6 METHOD OF CONSTRUCTION OF CONCRETE SHIPS. 



that position simply by tightening the bolts, which pass through strips attached at 

 their ends to the flexible batten. With these "curved sets," as they were called, it 

 was possible to lift lines from the mold loft floor and transfer them to the steel 

 bending tables or to the form timbers. For further use the lines were transferred 

 to heavy sheets of templet paper. 



Cypress was largely used as outside form lumber in the east and Oregon pine 

 in the west. Since the outside forms are exposed to the weather for several weeks 

 or months before the concrete is poured, it is necessary that some material be used 

 which will not warp badly. Most yards used light ]/s or ^-inch sheathing through- 

 out. One yard used i^-inch sheathing in the bottom and bilge forms. 



It was found to be impossible to secure the outside forms rigidly in position so 

 that they would not spread and would withstand the vibration of the air hammers 

 which were used in placing the concrete unless provided with a through tie to the 

 inside forms. Another method is to tie both inside and outside forms to the rein- 

 forcing steel. 



In one case the outside forms were prefabricated in panels throughout the en- 

 tire ship. In all other cases the outside forms were prefabricated in panels only 

 through the middle body portion of the ship and the curved portions, forward and 

 aft, were built as a unit in place. This latter method has proven the more satis- 

 factory. 



At San Francisco and Wilmington the entire outside form was built as a unit 

 in place, but joints were made in the bottom sheathing for removal in panels 

 through the middle body section. A description of the method employed is given 

 below. Its construction was comparatively simple. Shiplap, %-inch in thickness, 

 was used horizontally, backed by 2 by 6-inch studs at the frames and midway be- 

 tween frames or on 25^ -inch centers. The studs were fitted to the proper shape 

 on the mold loft floor, allowance being made for the thickness of the shiplap. They 

 were erected in the hull so that one face was coincident with the center line of 

 the frame (Fig. 28, Plate 8). 



For purposes of erection, wires were strung along the center line of the hull 

 and also 27 feet on either side of the center line, 27 feet being the half breadth of 

 the ship. The base line was also given at each frame. Points for stringing these 

 wires were given by the surveyor. 



While the ribs were on the mold loft floor, the 36-foot, 26-foot and lO-foot 

 water-lines were scribed on them, and also the intersection of the bottom and sides 

 located as in Fig. 28. The offsets at each water-line from both the center line and 

 the 27-foot line were scribed on a batten at the mold loft, four battens being re- 

 quired. These battens were then used in setting the studs, the offset from the 27- 

 foot side being used and the offset to the center line used as a check. A light batten 

 D was fitted across the faces of the studs as in Fig. 28 to take the curve of the ship 

 so that the distance a could be measured and set off on the stud as distance c. 

 This, done at several places vertically on the studs, gave points on a line so that 

 • they could be adzed to the proper surface DD ready to receive the shiplap. 



