METHOD OF CONSTRUCTION OF CONCRETE SHIPS. 13 



and support the shell bars. The most satisfactory method was probably the one 

 used at San Diego, as described above. At Mobile, the shell steel was supported 

 by the "White Bar Clip." The horizontal rods are hung from wires nailed to the 

 forms and held in place by the clip. 



Various means were employed for erectmg the frame steel. Some form of 

 clamp was used in three of the yards. In some cases where the clamps were used 

 the outboard frame bars were individually wired into position, and the inboard 

 frame bars were preassembled in the clamp and placed in position as a unit. At 

 San Francisco the side frame bars were erected and then the bottom frame bars. 

 In one yard a temporary wooden horse was placed at the elevation of the bottom 

 of the vertical side frame bars until they were wired into place with the stirrups. 

 The horse was then removed, and the bottom sections of frame bars were placed in 

 a similar manner. At Wilmington, N. C, the frames were prefabricated in three sec- 

 tions. The first unit consisted of the bottom or floor section up to the 6 foot 4 inch 

 water-line, and the other two sections extended from this line up to the deck line 

 and over to the hatch girders or the center line of the ship. The prefabrication 

 was done in an adjustable wooden frame, which was set to a templet for each frame. 

 No difficulty was experienced in setting these prefabricated frame sections. The 

 bottom sections of the frames were picked up by their ends, which tended to shorten 

 them slightly, due to the sag, thus providing plenty of clearance to enter the forms. 

 As soon as the frame was set in the floor on position and released, it sprang back 

 into position, tight up against the shell steel. It was anticipated that there would 

 be difficulty in setting the upper sections of the frames because of the lapping of the 

 end bars of the two sections. Little difficulty, however, was experienced on this 

 account. 



Many special tools were designed to assist in erecting the steel. 



The deck steel was placed in a manner similar to placing steel in floors in 

 ordinary building construction. At Wilmington the large longitudinal bars in the 

 fillet of the deck were electrically butt welded by means of a type lO-A 220V, 60 

 cycle, AC machine manufactured by the Federal Machine and Welder Company, 

 of Warren, Ohio. This machine is equipped for the continuous welding of bars 

 from y-i inch to i % inches in size, either round or square. The bars come in lengths 

 of 60 feet, and the butt-welding machine was set on the deck about 60 feet from the 

 aft end of the hull. The bars were passed through the machine and over a series 

 of iron rollers extending along the fillet. No difficulty was encountered in handling 

 the bars or in placing them. Eight men could handle a 240-foot iJ/^-inch bar and 

 place it in position in the fillet. Good welds were obtained in from 30 to 60 sec- 

 onds. The hard steel was a little more difficult to weld than structural grade, which 

 was not obtainable at the time this work was done. 



CLEANING OF FORMS FOR CONCRETING. 



The cleaning of the forms preparatory to placing concrete is one of the very 

 important matters in concrete ship construction. On account of the relatively large 



