Saltheart wrote:Thanks for that. I wonder how much that 18 inch Class B plate would have been worth in protection when "converted" to Krupp cemented. Maybe 15 inches?
The limit velocities in NRL studies were about 20% lower than they should have been.
Converting the protective qualities of homogenous armour to cemented armour is complicated because of the interaction of capped and un capped shell with the different types of armour at different striking angles. The more acute the striking angle is away from the normal (right angle), the better homogenous armour performs. This is why homogenous armour is used for deck armour because the striking angle is usually going to be at least 60* from the normal. On the other hand where the striking angle is less than about 50* from the normal; face hardened or cemented armour is used, because it works better at those striking angles.
The severely laid-back frontal plates on some turret designs work better with homogenous armour against flat trajectories but it becomes less useful as the battle range increases because eventually the increased angle of fall will put the striking angle right on the normal should it strike the angled plate. The 45* angle used by the modern American battleships is not at all ideal for using homogenous armour against either flat trajectory or longer range fire, but it was originally intended to use cemented armour.
Only the French used cemented armour on turret roofs, because they thought the greater danger was bombs- which strike at or near the normal. This explains how a Hood 15" shell perforated a turret roof at only about 15,000 yards against Dunkerque.
The French put thick armour on their turret faces which were laid back 17*. Richelieu had 17" face hardened armour (what was the comparitive quality and did they succeed in fabricating such thick face hardened plates of acceptable quality?). With only two turrets such heavy protection was called for.
However, I have always found it interesting to read on the internet how egg shell fragile the German turrets were with 14.2" KC faces, and the 7.2" Wh severely angled facet, and the 5.2" Wh roof.
Looking at some some other face thickness: