THE AUCKLAND FLOATING DOCK.

Grey River Argus, Volume VIII, Issue 597, 13 November 1869, Page 2

THE AUCKLAND FLOATING DOCK.

(From the Southern Cross.) The proposed Floating Dock, as shown by the plans prepared by Mr Stewart, A.1.C.E., will be capable of taking in a vessel 232 feet in length, of 42 feet beam, and drawing 18 feet of water. It is believed that such a dock will fully meet the ordinary requirements of the port ; and as the cost of wooden docks incr-ases in a very rapid ratio as compared wi-h increase of size, it is considered to be not advisable to incur the expenditure vhich would l>e needed for constructing a dock to accommodate vessels of tho largest size, seeing that such vessels will very rarely require docking here, The plan of construe* tion proposed by Mr Stewart, is one ranging between such docks as that at Fort Chalmers, aud pontoon docks. With the Port Chalmers flo.iting doc-k, the cost and the time necessary for clearing it of water is greatest when the smallest vessels are being dealt with : for their being no chambers or other me;tns of regulating the submersion, the dock must go down to her greatest depth, no matter what niiiy be the draught of the vessel to be taken in. Mr Stewart's plan obviates this practical defect, by the introduction, at each angle of the dock, of a "balance chamber," into which the flow of water can be regulated at pleasure. The proposed Auckland dock, including pumping gear and ballast, will have a weight of 101)0 tons, and her draught of water, whea empty, will be two feet six inches from the underside of her floor planking. A vessel weighing 1200 tons will cause a further displacement of nearly 'A feet, or less than 6 feet in all, from the underside of the lower stringers. As the gatesill will be 7 feet 9 inches above the point mentioned, a weight of 700 tons additional to the 1200 will be needed to sink the sill level with the water. In all ordinary cases, therefore, wheu a vessel has been •locked, the gate may be lowered as soon as the dock has been pumped out. In docking a vessel, when sufficient water has been let into the balance chambers to bring the sill slightly below the level of the water, the weight of the dock will bring her down until thure is 6 feet 6 inches on the sill ; and additional submersion, to just the depth necessary in each case, will be effected by admitting more water to the chambers. Thus it will be secured that only so much water as is. necessary to float the vessel into the dock shall have to be pumped out afterwards. It is proposed that the pumping power will consist of centrifugal pumps and engine, the aggregate power being sufficient to chrow 10,000 gallons of water b" feet high per minute. Supposing the dock, without a vessel ■within her, to be sunk to her extreme depth, the pumping gear would clear her of water in three hours and twenty minutes ; but, with a large vessel docked, the water would be ejected in about two hours aud a half. Estimated somewhat roughly, the coat of the proposed dock, complete, is set down at L 11,300. It may be added that the Port Chalmuis floating dock, which is 180 feet lone, was built by Messrs Murray and Co., shipwrights, of that place, on si. Provincial guarantee of eight per cent. f(>r live or six years on her total cost ; and that it was resolved she should be of the simplest possible construction, so as not greatly to burden the provincial revenues, because the Government had at the time determined to proceed with the construction of a graving dock, at a cost of L 50.000. That floating dock is admirably answering the temporary purposes for which she was built ; and ih ca. not be doubted that the proposed Auckland floating dock, with her greater carrying capacity and more economical working, will prove of the greatest advantage to the port, and also profitable to her shareholders.