14 SALVAGE EQUIPMENT USED IN RAISING SUBMARINE F-4. 
with a heavy “A” frame and a substantial boom. The hoisting machinery on the 
barge consisted of two engines, each having two drums of 34-inch plow steel wire 
rope. By taking the mooring lines to the niggerheads of the engines, the barge 
could be shifted conveniently. Special lead blocks and sheaves were rigged for 
handling the chains and for lowering the pontoons. 
For the bow and stern pontoons 2-inch chain was used. As the lifting capac- 
ity of the middle pontoons was considerably greater, 25-inch chain was used for 
the latter. All six chains were rove under the boat before any of the pontoons were 
placed. Divers had to tunnel under the vessel to place several of the chains, but 
otherwise the work was accomplished without much difficulty by means of the 
special rigging provided on the wrecking barge. 
PLACING THE PONTOONS. 
After all the chains had been laid out on the bottom under the vessel the barge 
was shifted for landing the midship pontoons. These were flooded to about 3 feet 
of freeboard in the harbor before being towed out to the job. One pontoon was 
placed on each side of the barge opposite the “A” frame, as shown in Fig. 8, Plate 
7. The four runners from the engine drums were dropped through the hawse pipes 
to the bottom and a report made by the divers on their location with reference to the 
chains. When the position was reported as satisfactory, the runners were shackled 
to the ends of the chains. In the meantime flooding the pontoons was continued. 
A 50-foot length of pneumatic hose, fitted with a 34-inch valve at the end, was 
connected to each vent. By manipulating these valves the trim of the pontoons was 
kept under control. The flooding valves were left open. As soon as the runners 
had been dropped through the hawse pipes and shackled on below, the clamps were 
placed on top of the castings, as shown in Fig. 9, Plate 8. In order tc facilitate the 
work of the divers in bringing the two halves of the clamps together, loosely fitting 
34-inch guide bolts were passed through holes provided for that purpose in the ends 
of the clamp castings. These bolts were long enough to permit spreading the clamps 
to the full 12-inch diameter of the hawse pipes. The clamps were lashed to the run- 
ning boards of the pontoons to keep them from slipping off. 
Five-inch manila lines were made fast to the end pads of the cylinders. The 
forward line of each pontoon was taken to a timber head and the after line to the 
niggerhead of one of the hoisting engines. These lines were marked every 5 feet 
as a guide for lowering the two ends uniformly. 
When everything was in readiness, the final flooding of one of the pontoons was 
started. As soon as the pontoons showed a tendency to sink, the vents were shut 
off to avoid further increase in negative buoyancy. Any slight excess of water in 
one compartment had the effect of making that end go down first and cockbilling 
the pontoon. The object of the lowering lines was to prevent the cylinders from 
sinking end on, as would invariably have happened without such control. As soon 
as the divers reported that a cylinder was lying squarely on the bottom, parallel 
