Bismarck vs. Iowa

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RobertsonN
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Re: Bismarck vs. Iowa

Post by RobertsonN »

With regard to fuzes for shells with long underwater travel, it is surprising that there is no mention in ADM 481, Suppl. 6, of the long fuse delays required. As the shell was intended to burst inside the ship, they must have had a fuse in mind. By this time, bombs such as the Tallboys dropped on Tirpitz did have longer fuse delays I believe. There is also no mention of the problem of such shells only detonating far on the lee side of ships whose superstructure they have passed through. However, two of the superstructure hits on POW did not detonate but still caused significant splinter damage through fragmentation of the aerodynamic windshield and ship's structure they passed through.
The underwater CPs were different from normal CPs, having somewhat smaller bursting charges, which was a disadvantage. In the end, the Board chose the underwater trajectory CPs because they were deemed capable of inflicting serious damage in the range 20000 to 30000 yds, where the AP was thought to be non-penetrating. Of the variants for the APs, they chose the lightest (2240 lb) shell, which had the greatest range (46300 yds) but the least deck penetration (6 in at 35400 yds). Perhaps this choice was made because the lightest shell, given British technology, was the most robust at oblique impact.

Thank you for mentioning CB 04039 (2). I have managed to find this. I need to study it. As far as MV measuring equipment is concerned, I seem to remember that the weight of such equipment is included in the Bismarck's armament weight, but must check this. Such equipment would seem to remove this problem of knowing what the MV is after so many rounds have been fired.
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Herr Nilsson
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Re: Bismarck vs. Iowa

Post by Herr Nilsson »

There were two Vo measuring instruments on BS. The first one in the "Kreiselumformerraum" for Anton, Bruno, and MA-turrets I and II, the other one in "Havarieschaltstelle 10" for Caesar, Dora and MA-turrets III.
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Re: Bismarck vs. Iowa

Post by Bgile »

Japanese AP shells had much longer fuze delays than anyone else's and were designed to travel long distances under water. They also tended to pass through superstructure without doing serious damage.
Thorsten Wahl
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Re: Bismarck vs. Iowa

Post by Thorsten Wahl »

yes fuzing of underwatertravel projectiels seems the most serious problem. Fuze action should start at penetration of plate, but not on impact on water. I dont have any plan for a reliable solution of this problem
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RobertsonN
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Re: Bismarck vs. Iowa

Post by RobertsonN »

In CB 04039 (2), underwater hits also play an important role, although here normal APC are considered useful. There is only the comment that at 22000 yds, angle of fall of a 14 in shell is 18 deg, so that richochet on the surface will not occur.
I see from this document that the RN did after all view inclined belts as having greater protective value. The inner edges of the periods of immunity against the German 15 in are given as KGV (14200 yds (15 in)/16000 yds (14 in)), while Nelson is given as 14000 yds (14 in)/16000 yds (13 in). As the quality of the KGV's armor was better than that of Nelson (so that 14 in (KGV) might have been the equivalent of as much as 17.5 in (Nelson)) the factor for the value of inclined armor might well be similar to that the US and others used (Iowa's 12.2 in was equivalent to 17.3 in vertical at 25000 yds).
The 1942 document rates the Bismarck as much poorer than the KGV and to a lesser extent the Nelson. In fact, the Bismarck (leaving speed and range out of it) is little better than Warspite. Must have been a morale booster to know the Germans were building such poor ships! The 15 in was seen as the most effective British gun, with the outer edge of the Bismarck's immunity zone coming down to a little over 20000 yds, compared with 22000 yds for 14 and 16 in guns.
Things had changed by Jan. 1946 (ADM481, Suppl. 6). The target described as 'similar to Tirpitz' now has a 12 in belt and 6 in deck, the latter being rated as safe at up to 34000 yds against a 16 in APC 2391 lb shell and 35400 yds against the 2240 lb shell actually chosen. The factor A in that report (ratio of hits penetrating the citadel to hits on the ship in the area of the citadel) is considered carefully. The value can be lowered for three reasons (apart from not being able to pentrate the main armor): (1) fuzing, (2) trajectory being over main armor deck (for which a low armor deck with scarps is ideal) and (3) hitting obstructions that move the shell out of its straight path so that it misses or fails to penetrate the armor deck. In 1942, (1) was not considered even though it was very likely at 18 deg angle of fall and fuze delays of 0.035 sec. In 1942 the upper deck is not given as being of armor plate, no earlier ship had armor here. Also the diagram does not put any armor thickness on the scarps and the immune zone they calculated assumes no armor here. The Warspite/QE had this arrangement with a gap here, and also none of the German post-Jutland fast battleship/battlecruiser designs had armored slopes, a fact the British may have been aware of.
In 1942 ideal fighting range was considered to be 22000 yds (with the enemy ideally about 30 deg fore or aft of the beam) at which range the deck could be penetrated and damaging underwater hits scored. In 1946 range was either over 35000 yds to obtain deck penetrations (I assume of magazine) while at 20000 yds+ the CP could score damaging underwater hits. For the fuzes they assumed 100% efficiency.
Last edited by RobertsonN on Fri Apr 01, 2011 8:48 am, edited 4 times in total.
RobertsonN
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Re: Bismarck vs. Iowa

Post by RobertsonN »

RobertsonN wrote:In CB 04039 (2), underwater hits also play an important role, although here normal APC are considered adequate. There is only the comment that at 22000 yds, angle of fall of a 14 in shell is 18 deg, so that richochet on the surface will not occur.
I see from this document that the RN did after all view inclined belts as having greater protective value. The inner edges of the periods of immunity against the German 15 in are given as KGV (14200 yds (15 in)/16000 yds (14 in)), while Nelson is given as 14000 yds (14 in)/16000 yds (13 in). As the quality of the KGV's armor was better than that of Nelson (so that 14 in (KGV) might have been the equivalent of as much as 17.5 in (Nelson)) the factor for the value of inclined armor might well be similar to that the US and others used (Iowa's 12.2 in was equivalent to 17.3 in vertical at 25000 yds).
The 1942 document rates the Bismarck as much poorer than the KGV and to a lesser extent the Nelson. In fact, the Bismarck (leaving speed and range out of it) is little better than Warspite. Must have been a morale booster to know the Germans were building such poor ships! The 15 in was seen as the most effective British gun, with the outer edge of the Bismarck's immunity zone coming down to a little over 20000 yds, compared with 22000 yds for 14 and 16 in guns.
Things had changed by Jan. 1946 (ADM481, Suppl. 6). The target described as 'similar to Tirpitz' now has a 12 in belt and 6 in deck, the latter being rated as safe at up to 34000 yds against a 16 in 2391 lb APC shell and 35400 yds against the 2240 lb shell actually chosen. The factor A in that report (ratio of hits penetrating the citadel to hits on the ship in the area of the citadel) is considered carefully. The value can be lowered for three reasons (apart from not being able to pentrate the main armor): (1) fuzing, (2) trajectory being over main armor deck (for which a low armor deck with scarps is ideal) and (3) hitting obstructions that move the shell out of its straight path so that it misses or fails to penetrate the armor deck. In 1942, (1) was not considered even though it was very likely at 18 deg angle of fall and fuze delays of 0.035 sec. In 1942 the upper deck is not given as being of armor plate, and of course no earlier ship had armor here. Also the diagram does not put any armor thickness on the scarps and the immune zone they calculated assumes no armor here. The Warspite/QE had this arrangement with a gap here, and also none of the German post-Jutland fast battleship/battlecruiser designs had armored slopes, a fact the British may have been aware of.
In 1942 ideal fighting range was considered to be 22000 yds (with the enemy ideally about 30 deg fore or aft of the beam) at which range the deck could be penetrated and damaging underwater hits scored. In 1946 range was either over 35000 yds to obtain deck penetrations (I assume of magazine) while at 20000 yds+ the CP could score damaging underwater hits. Ideal target angle was now seen as 45 deg. For the fuzes they assumed 100% efficiency.
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Re: Bismarck vs. Iowa

Post by Thorsten Wahl »

Unfortunately the british experts didnt take any notice about the protective effect of the scarp even in 1946.

RobertsonN
(ADM481, Suppl. 6)
is not a admirality report (ADM) but a report of Ministry of Supply (SUPP).
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Byron Angel
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Re: Bismarck vs. Iowa

Post by Byron Angel »

..... Not sure this is even apropos, given the dramatic difference in projectile technoloies (and more so because I cannot recall the precise citation - probably either from McGlaughlin's "Russian Battleships" or from one of the RJW papers done by DK Brown or Campbell or Grove). In any case, I recall reading an analysis of the effects of the bombardment of the Russian battleships in Port Arthur anchorage by Japanese 11-inch howitzers atop Telegraph Hill. Of those shots which actually hit a ship, only about half actually reached the protective deck, and a not inconsiderable amount of flooding was caused by mining effect of close misses detonating in the water alongside.

For what it's worth.

B
RobertsonN
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Re: Bismarck vs. Iowa

Post by RobertsonN »

It is noticeable in CB 04039 (2) that the MV of the German 38 cm is still given as 2721 fps (from Russian sources) and not the usual 2690 fps. There is some mention in a discussion about H class v. Lion on the NavWeapons website that the Germans carried out ballistic tests using charges that were at a lower temperature than normal, perhaps to give more realistic tables for the guns in service or to reduce wear in the testing phase. In this case, 2721 fps might have indeed been the true new barrel MV. Anyone care to comment about this?
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Re: Bismarck vs. Iowa

Post by Thorsten Wahl »

The gun was developed from the beginning as having 820m/s muzzle velocity.

Krupp data and data from navy service regulations for ammunition are going conform to a 820 m/s muzzle velocity gun. This MV referring to 210 kg RPC 32 or later 212 kg RPC 38
according rangtable for the projectile from GKdos 100 maximum range is 35.6 km at 30 degrees barrel elevation.

The Baron Mulheim Rechberg mentions in his book 36.2 km or so maximum range for the SK 38. I dont know wheter this is a fail of memory or not.
If this is correct the increase in range requires a increase in MV by about 12-16m/s additional MV.

There are also different informations on lifespan of the barrel available. There are secondary sources that say this is 180-210 rounds but original Krupp datasheet says 242 rounds (for 210 kg RPC 32)
this possibly increased wear might also indicate an increased MV.
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Re: Bismarck vs. Iowa

Post by Byron Angel »

Cannot say for sure, but range table data MAY have been computed for the average MV over the expected useful EFC life of the gun tube, or for some discounted MV short of the absolute maximum possible new gun value.
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Re: Bismarck vs. Iowa

Post by Thorsten Wahl »

The ballistics of the projectile for varying Vo can be determined from the Tagesverbesserungstafeln. You get then impact angle and -velocity for any given Vo and elevation.

With this data you can determine the corresponding penetration data from the penetration graphics, wich are plotted for every combination between normal impact and about 70 degrees obliquity and you receive the penetrable plate thickness for complete pentration-projectile fit to burst(Heilbleiben) and partial pentration (Grenzschuss)- plate holed projectile broken at least 50% of the masss of projectile can be found behind the plate and cause splinterdamage.
The Grenzschussdata were used to determine damage especially to barbettes, turrets and conning tower wich are containing sensitive items wich could be seriously damaged also by splinters.
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!
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Re: Bismarck vs. Iowa

Post by Seekanone »

IMHO, at long ranges, IOWA wins hands down. The USN had practiced pre-war in the mid-1930s at ranges over 30,000 yards and the IOWA would have been well prepared to engage at such distances. Bismarck's decks would have been extremely vulnerable to the 2700 lb AP projectile at such ranges.
BISMARCK would have been a tougher foe inside of 20,000 yards and especially inside of 15,000 but the chances of her being able to close the range would have been slim. I like the Bismarck as a design, with two turrets fore and aft, a nice funnel and director tower combination, and a hull with a long swept sheer forward to the bow. On the other hand, I no longer see her as super ship which was unfairly sunk by the Royal Navy. BISMARCK was a good battlewagon but not a super ship by any means.
Richelieu and South Dakota were marginally better and King George V was a good match for her as well. :dance:
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Re: Bismarck vs. Iowa

Post by RobertsonN »

While it is arguable that the Richelieu was a better design than the Bismarck, the French capital ships proved very vulnerable in practice. HE bombs caused great structural damage because they had no bomb deck, while near misses were also damaging because of the internal belt. In theory their SPS was second to none, but in practice progressive flooding through leaking cable ways threatened their buoyancy. A non-contact 18 in torpedo detonation crippled the ship, causing structural damage to some gun mounts. Perhaps they were lightly built similar to some Italian ships. The thick deck armor did not appear to meet expectations, as noted elsewhere on this site. The 15 in guns had to be derated: the Italians did better here. The triple 6 in turrets were of very limited use in the originally intended DP role, at least durimg WWII. The original light AA was very weak.
On the other hand, they were fast and had good range, and would have been useful ships in a chase. The design derived from the Dunkerque, which was a counter to the pocket battleships.
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Re: Bismarck vs. Iowa

Post by Tiornu »

I don't believe we've seen anything indicating the Richelieu armor deck fell short of design specs. It's hard to critique the ship on the basis of the under-bottom torpedo hit, which may also have involved 1500 lbs of explosive in a shallow harbor. Unlike British or American ships, Richelieu had ebonite mousse filling the space outside her belt to exclude flooding from near misses. When were the 15in guns derated? The 6in guns were better suited to AA action than the analogous guns aboard Bismarck or Littorio.
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