10 METHOD OF CONSTRUCTION OF CONCRETE SHIPS. 



Test specimens must bend cold, without cracking on the outside of the bent por- 

 tion as follows: Bars below %-inch in diameter must bend through i8o degrees 

 around a pin whose thickness equals the diameter of the bar. Bars ^-inch in 

 diameter or above must bend through i8o degrees around a pin whose thickness is 

 twice the diameter of the bar. 



Typical results of tests of the steel are given in Table 2, Plate 2. This hard 

 steel caused considerable difficulty in the large sizes, for it was very hard to bend 

 to shape. Approximately 1,600 short tons of reinforcing steel were used in each of 

 the 7,500-ton tank and cargo ships and 550 tons in the 3,500-ton cargo ship. The 

 longest length obtainable was 60 feet. 



HANDLING OF REINFORCING STEEL INTO HULL. 



At all yards the shell and bottom and side frame steel was carried by hand 

 labor from the steel yard or railroad car into the hull, through openings left in 

 one side of the outside forms near the quarter points of the length of the ship. The 

 frame and side shell steel was hoisted by hand or block and tackle from the top of 

 outside forms. At one yard a temporary extension was made of the railroad track 

 to the opening in the forms, and the steel was dragged by hand labor from the car 

 platform directly into the forms. 



After the bottom concrete was poured it was necessary to close the openings 

 in the lower part of the outside forms, and the steel had to be hoisted over the top. 

 At Oakland a power lumber hoist operating on the side of the staging was used to 

 hoist the steel to a runway on the top deck, from which it was carried by hand on 

 to the ship. At San Diego it was hoisted in bundles by tower revolving cranes and 

 dropped into the ship. Mobile used a gantry crane, Jacksonville used derricks, and 

 Wilmington used tower whirlers in the same manner. 



FABRICATION OF REINFORCING STEEL. 



At San Diego all reinforcing steel was sheared to exact lengths, and all bars, 

 including unbent bars, were tagged according to detailed plans and sent to the 

 forms ready to set into position, all joints and laps being fixed on the plans. In 

 all other yards the unbent longitudinal and shell steel was sent to the forms without 

 shearing or tagging, the staggering of joints and laps being provided for by instruc- 

 tions to the steel foreman. It is questionable whether the second method is equally 

 as good as the first. 



The bending of stirrups was originally done by hand methods in all yards. The 

 bender consisted of an arm pivoted at one end and carrying a hardened roller which 

 bent the stirrups around a fixed pin as commonly used in building work. At Jack- 

 sonville a unique power bender was devised and proved very satisfactory. It works 

 in the same manner as the hand bender, except that an air cylinder constructed of 

 standard pipe and fittings with leather cup piston is provided to operate the bending 



