BALLAST

There is often great difference in the proportion of ballast required to prepare ships of equal burthen for a voyage; the quantity being always more or less, according to the sharpness or flatness of the ship's bottom, which seamen call the floor.

The knowledge of ballasting a ship with propricty is certainly an article that deserves the attention of the skilful mariner; for although it is known that ships in general will not carry a sufficient quantity of sail, till they are laden so deep that the surface of the water will nearly glance on the extreme breadth amidships, yet there is more than this general knowledge required; since, if she has a great weight of heavy ballast, as lead, iron, &c. in the bottom, it will place the center of gravity too low in the hold; and although this will enable her to carry a great sail, she will nevertheless sail very heavily, and run the risk of being dismasted by her violent rolling..

To ballast a ship, therefore, is the art of disposing those materials so that she may be duly poised, and maintain a proper equilibrium on. the water, so as neither to be too stiff, nor too crank, qualities equally pernicious: as in the first, although the ship may be sited to carry a great sail, yet her velocity will not be proportionably increased; whilst her masts are more endangered by her sudden jerks and excessive labouring: and in the last, she will be incapable of carrying sail without the risk of oversetting.

Stiffness in ballasting is occasioned by disposing a great quantity of heavy ballast, as lead, iron, &c. in the bottom, which naturally places the center of gravity very near the keel; and that being the center about which the vibrations are made, the lower it is placed, the more violent will be the motion of rolling.

Crankness, on the other hand, is occasioned by having too little ballast, or by disposing the ship's lading so as to raise the center of gravity too high, which also endangers the mast in carrying sail when it blows hard: for when the masts lose their perpendicular heighth, they strain on the shrouds in the nature of a lever, which increases as the fine of their obliquity; and a ship that loses her masts is in great danger of being lost.

The whole art of ballasting, therefore, consists in placing the center of gravity to correspond with the trim and shape of the vessel, So as neither to be too high nor too low; neither too far forward, nor too far aft; and to lade the ship So deep, that the surface of the water may nearly rise to the extreme breadth amidships; and thus she will be enabled to carry a good sail, incline but little, and ply well to the windward. See the article TRIM.

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