Arab-class gunvessel
The "Arab"-class gunvessels were a pair of composite gunboats built for the Royal Navy in the mid-1870s. Design and construction. Designed by Nathaniel Barnaby, the Royal Navy's Chief Constructor, both ships was ordered from the Govan yard of Robert Napier and Sons in 1873 and laid down the same year as yard numbers 333 and 334. They were launched within days of each other in October 1874. The hull was built of iron frames and ribs, and planked in wood. This "composite" construction was both cheap and easy to repair and allowed the wooden planking to  be coppered, reducing marine growth. On far-flung colonial stations, the benefits of both simple repair and reduced marine growth were particularly positive, due to a lack of substantial ship repair and careening facilities. For this reason, smaller vessels like the "Arab" class continued to use composite construction until long after larger vessels had transitioned to iron or steel construction. Propulsion. Steam was provided at by 3 boilers to a single 2-cylinder horizontal compound-expansion steam engine generating a designed . In the event, "Arab" produced 656 ihp on trials, and "Lily" produced 829 ihp. A single screw was provided , which could be hoisted clear of the water to improve the ship's hull lines when sailing. A sailing rig was provided, with square rig on the fore and main masts, and fore-and-aft rigging only on the mizzen, giving her a "barque" rig. Armament. A single 7-inch rifled muzzle-loading gun amidships and two 6.3-inch 64-pounder rifled muzzle-loading guns, one forward and one aft, and both fitted on traversing slides, constituted the main armament. Two machine guns and a light gun were also fitted. "Arab" (but not her sister ship) was re-armed in  about 1879, with the after 6.3-inch 64-pounder gun replaced by three 20-pounder breech-loading guns under a newly constructed poop deck.