Here's some further musing on armour.
By DK Brown, 15" of Wrought = 5 3/4 " of Krupp or 7 1/2 " of Harvey.
Now, AP values for various guns are reported in Brassey at the muzzle, and for British guns out to 3,000 yards.
So let's see how the Formidable class stands up to German main armament guns at muzle and 3,000 yards. (This is basically assuming that the fall-off in effectiveness for German guns is proportional to British guns of similar calibre.)
Formidable (Krupp armour)
- Belt: 9 inches (229 mm)
- Bulkheads: 9–12 inches (229–305 mm)
- Barbettes: 12 inches (305 mm)
- Gunhouses: 8–10 inches (203–254 mm)
- Casemates: 6 inches (152 mm)
- Conning tower: 14 inches (356 mm)
Converting to Wrought Iron equivalent:
- Belt: 23.5 inches
- Bulkheads: 23.5-31.3 inches
- Barbettes: 31.3 inches
- Gunhouses: 20.9-26.1 inches
- Casemates: 15.6 inches
- Conning tower: 36.5 inches
German gun wrought-iron penetration at muzzle:
11"/40 = 30.6"
11"/35 = 26.7"
10.3"/19 = 15"
9.45/40 = 29.7"
9.45/32 = 20.7"
For the British 12" gun, penetration falls off from muzzle to 3000 yards at a ratio of about 1:0.73.
For the British 10" gun it's 1:0.68.
For the British 9.2" gun it's 1:0.66.
So at 3000 yards:
11"/40 = 21.4"
11"/35 = 18.7"
10.3"/19 = 10.2"
9.45/40 = 19.6"
9.45/32 = 13.6"
At 3000 yards most of the critical parts of the British ships are not really vulnerable to single penetrations. Only the heaviest 11" guns can penetrate the gunhouses, for example, which means the British cordite is not as much of a problem as it might have been.
Now, let's turn that about - since we have 3,000 yard values for the British I'll read them off directly.
Looking at the SMS Deutschland, as an example of the most heavily protected German PDNs:
- Belt: 100 to 240 mm (3.9 to 9.4 in)
- Turrets: 280 mm (11 in)
Converting to wrought iron:
- Belt: 10" to 24.5" wrought iron equivalent
- Turrets: 28.7" wrought iron equivalent
British 12" mark VI
24.4" at muzzle, 16.1" at 3000 yards
12" mark VIII
36.8" at muzzle, 26.6" at 3000 yards
12" mark IX
39.7" at muzzle, 28.7" at 3000 yards
So at 3000 yards, the Mark IX can penetrate any part of the German PDNs and the Mark VIII can penetrate anything but a turret face.
The Mark X (arming anything Dreandought and later) is not on the table.
The Mark IX armed the Formidable, London, Duncan and King Edward VII classes - the latest PDNs of the British line.
So I think the proposition "British Pre-Dreadnoughts were individually superior" holds up here, in a simulated battle at 3,000 yards of range.
To this we can add that the British have more Formidable-and-later PDNs (23) than the Germans have PDNs at all (22), and that due to the radically inferior nature of half the German battle line at doing any damage to the British Later PDNs then the German PDN line is actually smaller than 22 in effectives. (The Kaiser Friedrich III class could not penetrate turret or belt on a Formidable class if their guns were touching the armour!)