Let A, E, B, F be an open frame, A-B a wire stretched diagonally from corner to corner, and G a ring running upon the wire. C-D, another wire, reaches from end to end of the frame, passing also through the ring G at the intersection of the wires. This second wire (C-D) is movable back and forth between A-F and E-B, and parallel to them. It is evident that when C-D is moved the ring G will slide along both wires, and that while C-D is passing from A-F to E-B, G will slide from A to B—twice as far, that is, as the distance traversed by C-D, the moving agent.
SAIL PLAN OF A MODERN ICE-YACHT.
Now, suppose G to be an ice-yacht; let the movement of C-D across the frame represent the direction and velocity of the wind and the diagonal A-B the distance to be traversed. The ice-yacht G moves twice as far, that is to say, twice as fast as does C-D (the wind) that drives it. Such is, perhaps, as plain a statement of the conditions as can be devised. In practice the elements become more complicated. Let Fig. 3 represent a section of frozen river, with the wind blowing across it in the direction indicated by the arrows. Applying the principle shown in Fig. 2, an ice-yacht may run from A to B while the wind is moving across the river from A-F to E-B. It is not the purpose of this paper to go into the logistics of sailing in general, but any one who can sail a boat will see at a glance, that with the wind as shown in Fig. 3, an ordinary boat would sail nearly or quite as fast from C to D, or from E to F, as she would from A to B. The same rules apply, of course, to an ice-yacht, but with this important difference, while an ordinary sailing-boat meets with increasing resistance from the water the faster she goes through it, an ice-yacht meets less and less frictional resistance from the ice the faster she goes over it. Again, if she is pointing more or less toward the wind (as on a line from E to F), she increases the apparent force of the wind by her own motion. The only considerable resistance is that offered by spars, rigging, etc., in passing through the air, and this is trifling when compared with her large sail area, and the propulsive energy of even a moderate breeze.
FIG. 3.—THE SAILING PARADOX IN PRACTICE.
In sailing an ice-yacht there is none of the vexatious handling of ropes unavoidable in an ordinary sailing-boat. The sheets usually take care of themselves in going about, and the steersman has only to move his tiller a little to starboard or port to secure instant obedience and an eagle-like swoop of the yacht in the desired direction. In high winds, however, the yacht is apt to lift her weather runner clear of the ice, upon which she at once becomes unmanageable and must be brought down to her bearings as soon as possible. If properly balanced she should shortly do this of her own accord, but during the few seconds when she has the bit between her teeth she may do untold mischief.
The astonishing rapidity with which an ice-yacht under control may be handled was well instanced last winter in an encounter between the Polaris and Arrow, as indicated in the diagram, Fig. 4. The Polaris was running dead before the wind, heading to pass a space of open water where ice-cutters were at work, when her steersman became aware of the Arrow approaching on his starboard hand at a fearful rate of speed, but with her weather runner in the air, and evidently with the bit between her teeth. A collision was imminent, for the Polaris could not bear away in either direction; on one side was open water and on the other was the Arrow, too near to be passed astern. Under the circumstances it was instinct rather than a process of reasoning that led Commodore Roosevelt to jam his helm hard a-starboard and send the Polaris spinning on her center, making a complete revolution almost within her own length (see Fig. 4). She did it, and was on her former course again almost before any one knew what had happened, her jib-boom barely clearing the after leach of the Arrow’s mainsail as she passed astern of her. Such a gyration as this is justifiable only in extreme cases, for of course everything is subjected to a sudden and tremendous strain, and if nothing gives way it speaks well for the perfection of equipment.
Sometimes an ice-yacht will perform this maneuver on her own responsibility and without an instant’s warning, and this is especially true of the smaller class of lateen-rigged boats. With them, however, damage is less likely to result, as the strains are proportionately less severe.
Sailing on the wind is a comparatively simple matter, though, of course, where a number of boats are breaking tacks, as in a thrash to windward on a regatta day, a quick eye and a steady hand are indispensable if collisions are to be avoided and the most made of every turn.