CONCRETE SHIPS.

Auckland Star, Volume XLVII, Issue 239, 6 October 1916, Page 7

CONCRETE SHIPS.

METHOD OF MAKING. BIG FUTURE TOSSIBILrriES. The announcement by cable hi last evenirrr's issue of the "Au<*kland Star" that a vessel constructed of concrete, excepting tor steel ribs, had been launched in Sweden is a matter of considerable interest to the shipbuilding trade. As radicated by Mr. John WHsoni in an interview yesterday, barges, pontoons, and even a yacht have been built of reinforced—-concrete for- some years past. As a. matter of fact, reinforced concrete barges were used for removing the material when the Panama Canal was being excavated They were selected 'ijeeaase tihev could be built on the spot. at a nrueh less cost than steel ones, and only slightly in excess of wooden barges. It "is also claimed that the expense ot maintenance of concrete barges is practically nil. The barges used on the T'hg.Tnfn when in course of con- ; struction had wire netting reinforcement at the-.bottom and sides. Rods previously bent to the proper shape were securely wired to the mesh, and the skeleton of the barge was plastered with hydraulic cement mortar, to which had bei;n added 35 per cent, of lime. The , plaster was laid on the outside of the 1 wirie mesh, in two coats, aggregating half an inch in thickness, and the inside was then plastered thick enough; to cover the reimVjrcmg rods, the result being a slab aboai; 2i feet in thickness. The plaster was next rubbed down to a hard, smooth surface, especially on the outside. Upon the completion of the shell the reinforcement and forms were placed to the bulkheads Hud cross frames, being securely attached to the shell by wires a quarter of an inch wide, fixed to hooted rods previously inserted in the shell for thai purpose. The frames and bulkheads were then _ filled with concrete- to the bottom of the deck slab, and finally the later was placed in the usual Branner and given a trowel finish. Woodea forms were used throughout, the interior form work being built in collapsible sections, so as to be easily removed as the work advanced. These barges carried a dredging plant, motor, and equipment Teigbing about 6000 lb. Reference was made by Mr. John Wilson to a concrete yacht built in America over a decade ago. An article iv the "New York Evening World/ referring to this boat, states.- "While Europe is experimenting to test .the feasibility of concrete boats, Baltimore actually has demonstrated it. A con- j crete sailing vessel bas been in commission for eleven years. The boat is the Gretchen, built and owned by Daaiiel B. Banks, consulting engineer of the Fire Board. She ia a. two-masted schooner yacht 65ft long, with 16ft beam, and draws 14ft of water. When in Baltimore the Gretchen is one of the fleet of the Yacht Chub. She has- accommodation for a dozen persons, is easy-riding because of her weight, and while of only moderate speed in a light wind, she outstrips everything in sight in a stiff breeze and a heaw sea. Mr. Banks explained regarding bis boat: *T knew that concrete would be just as buoyant as steel, so I had a framework built with hundreds of lfcrht steel rods for reinforcement, exactly as buildings axe constructed. It may be mentioned that some years ago the Gretchen was driven on the rocks. A steel boat -would have had a hole stove in her side, but the concrete did not show even a scratch. ' While in Auckland pontoons are still constructed pf wood, the Sydney Hanbour Trust has in use one made of reinforced concrete.