LAUNCHING OF SHIPS IN RESTRICTED WATERS. 213 



The President: — Is there any further oral discussion? If not, the secretary will read 

 a commun,icated discussion. 



Rear Admiral D. W. Taylor, C. C, U. S. N., Honorary Vice-President : — This is 

 a paper of a kind very desirable to have in our Transactions. The launch of a large ship 

 is perhaps the most diiificult engineering problem connected with shipbuilding, and when 

 it must be undertaken in restricted waters, the sense of responsibility of the naval constructor 

 and of relief after a successful laimching are necessarily much accentuated. 



The friction brake metliods used in Mare Island launches are certainly sound theoret- 

 ically, and the fact that they have been used with success on a number of ships shows that 

 the practical application, has been carefully worked out. Their extension to the launch of 

 the California is a bold step, but the paper itself shows that it has been taken only after 

 the most thorough and painstaking investigation, justifying the anticipation of the authors 

 of a successful outcome. 



Captain Gleason (Communicated) : — Professor Hovgaard's discussion is very inter- 

 esting and is appreciated by the authors of this paper. There is one point which it is 

 desired to invite attention to wherein Professor Hovgaard mentions the comparison between 

 the launching of the Kanawha and Cuyama. The Kanawha had a mask fitted on her stern, 

 while the Cuyama did not. The same type of launching brake was used, and for practical 

 pui-poses the difference between the distance traveled by the Kanawha and Cuyama may be 

 taken as a fair approximation of the effect of the mask. No definite comparison, how- 

 ever, can be made, for the reason that there were no means in the brakes, as then employed, 

 to register the actual pressure applied to the friction ropes. It is therefore quite possible 

 that the pressure on the friction ropes in the case of the Kanawha may have been greater 

 than in the case of the Cuyama. This would of course account for some of the difference, 

 were it the case. It is regretted, in the case of these two ships, one with a mask and one 

 without, that the hydraulic means of applying pressure to the friction ropes was not used. 

 Had such means been used, there would have been some definite data upon which to arrive 

 at a fairly accurate estimate of the effect of the mask. 



Since the paper was read before the Society on November 13 and 14, the California 

 was successfully launched on November 30, using the brakes as described in the paper. The 

 launching brakes functioned satisfactorily, as far as the brakes themselves were concerned, 

 but unfortunately the chains which were used to connect up the friction hawsers to the 

 ship broke at various stages of the vessel's travel, owing to what afterwards was found 

 out to be defective links in the chain. The brakes therefore were not able to produce the 

 effect which had been intended, but sufficient work was done by the brakes before the vari- 

 ous chains parted to reduce the speed of the vessel to such a point that two emergency an- 

 chors stopped the ship without any damage to her. It is regretted that the breaking of the 

 chain cables prevented the obtaining of valuable data in actual experience for comparison 

 with the model experiment data. From the data, however, that were obtained and the dis- 

 tance that each of the friction hawsers traveled through the brakes before the chain broke, 

 it is hoped that a reasonably accurate estimate of the work done by the brakes may be ar- 

 rived at. This data will be collected, and it is hoped that at the next meeting of the So- 

 ciety a complete report of the actual performance may be made to the Society. 



It may be noted that, in launching the California, chains were used for correcting the 



