Page:The American Cyclopædia (1879) Volume XIV.djvu/889

 SHIP 8G3 nearly parallel in width and of various thick- nesses; the plank or wales above water are the thickest, being in a large ship from 5-J- to 7& in., the bottom plank from 3 to 4 in. The lowest tier or strake of planks outside, known as the "garboard strake," meets the keel along an angular recess called a rabbet, which is cut into its side for the purpose of affording to these planks a tight fit along their lower edge. The keel is thus interlocked along its whole line between the planks each side of it. In large ships this lower tier is sometimes of timbers rather than of planks. The other planks are from 3 to 7 in. thick. To obtain the curves required for the planks to fit the bends, these are steamed in tanks, and then are brought into shape by bending them with screws and levers between fixed supports. The inner planking, known as the ceiling, begins near the keelson with what is called the lim- ber strake, extending along the whole bottom of the hold, one on each side the keelson. The narrow space between is for a gutter to col- lect the drainage water, for delivering it to the pumps. Such a passage is called a limber. The strakes over the heads and heels of the timbers are thicker than elsewhere, to give additional security against their ends being pressed in. As the planking is carried up, the projecting pieces called shelves are set in their places and strongly secured, the deck beams are laid npon them, and the ends of these are fastened with wooden or iron knees of great strength. Under the middle of the beams are placed pillars, starting from the keelson; these pre- vent the settling of the beams, which are arched upward, and their consequent thrust- ing outward of the sides instead of tying them to a fixed width. As in the rolling of the ship a powerful strain is exerted to lift the ends of the beams, this is also guarded against by another projecting timber set in the planking directly over the beams. This is called the waterway, and is secured by vertical bolts ex- tending through the beam and shelf, and by horizontal bolts that pass through the frame and outer planking. The planks are fastened to the timbers with treenails (i. <?., pins of lo- cust) or with bolts or spikes. Treenails have sometimes been made with a thread cut round them and a square head by which they are seized and screwed into the holes. For the decks yellow pine planks are commonly used, except along the sides of the ship, where a strake of hard wood thicker than the rest of the planks, called the binding strake, is laid for a waterway. In laying the deck planks atten- tion should always be directed not merely to their use as a covering, but also to their action as longitudinal ties for the frame. In some instances decks have been laid diagonally from one side to the other, obviously involving a loss of strength; ships have also been built with three layers of planks for the decks and outer covering, two diagonal layers crossing each other, and a third upper layer running 739 VOL. xiv. 55 longitudinally. At the ends of the ship the shelf pieces, waterway planks, and strakes are secured to the beams, and crutches attached to the stern post and to the timbers called breast hooks, that spread out from the stem. The openings left in the deck for hatch and ladder ways necessarily weaken it somewhat, though they are provided with stout framing secured to the beams. The holes for the masts are large enough to receive wedges all around of 8 to 6 in. thickness. For supporting the masts blocks called steps are fastened to the keelson, or for light masts to one of the beams, and into a cavity of these blocks the heel of the mast is set. A great variety of work still remains for the ship carpenter to complete before he can give place to the calker, whose office it is to make the seams of the deck and outer planking water-tight. The bulwarks have to be finished, the pumps placed, the capstan or windlass for raising the anchor, the catheads for suspend- ing it over the sides, &c. Calking consists in driving threads of oakum, rolled up in the hand, into the seams between the planks ; and that it may reach to the bottom and make the seam perfectly tight, the planks should be bevelled on the outer edge to present an opening gradually closing toward the bottom. The widm of the opening is sometimes in- creased by driving in an iron wedge-shaped tool, and the oakum is then crowded in with great force by the calking iron. "When the seams are filled they are payed over with melted pitch ; but a much better material sometimes used is the marine glue, prepared from shell lac and caoutchouc. (See GLUE.) The rudder is sometimes hung before launch- ing, but more frequently afterward. This is made of timbers as thick as the stern post, up and down which it extends, and to which it is suspended by pintals on the rudder fitting into braces on the stern post. The head of the rud- der passes up through the stern above the deck, and to this a handle called a tiller is fastened for turning the rudder. The ship being ready for the launch, two parallel lines of heavy timbers are laid along her length, one on each side, and continued down into the water till sufficient depth is reached for the vessel to float. The fall of the water at low tide affords the opportunity for doing this. The slope of this track, or of the "ways," is about seven eighths of an inch to the foot for large vessels ; small vessels require a little more inclination. The timbers are held together by others under- neath crossing them, and the frame is kept down by being loaded with stones; this at least is the practice where the sliding ways are not permanent. The top of each timber is well covered with melted tallow, and upon this when cold is added soft soap or oil. On the top along the outer edge a ribbon of hard wood full 5 in. square is fastened down, and braced by a succession of shores extending back on each side against some solid support in the ground ; the object of this ribbon is to prevent