50 STEEL SHIP CONSTRUCTION 



The labor cost was calculated on the basis of man efficiency, using $5.40 as 

 the average daily wage of all men engaged on ship construction. To arrive at the 

 number of men per way the following formula was used : — 



Men per way —, 



X c 



in which 



a = fabricating capacity per 8-hour day. 



h = tons steel erected per man per year. 



c = number of ways. 

 300 = number of working days per year. 

 Launching was assumed when 90 per cent of the steel was erected and rivetted. A 

 balance between fabricating, erecting and rivetting was taken for granted. 



Plate 21 shows deadweight-ton cost curves for a five-way yard, plotted for dif- 

 ferent building programs and man efficiencies with fabricating capacity to meet 

 program requirements. The Minimum Cost Line shows the most economical build- 

 ing program for certain given conditions. 



Plate 22 is a companion curve to those in Plate 21, being plotted from the same 

 data, and shows the fabricating capacity corresponding to the most economical build- 

 ing program. 



Plate 23 shows deadweight-ton cost curves plotted for different numbers of 

 ways and man efficiencies with a fixed fabricating capacity of 150 tons per 8-hour 

 day. The Standard Ways Line shows the most economical number of ways for dif- 

 ferent man efficiencies. 



Plate 24 shows cost curves based on the same data as those in Plate 23, but re- 

 ferred to deadweight-ton cost and man efficiency as coordinates. 



A careful study of Plates 21 and 23 develops some very interesting results which 

 may be expressed as laws and enumerated as follows : — 



1. For a given man efficiency there are a certain definite number of ways and 

 a certain building program that will result in minimum costs. 



2. As man efficiency increases costs decrease according to a diminishing ratio 

 and not in direct proportion to increase of efficiency. 



3. The lower the man efficiency the greater the number of ways and the longer 

 the building program to secure most economical construction. 



The intimate connection between man efficiency and building program shows, 

 beyond any question, the advisability of working to standards and setting such 

 standards within reach of the working force. For example, if a contract were se- 

 cured for delivery of a 7,500 deadweight-ton cargo vessel in 155 days from keel lay- 

 ing (125 days keel to launching and 30 days launching to delivery), there is a pos- 

 sible variation in cost of about $117 and $158 per deadweight ton, depending on 

 whether the yard can show a man efficiency of 65 deadweight tons or 25 deadweight 

 tons per man per year with a fabricating capacity of 90 tons per 8-hour day. Ob- 



