22 LAUNCHING OF SHIPS IN RESTRICTED WATERS. 
No attempt will be made to include in this paper any details of the launch 
other than those having to do with the braking operations. The complete launch- 
ing report, Mare Island Plan No. 24389, has been issued and is now available for 
the information of those who may desire it. The following paragraphs are copied 
verbatim from this report :— 
OPERATION OF HYDRAULIC LAUNCHING BRAKES. 
“Before proceeding to a description of the behavior of these brakes, it will be 
of interest to note briefly the organization of the special brake detail and the 
instructions issued for the guidance of the members of this detail. It has already 
been stated that there were three full rehearsals of these operations prior to the 
launch and that all the men were given an opportunity to watch the performance 
of the launching model, when specially rigged with cables and chains. 
“The two groups of men operating the hand pumps were directly in charge of 
a supervisor on each side, who was to superintend the operation and the emergency 
release of the brakes on that side. It was conceivable that, in the event of a wire 
cable stranding or kinking, or part of the brake gear carrying away, it might be 
necessary to release the pressure in one or more sets of cylinders to avoid serious 
damage. 
“The brakes were to be set as soon as their respective cables began to pull 
through (for the brakes Nos. 3, 4 and 5, port and starboard, this would occur at 
about 568 feet travel). As an additional signal, two large klaxons were to be 
sounded by the brake control officer at the head of the slip, when the ship had 
run the proper distance and the chain cables had straightened out. From the rate 
of pressure curve, previously determined at the launching of the Zane, it appeared 
that about eleven seconds would be required to apply the normal pressure of 
850 pounds per square inch, and that in this time at least 200 feet of wire would be 
drawn through the brakes. The initial pressure was set at 50 pounds in order to 
insure that there was water in each system and that the hydraulic rams would 
respond at the first stroke of the pump. The water service was turned on each 
set of brakes at the moment that the vessel was released. 
“In case the speed of the vessel had not been sufficiently checked at 1,000 
feet travel (under normal conditions the vessel should have stopped dead in the 
water at about 960 feet travel), emergency pressure, I,150 pounds per square 
inch, was to be applied, the signal for this pressure to have been five or six short 
blasts of the klaxons. When the vessel had stopped dead in the water, the brakes 
were to be quickly released upon signal of the klaxons, to prevent the strain on the 
cables from drawing the vessel back toward the slip. Competent observers were 
stationed near each set of brakes, to note any unusual behavior of the apparatus 
and to watch the performance of the brake crews. Arrangements were made to 
take motion-picture observations of two extra gauges on the port and starboard 
No. 5 brakes. The actual pressure, distance and time readings are shown on 
Plate 10. 
“The chain cables attaching the friction wires to the ship were flaked down 
