142 BUOYANCY AND STABILITY OF TROOP TRANSPORTS. 



mum spacing of the bulkheads ^o = 45 'feet, which gives a maximum value of the 

 probability factor: — 



c. ^^— = 3-5- 



45-35 



{d) In order to secure the two-compartment standard, the combined length of 

 any two adjacent compartments must in no case exceed the floodable length, f, and 

 should in general be slightly smaller. Hence — 



'^<^ (a) 



and the smallest permissible floodable length will be — ■ 



/o = 2J„, or 

 > 



/o = 90 feet (3) 



When the floodable length at any point is so great as to admit of a subdivision 

 into three compartments, each of which has a length greater than ,^0, the three-com- 

 partment standard, should be adopted in that region if practicable. In such a case 



no single explosion is likely to flood a greater length than — f, and a margin of 



o 

 safety will remain, which enables the ship to sustain further damage without sink- 

 ing. A similar procedure may be followed where practicable in cases where / > 4.^0, 

 resulting in a still greater margin of safety. 



(e) If we take into account not only the direct effects of flooding but the prob- 

 ability of a bulkhead being lost, there is a limit to the closeness of spacing of bulk- 

 heads, which it is not profitable to pass. In other words — contrary to what might 

 appear at first sight — it is not always advantageous from the point of view of safety 

 to space the bulkheads closer together. 



Consider first a one-compartment ship, where the loss of a bulkhead means the 

 loss of the ship. If the spacing is here made equal to e, there is a practical certainty 

 that the ship will go down if she is hit by a torpedo. If the spacing is 45 feet, that 

 is s = So, we have seen that the probability of a bulkhead being lost is as 3.5 to i. 

 If the floodable length is 90 feet, the limiting value for the one-compartment stand- 

 ard, then by increasing s beyond the 45 feet, the probability of a bulkhead and hence 

 of the ship being lost is reduced and reaches its minimum when .y = 90 feet : — 



c = — ^ — = 0.64. 

 90-35 



In general, the greater the spacing, the smaller the probability of loss, and the 



maximum safety within the one-compartment standard is evidently attained by 



making the spacing equal to or slightly smaller than the floodable length. 



