As the name implies, coasters were designed to sail in the shallower waters near a coast. They were relatively slow and not particularly safe for deep sea voyages, but could carry a respectable amount of cargo with fewer crew than most cargo ships. Typically 60 ft (18 m) long at the keel and 20 ft (6 m) wide, coasters had two masts with triangular sails and no oars. The rudder was mounted off one side, and above deck there was often only a small sterncastle. Crew size ranged from a minimum of 12 to a maximum of 40, including passengers. A coaster could be armed with a large weapon (such as catapult or ballista) but was not built to wield a ram.