747 
—_ yd = 
the gear was set, it was necessary to pick up the various components almost 
simultaneously in order to keep strain off the charge, and also to keep the 
total weight on any one line small enough to be handled. This was analagous 
to the procedure in setting out the gear and was one of the main difficulties 
of this operation. When the various gauges and other components had been 
lifted sufficiently for the charge to be placed on deck, the charge was dis- 
armed and an investigation was made as to the cause of the misfire. 
17. "Two-dimensional" (paravane) rig 
(a) Setting the gear. -— The two-dimensional paravane rig was uscd in 
order to obtain more information about the distribution of the shock wave 
around a chargc without the necessity of firing additional charges. The 
various parts of this paravane rig are shown in Fig. h. These were arranged 
on the stern of the RELIANCE, roughly in the order in which they were to go 
out. The charge was hung directly over the stern and the sternmost gauge 
block was hung on the starboard quartér of the vesscl. Just forward of this 
was the starboard gauge block while the port gauge block was hung on the 
port quarter, and just forward of this was the forward gauge block. The 
two paravanes were kept on the starboard and port sides, respectively, just 
aft of the main rigging. As the gear was set, the sea anchor, its weight, 
and supporting ball were payed out until the strain came on the sternmost 
gauge block. This was then lowered, together with the momentum—gauge rig, 
until the strain came on the charge, when its lowering also was begun. The 
stern gauge block and its buoy were cast off as soon as the block reached 
the desired depth. As the strain from the two side spacer cables came on 
the starboard and port gauge blocks, these wore lowered simultaneously with 
the charge until the cables running to the paravane became tight. At this 
point the two paravanes were payed out very slowly and in good balance. It 
was important to bear in mind that the greatest strain on the paravanes had 
to come from their towing lines, If the strain came from the line running 
to the gauge block, the paravane wouid shoot in toward the center of the rig, 
rather than pulling out from the charge. When the paravanes were properly 
set and pulling, the various components were lowered further, including the 
forward gauge block which by this time had begun to take part of the strain 
of the charge. As soon as possible the charge was cast off, and the two 
Side gauge blocks were later cast off simultancously. The forward gauge 
block was payed out and cast off, The paravanes were allowed to drop back 
as the main towing cable waspayed out(Fig. 33), at such a rate that the two 
Side gauge blocks were always somewhat forward of a line through the charge. 
This condition was maintaincd until the charge was at the proper distance 
from the boat for firing, and then the two side gauge blocks were allowed 
to drop back until they were exactly opposite the charge. It was extremely 
important for all these maneuvers to be carefully coordinated during the 
setting of this gear. Duc to the short distances betwcen the various com- 
ponents compared with the depth at which the gear was set, they all had to 
be lowered almost simultancously and exact horizontal symmetry had to be 
maintained. One paravane pulling harder’ than the other would cause the gear 
to become askew. If cither paravane tended to shoot in, the gear became 
hopelessly tangled around the charge, and when working with non-standard 
booster systems or loadings, there would be danger of accidental detonation. 
