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stations; these plans, of intersections of trans- 200 positions of decks, ports, and general outline of the hull, is termed the sheer draft, and this is the drawing which is chiefly required in laying off. Other data are required, but these will be given in their proper places; at present we will confine our atten- tion to the sheer draft. And here it may be remarked that the several processes of laying off are dealt with in the following pages in the same order as the draftsman lays off his ship upon the mold-loft floor. Before proceeding further, it is necessary that we should examine the sheer draft in order that we may become acquainted and _ familiarize ourselves with the names and _ uses of the various lines composing it. The Sheer Draft Fig. 4 shows the sheer draft of a sloop of war. This is a fair type. of a sheer draft as prepared at the Admiralty for the construction of vessels in dockyards. In Fig. 4, the lines marked 2WL, 3WL, etc., are the projections of the intersections with the surface of the ship of planes parallel to the load water plane; they with LWL, the intersection of the load water plane; are called water lines. It may be here remarked that, unless it is otherwise stated, by "the surface of a ship" is meant the outside of the frames and not of the exterior plank, as, after the form of the ship has been designed, the plank is taken off by a process to be afterward described, and thus the building draft shows the surface of the frames. The dotted perpendicular lines at the extremities, marked FP and AP, are the perpendiculars between which the iength of the ship is measured. The other perpendicular lines in the sheer and half-breadth are termed square they are projections, upon verse vertical planes with the ship's ~ surface. only the. intersections of the planes with the port side of that portion of the ship on the foreside of her fullest part of dead flat. By this means we have, without confusion, the projec- tions in the body plan of the whole of the traces of these vertical planes with the surface. At the present time the alphabetical designations are sometimes discontinued, and the _ numerical mode is used for the two bodies, commencing forward or aft _ as: the case may- be. These plane sections are made at the joints of the two sets of timbers composing wooden frames, and at the 'sides of angle i iron frames; okey are generally 1e todd: oF In the body plan is projected _bet, THE MARINE REVIEW the others, this being done in order to allow room for a single timber frame, about which the relative posi- sitions of the component timbers of the frames were shifted, all the tim- bers on the fore side of the single timber being disposed by a certain ruJe, and those abaft it being dis- posed im a contrary 'Manner. Et should be further stated that the spaces between the joints of the frames of some recently constructed wooden war ships have been greater toward the extremities than at amid- ships, in order to lighten the framing at those parts whith receive least buoyant support. Again, referring to Fig. 4, TS is the topside line, and besides this the form of the upper deck, as projected in the three plans, is also shown; these are given in order to represent the form of the vessel above the water lines. Generally, a line, termed a top- breadth line, is drawn somewhere between the topside and load water ine; and, in large ships, lines at the port sills are given for the same purpose. The lines marked K show the upper and lower edges of the keelson, and at their extremities are shown the stemson and sternson. The dotted line marked A is the upper part of the keel, the two lines next below are the upper and lower edges of rabbet of keel; and below these are shown, in succession, ~ the lower edge of keel and the two pieces of false keel. The lines marked UDL in the sheer plan are, beginning at the uppermost, the lines of upper side of upper deck at middle line, upper side of upper deck beams at middle line, and upper side of upper deck beams at the ship's side respectively; these being usually known as deck at middle, beam at middle, and beam at sidelines. The vertical distance be- tween the first and second is, of course, the thickness of deck plank; that between the second and third is the round up of the beam--it is at once seen that the latter meet at the extremities of the deck. Besides the lines just noticed, there are also shown the knee of head, head rails, stern and munions, ports, masts and other de- tails. Conventional Usage is Adopted The upper edge of rabbet of keel is selected as the base line of the sheer draft shown in Fig. 4. This is a conventional usage which is adopted when, as in the present instance, the joints of the frames are per- pendicular to the keel. Before pass- ing on, it should be stated that the line termed the upper edge of rab- which is usually chosen as a base line, is 'incorrectly named beir merely a line parallel to" the lo edge of rabbet--a fixed line-- distant from it the thickness the bottom plank. By making this base line, and the ship not being on an even keel, causes the water lines to curved in the body plan as shown. Ip many cases the frames stand perpendi- cular to'the LWL, and in such cases a line drawn parallel to the fatter, and near the keel, has been chosen as a base, thus causing the square sta- tions in the body plan to end suc- cessively one below the other, as shown by Fig. 5 in the next install- ment instead of mostly at a point, as in Fig. 4 and the water lines in such drawings are, known as level lines. i er Fairing the Ship The sheer draft is usually prepared on a scale of 14 inch to a foot. This is copied full size upon the mold loft fioor, in performing which operation -- it is found that errors, almost in- appreciable in the one-quarter scale -- drawing, become very apparent when -- thus magnified 48 times. The three plans which, when upon paper, coin- cide as nearly as the draftsman's powers will permit, when copied to full size are found to disagree suff- ciently to prevent the various prob- lems of laying off from being solved with that degree of accuracy which -- is mecessary in order to obtain a fair -- surface to the ship. Hence a fairing, | or correcting process has to be per- formed before the timbers can be | laid off. we The mutual dependence of the three -- plans upon each other has already been shown; this property is utilized in performing a tentative process -- termed fairing the body. It has been shown that the projections of each of the sets of lines generally used in this process, viz., level lines, -- sguare stations, bow lines, and diagonal Sem lines, appear straight in one or two of the plans; so that, by the aid of a straight-edged batten, they can be drawn fair very readily in such plans. The property which a wooden or metallic batten has of bending im a fair curve, is brought to our aid in drawing the lines fairly in the plans where they appear curved. For, since the intersections of lines with each other are points, the points of inter- section of two sets of lines in one plan are transferred to their relative : positions in others, so that points -- Which, when in one plan, were in a straight line, are now in a curved line; a batten is penned, or bent tO -- pass through as many of the points as is consistent with absolute fa ness, and the line is drawn. T