Jacob Swart published in his naval annual for 1846 a note dealing with the French navy, apparently original published in the Annales Maritime no. 4 of 1846. According this note official accounts were used to compile a list of 23 French ships which were still on stocks despite the building begin years earlier.
On stocks
1 in 1807
1 in 1811
1 in 1823
2 in 1824
2 in 1827
1 in 1829
3 in 1832
2 in 1833
1 in 1834
2 in 1835
1 in 1837
In fact one ship was in 1846 after 39 years still on stocks, while the ‘youngest’ just 9 years! Average life of a French ship of the line was in that period 18 years and 7 months. In a forthcoming article I shall attend more attention which to these ship.(1)
Source
Jhr. G.A. Tindal and Jacob Swart. Verhandelingen en Berigten betrekkelijk het Zeewezen en de Zeevaartkunde. Amsterdam , 1846, vol 6, 2nd part, p. 829. Digitized by Google.
Note
1. See for instance “The French ship of the line Montebello (1810) visited in 1838 while being prepared at the navy yard at Toulon ”.