These were the last Royal Navy gunboats to have wooden hulls: subsequent gunboats were of composite construction, with wooden planking over iron frames.

[1] The class were fitted with a single-cylinder single-expansion reciprocating steam engine.

The single screw could be hoisted to give improved performance under sail.

[1] The ships were provided with a three-masted barquentine rig, that is, with square sails on the foremast and fore-and-aft sails on the main and mizzen masts.

[1] Early ships of the class were armed with two 68-pounder smooth bore muzzle loading cannon (as had been planned, but not implemented, for the Dapper class); but the Heron was fitted with two 112-pounder Armstrong guns.