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- PEARL SHELL 'panying illustration. 344 as that due to the added surface. Compared with the shipshape form, there is practically no difference in resistance between this and the sim- plified form with the corner cut off. Although time did not permit of carrying out a complete set of roll- ing experiments, some of the movdiels were tried and it was found that the effect of the sharp corner upon the reduction of rolls was most marked, and that even with the corner re- moved these models came to rest quicker than the shipshape form. The general conclusions that may be drawn are as follows: 1--Vessels of the straight fname type can be designed which will have about the same resistance as a ship- shape form. 2--lIf the diagonal line of the cor- ner be given the wrong slope, this will increase the resistance due _ to the lack of conformity with the proper stream line flow. HE steamship 'PEARL SHELL, one of the vessels built recently for the Shell Oil Co. of California and taken over by the govern- ment was constructed by the Harlan & Hollingsworth plant of the Bethlehem Shipbuilding Corp., Wilmington, Del., and is an excellent example of some of the more recent additions to the United States merchant marine. The principal dimensions of the vessel are as follows: Length overall 411 feet, beam 53 feet, and molded depth 29 feet. The gross tonnage of the vessel is 5845. The is shown in the accom- As is customary in vessels of this class the propelling machinery is located aft. The engine is of the inverted, direct acting, triple expansion type, and develops 2400 horsepower. lt THE MARINE REVIEW 3.--The effect of maintaining the square corner is to increase the bare Table II ° Particulars of Full Model Form LG with YA. C; corner Draft B/d corner-off Y.3.C. volume Coeff es Long. Coeff. . 301. 4798 .801 o 2 7 Block Coeff.. .779 .779 .785 | Mid Coeff....973 .976 .98L ong. Coef.. .791 © .788 -- .791 6" 2.66 Block -- Coeff. .766 p60. hho Mid. Coeff.. .968 72. 978 Long, Coch... 780 -- 178 ---.780 oO 3.2 Block Coeff.. .749 _ .750 = .759 Mid. Coeff... .961 .965 .974 has cylinders 29x 45x74 inches in diam- eter with a 48-inch stroke. Steam at 180 pounds pressure is supplied by three sin- gle-end Scotch boilers, located two athwartships and one forward, all having a common stokehold. Each boiler has three corrugated furnaces and 368 3-inch tubes which provide an evaporating surface of 2667 square feet. The grate furnace is 64.4 square feet. The boilers are operated under forced draft and are arrranged. to burn either coal or oil. An interesting feature of the PErarL SHELL is the use of superheated steam. The superheating of the steam is ac- complished by means of a fire-tube superheater furnished by the Loco- motive Superheater Co, New York. Each boiler has four cast steel head- = iin I é_ eal IC into the boiler tubes. December, 1918 hutl resistance, but as vessels of this form would not meed bilge keels the net result from a horsepower stand- point would be about the same as for a shipshape form. 4---Probably the best results from a resistance standpoint would be ob- tained by using diagonal line which is of a curved form in the body' plan. Australian wheat continues to arrive in sailing ships at San Francisco, the Columbia river and Puget sound ports. It is coming in vessels which carry lumber to the Antipodes and under normal conditions they would return either in ballast or with coal. A steel steamer, built at Vancouver, B. C., has sailed for Europe with 50, 000 bushels of wheat, part of it from Australia and part from Canadian fields. The Aus- tralian wheat comes in sacks and at the Vancouver elevator it is bulked and 'cleaned before being shipped to Great Britain. Sam/'s Fleet ers or collectors. These are arranged in pairs and each pair has one satur- ated and superheated header. They are connected by units of cold drawn, seamless steel tubes, which extend Each pair of units is attached to the headers by means of a clamp and stud and may -- be released by removing a single nut. Units are of the continuous type and have return bends formed integral from the tubing. The superheater provides steam at a temperature of 600 degrees Fahr. at the throttle under 'normal operating conditions. -- The extension of the use of highly superheated steam is shown by the fact that there are now more than 2,200,000 'horsepower of marine engines receiv- ing highly superheated steam from super- heaters which are of the fire-tube type. STEAMER PEARL SHELL This vessel is an excellent example of an eastern __ built cargo vessel. She was built for the Shell Oil. Co. of California and taken over by the gov- ernment, ng ,