NAVYPEDIA

Photo

Emerald 1878

Ships

Name	No	Yard No	Builder	Laid down	Launched	Comp	Fate
Opal (ex-Magicienne)		63	Doxford, Sunderland	13.10.1873	9.3.1875	1.1876	sold 8.1892
Tourmaline		113	Raylton Dixon, Middlesborough	17.7.1874	30.10.1875	25.10.1876	coal hulk 1899
Turquoise		203	Earle, Hull	8.7.1874	22.4.1876	13.9.1877	sold to BU 9.1892
Ruby		202	Earle, Hull	8.7.1874	9.8.1876	14.6.1877	coal hulk 12.1904
Emerald		190	Pembroke DYd	29.7.1874	18.8.1876	2.7.1878	powder hulk 1898
Garnet			Chatham DYd	16.3.1875	30.6.1877	31.10.1878	sold 12.1904

Technical data

Displacement normal, t	2120
Displacement full, t
Length, m	67.1 pp
Breadth, m	12.2
Draught, m	5.48
No of shafts	Garnet: 1 (feathering screw) others: 1 (hoisting screw)
Machinery	sails + 1 2-cyl HCE, 6 cylindrical boilers
Power, h. p.	Opal: 2187 Turquoise: 1994 Ruby: 1833 Tourmaline: 1972 Emerald: 2170 Garnet: 2005
Max speed, kts	Opal: 12.5 Turquoise, Ruby: 12.3 Tourmaline: 12.6 Emerald: 13.9 Garnet: 13.2
Fuel, t	coal 260
Endurance, nm(kts)	2000 - 2280(10)
Armament	Opal: 12 x 1 - 160/16 64pdr 71cwt MLR, 2 x 1 - 160/16 64pdr 64cwt MLR others: 10 x 1 - 160/16 64pdr 71cwt MLR, 2 x 1 - 160/16 64pdr 64cwt MLR
Complement	232

Standard scale images

Graphics

Project history

Designed by Nathaniel Barnaby. The introduction of the steel-hulled despatch vessels Iris and Mercury, with a speed of 18kts, made all other materials for hull construction obsolete, so the period of composite construction was brief. Care had to be taken in the distribution and support of weights in wooden hulls, to avoid excessive hogging and sagging. In composite hulls, the additional longitudinal strength gave designers more freedom in hull lines and weight distribution The theory that a fine entry gave extra speed was influenced by the performance of tea clipper ships with their 'Aberdeen bow', ie extending the stem out to form a cutwater, drawing the waterlines finer at the bow, giving greater buoyancy forward and enabling the ship to divide the water easily. In practice, however, this theory did not work with the Emerald class. To compensate for buoyancy they were given a short but very full midships section. Receiving little help from the ends, they tended to behave like a see-saw in heavy weather. Their faulty underwater lines adversely effected their performance under sail, none exceeding much more than 12kts.     The frames and keels of this class were of wrought iron and the stem and stern post of cast iron. The cladding was a double layer of teak, the inner 89mm, the outer 76mm in thickness. The first layer of timber was secured direct to the frames, the second to the first with a waterproof coating between. Watertight bulkheads extended to the upper deck. The compound engines were far from satisfactory due to the Admiralty's decision to invite competitive tenders, resulting in price cutting and inferior workmanship. In fact, the engine in Tourmaline was so troublesome that her chief engineer suffered a nervous breakdown, committing suicide. The HCE engines were of two cylinders - one HP and one LP. The six cylindrical boilers worked at 4.2kgf/cm2.     All guns were slide-mounted, with a broadside fire of five a side and two chase guns firing through embrasures at both ends of the ship. As completed they were all ship-rigged, carrying 1700m2 of plain sail. The lower masts were of iron.

Opal was laid as Magicienne and renamed 12.2.1875.

Modernizations

1876, Opal: - 2 x 1 - 160/16

early 1880s, Emerald, Tourmaline: were rearmed with 4 x 1 - 152/26 BL Mk II, 8 x 1 - 127/25 BL Mk I/II/III/IV/V

early 1880s, Garnet: was rearmed with 14 x 1 - 127/25 BL Mk I/II/III/IV/V

1880s, all: were converted to barque rig; + (7 - 9) x 1 - 11.4/87

Naval service

No significant events.

Many thanks to Wolfgang Stöhr for additional information on this page.