Engineering Wonders of the World
Volume I

70 ENGINEERING WONDERS OF THE WORLD. hull will have the exact curves required. The outline of the frames is then “ scrived ” or cut into the boards, and the boards trans- ferred bodily to the bending slabs for the guid- ance of the frame-turners in preparing the frames in the manner described later. Moulds, or templates, of thin wood, are then made for the various internal portions of the vessel’s structure, for the stem bar (of which an ex- planation is about to be given), and for a great many of the plates and bars. Fig. 7.—DIAGRAM TO SHOW THE FRAMES, LONGI- TUDINAL STRINGERS, AND CROSS BEAMS OF A SHIP. While work in the mould loft is proceeding, the numerous detailed drawings, which in due course will have to be issued to the workmen in the shipyard, are being pushed on in the drawing-office, and further material is ordered as the working drawings are developed. Dur- ing the whole of the various stages of construc- tion, the staff of the drawing-office must also keep a careful watch on the weights being worked into the hull ; while the timekeepers and accountants are making an accurate record of workmen’s time and the cost of material. As soon as the laying-off is well in hand and the building material begins to arrive at the yard, the shipwrights and their labourers pre- pare the building berth, or slip, Laying- the on which the vessel is to be Keel. laid down, and commence plac- ing the keel blocks. These blocks, which are of tough rectangular timber, 4 to 6 feet long, are placed in piles at a reasonable distance apart, determined by the weight of the vessel to be supported. It is on these keel blocks, as the name implies, that the keel of the vessel is to be laid, and it is therefore essential that they should be carried to such a height above the ground as will give ample space for the riveters and others who will have to work under the ship. The tops of all the blocks, which, are fitted with cap-pieces of oak or other hard wood, are accurately adjusted to a plane sur- face sloping about a J-inch in a foot from the top of the berth to the water’s edge, or, in other words, from where the vessel’s bow will rest on the blocks to where the stern will be supported near the water. This declivity, of course, is necessary to facilitate launching the ship when the proper time arrives. Fig. 8.—THE BENDING SLABS IN A SHIPYARD. In the foreground is the hydraulic press which does the bending. The frame is held down against the slabs by iron dogs having one end inserted in the slab holes. The keel of large merchant ships and war vessels usually consists of wide horizontal plates running along the centre line of the bottom. Immediately over the flat keel plates and at the centre line a vertical girder, known as the centre keelson, is fitted the full length of the double bottom. This centre keelson is connected at its lower edge to the keel plates and at its upper edge to the plating in the centre of the inner bottom, or tank top. The construction of the cellular double bottom, in- tended for carrying water ballast when the ship is at sea, is then proceeded with. The work at this stage is well illustrated in Fig. 9; which is a photograph taken during the build-