The eighth HMS Shannon was the first British armoured cruiser. She was the last Royal Navy ironclad to be built which had a propeller that could be hoisted out of the water to reduce drag when she was under sail, and the first to have an armoured deck.
Design
thumb|left|Plan and section of HMS Shannon from Harpers Monthly Magazine, February 1886.
Shannon was built in response to two threats. The instructions of the British Admiralty to the designer, Nathaniel Barnaby, were to design an ironclad "capable of competing with the second class Ironclads of foreign navies". This meant in particular the ten French armoured corvettes of the and classes, though the ironclads of the smaller navies of Asia, and the Americas also featured. The British counter to these ships were the and classes of second-class ironclad of the 1860s. Shannons design was in the lineage of these ships, though the tactical landscape was changing. At the same time as Shannon was being planned, the Imperial Russian Navy launched the first armoured cruisers, and her sister . These ships were intended for the traditional cruiser mission of commerce raiding, but were armoured and armed on the same scale as a second-class ironclad. The existence of these ships meant that Shannon was now expected to act as a counter to them, and perform the commerce protection missions which had previously been the preserve of unarmoured cruisers, most recently the . She was also equipped with an unusual detachable ram, which was meant to be removed in peacetime to reduce the risk of accidentally ramming another warship. The ram was supposed to be stowed on board and attached in wartime; however this proved to be a very impractical arrangement.
Shannon was armoured in an unconventional manner. An armoured belt tall and between thick ran for most of the length of the ship, but stopped from the bow. Above the belt was an armoured deck thick, the first such armoured deck on a British warship. At the point the belt ended, a 9 in armoured bulkhead ran across the ship, the top of which formed the embrasures for the 10-inch guns on the upper deck. From the bottom of this bulkhead, a thick armoured deck extended to the bow, at a level below the waterline. The space above this forward armoured deck was filled with coal bunkers and stores to limit any flooding.
Shannon could use both sail or steam power. While steam was much preferred for combat, sail propulsion was considered vital for a ship intended to operate worldwide. She was given a lifting screw in order to increase her efficiency under sail, the last Royal Navy warship to be so equipped. She had three masts, and was initially given a ship rig with of sail, a point insisted on by the Director of Naval Operations, Captain Hood. In service, this was reduced to a barque rig with . She was equipped with Laird two-cylinder compound engines, the high-pressure cylinders being in diameter and the low-pressure cylinders . Steam came from eight cylindrical boilers at pressure. Her design top speed was , but her best actual speed was . To reduce fouling, she had zinc and wood sheathing on her hull.
Service
Shannon was something of a failure as a warship. While she accomplished more than Swiftsure or Audacious on a more limited displacement, and was the equal of a foreign 'station ironclad', she turned out to be far too slow to be an effective cruiser. While her heavy reliance on sailing efficiency was inevitable given her role, this was incompatible with the speed required to catch a foreign cruiser.
In May 1883 she briefly became a tender to and then was relegated to being a coastguard ship. During the Panjdeh Incident in 1885 she was briefly readied for operations. From May 1895 she was in reserve, and she was sold for breaking up in December 1899 for £10,105.
Building Programme
The following table gives the purchase cost of the members of the Shannon. Standard British practice at that time was for these costs to exclude armament and stores. In the table:
- Machinery meant "propelling machinery".
- Hull included "hydraulic machinery, gun mountings, etc."
{| class="wikitable" style="text-align:center"
|+Cost data
|-valign="middle"
! align = center colspan= 3| (BNA 1895)
|-valign="middle"
!align="center"| Hull
!align="center"| Machinery
!align="center"| Total<br><small>excluding<br>armament</small>
|-valign="middle"
|align= right | £233,902
|align= right | £53,367
|align= right | £287,269
|align= right | £302,707
|-
|}
Notes
References
- John Beeler, Birth of the Battleship – British capital ship design 1870–1881, Chatham Publishing, 2001
- Brassey, T.A. (ed) The Naval Annual 1895
- David Lyon, The Ship – Steam, steel and torpedoes, National Maritime Museum, 1980,
- Sondhaus, Lawrence Naval Warfare 1816–1914. Routledge, London, 2001.