LAUNCHING OF SHIPS IN RESTRICTED WATERS. 
By LizuTENANT CoMMANDER H. E. SaunprrRs, Construction Corps, U.S. N., MEMBER. 
[Read at the twenty-eighth general meeting of the Society of Naval Architects and Marine Engineers, held in New 
York, November 11 and 12, 1920.] 
At the last meeting of this Society there was presented by the writer a paper 
dealing with methods employed to check the speed of vessels during launching, 
with particular reference to a type of friction launching brake developed and used 
at the Mare Island Navy Yard. A brief description of the launching and checking 
arrangements for the battleship California were given, together with a description 
of certain model experiments conducted in connection with this work. At the 
time this paper was submitted, however, the launch of the California had not yet 
taken place and it was proposed to submit a second paper, in the present form, 
embodying a description of the launch and an analysis of the data obtained at 
that time. 
Before proceeding to a detailed account of the launch, which took place on 
November 20, 1919, it may be well to note the principal characteristics of this 
vessel, as bearing upon the data set forth in the following paragraphs :— 
Werestlts  OVCt rll Mme Aha tes ile nse GU) came MR Sal y 624 feet. 
KCAL MOVER allt teinnum teh ice cytes nye ATR abe aN aU: 97 feet 534 inches. 
Meanedraughtwat launching. sls rane ns ane 14 feet 914 inches. 
Launching weight complete, with cradle......... 14,610.5 tons. 
Pressure on ways, per square foot............... 2.4 tons. 
Mean declivity of ways.............. RD Ey Feat 11/16 inch per foot. 
Maximum velocity attained: yc oie oa ae 24.7 feet per second. 
Velocity when brakes were applied.............. _ 21.5 feet per second. 
In order to obtain data for a complete analysis of the launching, every effort 
was made to provide sufficient recording apparatus for all phases of the operation. 
In addition to the standard drum chronograph previously employed at this yard, 
a second ‘‘direct-reading’’ chronograph was fitted and both machines connected 
to the ship by wires which were laid out over the ground ways. The arrangement 
of the latter chronograph, whereby the special ‘‘clock,’’ the chronograph dials, the 
two pressure gauges of the No. 5 brakes and the tachometer (indicating feet per 
second velocity) were all included in the field of view of the motion-picture camera, 
is very similar to that shown on Plates 10 and 11 of last year’s paper. Plate 2isa 
view of the entire brake control station at the head of the ground ways, port side. 
Plates, 3, 4, 5, 6 and 7 have been included in this paper to supplement the plan, 
Plate 14, of last year’s paper. These illustrations show, in considerable detail, the 
arrangement of hand pumps, brakes, chains and friction cables as actually installed. 
