BUOYANCY AND STABILITY OF TROOP TRANSPORTS. 145 



ard and may reach the three-compartment standard amidships, but the latter stand- 

 ard can probably not be attained throughout and to full advantage in ships of less 

 than 800 or 900 feet in length. Higher standards relative to the length of the ship 

 may be attained, but only by carrying the bulkheads up to a rather unusual height 

 or by a reduction in the carrying capacity of the ship, that is, by a disproportionate 

 height of freeboard of the bulkhead deck and a low draught. One-compartment 

 ships may of course be employed for the transport of troops in an emergency, but 

 should ordinarily be used only as supply vessels or other auxiliary duty. 



Dififerences of opinion w^ill no doubt exist as to the numerical values to be 

 adopted for the probable extent of damage by an explosion, the practicable mini- 

 mum spacing of bulkheads, and the assumptions on which the floodable lengths 

 should be calculated, but this does not affect the validity of the principles here 

 stated. The main results of the investigation, as relating to troop transports for 

 ocean service and on the present standpoint of submarine weapons, may be sum- 

 marized as follows: — 



1. Troop transports should have a length of not less than about 500 feet. 



2. The freeboard of the bulkhead deck and the sheer should be such that, when 

 the ship is on her deepest draught and with reasonable assumptions as to permea- 

 bility, she will conform at least to the two-compartment standard throughout her 

 length. 



3. Excepting the extreme ends of the ship, the spacing of transverse main bulk- 

 heads should not in general be less than about 45 feet. 



4. Whichever standard of subdivision is adopted, the spacing of the bulkheads, 

 at any point of the ship, should be the greatest practicable consistent with that 

 standard. 



5. Steps in bulkheads. — When a transverse bulkhead is divided into parts placed 

 on different frames, it is said to be stepped. Such a bulkhead actually consists of 

 two or more vertical parts and one or more horizontal parts, or steps, the latter 

 being formed by the deck or decks at which the continuity of the bulkhead is broken. 

 Damage to the side byexplosion or collision in way of a step located below the water- 

 line is likely to open both of the adjacent compartments to the sea and thus, depend- 

 ent on the length of the step, the value of the subdivision is seriously impaired. Sup- 

 pose, for instance, that, as indicated in Fig. i, a bulkhead has a step 35 feet long 

 and that the horizontal extent of the damage by an underwater explosion is likewise 

 35 feet; then the chance of both adjacent compartments being flooded by one explo- 

 sion is practically doubled due to the presence of the step. 



Steps in bulkheads are therefore to be avoided or their lengths at least reduced 

 to a minimum. 



Recesses or horizontal steps in bulkheads are less objectiouctble, provided they 

 do not extend so near to the sides of the ship as to be damaged by an underwater 

 explosion. 



6. Integrity of Bulkheads and Other Watertight Surfaces. — Several precau- 

 tions must be taken to ensure the effectiveness of watertight subdivisions, having for 



