2 METHOD OF CONSTRUCTION OF CONCRETE SHIPS. 



ating the yard at Jacksonville, Fla., and are constructing the concrete hulls for two 

 7,500-ton deadweight oil tankers (Type 70). The tankers are being outfitted by 

 the Jacksonville Ship Outfitting Company at Jacksonville, Fla. The Liberty Ship- 

 building Company are operating the yard at Wilmington, N. C, and are construct- 

 ing two 3,500-ton deadweight concrete hulls (Type 2) (Fig. 3, Plate 6). The out- 

 fitting is being done by the Jacksonville Ship Outfitting Company. 



The reinforced concrete ship is an ultra refined concrete structure with walls, 

 floors and columns similar to a building, requiring the engineer to deal with forms, 

 reinforcement and concrete, but with such refinement in quality and workmanship 

 that new methods of construction had to be developed or old ones improved in order 

 to meet the exacting conditions. Forms on a large scale had to be built of great 

 rigidity to conform to irregular curves and shapes and exacting dimensions, and 

 supported by novel means. Reinforcing steel, of both large and small diameter and 

 long and short lengths, had to be bent with exactness to irregular curves and firmly 

 secured in position with very small tolerances on account of limited spaces made 

 necessary by the requirement for minimum weight of hull and small allowable cov- 

 ering of concrete. Concrete of excellent quality, but of the lightest possible weight, 

 had to be placed in thin walls containing very high percentages of reinforcing steel, 

 the bars being in many cases only a few diameters apart. 



Unlike a building the concrete ship must be constructed on a temporary foun- 

 dation or underpinning. 



The Emergency Fleet Corporation adopted the policy of suggesting feasible 

 methods to the contractors, but permitting each to develop and use its own methods 

 provided the cost was not excessive. Thus the methods employed for the various 

 operations differed in the several yards. 



Complete cost records have been made of each operation, and comparisons can 

 be made of the relative efficiency of the several methods. 



Before discussing in detail the methods employed by the contractors for the 

 various operations it would perhaps first be well to outline briefly the stages through 

 which the construction work progresses, giving a general bird's-eye view of the 

 entire operation. The order of procedure is not fixed, for many of the operations 

 overlapped and it was not possible at times to proceed with the work as desired be- 

 cause of lack of certain required materials, but the outline here given was essen- 

 tially followed. 



1. The underpinning or blocking for supporting the floor forms is set in posi- 

 tion on the ways. 



2. The scaffolding with overhead trusses for holding the outside forms is set 

 in position. 



3. The outside bottom and side forms are erected complete, thus providing 

 means for supporting the reinforcing steel. 



4. All steel inserts such as sea chests, stern frame, stem plate, hawse pipes, etc., 

 are secured in place on the inside of the outside forms. 



5. The bottom and side shell reinforcing steel is placed within the outside 

 forms. 



