RESULTS OF MODEL TANK EXPERIMENTS TO DETERMINE THE 



ACTION OF A SHIP BRAKE. 



By Captain Wm. Strother Smith, U. S. N., Member. 



[Read at the twenty-third general meeting of the Society of Naval Architects and Marine Engineers, held in 



New York, November 18 and 19, 1915.] 



This paper is presented with the idea of showing the interesting data obtained 

 in the model tank at the Navy Yard, Washington, for use in determining whether 

 or not it was feasible to design and install a brake on the side of a merchant vessel 

 to assist in stopping a steamer when in danger of collision or grounding. 



The question of installing such a brake is a financial one and is dependent upon 

 the lessened insurance demanded and the advertisement of such an appliance to in- 

 crease the passenger list. 



This question is not one for the naval architect or marine engineer to solve 

 and is not brought up for discussion on that point. 



In the spring of 19 lo, a set of trials was made on the U. S. S. Indiana off 

 Delaware Breakwater to determine the effect of the Lacoste ship brake. Due to a 

 lack of preliminary investigation, this trial showed very little either for or against 

 the brake and it was some time after that the writer was requested by personal 

 friends to take up the study with a view to designing a practical brake. 



After the loss of the Titanic interest was awakened to such an extent that a 

 syndicate was formed and the permission of the Navy Department was obtained to 

 make a series of trials in the model tank, and the results of these trials are now 

 presented to you through the courtesy of the Lacoste Shipbrake Syndicate. 



The Wm. Cramp & Sons Ship and Engine Building Company was kind enough 

 to furnish the lines of the S. S. St. Louis, and a model of this vessel was con- 

 structed. ; 



Three runs (Nos. i, 2 and 3) were made to determine the curve of speed and 

 power before fitting any brakes, and the successive ten runs were made with dif- 

 ferent areas and settings of the brake to determine the resistances and pressures 

 per square foot. 



The S. S. St. Louis is 536 feet in length, 62 feet 9 inches beam, and the 

 draught at load line was 28 feet for model experiments, the displacement being 

 about 17,230 tons. 



Plate 51 shows the curves of speed and effective horse-power as determined 

 under the following conditions: — 



Runs I, 2 and 3 show the speed and power curve without brakes. The suc- 

 ceeding runs were with brakes as stated. 



Runs 4 and 5 — brakes, 12 feet 2^4 inches by 14 feet at 80°. 



