windward, and leave only just enough, so that by setting the sails in the way shown later, a model yacht steers itself perfectly. Great care must be taken not to overdo it, otherwise the vessel will run off the wind, and not steer herself at all. The part which the increased depth of keel aft plays in steering a model yacht is this; as the sails are very evenly balanced, and exert little more force at the stern than at the bow when the vessel is upright in the water; yet even then there is always the tendency more or less to come up in the wind, and as the bow is not so deep as the stern, the lateral pressure of all the sails forces the vessel sideways (called leeway),— she makes more leeway forward than aft, and thus this particular arrangement helps to make her steer herself. Necessarily, when the wind blows strongly it is of very great use, and enables increased length of bowsprit to be dispensed with: too long a bowsprit is a great drawback, it dips in the water, and is difficult to fasten firmly. Again, a model vessel being well up by the stem, and deep aft, possesses another power of self-steering, viz. when the wind presses her down forward (when on the wind), it lightens her aft; this, of course, permits her to gripe more to windward, as she holds more water forward and less aft, but if she comes up too much, so as to relieve the mainsail of a great part of its pressure, the opposite action results, the bow is lightened and the stern depressed exactly in proportion, so that under all circumstances the vessel possesses a self-acting power to steer herself. Now, as just shown, a model yacht, partly by the action of the sails (particularly the mainsail), and partly by the action of the lee bow, will always keep close to the wind,-in fact, too close; therefore, to make her steer herself, the jib and foresail are kept in a little closer (i. e. more in a parallel line with the keel) than the mainsail. So if the vessel comes too close to the wind, first the outer leach of the mainsail loses power and shakes, and if this does not suffice, as it its should, to make her fall off again, the whole mainsail will shake, and as the jib and foresail must keep full, the ship pays off till the mainsail fills again. So an equilibrium is attained, and in a steady wind, on the sea for instance, the yacht would sail on in the same direction as if on rails, till the sails dropped in pieces. This diagram gives the disposition of the booms by means of their respective sheets. To make a yacht sail full and by, i. e. close to the wind, and neither run off or shake, the jib is nearly parallel to the bowsprit, the foresail less so, and the mainsail least ARROW SHOWS DIRECTION of all, and clearly shows the principle, for it is evident that if the vessel turned more towards the wind, the mainsail would shake, and the jib and foresail keeping still full, would turn the ship back to her course again, viz. "full and by." On the other hand, she cannot run off the wind, because the mainsail, well full as it must be, if she ran off, would bring her up again instantly. I presume every intelligent person understands that a vessel cannot sail with her head to the wind (all the sails must shake, and she would go a- stern), and few vessels can sail nearer, if so near, as at an angle of 45° to the wind. In the next diagram (p. 92), will be shown the way to sail the vessel in any possible direction, and how the booms must be disposed, and the rudder or rudders and ballast bags used to accomplish it. The wind is supposed to be blowing in the direction the arrow flies, and by holding this diagram with the arrow towards the point the wind is blowing from, your vessel can be made to sail in every direction there indicated. No vessel can head nearer towards the wind shown by the arrow, than a and aa, one being on the larboard, the other on the starboard tack (as it is called), i. e. about 45°, four points of a compass, or half a right angle. |