200 report — 1877 



Report of the Committee, consisting of James R. Napier, F.R.S., Sir 

 W. Thomson, F.R.S., W. Froude, F.R.S., J. T. Bottomley, and 

 Osborne Reynolds, F.R.S. (Secretary), appointed to investigate 

 the Effect of Propellers on the Steering of Vessels. 



Since the meeting of the British Association held in Glasgow last year, the 

 Ccmmittee has been able to carry out some further experiments on steering 

 as affected by the reversing of the screw. 



The largest vessel experimented upon last year was the barge No. 12, of 

 about 500 tons, and it appeared, on comparing the behaviour of this vessel 

 with the behaviour of those of smaller size, that the larger the ship the more 

 important would the effect of reversing the screw become. This view has 

 been completely borne out by the experiments of this year, made with one 

 vessel of 850 tons and another of 3594 tons. 



In May last the 'Melrose,' a new vessel belonging to Messrs. Donald 

 Cnrrie & Co., was tried at the instance and under the superintendence of Mr. 

 James R. Napier. The ' Melrose ' is 228 feet in length by 29 feet in breadth, 

 and 16 feet 3 inches hi depth. She is 850 tons gross register ; her propeller 

 makes 90 revolutions per minute with the vessel going at a speed of 



lOf knots. 



The following is Mr. Napier's report of the trials:- — "These expciiments 

 were made on 3rd of May 1877, between Wemyss Bay and Rothsay. There 

 was little or no wind; the sea was glassy smooth. The draft of water was 

 9 feet 1 inch forward, and 12 feet 5 inches aft ; the diameter of the propeller 

 was 11 feet G inches, the pitch 14 feet 3 inches, it had 4 blades and was 

 ri^ht-handed. The maxinmm speed at the nautical mile was 10| knots ; but 

 the speed was about 10 knots when the trials were made. 



"A trial was made with the rudder said to be amidships, and the ship's 

 head turned to starboard : but it was found afterwards that the pointer on 

 the bridge had been misplaced, and, as it was difficult at the time to ascertain 

 the rudder's position, the result was uncertain. 



•■'First mock collision trial. — The vessel was steaming about 10 knots when 

 the telegraph bell warned the engineer to stand by his engines, and shortly 

 after the bell was rung for him to reverse at full speed (no intermediate 

 order to slow or stop being given) ; in 15 seconds after this order was given 

 the engines began to reverse, and in 2 minutes 15 seconds after the giving 

 of the order to reverse, the forward motion of the ship had entirely stopped. 



"At the instant that the engineer below telegraphed to the captain on deck 

 that his engines were reversing, the captain gave the order " Hard aport" 

 which was quickly obeyed by the two men at the week The vessels head 

 almost immediately commenced turning to port, and when the ship's way was 

 stopped, or about 2 minutes after the order to port was given, the vessel's 

 head had turned 26 or 2S degrees to port._ 



" Second mock collision trial. — Every thing was done in the same manner 

 as in the first trial, except in this case the order was to starboard hard. 

 The vessel's way was lost in about the same time. Tlie vessel's head com- 

 menced to turn to starboard cdmost immediately after the enr/ines began to 

 reverse, and when the forward way was lost, her head had gone round 40° to 

 starboard. 



