Boxes of Air to Foil the Torpedo 



William T. Donnelly's ingenious method 

 of making cargo-carrying ships unsinkable 



By Robert G. Skerrett 



THE steamship Lucia is unsinkable. 

 At least, such is the opinion of 

 William T. Donneily, a consulting 

 engineer of New York city and a member 

 of the Ship Protection Committee of the 

 United States Shipping Board. Indeed, 

 this belief is shared by his associates on 

 the Board, and for that reason Mr. Don- 

 nelly's special system has been installed 

 upon the ship in question. 



The Boxes and What They Do 



The invention consists fundamentally 

 of a system of portable buoyant water- 

 tight boxes, which, when packed in their 

 designed places, form a veritable honey- 

 comb of small air chambers. By thus 

 greatly subdividing the space allotted 

 to them, these boxes necessarily restrict 

 the volume that may be opened up by 

 the destructive gases of a torpedo, and, 

 therefore, limit the amount of water 

 that can enter the craft so damaged. 



Maritime law sets a limit to a craft's 

 deep load-line. The underwriters will 

 not issue insurance if that line is sub- 

 merged by reason of excess weight taken 

 aboard. While this is a very necessary 

 safety measure, still it actually invites 

 peril. For instance, coal represents 

 forty-three cubic feet to the ton while 

 the ordinary baled cotton runs about 

 ninety cubic feet to the ton. Clearly, 

 if a steamer of a given capacity has her 

 compartments entirely filled with cotton, 

 when loaded to her prescribed water- 

 line, those holds could not be more than 

 partly filled when carrying a correspond- 

 ing weight of coal. And because there 

 would be that volume of unused space, 

 when carrying coal, there would be just 

 80 much more room for water to rush 

 in in case the hull were ruptured. This 

 water would destroy the ship's reserve 

 of buoyancy — previously represented by 

 free air space — and cause her to sink. 

 The cotton cargo, on the other hand, 

 because it has less density and more bulk 

 than the coal, would keep out the in- 



vading sea and actually buoy the vessel 

 at the surface in spite of very serious 

 injury to her hull. 



Cargo Space Is Not Reduced Much 



Now, Mr. Donnelly stows the smaller 

 of his portable buoyancy chambers in 

 between the ribs of the craft and up 

 under the decks between the beams, 

 holding the buoyancy boxes in place in 

 both cases by means of wooden slats or 

 "battens," as they are technically called. 

 The boxes are placed where freight would 

 not be packed. These safety chambers 

 are what might be termed a permanent 

 feature of his plan. In order to take care 

 of excess space in the cargo holds, if the 

 weight of the freight and its density are 

 such that the compartments are not filled, 

 the inventor resorts to "cargo boxes" 

 which differ from the buoyancy boxes 

 mainly in the matter of size. The buoy- 

 ancy boxes average one foot by two feet 

 by three feet and weigh one hundred and 

 three pounds apiece; while the cargo 

 boxes are two and one-half feet by two 

 and one-half feet by six feet and weigh 

 three hundred and eighty-seven pounds. 

 The buoyancy boxes displace four hundred 

 and sixty-five pounds of water, and the 

 cargo boxes displace eleven hundred and 

 fifty-three pounds of water — showing 

 plainly a large net gain in reserve buoy- 

 ancy. Every box is tested first for air- 

 tightness by submerging it in a tank, and 

 then for water-tightness by placing it in 

 a sealed cylinder and subjected to hydro- 

 static pressure corresponding to the posi- 

 tion in the steamer. 



The complete equipment of boxes for 

 the steamer Lucia costs about one-tenth 

 of the building price of the ship. Mr. 

 Donnelly estimates that a vessel should 

 normally be worth ten times her cost to 

 her owners through the service she can 

 render in the course of an average useful 

 life. Therefore, his safety feature in- 

 volves an outlay of only one per cent, 

 of her probable returns. 



544 



