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300 / UU TT SEH Loon ooo Helhiod er ep ee LV . TERETE) Floating drydock i: DP LOCKANIGL IA PONTO? MARINE REVIEW July, 1922 AMO —rn 5 ¢ s “ \ vf “ NG 4 nn, Anoonannnnn yn n 4 OPLOCROARLAARS “ S » 7 ‘7 \ “4 ¢ ee ino cunaagcocadengpp re hes uuu 4 <i “7 s aM Wethod Of Decking Intermediate Pontoon of 8000-ton capacity built at Charleston. Special features of design and construction were incorporated in this drydock Design New Type of Floating Drydock LOATING drydocks have made a place for themselves as __ efficient units in a modern repair plant. Un- der the spur of war needs and of. ex- panded American shipping activities, dry- docking equipment in this country has been greatly increased. The docks them- selves have been improved in design. An unusually interesting installation has been in successful operation at Charleston, S. C., for several years, suf- ficient time to test thoroughly the merit of the design. This dock is operated by the Charleston Dry Dock & Machine Co., formerly the Valk & Murdoch Co. and was built by this company from plans developed by the Crandall Engi- neering Co., Boston. The unit is the first floating dock of the longitudinally trussed sectional type ever built. In 1914, the Valk & Murdoch Co., engaged the Crandall Engineer- ing .Co.. to construct one of its standard railway drydocks of 1200- ton lifting capacity. The dock meas- ured 200 feet over the keel blocks, 55 feet wide and gave 10 feet draft forward and 15 feet aft over the keel blocks. It was constructed entirely of yellow pine timber with a foundation of yellow pine piles. To protect the cradle from the ravages of marine borers so pre- valent in Charleston harbor, the cradle was sheathed to high water mark with ship’s felt and creosoted boards. cradle is operated by two hauling chains and: a powerful steam operated hoist. This railway drydock was completed in 1914 and has been in constant operation since that time. Later the Charleston company decided to install a floating dock. The Crandall Engineering Co. was again engaged, this time to design a timber floating dock of 8000-ton lifting capacity. The designers having just developed the longitudinally trussed sectional dock, it was decided to install that type. The Valk & Murdoch The - Co. began the construction of this dock in its own yard in 1917. After much delay to commandeering of timber and other commodities by ‘the government, four sections were ready in March, 1919, so they were joined together and operated until August, 1919 when the other sec- tions were ready and the complete dock was joined together and put in operation. As a unique occurrence, the first dry docking operation was to lift the cradle of the railway drydock, built five years before, for inspection of the underwater portion for damage by worms. This was done by disconnecting the chains from the cradle, floating the cradle by means — of scows clamped to the deck and then lifting it on the floating dock, Upon inspection, the sheathing on the cradle was found in perfect condition and the timbers free from worms, ss This. floating dock is a marked de- parture from the usual design. 'Through the longitudinal truss system, the sections