Recently I bought a copy of French Battleships of World War One by Jordan and Caresse. Published in 2017 at £40 the demand for it on the second-hand market is evidently high. I got the cheapest available at £80; US prices seem to be even higher, even over $200. It is a good book covering in detail many classes of ship.
It is armor that I want to mention here. According to Jordan the armor material for the belts used from the start up to the Bretagne class went through the following sequence: wrought iron, compound armor, mild steel, nickel steel and Harvey cemented. The improving quality led to reductions in maximum belt thickness from 55 cm (wrought iron), 45 cm (compound and mild steel), 40 cm (nickel steel) and 32 cm (Harvey). The first French battleship, completed in 1902, to have a belt of Harvey cemented armor was Iena. By that year various navies had moved on to Krupp cemented armor. In the last classes, including the Bretagne class, the maximum belt thickness was reduced further to 25 cm. Jordan does wonder if this reduced thickness was due to improvements made in the Harvey process. However, he also notes that it may have been due to the displacement limits on these ships, which were smaller than most of their contemporaries. It might have also been accounted for by increasing anticipated battle ranges: whereas in the 1890s typical battles ranges were around 2000 m but by the time of the Dreadnought classes ranges of up to 8000 m were anticipated. That last figure was on the low side, even the Germans anticipating ranges up to 10000 m.
But the point that surprised me was that apparently no change was made to Krupp cemented armor in this timeframe. According to Nathan Okun in his piece on armor and steel types on this website, Krupp armor was considerably more expensive than that of the Harvey type. And the financial constraints affecting French battleships were probably greater than on those of most other countries. Nathan Okun says (something I have not noticed before) that the general move from Harvey cemented armor to Krupp cemented was because KC could damage shells that did not shatter, increasing its resistance also in this case. The benefit of Harvey armor was limited to being able to shatter uncapped shells. For cemented armor types Nathan Okun assigned a factor QD (in addition to the normal quality factor Q) which was a measure of the ability of the armor to damage shells. For KC in general QD = Q but for Harvey cemented armor QD = 0.86Q and was therefore lower.
As to the steel type used in the armor decks in the 1890s the type used was called 'extra mild'. This may have been suitable at very high obliquities where most shells will richochet from the deck. But by the Patrie class, completing in 1907/08 a stronger steel type '50 kg' (nominal UTS 50 kg/mm^2) was used. This change may have been made because of greater battle distances with somewhat lower obliquities.
Jordan's book on French Battleships 1922-1956 describes, as far as I can see, belt, turret and barbette armor in the Dunkerque and Richelieu classes as being simply cemented armor, without saying what kind of cemented armor it was,
Neil Robertson
It is armor that I want to mention here. According to Jordan the armor material for the belts used from the start up to the Bretagne class went through the following sequence: wrought iron, compound armor, mild steel, nickel steel and Harvey cemented. The improving quality led to reductions in maximum belt thickness from 55 cm (wrought iron), 45 cm (compound and mild steel), 40 cm (nickel steel) and 32 cm (Harvey). The first French battleship, completed in 1902, to have a belt of Harvey cemented armor was Iena. By that year various navies had moved on to Krupp cemented armor. In the last classes, including the Bretagne class, the maximum belt thickness was reduced further to 25 cm. Jordan does wonder if this reduced thickness was due to improvements made in the Harvey process. However, he also notes that it may have been due to the displacement limits on these ships, which were smaller than most of their contemporaries. It might have also been accounted for by increasing anticipated battle ranges: whereas in the 1890s typical battles ranges were around 2000 m but by the time of the Dreadnought classes ranges of up to 8000 m were anticipated. That last figure was on the low side, even the Germans anticipating ranges up to 10000 m.
But the point that surprised me was that apparently no change was made to Krupp cemented armor in this timeframe. According to Nathan Okun in his piece on armor and steel types on this website, Krupp armor was considerably more expensive than that of the Harvey type. And the financial constraints affecting French battleships were probably greater than on those of most other countries. Nathan Okun says (something I have not noticed before) that the general move from Harvey cemented armor to Krupp cemented was because KC could damage shells that did not shatter, increasing its resistance also in this case. The benefit of Harvey armor was limited to being able to shatter uncapped shells. For cemented armor types Nathan Okun assigned a factor QD (in addition to the normal quality factor Q) which was a measure of the ability of the armor to damage shells. For KC in general QD = Q but for Harvey cemented armor QD = 0.86Q and was therefore lower.
As to the steel type used in the armor decks in the 1890s the type used was called 'extra mild'. This may have been suitable at very high obliquities where most shells will richochet from the deck. But by the Patrie class, completing in 1907/08 a stronger steel type '50 kg' (nominal UTS 50 kg/mm^2) was used. This change may have been made because of greater battle distances with somewhat lower obliquities.
Jordan's book on French Battleships 1922-1956 describes, as far as I can see, belt, turret and barbette armor in the Dunkerque and Richelieu classes as being simply cemented armor, without saying what kind of cemented armor it was,
Neil Robertson
statistics: Posted by neilrobertson1 — 1:27 PM - 1 day ago — Replies 3 — Views 172