 Wooden hulls continued to be used for long @-@ range and smaller ironclads , because iron nevertheless had a significant disadvantage . Iron hulls suffered quick <unk> by marine life , slowing the ships down — <unk> for a European <unk> close to dry docks , but a difficulty for long @-@ range ships . The only solution was to sheath the iron hull first in wood and then in copper , a laborious and expensive process which made wooden construction remain attractive . Iron and wood were to some extent interchangeable : the Japanese <unk> and <unk> ordered in 1875 were sister @-@ ships , but one was built of iron and the other of composite construction . 
