spicmart wrote:With Bismarck's turrets having really so little armor compared they must have been way more easily knocked out? That must have been a serious disadvantage if one looks at the armor of other BBs' turrets.
Bismarck's turret face plates were 14.2-inches thick. This does not compare badly with European practice. For example, KGV's face plates were 12.75-inches (not counting the backing plate which is not significant to the effective thickness). Vanguard’s were 13-inches. Littorio’s were 14-inches.
Richelieu’s were thicker at 17-inches, but there were only two turrets, and Germans engineers reported that the quality of the French plates were of deplorable quality, so more was needed.
Which reminds me that with thick armour plates, increasing thickness does not provide a linear increase in protective quality. Beyond about 12.75-inches each incremental increase in thickness provides less and less improvement in protection. A 17 -inch plate does not provide 3-inches more protection than a 14-inch plate of the same armour.
Looking at the Bismarck’s turrets starting from the top, the roof plates were 130mm and this is the amount required in keeping with an outer immunity zone of 30,000 meters.
But as Iranon commented, there were trade-offs to consider when it came to protecting turrets rather than just providing an theoretical immunity zone against a particular gun from one range point to another. For example, the infamous angled facets of 180mm homogeneous armour represent a trade- off. They were angled-back 65 degrees from the normal. They did not provide protection from beyond 23,000 meters battle range to plunging fire, where they were unlikely to take such a hit, but they traded that off for better protection, because of the presented obliquity, at ranges of less than 20,000 meters, where they were more likely get hit. This additional short range protection was particularly needed should they find themselves embroiled in battle with light forces slinging smaller caliber higher velocity ordinance.
Likewise, the various angles of the heavy face plates we find on various designs probably has to do with trade-offs, such as improving the chances of breaking up or deflecting high velocity ordinance at ranges that really can't be protected against partial or complete perforation anyway.