Page:Popular Science Monthly Volume 91.djvu/572

 One-Piece Ships of Stone

Already a company has been formed and financed to design and build concrete ships of 4,500-ton capacity

By Joseph Brinker

���Broadside view of 550-ton concrete barge used by Arundel Sand and Gravel Company of Baltimore, Md. This picture was taken just before the barge was launched. The barge has been in use for several years

��GONCRETE ships are possibilities. They may be built in addition to steel and wood vessels to offset the acute submarine peril. According to au- thorities, the German' U-boats are sinking Allied and. neutral tonnage much faster than it can be renewed. This cannot go on. If it does, we shall lose the war. Even our Government-controlled shipbuilding program for steel and wooden ships will not produce -sufficient tonnage to offset the present U-boat toll unless this tonnage is greatly increased by the use of some new substance.

Concrete seems to be this sub- stance. Already a large com- ^.Wood ra pany has been formed and financed in San Francisco to design and build sea-go- ing vessels of 4,500-ton ca- pacity to be made of re- enforced concrete. Plans now drawn up show these vessels to be three-hundred feet long, with a beam of forty-six feet and a draft of twenty-four feet. The con- crete hull is to be six inches thick and the steel re-enforc- ing rods are to be welded together to reduce the quan- tity of steel required to a minimum by avoiding the waste from laps and bolting otherwise necessary.

It has been calculated that the steel re-enforcing for the vessel will weigh less than the bolts needed in a

��wood ship and that the completed hull will weigh less than that of a wood boat of the same carrying capacity. Allan Mc- Donald, the designer of the ship, estimates that it can be built in ninety days and that turbine engines of two thousand five- hundred horsepower will be sufficient to drive her at a speed of fourteen knots, which is considered enough to enable a boat to escape a submarine under ordinary conditions.

There is no question about the avail- ability of the concreting materials and that

���The Mid -Ship Section of a Concrete Boat

It would be made up of light steel framework with wire re-enforcing on the sides. The concrete covering is shot into place by compressed air. The bottom of the vessel is cast in forms in the usual way. Poured concrete has much less density than that shot into place and is liable to be more porous than the kind placed under pressure. A slice is shown cut out of the boat from lower deck to lower deck in order to indicate the position of the steel re-enforcing rods placed longitudinally through the framework

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