310 RUDDER TRIALS. U. S. S. STERETT. 



"meet ship" turns. 



On these turns, the results of which are tabulated in Table V, the helm 

 was first put over to port, and then, after a definite interval of time, to 

 starboard. The maximum tension recorded by the dynamometer occurred 

 in all cases just after the helm had been started from port to starboard, i. e., 

 practically at the instant of "meeting ship." A correction for friction was 

 applied, corresponding in each case to the maximum recorded starboard 

 helm. The twisting moment was computed from the resulting maximum 

 stresses, and compared with the maximum twisting moments obtained by 

 interpolation from the curves of Fig. ii, Plate 121, for the same speeds and 

 helm-angles on the regular turns. The moment developed on "meeting 

 ship " appears to be, on an average, about 12 per cent greater than on normal 

 turning. 



The interval of time during which the ship was allowed to swing under 

 port helm, before "meeting" her, varied from 3! seconds to 45 seconds 

 apparently with no considerable difference in the effect on the twisting 

 moment developed. 



The record of revolutions per minute showed that on the initial swing 

 to starboard {i. e., with port helm), the revolutions per minute of the inboard 

 screw were about 10.8 per cent less than those of the outboard screw, and 

 that on the subsequent turn to port after "meeting ship," they were about 

 8.4 per cent less. 



BACKING TURNS. 



Two turns were made with engines backing at full power and two with 

 engines backing at reduced power. On the first full-power turn, the ship 

 being dead in the water, the engines were reversed and the helm simultane- 

 ously put over to 32° port, before the ship had gathered stem way. The 

 force curve obtained was similar in shape to those for turns ahead; but the 

 maximum tension recorded, 13,600 lbs., corresponding to a twisting moment 

 of 145,000 lbs. -feet at the rudder head, was 1.53 times as great as the 

 maximum tension recorded on the previous turns, corrected for friction. 



On the second full-power backing turn, the engines were first reversed 

 and the ship allowed to acquire considerable stemway before putting the 

 helm aport (32° maximum). On this turn the maximum tension recorded 

 was 13,980 lbs., corresponding to a twisting moment of 149,100 lbs. -feet at 

 the rudder head. This is nearly 1.58 times the maximum tension on the 

 turns at highest speed ahead. In both of the full-power turns, the vibration 

 was very violent, and no correction for friction has been applied to the 

 tensions developed in these turns. 



A detailed description of the backing turns is given in Appendix VII. 



