334 RUDDER TRIALS, U. S. S. STERETT. 



as the rudder experiments were made. That would have added greatly to the 

 value of the experiments. 



Referring to page 309, the conclusion of Wellenkamp there referred to, and 

 advanced already by Pollard and Deibout, that the rudder angle should be reduced 

 by the full amount of the drift angle, is certainly erroneous. According to an 

 analysis which I have made of numerous turning trials,* the deduction should be 

 much smaller than the drift angle. I agree, however, with the authors of the paper 

 that the deduction should probably be some function of the drift angle. 



The conclusions stated on pages 311 and 312 are certainly very interesting and, 

 notably the numerical data, are decidedly novel. Conclusion 6 points strongly in 

 favor of placing the steering engine right aft or at least in the engine-room. I never 

 could see the advantage of placing the steering engine forward, as it requires very 

 little looking after. 



Mr. E. a. SpERRY, Member (Communicated) : — I consider this paper a valu- 

 able contribution to our knowledge on the subject under discussion. Ithas, however, 

 occurred to me that the value of the results would have been somewhat increased 

 had the sheet of curves in Fig. 9, Plate 119, incorporated upon its face and actual 

 curve of the angles in azimuth made by the ship while turning in response to various 

 positions of the helm. This could have been quite easily accomplished by using the 

 gyro-compass repeater or by gyro apparatus similar in all respects to that employed 

 by the Navy Department for recording angles of pitch and roll, but so arranged as 

 to record all yawing movements, or movements in azimuth. Such an apparatus 

 has been devised whereby the angles are quite minutely traced, representing as 

 they do the circumference of a lo-foot circle, where a single degree is represented 

 by about an inch travel of the pen. A curve of this kind would have served to 

 give us the exact characteristic of the curve of response at various rudder angles, 

 together with the time lag and also the relative resulting velocities of movements 

 in azimuth. 



I wish to congratulate the authors upon the ingenuity of the apparatus 

 employed, together with its general arrangement on the ship ; also upon the mass 

 of data accumulated in this paper, which I believe will be a valuable contribution 

 to our proceedings. 



The Chairman : — It is to be regretted that a paper of this character, as well 

 as those which are to follow, should have such scant attention, owing to the lateness 

 of the hour; but I know that all the members who are interested will read them 

 when they appear in the Transactions, and I know that you will permit me to 

 extend the thanks of the Society to the authors of the paper which has just been 

 presented for the very admirable work they have done. 



We will now have read to us the paper entitled, "Logarithmic Speed-Power 

 Diagram," by Mr. Thomas M. Gunn. 



Mr. Gunn presented the paper. 



♦See Transactions of Institute of Naval Architects, London, 1912. 



