Why this assumption ?delcyros wrote:if we assume a 10% quality advantage for british CA against KC/n.A
Yes, but Dunkerque had 15cm thick roofs for the main turrets, and Hood was firing from 15-16km distance.but DUNKERQUE´s case is unique as they employed face hardened armour on the flat turret roofs
Expected angle of fall of British 15"/L42 at 16km is about 17*.
The problem was that Dunkerque's turret top had an angled surface, at about 9* from the horizontal.
Thus theoretical impact obliquity may have been ~ 26* at best [17* angle of fall + 9* plate inclination]. However, real life obliquity would have been worse, as the turret would not have been oriented exactly towards Hood [thus adding a lateral obliquity].
Expected penetration of 15"/L42 at 26* would be ~ 100mm homogenous.
French cemented armor was based on Krupp WW1 cemented armor, which featured about 30-35% cimentite at the front, gradualy falling back in hardness and brittleness towards the back of the plate.
Another big question remains about the quality of French cemented armor, but lacking definitive documents, I don't know what to say.
Anyway, 15cm of armor (even cemented) broken up at 16km distance is quite an accomplishment