We have assumed the work of the naval architect to be complete; all the specifications have been made out, and every part of the prospective ship has been drawn on paper. There are three plans: a “sheer plan,” showing all lines of length and height from stem to stern; a “half-breadth plan,” showing the lines of length and breadth, or, in other words, those lines which would be visible in looking down upon her decks from an elevation; and a “body plan,” which shows all lines of breadth and height, and represents the ship looked at “end on.” These are called the “construction drawings,” and with them in his hand the ship-builder can see in his mind’s eyes the vessel as she will appear when built. He does not work directly from these, however. They are carried up into the “mould loft,” the floor of which represents an enormous blackboard, and upon this they are reproduced to correspond with the exact dimensions of the ship. A foot is scaled down on the paper to a quarter of an inch, but in the mould loft a foot is a foot, and plate, girder, and rib are drawn to their full size. This enlargement leads to the detection of errors which are not apparent in the reduced drawings, and which must be eliminated. Straight lines are made with chalk by cords and rules, and curves by bending laths into the desired position and then tracing the sweep upon the floor. Every measurement has to be verified and checked, and “fairing the ship,” as this work is called, may take six or seven weeks. All errors having been corrected, still another drawing is made on a “scrive board,” and in this the lines, full-sized, are sunk in the wood so that they cannot be rubbed out. The “scrive board” is the plan from which the ship-builder works, and when it is complete the actual construction of the ship is begun.
General View of the Frames of the City of New York—June 25, 1887.
The keel is laid down on blocks, four or five feet apart, which form a slope toward the water, so that the hull may glide down easily when the time for launching comes. It is not a keel at all, in the sense in which the word was formerly used: a modern ship has a smooth bottom, without any projecting ridge or break to the curve of her sides; it is simply the central series of plates, from which an inner keel is built up like an enormous backbone, and to this the ribs are attached. The metal is delivered at the yard in the shape of angle iron or angle steel, the latter being the material which would be used in a ship of the class we have in mind. Heated to a white heat, the angle-bars are drawn out of the furnace into a perfectly level iron floor, upon which they are bent to the needed curve, and that which has been a line of ink in the original drawing, a chalk mark on the floor of the mould loft, and a groove in the surface of the “scrive board,” is now embodied in the heavy rib of the ship. The bending is done thus: the metal floor is perforated with thousands of holes, into which iron pegs are inserted until they form the curvature required, and the long, pliable bar of steel is pressed against them until it corresponds exactly with the line exhibited in the “scrive board,” which is always in sight of the workmen for guidance and comparison. In handling the metal the men use pitchforks, and with the prongs inserted in the holes they get purchase enough to make the bar yield; if it bends upward a hammer is used upon it. Each rib has, of course, to be duplicated with the utmost precision, in order that it shall be the same on both sides of the ship, and each, after it has cooled, is laid upon the “scrive board” and compared with the lines thereon, every variation being corrected before it is passed. Having already been punched for rivets, it is then marked with a chisel to show where rib-bands, stringers, and deck-beams are to fit into it.
Two or three months or less after the completion of the “fairing,” the ship is probably “in frame,” and looks like the skeleton of some Brobdignagian monster that has stranded on the bank of the river. The ribs have been hoisted into position at right angles with the keel, and strung together by “rib-bands,” and already there are signs of the coming subdivision by decks and bulkheads of the hollow space within. You can still see through her, however; she is like, to make yet another comparison, a great oblong wicker-basket, the supple willows being represented by the net-work of steel.
The next step is the clothing of the ribs with plates. As they reach the yard the plates are square and flat, but they are passed through rollers of various kinds, from which they issue in any shape desired—hollowed like a spoon, curved lengthwise or breadthwise or diagonally, as the contour of the ship may call for. A steam or hydraulic plane smooths them down as though they were the softest of whitewood; another machine trims the edges as easily as a woman cuts silk with a pair of scissors. Then, suspended by iron chains, they are thrust between the jaws of a punching machine, which has a resemblance to a sinister human face with a flat nose, a long upper lip, and a small chin. The jaws close upon them and bite out, ten at a time, the holes for the rivets by which they are to be fastened to the frame.
As they are hoisted up to the workmen, each fits the exact place designed for it and takes its part in the softly swelling lines of the ship. They are put on in rows, or, as rows are technically called in this connection, “strakes,” which are lettered alphabetically, A being the row riveted to the keel. The upper edge of A overlaps the lower edge of B, and the lower edge of C overlaps the upper edge of B, and thus while one row of plates like B has both edges hidden, the row above it has both edges exposed, which minimizes resistance to the progress of the ship. We all know what caulking a wooden vessel is—the wedging of all seams between the planks with oakum and tar. An iron or steel ship is also caulked, but in her case the word has a different meaning. The sharp edges of the plates are merely turned in with a chisel, and they meet so closely that no insertion is necessary to exclude the water.
Frames of the City of New York, looking aft—July 19, 1887.