RUDDER TRIALS, U. S. S. STERETT. 305 



jigger and spring balance to an initial stress of 300 lbs., which was the basis 

 of reference for the force curve through the trials. 



Three turns were made at each helm-angle; four different helm-angles 

 were used at each speed, and there were five speeds ahead, in addition to 

 "meet ship" turns (Table V) and full-power and reduced power backing 

 turns. The total number of turns made was 74, and the total time required 

 was seven hours. 



The "meet ship" turns consisted in steadying on a course at prescribed 

 speed, then putting the helm first port a certain number of degrees, then 

 starboard. Continuous records were made and maximum and "steady" 

 stress obtained for various conditions, such as "meeting" the ship, with star- 

 board helm immediately after the helm had been put aport; and "meeting" 

 her at various intervals of time after the ship's head had begun to swing to 

 starboard. 



Backing turns were made both at full power and at reduced power. 

 These are described in detail in Appendix VII. The backing turns at full 

 power are of particular interest because they give twisting moments more 

 than 1.5 times as great as the maximum moments obtained on the turns 

 at the highest speeds ahead. 



ANALYSIS OF RECORDS. 



CURVE Df^«wr< 6Y RECOROIfHC SfeftP^ 



Figure A shows the force diagram obtained from the continuous record 

 given on Fig. 9, Plate 119, with the scale of abscissae reduced to one-quarter. 

 The instant the helm starts to move, in beginning a turn, the force recorded 

 on the dynamometer begins to rise and reaches a maximum at about the 

 instant the helm reaches its maximum angle. During this time the ship 

 first gives a slight kick to starboard (assuming helm put to starboard), then 

 starts to turn to port. As she continues to turn, the tension in the tiller- 

 chain falls off somewhat and then maintains a practically uniform or " steady ' ' 

 value after a swing of 40° to 50°. The ship then turns uniformly in her 

 normal turning circle, and as there is practically no further variation in the 



