Encyclopaedia Britannica > Volume 21, ROT-Siam

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of Trade to know whether the Board oM>£Kfl the Bc,lr'1
powered under any eiren.netancce to insist m to^ZuTJZ
watertight compartments when employed in conveyance of mad?
and passengers, observing that the Admiralty were sHH nf .
that the regulations in fo^rce prior to the AiSndment let oTS
in respect of contract packets should not have been relaxed"
they considered such vessels should have compartments so arranged
that if any one of them became filled with water the WS0f
buoyancy thereby occasioned should not endanger the safe t of
the ships, as recommended by them in their commnnWi Af-v
STs^fh1^ ^ ^ BoarS Sr^eT^'sfp?
tember 1863) that their surveyors no longer had any power to
require given watertight partitions to be fitted in passeiLr steam
ships -though they agreed with the Admiralty in thinking that
whhVfffi S Tryinf imsfn8ers and “ails should be provided
with a sufficient number of watertight partitions,—and had no
reason to suppose that the Admiralty would not insist on snefi
partitions being fitted in all steamships employed in conveyance of
mails. 1 hey further say that the enactments in the Adrof 1854
were repealed, not because of any doubts as to the necessity of
proper and sufficient watertight partitions, but because those
enactments which required only two of such partitions for all sizes
It wasTund thS'ini C°me Prctically useless or mischievous.
It v as found that m large vessels more partitions than the Act
reqmred were necessary to secure the safety of the ship, and it w2
t bought better to leave builders and designers unfettered in pro¬
viding extra strength and security to meet the various forms
sizes, and descriptions of ships than to tie them down by general
statutory regulations which could not be so framed as to mfet the1
varying wants and circumstances of the shipbuilding trade
i ;na “tu™ by the Board of Trade to the House of Commons
dated 11th August 1875, setting forth the instructions issued to
ckuLirSs—mder the Merchant ShiPPing Acts, 1854 to 1873,
HpIsIilfSSisagg
ss ?ass 1 aE
r.nne®' T> Th!s “gulation has been reissued in the latest instructions to
uent _ Board of Trade surveyors, dated 1884. It thus comes about that
iubdivi- the number of bulkheads forming watertight compartments the
of number of doors in them, and how they are fastened^ are made the
ron and subject of consideration by the Board of Trade at their inspections •
feel but th® fact is that the great majority of ocean-going Steamers
hips. are not divided into watertight compartments in afy effidenl
manner and many losses in collision, grounding, and swamping are
due to this. Although all steamships have some bulkheads and
some have many bulkheads, they are as a rule distributed in such
a way, or are so stopped below the water-level, that for flotation
purposes after perforation those lying between the foremost
colhsmn bulkhead and the after bulkhead through which the screw
shaft passes are practically useless.
, yVltl1 .the exception of some four hundred ships, there are no iron
steamships afloat which would continue to float were a hole made
m the bottom plating anywhere abaft the collision bulkhead and
°r W]licl1 would not f°under were water
admitted through breaches made by the sea in weak superstructures
and deck openings. Of the four hundred ships referred to as
having properly designed bulkheads two hundred are essentially
cargo-carriers. They are generally built with five subdivisions,
the machinery space being one. Iron sailing ships are without
erxeptwn undivided into compartments. They have by law a
collision buikhead near the bow, and that is all. Between June
1881 and February 1883 there were about one hundred and twenty
iron steamships lost, of speeds of nine to twelve knots, not one of
which was well constructed according to the opinion of the council
oi the Institution of Naval Architects.
. ff may be said that wooden ships were not divided into water-
tight compartments, but it must be remembered that in a wooden
ship there is far more local resistance to a blow either in collision
“ by grounding, and that a wooden ship takes a much longer
time to settle down in the water and sink. Also, when wood was
employed for passenger and trading ships speeds were much lower
and traffic and risks of collision very much less.
The shipbuilding registries prescribe rules for the government
SHIPBUILDING
817
have been scfcarefu 1 ly framed cel;tificate> and these rules
built ships aro as a ruWp f 80 “forced that English-
(8th June 1882) rule of thPL^^T ?0nmrUCteti' The recent
important subject of divAfim i Jfmdon L1°yd s register as to the
* "ay be hoped “ " t*lm> “*
a watS'htbmkhead6 built ^PreLsonablP (mfne'r°f0m buIkbeads, to have
vessel. In steamers 280 feet Ions- ane G bls*'ance from each end of the
be fitted in the main hold extfnmnv to thBan addltlonal bulkhead is to
midway between the collision to the ,maln or upper deck, about
of 330 feet long and above an additional limkh1 b.u!kbeads i and in steamers
hold eXtending t0 the sajne height.1”nal bulkhead 13 to befitted in the after
plates to thefupper1 d^k S1°n bui}jbead in a11 cases to extend from the floor
the floor platesPtPo the upper deck 1n vfssel's00^buIkh+eads to extend from
and to the main deck in spar- and awnfn^r tha0ne’ ^ or three decks,
Britain Kt »“ tkS
amount Zd in inerf cmXtl PmT °i shil,I>iD« h‘
strahirtfinPaer8hfn’ TT* to » «r“,er variety of Strains
property are incurred ^ A +P “ ^bich greater risks of life and to which
disturbing forces in action r.iti01'01^- P.ractlca^ knowledge of the ships are
oomhinafous cnrbraeed in „s
an Some of these forces always act, whether the ship be Kst
a iuf Ssion sh„raayb6frr " stil> ™ter?and will be
t rest it cast on shore ; and, when there, she may be resting on w
side1 ^,coutmuous bearing, with a support from a portion of her
de, oi she may be supported m the middle only, with both ends for
a greater or less length of her body left wholly unsupported or shJ
may be resting on the ends with the middle unsupported or under
thJ starwS^Im lt?e3Jlcir“ms‘a?“s i »"1 "miai all those
. . onuumstciiices : ana unaer a 1
th fS%TlWlll Vai'y 111 .heir direction and in their intensity.
it the ship be m motion the same disturbing forces may still be
in action, with others in addition which are produced bTa state of
motion. When a ship is at rest in still water, although the upward
pressure of the water upon its body is equal to the total weight of
nortSfnfrt!068 n°f f°Uow that the weight o/every
portion of the vessel will be equal to the upward pressure of that
portion of the water directly beneath it, and acting upon it, on
t e contrary, the shape of the body is such that their weights and
pressures are very unequal. g ana
If the vessel be supposed to be divided into a number of laminse
of equa! thickness, _ and all perpendicular to the vertical longi¬
tudinal section, it is evident that the after lamina; comprised in
the overhanging stern above water, and the fore laminae comprised
m “e projecting head also above water, cannot be supported bv
any upward pressure from the fluid, but their weight must be
whoHy sustained by their connexion with the supported parts of
the ship. The lamina;, towards each extremity immediately con¬
tiguous to these can evidently derive only a very small portion of
them support from the water, whilst towards the middle of the
ship s length a greater proportionate bulk is immersed, and the
upward pressure of the water is increased.
A ship floating at rest under the view just taken of the relative
displacement of different portions of the body, if the weights on
board are not distributed so that the different laminae may be
supported by the upward pressure beneath them as equally as
possible, may be supposed to be in the position of a beam supported
at two points in its length at some distance from the centre and
with an excess of weight at each extremity. At sea it would be
exposed to the same strain ; and if supported on two waves whose
crests were so far apart that they left the centre and ends com¬
paratively unsupported, the degree of this strain would be much
increased. The more these two points of support approach each
other, or if they come so near each other that the vessel may be
looked upon as supported on one wave, or on one point only in
the middle of her length, the greater will be the tensile strain on
the upper portion and the crushing strain on the lower portion of
the fabric of the ship. A vessel whose weights and displacements
are so disposed as to render her subject to a strain of this kind
beyond what the strength of her upperworks will enable her to
bear, will tend to assume a curved form.
The centre may curve upwards by the excess of the pressure
beneath it, and the ends drop, producing what is called “hogo-ino- ”
I he main remedy for these evils is in the strength of the deck and
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