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Monday, 4 June, 2001
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Southampton
Class Light Cruiser
Written
by
James Davies
|
Southampton
Class Light Cruiser Key Data
|
|
Country
of Origin:
|
Great
Britain.
|
|
Manufacturers:
|
Devonport
Dockyard (Plymouth), Scotts (Greenock), Vickers-Armstrong (Tyne),
John Brown (Clyde)
|
|
Major
Variants:
|
Southampton
class, Liverpool class, Edinburgh class
|
|
Role:
|
Reconnaissance,
commerce protection, convoy escort
|
|
Operated
by:
|
Royal
Navy
|
|
First
Laid Down:
|
October
1934
|
|
Last
Completed:
|
November
1937
|
|
Units:
|
HMS
Southampton, HMS Newcastle, HMS Sheffield, HMS
Glasgow and HMS Birmingham
|
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Cruisers were formally defined in the
1930 London Treaty as "Surface vessels of war, other than capital
ships or aircraft carriers, the standard displacement of which exceeds
1,850 tons (1,880 metric tons), or with a gun above 5.1 inch (130 mm)
calibre". These were further sub-divided in to two sub classes:
heavy cruisers, which carried guns between 6.1 inches (155 mm) and eight
inches (203 mm), and light cruisers with guns of six inches (152 mm) or
below. The Southampton class cruiser is a light cruiser.
Southampton class ships
are the original variants of the Town class cruisers. Five Southampton
class cruisers were built by Great Britain (HMS Southampton, HMS
Newcastle, HMS Sheffield, HMS Glasgow and HMS Birmingham),
entering service just prior to the start of the Second World War. All
apart from HMS Southampton survived the war, although all of the
ships were damaged in action.
Despite being designated
as light cruisers, the advantage of firepower between the heavy and light
cruisers did not always lie in ships with the bigger guns. In particular,
the heavier eight inch gun took longer to reload, and because of this
the six inch guns could put a heavier weight of shell out per minute than
the eight inch guns. This was offset by the increased range of the eight
inch guns. This meant that with good visibility the advantage clearly
went to the heavy cruiser, with its ability to severely damage a light
cruiser before it could get in range to use its guns. However in conditions
of poor visibility, or at night, the increased range was of no benefit,
and the light cruiser was at an advantage as its faster-firing weapons
could inflict more damage in a shorter period of time.
Overall, the Southampton
class was seen to be a success, with proven ability to stay afloat and
continue to fight after sustaining considerable damage, effective main
guns, adequate armour and sufficient speed - all the qualities of a good
cruiser. In common with all ships of their time the Southampton class
was shown to be initially lacking in air defence, although as the war
progressed significant improvements were made to the anti-aircraft guns
and this deficiency was rectified.
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In 1922 the Washington Treaty placed
limitations on aircraft carriers and on the number of ships over 10,000
tons displacement (‘capital ships’). Ships below 10,000 tons were only
limited by the size of the guns, which was fixed at a maximum of eight
inches (203 millimetres). Further limitations were imposed in the 1930
London Treaty, putting a cap on the total tonnage of cruisers for the
first time. In addition, the total number of heavy cruisers were limited
to 15 for Britain.
The Southampton class
cruiser was conceived as a light cruiser to fit within the limits set
by the 1930 treaty. Under heavy criticism, twelve six inch (152 mm) guns
(in four turrets) were selected as the main weapons. Pressure to increase
this to 15 guns (to match the Japanese Mogami class and the American Brooklyn
class) was resisted, on the grounds that this would break the 10,000 ton
limit set by the treaties, although given the generally liberal interpretation
of ship displacement by other powers the refusal appears strange. Under
normal operating conditions the guns could fire eight rounds per minute
each, and had a maximum range of approximately 25,500 yards (23,317 metres).
Each round weighed 112 pounds (50.8 kg), and (unlike the rounds for eight
inch guns) could be manually handled in the event of power failure.
Armour for the ships
was chosen to provide some protection against the eight inch shells fired
by heavy cruisers (which the Southampton class might be expected to fight),
although they could not be expected to withstand the much heavier guns
of capital ships.
Aircraft were provided
for a reconnaissance role, and having experienced problems in other ships
maintaining aircraft in an air-worthy condition the ships were fitted
with two aircraft hangars - the first British cruisers to be so equipped.
The aircraft were launched by catapult from the ship, and were recovered
by crane after landing on the water. The chosen aircraft was the Supermarine
Walrus, which was a single engine amphibious biplane. It had a crew of
four and a maximum speed of 135 miles per hour (217 kilometres per hour).
It was armed with one 0.303 inch (7.7 mm) machinegun in the front (in
an open position in front of the cockpit), one or two 0.303 inch (7.7
mm) machineguns in the aft dorsal position (again in an open position),
and could carry 600 pounds (272 kg) of bombs or depth charges.
Eight four inch (102
mm) guns were chosen for dual purpose air defence and short range weaponry,
and had a rate of fire of 20 rounds per minute. These were supplemented
with two four barrelled pom-poms, which were a cut down version of the
eight barrelled weapon fitted to larger ships. These guns fired 115 rounds
per minute per barrel, and were effective out to 1,100 metres (1,203 yards).
Finally, eight 0.5 inch (13 mm) machineguns were installed in two mounts
of four guns each, although these were found to be prone to jamming. The
pre-war lack of appreciation of the threat posed by aircraft can be seen
in this light selection of anti-aircraft weaponry.
Torpedo tubes were
provided in case the vessel had to go in to action against a capital ship,
which could be expected to withstand six inch (152 mm) guns.
During the war changes
were continually made to the vessels to meet the needs of the areas where
they were operating in at the time, to keep up to date with technological
developments and to reflect war experience. By early 1941 no two ships
mounted the same equipment, and by the end of 1941 there were no unmodified
Southampton class cruisers. The development of each ship through the war
is shown in the 'Major Modifications' section at the end of this document.
[Note: only significant modifications have been shown].
The threat posed by
aircraft can be clearly seen by the rapid increase in anti aircraft armament.
The installation of radar made the aircraft obsolete, and their removal
considerably reduced the potential for fire when under attack.
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Two other variants of the Town class
Cruisers were produced - the Liverpool and the Edinburgh classes. The
Liverpool class (comprising HMS Manchester, HMS Gloucester
and HMS Liverpool) were converted during building from the Southampton
class by slightly increasing the breadth of the vessel, adding a small
quantity of extra armour, and providing a more powerful propulsion system
to overcome the extra weight. They also had better fire control (including
a second director aft for both low angle and high angle), although the
ships were essentially little changed from the Southampton class.
The Edinburgh class
(comprising HMS Edinburgh and HMS Belfast) were designed
from the keel up as an improvement on the Liverpool class. The initial
intention was to provide four turrets each with four six inch guns, with
improvements to the ammunition handling facilities for the main guns.
Other changes in internal arrangement were made, although the final benefit
achieved was questionable. Eventually, due to development difficulties
associated with the quadruple mounts and fears that further delay may
result in the ships being limited in a forthcoming naval treaty, it was
decided to retain the triple mounts. Four additional four inch guns were
also provided, to improve the anti-aircraft capability.
As with the Southampton
class, ships of the Liverpool and Edinburgh classes were considerably
modified during the war, particularly with respect to anti-aircraft weaponry.
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The main objective of the Royal Navy
was to protect the British merchant fleet, and the navy was intended to
meet the enemy fleet at sea and destroy it before it could do significant
harm to merchant shipping (the Admiralty spent much of the pre-war years
planning for ‘the next Jutland’, although the enemy was now seen to be
the Japanese rather than the Germans). Cruisers were intended to act in
a reconnaissance role in support of capital ships and to neutralise enemy
cruisers. They were designed to mix speed with range, endurance and firepower,
and were expected to be able to out-run any ship they could not out-fight.
As the war progressed
cruisers began to see use in roles outside those initially intended. In
particular they saw extensive use in convoy close escort, specifically
to provide increased protection against air attack with their anti-aircraft
capability. Their usefulness in air-defence was recognised quickly, although
a specialised anti-aircraft ship (a converted merchant ship which mounted
the same anti-aircraft armament as a cruiser) was developed to replace
the cruiser in this role. Further use was found in shore bombardment in
support of allied landings.
Cruisers had no role
to play in anti-submarine warfare as their advantages of speed, armour
and firepower were irrelevant.
The Southampton class
cruisers saw wide use in many parts of the world: as part of the Home
Fleet they were present during the Norway campaign at the start of the
war; acted as convoy escorts in the North Atlantic and were involved in
the hunt for the Bismarck; worked with Force D, Force H and as convoy
escorts in the Mediterranean; hunted for blockade runners and escorted
convoys in the South Atlantic; supported the Burma campaign and protected
shipping in the Indian ocean, including sinking tankers supporting German
U-boats; acted as a flagship; supported the Normandy invasion.
The only ship of the
Southampton class to be lost was HMS Southampton. Whilst serving
in the Mediterranean in 1941 the ship was heavily damaged in an air attack
on January 10th. Although still afloat the decision was made to sink her,
and she was dispatched by torpedoes from HMS Gloucester and HMS
Orion on January 11th.
The other variants
fared less well. The Liverpool class served in the Mediterranean, where
two of the three were lost (HMS Gloucester was sunk by air attack
and HMS Manchester was scuttled after being badly damaged by E-boats).
Of the Edinburgh class, HMS Belfast broke her back after passing
over a mine in November 1939 (she didn’t return to service until November
1942, escorting the Russia convoys), and HMS Edinburgh was deliberately
sunk by a torpedo from HMS Foresight after being torpedoed whilst
escorting a Russia convoy (twice initially by U456, then once again
by the German destroyer Z24 two days later).
Thus, of the 10 Town
class ships, one was sunk by enemy action, three were deliberately sunk
after sustaining heavy damage, and six survived the war.
After the war the surviving
ships were modernised and continued in service for some time (HMS Sheffield
being the last to exit service, in 1967, after serving as the flagship
of the Reserve Fleet), with both HMS Birmingham and HMS Belfast
taking part in the Korean war.
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|
|
Southampton
Class
|
Liverpool
Class
|
Edinburgh
Class
|
|
Displacement
|
9,100
tons standard
11,200
tons full load
|
9,400
tons standard
11,650
tons full load
|
10,565
tons standard
12,980
tons full load
|
|
Length
(OA)
|
591
ft 6 in (180.29 m)
|
591
ft 6 in (180.29 m)
|
613
ft 6 in (186.99 m)
|
|
Length
(pp)
|
558
ft (170.08 m)
|
558
ft (170.08 m)
|
579
ft (176.48 m)
|
|
Length
(WL)
|
584
ft (178.0 m)
|
Not
available
|
Not
available
|
|
Beam
|
62
ft 3 in (18.97 m)
|
64
ft 9 in (19.74 m)
|
64
ft 9 in (19.74 m)
|
|
Draft
(Standard)
|
17
ft (5.18 m)
|
17
ft 6 in (5.33 m)
|
18
ft (5.49 m)
|
|
Draft
(Full Load)
|
20
ft (6.10 m)
|
20
ft 6 in (6.25 m)
|
22
ft 6 in (6.86 m)
|
|
Block
Coefficient
|
0.54
full load
|
0.52
[Note 1]
|
0.51
[Note 1]
|
|
Propulsion
|
75,000
SHP (55.9 MW)
|
82,500
SHP (61.5 MW)
|
80,000
SHP (59.7 MW)
|
|
Speed
|
32
knots
30.5
knots full load
|
32
knots
30.5
knots full load
|
32
knots
31
knots full load
|
|
Weapons
|
|
Main
Guns
|
12
x 6 inch (152 mm) in four turrets
|
12
x 6 inch (152 mm) in four turrets
|
12
x 6 inch (152 mm) in four turrets
|
|
Other
Guns
|
8 x 4 inch (102
mm) high angle guns in 4 mounts
8 x 2 pound
(0.91 kg) pom-poms in two mounts
8 x 0·5 inch
(13 mm) machine guns in two mounts
|
8 x 4 inch (102
mm) high angle guns in 4 mounts
8 x 2 pound
(0.91 kg) pom-poms in two mounts
8 x 0·5 inch
(13 mm) machine guns in two mounts
|
12 x 4 inch
(102 mm) high angle guns in 6 mounts
8 x 2 pound
(0.91 kg)pom-poms in two mounts
8 x 0·5 inch
(13 mm) machine guns in two mounts
|
|
Torpedo
Tubes
|
6
x 21 inch (533 mm) torpedo tubes in
two mounts
|
6
x 21 inch (533 mm) torpedo tubes in
two mounts
|
6
x 21 inch (533 mm) torpedo tubes in
two mounts
|
|
Armour
|
|
Side
Belt
|
4.5
in (114 mm)
|
4.5
in (114 mm)
|
4.5
in (114 mm)
|
|
End
Bulkheads
|
2.5
in (64 mm)
|
2.5
in (64 mm)
|
2.5
in (64 mm)
|
|
Magazine
|
1
to 4.5 in
(25
to 114 mm)
|
1
to 4.5 in
(25
to 114 mm)
|
3
to 4.5 in
(76
to 114 mm) [Note 2]
|
|
Barbette
|
1
to 2 in (25 to 51 mm)
|
1
to 2 in (25 to 51 mm)
|
1
to 2 in (25 to 51 mm)
|
|
Turret
|
1
to 2 in (25 to 51 mm)
|
1
to 2 in (25 to 51 mm)
|
2
to 4 in (51 to 102 mm)
|
|
Machinery
|
1.25
to 1.5 in
(32
to 38 mm)
|
1.25
to 1.5 in
(32
to 38 mm)
|
1.25
to 2 in
(32
to 51 mm)
|
|
Miscellaneous
|
|
Aircraft
[Note 3]
|
Two
Supermarine Walrus
|
Two
Supermarine Walrus
|
Two
Supermarine Walrus
|
|
Compliment
|
750
(peace) 930 (war)
|
800
(peace) 980 (war)
|
781
(peace) 950 (war)
|
Note 1: Good approximation, although
the waterline length unknown.
Note 2: The box citadel approach used
in the Southampton and Liverpool classes was abandoned in favour of an
extension of the side belt.
Note 3: Up to three aircraft could
be carried, although one must remain on deck. There is no known case of
three aircraft being carried on any of these ships.
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| Major Modifications up to 1941 |
|
Ship
|
Modifications
In Year (Items Added And Removed In The Same Year Are Not Included)
|
|
Pre-war
|
1939
|
1940
|
1941
|
|
HMS
Southampton
|
None known
|
None known
|
None known
|
None (Sunk Jan
11)
|
|
HMS
Newcastle
|
None known
|
None known
|
None known
|
Added:
9
single 20mm AA
Surface
warning radar
Air warning
radar
Removed:
Machineguns
|
|
HMS
Sheffield
|
Added:
Third
HA DCT.
Air warning
radar
Removed:
Aft
control position and rangefinder.
|
None known
|
None known.
|
Added:
6
single 20mm AA
Air warning
radar
Ranging
radar fitted to LA DCT
Air ranging
radar fitted to HA DCT
Removed:
Machineguns
|
|
HMS
Glasgow
|
None known.
|
None known
|
Added:
Air
warning radar.
|
None known.
|
|
HMS
Birmingham
|
Added:
Third
HA DCT.
Removed:
Aft
control position and rangefinder.
|
None known
|
None known
|
None known
|
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| Major Modifications 1942-1945 |
|
Ship
|
Modifications
In Year (Items Added And Removed In The Same Year Are Not Included)
|
|
1942
|
1943
|
1944
|
1945
|
|
HMS
Southampton
|
N/A (sunk)
|
N/A (sunk)
|
N/A (sunk)
|
N/A (sunk)
|
|
HMS
Newcastle
|
Added:
10
single 20mm AA
Surface
ranging radar fitted to LA DCT.
Air ranging
radar fitted to HA DCT.
Air
ranging radar fitted to pom-pom directors.
Upgraded:
Air
warning radar
Removed:
Aircraft
and catapult
|
Added:
4
twin 20mm AA.
Removed:
6
single 20mm AA
|
None
known
|
Added:
2
x 4-barrel pom-poms
Removed:
X
turret
|
|
HMS
Sheffield
|
Added:
3
single 20mm AA
Surface
warning radar
Air ranging
radar fitted to pom-pom directors
Barrage
directors fitted with radar provided for main guns.
Upgraded:
Air
warning radar
|
Added:
5
single 20mm AA.
|
Added:
8
single 20mm AA
Removed:
Aircraft
and catapult
|
Added:
4
x 4 barrel 40mm
10 twin
20mm AA
Upgraded:
Surface
warning radar.
Removed:
X
turret
15 single
20mm AA
|
|
HMS
Glasgow
|
Added:
4
single 20mm AA
8 twin
20mm AA
Surface
warning radar
Surface
ranging radar fitted to LA DCT.
Air ranging
radar fitted to HA DCT.
Air ranging
radar fitted to pom-pom directors.
Upgraded:
Air
warning radar.
Removed:
Machineguns
|
Added:
2
single 20mm AA.
|
Added:
4
single 20mm AA.
|
Added:
2
twin 20mm AA
4 single
20mm AA
2 x 4
barrel pom-poms
4 single
barrel pom-poms
General
warning radar (air and surface use).
Upgraded:
Air
warning radar
Surface
ranging radar.
Removed:
X
turret
Aircraft
and catapult
Surface
warning radar
|
|
HMS
Birmingham
|
Added:
7
single 20mm AA
Air warning
radar
Surface
ranging radar fitted to LA DCT.
Removed:
Machineguns
|
Added:
8
twin 20mm AA.
Surface
warning radar
Upgraded:
Air
warning radar.
Removed:
Aircraft
and catapult
5 single
20mm AA
|
Added:
4
x 4 barrel 40mm AA
2 x twin
20mm AA
5 x single
20mm AA
Removed:
X
turret.
|
None known.
|
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|
Appendix
A: Surviving Examples
|
HMS Belfast is the only surviving
example of a Town class cruiser. She is moored on the Thames in London,
near to Tower Bridge. At the time of writing she could be viewed from
10 am - 6pm (last admission 5.15pm) seven days per week from March to
October, and from 10 am - 5pm (last admission 4.15pm) from November to
February. The ship is closed 24-26 December.
Visit the Imperial
War Museum's HMS Belfast website at http://www.iwm.org.uk/belfast/belfast.htm.
|
The
ship was extensively altered post-war, and some of the equipment
has been removed, however the ship remains in essence the same as
the cruiser which fought through the Second World War.
|
|
|
Many of the internal compartments are open
to the public, including the forward magazines (upper magazines,
containing the shells), the forward engine room (providing power
for the outer propellers), forward upper mess deck, the superstructure
and some other forward areas in the hull.
The upper left photo shows a view of the shell hoists in the forward
magazine ('A' magazine). Shells went from here to 'A' turret. Below
this magazine is the cordite magazine, which is not open to the
public.
Below this photo are the controls for flooding 'B' magazine, located
in 'A' magazine to the left of the door to 'B' magazine. The large
wheel is for activating sprinklers, whilst the smaller wheel is
for rapid flooding.
The navigating bridge of the HMS Belfast is shown in the bottom
left photograph.
The top right photo shows a view of some of the instruments within
the turret.
Below this is a view of the breech of a six inch gun within a
turret.
Below that is a view of the engine room. The wheel closest the
camera controls power astern, the middle wheel controls power ahead,
and the far wheel controls power to the cruising turbine.
On the far wall can be seen the engine telegraph.
The bottom right photograph shows a close up of a similar telegraph.
|
|
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|
Ship
|
Builder
|
Laid
Down
|
Launched
|
Completed
|
Left
Service
|
Fate
|
|
Southampton
Class
|
|
HMS Birmingham
|
Devonport Dockyard
(Plymouth)
|
Jul-1935
|
Sep-1936
|
Nov-1937
|
Sep-1960
|
Scrapped
|
|
HMS Glasgow
|
Scotts (Greenock)
|
Apr-1935
|
Jun-1936
|
Sep-1937
|
Jul-1958
|
Scrapped
|
|
HMS Newcastle
|
Vickers-Armstrong
(Tyne)
|
Oct-1934
|
Jan-1936
|
Mar-1937
|
Aug-1959
|
Scrapped
|
|
HMS
Sheffield
|
Vickers-Armstrong
(Tyne)
|
Jan-1935
|
Jul-1936
|
Aug-1937
|
Sep-1967
|
Scrapped
|
|
HMS Southampton
|
John Brown (Clydebank)
|
Nov-1934
|
Mar-1936
|
Mar-1937
|
Jan-1941
|
Heavily damaged
by aircraft from II/StG2. Deliberately sunk by torpedoes from HMS
Gloucester and HMS Orion (154nm ESE of Malta in the Mediterranean)
|
|
Liverpool
Class
|
|
HMS Manchester
|
Hawthorn Leslie
(Hebburn)
|
Mar-1936
|
Apr-1937
|
Aug-1938
|
Aug-1942
|
Heavily damaged
by Italian torpedo boat (either Ms16 or Ms22). Scuttled
(4nm E of Kelibia, in the Mediterranean)
|
|
HMS
Gloucester
|
Devonport
Dockyard (Plymouth)
|
Sep-1936
|
Oct-1937
|
Jan-1939
|
May-1941
|
Sunk
by aircraft from StG2, I/LG1 and II/LG1 (10nm W of Antikithera Island,
in the Mediterranean)
|
|
HMS Liverpool
|
Fairfield (Govan)
|
Feb-1936
|
Mar-1937
|
Nov-1938
|
Jul-1958
|
Scrapped
|
|
Edinburgh
Class
|
|
HMS Belfast
|
Harland &
Wolff (Belfast)
|
Dec-1936
|
Mar-1938
|
Aug-1939
|
Aug-63
|
Museum ship,
moored in the Thames in London
|
|
HMS Edinburgh
|
Swan Hunter
(Wallsend)
|
Dec-1936
|
Mar-1938
|
Jul-1939
|
May 1942
|
Torpedoed first
by submarine U456 then by destroyer Z24. Deliberately
sunk by a torpedo from HMS Foresight (120nm ENE of North
Cape, Norway).
|
[
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|
Appendix
C: Further Reading and Bibliography
|
Lenton H.T, British and Commonwealth
Warships of the Second World War, Greenhill Books, ISBN 1853672777
Whitley M. J, Cruisers
of World War Two, Naval Institute Press, ISBN 1557501416
‘Washington Treaty’,
Conference On The Limitation Of Armament, Washington, 6 February 1922
‘London Treaty’,
International Treaty For The Limitation And Reduction Of Naval Armament,
London, 5 June 1930
Roskill S.W, The
War At Sea, 1939-1945, HM Stationary Office
Jones J.M, Historic
Warships, McFarland & Company, ISBN 0899507794
Jane’s Fighting
Ships of World War II, Crescent Books, ISBN 0517679639
Piekalkiewicz J (translated
Spurgeon P) , Sea War 1939-1945, Historical Times, ISBN
091867817X
Mondey D, British
Aircraft Of World War II, Chancellor Press, ISBN1851526684
Chant C, "Aircraft
of World War II", Dempsey Parr, ISBN 1840843292
[
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Arthur M, The Navy 1939 To The
Present Day, Coronet Books, ISBN 0340684704
(Pages 61-64 HMS Liverpool in the Mediterranean; Page 78 the sinking
of HMS Gloucester; Pages 126-130 the sinking of HMS Edinburgh;
Pages 139 to 150 HMS Manchester in Operation Pedestal; Pages 325
– 328 HMS Birmingham in the Korean war; various pages other minor
mentions of Town class cruisers )
[
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Andrew Arthur, Royal
Navy Encyclopaedia, (viewed May 2000)
http://www.royal-navy.org.uk/
Naval
History On-Line, (viewed May 2000)
http://www.uq.net.au/~zzddelli/navyhome.htm
Warships1,
(viewed May 2000)
http://www.warships1.com
The Trustees of the
Imperial War Museum, HMS Belfast,
(viewed May 2000)
http://www.hmsbelfast.org.uk
[
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|
Appendix
D: Glossary of Terms
|
| Term |
Explanation |
|
AA
|
Anti-aircraft
|
|
Abaft
|
‘Aft
of’.
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Aft
|
The
part of the ship that is towards the stern (behind) from the point
of reference (eg ‘aft of the crane’), or the rear portion of the
ship.
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Aircraft
carrier
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"Any
surface vessel of war, whatever its displacement, designed for the
specific and exclusive purpose of carrying aircraft and so constructed
that aircraft can be launched therefrom and landed thereon. The
fitting of a landing-on or flying-off platform or deck on a capital
ship, cruiser or destroyer, provided such vessel was not designed
or adapted exclusively as an aircraft carrier, shall not cause any
vessel so fitted to be charged against or classified in the category
of aircraft carriers." – (London Treaty, 1930)
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Asdic
|
Original
British name for sonar (Sound Navigation and Ranging). A device
that sends out an underwater sound pulse to detect objects (submarines).
If the sound pulse strikes an object it is reflected back, and by
knowing the time taken for the round-trip the distance of the object
can be estimated. The direction of the sound pulse is controlled
by the operator, with reflections this giving a distance and bearing
for the object. The name comes from the Allied Submarine Detection
Investigation Committee, which investigated the system in 1917.
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Barbette
|
The
cylinder that the a main gun turret sits on. It supports the turret
and contains the ammunition hoists.
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Beam
|
The
maximum width of the ship.
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Block
coefficient
|
Cb
= V/(L x B x T), where V is the total underwater volume of the ship,
L is the waterline length of the ship, B is the breadth of the ship
and T is the draft of the ship. The block coefficient gives a crude
indication of the underwater shape of the ship, with low values
implying that the ship is shaped for speed at the expense of useable
space, and high values implying a slow vessel concerned more for
maximising useable internal space than for speed (note - this is
a rule-of-thumb). A block coefficient of 1 would indicate that the
ship was a rectangle, without any underwater shape. Modern supertankers
have block coefficients above 0.9 and container ships (fast merchant
ships) are around 0.65.
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Bow
|
The
most forward part of the ship that meets the water
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Bulkhead
|
An
internal subdivision of a ship. Bulkheads are not necessarily watertight.
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Bunker
|
A
fuel tank. When ships ran on coal this referred to the coal bunkers,
however nowadays this term also refers to fuel oil storage.
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Bunkering
|
Refuelling.
See Bunker.
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Capital
ship
|
Surface
vessels of war, the standard displacement of which exceeds 10,000
tons, or with a gun above eight inch (203 mm) calibre.
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|
Cb
|
Block
coefficient
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Cruiser
|
"Surface
vessels of war, other than capital ships or aircraft carriers, the
standard displacement of which exceeds 1,850 tons (1,880 metric
tons), or with a gun above 5.1 inch (130 mm) calibre." – (London
Naval Treaty, 1930)
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Cruiser
- heavy
|
A
cruiser with a gun above six inches in calibre. (London Naval Treaty,
1930)
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Cruiser
- light
|
A
cruiser with all guns of calibre six inches or less. (London Naval
Treaty, 1930)
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Deadweight
|
The
weight of all cargo and stores (including fuel, water, food and
other supplies) carried by a ship. For a cargo ship it is one of
the primary measures of ship size (along with gross tons), as it
approximates to the cargo carrying capacity of the ship.
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Depth
|
The
depth of a ship is the vertical distance between the deck and the
keel
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Destroyer
|
Surface
vessels of war the standard displacement of which does not exceed
1,850 tons (1,880 metric tons), and with a gun not above 5.1 inch
(130 mm) calibre. (London Naval Treaty, 1930)
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Displacement
|
The
weight of the ship. The term ‘displacement’ comes from Archimedes
principle, which states that the upthrust on a vessel is equal to
the mass of the volume of water displaced, and that a ship will
sink until the mass of displaced water equals the weight of the
ship. A ship’s displacement varies continuously - as stores are
consumed, ammunition fired and fuel burned the displacement decreases;
as modifications are added and supplies brought on board the displacement
increases. It is thus not possible to get a definitive value of
the total displacement of a ship, and different sources for displacement
often quote different values.
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Draft
|
The
vertical distance from the waterline to the lowest point on the
ship.
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Gross
Tons
|
A
measure of the internal volume of the ship, expressed as 100 feet3
to 1 ton. The volume includes all enclosed spaces, including bridge
and accommodation. Along with deadweight, this is one of the primary
means of measuring the size of a merchant ship. Gross tons was extensively
used as a measure in the past, however for modern cargo ships deadweight
is now the most common measure.
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HA
DCT
|
High
angle direction control tower. Used for engaging air targets.
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HF/DF
|
High
frequency direction finding equipment, used to get a bearing on
submarine radio emissions.
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Huff-Duff
|
Common
name for HF/DF equipment
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Keel
|
The
outside of the bottom of the ship
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Knot
|
One
nautical mile per hour, or 0.5144 meters per second.
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LA
DCT
|
Low
angle direction control tower. Used for engaging surface targets.
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Length
(OA)
|
The
overall length of the ship, from the aft-most part to the forward-most
part.
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Length
(pp)
|
The
length between perpendiculars. The forward perpendicular is defined
as the point where the forward-most part of the ship meets the water
at the fully loaded draft. The aft perpendicular often defined as
the centre of the rudder stock.
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Length
(WL)
|
The
length of the ship from the point where the aft end meets the water
until the point where the forward end meets the water.
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Nautical
mile
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1,852
metres
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Port
|
When
facing forward, the port side is the left side of the ship.
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SHP
|
Shaft
Horse Power - power delivered to the propeller shaft.
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Starboard
|
When
facing forward, the starboard side is the right side of the ship.
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Stern
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The
back end of the ship.
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Turrets
|
Turrets
contained the main weapons, and were identified in the Southampton
class as follows: front turrets were ‘A’ for the most forward, then
‘B’; aft turrets were ‘Y’ for the most aft, then ‘X’.
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