CONCRETE SHIPS. For vessels of mod erate size, reinforced concrete has taken its place as a real shipbuilding material. It pos sesses obvious advantages for the building of many useful types of craft. Among its recom mendations are simplicity and rapidity of con struction, the readiness with which repairs can be executed, high resistance to strain and shock, incombustibility and fire-resistance, relatively low cost and the virtual elimination of main tenance charges. Experience appears to show that the skin-resistance of a reinforced con crete vessel to passage through water is slight, owing to the smoothness of the surface and the absence of joints, and the ease with which scraping can be effected.
Reinforced concrete lends itself to the most modern developments in shipbuilding design, and although the skin of the hull must neces sarily be thicker than when steel plates are used, it need scarcely be thicker than would be the case if timber were employed. Assuming three inches to be the thickness adopted, the weight per square foot would be less than that of steel one indh thick. Therefore the question of dead-weight does not appear to constitute a very serious objection, especially in view of the fact that the weight of the hull of a vessel is small in oomparison with the weight of equip ment, fittings and cargo.
After America's entry into the war in April 1917, the pressing need for ships and the ex isting congestion in American shipyards led marine engineers to consider the possibility of utilizing other materials than wood and steel for shipbuilding. The most promising alterna tive was found to be reinforced concrete. Its application to the construction of ships was at once studied intently by prominent -engineers of Britain and America. Fortunately valuable pioneer work in this field had been proceeding successfully for a decade or more and showed the way along which successful development was possible.
The first example of what we know as reinforced concrete was a rowboat built in 1849 by M. Lambot, of Carces, France. The process of construction was patented and M. Lambot exhibited his work at the Paris Exposition of 1855. The French government investigated the work of M. Lambot in 1850, but, as usual, further development was left to private initiative. In 1899, Carlo Gabellini, of Rome, Italy, began the construction of concrete scows and barges. His process had been so developed by 1905 that a 150-ton barge was constructed for the city of Civita Vecchia. The following year another barge was built for the military harbor at Spezzia, for the use of the Italian navy. This latter barge before accept ance was put to the severe test of being driven against some piling and afterward being rammed by a steel towboat. Results of these tests were so satisfactory that construction of similar boats and barges followed.
Methods of In the Gabel lini method the first step in °laying down° these vessels consists of placing reinforcement for the keel and ribs. This reinforcement, which usually consists of round steel rods, is then covered on the outside with-inch wire mesh, to which a 1-inch coat of cement mortar is applied by hand. Next a somewhat thinner coat of mortar is placed on the inside, follow ing which forms for the ribs and keel are put in place and concrete deposited for these parts of the vessel. These ribs run both longitudi nally and transversely so that a checkerboard arrangement results, the pockets being 10 inches deep and the ribs about 2 inches wade. Over these ribs %-inch wire mesh is placed with a thin mortar covering plastered on. Finally a third and coarser wire mesh is pressed into the soft mortar and the entire surface troweled over. Thii completes the hull. Bulkheads axe
next concreted and the boat finished with a wooden sheer stralce and gunwale.
The first concrete boat in Holland was built in 1887 by the Fabrieck van Cementljzer Werken. This firm first built barges up to 11 tons capac ity, which proved so successful that plans were elaborated resulting in the building of barges 64 feet long and 14 feet be-am, of 55 tons capacity. Briefly, the system of construction consisted of building longitudinal and trans verse bulkheads spaced approximately on 6-foot centres, thus providing a cellular construction, which made the ship practically unsinkable. German shipbuilders, m 1909, at Frankfort-on the-Main, constructed a concrete freighter of 220 tons. Simple fortns were set up and con crete placed between them. A concrete sail boat was built in 1912 by Johannes Lescher of Dresden. It embodied the latest principles of sailing vessel construction as to shape of hull, etc. In 1914 the Sydney Harbor Trust had con structed a pontoon of reinforced concrete for use in Sydney Harbor, N. S. W. It is 110 feet long, 53 feet 3 inches wide at the bow, 67 feet 7 inches at the stern, has a draft of 7 feet 9 inches and deck area of 6,000 square feet. The total displacement is 783 bons. Concrete barges have been in use for some years on the Man chester Ship Canal, and one on the Well-and Canal has successfully withstood very severe tests since its installation in 1910. Concrete bargts built on the Panama Canal in 1911 proved good examples of what service such barges oould render under adverse conditions. In this case concrete wa.s selected as the con struction material because no skilled labor for steel or wood ship construction was available, nor could steel plates nor suitable seasoned timber be obtained within the time requirecL Concreting materials were at hand in large quantity and the expediency of using concrete suggested itself as a happy solution of the problem. Concrete barges have been con structed also and placed in successful opemtion at Baltimore, Md., and Mobile, Ala.
In 1917 a concrete lighter was built at Pors grund, Norway, and its success led to the con struction of larger ships at the same plant. In the same ear a 300-ton concrete motorship was built in land for coastwise and channel Lit traffic. At e end of the first half of 1917, 20 or more barges and ships of similar were in use on the Paris ship canal. CanatT came forward in the same year with a concrete ship proposed for lake traffic. A concrete ship ap proicunating 5,000 tons was built for trans Pacific service at Redwood City, Cal., in 1917, and a New York company in the same year built a 700-ton concrete barge, and in 1918 had contracts in hand and work progressing on a number of similar vessels. Norway came to the forefront in this field in 1917 in the numbers of concrete barges, lighters and ships varying from 200 tons up to 3,000 tons, launched. Some of these are in ocean traffic between Norway and England. The year 1918 saw rapid ad vances in the construction of ooncrete ships, due to the great necessity of overcoming the losses in merchant tonnage through Germany's submarine warfare. This development has been chronicled in the daily press and in the periodicals of the nation. Consult (Concrete Ships) (issued by the Portland Cement Asso ciation, Chicago 1918), from which the fore going account has been compiled; Concrete and Constructional Engineering (Vols. XI, XII, XIII, London 1916-18); Marine Review (Cleve land, August 1917) ; Scientific American (28 July 1917; 17 Nov. 1917); Shipping Illustrated (New York, 23 June 1914; 18 Aug. 1917; 29 1917; 20 Oct. 1917); The London Times (Engineering Supplement, 25 May 1917).