What if Bismarck hit Rodney early on?

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alecsandros
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Re: What if Bismarck hit Rodney early on?

Post by alecsandros » Mon Sep 10, 2018 4:47 pm

Dave Saxton wrote:
Mon Sep 10, 2018 3:55 pm
I.5-inch D S may initiate fuse action but the enemy APC could travel up to 20 meters before bursting at these ranges.
At 20.000meters, 380mm APC projectile strikes at 510m/s, thus a perfectly functioning fuze would explode after travelling 18meters (59 feet), while a fuze working such as the ones fired by Graf Spee at River Plate* (about 0,05seconds) would explode after 25,5meters (77feet)

At 18.000meters, 380mm APC projectile strikes at 532m/s, thus travelling 18,62meters (61 feet), or 26,6meters (87feet) respectively.

===
* "62 Evidence from U.S. sources indicates that such an increase in delay would not be unusual. For example, U.S. Navy specifications for the Base Detonating Fuze Mark 21 considered the fuze action satisfactory if the detonation occurred between 0.030 and 0.070 seconds after impact when set for a nominal 0.033 second delay. British experience at the River Plate and elsewhere lead them to estimate the effective German fuze delay as being about 0.05 seconds. "

From http://www.zhanliejian.com/navweaps/INRO_Hood_p3.htm#62

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Re: What if Bismarck hit Rodney early on?

Post by dunmunro » Mon Sep 10, 2018 4:57 pm

Dave Saxton wrote:
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.
This is from G&D:

Image

and their exposition:
The vertical main side belt of cemented armor, 415 feet long and 23 feet deep {56
percent of the waterline length}, was 14.71 inches thick at the main magazines and
13.75 inches thick outside of the propulsion plant. It tapered to 5.38 inches outside
the former and 4.42 inches outside the latter, at a distance of 8.25 feet below the
standard waterline. Armor extending 12 feet below the design waterline, an important
feature, comprised the greatest amount ever so used in a British battleship. The lower
side belt extended 40 feet forward and 37 feet abaft the citadel, comprising underwater
protection for a total of 492 feet
The drawing shows the WL at design standard but it was about 32ft at full load in 1941. Total belt height varied slightly by location.

Edit: G&D have mislabelled this drawing. The WL is actually at 31.5ft draft which is probably a reasonable average action draft in 1941. The total belt height is shown as 23.5ft with 11ft above water and thus 12.5ft below.
Last edited by dunmunro on Mon Sep 10, 2018 6:04 pm, edited 1 time in total.

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Re: What if Bismarck hit Rodney early on?

Post by dunmunro » Mon Sep 10, 2018 5:44 pm

Dave Saxton wrote:
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.
According to Okun D steel is 89000 psi tensile at 22% elongation. Thinner STS plates had lower ratings, probably about 110k according to Okun:

http://navweaps.com/index_nathan/metalprpsept2009.php

at 1640fps SV (23000yds), the projectile will lose about 150fps in penetration. 1500fps and .035sec fuze delay = ~53ft of travel and that's assuming no further obstruction. Yes, longer delay might occur but so might a shorter delay.

The 38cm crane hit on PoW travelled about 30ft prior to detonating.

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Re: What if Bismarck hit Rodney early on?

Post by Dave Saxton » Mon Sep 10, 2018 5:49 pm

My source could well be incorrect. It would not be the first time. I did find an ADM document drawing that shows the KGV belt being about 3.5 meters below and about 3.7 meters above at the deepest waterline. Perhaps the 2.54 meter figure was at light load?

But Rodney's belt depth is the issue.
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 5:52 pm

dunmunro wrote:
Mon Sep 10, 2018 5:44 pm
Dave Saxton wrote:
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.
According to Okun D steel is 89000 psi tensile at 22% elongation. Thinner STS plates had lower ratings, probably about 110k according to Okun:

http://navweaps.com/index_nathan/metalprpsept2009.php

I have primary documents on D steel and Nathan is incorrect on this one.
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 alecsandros » Mon Sep 10, 2018 6:17 pm

dunmunro wrote:
Mon Sep 10, 2018 5:44 pm

at 1640fps SV (23000yds), the projectile will lose about 150fps in penetration. 1500fps and .035sec fuze delay = ~53ft of travel and that's assuming no further obstruction. Yes, longer delay might occur but so might a shorter delay.
... Bismarck never fired against Rodney from 23000yards. First Bismarck salvo (4x380mm shells from Anton and Bruno) was fired from probably 21.500yards at 8:49 or 8:50, and the 3rd salvo (the only straddle obtained against Rodney - causing splinter damage) was fired from a probable distance of 20000yards (because the time was 8:52, and at 8:53 we have a radar range from KGV of 21500yards, while Rodney was leading by about 1 mile)

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Re: What if Bismarck hit Rodney early on?

Post by dunmunro » Mon Sep 10, 2018 6:19 pm

Dave Saxton wrote:
Mon Sep 10, 2018 5:52 pm
dunmunro wrote:
Mon Sep 10, 2018 5:44 pm
Dave Saxton wrote:
Mon Sep 10, 2018 3:55 pm

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.
According to Okun D steel is 89000 psi tensile at 22% elongation. Thinner STS plates had lower ratings, probably about 110k according to Okun:

http://navweaps.com/index_nathan/metalprpsept2009.php

I have primary documents on D steel and Nathan is incorrect on this one.
I think your numbers might be for weldable D1 steel.

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Re: What if Bismarck hit Rodney early on?

Post by dunmunro » Mon Sep 10, 2018 6:31 pm

alecsandros wrote:
Mon Sep 10, 2018 6:17 pm
dunmunro wrote:
Mon Sep 10, 2018 5:44 pm

at 1640fps SV (23000yds), the projectile will lose about 150fps in penetration. 1500fps and .035sec fuze delay = ~53ft of travel and that's assuming no further obstruction. Yes, longer delay might occur but so might a shorter delay.
... Bismarck never fired against Rodney from 23000yards. First Bismarck salvo (4x380mm shells from Anton and Bruno) was fired from probably 21.500yards at 8:49 or 8:50, and the 3rd salvo (the only straddle obtained against Rodney - causing splinter damage) was fired from a probable distance of 20000yards (because the time was 8:52, and at 8:53 we have a radar range from KGV of 21500yards, while Rodney was leading by about 1 mile)
KGV and Rodney were in a line abreast with Rodney about 2000 yds north of KGV with Rodney bearing 10degs from KGV (Rodney's bow is about 350 yds ahead of KGV's )

OK so lets choose 20k yds. The SV increases to 1734fps but the AoF is now only 14.24 degrees. What is gained in SV is lost in AoF, because we need the 38cm shell to descend enough to threaten the magazine.

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Re: What if Bismarck hit Rodney early on?

Post by alecsandros » Mon Sep 10, 2018 6:41 pm

I have tried to draw 2 trajectories of 380mm shots: 1 for a 55feet trajectory at approx 20deg fall, the second for a 70feet trajectory at approx 15deg fall. Both end up in the forward main magazine...
dunmunro wrote:
Mon Sep 10, 2018 6:31 pm
OK so lets choose 20k yds. The SV increases to 1734fps but the AoF is now only 14.24 degrees. What is gained in SV is lost in AoF, because we need the 38cm shell to descend enough to threaten the magazine.
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Re: What if Bismarck hit Rodney early on?

Post by dunmunro » Mon Sep 10, 2018 7:02 pm

alecsandros wrote:
Mon Sep 10, 2018 6:41 pm
I have tried to draw 2 trajectories of 380mm shots: 1 for a 55feet trajectory at approx 20deg fall, the second for a 70feet trajectory at approx 15deg fall. Both end up in the forward main magazine...

uQldjFr.jpg
dunmunro wrote:
Mon Sep 10, 2018 6:31 pm
OK so lets choose 20k yds. The SV increases to 1734fps but the AoF is now only 14.24 degrees. What is gained in SV is lost in AoF, because we need the 38cm shell to descend enough to threaten the magazine.
For reference Rodney is 710ft long. Your line drawing in blue shows a total travel of 132ft...

It also shows the shell going through the armoured bulkhead. The bulkhead was 12in thick for two decks, and then reduces in thickness gradually but it is worked all the way to the bottom. Also as I explained Rodney and Nelson had an extension to the armoured deck forward running from the bottom of the 12in portion of the armoured bulkhead.
Last edited by dunmunro on Mon Sep 10, 2018 7:18 pm, edited 1 time in total.

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Re: What if Bismarck hit Rodney early on?

Post by alecsandros » Mon Sep 10, 2018 7:08 pm

dunmunro wrote:
Mon Sep 10, 2018 7:02 pm
For reference Rodney is 710ft long. Your line drawing in blue shows a total travel of 132ft...
It also show the shell going through the armoured bulkhead. The bulkhead was 12in thick for two decks, and then reduces in thickness gradually but it is worked all the way to the bottom. Also as I explained Rodney and Nelson had an extension to the armoured deck forward running from the bottom of the 12in portion of the armoured bulkhead.
12" armored bulkhead while the shell was rated at 17" armor penetration (vertical) from 18000meters (20.000yards).
Also, notice the pink trajectory going through the 6" portion of the bulkhead :wink:

I have re-drawn the trajectories, above.

P.S.: According to GKDOS100 calculus, the 380mm/L52 with APC shot could perforate 12" solid plate (of Krupp-post-1930 armor , at least 5% stronger then 1920s vintage armor) , at 30deg compounded obliquity (total obliquity) by using 493m/s velocity for intact perforation, or 458m/s for projectile broken after impact.
Last edited by alecsandros on Mon Sep 10, 2018 7:34 pm, edited 3 times in total.

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Re: What if Bismarck hit Rodney early on?

Post by Dave Saxton » Mon Sep 10, 2018 7:14 pm

dunmunro wrote:
Mon Sep 10, 2018 6:19 pm

I think your numbers might be for weldable D1 steel.
No, but I have the numbers for DW also.
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 7:32 pm

alecsandros wrote:
Mon Sep 10, 2018 7:08 pm
dunmunro wrote:
Mon Sep 10, 2018 7:02 pm
For reference Rodney is 710ft long. Your line drawing in blue shows a total travel of 132ft...
It also show the shell going through the armoured bulkhead. The bulkhead was 12in thick for two decks, and then reduces in thickness gradually but it is worked all the way to the bottom. Also as I explained Rodney and Nelson had an extension to the armoured deck forward running from the bottom of the 12in portion of the armoured bulkhead.
12" armored bulkhead while the shell was rated at 17" armor penetration (vertical) from 18000meters (20.000yards).
Also, notice the pink trajectory going through the 6" portion of the bulkhead :wink:

I have re-drawn the trajectories, above.

P.S.: According to GKDOS100 calculus, the 380mm/L52 with APC shot could perforate 12" solid plate (of Krupp-post-1930 armor , at least 5% stronger then 1920s vintage armor) , at 30deg compounded obliquity (total obliquity) by using 493m/s velocity for intact perforation, or 458m/s for projectile broken after impact.
The blue line shows a travel of 76ft... The shell has to penetrate the hull plate for a ~10% velocity loss and then a 12in bulkhead for another huge loss of velocity. The pink line is 93ft long and the bulkhead it passes through is 8in thick. (R&R British Battleships page 123)

The RN did a post war study of Nelson class armour and concluded that it was essentially identical to WW2 armour. See ADM 281-40.

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Re: What if Bismarck hit Rodney early on?

Post by alecsandros » Mon Sep 10, 2018 7:36 pm

dunmunro wrote:
Mon Sep 10, 2018 7:32 pm

The blue line shows a travel of 76ft... The shell has to penetrate the hull plate for a ~10% velocity loss and then a 12in bulkhead for another huge loss of velocity. The pink line is 93ft long and the bulkhead it passes through is 8in thick. (R&R British Battleships page 123)
Where did you get 10% velocity loss when passing through 37mm of contruction steel ?

As known, 12" (305mm) and 8" (203mm) respectively is easily perforatable by 380mm shot from 18000meters. Shot has velocity of ~525m/s, enough to perforate ~440mm (17") of solid plate of better quality then the 1920s armor.
see http://www.kbismarck.com/38cm.html

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Re: What if Bismarck hit Rodney early on?

Post by alecsandros » Mon Sep 10, 2018 7:44 pm

dunmunro wrote:
Mon Sep 10, 2018 7:32 pm
The pink line is 93ft long and the bulkhead it passes through is 8in thick. (R&R British Battleships page 123)
updated - above.
The RN did a post war study of Nelson class armour and concluded that it was essentially identical to WW2 armour. See ADM 281-40.
in some tests yes,
in others, it was worse then KGV type of cemented armor by up to 10%.
Friedman, in "The British Battleship 1906-1946", writes (pg 371): "when HMS Rodney was scrapped, N.C.D. compared her (1923) armor with later types. The testers concluded that modern armour, such as that on HMS Vanguard, was only slightly better than the armor in Rodney, but it was more consistently effective "

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