An Universal Dictionary of the Marine / Or, a Copious Explanation of the Technical Terms and Phrases Employed in the Construction, Equipment, Furniture, Machinery, Movements, and Military Operations of a Ship. Illustrated With Variety of Original Designs of Shipping, in Different Situations; Together With Separate Views of Their Masts, Sails, Yards, and Rigging. to Which Is Annexed, a Translation of the French Sea-terms and Phrases, Collected from the Works of Mess. Du Hamel, Aubin, Saverien, &c.

by William Falconer

Geometricians have determined the most advantageous angle made by the helm with the line prolonged from the keel, and fixed it at 54° 44´ presuming that the ship is as narrow at her floating-line, or at the line described by the surface of the water round her bottom, as at the keel. But as this supposition is absolutely false, inasmuch as all vessels augment their breadth from the keel upward to the extreme breadth, where the floating-line or the highest water-line is terminated; it follows that this angle is too large by a certain number of degrees. For the rudder is impressed by the water, at the height of the floating-line, more directly than at the keel, because the fluid exactly follows the horizontal outlines of the bottom; so that a particular position of the helm might be supposed necessary for each different incidence which it encounters from the keel upwards. But as a middle position may be taken between all these points, it will be sufficient to consider the angle formed by the sides of the ship, and her axis, or the middle-line of her length, at the surface of the water, in order to determine afterwards the mean point, and the mean angle of incidence.

It is evident that the angle 54° 44´ is too open, and very unfavourable to the ship’s head-way, because the water acts upon the rudder there with too great a sine of incidence, as being equal to that of the angle which it makes with the line prolonged from the keel below: but above, the shock of the water is almost perpendicular to the rudder, because of the breadth of the bottom, as we have already remarked. If then the rudder is only opposed to the fluid, by making an angle of 45° with the line prolonged from the keel, the impression, by becoming weaker, will be less opposed to the ship’s head-way, and the direction N P, fig. 1. plate [V]. of the absolute effort of the water upon the helm drawing nearer to the lateral perpendicular, will be placed more advantageously, for the reasons above mentioned[^[33]]. On the other hand, experience daily testifies, that a ship steers well when the rudder makes the angle D B E equal to 35° only.

It has been already remarked, that the effect of moving the wheel to govern the helm increases in proportion to the length of the spokes; and so great is the power of the wheel, that if the helmsman employs a force upon its spokes equivalent to 30 pounds, it will produce an effect of 90 or 120 pounds upon the tiller. On the contrary, the action of the water is collected into the middle of the breadth of the rudder, which is very narrow in companion with the length of the tiller; so the effort of the water is very little removed from the fulcrum B upon which it turns; whereas the tiller forms the arm of a lever ten or fifteen times longer, which also increases the power of the helmsman in the same proportion that the tiller bears to the lever upon which the impulse of the water is directed. This force then is by consequence ten or fifteen times stronger, and the effort of 30 pounds, which at first gave the helmsman a power equal to 90 or 120 pounds, becomes accumulated to one of 900 or 1800 pounds upon the rudder. This advantage then arises from the shortness of the lever upon which the action of the water is impressed, and the great comparative length of the tiller, or lever, by which the rudder is governed; together with the additional power of the wheel that directs the movements of the tiller, and still farther accumulates the power of the helmsman over it. Such a demonstration ought to remove the surprize with which the prodigious effect of the helm is sometimes considered, from an inattention to its mechanism: for we need only to observe the pressure of the water, which acts at a great distance from the centre of gravity G, about which the ship is supposed to turn, and we shall easily perceive the difference there is between the effort of the water against the helmsman, and the effect of the same impulse against the vessel. With regard to the person who steers, the water acts only with the arm of a very short lever N B, of which B is the fulcrum: on the contrary, with regard to the ship, the force of the water is impressed in the direction N P, which passes to a great distance from G, and acts upon a very long lever E G, which renders the action of the rudder extremely powerful in turning the vessel; so that, in a large ship, the rudder receives a shock from the water of 2700 or 2800 pounds, which is frequently the case, when she sails at the rate of three or four leagues by the hour; and this force being applied in E, perhaps 100 or 110 feet distant from the centre of gravity G, will operate upon the ship, to turn her about, with 270000 or 308000 pounds; whilst, in the latter case, the helmsman acts with an effort which exceeds not 30 pounds upon the spokes of the wheel.

After what has been said of the helm, it is easy to judge, that the more a ship increases her velocity with regard to the sea, the more powerful will be the effect of the rudder, because it acts against the water with a force, which increases as the square of the swiftness of the fluid, whether the ship advances or retreats; or, in other words, whether she has head-way or stern-way; with this distinction, that in these two circumstances the effects will be contrary. For if the vessel retreats, or moves astern, the helm will be impressed from I to N, fig. 1. plate [V]. and, instead of being pushed, according to N P, it will receive the effort of the water from N towards R; so that the stern wall be transported according to the same movement, and the head turned in a contrary direction.

When the helm operates by itself, the centre of rotation of the ship, and her movement, are determined by estimating the force of this machine; that is to say, by multiplying the surface of the rudder by the square of the ship’s velocity[^[34]]. See the articles Rudder, Sailing, Steering, Trim, and Working.

HIGH AND DRY, a phrase which implies the situation of a ship, when she has run aground, so as to be seen dry upon the strand.

HIGH WATER, haute marée, the greatest height of the flood-tide, See Flood and Tide.

HITCH, clef, a sort of knot or noose, by which one rope is fastened to another, or to some other object, as a post, ring, timber-head, mast, &c. Hence we say an half-hitch, demi-clef, a clove-hitch, a rolling-hitch, &c. See Bend and Knot.

HOASE, manche pour l’eau, a long flexible tube, formed of leather or tarred canvas, but chiefly of the latter, and employed to conduct the fresh water, which is hoisted aboard a ship, into the casks that are ranged in the hold; and to pass the water, or other liquors, out of one cask into another. For the latter use, one of the ends or openings of the hoase is fixed in the empty cask, whilst the other is applied to the pump that extracts the water out of the full one. This exercise is, on some occasions, necessary to alter or preserve the trim of the vessel, without disturbing her stowage.

HOG, goret, a sort of flat scrubbing-broom, serving to scrape off the filth from a ship’s bottom, under water, particularly in the act of boot-topping, which see.