18 RESISTANCE OF BILGE KEELS. 



Finally, for the higher speeds there is given in column 12 the ratio of the in- 

 crement in power due to 9-inch keels to the power for the bare hull. If it be as- 

 sumed that the increment for 3-inch keels is one-third as great as for the 9-inch 

 keels (as appears probable from Plate 20) we may conclude that the power required 

 to drive keels of the normal proportions may be six to seven per cent of the power 

 for the bare hull. The same figure can be used directly for brake horse-power or 

 for indicated horse-power, since the reduction factors for a given speed are the same 

 for the bare hull and for the hull with keels. 



Acknowledgments. — The following gentlemen, all of Boston, Mr. Henry A. 

 Morss, Mr. Lewis A. Crossett, Mr. Frederick C. Fletcher and Mr. Herbert M. 

 Sears, very generously provided for the expenses of this year, and Mr. Harrison 

 Loring, Jr., sent a receipted bill for transportation; to all and to each I wish to 

 record here my gratitude. 



DISCUSSION. 

 The Chairman : — The paper is now before you for discussion, gentlemen. 



Mr. William Gate wood. Member: — In connection with this paper I would like to say 

 that it is my recollection from the results of the experiments in the Washington Model Basin 

 on bilge keels for battleships that these results are not borne out, and that the power re- 

 quired is almost entirely that which can be attributed to friction. 



Mr. Elmer A. Sperry, Member: — I think the paper is very interesting and there is 

 one point in connection with Plates 19 and 20 which I would like to bring up. Of course we 

 must realize that the actual speed under which this work is done is rather small, yet the 

 upper part of these curves is quite significant. We see in both Plates 19 and 20 that the 

 curves are tending quite rapidly to disperse, showing more relative resistance at this point 

 than at the lower speeds. Now, were these curves projected up into commercial speeds we 

 can only guess what would happen. We are just commencing to understand a matter in con- 

 nection with resistance in air, of much more rapidly moving bodies than this, relatively ; that 

 is, the augmenting resistance due to eddies in corners. So it seems to me it might be well if 

 Professor Peabody would tell us a little more as to how these bilge keels were attached, 

 whether there was a fillet at the junction between the keel and the hull. 



Naval Constructor D. W. Taylor, Vice-President: — Professor Peabody 's paper of- 

 fers some interesting data in connection with wake factors, and I should like to give a little 



