36 STRUCTURE OF VESSELS AS AFFECTED 



the fifth part of the length of the vessel abaft the collision bulkhead open to the 

 sea, considering the void spaces in the hold as 50 per cent. It will be noticed that for 

 each condition of loading, the freeboard at the collision bulkhead must exceed 

 25 per cent of the draught, and the after bulkhead of the flooded compartment must 

 extend above the load line, more than 18 per cent of the draught. 



With the fifth part of the vessel's length forward of the machinery space 

 open to the sea, the height of the forward bulkhead of the compartment must 

 exceed 19 per cent of the draught, and the height of the forward bulkhead of the 

 machinery space must exceed 13 per cent of the draught above the load line. This 

 condition is not shown in the figures. 



With two-fifths part of the length of the vessel abaft the collision bulkhead 

 open to the sea, the freeboard at the collision bulkhead must exceed 65 per cent 

 of the draught, and the forward machinery bulkhead must extend not less than 30 

 per cent of the draught above the load line. 



Initial stability seems satisfactory in all the conditions considered, but it 

 must be remembered that the void spaces in the vessel are assumed to consti- 

 tute 50 per cent of the total, and this assumption will not be correct for vessels when 

 carrying a small amount of cargo, or where the cargo is of great density, such as 

 steel, iron ore, etc. 



On this vessel, therefore, under the assumed conditions, transverse bulkheads 

 spaced as shown, and extending to the deck below the hurricane deck, would af- 

 ford protection in case of collision opening any one compartment to the sea, with 

 draught intact not exceeding about 23 feet. They would also afford protection 

 in case any two compartments were open to the sea, with draught intact not ex- 

 ceeding about 18^ feet. To afford protection at greater draughts, the bulkheads, 

 with spacing shown, must extend to the hurricane deck, and the limit of draught 

 would seem to be about 24 feet in case of damage bilging two compartments. 



If the bulkheads are spaced closer, dividing the forward hold, for instance, 

 into three compartments instead of two, better protection will be afforded in cases 

 of ordinary collision and of grounding; and three compartments could be flooded 

 with the same degree of danger as is attended by the flooding of two, with the 

 wider subdivision. Or, if it is considered that the damage will be likely to affect 

 but two compartments, of length about 50 feet each, a greater load draught could 

 be allowed for bulkheads extending the same distance above the keel. The inter- 

 ference with cargo handling and stowing would be appreciable, but not prohibitive. 



If more than two-fifths of the length of a vessel is required to be flooded with 

 safety, it would seem that the transverse bulkheads would need to be supplemented 

 so as to divide the vessel into cells, and this would be commercial in special cases 

 only, as mentioned above. In the case of the Titanic, about 30 per cent of the length 

 of the vessel abaft the collision bulkhead was damaged, or 36 per cent in all. 



