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5 in. thick, riveted to the protective deck, and projecting outside the general
surface of shell plating, to which it is secured by stout angle-bars inside and
outside the ship ; (d) the vertical armour plate, 2 in. thick, riveted to the
stem and to the bottom plating on each side.

To prevent the fouling of anchors, the angular spaces between the
ram plate and the bow plating are filled with wood and protected by thin
steel plates.

The model also shows a " collision " bulkhead extending from the
vertical keel to the upper deck across the vessel. All water gaining
access below or between any of the horizontal platforms is by this means
confined to the cellular spaces before this watertight screen. In some
later vessels these spaces were tightly packed with cork, which gave some
elasticity and also prevented the entrance of any considerable weight of
water.

667. Half midship section of H.M.S. "Royal Sovereign."
(Scale 1 : 24.) Made by the Admiralty, 1893. Plate VII.,
No, 2. N. 2016.

This shows the structural arrangements amidships of the " R " class of
battleship.

The flat keel is built up of two thicknesses of steel plates, and upon this
is secured by angle-bars a vertical keel plate, to which is attached the main
transverse framing of the ship. These plate frames are of steel, generally
375 in. thick: they are about 5 ft. deep at the centre line of the



200

decreasing to about 2-5 ft. at the bilge, and again increasing to about 3' 5 ft.
below the armour shelf : at intervals of 24ft. watertight frames are employed.
The longitudinal framing of the ship consists of six continuous fore-and-aft
plate girders. The lower portion of the hull is rendered cellular by the
addition of a watertight inner-bottom of steel reaching to the third longi-
tudinal girder on each side.

The first longitudinal girder, or armour shelf, is 6 ft. wide amidships, and
upon it rest the heavy transverse plate frames, about 4' 5 ft. wide, which,
combined with longitudinal intercostal girders, support the 18-in. steel
armour plates. The shell of the ship behind the vertical armour is formed
of two thicknesses of steel plate, and to this a teak backing is bolted.
Horizontal protection is given by a steel deck, formed of two thicknesses of
1 '5 -in. plates, which is secured to the top of the armour belt by tap bolts.

An important feature in this type of vessel is the secondary armour
plating, 5 in. thick and 6 ft. deep, which extends for a length of 150 ft.
amidships and gives with the primary armour a protected freeboard 9 5 ft.
high. The machinery and vitals of the ship are further protected by coal
spaces above and below the 3-iii. protective deck.

At the level of the top of the secondary belt is the niajn deck, which
extends unbroken for the whole length of the ship, and upon which the
officers and men are berthed. On this deck are placed four of the ten
6-iii. guns which form the principal part of the secondary armament of
the ship.

668. Sections of armoured side of H.M.S. " Royal Sovereign."
(Scales 1 : 8 and 1 : 12.) Made by the Admiralty, 1893.

N. 2016.

These show in detail the principal protective arrangements adopted in
the nine battleships of the " Royal Sovereign " class built 1890-4.

The lower belt of side armour extends for two- thirds the vessel's length
amidships and is terminated by transverse armour bulkheads ; it is 8*5 ft.
in width (5 ft. below water-line and 3 5 ft. above) and has 18-in. maximum
thickness. It is of the "compound" type, i.e., the outer face of hardened
steel and the inner portion of softer and more ductile material to obviate
the whole plate cracking under the impact of projectiles. Each plate weighs
about 30 tons and is fastened by bolts 5 5 in. diam. and 2 7 ft. long
screwed into the back of the plate and thus avoiding the drilling of the
hardened face. Details of these bolts are shown ; a long steel sleeve passes
over the inner end and bears against the 1-in. skin plating; outside of this
are two plate washers with india-rubber between them, forming an elastic
bed upon which the securing nut is screwed.

The upper belt of 5-in. armour extends over nearly one-half the amidships
length of the ship and is 6 ft. in width.

Between the two armour belts is the 3-in. horizontal deck-plating, worked
in two thicknesses ; this affords additional protection to machinery spaces
and magazines from gun-fire and the splintering of explosive shells. Upon
this deck is also fitted a cofferdam, or double-bulkhead, to prevent the rapid
spreading of loose water to the central hatchways. -

669. Half midship section of an iron ship. (Scale 1 : 16.)
Lent by Lloyd's Register of British and Foreign Shipping,
1876. N. 1438.

This represents a typical iron-built merchant vessel of about 2,000 tons
register, conforming with Lloyd's rules- for the highest class.

The keel is a vertical solid bar ; the keelson a plate girder above the
floors and carrying the heels of the pillars. The frames are of two angle-
bars reversed, while the beams are of bulb-bars with two angle-bars riveted
to them. The shell plating is in longitudinal strakes alternately raised and
sunken. Details are shown of a watertight bulkhead, of bilge and side-
stringers and of tie-plates to the deck beams. Further information is given
by a drawing on the wall.



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670. Half midship section of a merchant vessel. (Scale
1 : 12.) Made by the Admiralty, 1887. N, 1743.

This shows the framing of a large merchantman fitted with a bar keel,
a deep middle-line keelson, and three tiers of beams.

It shows a complete transverse frame, built on the reversed angle-bar
and solid floor-plate system, with details of the connections to shell plating,
decks, side and bilge keelsons, also to the stringers in the hold.

671. Midship sections of merchant vessel with cellular
bottom. . (Scale 1 : 12.) Made by the Admiralty, 1887.

N. 1744-5.

These show a merchant ship of moderate dimensions, built with a double
bottom and a centre-through-plate keel.

The portion of double-bottom space shown in the completed section
includes a typical transverse frame formed upon the " bracket " system,
each part between the continuous longitudinal girders being built up of
short plates and angle bars. This model shows also the construction of [a
strong web-frame fitted above the " margin " plate or outside boundary
of the cellular bottom. It consists of a vertical plate or web, stiffened
by double angle-bars on the inner edge, and supported by side stringers
and diamond plates. Such frames [take the place of the ordinary frames
and compensate for the loss of deck beams in the way of the hold and
machinery spaces.

The other model shows a section of the double-bottom space at a
position intermediate to that described above. Here the upper frame bar
is worked intercostally, while the lower frame extends continuously from
the margin plates across the keel, piercing the longitudinal girders but
giving transverse support to the shell plating.

Both of these sections are taken at non- watertight stations. To sub-
divide the double bottom into the requisite number of cells, transverse and
longitudinal watertight frames are fitted at intervals of from four to eight
frame-spaces apart. Each bracket composing the former has a solid web
and is connected by closely- spaced rivets to the inner and outer skins and
to the adjoining longitudinals. Solid plate frames, lightened by means of
manholes, are introduced to give increased rigidity beneath the engines and
boilers in all ships, and also beneath the barbettes and heavy armament in
war-vessels.

The Admiralty system of " bracket " framing and watertight frames is
shown in Nos. 677-80.

672. Model of bow and stern framing of a merchant vessel.
(Scale 1 : 24.) Made by the Admiralty, 1887. N. 1787.

These are sectional elevations of the extremities of a single screw steel-
built merchant ship of the largest type.

In the fore part is shown the collision bulkhead, extending from keel to
upper deck, together with the watertight decks and flats for localising the
effects of damage to this end of the vessel. The full details are shown of
the ordinary transverse frames and of the specially deep transverse floors,
which, in conjunction with the " panting stringers " (shown longitudinally
between decks), are fitted to stiffen the shell plating of ships with these long
fine bows.

In the after part similar details of construction are shown, together with
the method of framing and plating the hull in the neighbourhood of the
single propeller shaft.

The rudder with its attachments to the stem frame is also represented.
This stern post is of the forged solid-bar type, as is also the stern post ; the
modified sections obtainable when steel castings are used are shown in
several other models.



202

673. Model of " turret-deck " vessel. (Scale 1 : 24.) Made
in the Museum, from particulars supplied by Messrs.
W. Doxford and Sons, 1900. Plate VII. , No. 3. N. 2183.

This sectional model shows in detail the midship length of a cargo
steamer of the " turret-deck " type patented in 1891 by Mr. C. D. Doxford.
The ship represented, moreover, besides differing in its above- witter form
from the usual " tramp " steamer, exhibits several interesting innovations in
shipbuilding practice introduced to secure strength while economising
labour and materials.

The leading detail in the construction is the general adoption of the
Bell-Rockliffe system of "joggle" plating, patented in 1887, whereby the
use of " liners," or packing pieces, between the frames and the plating is
avoided, and a direct saving in the weight of hull effected. This system
has now been followed to some extent in the plating of ordinary merchant
vessels and in modern warships, the edges of the plates being either pressed
to the required form, or rolled in a special machine patented by Mr. C. D.
Doxford in 1894 and shown in an adjacent photograph.

Another detail in which the construction differs from general practice is
in the use of " plate flanges," instead of rolled sections, for stiffening the
main watertight bulkheads and for connecting the framing of the cellular
bottom.

For the main transverse framing of the ship, " Z " sections are used
throughout, with bulb angle-bars forming the upper parts : the curvature
of this " harbour "-deck framing, in conjunction with the thick shell -plating,
offers considerable resistance to the stresses to which this portion of a ship
is subjected in a sea-way. At intervals of about 20 ft. throughout the
vessel, specially strong transverse frames are fitted as shown at the end of
the hatchways ; these frames are connected at the height of the harbour-
deck by athwartship beams of double channel -bar supported by pillars of
similar construction.

The lower, or " tween," deck is intermediately supported by a combi-
nation of fore-and-aft girders and widely-spaced pillars, so arranged as not
to seriously interfere with the stowage of cargo. These, together with a
portion of a large cargo hatch fitted with " shifting " beams, are shown on
each deck, and the model also indicates the construction of the " hold "
below.

The upper or weather deck of an ordinary merchant steamer is replaced
in the " turret " type by the harbour deck, from the central portion of which
rises a narrower section, or " turret," extending the full length of the vessel
and supporting the working platform of the ship. The constructive value
of the whole turret-erection is, that it forms an integral part of the ship in
a position in which the material possesses great efficiency in resisting the
hogging and sagging stresses ; at the same time the interior acts as a
" feeder " for bulk or grain cargoes, in a similar way to Price's self -trimming
hatchways (see No. 722).

Like the " whaleback " steamer, so successfully adopted as a freight
carrier on the American lakes, the "turret " vessel has some advantages in
construction and registration over a vessel of the ordinary type, arising
from the absence of sheer and the reduced deadweight of the hull, while
being moreover suited for ocean navigation.

674. Model of "tank" steamer " Paul Paix." (Sca]e 1:24.)
Lent by Messrs. R. Craggs and Sons, Ltd., 1909. N. 2516.

This represents a portion of the midship section of an oil-carrying steamer
built by Messrs. R. Craggs and Sons at Middlesboro' in 1908 upon a system
of construction introduced by Mr. J. "W. Isherwood.

The value of longitudinal framing in iron ships was demonstrated as
early as 1834 by Mr. J. Scott Russell, who built a small steamer entirely
without transverse frames a number of fore-and-aft stringers, riveted
internally along the plate edges, supplying all necessary structural strength :



203

the famous " Great Eastern," completed in 1859, likewise embodied this
principle (see models and drawings in Ship Gallery). Since this time
several attempts have been made to give longitudinal frames a more
important place in shipbuilding, but with no great practical success.

The " Isherwood " system re-arranges on this principle the material
used for the main framing of a ship. The ordinary closely- spaced transverse
frames and beams are supplanted by closely-spaced longitudinal frames at
the bottom, sides and decks, while the necessary transverse strength is
supplied by widely- spaced plate girders or frames extending completely
round the inside of the hull ; an efficient spacing of the latter has been
found to be 12 to 16 ft., and of the former 27 to 29 in. By this new dis-
position of framing, it is claimed, all structural requirements are met with
less weight of material. Other advantages claimed are : Greater simplicity
in preparing and erecting the constructional parts ; less liability to serious
damage by collision ; easier accessibility for maintenance and repair ;
increased hold space, in ordinary cargo steamers, owing to fewer beam knees
and bilge brackets.

In a modem oil-carrying steamer, the numerous " tank " bulkheads
necessary give a natural increase of transverse strength, and hence some-
what simplify the adoption of this system ; two transverse plate-frames
only are in this case required between consecutive bulkheads. As shown by
the model, these plate-frames are divided by the centre-line bulkhead, a
complete half -frame being fitted on each side. Following the usual practice
in vessels of this type, all longitudinal framing is cut off at each oil-tight
bulkhead, and the continuity of strength maintained by gusset or corner
plates (see No. 300). In the " Paul Paix " the bulb-angle framing at the
sides connect with the horizontal stiffeners of the bulkhead, and both the
framing and stiffeners increase in dimensions with their depth below the
water-line ; each transverse bulkhead is further supported by vertical web-
stiffeners worked on the opposite side to the horizontal stiffeners. Each
strong transverse frame is built up of - 45-in. plating and varies in depth
from 20 in. to 39 in. ; the plating of decks and sides is 5 in. thick. The
principal scantlings have been approved by Lloyd's Register, Bureau Veritas,
and the British Corporation.

The " Paul Paix" is of the single-deck type with a continuous expansion-
trunk above her main cargo spaces. She has a dead-weight capacity of
6,200 tons, and can load to full draught with light motor spirit, which
is carried in 16 separate tanks. Oil fuel is carried in double-bottom
compartment s .

The principal particulars of the vessel are : Gross register, 4,196 tons ;
length, extreme, 367 ft. ; breadth, 49 -4 ft. ; depth, moulded, 28 ft.

At the present time (1910) the " Isherwood" system has been adopted in
about 45 vessels, built or building. Adjacent photographs show details of
the construction of the " Craster Hall," a two-decked vessel built 011 this
system for ordinary cargo purposes, in 1908-9. Her principal particulars
are : Dead-weight capacity, 7,300 tons ; gross register, 2,759 tons ; length,
392 5 ft. ; breadth, 50 ft. ; depth, 29 ft.

675. Section of bar keels and centre-plate keelsons.
(Scale 1 : 4.) Made by the Admiralty, 1887. N. 1730-1.

These illustrate two methods of combining, in steel- built vessels, a solid
bar-keel with a vertical plate keelson.

In (a) the floor-plates are fitted continuously across the keel, the lower
portion of the vertical plate being scored through for this purpose, while
the transverse (frame and reversed frame) angle-bars are butted at the
middle line. The upper portion of the vertical keelson plate is formed into
a continuous longitudinal girder by the addition of double angle-bars to
the top and bottom edges ; a horizontal rider-plate at the upper edge
provides the necessary security for the lower tier of pillars. The forged
lengths of bar-keel are connected together by means of well-riveted scarf



204

joints, and the whole is secured to the general framing of the ship by
flanging the garboard strakes of shell plating as shown.

In (6) both floor-plate and frame-angles are cut off at the middle line
by a continuous centre-through-plate keelson. From the underside of
keel this extends sufficiently above the top of the floors to take two
continuous angle-bars and a bulb-plate ; at the lower edge two side bars,
one on each side, are fitted, the total thickness of the three plates being
usually equal to that of a single bar-keel. When carefully riveted to the
garboard strake, as shown, this is a highly efficient combination, although
the cost of workmanship has militated against its general adoption by
shipbuilders. The butts of upper and lower frame-angles are connected
by short doubling- angles, which are scored through the keelson-plate on the
opposite side of the floor -plate.

676. Section of flat keel and centre-plate keelson. (Scale 1 : 4.)
Made by the Admiralty, 1887. N, 1732.

This construction is largely used for small vessels in the mercantile
marine. A single flat-plate keel, double riveted to the garboard strakes
of bottom plating, is combined with a continuous vertical keelson-plate
provided with double angle-bars to upper and lower edges. The trans-
verse frames extend from the middle-line to the topsides of the vessel
and are connected to the keelson-plate by means of short vertical angles
on each side of the floor-plate; there is also a continuous "gutter plate"
riveted to the reversed frame-bars and to the upper angles of the keelson.

For large vessels, Lloyd's rules require the flat-plate keel to be doubled
for one-half the vessel's length amidships.

677. Model of bracket framing. (Scale 1 : 12.) Received,
1874. N. 1395.

This illustrates the construction of the double bottoms of warships
during the period 1870 to 1895.

It shows two complete " bracket " frames, at non- watertight stations,
and details of their connections with the longitudinal frames ; also portions
of two "longitudinals," one of which serves the purpose of an ordinary
lightened-plate girder, while the other, built of solid-plates with closer-
spaced riveting, serves the additional purpose of a watertight boundary to
the cellular spaces into which the double bottom is divided.

Owing to the greater length, speed, and armament of modem vessels, a
modified form of bracket frame, giving greater strength and rigidity, has
been generally adopted.

678. Model showing cellular construction. (Scale 1 : 4j
Made by the Admiralty, 1887. N. 1735.

This is a transverse section of a double-bottom at the middle -line of the
vessel. It shows full details of the arrangements for connecting the inner
and outer skin plating with the bracket frames and vertical keel.

Butt straps of the vertical keel and of the inner and outer flat keels are
shown, also the covering straps of the butts of the upper and lower keel
angles, with details of the riveting in each case. The practice of lapping
the upper and lower frame angles upon the vertical keel angles is now
discontinued, the former angles being cut shorter so as to avoid the
expensive bending.

679. Model showing cellular construction. (Scale 1:4.)
Made by the Admiralty, 1887. N. 1746.

This shows a portion of the framing and outer bottom plating of a vessel
built on the cellular system.

It comprises one watertight and six ordinary "bracket" frames, with
their adjacent longitudinal girders, and shows the method of constructing
and combining the same ; also the shell plating in the vicinity, with details



205

of the riveting at the butts, edges, and frames. The model further
illustrates a method of disposing the butts of shell plating, whereby two
unpierced strakes are provided between butts in the same frame space.

680. Models showing cellular construction. (Scale 1 : 4.)
Made by the Admiralty, 1887. N. 1733-4.

These show details of the framing and plating adopted in the construction
of the cellular bottoms of warships.

(a) is a watertight bracket frame, extending from the middle-line of the
vessel to the first longitudinal. It consists of a solid plate bounded by a
complete frame of angle-bar which is connected by closely- spaced riveting
with the inner and outer bottoms, as well as with the vertical keel and the
longitudinals. When caulked this transverse frame forms a watertight
partition between two of the many cellular spaces into which the double
bottom is divided.

(&) shows the construction of an ordinary bracket frame, and is typical
of the general structure of the frames between the watertight ones.

Each model also illustrates a method of securing a longitudinal bulkhead
and its vertical stiffeners to the inner bottom plating.

Details of the more recent practice in regard to the construction and
fitting of these frames are shown in model No. 667.

681. Model of outer bottom plating of a warship. (Scale 1 : 4.)
Made by the Admiralty, 1887. N. 1736.

This represents a portion of a double-bottom and details of the shell
plating in the neighbourhood of the keel.

The methods of fitting butt straps to the vertical keel plates, to the
inner and outer flat keel plates, and to the first or garboard strakes of the
outer-bottom plating are shown, together with the covering strap of a butt
of the lower angle-bar to the vertical keel.

The lower portion of this cellular bottom, after being carefully caulked
and tested, is covered with a layer of cement, which protects the structure
from the corrosive and mechanically wearing effects of bilge-water. The
cement is thickest near the keel, where it rises to the height of the circular
drainage holes shown in the bracket frames, thus facilitating the complete
pumping out of these compartments.

682. Model of outer bottom plating showing disposition of the
butts. (Scale 1:4.) Made by the Admiralty, 1887.

N. 1747-8.

These illustrate two systems of so arranging the butts of shell plating as
to give uniform distribution of these lines of transverse weakness.

(a), with plates four-frame spaces in length, shows three passing strakes
of plating between each pair of butts in the same frame space.

(&), with plates five-frame spaces in length, has four passing strakes
between consecutive butts in the same vertical section.

For illustration of an arrangement in which only two passing strakes
break the line of consecutive butts, see No. 679.

683. Model of shell plating showing " stealers." (Scale 1 : 4.)
Made by the Admiralty, 1887. N. 1749-50.

The great difference between the girth of a vessel amidships and at the
extremities renders it necessary to end some of the strakes of the outer
bottom plating before reaching the bow or stem ; these shortened strakes
are known as " stealers.''

(a) and (6) show in elevation a method of working a stealer in a sunken
or a raised strake respectively.

The smaller models (c), (d), (e), and (/) are transverse sections of the
above, taken through the dotted lines marked " A B " and "CD." They
show details of the tapered rebates and edge connections, whereby the two
strakes are worked into one and then efficiently secured.



206

684. Models of beam, frames, and stringer connections.
(Scale 1 : 4.) Made by the Admiralty, 1887.

N. 1737 and 1768.

These show the usual attachment between a ship's beam, a transverse
frame, and a deck stringer ; also the connection between a deck stringer,
a frame, and (a) the sheer strake of a composite-built vessel, (6) the shell
plating of a steel-built vessel.

The latter model shows, in addition, portions of the wooden sheathing
and deck planking, as well as a "gutter- way" for carrying water from
the deck to the scuppers ; this gutter is formed of two continuous longi-
tudinal angle-bars. The transverse frame is here of Z-section, while



Online LibraryScience Museum (Great Britain)Catalogue of the naval and marine engineering collection in the ... museum .. → online text (page 28 of 58)