BUOYANCY AND STABILITY OF TROOP TRANSPORTS. 



By Professor William Hovgaard, Member. 



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



in New York, November 13 and 14, 1919.] 



We shall here deal in particular with ocean-going transports such as those 

 used to carry troops across the Atlantic during the world war. The number of 

 troops on board a transport often greatly exceeds the number of passengers car- 

 ried on a liner of the same size, and this fact, in connection with the urgency and 

 vital character of military expeditions in general, makes the problem of the safety 

 of troop transports rank higher in importance than in the case of ordinary passen- 

 ger steamers. 



REQUIREMENTS FOR SAFETY. 



In order to obtain a basis for the discussion it is necessary to make certain as- 

 sumptions as to the amount of damage which it may reasonably be stipulated that 

 troop transports should be able to stand without their safety being imperilled. In 

 addition to the ordinary dangers of navigation, notably collision and grounding, such 

 vessels are in time of war exposed to attack from artillery, mines, and torpedoes, 

 but we consider here those dangers only in so far as they affect the buoyancy and 

 stability, involving damage below the bulkhead deck. In this connection underwater 

 explosions are the most important. 



Evidently the minimum claim to buoyancy and stability of a troop transport is 

 that such a vessel should stand the eft"ect of one underwater explosion or one colli- 

 sion without sinking or capsizing. But this is not sufficient. In order to provide for 

 roughness of the sea and allow the safe lowering of the boats, there must remain a 

 certain margin of reserve buoyancy and the ship must not take too great a list. Since 

 an explosion or a collision is liable to damage one of the main transverse bulkheads, 

 those requirements must be satisfied even if two adjoining compartments are 

 flooded, whatever the conditions of loading. Finally, the spacing of the bulkheads 

 should be such that there will be very little chance of two bulkheads being damaged 

 by one explosion. 



As explained hereafter, the claims stipulated above practically determine a 

 minimum length of troop transports. It is at once clear, moreover, that in order to 

 prevent a ship from taking an excessive list in the damaged condition, she must be 

 subdivided essentially on the transverse system and the metacentric height must 

 not fall below a certain minimum dependent on the size and design of the ship and 

 the condition of loading. 



