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EMERALD composite screw corvettes (6, 1876 - 1878)


Emerald 1878


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, t2120
Displacement full, t 
Length, m

67.1 pp

Breadth, m


Draught, m


No of shafts

Garnet: 1 (feathering screw)

others: 1 (hoisting screw)


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)

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



Standard scale images

<i>Emerald </i>1878
Emerald 1878


<i>Emerald</i> 1878
Emerald 1878

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.


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.