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PG-10 Annapolis

The Annapolis, Marietta, Newport, Princeton, Vicksburg, and Wheeling, were so-called "composite ships," having steel frames and upper works combined with wooden bottoms. All of these each had a displacement of about 1,000 tons, and most of them carry main batteries of 4-inch guns. The gunboats are especially adapted for service on inland waters, alike of home and foreign stations. Their defensive power is small, their only armor being a light protective deck, while even this is omitted in the composite boats. They have good offensive powers, however, their batteries, while of small caliber, being of high power. Their speed varies from twelve to over seventeen knots, while their light draught enables them to cruise in waters which heavier vessels cannot enter, and provides a means of escape when chased by heavier craft.

The ordinary iron or steel war-ship has one constant source of trouble, the accumulation of barnacles and marine vegetation, which gather thickly on their bottoms, checking their speed and demanding frequent docking, with its cost and loss of time. The composite gunboat is designed to overcome this trouble, by the use of wooden planking to form the under-water hull. On this a sheathing of copper is placed, since the marine animals and plants avoid this metal. If greater strength is required, there may be an inner sheathing of steel, the whole being joined together by composition bolts to prevent galvanic action. Vessels of this class will be of great utility in stations remote from docks, such as the Alaskan rivers and seas.

The launching of the Vicksburg and Newport took place at the Bath (Me.) Iron Works, December 5. Miss Addie Trowbridge, daughter of Mayor Trowbridge of Vicksburg, Miss., christened the former; and Miss La Farge of Newport, R. I., a granddaughter of Commodore Perry, the latter. These gunboats are composite in structure, having steel frames plated with steel above the water-line and planked below, the planking covered with copper; this arrangement permits of uninterrupted cruises of seven or eight years. The total cost will be $1,460,000, and they will be ready for sea early in 1897. On December 23, 1896 the gunboat Annapolis was launched at the Crescent shipyards at Elizabethport, N. J. Miss Georgiana Patterson Porter of Annapolis, Md., a granddaughter of the late Admiral Porter, was selected by her townspeople to christen the vessel. Like the Vicksburg and Newport, the Annapolis is a composite structure, and all the wood had been fireproofed.

The new gunboat Annapolis, which was the first to be completed of the six composite hull boats ordered by the Government early in 1896, was given its official trial of four hours at full speed on Long Island Sound on April 22, 1897. This gunboat is notable as being the first US Government vessel of large size to be fitted with boilers of the water-tube type exclusively. Other vessels have been built within a few years in which the Scotch type and the water-tube boilers have both been used in connection with each other.

The Annapolis was built at the Crescent Ship Yard, Louis Nixon, Manager, Elizabethport, NJ, and the boilers were furnished by the Babcock & Wilcox Co. of New York City, whose works are also at Elizabethport. The same type of boiler has also been adopted for the gunboat Marietta.

In this boiler the water tubes are all straight, placed at an angle of 15 with the horizontal, and expanded at each end into forged steel headers. Openings are provided in these headers opposite the ends of the tubes, through which a thorough examination of each tube may be made, and the tubes cleaned and renewed when necessary. By means of a steam jet inserted between the headers all deposits of soot may be removed from the exterior of the tubes. Surmounting the sections of tubes is a steam and water drum 42 inches diameter and io feet long; all openings leading into and out of drum are 4 inches diameter. Steam to 200 pounds pressure can be raised from cold water in half an hour, this being a most important feature in boilers for a war-ship. The boilers are designed for a working pressure of 250 pounds.

The principal dimensions of the Annapolis and of its steam equipment are as follows: Length, 204 feet; width, 36 feet; depth, 23 feet 3 inches; displacement on a draft of 12 feet, 1000 tons; boilers, two, each 94 square feet of grate and 3600 square feet of heating surface; ratio of grate to heating surface, 1 to 38.3; engine, triple expansion, with cylinders 15, 24^ and 40 inches diameter, 28 inches stroke; contract speed of vessel, 12 knots with 800 IHP. The builder's trial showed that 900 IHP could be developed under natural draft, with a short funnel.

On the official trial forced draft in the ash pit was used, each boiler being supplied by air from independent Sturtevant fans, the average air pressure in the ash pit being limited to i inch of water. During the 4-hour trial the steam pressure averaged 226 pounds per square inch, the minimum being 218 and the maximum 240 pounds. The draft pressure in the ash pit averaged 0.90 inch on the port side and 0.91 inch on the starboard side. The speed trial over a measured course of 48 knots, marked by nine stake boats, gave a speed in the eight divisions of the course ranging from 12.7 to 14.18 knots per hour, averaging 13.43 knots.

The maximum IHP developed by the main engine was 1400, the aver age being 1320, at 147 revolutions per minute. The collective IHP will average about 1360. Dividing 1320 IHP into 3600 square feet heating surface gives one IHP for each 2.73 sq. ft. of heating surface. Dividing it by 94 square feet of grate gives 14 IHP per square feet of grate. During the test under forced draft the smokestack did not become hot enough to burn the paint off it.

On April 20, 1898 President McKinley sent his ultimatum to Spain, and the following day Spain gave United States Minister Woodford his passports. Every ship of the United States Navy in commission, whose engines were even halfway good, had steam up. Work on the gunboat Princeton and other warships in the course of construction was hurried more than ever.

The 'Marietta' made a trip almost as long as that of the 'Oregon,' as she left San Jose de Guatemala on March 16th, 1898 and arrived at Key West on June 4th, having been under steam continuously for nearly three months and having covered a distance of over 13,000 miles at an average speed of 9.2 knots. As this came after the vessel had already been in service for nearly a year, the record is very creditable. At the expiration of a 12,000-mile voyage from Boston to Cavite, the boilers of the United States gunboat " Marietta" needed only a few grate bars. This run was in addition to the war service of this little vessel, and the memorable trip around the " Horn " in company with the battle ship "Oregon."

The gunboat Vicksburg, sister ship of the Newport, had her official trial trip on May 29 off Bath, Me., and developed a speed of 12.68 knots an hour, which is about four-tenths of a knot better than the Newport made over the same course.



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