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24 | MARINE REVIEW. divisions. This applies also to a considerable part of the water bottom forward and aft of the straight midship body, and, as will be seen here- after, to a large part of the ship above the tank top. Forward and aft of the midship body the channel floors are continually growing shorter and the bilge brackets longer, as the extremities are approached. The bilge bracket soon becomes too large if its inner edge is kept straight, and it is, therefore, cut out to a curve and fitted with a reverse frame. When the channel diminishes to about 6 feet in length its use is abandoned and ordinary plate floors with frame and reverse frame substituted. While one diminish mould for each body answers for the floor chan- nels, separate moulds for each bilge bracket must be made. When bolting the various parts together, however, to make the complete floor, the same test moulds answer as are used for amidships, the position of the outboard: upper point of each frame 'being marked upon them, so that all the floors from one end to the other of the water 'bottom are completed and riveted at one time. The center keelson having been riveted and caulked, heavy floor ribbands are now erected at each side at a distance from the keel just inside the extremities of the floor channels. The garboard plates are now raised into position, bolted to the keel plate on the inner edge and held up by temporary vertical shores near the outer edge. Similarly the other strakes of the bottom plating for all the flat part of the bottom are put up in succession and supported in the same way. The total weight being small, only very light shoring is required. The floors are now brought over by locomotive crane from where they were stored, after being riveted on the hull machine, and dropped into place on top of the bottom plating by an overhead traveling crane. The inner end rests on the keel and the outer end on the floor ribband, a bolt or two through the bracket and keel- son stiffeners being put in at the same time. Quickly thereafter the longi- tudinals and intercostals are put in, the channel seam straps rove across, and the whole carefully leveled and squared up, one or two tank-top plates being put on to hold everything secure. All the work is now carefully bolted, reamed by pneumatic drills, and is ready for riveting, which is started at once amidships by pneumatic yoke riveters for the inside and by pneumatic shell riveters for the bottom plating, nearly all the rivets in the hull being machine driven. As soon as the channel seam straps and ties are riveted to the bilge brackets, the tank margin plates are put on and the angle on top of same for the bracket connections, and all riveted. The bilge plates are now templeted from the work, punched, rolled, and bolted up in position. That these plates are not gotten out from moulds like the others is principally because the very careful work on a surface of so sharp a curve is too expensive. At the lapped butts it is evident that the radius is greater for the outside plate than for the inside, and in any rolled plate the necessary difference 'between the lengths of the two surfaces is obtained sometimes by compression on the inside and sometimes 'by extension on the outside, and there is no way of determining beforehand which will occur. Further than this comes in the slight irreg- ularity in the height of the floor ribbands, the effect of which is magnified at the 'bilges, increasing the chance of bad holes and spoiled plate. While the use of this mould system requires in any event a good solid founda- tion under the ship, it must be remembered that this is only piling; that shores and blocking are of wood, only roughly cut to length and wedged up; and that ribbands are also of wood, supported only at intervals, and lined up principally by a ship's carpenter's eye.. While our experience has amply proven that for such parts of the bottom as have been already de- scribed--all straight work--these sources of error are quite negligible, that is not so with the bilge plates, even amidships, and it is much cheaper to templet these plates than to spend the time and money necessary to bring the framework of the tank to such perfection of outline and spacing that mould work could be depended upon in all cases. * With the bilge plates in place, the water bottom for the straight mid- ship body of the ship is completcd. The rémainder of the shell plating within the limits of the water bottom, the margin plates and other plates ot the tank top are templeted off in the ordinary mannet. In the mean- time, the channel frames and belts for the sides of the ship above the tank for the straight midship body and for some distance forward and aft of same, until the curvature becomes too great and bevelling commences, have been cambered cold in a héavy power bending press. These frames and belts having been ordered to lengths taken directly from the mould- loft floor, the variation in length is very slight from what is actually re- quired, and is taken up at the lower ends, which stop about 4 inches short of the margin plate of tank to form a waterway. The main-deck line and side stringets, and the plate edges of all side strakes, are run in parallel to the upper deck sheer. One mould for the web and one for each flange of frames and bolts, therefore, answer for all holes down to and including the lower side stringer. The holes at the bottom for the rivets connecting the channel frame or tbelt to the tank-top bracket are put on from the same mould, but as these holes are set to a level-line, which is the height of the top of the center vertical keelson, the mould must be moved down at each frame a distance equal to the raise of the sheer at that frame, these sheer heights of spar deck being marked on the upper end of the mould, The spar-deck 'beam brackets and the main-deck lower brackets are now laid out, each from its own mould, for all that 'part of the ship for which the tumble-home is constant, punched, bolted on to the frames and belts, and riveted by a stationary riveter. The spar-deck beams are cambered and, with the straight main-deck beams, stanchions, shifting boards; channel ties and struts and 'thwartship hatch coamings, laid out from moulds and punched. Side stringer channels, which are in short lengths between belts, and Z-bar clips between frames are laid out, punched, and riveted together on the- ground by portable yoke riveters. Main-deck stringers for the straight body are laid out and punched, with the channel intercostal to the skin between belts, which is scored out to allow the frames to pass through. The three upper strakes of the side plating for the straight side are now laid out, punched, and countersunk. For the lowest of the three, the main-deck sheer, this does not include any more plates than those on the midship body, as the frame line begins to leave the tumble-home line at its lower end immediately the extremities of the dead flat are passed, the point of departure going higher with each frame. The between-deck strake has a larger number of plates on the flat side and the sheer strake the most of all. For laying out these shell plates a slip mould is used. I believe that this method of laying out side plating is origifal with Mr. E. Gunnell, superintendent of the Chicago Ship Building Co., to whom, in fact, the most of the development of the system is due. This mould is based on the principle of working from a level line parallel to the keel of the ship. The mould itself is square, the length inside of the end pieces. being the exact length of the plate. At about its center a straight line is marked across it. The frame strips and butt lap moulds are entirely separate from the main mould and have similar lines marked upon them, one butt mould having in addition a scale of inches marked on it, starting from the line at zero. The fitter is furnished with a table, prepared for the mould-loft floor, showing the sheer height of the spar-deck line at each butt. The squaring mould is now placed on the plate, the line on one butt mould brought. into exact accordance with the line on one end of it, and the other butt mould raised until its line is a distance above the level line on the squaring mould equal to the raise in the sheer from the table. A chalk line is then stretched between the two ends, snapped on, and the mark on each frame strip brought exactly to it. All the frame and butt holes are now transferred to the plate and the moulds are removed. When the seam lap moulds have been put on and the holes marked the plate is ready for punching and countersinking. If the sheer of the ship is so bold that the variation from the straight line in the length of a plate must be taken into account, it is only necessary to use the exact sheer height at each frame in setting the frame strips, but this seldom happens. There is now a large portion of the hull of the ship above the tank ready for erection, and it is assumed that sufficient of the water bottom, if not all of it, is completed and riveted, for a start to be made on the upper work. The water bottom or tank now forms a broad, solid founda- tion on which the remainder of the framing is erected, requiring no side shores whatever until the very extremities of the ship are reached. Evi- dently, however, as so much of the upper works have been laid out from moulds, any inequalities, however slight, in the tank must be corrected before this erection is started, otherwise bad work will result and the var- ious pieces will not come together correctly. For this purpose a line is leveled across the top of the center vertical keelson and marked on the inside of the bilge plates above the tank, corresponding to the line from which the side frames and belts were punched, referred to previously. The frame and belt 'brackets are now placed in position between the angles on the tanktop margin plates and the position of this level line transferred directly to them, and at the same time the bottom holes are marked from the angles. The tbracket plates are then taken to the shop and the remain- ing holes for the frame and belt rivets marked off from the moulds which were used for the corresponding holes in the frames and belts. As these moulds in each case are set from the level line spots referred to, it is evi- dent that when the brackets are put back in position on the ship and the frames and-belts 'bolted thereto, their tops will come true to the spar-deck line independent of high or low points in the tank margin itself, and, there- fore, the main-deck line, stringers, and plate edges will also come true. The belts, stanchions, and main-deck beams are now erected by the overhead crane, leveled, plumbed, and squared up, the whole making a self-containing structure. The sheer strake is then bolted into place and the frames put up. As soon as the shifting boards, bulkheads, and main- deck stringers and ties are in place, the spar-deck heads are put in and the shell plating 'bolted up with the upper and lower side stringers. The spar- deck plating between hatches which had previously 'been punched from moulds--corresponding plates in each space being exactly alike, except for manholes, mast holes, etc.-- is now put in place, as well as the channel ties and intercostals under and between the spar-deck beams, and the athwart- ship hatch coamings. When all bolted and reamed a large amount of work, both inside and shell, is opening up for the machine riveters. -The remain- ing strake of side plating amidships--that immediately above the bilge-- is now templeted off the ship, thus eliminating the effect of any variations in the height of the tank margin. : ! The above description includes about all of the ship which is gotten out by what may be called duplicate mould work. The remainder of the framing at the ends, etc., is laid out, furnaced and punched from ordinary iidividual wooden moulds, and the plates, stringers, etc., templeted off the work in the usual manner. No scrieve board is used. In general, it may be said that the system used in the Chicago yard requires very careful work in the mould loit, explicit directions to ithe foreman in charge of each ship, and a thoroughly competent and experienced superintendent in actual charge of the yard to harmonize the work of the various shop and outside foremen and to decide where duplicate work shall stop and a return be made to ordinary methods. This is principally a matter of cost in every case. If too much time and labor is required ito bring certain portions of the structure to such. exact accordance with the mould-loft floor, that other portions following them, laid out-from moulds made from the floor, will go exactly into place, it is cheaper to follow ordinary methods, where a much greater variation is allowable, because each piece is based only on the piece next ahead of it, and therefore, errors are not cumulative. Asa matter of personal opinion, however, after an experience covering the con- struction of some thirty ships of large size under the mould system, the writer thoroughly believes that this system is the cheapest known and can be applied to a large extent with great advantage in any yard where large ships are \built, of any type. WELL REPRESENTED AT GLASGOW. __ A Glasgow correspondent of the Marine Review says: "The relative interests of the nations in shipbuilding is well shown by the number of students they give to the subject. At the University of Glasgow, the in- ternational school for the study of naval architecture, the nationality and number of students is as follows: American, 15; Scotch and English, 13; Belgian, 2; Argentine, 2; Japanese, 2; Swede, 1; Finn, 1; Italian, 1. "As to the type of water tube boiler to be used, there are as many to choose. from as there are fleas on a dag," says Enginéer-in-Chief Melville of the United States: navy. «Someone has:said that a certain amount of fleds keep a' dog from brooding 'over being a dog. So the number of varieties we have to c':00se from may be a good thing for all.