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THE MARINE REVIEW VOL. 43 CLEVELAND OCTOBER, 1913 NEW YORK No. 10 Model Experimental Tank | What the Navy Department is Doing to Prove the Theory of Suction as Well as Improving the Lines of Ships HE § suction of the current I caused by the submerged por- tion of the hull of a warship or an ocean liner, as it leaves or en- ters the dock, is of such power that frequently the cables fastening vessels to piers have been broken and col- lisions have resulted, sinking or dam- aging one or both vessels which have been thrown against each other. This is why the testing basin de- chant vessel could be made for the same purpose. ; The reason this new idea was de- signed was the result of an investiga- tion of a collision, made by Naval Constructor David W. Taylor, in con- nection with other engineers. The steamers Prinzess Irene and Parima were going out of New York Bay. The Parima, the smaller craft, was leading, and the Prinzess Irene, gath- GENERAL VIEW OF THE TANK, ERY FOR GAGING THE SPEED, THE RESIST AND OTHER TESTS signed and constructed by the navy engineers for determining the speed of naval vessels: and best designs of hulls, which will allow the cruiser or battleship to be propelled over the water with least resistance, has at- tracted much attention among ship builders in this country, and abroad, Since the miniature model of a mer- SHOWING THE MODEL MOVING, THE MACHIN: ANCE TO THE WATER ering speed, began to overhaul her. The ships were in a comparatively narrow channel, and their courses, separated them laterally, by about 200 ft. Suddenly the Parima's stern was drawn toward the overlapping craft, when a wave caused by the suction of the Irene's rapid speed, threw the Parima against the Prinzess Irene By Day Allen Willey and caused this ship to run aground. The seeming mystery of that mishap was proved by Naval Constructor Taylor to be due entirely to reactions set up between the ships by their own wave motions, and the same effects would be caused if the craft were virtually stationary and the tide were sweeping by them at a corresponding speed. The. experiments at Washington have shown clearly that the tendency be- tween ships passing each other, as far as 200 ft. apart, or a vessel entering the harbor near the end of the pier that forms its entrance, creates a cur- rent either forward or backward ac- cording to the tide, the flow of the current depending upon the sizes of the vessels and their speed or the velocity of. the harbor current. This shows how necessary it is for ships to pass further apart as they increase in size, speed and length; and it naturally follows that the course of smaller vessels would be thrown out of line by the movements of the craft of larger dimensions and_ greater depth. Study of Currents The study of currents is made' by the employment of what is known as the "experimental model basin". The capacity of the basin is about a mil- lion gallons. It is filled with water from the city supply for Washington, which is taken from the Potomac, some miles above the: city. Before reaching the basin, the water is treat- ed with a minute quantity of alum, which coagulates with any mud pres- ent, and then clarified by passage through a sand filter of the pressure type. When working the filters to their full capacity, the operation of filling requires about a week unless the city water is unusually muddy. After filling the basin, a small stream