Page:Popular Science Monthly Volume 91.djvu/574

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��Popular Science Monthly

��which is shown in the illustra- tion on page 556 of this issue. This has been in use for more than four years and is still giv- ing satisfactory service.

���The Cement-Gun Rod Re-enforcement The T-hars used in the side of the concrete ship are made by shooting the material into place. The spacer bars have holes through which are inserted short rods with hooks to carry the horizontal bars on which the three layers of re-enforcing wires are hung. By this means the wire is kept always in its proper relation

��Advantages of Concrete Ships

Re-enforced con- crete barges seem to have given good service, so that the present problem of building self-pro- pelled ships of four- or five-thousand tons capacity is one of construction methods and of tak- ing care of the severe strains of ocean travel and the vibra- tion of the engines. These conditions met, concrete has many advantages not enjoyed by

either wood or steel. Concrete ships would be fireproof and would require less main- tenance than steel vessels because of the elimination of scraping and Hatch coammq

painting to avoid deteri- oration due to rusting. Also, their bottoms would need to be cleaned less often be- cause sea growths do not attach themselves so readily to concrete as to steel and wood. Some advocates of the concrete vessel claim that it can be built at less cost than a ship of steel or wood, that it has a

��longer life than either and that less skilled labor is re- quired. While this may be true in the case of small barges and the like on which actual cost figures are available, it remains to be proved in the case of the large ocean- going freighter. The standardized cargo boat of either steel or wood as planned by our Shipping Board will be built in much less time than any other ships constructed hereto- fore.

Following previ- ous re-enforced con- crete construction methods, the pro- posed concrete ves- sels may be built along two general lines — one by the use of forms, as in most building work, and the other by the

��A Simple Con- crete Barge

Below: Note the single side hull and double bottom construction; also the form of the three vertical deck sup- ports and the beams

���Transverse Section

Through Deck and

Part of. Hatch

Above we have a good illustration of the man- ner in which the con- struction of the concrete boats will follow the usual methods of con- crete building in regard to re-enforcing. Note the wood bumper stringer bolted to the concrete hull to ward off collisions, which might tend to crack the concreteand cause a leak

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