Main battery and underwater protection for Battleships

The following is a translated summary of an article in Marine Rundschau 23 1912, a reprint of Engineer Salvatore Orlando's article in Revista Maritima from 11th November 1911.

Tactical considerations are generally the decisive reason for placement of the artillery. The ship designer has to take into account the entire organism of the ship and the armament has to be designed in such a way it can account for the tactical schools to follow. The artillery must predominantly be able to fire over both sides laterally for a classic broadside. However despite this the battery must attempt to prevent large sectors of longitudinal fire with poor effect.

None of these designs adhere to the design principles. Design A has no capability for a full broadside. Design B has poor angles of maximum fire at roughly 90° per side. Design C does have a good 130° sector of fire but has a stem and stern coverage sector of 50° with only a single turret. This can theoretically be brought to 140°/40° respectively but that requires significant extension of the ship and the removal of superstructures. 

When looking at superfiring lay-outs one finds these designs do adhere to the design principles. If a turret beyond the 4th is added then it would not employ its greatest potential due to limited coverage caused by two dead angles afore and astern. Therefore, improvement in firepower is preferably done by increasing the calibre of the artillery.
With 4 turrets of which 2 elevated, each of them has only one dead sector. If the turrets are placed close to each other the blind sector of the lower turret can reach 70° for twin turrets with 34,3 cm guns. This diminishes as the turrets are placed further apart. But can be limited by the need to keep the muzzles away so as to not injure the turret beneath. The minimum blind angle is roughly 60° for 34,3 cm guns. A bit more for triple turrets. The broadside angles can not exceed 120° this way.

The appended sketches illustrate four different methods of superfiring compositions. The first is the classic “Michigan” type. The rest attempts to make the bow-stern fire sectors more effective by moving the turrets to the side.

	Sum Dead Sectors	Sum Broadside	Sum Guns
A	460°	490°	1960°
B	332	554	2216
C	300	570	2280
D	220	610	2440
E	202	619	2476
F	180	630	2514
G	180	630	2520

When it comes to dead angles the superfiring turrets are a clear winner over turrets on the same deck. When looking at the number of guns capable of firing to one side of the ship we can see the same trend. Which can also be seen when we look at the total sum of gun angles.

For fire directly for or aft, the group ABC has only a single turret operational whereas the superfiring layouts of DEFG have two to three. Under those conditions ships of the A, B and especially the C type are unable to effectively engage in a chase or retreating engagement. They thus must angle their profile to half the dead angle, between 6° and 25° degrees, to then be able to use two turrets. Meanwhile the DEFG group is not required to and can exploit two or even three of theirs.

The resulting difference in angles means the difference in speed would thus be V(new) = cos(25) ✕ V(old) = 0,90 V(old). This means a speed difference of around 2½ knots.

The ability to utilise both firepower and speed lead to the same result. Ships with superfiring turrets are preferred to those with turrets on the same level. A principle which the author has mentioned since 1907 and tried to prove was the best for the Italian navy.

	2-turret sector	4-turret sector
D	50°	120°
E	19	98
F	18	108
G	30	120

In regards to which of the superfiring layouts is preferable, if we check the sectors at which only two turrets can fire we see that scheme E and F have the smallest sector. This means that should one turret be knocked out they would have to provide the minimal course shift to bring fire to bear.

If we look at the 4-turret broadside sector D and G are the superior options. The sectors of E F and G could be enlarged should the dead sector of the turrets be kept smaller than 60°. D and especially G are preferred for the broadside, but E and especially F are only slightly inferior. Considering the better extremity sectors this version comes closer to the ideal characteristics.

Underwater protection
There has been a special emphasis on underwater protection since the Russo-Japanese war. Initial attempts of a double or even triple bottom and the armouring of the hull have proved ineffective. It is generally accepted that the armour has to be at least 5 metres away to reduce pressure. Consequently the longitudinal bulkhead is armoured these days.

However, the armouring of this bulkhead has proved vulnerable due to its great height. They often get bent in such a way they tear off at the connection points at the armour deck and double bottom. They have to be thusly designed to: 1) have the lowest possible height to allow the greatest possible resistance; and 2) If it breaks the water that penetrates up to swimming level cannot cause significant transverse movements.

It is known that the armoured deck is most resilient to underwater explosions. The most vivid effect is in the horizontal plane. When tests were carried out the armoured deck withstood explosions that destroyed the bulkheads over a wide area.

By lowering the armoured deck one can lower the height of the bulkheads and furthermore reduce the effects of flooding on the buoyancy.

In a ship with the following parameters:

Length PP: 156,28 m
Length CWL: 165,28 m
Widest beam: 27,80 m
Depth: 7,95 m
Displacement: 21 000t
Height of deplacement origin of mass: 4,50 m
M.F. : 7,00 m

In this example, the height of the bulkhead in the original design is 7,45 m in the middle and 5,65 m at the stern whereas with the new designed underwater protection the heights are 4,5 m and 2,70 m respectively. The new armoured deck would provide better stiffening to the armoured belt and would cause a weight reduction of 190 t in the example given.