Alaska Class vs Dunkquerke Class

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paul.mercer
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Re: Alaska Class vs Dunkquerke Class

Postby paul.mercer » Wed Mar 29, 2017 3:16 pm

Thanks for that,
But how would another country or navy know what the immune zones on that particular ship or whether their shells are powerful enough to penetrate? After all, the French ship - as was Bismarck were both fairly new and even in the case of Rodney (or any ship in any navy) it is hardly likely that they are going to broadcast to the world which areas and at which range is the best for a rival ship to engage them! All they would have to go on are tests on their own armour or on old ships which may or may not be applicable bearing in mind the fairly rapid development of shells and armour plating. I know we can discuss these matters now in the forums because most of the tests and their findings have been published, but they surely would have been top secret before the war.

Iranon
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Re: Alaska Class vs Dunkquerke Class

Postby Iranon » Wed Mar 29, 2017 11:16 pm

There would be a lot of guesswork involved. German fighting recommendations Bismarck vs Nelson:
12-16km for decisive battle, maintain an angle of at least 30°. Effective AP fire possible against turrets and barbettes out to 24km, but own deck penetration may become a factor past 23km; no corresponding weakness for Nelson. It should be considered that Nelson has large unprotected areas highly vulnerable to HE shells.

A 1942 British Armour Efficiency Diagram assumed better protection for Nelson against Tirpitz at 12-16km (immunity between 16000 and 31000yd for Nelson, between 16800 and 21000yd for Tirpitz; stating 13" belt and 3.2" deck for Tirpitz; no mention of inner layers).
At an angle of 120°in British parlance (the above 30° in German parlance), Nelson's belt penetrable down from 12800yd, Tirpitz' belt down from 14000yd.

I'm afraid I don't have comparable information about a Alaska/Dunquerke matchup and would be surprised if such a primary source existed.

paul.mercer
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Re: Alaska Class vs Dunkquerke Class

Postby paul.mercer » Fri Mar 31, 2017 9:31 am

Thanks again for the info.
I suppose it would be rather unfortunate if both ships had the same ideal optimum firing range!
Even so, at whatever range they hit 15" or 16" shells are going to hurt even if they don't penetrate the armoured decks, they could still take out other vital parts such as rangefinders, control systems and even gun barrels. One thing is for sure, I wouldn't like to be on the receiving end at any range!

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Re: Alaska Class vs Dunkquerke Class

Postby Iranon » Sun Apr 02, 2017 12:04 am

Not quite the case here. In C.B. 04039 + Addendum 2(1942), relatively long ranges were recommended for an advantage in armour penetration (it is noted that other considerations may be as important): Between 22000 and 26000yd, Nelson immune while Tirpitz vulnerable to 16" deck hits. Between 22000 and 31000yd, KGV immune while Tirpitz vulnerable to 14" deck hits.

Some interestings details:
British WW1-era 15" outclassing the more modern guns (16" having slightly better belt penetration at high obliquities but much worse deck penetration). Relative protection of Queen Elizabeth class and Tirpitz held almost equal (slight British disadvantage for the belt, slight advantage for deck). Generally, only considering one layer for Tirpitz and no mention of possible complications (yaw, decapping, fusing... British shells may explode before even reaching the armour deck if the fuze works correctly). Armour immunity diagram of QE and loss of Hood through a supposed hit into a main magazine also appear difficult to reconcile.

So even when clear capability assessments and handling instructions are available, this may raise as many questions as it answers. While being shot at with main battery shells is probably not the nicest thing to happen to one's ship, immunity is explicitly given for embedded vitals - propulsion plant (hits may deprive one of the ability to disengage) and magazines (hits could be catastrophic). Accumulating damage elsewhere is something both RN and KM took into consideration. British AP shells carried a large explosive charge and other British documents discuss relying on incremental damage while prioritising own safety; they just thought they had a better option against Tirpitz because they considered her deck armour weak. German ships carried a significant number of HE shells intended for anti-ship use at distances where enemy vitals were not expected to be vulnerable.

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Re: Alaska Class vs Dunkquerke Class

Postby Thorsten Wahl » Thu Apr 06, 2017 9:31 am

Between 22000 and 31000yd, KGV immune while Tirpitz vulnerable to 14" deck hits.

This recommendation was overtaken past 1945/46 when the protective value of the german horizontal protection(50 mm + 80 mm) was evaluated with about 6 ".

No british naval gun/shell in service at this time could perforate (projectile through armour) this protection at ranges below 30 kyard. The observed new type of failure of penetration was referred as "topple".

Nevertheless the complete ship above the main armored deck has almost no imunity against BB main caliber shells.

So technically speaking, at ranges when belt penetrations became impossible, the AON of british and american ships offer one deck less destructable area, until a shell could defeat the complete horizontal protection scheme.
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Re: Alaska Class vs Dunkquerke Class

Postby Byron Angel » Tue May 09, 2017 9:44 pm

I might be wrong on this, but IIRC BB59's shoot against JB was effectively air spotted indirect fire against an target invisible to BB59 because of smoke screens and smoke from nearby dockyards fires.

Dave can probably deal with the following:
Given the position of JB in a pierside position, surrounded by various cranes, buildings and other structures, I wonder how useful BB59's FC radar would have been if it had been working.

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Re: Alaska Class vs Dunkquerke Class

Postby Dave Saxton » Wed May 10, 2017 1:41 am

Byron Angel wrote:I might be wrong on this, but IIRC BB59's shoot against JB was effectively air spotted indirect fire against an target invisible to BB59 because of smoke screens and smoke from nearby dockyards fires.

Dave can probably deal with the following:
Given the position of JB in a pierside position, surrounded by various cranes, buildings and other structures, I wonder how useful BB59's FC radar would have been if it had been working.

Byron


The MK3 or FC radar had a resolution for range of 300 meters and a resolution for bearing (while lobe switching) of 14 degrees. Indication was by A-scope. It is doubtful that there would have been sufficient ability to distinguish from among all those different targets.

Range accuracy would have been about 60 yards but what exact target it was ranging would have been ambiguous.

Target resolution in this particular case would be very difficult for any radar in my opinion. Even a modern radar. Substituting a MK8 for the MK3 it would still be difficult to resolve the target from the surrounding clutter despite using a B -scope. The resolution for range in the MK8 case will be about 60 meters and the resolution for bearing will be two degrees. Even MK13 or SCR584, or MK35 would probably not be able to resolve the target in this case.
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paul.mercer
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Re: Alaska Class vs Dunkquerke Class

Postby paul.mercer » Thu May 11, 2017 9:03 pm

Iranon wrote:In case of a large speed advantage, the faster side can dictate the range.
In the case of Bismarck vs. Rodney, this gives Bismarck several options, such as

a) Close the range to a point where Bismarck's vitals are immune but Rodney's aren't, accepting varying and unclear conditions in the meantime.

b) Keep a moderate distance where vitals are immune on both sides, pepper Rodney with HE shells taking advantage of the large unprotected areas

c) Keep a long-ish distance in the hopes that an assumed advantage in own fire control is most telling there.

None of these is without problems, own doctrine based on incomplete information may not be ideal... but the ability to choose must count for something.



For the matchup at hand, if the Americans are confident in their ability to hit at extreme range (or at least willing to fire a large number of shots and disengage if unsuccessful) and the French aren't, there is little the latter can do.


I have to say that closing the range with a ship mounting 9x16" guns would be a very risky option even for Bismarck!

Iranon
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Re: Alaska Class vs Dunkquerke Class

Postby Iranon » Wed Oct 25, 2017 12:26 am

I've recently had a look at various gun range/velocity tables comparing impact energies, which turned out to be quite interesting.



Alaska's guns are sometimes described as powerful for their calibre, but Dunkerque's are something else. Impact energy at usual battle ranges is about 50% higher, more than any naval 14", and the US empirical formula credits it with belt penetration comparable to the German 38cm at 0° obliquity. Not entirely unexpected, smaller shell and shallower angle mean there's less armour in the way.
The shells also carry a rather large bursting charge of 20.3kg (7.9kg for American 12" AP, 18.55kg for American 16" superheavies).

The impressive characteristics on paper aren't everything though. Very high muzzle velocity exacerbated the dispersion problems arising from the close-set quad mounts (169cm between axes of a pair).
Long (5 calibre lengths) and heavy shells retain energy well downrange, but are subject to excessive bending forces at oblique angles; together with the high percentage of explosive filler this should make them relatively fragile. American face-hardened armour focused more than others on damaging projectiles, rather than just resisting penetration.
Neither ammo supply nor RPC turned out to be entirely satisfactory.



The impact energies of Rodney's 16" and Bismarck's 38cm shells are very close at ranges between 10 and 20km, and again this should favour the smaller, higher-velocity shell when it comes to belt penetration.
So while closing may be a risky proposition for Bismarck, it may be even less comfortable for Rodney. Again, the question is whether the KM wants to take that risk... their fighting recommendations for decisive battle read as quite aggressive, but they rarely wanted to push for one.


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