The Woolwich-built corvette was launched on 5 February 1858. For the expedition it displaced roughly 2,171 tons, measured about 68.6 metres overall, drew about 5.28 metres forward and 5.74 metres aft, and had a hold depth of roughly 7.29 metres. A two-cylinder trunk engine supplied about 1,450 indicated horsepower to one screw, while the retained sailing rig offered another means of propulsion; its spars were reduced for the voyage. Its normal armament comprised twenty 8-inch muzzle-loading smoothbores, ten per side, with a pivot-mounted 10-inch or 68-pounder at the bow. Most of those guns were removed to make room for the scientific programme. Challenger retained two guns because a valuable research vessel on a global route still needed some deterrence against opportunistic attack.
Notable Point · 16:01-20:22
HMS Challenger's size, propulsion, and reduced armament
HMS Challenger combined steam, sail, scientific fittings, and two retained guns after most of its normal armament was removed.