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TAE MARINE REVIEW 15 HABITABILITY., Special provision must be made to secure proper living quarters for the personnel. The condition and state of such quarters while under forced draft should be consid- ered in its hygienic relations. The endurance of the vessel and her efficiency as a scout depends upon the endurance of her personnel. Suitable living quarters that will pro- vide ample sleeping accommodations and a well ventilated and dry resting place in rough weather will serve to main- 'tain the crew in good physical condition and contented state of mind, the effect of which upon the endurance and the capabilities of the vessel will be worthy of thorough consideration. Good living quarters with ample room for the crew are provided by providing a raised forecastle deck which ex- tends aft to the forward smoke stack and by having the whole gun deck fore and aft available for living quarters, The high free board, 34 feet forward and 22 feet aft, will serve to make these quarters dry and airy. ' STRUCTURAL STRENGTH. Good structural strength with least weight is to be ob- tained by care in locating bulkheads and intelligent use of pillars, beams, ties and stiffeners. The bulkheads and decks should be continuous and as few holes as possible for communication should be cut. Special care must be taken to secure proper solid found- ations for the engines and auxiliaries so that their weights are well distributed, and that excessive vibrations are avoided. In order to better distribute the weights the engines are placed one abaft the other. This does not allow of as handy an engine arrangement, but in this case handiness in arrangement must be sacrificed to obtain better structural strength and distribution of weights. FINENESS OF HULL. ge high speed vessels the form of hull is a very ma- terial factor in governing the power necessary to attain the speed. At ordinary speed, below 13 knots, the effect of wave making resistance is a relatively small portion of the total resistance, but as speed increases the wave making resistance which depends on the form of hull increases very rapidly so that at speeds of 25 knots it may amount to one half of the total. resistance. The importance of having lines of hull adapted to the speed is of such importance that numerous models have to be tried. The lines which show the best propulsive efficiency may however not be those well suited to the proper location of the machinery and propellers so that alterations from best form are sometimes necessary in order that engines and boilers may be located to better advantage. The lines must also be adapted to secure necessary stability and the above water part of the vessel must be such that the action of the waves in affecting the speed and steadiness of the vessel should be a minimum. | MACHINERY. : _ This must be thoroughly reliable, and therefore it will not be wise to crowd into the space all the horsepower possible with the result of a very -unhandy installation and rapid decay due to crowded condition. Duplication and complication should be avoided, and in order to reduce the work of the personnel the machinery should be capable of being easily taken care of. The facility of overhaul and the reliability of all ap- purtenances put on board must be Le cardinal feature in developing the design. ENGINES. To secure engines for these vessels which will at the same time be light, thoroughly reliable and capable of being installed in the limited space available, is a problem of no little magnitude. These considerations have brought forth the problem of the turbine engines. The turbine will be better adapted for installation in the scouts than perhaps on any othér type of naval vessel. In order that a comparison of the best possible install- ation may be drawn, the present plan is to install recip- rocating engines in one vessel and Parsons and Curtis turbines in the other two. The turbine installation will at once bring forth the question of multiple screws. From a tactical standpoint the best arrangement for the tur- bines seems to be three screws each operated by a separ- ate and independent turbine. With two screws it will be very difficult to get the ne- cessary propeller surface to handle 8,000 I. H. P., and two propellers on a single shaft does not lend itself to good propulsive efficiency. Another advantage of the three Screw arrangement is that the wing screws only would need to be arranged for backing, and the center one could be used for great speed only. In this way very good pro- pulsive efficiency is possible, and there is not such a great 'risk of lack of economy at low power. The plan decided upon is one. vessel Parsons turbine 4 screws, one vessel Curtis turbine two screws. : With reciprocating engines in the scouts no steam jack- ets are to be fitted owing to necessity for lightness and the somewhat questionable gain in economy due to jackets, and also difficulty sometimes experienced in cutting cy- linders due to the inefficient cylinder lubrication while jackets are in use with high pressure steam. A somewhat larger ratio of cylinders is also to be used, and a larger area of L. P. for the horsepower is thus caused by provid- ing an engine designed to expand the steam about 11 times at full power instead of 7 or 8 times as had been the usual practice in man-of-war. An engine 28%-in. H. P. x 45-in. I. P. x two 62-in. L. P, and 36-in. stroke, 200 revolutions is contemplated. A still larger proportioned L. P. cylinder is desirable for purposes of economy, but the general disinclination to depart from former practice to any great extent has operated to take a half way stand in this re- spect. It is only by providing a large L. P. wn that is capable of allowing steam used to expand a great many times--that good economical results can be obtained. In the design of engines special care will have to be taken that working parts are stiff and strong; that bearing surfaces are ample and that a stiff framing is obtained. The valve gear will be of the Stevenson type, the H. P. - valve 16%4-in., two I. P. 18%4-in. and two L. P. 25-in. all of piston type. Special provision as to lagging of cylinders is to be made so that losses from radiation and liquefaction may be reduced as far as possible. BOILERS. The boilers must be of a design where lightness as well as reliability are obtained, the furnaces arranged so that coal can be readily brought to the fires, the fires easily worked and cleaned and the ashes disposed of. The main supply bunkers should be directly abreast the fire rooms so that the arduous labor of taking coal from bunkers may be reduced to a minimum. The total coal capacity will be something over a thousand tons, A consideration of the various types of boilers will result in the choosing of boilers of a modified Normand type, having the tubes arranged to form baffles so that the products of combuston have a double pass among the tubes. With these boilers the uptakes are at the back and baffling is arranged so that the flames enter at the back, come forward, turn and then go back to the uptake. The tubes themselves form the baffling. Thus all special