The batteries have a claim to the title of the first ironclad warships but they were capable of only 4 knots ( 7 km / h ) under their own power : they operated under their own power at the Battle of Kinburn , but had to be towed for long range transit . They were also arguably marginal to the work of the navy . The brief success of the floating ironclad batteries convinced France to begin work on armored warships for their battlefleet .