Battleship Vittorio Veneto

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RF
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Re: Battleship Vittorio Veneto

Post by RF » Thu Dec 16, 2010 12:04 pm

Gary wrote:I think The only modern Battleship a VV came close to engaging was Prince of Wales during Operation Halberd.
If the Prince had caught her and engaged her long enough to allow Rodeny to catch up it could have been a repeat of Bismarcks final battle
Maybe, but it also depends on how good the VV gunnery against POW would be.
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Re: Battleship Vittorio Veneto

Post by RobertsonN » Thu Jan 06, 2011 9:18 am

Gentlemen,

The vulnerability of the Littorios to the large German radio controlled bombs would not seem to be in doubt, although Littorio did survive one hit forward of the citadel (Dulin & Garzke, Axis battleships). On the other hand, the class stood up quite well to conventional bombing. D&G list eight hits on the three ships made with AP bombs by high level US bombers. At least four of these were 2000 lb bombs. Three of the hits were on main battery turrets and caused no serious damage. One hit forward led to 2350 tons leakage and another penetrated all armor decks outboard of A turret and remained unexploded in the side protection system. In this case, the bomb was probably disarmed on penetrating the armor (as occurred on Scharnhorst (3 times) and Tirtipz (once)). By way of comparison, Friedman (US battleships) gives the Iowas as immune to 1600 AP bombs below 12200 ft. Does any one know if AP bombs had caps?

With regard to torpedos, members of the class were torpedoed on four occasions, three times underway. Vittorio Veneto survived a hit aft in the same area that doomed the Prince of Wales. Here, the well separated propellors and three rudder arrangement appear to have compared favourably with other contemporary ships. Later German H class designs had three rudders (D&G)). On the other hand, Littorio was sunk by three 18 in torpedoes at Taranto. It was a hit forward that put the bows down. No detailed account is known to me. Was it bad design or was the ship in such a low action state that not enough electric power was available to pump the water out? Is the effect of an underwater exposion in very shallow water as at Taranto greater, with reflection off the bottom, than at normal depths?

While this discussion has concentrated on the unconventional protection systems of these ships, this 1934 design did otherwise adopt many features that were to become common on later ships, especially USN ones: the main battery arrangement, short citadel, bomb deck, triple bottom and no longitudinal subdivision of machinery spaces.

Attempts were also made to reduce some of the weaknesses common to all battleship designs: vulnerability of rudders and secondary armament.

The low level heavily protected conning tower was dispensed with, presumably on the basis that it was useless in the long range engagements envisaged, to be replaced by a higher level CT proof against 8 in shells.

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Re: Battleship Vittorio Veneto

Post by Tiornu » Thu Jan 06, 2011 4:13 pm

The next Italian design after VV was to be built without decapping plates or Pugliese tubes.
Diagrams of the Fritz-X hit to Warspite show little horizontal travel through the hull. She appears to have been struck at a steep angle.

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Re: Battleship Vittorio Veneto

Post by Dave Saxton » Thu Jan 06, 2011 4:28 pm

RobertsonN wrote:....... On the other hand, Littorio was sunk by three 18 in torpedoes at Taranto. It was a hit forward that put the bows down. No detailed account is known to me. Was it bad design or was the ship in such a low action state that not enough electric power was available to pump the water out? Is the effect of an underwater exposion in very shallow water as at Taranto greater, with reflection off the bottom, than at normal depth.
I recall reading that in the case of the Littorio and VV at Taranto, the overall pumping capacity and the overall electric support capacity was grossly insufficient to cope with the flooding.
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Re: Battleship Vittorio Veneto

Post by RobertsonN » Fri Jan 07, 2011 9:37 am

"Tiornu wrote: The next Italian battleship after VV...

I was unaware there were any Italian battleships projected after VV. Do you have any details of their characteristics?

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Re: Battleship Vittorio Veneto

Post by Tiornu » Fri Jan 07, 2011 5:00 pm

The Italian follow-up to VV is best known in its export version, UP-41. There was an article in Warship (2007?) that gives some details.

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Re: Battleship Vittorio Veneto

Post by RobertsonN » Mon Jan 10, 2011 8:53 am

I thought members would be interested in an original source on spaced armor that I came across some time ago (LONESENTRY.com). It is of a report in a US journal of a British study that was probably occasioned by the Fall of Italy and the VV protection system in particular.

Tactical and Technical Trends, No. 39, Dec. 1943

ENEMY USE OF SPACED ARMOR

The final paragraph reads "It is true that an AP or APC shot tends to turn towards the normal on perforating a plate, but in the case of spaced armor any advantage which might be gained thereby is likely to be neutralized by the acquisition of a transverse angular velocity which may result in increased yaw. For this effect to be appreciable, plates should be separated by a distance of at least one calibre."

To anyone familiar with the standard British naval books of the last 40 years (Raven & Roberts, Brown, Preston) this comes as a surprise because in these the disadvantage of the 'turn to the normal' (at least for horizontal protection) is often discussed but there is no mention of transverse angular velocity or yaw. It seems these authors may have relied on tests done in the 1920s and 1930s, and simply assumed that shells always remain aligned with the line of their trajectory to give optimum penetration that depends only on the obliquity.

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Re: Battleship Vittorio Veneto

Post by Bgile » Mon Jan 10, 2011 6:00 pm

I don't understand why the minimum distance would be caliber of the shell, since that would mean it hits the second plate long before the shell has cleared the first plate. How is it supposed to have the freedom to yaw?

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Re: Battleship Vittorio Veneto

Post by RobertsonN » Tue Jan 11, 2011 9:17 am

Bgile wrote: " ... minimum one calibre".

Good point. I don't understand that either. Intuitively, it should be the projectile length. Perhaps it is a mistake. This is, however, what it says.

Tiornu wrote: "...export version UP-41".

I don't have the Warship article. However, details are given in Dulin and Garzke and also the excellent Russian and Soviet Battleships by MacGlauchlin. I've always been surprised at the low displacement stated of 42000 tonnes, given that it had heavier armament, protection and speed compared with the VV. Perhaps the hull weight was low. The other noteworthy features are the very low armored deck, at fourth deck level, and the heavy AA armament for the time of the design, 1936. Placing the armored deck three levels down from the heavy (55 mm) forecastle deck would have given more effective protection through fuzing of bombs and shells, although it needed a higher armour weight for the barbettes.

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Re: Battleship Vittorio Veneto

Post by lwd » Tue Jan 11, 2011 1:50 pm

Isn't one caliber about the thickness required to get significant effects due to decapping? Could there be confusion over what was causing the improved performance of the armor array?

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Re: Battleship Vittorio Veneto

Post by Tiornu » Wed Jan 12, 2011 12:58 am

I've always been surprised at the low displacement stated of 42000 tonnes, given that it had heavier armament, protection and speed compared with the VV.
Keep in mind that VV was a "35,000-ton" design just as much as the next ship was a "41,000-ton" design.

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Re: Battleship Vittorio Veneto

Post by Thorsten Wahl » Wed Jan 12, 2011 8:17 am

As far as I can see the origin document RobertsonN is referring to, is ADM 281/31 The Ballistic performance of Spaced Armour Assemblies and the effect od varying the Arrangement of plate thickness

but this report deals with decapping effects of plate arrangements and their comparative performances using various plate arrangements of the same total thickness.

Unfortunately the effect of spacing between plates wasnt tested comprehensively, so the test seems suffering from a to low distance between two plates, as the used distance was only ~25 cm.
german sources spoke about ~70 cm spacing in flight direction for the 38 cm shell, to complete decapping for sure.

I think I have posted the results of this tests somwhere in this forum.
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Re: Battleship Vittorio Veneto

Post by RobertsonN » Wed Jan 12, 2011 9:49 am

Thanks for the explanation of the displacement of UP-41!

Perhaps by 1943 the British thought that both decapping and yaw were problems. In 1939 the RN went into the war with capital ships having almost 100% APC outfits. Roberts in "The Battlecruiser Hood" gives the Hood's outfit as mostly APC, with some CPC and a few shrapnel. To be testing uncapped AP in 1943 shows that they may by then have had doubts about this policy.
There is a thorough discussion of yaw and decapping on this site (Bismarck/Tirpitz = most powerful European Battleship? on 26 Sep. 2010). There, it is assumed that initial yaw on penetrating the upper deck is yaw down (towards the normal), presumably for the same reason that deflection is towards the normal, and then precession carries the shell towards yaw up and a less favourable condition for penetration at the armour (lower) deck.
It appears that by 1943 the RN realized that the disposition of armour in some Italian (and German) ships was more effective than they had earlier supposed.

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Re: Battleship Vittorio Veneto

Post by Dave Saxton » Thu Jan 13, 2011 4:46 pm

Make sure to keep trajectory change toward the normal and yaw different. They are not the same. The yaw becomes manifest via precession interacting with nutation. Precession of a spinning projectile begins 90* perpendicular to the axis of the force. When the projectile collides with a yaw plate the axis of impact is vertical (in the context of horozontal decks) causing the projectile to first shift away from the normal and then (usually) toward the normal after penetration in terms of its trajectory. The precession will begin 90* away from this axis causing initial yaw to be horizontally from the fight path relative to the orientation of the decks. Thus there will be some yaw right away. Precession rotates relatively slowly over time-distance, so the greater the distance between yaw plate and main plate; the more yaw becomes manifest, and it will be nose up or side ways yaw when it strikes the main armour. The more blunt the head shape the slower the rate of precession too. Thus in a deck system you want relatively great distance between the yaw plate and the main armour to realize the most potential of the effect. You also want any intervening decks to have negligable effect.

Where the precession has progressed to should the shell then interact with any inbetween deck will have an effect on the striking angle when the projectile finally reaches the main plate. If the projectile was yawed nose up upon penetrating the inbetween plate the trajectory will be shifted away from the normal once it reaches the main plate. If it was yawed nose down when it impacts any inbetween decks of significant thickness, the trajectory will be more toward the normal.

The amount of trajectory shift toward the normal or away from the normal is comparitively insignificant in the cases of the 38mm or 50mm or 80mm yaw decks. German tests quantified it as a max of ~4* trajectory shift if a homogenous armour yaw plate thickness was 50% the diameter of the projectile.

Removal of the cap has effect on the amount of precession and ultimately the amount of yaw. Removal of the cap increases the distance between the projectiles center of pressure and the center gravity. Complete removal of the cap will result in greater yaw as well as decreasing the shells penetration potential by removal of the cap.
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Re: Battleship Vittorio Veneto

Post by lwd » Thu Jan 13, 2011 7:31 pm

Dave Saxton wrote:.... Removal of the cap increases the distance between the projectiles center of pressure and the center gravity. ...
What is the defintion of center of pressure?

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