British guns at DS

[Francis Marliere]

Gentlemen,

It is usually said that VADM Holland tried to close the range between Bismarck and his ships because he knew that German 38 cm could easily defeat Hood's armor. However, I found very few data upon the capacity of British guns to penetrate Bismarck armor. I guess that British guns can only penetrate at modertae range because of 15"/42 low velocity and 14"/45 light shell, but I would like to have hard facts. Could your please communicate the data ?

Best regards,

Francis Marliere

[alecsandros]

I think it was more a matter of standard tactics. A 1935 British document mentions "usual ranges of battleship engagements" at about 16.000y.
This is consistent with most of the battles in which British battleships were involved in WW2.

I doubt Adm. Holland had the technical charts that are today floating on the internet, both in terms of German armor schemes and German 15"/L52 guns.

So my impression is that he acted according to standard British naval doctrine of the time...

[alecsandros]

As for Hood/KGV/Bismarck relative immunity zones, the discussion is quite complicated.

In a simple approach, with all ships at perpendicular angles to each other's guns (perfectly parallel courses), we would have:

Hood's main belt (305mm - 1920s quality) -- vulnerable at 30km against 380mm shells
KGV's main belt (384mm British post-1930 CA)-- vulnerable to 21km against 380mm shells

Bismarck's main belt (320mm - KC n/A)-- vulnerable at 25km against 381mm shells
Bismarck's main belt (320mm - KC n/A)-- vulnerable at ~ 25km against 356mm shells

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However, in a real engagement, the "perfectly parallel course" would very rarely be attained, with ships being slightly "ahead" or "behind" the enemy, and rolling/pitching according to manouvres and sea condition. This corresponds to a certain "obliquity" between the shells trajectory and the normal of the armored plate. This would make the shell's perforation more difficult.

German L4.4 380mm shells were greatly improved for oblique penetration, and their performance was clearly better than British 381mm and 356mm during oblique penetrations.

Moreover, Bismarck's design featured a second, internal, sloped deck, which could opose possible shells that would manage to break through the main armored belt.

----------

A discussion about relative deck perforations as a function of shell and range is much more complicated. My impression, though, is that the lower m-v of the British 381mm gun, along with the short and robust shell could prove more deadly against Bismarck's decks than against Bismarck's main belt(s).

Just some thoughts...
Cheers,
Alex

[Thorsten Wahl]

plain translation from the "Unterlagen zu Bestimmung der Hauptkampfentfernung"

"... It must therefore be sought, if at all possible, to incorporate also the horizontal plating in the entire system of the armor. This can be achieved, that is kept at least on the main combat distances, the effects of the destruction of vital parts of the ship. The strongest armored deck is like to lay so far as deep as possible and pull down with as flat slope to the lower edge belt, but, in contrast to earlier to make now so strong that bullets that hit the belt with a considerable excess of speed by beating and scarp may not pentrate but either get broken or be dismissed..."

As vital parts of the ships were considered machinery and magazines. The protection scheme doesnt make the ship unvulnerable, it requires, that large parts of the ship have to be badly damaged.

The mechanism of decapping wich enables the armor scheme to do so, requieres less armor, wich deemed to be necessary by a plain calculation of penetration.
As a consequence of decapping the head shape changes in a unfavorable manner, so a pentration requires more energy at highly oblique impacts.
mass of the projectile at the second impact is also reduced.
and deflection of the projectile is also more likely depending on the head shape

Additional due to the change of the flightcurve compared to orientation of the rotation axis of the projectile further effects may occur(yaw), the projectile wich digs in a armor plate creates a hole wich is increased in diameter, so a given pentration channel requires more energy as a optimal pentration.

the same effects can also be expected by a pentration through the upper belt and the upper deck. In these cases also premature fuzing came into play, whilst the effects of deceleration of the attacking projectile were reduced.

According to US ballistic experts the the gain in effective thickness to the total thickness of a spaced array can be expected up to 30-50% compared to the thicknes of a single plate.
see here
Title : Spaced Armor
Descriptive Note : Experimental rept
Corporate Author : WATERTOWN ARSENAL LABS MA
Personal Author(s) : Hurlich, A.
http://handle.dtic.mil/100.2/ADA954865

[lwd]

...According to US ballistic experts the the gain in effective thickness to the total thickness of a spaced array can be expected up to 30-50% compared to the thicknes of a single plate.
see here
Title : Spaced Armor
Descriptive Note : Experimental rept
Corporate Author : WATERTOWN ARSENAL LABS MA
Personal Author(s) : Hurlich, A.
http://handle.dtic.mil/100.2/ADA954865

It should be noted that said document also illustrates cases where the spaced array is inferior to a single plate.

[Dave Saxton]

^^The Bismarck's armouring scheme and material properties meets the requirements set forth for providing protection exceeding that of a single plate.

[Karl Heidenreich]

Dave:

^^The Bismarck's armouring scheme and material properties meets the requirements set forth for providing protection exceeding that of a single plate

This point has been addressed in many threads before, specially a month or two ago and the conclusions have been pretty clear. To "forget" about it now is not a good way to conduct discussions: if a point is clear and proved, then the discussion move on to the next point in order to achieve more information and comprehension of what we are discussing.

Both: Thorsten and Dave have bring forth arguments strong enough to shed light that the space arrayed armor of Bismarck was perfectly able to withstand the punishment of her contemporary adversaries.

[RF]

And presumably demonstrated so during Rheinubung.

[lwd]

... Both: Thorsten and Dave have bring forth arguments strong enough to shed light that the space arrayed armor of Bismarck was perfectly able to withstand the punishment of her contemporary adversaries.

Not really. They have made a strong case for that possibity but not for its certainty as you imply. This is especially true if ones defintion of "adversaries" includes those she could have fought as well as those she did.

[dunmunro]

KGV did not use a spaced array yet her belt and decks were immune from the KM 38cm throughout most of the battle simply because she maintained a high target angle and used the weight savings to thicken the armour to its maximum. To consider the efficacy of Bismarck's armour you also have to look at belt depth, deck thickness and the alternative arrangements: For example by using an AoN scheme Bismarck could have had thicker decks, and a thicker and deeper belt, which would probably have provided superior protection from a greater range of threats.

[alecsandros]

KGV did not use a spaced array yet her belt and decks were immune from the KM 38cm throughout most of the battle

Are you sure ?

[dunmunro]

KGV did not use a spaced array yet her belt and decks were immune from the KM 38cm throughout most of the battle

Are you sure ?

Yes, I am quite sure. KGV had splinter protection above and below the MAD and inside the citadel but this is not a spaced array.

[alecsandros]

My impression is that KGV belt was vulnerable to Bismarck's guns below 18km... INdeed, the target angle was unfavorable for most of the battle, but the 38cm shells were quite nicely engineered to function at unfavorable obliquities.

It is a question of probabilities, in my opinion, as to how likely a 38cm shell was to perforate a 38cm CA plate. Clearly, the penetration equation doesn't look to good for the shell, especialy at ranges > 18km.

However, probabilities exist at all the ranges the battle was fought. And at the minimum range between the ships (14km ?), the probability of perforation in a fit state of bursting is quite high...

Cheers,
Alex

[Karl Heidenreich]

Lee:

Not really.

Oh, yes. They both have for a long time now. The fact remains that you don't want to accept it, that's all.

[lwd]

Lee:

Not really.

Oh, yes. They both have for a long time now. The fact remains that you don't want to accept it, that's all.

Then you shouldn't have any trouble pointing out where.