Bulwark - class battleship ( 1859 ) The " Bulwark " class were the final class of wooden line - of - battle ships laid down for the Royal Navy . They were laid down after . In March 1861 their construction was suspended , and seven were later converted to iron - clads . and were kept on the stocks almost complete , in case of need , until they were scrapped in 1873 and 1872 . Origins . The consensus of British naval opinion after the Crimean War favoured the large steam - powered two - decker line - of - battle ship with 101 or 91 guns . The designs for two - decker evolved . " The 101 - gun type were redesigned with an extra 400 tons and engines of 800 nhp , to produce the " Duncan " class . The 91s were given similar engines , while their smaller increase in size was largely taken up with an additional overall for a finer length - to - beam ratio and improved lines in . In the 1859 programme the two types were merged to produce a 91 - gun ship with the dimensions of the 101 - gun type . Two ships built on this plan - the " Bulwark " and " Robust " , the latter having been commenced as a 101 - gun ship - were preserved on the stocks until 1872 , the remaining seven being converted into ironclads . These last two - deckers were overall , that they all displayed all the classic symptoms of weak construction , such as leaky seams , demonstrated that wood was no longer suitable for the construction of the largest classes of warships . Britain ' s first sea - going iron - clad , was laid down in May 1859 , and a further three had been laid down by the end of 1859 . Nevertheless , the Royal Navy continued to convert old sailing line - of - battle ships to steam , and to order and lay down new " Bulwark " - class two - deckers . The objective was to achieve parity with the combined navies of France and Russia . Initially there was great uncertainty about the value of iron - clads . So it was prudent to continue building unarmoured steam line - of - battle ships , which would in any case be " the common currency of sea - power for some years to come . " In March 1861 , work on the " Bulwark " class was suspended . They were retained on the stocks while the smaller was launched on 27 March 1861 . The larger ships were better suited for conversion into iron - clads and were held in reserve for that purpose . Similarly , the sailing line - of - battle ships and completed their conversion to steam line - of - battle ships on 21 May and 25 June 1861 respectively . Design . The " Bulwark " class ships were a modification of the 101 - gun " Duncan " - class design . They had the same dimensions , but had a new timbering plan dated 29 July 1858 , which suited the smaller armament . The reduction in armament was intended to improve the efficiency of the guns . Key Dates . The following table shows key dates for the " Bulwark " class . Conversion to iron - clads . " Bulwark " and " Robust " were suspended on the stocks in March 1861 in an advanced state of construction . The Controller " had plans prepared for the " Bulwark " to be converted into a twin turret breastwork monitor but they were never used . As Edward Reed pointed out this was a wise policy as they would have been inferior to , and yet more costly than , iron - hulled ships built from scratch . " In war time the rapidity with which these ships might be converted into iron - clads would probably outweigh these considerations " . " Bulwark " and " Robust " were eventually broken up in March 1873 and August 1872 respectively . The remaining seven ships of the " Bulwark " class were in a less complete state and were converted into ' ironclad frigates ' . Of these HMS " Triumph " ( later renamed ) , , and were converted to ' broadside ironclads ' with 1000 nhp engines . had a similar conversion but with the original 800 nhp engine . The development of these four ships is discussed in the article on the . , and were later converted into ' central battery ships ' .