ON THE STEERING OF VESSELS. " 69 



engines been kejit on ahead, the effect of reversing was to turn her through 

 90° from the iwsition she would have occupied had the CDgincs kept on 

 ahead. 



E.vpeviments with the Steam Yaclit ' ColumJxi,' hehnginr/ to His Grace the 

 Duke of Arfjyll, June 29, in Gare Loch, the weather very fine, with little 

 wind. 



The draught of the vessel was 10 feet aft and 8' 2" forward. She was 

 fitted with a Griffith's screw 7' 1" in diameter and 12' pitcli. The experi- 

 ments were witnessed by Mr. James E. Napier and his son, Mr. Eobert T. 

 Napier. "When the vessel was going full speed ahead (about 10 knots) the 

 engines were reversed, and the helm immediately put to starboard ; the ves- 

 sel turned to starboard until her forward way was lost, the time between the 

 reversal of the engines and the stopping of the ship being about 1 minute. 



When the vessel was going full speed ahead the helm was set to port, and 

 shortly after the screw reversed. The vessel turned to starboard at first, 

 and then to port until all way was lost. The turning to starboard at first 

 was the natural result of the helm having been ported before the screw waa 

 reversed. 



In the trials on this ship no measurements were made of the angles 

 turned through. The direction of turning, however, was the same as be- 

 fore, the reversing of the screw at once reversing the eflfect of the rudder. 



In all three of these vessels, therefore, the same effect on the steering waa 

 produced by the reversing of the screw when the vessel was at full speed. 



The importance of this effect may perhaps be best seen from the diagrams 

 (Plate I.), showing the various positions occupied by the ' Valetta ' and the 

 barge compared with those they would have occupied had the screws not been 

 reversed. 



In these diagrams the directions of the vessels correspond with the actual 

 measurements during the trials ; the positions and distances travelled being 

 estimated from the known speed of the vessels. It had been the intention 

 of the Committee to use one of Mr. Napier's pressure logs in order to ascer- 

 tain exactly the positions of the vessels during the trial, but this intention 

 was not carried out. 



DiagTam 1 shows the courses run by two ships after the reversing of the 

 screw until they had lost all way compared with the courses they would have 

 run had they continued under full steam, the helm being hard to port. 



A glance at this diagram is sufficient to show what a fatal mistake it must 

 be when a collision is imminent to reverse the screw, and then use the rudder 

 as if the ship would answer to it in the usual manner. 



But perhaps, as regards collisions, the most important result is that 

 shown in diagram 2 — namely, the positions of the ships when they have not 

 lost more than half their way, and when, as regards the distance run, the 

 effect of reversing the screw is but small. 



As is shown in this diagram, it appears that whether the reversing of the 

 screw reverse the action of the rudder or not, the rudder is nearly powerless 

 to turn the ship, and that she will turn not only more rapidly, but in less 

 room when going full speed ahead. 



Before closing their Eeport, the Committee desire to express their thanks 

 to the Earl of Glasgow, the Clyde Navigation Trust, and His G race the Duke 

 of Argyll, for the use of their vessels, and to the officers and crews who 

 assisted in making the arrangements and conducting the experiments. 



