Plan Z

[Plain Old Dave]

Given Tirpitz outranges Massachusetts by approx 3,000yards,

That's almost exactly how much MASSACHUSETTS outranges Tirpitz.

more likely to simple bounce off harmlessly.

You must have slept through physics class. That's a 2700 pound chunk of hardened tool steel for an AP round. With a muzzle velocity of 2500 fps. "Hot knife through butter" is the metaphor you're looking for.

[Terry Duncan]

Duplicate post removed.

[Terry Duncan]

Given Tirpitz outranges Massachusetts by approx 3,000yards,

That's almost exactly how much MASSACHUSETTS outranges Tirpitz.

I really must ask where you are getting your figures from, as it isn't Navweaps, Wiki, Garzke & Dulin etc, as they are all remarkably consistent on the ranges the German 15" and US 16" Mk6 could manage. This would be 36,900 yards for the 16" and 39,589 yards - 39,940 yards for the 15" which means Tirpitz has the advantage in range, not Massachusetts.

https://en.wikipedia.org/wiki/South_Dak ... hip_(1939)
http://www.navweaps.com/Weapons/WNUS_16-45_mk6.php
https://en.wikipedia.org/wiki/Bismarck-class_battleship
http://www.navweaps.com/Weapons/WNGER_15-52_skc34.php

We have all the data, so there really is no mystery around these guns performances.

more likely to simply bounce off harmlessly.

You must have slept through physics class. That's a 2700 pound chunk of hardened tool steel for an AP round. With a muzzle velocity of 2500 fps. "Hot knife through butter" is the metaphor you're looking for.

It is a large mass of metal moving at high speed, and penetration varies wildly depending on the angle the armour is struck at, with many angles auto-rejecting the shells, which is the basis for the highly sloped glacis armour on modern tanks. You seem somewhat too invested in myths to be suggesting that I or anyone else slept during physics classes, given your own knowledge seems to be somewhat lacking. If you follow the link to the US 16" gun at Navweaps it even has a nice little penetration table for the 2,700lbs shell;

http://www.navweaps.com/Weapons/WNGER_15-52_skc34.php

Now, if 'hot knife through butter' is the phrase I am looking for, please explain why the gun can only manage to penetrate between 1.87"/28mm and 3.03"/77mm of deck armour at ranges 10,000 - 15,000 yards? I will tell you, it is because the armour is simply too thick to be penetrated at the angle of impact these ranges allow the shell to do anything but bounce harmlessly off the armour. We could start looking into actually where most shells will strike a target at certain ranges, but as this really will not help you, I will leave it up to you if you really want to keep digging that particular hole.

[JAK]

Hi,

Is there any meaningful difference between the 15" and 16" guns? As the seem to be such powerful weapons it makes me think that other factors would be more deciding in a battle. Like for example pure luck in getting the first hit etc.

[Terry Duncan]

Hi,

Is there any meaningful difference between the 15" and 16" guns? As the seem to be such powerful weapons it makes me think that other factors would be more deciding in a battle. Like for example pure luck in getting the first hit etc.

Hi. That is a very good question. The major factor would be in shell weight and the size of the burster charge in the shell itself. The British 15" had a very large burster charge (about the same as the WWII US 16" iirc), so was extremely destructive when it did burst inside the armour. In the case listed, Tirpitz vs Massachusetts, the US ship has by far the heavier broadside and more destructive shells, 24,300lbs vs 14,400lbs, and at most likely ranges a RoF from both ships would be around 1rpm. This is where it gets complicated though, the Tirpitz has a far higher shell velocity, 2690fps vs 2300fps, and as such has a flatter shell trajectory and shorter flight time, making it slightly easier to hit a moving target as a base chance before the accuracy of fire control is taken into account. The effectiveness of the fire control is open to debate, results in war tended to show most guns performed at least ok, and it is difficult to compare them because luck does play a part too. With a slightly higher RoF for the Tirpitz at closer ranges (where spotting the fall of shot takes less time because flight time decreases), it is likely she would hit more often, and with a 3,000 yard range advantage quite likely to hit first as she will start the process of targeting and adjustment earlier, but with far less effect than the US shells when they hit back. Where the shells hit would be the most critical part, and that is well beyond anyones control at all but very close range, so again luck plays a massive role here - look at Tiger and Lion during WWI, where both ships took a lot of hits, Tiger taking 17 hits at Jutland in the Run to the South and notably took little damage from any, whilst Queen Mary took 4 hits for certain and was lost in an explosion.

There are also two other factors that could be considered. The rather unusual number of shells fired by Bismarck that were duds could indicate either pure bad luck or possibly a shell defect in manufacture? This may not have effected Tirpitz, it is hard to say as she was never tested. Then we come to the US 'super-heavy' shells, where the shell itself was somewhat longer than previous shells, and because of this, when the shell strikes at a highly oblique angle it causes the shell to bend as the nose impacts the armour and very slightly slows compared to the rear of the shell. Whilst this sounds really minimal, it causes the shell to either bounce off entirely or to distort so much that it fails to explode. It is known as a whiplash effect or 'hammer action' as it is rather like hitting the head of a long nail somewhat off center causing it to bend rather than penetrate the wood as intended. The British had rejected such a shell design prior to WWII as they felt the advantages offered were outweighed by the disadvantages, whilst the US decided to take the risk as they felt the opposite way. As it is impossible to ensure the enemy is presented at a nice shell friendly angle, the British may have proven to be correct in anything but a line of battle type engagement where ships tend to be far closer to the optimal impact angles as the lines face off.

Hope this explains things ok, but as you said, luck is the one major factor that is both needed and unpredictable - other than in alt history stories/fantasies.

[Polar bear]

hi, Terry,

.. and that was a very good reply.

greetings, the pb

[JAK]

Agreed! Thanks for a thorough answer!

[Terry Duncan]

Thank you to both of you, I am never sure if I prattle on a lot in a way that is mostly only understandable to someone who already knows what I am referring to. Unlike in many alternate histories hitting the enemy, let alone hitting them in a critical location, is far from certain at most likely battle ranges. At close ranges, it becomes very different, sees the final Bismarck action or the infamous night action at Cape Matapan for examples of just how quickly modern warships were able to dispose of enemies, especially with regards to disabling turrets and critical systems.

[Terry Duncan]

Plain Old Dave,

I really must ask where you are getting your figures from, as it isn't Navweaps, Wiki, Garzke & Dulin etc, as they are all remarkably consistent on the ranges the German 15" and US 16" Mk6 could manage. This would be 36,900 yards for the 16" and 39,589 yards - 39,940 yards for the 15" which means Tirpitz has the advantage in range, not Massachusetts.

I presume you are not intending to answer this or absent at present, which if it is the former, is somewhat sad as it would be interesting to see other data and sources. I would stake a lot of money to say your figures are incorrect, but I would still be very interested in reading the sources?

[Thoddy]

postet in wrong thread removed

[Thoddy]

double post sorry

[Thoddy]

The British 15" had a very large burster charge (about the same as the WWII US 16" iirc)...the US ship has ... more destructive shells

-burster of the 2700 lb (1225 kg) US-Shell 40.9 lbs. (18.55 kg)
-burster of the german 800 kg Psgr (18.8 kg)

energy content of the german burster is about 20 % higher than the US burster.

The main advantage the US Shell possess when fired from the 16" L/45 gun(IV 2300 fs) is its greater mass and it's somewhat better impact angle against horizontal protection.

Nevertheless a internal detonation of the german shell would also destroy a complete compartment. A restoring of lost capabilities require shipyard capacities. This was tested fullsize.

From the ballistic quality of the german gun/turret one can expect about 15,5 percent hit probability of the german gun at 25 km distance if MPI is on target. Tirpitz carried out a one hour shooting excercise(not continous but several attack figures) in autumn 1941 at this distance, wich yielded about 8 hits(AFAIK) at the moving target ship. A two impacts salvo spread at this distance looks like that

Hessen near miss.jpg

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http://www.navweaps.com/Weapons/WNGER_15-52_skc34.php
We have all the data, so there really is no mystery around these guns performances.

the data at navweaps partly underestimate the performance of the german armor piercing shell.
One should take the data KBismarck provides, as this is based on the original german fire-effect-tables.
http://www.kbismarck.com/38cm.html

The penetration performance of the US Shell published at Navweaps.com was based on a completely calculated performance using Thompson F-Formula (Origin Ordnance Pamphlet No 653
Armor pentration curves (revised) January 1942).
This formula overestimates angular performance with the error becoming higher at high obliquity
and underestimates shell performance at low obliquity.

Supp 6 910 calculated angular performance.png

In addition one should consider the better ballistic capabilities of german armor when compared to US armor of the same thickness.

[Terry Duncan]

The British 15" had a very large burster charge (about the same as the WWII US 16" iirc)...the US ship has ... more destructive shells

-burster of the 2700 lb (1225 kg) US-Shell 40.9 lbs. (18.55 kg)
-burster of the german 800 kg Psgr (18.8 kg)

energy content of the german burster is about 20 % higher than the US burster.

I agree, although the US shell is throwing 50% more mass around as shrapnel once inside the ship, so rather balances out the initial destructivness of the burster with a greater mass being thrown around inside the ship after bursting.

The main advantage the US Shell possess when fired from the 16" L/45 gun(IV 2300 fs) is its greater mass and it's somewhat better impact angle against horizontal protection.

Yes, I quite agree.

Nevertheless a internal detonation of the german shell would also destroy a complete compartment. A restoring of lost capabilities require shipyard capacities. This was tested fullsize.

Almost all shells will destroy the compartment that they explode inside, the critical part is if that compartment is in the ships vital areas or integral to the water tight integrity of the hull. The extension to this is where the shell fragments travel to, as a red hot fragment can pass on from where the shell bursts and end up inside vital areas, as in the hit on Malaya (iirc) at Jutland that saw a fragment end up in the 6" magazine!

From the ballistic quality of the german gun/turret one can expect about 15,5 percent hit probability of the german gun at 25 km distance if MPI is on target.

I am not too sure I follow this. 15.5% hit probability at 25km is at least 3 times, and more likely 5 times anything achieved in action, where 5% at half such a range was still considered good shooting in WWII. Against a stationary target maybe, but not in battle, no ship came close to this except in very one sided encounters at short range like Matapan where anywhere up to 80% accuracy was achieved.

Tirpitz carried out a one hour shooting excercise(not continous but several attack figures) in autumn 1941 at this distance, wich yielded about 8 hits(AFAIK) at the moving target ship. A two impacts salvo spread at this distance looks like that

Only two hits were ever achieved at 25km or even close, so I am sceptical on claims of 15.5% hits. 1.55% might be more likely?

the data at navweaps partly underestimate the performance of the german armor piercing shell.
One should take the data KBismarck provides, as this is based on the original german fire-effect-tables.
http://www.kbismarck.com/38cm.html

Navweaps is fairly accurate, which served my purposes as if anything boosting the capabilities of Tirpitz only makes the equation run more against Massachussetts. It looks like the KMBismarck site uses data for a gun in 'new' condition, with optimum figures, which of course tend to run down slightly after a few rounds have been fired. Taking barrel wear into account really complicates things far too much for a basic comparison where such details are unspecified.

The penetration performance of the US Shell published at Navweaps.com was based on a completely calculated performance using Thompson F-Formula (Origin Ordnance Pamphlet No 653
Armor pentration curves (revised) January 1942).
This formula overestimates angular performance with the error becoming higher at high obliquity
and underestimates shell performance at low obliquity.
Supp 6 910 calculated angular performance.png

The problem with the US shells at high obliquity is that pointed out by the RN when the idea of longer shells was mooted for them, the shell will often just distort and fail entirely, or riccochet off harmlessly, which makes overall performace at such angles hard to judge, as whilst one shell may achive a spectacular result by penetrating armour intact, it is possible dozens may strike and do nothing at all.

In addition one should consider the better ballistic capabilities of german armor when compared to US armor of the same thickness.

I would agree that the German armour is generally better than US armour of an equal thickness in WWII, but there are many differing claims as to how much better it actually was, though I would suspect it was within 10% - 20% more efffective as an off the cuff figure. It is also worth looking at the article Nathun Oakun wrote (I cannot recall the title, and do not know if it is still available sadly) about how the 'X% more effective' claims may be judged, as claims are not always worded clearly.

[Pips]

Just a comment on the 'range' issue of both the Tirpitz (39,589 yds) v Massachusetts (36,900 yds).

Isn't the argument moot? The longest hit achieved by a moving battleship in WWII was by Warspite and Scharnhorst. Warspite (equipped with old 15" guns) hit the Italian battleship Giulio Cesare 9 July 1940 near Punta Stilo at a range of approximately 24 km (26,000 yds). Scharnhorst (equipped with smallish 11' guns) hit the carrier Glorious at approximately the same distance 8 June 1940.

That being the case shouldn't the argument be based on a 'head-to-head' at more realistic battle ranges?

[Paul Lakowski]

Just a comment on the 'range' issue of both the Tirpitz (39,589 yds) v Massachusetts (36,900 yds).

Isn't the argument moot? The longest hit achieved by a moving battleship in WWII was by Warspite and Scharnhorst. Warspite (equipped with old 15" guns) hit the Italian battleship Giulio Cesare 9 July 1940 near Punta Stilo at a range of approximately 24 km (26,000 yds). Scharnhorst (equipped with smallish 11' guns) hit the carrier Glorious at approximately the same distance 8 June 1940.

That being the case shouldn't the argument be based on a 'head-to-head' at more realistic battle ranges?

That is exactly the points, since shooting at anything that is shooting back is infinitely harder than a inert target, moving or not.