(from Chapter 16 of Professor Krylov's Navy)
Your Excellency! This is how I understand ship
unsinkability.
1) It is often said that “ship unsinkability is provided
by partitioning the hold into compartments.” This is inaccurate. The ship reserve buoyancy provides unsinkability.
Reserve buoyancy is in turn the volume of the above-water part of the ship,
bounded by the upper watertight deck. Partitioning of the hold into
compartments is one way to utilize reserve buoyancy.
2) Besides buoyancy, it is necessary to provide for the
ship stability. This is achieved by coordinating
partitioning of the above-water parts with partitioning of the hold and by
arranging appropriate system of flooding the compartments to right the ship.
Only such righting provides ability to use the entire reserve buoyancy. The
bilge system is powerless in controlling the holes. When partitioning the hold
and the above-water parts, we must be guided by calculations of the effect of
flooding the compartments on the list, trim, and stability. The principle of
partitioning should be that buoyancy is lost prior to stability—in short, that the ship sinks without capsizing.
3) Any damage to the freeboard causes corresponding
reduction in reserve buoyancy and stability of the ship. The desire to provide
this reserve in a battle led to change in the ship armor. Before, the purpose
of the armor was seen in covering the machinery, boilers, and generally vital
parts of the ship. To provide buoyancy, the presence of unarmored freeboard was considered sufficient.
The development of the rapid-fire artillery forced changes to the armor,
considering as its main purpose: to ensure reserve buoyancy and stability of
the ship.
4) The natural
development of the first type of armor led to concentration of all the vital
parts of the ship in her middle, covering this part with the thickest possible
armor over the least possible area.
5) The second type, conversely, requires covering the
largest possible area of sideboard, with the same thickness everywhere or even
thicker at the ends.
6) In practice, both systems are often combined, covering
the middle part of the ship along the waterline with the thicker armor and the
rest of the sideboard with the armor of the equal or almost equal thickness
everywhere.
7) Any armor can be pierced by a gun of a proper caliber
within limits of certain angles of impact and range; hence the opportunity to
equalize probabilities: having superiority in artillery over the more
powerfully armored adversary, to inflict on him in the same time the same total
area of the holes as is expected to receive from him. Thus, the question of the
battle between armor and artillery as it relates to unsinkability can be
reduced to numerical calculations of probabilities and the expected value of
the area of the holes, similar to the calculations of pension funds and other
insurance enterprises.
8) Rational armoring
must be in certain correlation to the partitioning of the hold into
compartments; this latter to the radius of destruction from the torpedo hole.
9) Until now, in designing the warships, for the most part,
the same stability calculations were made as for the sailing vessels. When
considering such important quality as survivability or unsinkability of a ship,
not calculations, precise and defined, but general considerations sufficed—to
put it bluntly, conversations. Many shortcomings arose. For example, on some
vessels, the mess deck partitioning in the number of compartments, does not
correspond to the hold partitioning. Damage to the deck and to the freeboard
causes excessive decrease of stability; there are many small compartments in
the hold, 10 tons of volume or less, next to the compartment of 800 tons. The
centerline bulkhead in the boiler room is made without doors, so after ramming in the middle, the battleship will
capsize before the crew manages to think
about what to do to prevent the ship’s loss. On other vessels, shipbuilders have
fallen into opposite extreme, not making the centerline bulkhead at all, as if
forgetting that this is one of the main ship ties. All this happens because shipbuilders
do not trust calculations and do not establish basic principles for them, so
assessment of the requirements for the warship is absent. Any rational design should be based on number and
measure. However, we must remember that awareness of shortcomings is the first
step in correcting them.
I do not know how the foregoing will correspond to the
content of your lecture. In any case, I am entirely at the disposal of Your
Excellency.
With the deepest respect and sincere devotion, I have the
honor to be Your Excellency’s obedient servant,
A. Krylov
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