142 • KEPORT — 1875. 



harbour, that on her entering between the piers the. engines were reversed, 

 and that the ship turned, under the influence of the current, in spite of her 

 rudder ; so that Capt. Pittoch, in his letter to the ' Times,' attributed the 

 accident entii'ely to her failing to steer at the time. 



On reading of the accident I thought it would be a good opportunity .to 

 call attention to the subject of steering steamers ; and I wrote a paper, which 

 was published in the ' Engineer' of June 4th, 1875, in which I explained 

 why the act of stopping a ship must necessarily affect her power of steering — 

 j»ointiag out that when a ship is stopping the water will be following her 

 stern relatively faster than when she is moving uniformly, and consequently 

 that the eifect of the rudder will be diminished ; • that the longer the ship 

 the greater will be the diiference; also that this effect is greatly increased 

 when a ship is stopping herself with her propellers, as was the ' Bessemer ' ; for 

 then not only is the retardation of the vessel much more rapid, but the 

 water hafe a forward motion imparted to it by the propellers, which motion, 

 if the propellers are near the rudder, may be greater than that of the ship, 

 under which circumstance the effect of the rudder's action will be reversed. 

 Since publishing this paper in the ' Engineer ' I have canned the investiga- 

 tion further ; and the object of the present paper is to give an account of 

 some experiments on model boats driven by screws, and the conclusions to 

 which these experiments have led me. 



Two models were used in making these experiments ; the one 2' 6" long, 

 driven by a spring, and the other 5' 6", driven by steam. In both models 

 the rudders were broad in i)roportion to the boats. In the clockwork model 

 the rudder was almost close to the screw, there being no stern-post. In 

 the steam model there was a wide stern-post, and the rudder was an inch 

 and a half behind the screw. 



Both boats went straight with their screws driving them ahead and with 

 their rudders straight, and they both answered their rudders easily with 

 their screws going, turning in circles of from four to six feet radius. When 

 the screws were stopped and the boats carried on by their own way, they 

 both answered theii- rudders, but much more slowly than when their screws 

 were going, the smallest circle being now, as near as I could estimate, from 

 twelve to fifteen feet radius. 



In order to try the effect of the screw when reversed on the steering of the 

 spring-model, the model was towed by a cord attached (as shown in the accom- 

 panying figure) to a point T amidship about one third of her length from her 



stern, so that the towing had little or no tendency either to keep her straight 

 or turn her. The rudder was then set at an angle of 45° or thereabouts, so 

 as to turu her head to the right, towing was commenced, the boat turning in 

 a circle to the right. The screw was then started in the reverse direction ; 

 Avhereupon the boat ceased to turn to the right, and commenced turning to 

 the left to an extent depending on the slowness with which she was being 

 towed. When towed very quickly, at from two to three miles an hour, she 

 came nearly straight forward, but at the fastest speed showed no tendency to 

 turn to the right. 



