STABILITY OF VESSELS AS AFFECTED BY DAMAGE DUE TO 



COLLISION. 



By William Gatewood, Ksq., Member. 



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



New York, December 10 and 11, 1914.] 



Stability is a subject which should receive consideration before the dimensions 

 of a vessel are settled. The height above base line of the initial metacenter can be 

 determined, w^ith a fair degree of accuracy, by the use of coefficients. A conven- 

 ient formula is — 



Metacenter above base = a/J'+ c — 



H 



In this formula H represents the draught and B the beam of the vessel ; aH is the 

 height of the center of buoyancy above base and c — is the height of the meta- 



center above the center of buoyancy. For coastwise passenger and freight steamers 

 of modern design having fine load waterline forward and full midship section, the 

 coefficient a will vary between .57 and .54, depending on coefficient of fineness and 

 exact shape of lines, and decreasing for the same vessel about .01 as the draught 

 increases from 12 feet to 24 feet. For the same type of vessel, the coefficient c will 

 vary between .078 and .082, depending on the exact shape of the load waterline 

 and the fineness of the vessel. For the older vessels, with considerable deadrise and 

 with V-shaped lines forward, both coefficients will be found to be greater. If they 

 had not taught that increase in beam does not, ipso facto, imply increased resist- 

 ance to motion, the model tanks could be blamed for a reduction in metacentric 

 height on passenger steamers, because they are responsible for small deadrise and 

 for fine load waterlines forward on vessels which are designed to obtain a good 

 speed on small horse-power. 



The determination of the height of the center of gravity above base cannot 

 be approximated so readily. The vessel, as completed and loaded, can be considered 

 as composed of six items : — 



1. The hull and fittings below the highest continuous deck. 



2. The hull and fittings above the highest continuous deck. 



3. The machinery. 



4. The fuel and water. 



5. The passengers, crew and stores. 



6. The cargo. 



