Duncan class (1859)

HMS Duncan, Halifax, Nova Scotia c. 1865
Class overview
Name:	Duncan class
Operators:	Royal Navy
Preceded by:	Conqueror class
Succeeded by:	Bulwark class
Cost:	Duncan: £132,697, Gibraltar: £130,235
Built:	1855–1861
In service:	1863–1870
Building:	3
Planned:	3
Completed:	2 as Duncan class 1 completed as Bulwark class
Active:	2
Retired:	2
General characteristics
Class and type:	Duncan class
Type:	101-gun screw two-decker
Tonnage:	3,715 t
Displacement:	5,950 t
Length:	252 ft 0 in (76.81 m) overall 213 ft 9.25 in (65.1574 m) keel-line
Beam:	58 ft 0 in (17.68 m) extreme
Draught:	Gibraltar (not masted or stores) 18 ft 0 in (5.49 m) forward, 22 ft 6 in (6.86 m) aft
Depth of hold:	25 ft 6 in (7.77 m)
Installed power:	Duncan (Penn) 3428 ihp Gibraltar (Maudslay) 3494 ihp
Propulsion:	800 nhp
Sail plan:	Main mast: 67 ft 0 in (20.42 m)ft × 0 ft 40 in (1.02 m) Fore mast: 61 ft 0 in (18.59 m)ft × 0 ft 37 in (0.94 m) Mizzen mast: 51 ft 6 in (15.70 m)ft × 0 ft 27 in (0.69 m)
Speed:	Duncan 13.338 knots (24.702 km/h) trials Stokes Bay 7 August 1860 Gibraltar 12.48 knots (23.11 km/h) (not masted or stored) trials Plymouth 17 April 1861
Complement:	930
Armament:	Gun Deck: 36 × 8in/65cwt Main deck: 36 × 32-pounder/56cwt Upper Deck: 28 × 32-pounder/42cwt, 1 × 68-pounder 95 cwt
Notes:	Source: Lambert Battleships in Transition

The Duncan class of 101-gun two-decker steam line-of-battle ships are considered by Professor Andrew Lambert to have been the "final statement of the British design progress" for steam two-deckers. The class consisted of HMS Duncan and HMS Gibraltar. The Bulwark class had identical hulls. HMS Gibraltar was the last wooden steam line-of-battleship to commission as a private ship in the Royal Navy.

The first British steam 101-gun two-decker was the St Jean d'Acre, which was ordered and laid down in 1851 and was "the first ship that can be directly attributed to Sir Baldwin Walker's influence. [She was] an expansion of the Agamemnon [91-guns], her superior qualities were developed in the succeeding Conqueror and Duncan classes of 101-gun ships." The Duncan class were longer and broader versions of the Conqueror, which was a success as they were noticeably faster (see table below).

"The early steam battleships, such as the 230-foot (70 m) Agamemnon, combined a measure of speed under sail or steam with similar manoeuvring powers to the sailing ships. This persuaded Walker to try even longer hulls, the Renown being drawn out to 244 feet 9 inches (74.60 m) and the Bulwark to 252 feet (77 m). While the post-war ships, from their greater length and finer lines, reached higher speeds they did so at the expense of the facility and precision of their response to the helm. New ships such as the Donegal, 101 and Renown, 91 were considered slow in their stays. This lack of handiness was emphasised by their operating in company with older ships such the St Jean d'Acre, 101 and James Watt, 91 which lacked speed, but tacked and wore far more easily. Lord Aukland had anticipated this problem in 1847."