The national Republican. [volume] (Washington City [D.C.]) 1866-1870, 1869-09-02

| Translated for the National Republican,
Iron floating dock, (balance dock,) bull
In France. near Toulon, for the Viceroy o.
Egypt, and delivered by the contractor, al
Alexandria, the arst Of August, 1868.
This dock, built for the Egyptian fleet, wa.
made sufficiently large TO receive the yaen n.
Of the viceroy, measuring in length 40 a iSc'
boxes, as well as to take In the largest yes-
sells that can enter the harbor OF Alehanufia'
drawing less than 90 feet of water. 4,
In order to fulfill these condltlonsl tnc
principal dimensions were as iollowsi lotai
length, 400 feet; breadth inside, IsN ieeti
breadth Of the floats, feet ~ inchesi. total
breadth, 9s feet ,nchi dePth Or thickness
ION of platform to top of noat, 81 feet 10
inches, total height, 80 feet.
! The ends arc closed by floating gates,
similar to those used In stone docks, only TO
be used when the weight Of the vessel to be
raised Is 1900 tons, but with less weight,
| the floating gates arc not necessary that the
keel may be entirely clear of the water; in
this latter case, the hull Of the vessel In the
dock Is better ventilated and there Is greater
facility for doing the work, the upper side Of
| the bottom float being then not more than
the height Of an ordinary boat above the
| surface OF the water.
The construction Of this dock presented
| several difficulties, The Egyptian govern
ment required that 1t should last very
long time, and 1t was necessary that the iron
framing should be sufficiently strong to with
stand the deterioration Of the plating and the
strains which long service would throw
upon 1t. In order to satisfy these conditions,
the scantling Of materials was as follows /:
The plating Of the bottom Of tho dock is
formed oftwot hicknesses Of plates, In thick
ness TIC inch the vertical sides are of
plate iron, In thickness 1910 inch below,
| gradually diminishing to GIG inch In thick
ness at the upper part the plating Of the
| upper side Of the bottom platform Is In thick
ness 9.16 inch the frames are laid 2iI
inches asunder, and at every l6 feet there are
solid plates with vertical stiffeners secured to
the plating Of the side by angle irons; iu every
third frame for the solid plate is substituted a
trellis work OF fat iron and 7 iron; the inter-
| mediate frames are formed Of I iron connect
| ed by ties and struts, the inner bulkhcads are
ofplate iron In thickness $40 inch, strength
ened by T irons, and secured to the side plat
ing by angle irons. The weight Of the iron
work, exclusive Of the gates, including the
| plating, angle and other iron, was $500, 900
pounds; the number Of nuts used being ,060,.
600; the total weight Of the dock light was L..
$40 tons. Tho bottom platform is divided into
watertight compartments, each Of which
Is divided into two by longitudinal water.
tight bulkhead; this bottom Is constructed
so as to resist apressure Of POS pounds per
square foot upon the outside, and a pressur,
Of 15II pounds per square foot on the inside
when the upper surface Of the bottom is i'm
mersed % feet. The sides Of the dock ar,
In like manner divided into 2 water.tigh
compartments. Tho dock Is pumped out b,
four centrifugal pumps, worked by two steam
engines, placed on the sides; the pipes ar,
arranged so as to pump from one or sevsra
compartments OF the bottom or sides, as wei
as from the inside OF the dock when the
floating gates are In place. 1t requires
about four hours to pump the dock, when
the bottom platform only Is used, without
the gates, and about Ave hours to pump II
out when the gates are In place.
This floating dock was commenced on the
18th of October, 1896, and was launched
entirely completed, on the Goth Of January
, 1867. The launching Of this vessel, which
can only be compared with that Of the Grea
Eastern, was subject of much considera
4 ton before the building was commenced.
: was not to be thought Of to launch this heav
q rectangle mass In the direction Of the length
as there would be danger of straining II, an
= the result would be doubtful. The launcl
ing athwartships was thus preferred becaus
= II offered greater facilities In the construt
a ton, and, though not exempt from danger
offered fewer difficulties.
This being determined, It became necc.
sary to prepare o slip Of about 400 feet Q
water front; also, the taking into considera
ton the weight which the newly-mad
ground and son bank could support, ant
also the inclination and surface OF friction
the most favorable for sure launch, not L
be too rapid, and Of equal velocity at boil
: ends.
, To this end the following arrangement
were made; There was built on this lengt
i've sets Of launching ways, having an incl
, nation Of five eighths Of an inch to a fool
!, each set forming an independent cradle, tn
breadth of each piece being . feet, with th
:, go feet, the parts being connected by Tic
" and struts.
This arrangement of the launching way
r was Indispensable, as 1t was necessary I
/. cover sufficient ground that there might NJ
be any settling under the weight OF the stru'
ture. The rubbing surfaces Of the launchin
: ways aud the bilge ways and lauuchin
heat Of the weather the tallow used to greai
n the parts in contact was mixed in equ
parts with CASTLE soap. The surface
friction was 1887 feet, with weight OF A..
tons.
s. 1t is well understood that body placed @
A IN inclined plane tends to descend by a
effect resulting from the weight, and tn
| mOTt Us tut angie lb RTthttTi Dut
$ Is not easy TO determine IN practice the nd
= herence Of the body to the plane which sup
ports 1t. The greater or less exactness II
laying the inclined plane, its partial settle
ment of the foundation caused by the weigh
: and the manner Of greasing the rubbing sur
faces have great influence on the motion 0
. the vessel, so that there is always some un
i certainty even to those having the most ex
4 perience.
Ia tho pra.ept ~, an IN, ,uastiop was IN
, more serious, as, with difference In th
, velocity OF the two ends Of the dock, on
, would enter the water more or less obllquely
and In that case would be twisted like I'll
r wing OF q wind. mill, as occurred In launcl
. ing much smaller dock In one Of the port
a Of the Baltic.
q To guard against this danger, there wa
q placed opposite the centre Of the dock, an
A at about 32s feet from 1t, large reel @
!. cylinder, upon which was rolled, with equa
I, tension, two white hemp hawsers Of 121
4 inches diameter. The end Of each hawse
was secured to the extreme launching @
, bilge-ways, so as to hold them equally whel
the lashlngs were cut. The brake OF tn
cylinder or reel was large lever at the ex
tremity of which was suspended a weight
Z which would only permit Il to turn with al
effort OF about 10 tons, which each OF tn
hawsers could stand. This strain of 20 ton
seems, at first sight, very little to exercise
n sensible influence upon the motion of q bod
r Weighing Abs tons; but, considering thG
Ia the weight upon the ways has only one hft
Of the total weight--that Is, 625 tons-an
the tendency down the plane was only OF
sixteenth of the weight, It will be seen thu
" at the moment Of the commencement of mi
g tlon, which Is the most critical, the resis
y ance Of the brake on the side which woul
!, tend to move first, would absorb two flftl
of the effort, which was Judged to be SUD
, Client.
: Experience Justified these calculations, 70
8 one end of the dock commenced TO move
h few seconds before the other, which was sui
llclet to cause the regulator to act, and pei
mIttcd the other end to get into line. Not
outstanding the rapidity of motion acquire
+ from velocity OF 81 feet per second, tn
tension OF the hawsers was sensibly the SAINT
and the lower angle of the dock entered tn
water with an almost mathematical paral
: lcllsm.
D The complete success Of this delicate opei
, alton passed without notice, and It Is onl
by comparison that Its importance can b
Judged of, and TO this end tho launching Q
, the Great Eastern Is referred 10. In tina
+ large vessel, though about three times heavie
than the dock, the conditions for success
were more advantageous, as the ground wa
In every resDect sOlld and sufliclent to arm