METHOD OF CONSTRUCTION OF CONCRETE SHIPS. 19 



The transferring of the hull from the ways to the water is accomplished in the 

 following- manner. 



Alternate sections of the blocking and forms which supported the hull during 

 construction are removed, and a temporary cribbing is inserted and brought to 

 bear by driving in wedges. As the forms and original blocking are moved, the con- 

 crete is pointed, patched where necessary, and painted. 



The remaining sections of form blocking are removed, and the patching and 

 pointing of concrete is completed. The launching ways are set in place. The launch- 

 ing packing is then placed, the temporary blocking removed, transferring the load 

 to the ways through the packing, and the ship is launched. 



It is obvious that the details of the first two operations will vary with the 

 method used to support the bottom forms. As was outlined in the section dealing 

 with blocking, scaffolding, etc., the forms at San Francisco were supported on pre- 

 fabricated trusses running transversely across the ship. These trusses were spliced 

 at the center line and tapered from the bil'ges down to the keel. After concreting, 

 the proper lines of trusses were pulled out from under the ship, allowing the forms 

 to be removed. A similar method was used at Jacksonville and Wilmington. 



At San Diego blocking was used instead of the trusses. Two of every three 

 panels (each panel is 8 feet 6 inches) were removed and the load carried on the 

 third. The exposed surface was painted, cribbing installed, and finally the last sec- 

 tion of forms removed. 



At Mobile a combination of blocking and struts was used to carry the bottom 

 forms. Immediately before launching the weight of the ship is carried to the 

 foundations through the temporary blocking and through a series of wedge blocks 

 placed under the keel. The launching packing is in place on the greased ways, but 

 does not, as yet, carry any load. The first operation of launching is to drive in 

 wedges set in the packing, so that the packing will bear against the ship and thus 

 take some of the hull's weight. This may be done in one operation, but the general 

 practice is to set the wedges up in two or more rallies. The temporary wedges and 

 keel blocks are then driven out with battering rams, leaving the entire load on the 

 packing. The blocking is usually made up with a block wedge, held together by a 

 steel strap and pin, and with its sloping faces heavily greased. When the pin is 

 driven out with a sledge the block may usually be knocked apart with the ram. 

 Provision is always made, however, to split it out with steel wedges in case it jams. 

 With the blocking out, the ship is restrained from sliding by a series of so- 

 called "daggers" and "triggers" at the bow and stern. The thrust of the ship is 

 taken into five daggers, each of which bears on a trigger. The thrust is carried 

 across the triggers chiefly to a bolster block bolted to the side of the way and 

 thoroughly braced by either one or more spins. The dagger is set so that the pro- 

 duced line of the face nearer the way clears the bolster by about an inch. The 

 trigger is prevented from kicking out by a heavy line which passes under the ship 

 and is anchored to a deadman on the inboard side of the building way. Each of 

 these slings is carried over a chopping block, at which a man is stationed with a broad 



