Hi Alec,Alecsandros wrote: "....Littorio class armor deck differed from centerline to outboard of ship: above machinery, the centerline armor was equivalent to ~ 107mm single sheet homogenous armor; outboard, it was equivalent to 98mm single sheet....... Furthermore, above magazines, Littorio had an equivalent of ~ 157mm armor, but on the outboard of the ship, adjacent to the magazines, the thickness was the same 98mm as above machinery. While some armored bulkheads could be in the way of a perforating trajectory......."
you are right about the inboard/outboard difference, but the scheme was a bit more complex/efficient. Here below the complete scheme and description of Littorio's horizontal protection over the citadel:
source E.Bagnasco, "Class Littorio Battleships", pag.37(scheme) and 58 (description).
As you see, the horizontal protection was based basically on 2 armor grade steel ("OD = acciaio omogeneo" Nickel - Chrome) decks (with some HT ("ER = Acciao ad Elevata Resistenza") steel backing them and a third intermediate HT deck).
There was a weather deck ("Ponte di castello") of 36 mm Homogeneous + 9 mm HT steel (this was a de-capping deck), a middle deck ("Ponte di coperta") of 12 mm HT steel (I doubt this deck was improving protection, even marginally....) and a main deck ("Ponte di batteria") of 100 mm homogeneous + 12 HT steel over machinery (frame 83 to 130) inboard and 90 mm homogeneous + 12 mm HT steel outboard. Over magazines (frames 54 to 83 and 130 to 174) the main deck was 150 mm homogeneous + 12 mm HT inboard and 100 homogeneous + 12 mm HT steel outboard.
Even discounting at all the 33 mm HT steel...., Littorio's had a minimum armor grade horizontal protection over machinery of 136 mm homogeneous steel inboard and 126 mm homogeneous steel outboard, while over magazines it was 186 mm inboard and 136 mm outboard.
In addition there were several bulkheads ("Paratie Paraschegge") as thick as 36, 24 mm and 15 mm, contributing to the protection of the vitals close to the outboard area, while there was an upper belt ("Corazza di murata"), contributing to protect the outboard part at long-average ranges from shells with AoF of 35°of 70 mm KC vertical armor around and over the whole citadel.
In conclusion, while I agree with you about the potential "weakness" and discontinuity of the outboard part (5 to 7 meters large) scheme, I really wouldn't count on many crippling hits in a potential confrontation with QE's.....