The Roanoke times. [volume] (Roanoke, Va.) 1890-1895, 1892-11-16
LAUNCHING A VESSEL
OLD TIME METHODS ARE ADAPTED
TO MODERN CONDITIONS.

Guesswork Has Given Place to Fine CAL
c"lations = Tho BuiIders' Supremacy
Anxious Moment Whom tho Vessel Is
Poised ON tho Ways.
The launch of a modern vessel does not
differ materially from one of older DAYS
except in detail and enlarged response
oillty. 1t is now question of Inathemat-
les rather than of personal experience. 1t
Is now matter of applied science and not
one OF fortunate guesswork. The con-
structor in these days does not fix the scale
OF the inclined plane down which the YES
sci will glide by his experience in such
matters; does not smear the tallow OH the
ways until 1t seems to be enough; does not
adjust the size of the ways to suit his
fancy. Vessels that cost from 81 900, 900 to
S3,OOO,0O0 are too valuable for the running
OF large risks, and hence the equation, the
formula, the methods of applied mathe-
matics, have supplanted old time ways of
trusting to individual Judgment and good
luck.
Three things are absolutely necessary in
launching n vessel in tidal waters-the
launch must take place on time, must be
OF moderate speed, and all straining of the
particular that the greatest responsibility
rests nowadays A wooden vessel may be
subjected to great strain, her seams NAV
open and, as naval constructor recently
put 1t, she may almost be stood on her
head" and yet escape serious damage in
launching. 'She seams will close again
and the timbers and anks>adjust them
selves. Not so with iron oT steel vessels
II the plates are strained, the rivets bent
or broken, the injury is permanent and q
matter of the gravest Importance
Preparations for u launch are begun be-
lore the keel is laid. The incline of the
plane has first to be figured out 1t gen
orally varies from one-half inch to one inch
TO the foot Vessels of Il large tonnage
have less inclination than smaller ones.
The City of Paris had only one-half an inch
inclination when she was launched. The
cruiser Columbia, SO long known rs the
Pirate, and recently launched att Cramps
shipyard In Philadelphia, glided into the
water mt an inclination of thirteen-siX-
teenths of an inch to the foot. She went
down the ways like a race horse Mr. Nixon.
the constructing engineer of the Cramps,
planned to have her in the water in thirty
seconds after she started. She made it i'm
twenty-ninc. More vessels are launched
Mt an inclination of thrcc-quartcrs of an
inch to the foot. however, than ut any other
plane.
The ways, as is generally known, con.
sist OF two parts, the ways proper and the
cradle The ways proper are stationary
and firmly fastened to the ground The
cradle rests on top of the ways and I'D
against the vessel and slides into the water
with the ship Between the ways prone,
and the cradle the tallow is smearcd. This
is generally spread five-eighths of an inch
thick and must be of the highest grade.
That used by the Cramps is made in Phil.
adclphia and costs from seven to eight
cents pound. About II 900 pounds was
used in the launching of the Pirate. 1t is
heated in big kettles in tho shipyard and
spread on by hand. In the case of the
Pirate the weather was so warm that there
was serious danger that the tallow would
melt and run away. Mr.. Nixon therefore
mixed 10 per cent. stearine with it, He
also played n hose OH the tallow, and went
so far as to sit up nights with the mixture
to watch the effect of the weather on it.
The stcarine hardened the tallow and the
launch was successful.
Perhaps the most important element TO
be considered in the launch of today is the
buoyancy OF the water and it's effect on
that part of he vessel which is still OH the
stocks after probably one-half of the vessel
is i'll the water. Recently one of the new
English battleships of the II, 0OO-ton class
was wrecked at her launch. The buoyancy
OF the water lifted her up mt the heels and
threw her immense weight forward on her
shoulders, crushing the frames and the
launching ways, and running the boat.
The modern naval constructor reduces this
question OF buoyancy to matter of mathc
MATES Mt once. He starts with the oucs-
ton of specific gravity of the vessel. If
there were no water for the ship to slide
into she would continue in the line of the
ways until the center of gravity would get
over the end of the ways and then she
would tilt. But the water keeps her from
dropping down and holds the vessel in the
line of the ways. This water is the safety
valve of the launch, but it must not be too
safe. While the moment of buoyancy
must always be greater than the moment
OF weight, it must not be so much greater
as to throw terrible pressure on the for
ward end of the vessel and wreck it.
Having arranged all these things, n day
and an hour are set for the launch the
time of the high tide being the chief factor
to be considered. Most of the props are
taken down and the vessel rests on the keel
blocks and one or two sets of stocks at the
sides. The ways and cradle have been fixed
i'll place, and wedges have been adjusted
above the cradle and under the poppet
blocks on which she rests. A battcring
ram consists OF four men to piece of stout
timber. These four men take care of four
wedges. The signal is given and an i'm
mense clatter begins as the men drive
home the wedges for five minutes. The
vessel is lifted just clear of the keel blocks
and now rests on the ways. Alternate keel
blocks are now knocked away, beginning
Mt the stern. Another "wcdgng up" fol-
lows, and then all the props at the sides
are removed.
After rest the third wedging comes,
and then all the keel blocks are knocked