48 APPLICATION OF BUOYANCY BOXES TO THE STEAMSHIP 



Longitudinal Stability. 



Consider the forward compartments opened by the torpedo explosion. Water 

 will flow into the compartments until the inner and outer water lines coincide. The 

 water in these compartments increases the draught of the ship and also gives it a 

 considerable list. 



At Equilibrium. — The average height of water in the forward compartments 

 of the ship in ballast is X feet above the double bottom. 



If this amount had been applied at the center of the ship, -the draught of the ship 

 would have been : — 



37 X ^70 ^ +13.25 feet, or 

 50 X 400 



17 X X +9-25 feet above the double bottom. 



50 X 400 



If the water load is shifted 108 feet forward, a moment will arise, viz.: — 



^x 37 + 170 X 108 foot-tons. 



35 



This moment is anti clock-wise. 



This moment is counteracted by the water plane moment of the ship. The water 

 plane approximates a rectangle 50 feet X 400 feet, hence one foot submergence at 

 one end creates a moment — 



4ooS^i2 X ^ foot-tons. 

 6 35 



Section Modulus ) \ Weight in tons of 



of plane around \ ] one cubic foot of water 



The forward end is submerged a distance — 



(X=Z?) x^feet. 



lOo 



Hence the created moment is: — 



4QQ X 50 >, _L ( X- Z?) ^ foot-tons. I 



6 35 ^ 108 i 



This moment is clock-wise. ■ 



An anti clock-wise moment of ' ;i 



n^>^ll X i X (X-Z?) X -^ fbot-tons ) 



6 35 108 j 



is created by the free water surface inside the ship. j 



The sum of these three moments will equal zero at equilibrium. ! 



The torpedoing of the boiler and engine-room place will only effect an increased j 



draught as the center line of these compartments coincides with the center line of j 



the ship. i 



