238 



NOTES ON FUEL ECONOMY. 



When we deal with cargo carrying vessels, in which we must have a certain 

 amount of midship area, we all make the boat as dead-flat as possible. We do not 

 do this to save 3 per cent in horse-power, because every engineer knows that you 

 can more than eliminate that amount, or augment it, by a slack indicator spring. 

 Then why do we increase mid area? Mainly to get the boat as short as possible 

 to carry the deadweight, because every one connected with ship design knows that 

 length is the important factor in the ship, and the expensive one. Beam does not 

 cost one-tenth of what length does. 



As to the ships Mr. Rigg refers to, the examples he gives, I happen to know 

 of as their designer. One of them he calls the Mars class. It is not the Mars 

 class, it is the Everett class, the pioneer of the present colliers in this country and 

 of which the Mars class is a copy. I fixed these proportions and can say something 

 about them. In fixing these proportions I aimed to shorten the ship. If I were 

 designing these ships to-day, I would shorten them still further. If it is of interest 

 enough to put in this discussion — I have not the data with me — I will prepare a 

 table showing the elements of the boats in a competitive design for a cargo vessel 

 probably the most interesting that has been brought out in this country (see 

 table following). 



Dimensions Proposed by Different Builders for a Given Dead- 

 weight, Speed and Draught. 



6. 



Length overall 



Length between perpendiculars.. 



Breadth mid 



Depth mid ,. 



Load draught, maximum 



Speed at sea (knots) 



Dead-weight 



Load displacement 



Coefficient of displacement 



368' 



355' 



48' 6" 



30' o" 



23' 6" 



10.5 



6,125 



9,140 



.791 



381' 



365' 



48' 6" 



3J' 6" 



23' 6" 



10. 5 



6,125 



8,575 

 .746 



376' 



360' 



48' 6" 



29' o" 



23' 6" 



10.5 



6,125 



9,050 



.772 



379 



362' 



48' 6" 



31' 9" 



23' 6" 



10.5 



6,125 



8,600 



•73 



370' 



355' 



48' 



30' 



23' 6" 



10.5 



6,125 



9,100 



•79 



361' 3" 



345' 



48' 3" 



30' o" 



23' 6" 



10.5* 



6,i25t 



8,800 



.787 



*As built 1 1 knots. 



tAs built 6,200 tons. 



That design was contemporaneous with the Mars class Mr. Rigg refers to. A 

 number of large shipbuilders went into this competition. The owners gave com- 

 plete specifications as to what they desired in the ship, but left out everything in 

 the way of dimensions. They said : ' ' We want a vessel to carry so many hundred 

 tons deadweight on a certain draught, the ship to go a stipulated speed." Every- 

 thing else was blank. The beam was stated as so-and-so, and they gave their 



