NOTES ON FUEI/ ECONOMY. 233 



Item. Quadruple. Triple. 



Length 400 ft. o in. 410 ft. o in. 



Breadth 53 ft. o in. 53 ft. o in. 



Draught 27 ft. o in. 27 ft. o in. 



Ship, tons 4,125 4,160 



Cargo, tons 7,000 7,000 



Oil, crew and water 1,900 2,200 



Displacement 13,025 13,360 



Speed, knots 11 11 



I. H. P 2,750 2,800 



Savings per voyage $2,500 



Extra first cost $10,000 



It will be seen that the extra first cost is recovered in four voyages, and 

 after that a steady gain per voyage is apparent. This is not strictly an 

 example of economy due to ship form, but has been inserted as being perhaps 

 of interest. 



EXAMPLE NO. 5. 



From the point of view of economy due to machinery, it can be shown 

 that single-screw propulsion is cheaper than twin screw, the advantage of 

 twin screw being in greater immunity from breakdown, a point by no means 

 negligible in passenger and perishable cargo ships. This is well known to the 

 members of the Society and is only mentioned to make the examples more 

 complete. This refers to steamers of customary revolutions per minute; 

 for the newly arriving motor ship of high revolutions per minute the case 

 is different and needs further investigation. 



EXAMPLE NO. 6. 



Recently published photographs of our latest battleships in dry dock 

 reveal a pecuhar bulbous form of bow, the load water-line being narrowed 

 and the displacement made up by filling out the lower water-lines. Experi- 

 ments at the model tank in Washington show a material saving due to this 

 form, the bow waves being naturally lessened by the fine upper water-lines. 



The superintendent of one of our coastwise lines of steamers has had 

 the courage to adopt this form of bow for a twelve-knot cargo steamer, in 

 which a 3 per cent saving would mean a ton of coal per diem, a by no means 

 negligible amount when figured in dollars per annum. It is to be hoped 

 this will be realized in service. 



I am indebted to Mr. Higgins of the Old Dominion Steamship Company 

 for permission to produce the data of the vessel mentioned. 



Figure 2, Plate 95, shows curves of cross sectional areas and of water- 

 lines compared; Fig. 3, Plate 95, gives superposed body plans. It will be 



