What if Bismarck hit Rodney early on?

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Re: What if Bismarck hit Rodney early on?

Post by Dave Saxton » Sun Sep 09, 2018 2:47 pm

Rodney was much more vulnerable to shells passing below the belt than either Bismarck or KGV. The belt is both shallow and sloped. There was a probably of Rodney taking such a hit in this scenario.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: What if Bismarck hit Rodney early on?

Post by dunmunro » Sun Sep 09, 2018 7:47 pm

alecsandros wrote:
Sun Sep 09, 2018 1:15 pm
dunmunro wrote:
Sun Sep 09, 2018 12:27 pm
The hull and weather deck of a battleship is thicker than a light cruiser's hull and the 28cm hits were at much closer distance and higher SV. The nominal delay for KM 38cm AP was .035 seconds.
The range at which Graf Spee hit Exeter and Ajax with the deep penetrating hits was probably between 12 to 17km. At this range band, the 283mm/L52 had 10 to 20% less striking velocity then the 380mm/L52.
I must have looked at the 28cm C34 range table. In any event the higher the SV the shallower the trajectory and this equals a greater probability having to pass through more of the ship's structure prior to hitting armour.

93. Perhaps the most interesting point was the mixing of armour-piercing delay action projectiles and direct action. AJAX'S one 11 in. hit and several of EXETER'S were of the delay action type. A delay of 42 feet was measured in AJAX [at ~10k - DM] yds and 65 feet in EXETER. It was most noticeable that at the short range at which the action was fought the 11 in. projectiles proceeded more or less on a horizontal course through the ship and did not directly affect the vitals below.
http://www.naval-history.net/WW2LGGrafSpee.htm

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Re: What if Bismarck hit Rodney early on?

Post by dunmunro » Sun Sep 09, 2018 7:55 pm

alecsandros wrote:
Sun Sep 09, 2018 1:13 pm
dunmunro wrote:
Sun Sep 09, 2018 12:27 pm
Bow on, at 20deg descent a 38cm shell must travel ~60ft to reach the very upper edge of the armoured bulkhead, if it strikes the weather deck.
And if it strikes the side of the forecastle it requires 30ft before striking the forward armored bulkhead (at a point at which it is not full thickness), and 30ft more before reaching the upper forward edge of the main magazines.

The 283mm/L52 fired at 910m/s, and the shell had 407m/s at 20.000meters. The 380mm/L52 fired at 820m/s, and the shell retained 510m/s at 20.000meters.
The forward Armoured bulkhead is full thickness to about 6ft UW. The hull side is 1.5in D steel and at high obliquity will probably decap the shell and/or yaw it

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Re: What if Bismarck hit Rodney early on?

Post by dunmunro » Sun Sep 09, 2018 8:01 pm

Dave Saxton wrote:
Sun Sep 09, 2018 2:47 pm
Rodney was much more vulnerable to shells passing below the belt than either Bismarck or KGV. The belt is both shallow and sloped. There was a probably of Rodney taking such a hit in this scenario.
Rodney's belt had a similar UW height as Bismarck but appreciably less than on KGV. It might be possible for a functional 38cm AP round to pass beneath the belt but it should detonate well above the magazine.

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Re: What if Bismarck hit Rodney early on?

Post by swpz » Sun Sep 09, 2018 10:15 pm

dunmunro wrote:
Sat Sep 08, 2018 7:35 pm
Both ships primarily engaged Bismarck's port side. Rodney (and to lesser extent KGV) briefly engaged Bismarck's starboard side. Rodney's salvo record is clear and it states that she opened fire with an incorrect range and it took her some time before she straddled. Bismarck's 13in side armour was largely submerged due to previous battle damage and in the high swells prevalent during the battle was largely shielded from being hit.

Anything you may have read from any source that attributes specific hits to Rodney or KGV (or any other ship) is wrong. This was all pure speculation. There was no observer who could distinguish 14in salvos or hits from 16in salvos or hits, except for when KGV and Rodney closed to near point blank range and even then, when hits could be seen through the smoke and flame onboard Bismarck, there is no way to correlate the hits on the wreck to specific shots fired. KGV and Rodney could only tell a 14in salvo from a 16in salvo by means of a horn that would sound when their salvo was expected to land. External observers could not possibly identify a 14in or 16in salvo because they had no means of precisely timing the salvos to identify their ship of origin. The only way another ship could positively indentify a salvo's origin would be to communicate with that ship via a dedicated FC radio link, and we know that neither KGV or Rodney did this.

What we do know is that KGV had much more modern FC equipment than Rodney and FC radar, which Rodney lacked. It is a mathematical certainty that KGV was scoring, by far, the greater number of hits from 0848-0920. Testing against armour plate, including some from Tirpitz showed that 14in AP rounds could penetrate any armour that Bismarck possessed. At inclinations over 40 degrees 14in and 16in AP would begin to fail to penetrate. Any 14in hit with an inclination of 30 degrees or less would penetrate any armour on Bismarck. There is a very narrow band of inclinations maybe ~5-10 degrees wide, where a 16in shell would penetrate when a 14in wouldn't. Unfortunately there has been a tendency for writers to attribute any penetrating hit identified on Bismarck to a 16in shell when this is simply not possible to do.
Thanks for the correction.

If KGV had the range and better FC why did she score no hits during almost 15 minutes of firing? We know for a fact(?) that the hit(s) at 09:02 was(were) scored by Rodney (this is confirmed by Campbell's account which is actually what led me to this scenario); so despite having the incorrect range, she scored first. How many shells were fired by the British in the first 10 minutes of the battle?

So aside from that we don't actually know which ship did what damage.

How close did KGV go? Rodney is recorded to have closed to about 2500m; did KGV do the same or did she stay further out?

This article here is interesting as it states KGV was firing at Rodney's splashes and not Bismarck herself: http://www.navweaps.com/index_tech/tech-016.php

--

With regards to a bow hit on Rodney before the armored bulkhead, just how much resistance would the structures actually give? In the Hood scenario (Juren's paper) one of the proposed hit locations was a shell landing short, diving and penetrating under the belt into an area next to the magazines. I recall that it was suggested that the structures which were unarmored would have provided no more retardation to the shell than seawater would - so practically nil.

Assuming a shell hit and penetrated the bulkhead, would a detonation in the handling room (as per alecsandros' linked image) be enough or would the shell have to penetrate into the magazine itself to trigger another such explosion? Assuming A magazine did suffer some sort of conflagration (what would be the chances of this to begin with even assuming a shell penetrated and detonated in the next room), how much cordite was in A magazine? Per my understanding Hood had her magazines below the shell handling rooms but Rodney seems to have a slight separation between the magazines in that it's 3 independent units.

--
RF wrote:
Fri Sep 07, 2018 9:12 am

This was not an option because of the KGV fuel situation, and with Churchill in the background wanting action. KGV would have to engage with the two cruisers in support and whatever firepower Rodney had.
This leads to an even more interesting scneario but it goes to the realm of politics. What would the consequences have been for Churchill had Bismarck survived the encounter and not only damaged Rodney but took one of the cruisers with her? Let's say she's scuttled afterwards when the KM makes it to the scene with whatever they have but this fact wouldn't have been known. The propaganda value would have been very interesting at that critical time when everything was going wrong for the British.

--
Dave Saxton wrote:
Fri Sep 07, 2018 3:23 pm
Indeed, a hit to the foretop was also the case with the Scharnhorst at N. Cape. I have mentioned before that this was most unlucky. However, it was not really uncommon. Besides the Bismarck, it also happened to South Dakota. Kirishima hit the SD's foretop fire control station with a 6" round from 10,000 meters with its first salvo. A 14" round passed through Washington's SK radar antenna in the same battle. A few meters lower and it would have hit Washington's main fire control position. A 6" round passed through Graf Spee's foretop below the fire control station. It severed electrical power and communications to the position and the radar. This turned the battle. A 15" round passed through Gneisenau's foretop on April 9th 1940, knocking out the radar and causing Luetjen's to seek to disengage. Not uncommon.
Interesting. Most accounts I've read saw that the blast from her own guns knocked out her (SD's) radar and severed wires which caused electricity to short out leaving her blind (think the book was Jane's warships of the 20th century). The rest, curious. So now that uncommon but still rare - do we have any cases for the British and the Italians? Think they fought more surface engagements (ship wise) than pretty much everyone else combined.

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Re: What if Bismarck hit Rodney early on?

Post by dunmunro » Sun Sep 09, 2018 11:44 pm

swpz wrote:
Sun Sep 09, 2018 10:15 pm
dunmunro wrote:
Sat Sep 08, 2018 7:35 pm
Both ships primarily engaged Bismarck's port side. Rodney (and to lesser extent KGV) briefly engaged Bismarck's starboard side. Rodney's salvo record is clear and it states that she opened fire with an incorrect range and it took her some time before she straddled. Bismarck's 13in side armour was largely submerged due to previous battle damage and in the high swells prevalent during the battle was largely shielded from being hit.

Anything you may have read from any source that attributes specific hits to Rodney or KGV (or any other ship) is wrong. This was all pure speculation. There was no observer who could distinguish 14in salvos or hits from 16in salvos or hits, except for when KGV and Rodney closed to near point blank range and even then, when hits could be seen through the smoke and flame onboard Bismarck, there is no way to correlate the hits on the wreck to specific shots fired. KGV and Rodney could only tell a 14in salvo from a 16in salvo by means of a horn that would sound when their salvo was expected to land. External observers could not possibly identify a 14in or 16in salvo because they had no means of precisely timing the salvos to identify their ship of origin. The only way another ship could positively indentify a salvo's origin would be to communicate with that ship via a dedicated FC radio link, and we know that neither KGV or Rodney did this.

What we do know is that KGV had much more modern FC equipment than Rodney and FC radar, which Rodney lacked. It is a mathematical certainty that KGV was scoring, by far, the greater number of hits from 0848-0920. Testing against armour plate, including some from Tirpitz showed that 14in AP rounds could penetrate any armour that Bismarck possessed. At inclinations over 40 degrees 14in and 16in AP would begin to fail to penetrate. Any 14in hit with an inclination of 30 degrees or less would penetrate any armour on Bismarck. There is a very narrow band of inclinations maybe ~5-10 degrees wide, where a 16in shell would penetrate when a 14in wouldn't. Unfortunately there has been a tendency for writers to attribute any penetrating hit identified on Bismarck to a 16in shell when this is simply not possible to do.
Thanks for the correction.

If KGV had the range and better FC why did she score no hits during almost 15 minutes of firing? We know for a fact(?) that the hit(s) at 09:02 was(were) scored by Rodney (this is confirmed by Campbell's account which is actually what led me to this scenario); so despite having the incorrect range, she scored first. How many shells were fired by the British in the first 10 minutes of the battle?

So aside from that we don't actually know which ship did what damage.

How close did KGV go? Rodney is recorded to have closed to about 2500m; did KGV do the same or did she stay further out?


As I've explained anyone who states that Rodney or KGV scored specific hits at a specific time is simply speculating.

Norfolk claimed to have observed hits from Rodney at ~0849 from Rodney's salvos 3 and 4 fired at 0848, yet Rodney's own records state she was firing with an incorrect range (23500 yds) and that neither salvo fell near the target. OTOH, KGV's initial salvos were radar ranged and had a much higher probability of scoring straddles and hits. For several minutes after her first two salvos KGV probably spotted Rodney's salvos as her own but this was sorted out at 0853.

Rodney claimed 6 straddles from 0858 to 0913 and her first claimed hit was at 0908 from salvo 31, although observers elsewhere made claims on her behalf including hits at 0902. Rodney claimed 12 more straddles from 0913 to 0930 and was undoubtedly hitting hard at this point.

KGV claimed 14 straddles from 0853 to 0913 and she claimed her first hit from a salvo fired at 0853. KGV claimed 4 more straddles from from 0913 to 0930.

Roberts states that by 0931 all of Bismarck's 38cm turrets were out of action although various accounts give different times.


The best single article on this is The Final Action by John Roberts in Warship issue 28, Oct 1983. Roberts states:
In the early stages of the action, until 0913, KGV employing her type 284 radar had an advantage over Rodney and obtained about 14 straddles to Rodney's 8 or 9 [Rodney's record of salvos claims 6 - the rest presumably were claimed for her - DM]. It is difficult however, to attribute any particular damage to either ship - it was during this period that Bismarck's A and B turrets and the forward FC positions were disabled...
Of course Roberts does fall prey in the article to the tendency to want to attribute specific early hits to Rodney when there is no real basis for this.

Can you give me the name of Campbell's article and/or book? I have the KGV gunnery report for this action and Roberts provides much of the data from Rodney's report including her Record of 16in Salvos.

By 0913 KGV was down to ~12000 yds and she eventually closed to 4000 yds after ~10:00. You can see a plot of her movements here:

http://navweaps.com/index_inro/INRO_Bismarck.php

and this is an interesting article but please take any claims for specific hits from specific ships with a large grain of salt.

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Re: What if Bismarck hit Rodney early on?

Post by dunmunro » Mon Sep 10, 2018 12:25 am

swpz wrote:
Sun Sep 09, 2018 10:15 pm

With regards to a bow hit on Rodney before the armored bulkhead, just how much resistance would the structures actually give? In the Hood scenario (Juren's paper) one of the proposed hit locations was a shell landing short, diving and penetrating under the belt into an area next to the magazines. I recall that it was suggested that the structures which were unarmored would have provided no more retardation to the shell than seawater would - so practically nil.

Assuming a shell hit and penetrated the bulkhead, would a detonation in the handling room (as per alecsandros' linked image) be enough or would the shell have to penetrate into the magazine itself to trigger another such explosion? Assuming A magazine did suffer some sort of conflagration (what would be the chances of this to begin with even assuming a shell penetrated and detonated in the next room), how much cordite was in A magazine? Per my understanding Hood had her magazines below the shell handling rooms but Rodney seems to have a slight separation between the magazines in that it's 3 independent units.


Hood's magazines were above the shell rooms. Rodney and KGV had them below the shell rooms. This increased the probability that diving shells would detonate before entering the magazines as their fuzes will be activated upon hitting the water.

The weather deck and/or hull are thick enough to activate the fuze on a AP shell and this limits the distance that the shell can travel before it detonates. They are also thick enough to knock off the AP cap which aids the shell in penetrating thick armour, and they will probably yaw the shell to that it doesn't strike the armour perpendicular which considerably reduces it's penetrative ability.

I think you are confusing the forward armoured bulkhead with the armoured barbettes. The 16in barbettes have 15in of armour on those portions above the 6.25in armoured deck. In any event there is an almost zero probability of a 38cm shell being able to reach the main magazines by passing through the forward armoured bulkhead.

The RN did not store large quantities of propellant in the handling rooms and the odds of a hit there causing a magazine explosion are very low as the RN learned from WW1 and used elaborate precautions to prevent this from happening.

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Re: What if Bismarck hit Rodney early on?

Post by Dave Saxton » Mon Sep 10, 2018 3:16 am

dunmunro wrote:
Sun Sep 09, 2018 8:01 pm
Dave Saxton wrote:
Sun Sep 09, 2018 2:47 pm
Rodney was much more vulnerable to shells passing below the belt than either Bismarck or KGV. The belt is both shallow and sloped. There was a probably of Rodney taking such a hit in this scenario.
Rodney's belt had a similar UW height as Bismarck but appreciably less than on KGV. It might be possible for a functional 38cm AP round to pass beneath the belt but it should detonate well above the magazine.
Bismarck's belt extended 2.5 meters below the waterline. KGV's belt extended 2.54 meters below the waterline. Rodney's belt only extended 1.8 meters below the waterline. Additionally, the slope of 18 degrees increases the vulnerability to diving shell.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: What if Bismarck hit Rodney early on?

Post by Dave Saxton » Mon Sep 10, 2018 3:25 am

dunmunro wrote:
Sun Sep 09, 2018 7:55 pm
The hull side is 1.5in D steel and at high obliquity will probably decap the shell and/or yaw it
At least .2 calibers of armour grade steel is usually required in most applications of vertical armour. Littorio's de-capping plate was 70mm of armour grade steel. True the 1.5-inch upper deck of South Dakota de-capped the Kirishima 14" at extremely acute obliquity, but that was also armour grade steel.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: What if Bismarck hit Rodney early on?

Post by Dave Saxton » Mon Sep 10, 2018 4:05 am

swpz wrote:
Sun Sep 09, 2018 10:15 pm
....Interesting. Most accounts I've read saw that the blast from her own guns knocked out her (SD's) radar and severed wires which caused electricity to short out leaving her blind (think the book was Jane's warships of the 20th century). The rest, curious. So now that uncommon but still rare - do we have any cases for the British and the Italians? Think they fought more surface engagements (ship wise) than pretty much everyone else combined.
To clarify, after firing 14 broadsides, shock caused the circuit breakers in the main power supply to trip, knocking out the electrical power to the guns, FC, radar, comms... This was about 30 minutes before it came under fire from Japanese forces. In the meantime as power started to come back it opened fire on a target over the stern. They thought they were firing at a Japanese cruiser but it was actually a retiring American destroyer. When the DD flashed its running lights, they thought it was the target blowing up. The firing over the stern caused the aircraft on the catapults to catch on fire. The next salvo blew them overboard, but an aviation gasoline line was severed resulting in a geyser of flames shooting way up in the sky. This along with passing in front of burning and sinking American destroyers announced its position to the enemy. The foretop was hit right away. Later on it started tripping breakers again due to incoming rounds severing cabling and the resulting short circuits. Once power is lost it could take tens of minutes for the radars to become fully functional again. Nonetheless, the foretop had already received a direct hit from when it first came under fire.

Foretops are more likely to get hit because they tower way up in the air.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: What if Bismarck hit Rodney early on?

Post by dunmunro » Mon Sep 10, 2018 4:42 am

Dave Saxton wrote:
Mon Sep 10, 2018 3:16 am
dunmunro wrote:
Sun Sep 09, 2018 8:01 pm
Dave Saxton wrote:
Sun Sep 09, 2018 2:47 pm
Rodney was much more vulnerable to shells passing below the belt than either Bismarck or KGV. The belt is both shallow and sloped. There was a probably of Rodney taking such a hit in this scenario.
Rodney's belt had a similar UW height as Bismarck but appreciably less than on KGV. It might be possible for a functional 38cm AP round to pass beneath the belt but it should detonate well above the magazine.
Bismarck's belt extended 2.5 meters below the waterline. KGV's belt extended 2.54 meters below the waterline. Rodney's belt only extended 1.8 meters below the waterline. Additionally, the slope of 18 degrees increases the vulnerability to diving shell.
KGV's belt was 23.5ft high. At deep load the belt was submerged to about 13ft (4m). Bismarck's belt including the upper strake had about the same height but it started one deck higher than KGV.

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Re: What if Bismarck hit Rodney early on?

Post by dunmunro » Mon Sep 10, 2018 5:33 am

Dave Saxton wrote:
Mon Sep 10, 2018 3:25 am
dunmunro wrote:
Sun Sep 09, 2018 7:55 pm
The hull side is 1.5in D steel and at high obliquity will probably decap the shell and/or yaw it
At least .2 calibers of armour grade steel is usually required in most applications of vertical armour. Littorio's de-capping plate was 70mm of armour grade steel. True the 1.5-inch upper deck of South Dakota de-capped the Kirishima 14" at extremely acute obliquity, but that was also armour grade steel.
D steel is similar to STS. In any event we are talking about impact at ~70+ degrees from the normal so fuze activation, deflection and decapping are all highly probable.

In addition, and I should have mentioned this sooner, Rodney's armoured deck extended forward past the forward armoured bulkhead at the same height as it's lower 12in edge, so for a shell to hit a magazine from a forward bearing it would have to avoid the armoured deck extension (see RA Burt for details).

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Re: What if Bismarck hit Rodney early on?

Post by alecsandros » Mon Sep 10, 2018 5:40 am

dunmunro wrote:
Sun Sep 09, 2018 7:55 pm
The forward Armoured bulkhead is full thickness to about 6ft UW. The hull side is 1.5in D steel and at high obliquity will probably decap the shell and/or yaw it
1.5" of construction grade steel is nothing for a 15" APC projectile. A minimum of 2" of armor-grade steel was required for decapping for higher obliquity badns, and a minimum of 3" for decapping at all probable obliquities.
As for impact obliquity, this varied a lot during the battle, with the intial phase having a rather end-on approach and therefore a low obliquity (between firing ships). Actual obliquity at the point of impact would differ , on ship roll, momentary course alterations (with or without order to do so - see Bismarck's erratic course), etc.

Nonetheless, for the point of this discussion, the mechanics of the 380mm shell at ~20km were good enough to ensure perforation into the main forward magazine of HMS Rodney.

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Re: What if Bismarck hit Rodney early on?

Post by Dave Saxton » Mon Sep 10, 2018 3:45 pm

dunmunro wrote:
Mon Sep 10, 2018 4:42 am


KGV's belt was 23.5ft high.
My sources indicate 2.54 meters below the waterline and 4.6 meters above the waterline = 23.5 feet. The KGV belt upper edge meets the MAD one level below the weather deck.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: What if Bismarck hit Rodney early on?

Post by Dave Saxton » Mon Sep 10, 2018 3:55 pm

dunmunro wrote:
Mon Sep 10, 2018 5:33 am


D steel is similar to STS.
D steel is 80,000 psi tensile at 17% elongation.
STS is 120,000 psi tensile at 25% elongation.

STS will consume a lot more energy.

I.5-inch D S may initiate fuse action but the enemy APC could travel up to 20 meters before bursting at these ranges.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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