94 ECONOMICAL CARGO SHIPS. 



(g) Application to Design. — Figs. i6, 17 and 18, Plate 41, give, respectively, size 

 of ship, power of ship, and capacity of ship for the various speeds and sizes dealt 

 with in this paper. These three diagrams should be of some use for preliminary de- 

 sign work to rapidly approximating the dimensions of a new ship. They are only of 

 definite value, of course, if the proportions and characteristics of the ships are simi- 

 lar to those dealt with in this paper. 



(h) Fuel. — Figures compiled for the 500- foot ship indicate that for the same 

 profits the cost of coal fuel could only be 53 per cent of the cost of oil fuel. This 

 figure, of course, includes putting coal in bunkers, and it takes full consideration of 

 the saving in weight and increase in carrying capacity of the ship due to the use of 

 oil fuel. This economy in oil fuel will not be maintained, of course, if the ships are 

 not running with capacity cargoes. 



(i) Concrete Ships. — The 500-foot ship was calculated also as a concrete ship, 

 and the assumption was made, for the sake of comparison, that depreciation, insur- 

 ance and up-keep would be at the same rate per annum as the steel ship, viz., 13 

 per cent. On this basis, in order that the concrete ship should show the same oper- 

 ating profits with the steel ship (the cost of machinery being the same), the cost of 

 hull and outfit for the concrete ship at 10 knots should not exceed 79 per cent of 

 the cost of the hull and outfit of the steel ship, and at 13 knots it should be limited 

 to 70 per cent of the cost of the steel hull and outfit. The cost of a concrete 

 ship per ton of deadweight to show equal profits with the 500-foot steel ship, is 

 shown on Fig. i, Plate 40. 



These figures are on the basis of $6.00 fuel and no dues, but they are ap- 

 proximately true for the other working assumptions. 



DISCUSSION. 



The PfeEsiDENT: — Gentlemen, Mr. Robertson's paper, "Economical Cargo Ships," is 

 before you for discussion. 



Professor H. C. Sadler, Member of Council: — Mr. President and gentlemen, I think 

 Mr. Robertson is to be congratulated in giving us a paper of this type. It is unfortunate, in 

 some of our papers, that the writers occasionally omit certain data on which they have based 

 their conclusions. Mr. Robertson has been very careful to give us all the information on 

 which the results of his calculations are based, so that it is a comparatively easy matter, 

 with different assumptions, to reproduce a curve for any given set of conditions as to freight 

 rates, first costs, running expenses, etc. 



I may say that the paper perhaps justifies, to a certain extent, the work of the Emer- 

 gency Fleet Corporation. As you know, a large proportion of the vessels built were of the 

 cargo type, vessels from 8,800 tons up were in the majority, and they had a speed of about 

 10 knots, showing that they were really of the good, economical cargo type. 



