66 REPORT— 1876. 



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



W. Thomson, F.R.S., W. Froude, F.R.S., and Osborne Reynolds 



(Secretary), appointed to investigate the effect of Propellers on the 



Steei'ing of Vessels. 



[Plate I.] 



The Committee commenced operations by printing the following Circular, and 

 sending copies of it to the Admiralty and to those shipowners with whom 

 the individual members of the Committee were personally acquainted, or 

 those who in their opinion were likely to assist in the investigation : — 



" The British Association foe the Abvancement oe Science. 

 " Experiments on tlie Turning of Screw Steamers. 



" At the Meeting of the British Association in Bristol last year, a paper 

 was read by Professor Osborne Eeynolds, in which it was shown, from ex- 

 periments upon models, that in a steamer when the screw is in motion, the 

 direction in which the rudder tends to turn the ship depends on whether the 

 screw is driving ahead or astern, and is independent of the actual motion of 

 the ship through the water ; for instance, if when a ship has headway on 

 the screw is] reversed, then the action of the rudder is the same in direction 

 as that of a ship going astern ; or if the ship have sternway on, and the 

 screw be started to drive her ahead, then the rudder acts as if slio were going 

 ahead. 



" After the discussion of the paper, Mr. James R. Napier, Sir William 

 Thomson, Mr. "W. Froude, and Professor Eeynolds were appointed a Com- 

 mittee to carry the investigation further, and particularly to ascertain if the 

 same results would be obtained when the expei'imcnts were made with full- 

 sized ships. 



" In order to collect sutHcient data to establish a general conclusion, the 

 Committee are anxious to obtain the assistance of such shipowners and 

 captains of ships as may be willing to aid them. 



" The Committee accordingly ask that certain trials and observations may 

 be made, and the results, together with the name, size, tonnage, and condi- 

 tion of loading of the ship, as well as the depth of immersion of the screw, 

 the date and name of the officer in charge, may be forwarded to Professor 

 Reynolds, Owens College, Manchester, or to any of the Members of Com- 

 mittee. 



" It is also particularly requested that the kind of screw and the number 

 of blades may be stated, and whether the screw is right- or left-handed. By 

 a right-handed screw is imderstood one in which the uj^per blades move from 

 port to starboard when driving the ship ahead. 



" The following are the trials requested : — 



" Trial I. — That when the ship is going full speed ahead, the screw should 

 - be suddenly reversed and the rudder put hard over, as if to turn the ship to 

 starboard of her course, and careful notice taken as to the way in which the 

 ship turns before all headway is lost. 



" Trial II. — The same repeated with the rudder set in the opposite 

 direction. 



" Trial III. — That when the ship is going fast astern the screw should 

 suddenly be started to drive her ahead, and the rudder put hard over to the 

 same side as in Trial I. 



"Trial lY. — Trial III. repeated with the rudder. in the opposite direction. 



