LAUNCHING OF SHIPS IN RESTRICTED WATERS. 



By Captain H. M. Gleason, Construction Corps, U. S. N., Member, and 

 Lieutenant Commander H. E. Saunders, Construction Corps, U. S. N., Member. 



[Read at the twenty-seventh general meeting of the Society of Naval Architects and Marine Engineers, held 



in New York, November 13 and 14, 1919.] 



Although there have been ten papers read before this Society giving notes 

 and data on the launching of various types of ships, the subject of the launching 

 of ships in restricted waters has not been touched tipon. The authors therefore 

 have undertaken to present this subject based upon the experience of the Mare 

 Island Navy Yard. 



Unfortunately, there is very little definite information obtainable from text- 

 books, technical papers, etc., giving the results of actual launchings in which means 

 to check the speed of ships have been used. It is therefore believed that the sub- 

 ject-matter of this paper will be a welcome addition to the already published data on 

 launchings. 



The launching of a large ship is attended with a certain amount of risk under 

 the most favorable conditions, and when there is added to this the problem of check- 

 ing the ship after leaving the ways, the anxiety of those responsible is not relieved 

 until the ship comes to rest. In most shipyards in this country there is sufficient 

 water space in wake of the building slips to allow the ship free scope, or at least 

 sufficient water space to check the ship by the dropping of anchors. In some ship- 

 yards situated on narrow waters the building slips are inclined at an angle of about 

 45 degrees to give greater travel. 



Various methods have been successfully used to check vessels on leaving the 

 ways, such as — 



(a) The breaking of rope stops. 



(&) The use of wood friction wedges. 



(c) Fitting of a mask on the stern. 



(d) Dropping of anchors. 



(e) Slewing the stern with the channel by dropping stern anchors. 

 (/) Chain drags. 



Anchors are generally fitted for emergency use in connection with any of the 

 above methods. 



The most commonly used method, especially in English and Scotch shipyards, 

 is the use of heavy chain drags. The amount of chain used varies according to the 

 experience at the various yards, and depends upon the nature of the surface avail- 

 able for the drags, launching speed, etc. ; but the usual weight of chain is about one- 



