Gunfire hits below the waterline?

[BobDonnald]

The loss of the IJN Kirishima's has been attributed to both scuttling and being holed below the waterline. Since neither the Bismarck nor the Scharnhorst sinkings describe such hits and damage resulting from them, is this something rare? I know that USS Boise took a special IJN diving shell below the waterline that flashed a magazine. Both the final battle of the Bismarck and Scharnhorst had gunfire exchanges at similar ranges to the Second Guadacanal. So does the thicker armor belts of the German ships defeat any shell that first hit water?

[Steve Crandell]

The loss of the IJN Kirishima's has been attributed to both scuttling and being holed below the waterline. Since neither the Bismarck nor the Scharnhorst sinkings describe such hits and damage resulting from them, is this something rare? I know that USS Boise took a special IJN diving shell below the waterline that flashed a magazine. Both the final battle of the Bismarck and Scharnhorst had gunfire exchanges at similar ranges to the Second Guadacanal. So does the thicker armor belts of the German ships defeat any shell that first hit water?

Yes, it is rare. No, the German armor scheme doesn't prevent them. Bismarck received a shell from PoW which passed under Bismarcks main armor belt and resulted in flooding of fire rooms.

Salt Lake City took an underwater hit at the Battle of the Komandorski Islands.

Rodney was too close to achieve much in the way of underwater hits on Bismarck during the final stage of that battle, given conventional AP shells. It is possible that IJN shells would have been more effective at sinking Bismarck.

Incidentally, recent research of IJN testimony by R. Lundgren pretty conclusively proves that IJN Kirishima was not scuttled. I think it is even possible that one or more shells from Washington passed through Kirishima and exited on the disengaged side of the ship below the waterline. In any case, her watertight subdivision was probably pretty much destroyed in some areas of the ship.

[Thorsten Wahl]

The loss of the IJN Kirishima's has been attributed to both scuttling and being holed below the waterline.

given the location of hits on Kirishime in Rob Lundgrens analysis it appears that german ship shouldnt suffer the same fate
as majority of UW-hits seem to have been occured through the belt and the japanese belt seem shallower than the german.

In the german case the projectiles could have pentrated the belt too, but should became rejected at the scarp so flooding would occur above the armored deck but only to a limited degree in the area of the scarp. Areas within the citadel like machinery spaces or magazines should not be affected by flooding.

Nevertheless diving hits under the side protection are possible, but in this case the american projectiles should be duds to achieve the required UW trajectory.

In Rodneys case the considerable wave height should be responsible for the lack of UW hits at low AOF.

[alecsandros]

The loss of the IJN Kirishima's has been attributed to both scuttling and being holed below the waterline.

given the location of hits on Kirishime in Rob Lundgrens analysis it appears that german ship shouldn suffer the same fate
as majority of UW-hits occured through the belt.
In the german case the projectiles could have pentrated the belt too, but should became rejected at the scarp so flooding would occur above the armored deck but only to a limited degree in the area of the scarp. Areas within the citadel like machinery spaces or magazines should not be affected by flooding.

In Rodneys case the considerable wave height should be responsible for the lack of UW hits at low AOF.

...USS Washington's official report mentions "8 or 9 hits". The behavior of 16"/L45 shells (shown as exploding immediately behind the armor belt, after traveling a few meters, allthough velocity was ~ 600m/s) is not consistent with the behavior of the same shells fired by USS Massachussets at Jean Bart 1 week before (whihc traveled a measured 15m and 21meters respectively, at a striking velocity of ~ 480m/s).

It may be that Mr Lundgren is correct, and that drawing on the Japanese damage report is accurate. I do not know. It seems odd to me that Wasington's crew couldn't count the shell splashes and that the 16" shells exploded so quickly. It doesnt mean it couldn't happen.. just that.. it's odd..

@Thorsten:

Swaping Kirishima with Bismarck, only a few u-w shells would hit Bismarck's belt, which was a bit shallow (H-class battleships designers learned from this and extended the main belt 2 meters lower). Most of them would pass beneath the belt/stearing gear armor, and strike at the TDS.
Great flotation damage would be suffered, but Bismarkc's pumping capacity was considerably larger than her contemporaries, so she may have survived, albeit heavily damaged.

cheers,

[Thorsten Wahl]

Swaping Kirishima with Bismarck, only a few u-w shells would hit Bismarck's belt,

Im sorry
Kirishimas belt is extends at best one meter below WL.
At battle condition Bismarcks belt extends in the order of 2-2,3 m below WL.

at ~6 degrees AOF (and a straight UW trajectory implied) a hit at a ship within 1 m depth required an impact 10 m short

A dive at 2 m depth requires approximately 20 m short. Normally the fuze should be set at impact on water, therfor a properly functioning projectile should detonate past 15 m UW travel.

[alecsandros]

Swaping Kirishima with Bismarck, only a few u-w shells would hit Bismarck's belt,

Im sorry
Kirishimas belt is extends at best one meter below WL.
At battle condition Bismarcks belt extends in the order of 2-2,3 m below WL.

at ~6 degrees AOF (and a straight UW trajectory implied) a hit at a ship within 1 m depth required an impact 10 m short

A dive at 2 m depth requires approximately 20 m short. Normally the fuze should be set at impact on water, therfor a properly functioning projectile should detonate past 15 m UW travel.

With all due respect Thorsten,

But usualy large ships traveling at high speed produce a cavity around them, especialy at the front of the ship, of up to 1 meter depth, that futher exposes their (normally) submerged portions.
This was obvious during Littorio/Veneto speed trials, and would almost certainly be the case for Bismarck/Tirpitz in such a setup (i.e. moving at 30kts+).
Thus a hit below the belt would be possible with shells falling closer to the ship then geometry would suggest.

[Alberto Virtuani]

Hi everyone,
my 2 cents opinion here about Bismarck underwater vulnerability (I don't know Kirishima action details).

Bismarck class, as Alecsandros pointed out, had a belt that was not very extended below waterline, and the hit in the vitals (generator room destruction and flooding of boiler room) received from PoW on May 24 demonstrates that she was vulnerable to underwater hits below the belt.
BTW all the 3 BB involved in the action (all travelling at very high speed) possibly received such hits: Hood most probable cause of lost is an underwater hit according to Bill Jurens analysis and PoW 15" underwater hit (albeit a dud) penetrated the ship vitals. Please consider also that KGV class had a much deeper belt than BS under water....

The reasons why BS did not (probably, we will never know for sure of course....) receive any underwater hit on May 27 is IMHO due to several concurrent reasons:
1) the fact that she was quite deep in the water due to the torpedo and shell hits already received in the previous days when the battle started, thus minimizing the risk to expose her side under the belt; 2) she was travelling at very slow speed (so no cavity effect along her side);
3) she was engaged mostly at very short distance, therefore flat trajectories, not very "good" at travelling under water (more to bounce on hitting water),
4) she was mostly engaged from her port side and from the bow direction while she was quite heavily listing to port (see the Baron witness) and she was down by the bow, thus not exposing much the under-belt port side, maximizing the protection effect of the belt/sloped deck and of the bulkhead/deck combination.

Bye, Alberto

[Thorsten Wahl]

Bismarck class, as Alecsandros pointed out, had a belt that was not very extended below waterline, and the hit in the vitals (generator room destruction and flooding of boiler room) received from PoW on May 24 demonstrates that she was vulnerable to underwater hits below the belt.

Please consider also that KGV class had a much deeper belt than BS under water....

Ther is no question on the result of bypassing the side protection of Bismarck and vulnerability against such types of hits. But did the hit really reveal a weakness at this distance. Could a penetration within the ship have been avoided (at was costs)?

Generally spoken, the hit occured at a distance were no belt alone (inclined or not) offered protection for vitals against this type of pentrating hit, as the underwater part of side protection of most ships is not offering a better IZ against projectile attack, compared to the part above the waterline. There ar some rare exceptions when thickness of the belt remained the same for all of the covered depth.


In the case of Kirishima the battle distance is far shorter compared to Denmark Strait, so standard side protection is nullified - any projectile that is able to reach the ships side regardless if it hits underwater or above the waterline is likely to penetrate and if the timing of the fuze will allow for detonation within the ship the result should be comprehensible devastating. Even duds will punch large holes in the hull and inner bulkheads.
------------------------------------------------------------------------------------------------------------------------------------------

But usualy large ships traveling at high speed produce a cavity around them, especialy at the front of the ship, of up to 1 meter depth, that futher exposes their (normally) submerged portions.

For easy accomplishment I had choosen a simplified explantion model without creation of wave crests and wave troughs.

[Alberto Virtuani]

@Thorsten Wahl:
hi Thorsten, do you know from any source whether the hit from PoW perforated the belt, the sloped deck and the torpedo bulkhead or whether it perforated the belt plus the horizontal deck or whether it just slipped under the belt of BS penetrating the thin torpedo bulkhead only ?
I suspect it was the last option as I doubt a 14" at more than 15000 yards could penetrate the side protection plus the (sloped or not) deck anyway......

Bye, Alberto

[alecsandros]

@Thorsten Wahl:
hi Thorsten, do you know from any source whether the hit from PoW perforated the belt, the sloped deck and the torpedo bulkhead or whether it perforated the belt plus the horizontal deck or whether it just slipped under the belt of BS penetrating the thin torpedo bulkhead only ?
I suspect it was the last option as I doubt a 14" at more than 15000 yards could penetrate the side protection plus the (sloped or not) deck anyway......

Bye, Alberto

... It went beneath the belt, but it did not penetrate the TDS, but the outer skin of the ship.
The 14" shell then exploded near to or in contact with the 45mm Whotan torpedo bulkhead, creating fractures/holes in it, which, in time, lead to gradual flooding and the abandonment of a boiler room. It is easy to see the shell's explosion was contained outside the ship's armor, as no one was injured/killed by the blast near the boiler room.

[Thorsten Wahl]

simplified model of the trajectory(no waves, no upturning trajectory, no deceleration on water entry...)
the compartment above(orange) the electrical powerplant(blue) was a ammunition chamber, flooded boiler room (green)

[alecsandros]

But did the hit really reveal a weakness at this distance. Could a penetration within the ship have been avoided (at was costs)?

Generally spoken, the hit occured at a distance were no belt alone (inclined or not) offered protection for vitals against this type of pentrating hit, as the underwater part of side protection of most ships is not offering a better IZ against projectile attack, compared to the part above the waterline. There ar some rare exceptions when thickness of the belt remained the same for all of the covered depth.

... For what we know, the H-39 battleship would have behaved better, as his belt ran deeper, and the proposed 14" shell would have exploded in contact with the 300mm belt, probably causing negligible shock damage to the structure and holdings.

However, the more damaging hit was ultimately the bow hit, also of 14", which slowed down the Bismarck by 2-3 kts and lead to a higher fuel consumption than normal, due to increased drag in the bows, along with other troubles.

H-39 , and any other contemporary battleship, built or not, would suffer the same troubles.

[Thorsten Wahl]

However, the more damaging hit was ultimately the bow hit, also of 14", which slowed down the Bismarck by 2-3 kts and lead to a higher fuel consumption than normal, due to increased drag in the bows, along with other troubles.

H-39 , and any other contemporary battleship, built or not, would suffer the same troubles.

the loss of the boilerroom brought approximately 100 t steam less per hour, this appears as the main reason of reduced speed
nevertheless the roughened hull cause increased drag and fuel consumption too.

[Alberto Virtuani]

Thanks Thorsten and Alec !

From what you say, I agree that H-39 with a deeper belt would have behaved better, especially because the 14" exploded "near or in contact" with" the torpedo bulkhead. Would the fuse have made it exploding after it (the 45mm TDS couldn't possibly stop a 14" even travelling at (an up to a certain extent) reduced speed, it could have caused even much more serious damages and casualities as "the compartment above(orange) the electrical powerplant(blue) was a ammunition chamber, flooded boiler room (green)".....

However I also agree that any BB was exposed to underwater hits as the 15" dud shell received by PoW (with her very deep belt under waterline) demonstrated.

Bye, Alberto

[dunmunro]

Swaping Kirishima with Bismarck, only a few u-w shells would hit Bismarck's belt,

Im sorry
Kirishimas belt is extends at best one meter below WL.
At battle condition Bismarcks belt extends in the order of 2-2,3 m below WL.

at ~6 degrees AOF (and a straight UW trajectory implied) a hit at a ship within 1 m depth required an impact 10 m short

A dive at 2 m depth requires approximately 20 m short. Normally the fuze should be set at impact on water, therfor a properly functioning projectile should detonate past 15 m UW travel.

The roll of the ship would expose it to a greater/lessor probability of an UW hit depending on where in the roll it struck.