, but a simpler plan is for him to stand on one, point the other more or less in the direction in which he wants to go, and hold it so for a moment. It is thus of course made to “stem”—in other words, to side-slip—and, if the runner then throws his weight on to its heel, it can, as we have just seen, be made to turn still further, the previously weighted one being again brought parallel with it as it does so. A turn can also be started from a traverse in the same way.
When one ski is held at an angle with the other in order to start a turn in the above way, the relative position of the two usually produces some steering effect; the two skis in fact act together something like a boat and rudder. To say that one ski may be looked upon as the boat and the other as the rudder is hardly accurate, for the steering effect is at its greatest when, as the runner’s weight is shifted from the ski that is running straight ahead to the one that is held sideways, it rests equally on both; at which moment, since their area is equal, either of the skis may equally well be looked upon as the rudder or as the boat. If, however, it is remembered that the boat steers the rudder no less than the rudder steers the boat, and that if the rudder is fixed in a certain position, it and the boat together may be considered as one solid object whose shape determines whether and how it is able to turn, one may, by comparing the skis with a boat and rudder, understand whether and how, when held in various relative positions, they are able to turn.
The diagram shows the skis as they are held at the beginning of—a, a Telemark, b, a Stemming turn, and c, a Christiania. It also shows a boat turning to the left steered by both a bow and a stern rudder.
Fig. 25.
The darkened ski of each pair is the weighted one.