6 SALVAGE EQUIPMENT USED IN RAISING SUBMARINE F-4. 
Salvage pontoons of this kind were not available in Honolulu. They would not 
have been altogether suitable in any case, because the difference between high water 
and low water off Honolulu is only about 1% feet, and therefore practically all of 
the lift would have had to be accomplished by the difference in draught of the pon- 
toons when flooded and when dry. As there is always a considerable amount of 
slack to be removed from lifting gear before it takes up the load, the result would 
have been a very limited lift at each step, if this type of pontoon had been used. 
There were, however, on hand locally, two bottom dumping mud scows of 
rugged construction. These scows were 104 feet long by 36 feet beam by 13 feet 
deep. The scows had four mud-pockets, each about 24 feet by 13 feet at the top 
and sloping to 11 feet by 13 feet at the bottom. These scows were selected for the 
weight-carrying units of the salvage plant. Details of the scows are shown in 
Plates 11 and 12. The scows were of ample strength and capacity to carry the load 
when distributed to the main strength members of the structure. Their adaptation 
for the job consisted of providing them with suitable lifting gear. 
Briefly, the salvage method consisted of sweeping four wire hawsers under 
the vessel—two forward and two aft. The ends of these hawsers were brought 
up through the central mud-pocket openings of the scows and were then attached to 
specially constructed windlasses mounted over the pockets. Two windlasses were 
installed on each scow, one for each hawser. By winding up the hawsers on these 
windlasses the vessel was thus lifted in the loops of the four slings. 
DESCRIPTION OF EQUIPMENT SCOW. 
Five 30-inch, 100-pound I-beams were used for the windlass foundations on 
each scow. Three heavy angles were fitted across the tops of the I-beams to re- 
sist racking. The ends of the beams were secured to the mud-pocket coamings by 
drift bolts and were braced by 12-inch by 12-inch timbers. The middle I-beam 
was supported throughout its length by the division bulkhead between the two 
central pockets. The two I-beams at the ends were supported by a timber truss 
for transferring part of the load to the mud-pocket framing of the scows. 
The windlasses were made from sugar-mill shafts which were found in stock in 
Honolulu. These shafts were 13 feet long by 145% inches diameter, after being 
turned down. The shafts themselves formed also the barrels of the windlasses. 
Although a diameter of 15 inches is far too small to fulfil the theoretical require- 
ment for winding up cables of the size used, it nevertheless proved satisfactory. 
Of the four slings two were of plow steel. These stranded to some extent, but in 
no instance did a cable fail entirely, due to the short nip resulting from the small 
radius of the bend over the windlass barrel. This impairment ruined the cables 
for further use over the length affected, but this was a small matter as compared to 
the cost and difficulty of building windlasses conforming in diameter strictly to 
theoretical requirements. 
The turning effort was applied to the windlasses by means of a bull wheel fit- 
