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4 MARINE REVIEW. [April 4, — CONSTRUCTION OF TORPEDO BOATS AND DESTROYERS. BY GEORGE HERBERT WILSON. TRANSVERSE FRAMES AND SCANTLINGS. Departing from the consideration of longitudinal strength, the matter of transverse stiffness must reauire considerable attention, although not calling for as much as the former, and the weight and size of scantlings should be designed in proportion. The importance of the transverse fram- ing of a boat cannot be gainsaid, nor can too much thought and care be used in the design thereof, the correct proportion of the weights to the strength depending upon the scantlings. As in all por- tions of the hull structure, a correct idea of the princi- pal functions must be known to provideadequate means for their performance. The main work devolving upon the transverse framing is that of maintaining the shape of the boat as constructed, provid- ing sufficient stiffness to pre- vent any tendency to crush- ing or change of form in the transverse direction. In ad- dition to this important duty the transverse frame must be regarded as a “tie member” connecting the various por- tions of the boat in its vicin- ity. The frames themselves are tied together by the floor plate. The deck is secured to’the frames by means of beam knees or brackets. The longitudinal bulkheads re- ‘ceive additional support in the brackets connecting them to the frame at the bottom and to the deck beam at the top. 5 The floor plates, how- ever, form the main connec- tion and are relied upon for stiffening the lower portion of the hull structure in conjunction with the keel and longitudinals, and their depth is decided by the amount of ma- chinery, boilers, cargo. etc., carried in the vicinity. The “shapes” most desirable for a transverse frame of a boat are the bar, angle or bulb angle. The first of these is, no doubt, superior where great strength is necessary, and it is used on some of heavier naval work at present. The second finds universal favor, however, from the cheapness of the section and the greater ease in bending, and principally in beveling. This shape is used on the boats whose transverse sections are shown on plates 5 and 6. The third shape is very desirable from the disposition of the metal in the section, the bulb adding greatly to the stiffness, and is used a great deal in the class of boats with which we are dealing, from the lightness of the section compared to the moment of resistance. This style of frame is shown on the transverse section in plates 7 and 8. For the reverse frames the angle section is generally used, as it appears to answer to all the requirements. METHODS OF WORKING THE REVERSE FRAMES. Various ideas as to the method of working the reverse frames ie in use, but the most common practice is to carry them along the top of the floors on the opposite side to the frame bar. At the end of the floor — plate the bar is bent and carried up along the frame for some distance, the distance varying on alternate frames. In some cases the bulb angle séc- tion is used as a reverse bar, as shown on plate 7. In the transverse sec- tion shown on plate 5 the angle shape is used. The floor plates forming so important a number of this part of the hull structure, constitute the main “tie,” as previously mentioned, for the lower portion of the boat. Being supported by the frames at the bottom and the reverse frames at the top, and the frames being riveted to the shell plating, a very rigid and valuable support is gained to guard against transverse racking strains. The floor plates are decreased in weight to a considerable extent by various types of lightening holes, care being taken to provide sufficient metal to resist tension stresses and buckling. As regards the methods of designing and erecting the floor plates sufficient has been said in the previous articles on these items to gain an idea as to the best practice to follow in various cases. -I refer to the question of continuous floors or continuous keels and longitudinals. In plate 6 is shown the type of a continuous floor plate and intercostal keel. Plate 5 shows the continuous keel bar on top of a continuous floor plate, Plates 7 and 8 give an idea of the construction where the keel and floor are semi-continuous. In some of the later torpedo boats and destroyers the practice of flanging the upper edge of the floor plate has been followed in addition to the reverse bar. Where weight is of more importance than strength the reverse bar can be omitted except a short piece at the ends of the floors to prevent a sudden reduction of strength. The practice of making the floor plates in three pieces has been followed out in some of the boats now building, the two end sections being reduced in weight from that of the $2/¢%266:Las AMsDswies. LTeatlont63 + Ar Eros. ttle | 3% 2°39, $:Le% AM/OSHIE: | 2¢x/3%2-Las. L£vos. middle portion. Double riveted lap butts form sufficient connection be- tween these plates. This method has two very important features, the first of which is obviously the great saving in weight, and the second is the decrease in cost of material and ease in handling and erecting the smaller plates. In the lightening of floor plates considerable attention has been given to the cheapest and most effective method of doing the work. This must depend largely upon the types and sizes of the holes designed. I will attempt to cover a part of this ground in a later article, epusnine upon the various machines, dies, etc., likely to enter into sucit work, BRACKET CONNECTIONS TO THE DECK BEAMS. Continuing along the line of the transverse scantlings, we will ignore the bottom and side plating, which will appear in a later article, and give some attention to the bracket connections to the deck beams. These must necessarily vary in shape and size to conform to the shape of the deck. The depth of these brackets on frame and beam is determined by the number of rivets necessary to gain the required strength. Light- ening holes can be conveniently allowed without impairing the efficiency of the bracket. In some boats the practice of flanging the bracket on the