Boadicea Class Cruiser (1908)

The seven scout cruisers of the Boadicea Class were completed at Pembroke Royal Dockyard between 1910 and 1913.

Today, the class is often treated as three separate classes (two Boadiceas, two Blondes and three Actives) but contemporary documents almost always seem to discuss them collectively. There are, however some significant differences. Most notably, Boadicea and Bellona had just six 4-in guns, and the others carry eight or ten. The mountings also differ as indicated below.

Their designation as scout cruisers was taken literally, as Blanche, Blonde and Bellona served throughout the war providing a close-in screen to individual Battle Squadrons for fleet operations.

Overview of 7 vessels
Citations for this data available on individual ship pages
Name	Builder	Laid Down	Launched	Completed	Fate
Boadicea	Pembroke Royal Dockyard	1 Jun, 1907	14 May, 1908	Jun, 1909	Sold 13 Jul, 1926
Bellona	Pembroke Royal Dockyard	5 Jun, 1908	20 Mar, 1909	Feb, 1910	Sold 9 May, 1921
Blonde	Pembroke Royal Dockyard	6 Dec, 1909	22 Jul, 1910	May, 1911	Sold 6 May, 1920
Blanche	Pembroke Royal Dockyard	12 Apr, 1909	25 Nov, 1909	Nov, 1910	Sold 27 Jul, 1921
Active	Pembroke Royal Dockyard	27 Jul, 1910	14 Mar, 1911	Dec, 1911	Sold 21 Apr, 1920
Amphion	Pembroke Royal Dockyard	15 Mar, 1911	1911	Mar, 1913	Mined 6 Aug, 1914
Fearless	Pembroke Royal Dockyard	15 Nov, 1911	1912	Oct, 1913	Sold 8 Nov, 1921

Binoculars

In September 1914, the ships were allowed six additional pairs of Pattern 343 Service Binoculars.

Habitability

In 1912 and 1913, four Bastian Radiators were obtained for a temporary trial in warming the Officers' Cabins on the Upper Deck where radiators were not already present. Based on the satisfactory reports, these radiators were kept in place permanently.

Boats

The ships were ordered in July 1914 to surrender their 13.5 foot dinghy unless they'd already returned their Balsa Raft – they were not to carry both.

Rangefinders

In January 1914, it was reported that a rangefinder mounted on the fore upper bridge may have been unable to work properly when the ships were steaming at high speeds. Whether this was due to vibration or spray is not made clear. At the same time, it was worried that a rangefinder mounted aft had a forward arc of view obstructed by boats.

In 1918, it was proposed that the "Blonde class" should have their existing 4.5 foot rangefinder replaced by a 9-foot model. It is not clear if this applies to just the Blonde group ships or this entire class.

Armament

Boadicea

This section sourced from The Sight Manual, 1916 except as indicated.

• six 4-in B.L. Mark VII guns on P. IV mountings

The P. IV mountings could elevate to 15 degrees and depress to 10 degrees, but though its sight could match the 15 degree elevation, the range dial was only graduated to 8,500 yards (8.5 degrees) at 2,225 fps. This might have been in obeisance to the Admiralty's stated desire that giving a long-ranged gun to a light cruiser is a guarantee that it will go get in a gunfight and abandon its scouting duties.^{[Inference][Citation needed]}

The gear-worked sights, the first F.T.P. models to be introduced, had a range gearing contant of 42.95 and spiral-reading range dials for 2850 fps, 1-in aiming rifle and .303-in aiming rifle. M.V. could be corrected (downward only) 200 fps by adjustable scale plate.

The deflection gearing constant was 61.7 with 1 knot equal to 2.74 arc minutes, corresponding to 2824 fps at 3500 yards. Drift was corrected by inclining the sight 2 degrees.

The layer's sight line was 16.8 inches above the bore, and 15 inches left. The trainer's lines were 16.8 inches above and 14.9 inches right.

The sight lacked a "C" corrector. A number of temperature scale plates corresponding to M.V.s varying by 25 fps could be shipped with an index facing the actual M.V..

Open sights do not seem to be in the drawing.

In October 1913, it was decided that the mountings should also have buzzer for their firing circuits.

Bellona, Blonde and Blanche

This section sourced from The Sight Manual, 1916 except as noted.

• six (Bellona) or ten ((Blonde and Blanche) 4-in B.L. Mark VII guns on P. IV* mountings with F.T.P. sights.

These ships had the same mountings as some Bristol class cruisers.

The mounting could elevate 15 degrees and depress 10 degrees, but though its sight could match the 15 degree elevation, the range dial was only graduated to 11.5 degrees (10,000 yards).

These cam-worked F.T.P. sights had range dials for 2750 fps, and 1-in and .303-in aiming rifles. M.V. could be corrected by adjustable pointer through +/- 150 fps.

The deflection gearing constant was 64.277 with 1 knot equal to 2.41 arc minutes, corresponding to 2800 fps at 2000 yards. Drift was corrected by inclining the sight 2 degrees.

The layer's sight line was 13.73 inches above the bore, and 15.85 inches left. The trainer's sight line was 15.08 inches above and 14.9 inches right.

The sight had a temperature correcting scale plate and a "C" corrector.

The layer had an open sight. The trainer's sight could be used as a free sight with a counterweight.

In August of 1913, Portsmouth Royal Dockyard was to supply head rests for these guns, to be fitted in the dockyard when the opportunity arose. In October 1913, it was decided that the mountings should also have buzzer for their firing circuits.

Active and Amphion

This section sourced from The Sight Manual, 1916 except as noted.

• ten 4-in B.L. Mark VII guns on P. IV** mountings

The layer had a double-handed bicycle-type two-speed elevating crank. At high speed, it elevated the gun 2.97 degrees per rotation. At slow speed, it did 1.48 degrees. The right hand had a firing trigger right on the elevating handle, and the speed selection was made by throwing a separate lever using the left hand. The pedestal had a lever to clamp the gun in training.

The mounts could elevate 15 degrees and depress 10 degrees, but though the sights could match the 15 degree elevation, the range dials were only graduated to 11.5 degrees (10,000 yards).

These cam-worked sights had range dials for 2750 fps, and 1-in and .303-in aiming rifles. M.V. could be corrected by adjustable pointer through +/- 150 fps.

The deflection gearing constant was 64.277 with 1 knot equal to 2.41 arc minutes, corresponding to 2800 fps at 2000 yards. Drift was corrected by inclining the sight 2 degrees.

The layer's sight line was 13.73 inches above the bore, and 15.85 inches left. The trainer's sight line was 13.83 inches above and 14.9 inches right.

The sight had a temperature correcting scale plate and a "C" corrector.

These were likely F.T.P. sights, but there is no definite indication that they were.^[Inference]

The layer had an open sight. The trainer's sight could be used as a free sight with a counterweight.

In August of that 1913, Portsmouth Royal Dockyard was to supply head rests for the guns on Active and Amphion, to be fitted by the ships' artificers.

Fearless

This section is sourced from The Sight Manual, 1916.

• ten (possibly just eight when completed) 4-in B.L. Mark VII guns on P. VIII mountings with F.T.P. sights.

The mounts could elevate 15 degrees and depress 10 degrees, but though the sights could match the 15 degree elevation, the range dials were only graduated to 14 degrees (11,000 yards). It appears that no other ships carried this particular mount.

These cam-worked sights had range dials for 2750 fps, and 1-in and .303-in aiming rifles. M.V. could be corrected by adjustable pointer through +/- 150 fps.

The deflection gearing constant was 59.79 with 1 knot equal to 2.41 arc minutes, corresponding to 2750 fps at 2000 yards. Drift was corrected by inclining the sight bracket 2 degrees.

The layer's sight line was 12 inches above the bore, and 22.3 inches left. The trainer's sight line was 12 inches above and 18.25 inches right.

In addition to the M.V. corrector, the sight had a temperature correcting scale plate and a "C" corrector.

There was an open sight on both sides. No mention is made of a free sight.

Torpedoes

The two ships ordered in the 1908-09 Programme had smaller torpedoes.

Boadicea and Bellona:

• two 18-in torpedo tubes

Other vessels:

• two 21-in torpedo tubes.

Fire Control

Control Groups

Gun Control Groups

In 1909, these were described as being similar to the Gem class, but the forecastle and poop guns could be controlled as separate groups or attached to the nearest broadside group on either side. The middle line guns could be connected to whichever side was desired. However, the figure shown indicates that the guns were grouped with the first three on each broadside being in a forward group and the aftmost pair being the aft group for navyphone control with no similar provision being offered for data circuits.

Torpedo Control

In 1907, Boadicea, Swift and the River class destroyers were to be equipped with Fore Bridge Firing Gear. Later, it was decided that Bellona, Blanche and Blonde would not receive Fore Bridge Firing Gear.

Transmitting Stations

If we trust that they all resembled Fearless, they had a transmitting station forward.

Dreyer Table

These ships had no fire control tables.

Fire Control Instruments

Fire Control Circuits

Boadicea Group

By 1909, Boadicea (Mark I instruments) and Bellona (Mark II) were outfitted with Vickers F.T.P. Fire Control Instruments, marking a new wrinkle in equipment by replacing the Barr and Stroud equipment that had taken hold shortly after 1906. The equipment was fitted as follows:

• Range Transmitters: 3
• Deflection Transmitters: 3
• Range Receivers: 6
• Deflection Receivers: 6
• C.O.S.: 1
• Vickers Fire Gongs: 6 with 3 keys

Neither ship had Target Visible or Gun Ready signals.

Blonde Group

In 1909, it was planned that Blonde and Blanche were to be completed with the latest Vickers Mark II F.T.P. Fire Control Instruments as follows:

• Range Transmitters: 2
• Deflection Transmitters: 2
• Range Receivers: 10
• Deflection Receivers: 10
• C.O.S.: none
• Vickers Fire Gongs: 10 with 2 keys

Neither ship had Target Visible or Gun Ready signals.

Active Group

Fire Control Navyphones and Data Circuits

Fire Control Navyphones and Data Circuits

Control was by navyphone from either:

• Aft control platform
• Upper conning tower

The upper conning tower position may have been a fall-back, as its portable navyphones could also be plugged in at the T.S..

The navyphone control could split fire in fore and aft groups. The data system for each broadside had only a single set of transmitters and not C.O.S. in the T.S. and could not.

Each broadside had similar, separate systems along the following pattern. Each had a Pattern 872 firing key in the T.S. to actuate the Pattern 872 firing gongs at the guns, and range and deflection transmitters (with local Mark III repeats) to drive the receivers at the guns. There were no C.O.S. fitted to allow the splitting of these data connections into fore/aft groups as was provided for the navyphone system. Confusingly, the next plate in the same source indicates that the data systems did have a C.O.S. to permit fore-aft splitting, with four sets of transmission gear in the T.S..

Alterations

By November 1918, Boadicea, Bellona, Blonde and Blanche were fitted with rails for 66 mines. The torpedo tubes and guns removed when the mines were shipped could be placed back aboard with enough notice.

See Also

• Wikipedia articles on the Boadicea, Blonde and Active classes

Bibliography

• Admiralty, Gunnery Branch (1910). Handbook for Fire Control Instruments, 1909. Copy No. 173 is Ja 345a at Admiralty Library, Portsmouth, United Kingdom.

Boadicea Class Scout Cruiser

Boadicea Group

Boadicea

Bellona

Blonde Group

Blonde

Blanche

Active Group

Active

Amphion

Fearless

<–

Sentinel Class

Minor Cruisers (UK)

Bristol Class

–>