 They were designed as much to row as to sail, and carried their primary armament firing forward - a pair of long 18-pounders or 24-pounders, weapons which in any practical sense could only be trained and fired with the vessel under oars.The 1797 batch introduced means to improve their sailing ability.Each was fitted with a Schank drop keel, and lighter bow chasers replaced the heavy pair of guns firing forward over the bows; in later vessels one of the bow chasers would be moved aft to become a stern chaser, both of these guns then being mounted on the centreline and able to pivot.