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124 crete to a thickness of about 4 inches. But the one example of concrete construction that has come in for more notice and comment perhaps than any other early attempt is that of a barge built in 1910 for use on the Welland canal, Canada. This barge was named the ProNreErR and has been used principally to carry stone. The barge measures 24x80 feet and has a draft of 7 feet. At times, whole carloads of stones from dump cars have been dropped upon its deck from a 12-foot trestle, without injury to the vessel. In 1910, builders in Hol- land continued their output of con- crete barges with considerable suc- cess. A special design of concrete lighter for extensive use on the Dutch canals for the transport of ashes and other refuse was designed. These lighters are 46 feet 8 inches long, and 10 feet beam. They have a carrying capacity of 15 tons. Builds Several Scows In 1912 the First Concrete Scow Construction Co. built a 500-ton con- crete scow for the Arundel Sand & Gravel Co., Baltimore. Several scows and barges of this type have been in use for four years or more on Chesa- peake bay or tributary waters in the vicinity of Baltimore. The same year Johannes Lescher of Dresden, Ger- many, launched a concrete sailboat. She has been subjected to severe handling but thas given excelkent service. _ The year 1912 marked a revival of interest in. concrete boat construction. The Gabellini method of construction was used in the building of a con- crete barge at Mobile, Ala., which has met with rough treatment in the Gulf. The barge is now being used to transport fuel oil on waters ad- jacent to the Gulf’ of Mexico, A concrete barge, 100 feet x 28 feet, was built for use on the Manchester ship canal, England. She carries sludge pumps, boilers and fuel. Since 1912 many concrete barges have been in use on various English canals. Four concrete pontoons were built on the Panama canal in 1914. Four more were built in 1916. These are used as landing stages for small steamers. A harbor pontoon was built of con- crete in 1914 by the Sydney Harbor Trust Co., Sydney, New South Wales. This is 100 feet long, ranges in beam from 53 to 67 feet, has a draft of 7 feet 9 inches and a total displacement of 783 tons. It has been subjected to severe treatment from the ferries using it as a landing stage. In August, 1917, a 200-ton concrete power lighter was launched at the plant of the Porsgrund Cement Cast- ing Works, Porsgrund, Norway. The THE MARINE REVIEW Porsgrund plant builds its boats bot- tom up, an internal mold being used which is made in units that can read- ily be taken apart and reassembled. The vessel is launched in the same position in which built and by taking advantage of a special design of in- terior compartments, a small amount of water is admitted so that the ves- sel, soon after launching, rights it- self. But probably no company made greater strides in the use of con- crete. for building ships than the Fougner Steel Concrete Shipbuilding Co., Moss, Norway, This company developed a type of 100-ton concrete lighter which is used by the Nor- wegian navy. Among other works of the Fougner company are concrete drydocks. The first dock built by this company accommodates boats up to 75 feet long by 25 feet wide and has a lifting capacity of 100 tons. This company built a 200-ton con- crete cargo vessel in the summer of 1917, which vessel shortly afterward made its first trip from Norway to England. The boat is driven by a 70-horsepower motor and_ carries enough fuel for a trip from Norway to England and return. In 1918 England also took up con- crete boat construction in earnest. France began to standardize her con- crete shipbuilding and in Spain work was begun on vessels ranging in size up to 6000 tons. At the same time, the United States showed its courage by building the 5000-ton cargo boat FairH. First Large Ship The Fairu, first of the large cargo boats built of concrete, has afforded shipping experts an opportunity to study the commercial possibilities of this method of marine construction. In a measure the FarrH has indicated the limitations of concrete ships although the concrete advocates are not entirely satisfied. This vessel has been in con- tinuous service for nearly a year, en- countering the -severest weather and maintaining an almost perfect record. She has made a better record than some of the steel boats put together in record time. Since building the Fariru, rapid strides have been made in the improve- ment of concrete craft construction. Practical studies have been made with strains and stresses and the lines of concrete ships have been altered in ac- cordance. Furthermore, a lighter and stronger concrete has been successfully developed and demonstrated. New methods have been successfully intro- duced in the building of the vessels, making possible unexpected reduction in total weight. . Standard concrete weighs approxi- mately 150 pounds per cubic foot. ® _for the purpose of proving that con- March, 1919 This was good for structural pur- poses but it has been desirable to obtain a lighter weight for marine construc- tion in order to compete with steel. Only by so doing could the dead- weight of the ships be brought to a competitive relation with steel con- struction. The FairH was reinforced much more securely than ordinary con- struction work. Some authorities think she has too much reinforcement. The concrete experts made many experi- ments with numerous substances and finally fixed upon a burnt shale-clay. This resembles in appearance certain volcanic rufas of the Pacific coast. The basic clay from which this marine con- crete is produced is said to be found in various localities. Practically iden- tical clay is found in Alabama, New Jersey, Missouri and California. It can be burned in any modern kiln and its production is comparatively simple. Weight is a Detriment In the average cargo ship built of steel, the deadweight is from 70 to 75 per cent of the displacement, when taking into account as weight of ship all spars, fittings, deck houses, anchors and chains, auxiliary engines and tanks, but not boilers, engines or coal. In the wooden ship the deadweight is approximately 60 per cent of the displacement. It is evident, from the difference in weight of materials, that the chief difficulty has been to design a ship of concrete that will give a relationship between deadweight and displacement approaching that of steel. Experiments in burning lighter weight concrete have been conducted crete ships can be made commercially successful, that the weight of the ship can be such as to provide a reason- able deadweight or cargo capacity in | z relation to the displacement. Experts have been called together to. study the questions of design.: It was determined that concrete mem- bers could be designed to stand the traverse stresses just as well as steel members. Steel reinforcing was de- termined upon, however, to take up the longitudinal tensile stresses, whereas concrete assisted by the steel was relied upon to take the com- oe pressive longitudinal stresses. The experts decided that concrete had enough elasticity for the work in hand. These were the points deter- mined upon prior to the building of large. cargo boats of this material. Actual experiments have altered the opinions of many experts since. The Fairu, for instance, was found to set down close on the water. She did not ride the waves like a steel ship and therefore there is a great modi- fication in the strains and stresses in