Hood v Vittorio Veneto

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alecsandros
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Re: Hood v Vittorio Veneto

Post by alecsandros » Sat May 14, 2016 6:39 am

... I think it would be a long , long battle with huge ammo consumption and low rate of hits.

The 14" gun is not accurate enough to ensure steady hitting beyond 20-21km, and British BB doctrine required decisive battle at 12 to 18km.

In this matter, the 14" gun has less advantages then the old 15" gun, because the 15" gun had good grouping all the way to 27km. It also had a better rate of fire, and , very interestingly, better perforation of horizontal armor at ranges > 20km.

The drawback was the danger space/hittting space, which would be advantaging the 14"/L45 - but not by a significant margin.

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Alberto Virtuani
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Re: Hood v Vittorio Veneto

Post by Alberto Virtuani » Sat May 14, 2016 8:54 am

Alecsandros wrote: "At 8km, British 14" gun shell retains 605meters/second impact velocity."
Ciao Alec,
therefore same velocity as the Italian 15" at 16 km but 164 kg less mass...... I don't think that with 0° inclination (and even including AoF) the 14" was able to penetrate Littorio belt if the 15" was not....

you wrote: "I know the belt and decapping plate were declined at 12*, making the job of the shell harder. But still, at such high velocities, I think there is some chance (and somebody with better knowledge could quantify it) that the armor piercing cap would start to be dettached from the body of the shell, on perforating the decapping plate (70+10mm), but the immediate deceleration of the cap would not be so powerfull as to ensure total decapping.... "
The belt of Littorio was declined 15° inboard, according to E.Bagnasco (job even harder for the shell).

AFAIK, the principle of the array was that the shell would have hit the main armor plate while de-caped and not yet "free" from the previous plate for all its length, thus in a very unfavorable jaw condition inducing its rupture. To be more precise, the shell would have had a very bad "motion of precession" induced by its tail (still fastly rotating due to gun rifling) being still "trapped" inside the outer armor plate when impacting the main inner one).

The tests confirmed this theory and concluded that it worked against the 15" Italian gun at 16km, thus it should work on the equally fast but much lighter (and fragile, as per Steve post) 14" even under 8 km at 0° inclination.

you wrote: "... I think it would be a long , long battle with huge ammo consumption and low rate of hits."
I do agree, but still, forgetting the RN doctrine and the possible involved admirals "temper", in theory I would have engaged the Littorio's at average to long range (over 20km) as the KGV's had no immunity at shorter distance, Littorio's were less protected horizontally and lacked the speed advantage to close the range.

At very short range (below 12 km), Littorio's are very dangerous "beasts" for any other battleship: they can be damaged of course but it would be difficult to sink them and a single shot of the Italian 15" can be a KO punch.....


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Re: Hood v Vittorio Veneto

Post by alecsandros » Sat May 14, 2016 10:14 am

Alberto Virtuani wrote: therefore same velocity as the Italian 15" at 16 km but 164 kg less mass...... I don't think that with 0° inclination (and even including AoF) the 14" was able to penetrate Littorio belt if the 15" was not....
... Indeed,
but the angle of fall of British 14" at 8km woudl be 6 degrees, while Italian 15" at 16km falls at 10 degrees.
Thus for a perfect parallel ship at 90*, obliquity against plate would be 21 degrees for British shell (15 degrees plate declination and 6 degrees angle of fall) , and 25 degrees for the Italian shell (15 + 10). Strike angles versus normal of plate would be 69 and 65 degrees respectively - so favoring British shell. The aspect of mass should't be ingnored, but velocity and obliquity are more important, IMHO.

AFAIK, the principle of the array was that the shell would have hit the main armor plate while de-caped and not yet "free" from the previous plate for all its length, thus in a very unfavorable jaw condition inducing its rupture. To be more precise, the shell would have had a very bad "motion of precession" induced by its tail (still fastly rotating due to gun rifling) being still "trapped" inside the outer armor plate when impacting the main inner one).
From what I remember, the initial trials done by Pugliese (and confirmed several years later by Rheinmetal Borsig research done in Germany) , showed a need of an interspace between first and second plates in order for the shell to be ineffective.
The interspace distance was 0,6 meters, IIRC, for 2 plates with only air between them. The interspace distance was shrinkable to 0,25meters, provided that the interspace be filled with concrete. However, neither solution was feasible for battlehip design , as the first would "eat" to much of lateral volume, making the ship impossibly cramped, while the second required several thousand tons of extra weight added to the ship - the weight of the concrete poured between the plates.

The situation remained as it was - 0,25meters with no concrete between. Hence, it is debatable over how certain the array was to stop projectiles. Probably that is why they considered it safe outside 16km versus their own main guns (a complete array would be safe to any distance).
I do agree, but still, forgetting the RN doctrine and the possible involved admirals "temper", in theory I would have engaged the Littorio's at average to long range (over 20km) as the KGV's had no immunity at shorter distance, Littorio's were less protected horizontally and lacked the speed advantage to close the range.
It would be good in theory,
In practice the 14" gun did not have good grouping , and it did not have enough punching power to do damage to Littorio beyond 20km. Some hits could cause damage to non-armored parts, and damage/incapacitate (but not destroy) key parts (main con tower, main turrets). But that wouldn't ensure victory, and it would only come as a matter of luck, as the shell dispersion issues of the 14" gun were unpleasant at long range. For instance, it would be hard for a KGV to obtain the same hit as Warspite had (at Calabria from 24.000 meters). Warspite hit Caesare on her 10th salvo (semi-salvo of 4 guns), after 7 minutes of firing, on optical spotting only...

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Re: Hood v Vittorio Veneto

Post by Dave Saxton » Sat May 14, 2016 4:07 pm

Even Fully Capped shells can also shatter if striking face hardened armour obliquely at a high enough velocity. De-capping only lowers the velocity that the shell would shatter, to the point that unless the un- capped shell is going extremely slow it will almost always shatter against face hardened armour. Face hardened armour only needs to be about 20% caliber thickness to shatter most un-capped shells. But capped shells at extremely high velocity will likely shatter against heavy face hardened armour. For example, some of the still capped shells fired at extremely short range against Bismarck are believed to have shattered on impact with the heavy external armour.

There are variations on the theme of using the shatter velocity of shells against them for the vertical armour protection of ships:

One is the German scarp triangle arrangement as explained by Hoyer in his 1943 lecture. The scarp arrangement increased the required velocity the shell needed to obtain penetration of the entire plate arrangement to that that exceeded the shatter velocity of capped shells against the main belt. If the shell is going slow enough to not shatter when striking the external face hardened belt, is not going fast enough to penetrate the complete set of plates.

In the more conventional de-capping approach, the shell is de-capped first before striking the main plate, lowering the critical velocity, so if it then strikes the heavy armour with enough velocity to penetrate the main plate it will being going too fast to avoid shatter.

As originally designed the Italian system followed this principle, but the Italians became concerned that a wide inter-space would become a flooding liability. The redesign eliminated the wide inter-space.

As I recall some of George Elder's comments on Pugleise's engineering papers, and if I understand the commentary correctly (its been several years), the small inter-space was tested as being able to shatter shells even if the "cap rides" the shell, by putting the shell in a "bind" between the outer plate and the main plate when the shell strikes the array obliquely as it changes trajectory slightly while rotating while passing through the outer plate. If the striking angle is normal then the system may not work as designed, but as has been argued in this thread; belts are almost always struck with some obliquity.
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Alberto Virtuani
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Re: Hood v Vittorio Veneto

Post by Alberto Virtuani » Sat May 14, 2016 5:34 pm

@Dave Saxton:
Hi Dave, this is exactely the same way I have understood the Littorio's belt arrangement principle.
you wrote: " If the striking angle is normal then the system may not work as designed, but as has been argued in this thread; belts are almost always struck with some obliquity."
.... and the 15° inboard inclined belt should guarantee that a normal striking angle is never happening, even at inclination 0° and very limited AoF.

Bye, Alberto
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Re: Hood v Vittorio Veneto

Post by paul.mercer » Sat May 14, 2016 7:20 pm

Gentlemen,
From all your comments in this and other topics it seems to me as a non expert observer that the 14" gun and its shell wasn't very good at all when compared against a battleship armed with 15" guns especially as the RN had plenty of experience with the 15", so I wonder why on earth they deviated from the tried and trusted 8x15 set up. I realise the Washington Treaty had something to do with it, but was it because the designers thought that 10x 14" would provide a quick firing 'rain of shells' which would cause a serious amount of damage to the upperworks of an opponent even if they did not penetrate the armoured belts, rather like the Japanese did to the Russian fleet with their 6" guns in the early 1900's ?

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Re: Hood v Vittorio Veneto

Post by alecsandros » Sat May 14, 2016 7:34 pm

@David, Alberto,
Very interesting comments :cool:

@Paul
If I remember right,
Initialy the KGVs were supposed to have 12 main guns in 3 quad turrets. Weight problems caused them to scale down to 10.
For ranges below 20km, my opinion is that the 14" / L45 gun was a better weapon then the older 15"/L42, having better perforation capabilities of vertical armor, and a decent rate of fire and shell grouping. The British expected battles to be fought below 20km, their battle ranges expected in 1935 being 12 to 18km for capital ships engagements. Thus they optimised their ships (guns and armor) to fight at such intervals.

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Re: Hood v Vittorio Veneto

Post by dunmunro » Sat May 14, 2016 7:37 pm

alecsandros wrote:
In practice the 14" gun did not have good grouping , .
What makes you say that? AFAIK the RN was very pleased with the accuracy of the 14/45.

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Re: Hood v Vittorio Veneto

Post by slaterat » Sun May 15, 2016 6:18 am

Another consideration is the small area covered by the VVs main belt. It was only 3.8 m in height with 2.3 above the waterline and only 1.5m below the waterline at deep load. Compared this to the KGV with a main belt of 7.2 m in height with 2.6 above the waterline and 4.6 meters below the waterline. The VV is very vulnerable to low hits and possible magazine detonation. I believe the 14/45 to be the more accurate weapon in this scenario and with a much bigger bursting charge and a better rate of fire. IMHO the odds favor the RN all the way.

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Re: Hood v Vittorio Veneto

Post by alecsandros » Sun May 15, 2016 6:31 am

dunmunro wrote:
alecsandros wrote:
In practice the 14" gun did not have good grouping , .
What makes you say that? AFAIK the RN was very pleased with the accuracy of the 14/45.
... I remember that during gunnery trials, King George Vth exhibited large patterns at long range. I remember 400meters pattern for 4-gun salvo at 20km. That was in 1940.

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Re: Hood v Vittorio Veneto

Post by dunmunro » Sun May 15, 2016 6:51 am

alecsandros wrote:
dunmunro wrote:
alecsandros wrote:
In practice the 14" gun did not have good grouping , .
What makes you say that? AFAIK the RN was very pleased with the accuracy of the 14/45.
... I remember that during gunnery trials, King George Vth exhibited large patterns at long range. I remember 400meters pattern for 4-gun salvo at 20km. That was in 1940.

I haven't found any sources to support your recollection.

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Re: Hood v Vittorio Veneto

Post by alecsandros » Sun May 15, 2016 7:33 am

dunmunro wrote: In practice the 14" gun did not have good grouping ,

What makes you say that? AFAIK the RN was very pleased with the accuracy of the 14/45.
... I remember that during gunnery trials, King George Vth exhibited large patterns at long range. I remember 400meters pattern for 4-gun salvo at 20km. That was in 1940.

I haven't found any sources to support your recollection.[/quote]
Strange, as I remember you were involved in that discussion as well.
The numbers came from an Admiralty file , showing various dispersion numbers for Rodney and King George Vth at various ranges (typical gunnery documents).

I'll try to find them again. I think they are in this forum.

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Re: Hood v Vittorio Veneto

Post by Alberto Virtuani » Sun May 15, 2016 8:04 am

Slaterat wrote: "Another consideration is the small area covered by the VVs main belt. It was only 3.8 m in height with 2.3 above the waterline and only 1.5m below the waterline at deep load......The VV is very vulnerable to low hits and possible magazine detonation"
Hi,
the belt of Littorio's was 4.4 meters high, extending for 2 meters under water at normal battle load (source: E.Bagnasco, pag 56-58 "Littorio class battleships", Italian edition). It was considered enough for Mediterranean seas and for a ship that did not change much her draught due to her limited range (not much fuel could be embarked anyway).
It's a very small belt, but Bismarck's was 4.8 meters only as well, and the 14" hit from PoW was not able to detonate directly within the vitals (albeit flooding them).

The Littorio's magazines could not anyway be directly reached by an UW shell, being behind the belt, high enough to avoid direct penetration by a shell coming from under waterline.
A shell fired at average range should travel some 10 meters under water, pass the complex, rounded, "Pugliese" underwater protection system (in total 94 mm of steel over a path around 8 meters long with voids and liquids in the "worst" conditions of 0°inclination and 90° angle of impact over the cylinder, please see scheme I posted at pag.12 of this very thread) to reach the shell room, still being able to explode and, by splinters effect, to ignite the magazine above.....
The limited belt height is a weakness, but only against a very lucky hit, IMHO, while the belt was not giving immunity to KGV's vitals at average battle distance against the Italian gun, no need of any lucky hit.

Bye, Alberto
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Re: Hood v Vittorio Veneto

Post by Dave Saxton » Sun May 15, 2016 1:29 pm

The Italians found that the danger of shells passing under the shallow belt becomes manifest when the wave forms along the waterline uncover portions of the belt at certain speeds and certain sea conditions. Tank experiments revealed that the dangerous speeds are around 29 knots. Otherwise if the belt remains covered by sea water the danger is minimized.
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: Hood v Vittorio Veneto

Post by Dave Saxton » Sun May 15, 2016 1:51 pm

paul.mercer wrote:Gentlemen,
From all your comments in this and other topics it seems to me as a non expert observer that the 14" gun and its shell wasn't very good at all when compared against a battleship armed with 15" guns especially as the RN had plenty of experience with the 15", so I wonder why on earth they deviated from the tried and trusted 8x15 set up. I realise the Washington Treaty had something to do with it, but was it because the designers thought that 10x 14" would provide a quick firing 'rain of shells' which would cause a serious amount of damage to the upperworks of an opponent even if they did not penetrate the armoured belts, rather like the Japanese did to the Russian fleet with their 6" guns in the early 1900's ?
It really was the treaties mostly. A smaller gun requires less weight to support it: lighter turrets and smaller barbets, less weight committed to traversing and elevating gear, less weight committed to ammunition supply gear, and less weight needed for armour protection. A faster and/or longer range warship can be built on the same displacement.

Another factor for the British is that they already have a battle fleet, albeit aging, armed with 15". If they get potential rivals to build new warships with 14" guns, then it delays the impending obsolescence of their own existing warships. It saves money.
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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