Bismarck and Iowa

Historical what if discussions, hypothetical operations, battleship vs. battleship engagements, design your own warship, etc.
spicmart
Member
Posts: 30
Joined: Wed Jan 07, 2009 5:41 pm

Bismarck and Iowa

Postby spicmart » Thu Jan 12, 2017 9:17 pm

Which one was the better battleship design wise?

Excluded are "software" like radar, aircraft, anti aircraft capability, crew condition etc..

Just brute force and toughness, resistance against attacks (artillery and torpedos).

paul.mercer
Senior Member
Posts: 597
Joined: Fri Mar 26, 2010 10:25 pm

Re: Bismarck and Iowa

Postby paul.mercer » Fri Jan 13, 2017 12:08 am

spicmart wrote:Which one was the better battleship design wise?

Excluded are "software" like radar, aircraft, anti aircraft capability, crew condition etc..

Just brute force and toughness, resistance against attacks (artillery and torpedos).


Iowa, without a doubt, she was a much more modern design with armour at least as heavy if not heavier than Bismarck and of course mounting 9 x 16" main armament and better AA weapons. As for resistance against bombs and torpedoes its hard to say, after all two of the largest battleships Yamato and Musashi which had even heavier armour were sunk by a combination of bombs and torpedoes.

alecsandros
Senior Member
Posts: 3992
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania
Contact:

Re: Bismarck and Iowa

Postby alecsandros » Fri Jan 13, 2017 7:27 am

Bismarck had thicker vertical armor (up to 475mm of total succesive armor layers) and thinner horizontal armor (as low as 130mm in successive layers).
IN terms of turrets and con tower, Iowa had thicker armor .
In terms of anti-torpedo protection, Bismarck had stronger defense.

In terms of broadside weight, Iowa had heavier punch.
In terms of broadside weight per minute, Bismarck had heavier punch.

User avatar
Dave Saxton
Supporter
Posts: 2906
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: Bismarck and Iowa

Postby Dave Saxton » Fri Jan 13, 2017 4:43 pm

Iowa's deck protection calculates to 140mm effective thickness. Tirpitz's calculates to at least 150mm effective thckness over the magazines and 130mm over the machinery.

However, the quality of the German armour materials are superior. It is well documented about the poor quality of US face hardened armour during that period. The German face hardened armour was virtually as good as the best British.

Additionally, I am thoroughly convinced that the German homogeneous armour was also superior to American homogeneous armour. When using the same measurement methods, the German chrom/moly Wh armour is tougher and more ductile than STS/Class B per tensile strength. And the tensile strength matters. It was found that if the tensile strength exceeded 80kg/mm2 then it was significantly more resistant to penetration at oblique striking angles, particularly against de-capped shells. It also has the correct concentration molybdenum, and in tests Mo significantly improved resistance to penetration by capped shell. STS had little to no Mo.

The quality of American Class A plates (face hardened) were found to be so poor that Class B plates were substituted for the turret face plates on all the new construction battleships. However, the use of homogeneous armour at such thickness does not equate to the same protective properties as the same thickness of high quality homogeneous plates either. It was found that thick class B plates 15% less resistant to penetration than standard. The problem was that with such thick homogeneous plates, that the interior of the plates did not respond properly to heat treatments, causing them to be brittle. No solution was ever found to this problem. Of course they could not provide the same level of protection as heavy high quality Krupp's Cemented can provide for heavy face plates.
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.

spicmart
Member
Posts: 30
Joined: Wed Jan 07, 2009 5:41 pm

Re: Bismarck and Iowa

Postby spicmart » Sat Jan 14, 2017 1:55 pm

Bismarck's shells were much lighter. Actually the lightest of all modern BBs' (from 15" upwards). Was that the result of German philosophy to put priority on RoF and precision/accuracy?
How would those shells perform at longe range? Were they enough to challenge Iowa?

User avatar
Dave Saxton
Supporter
Posts: 2906
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: Bismarck and Iowa

Postby Dave Saxton » Sat Jan 14, 2017 3:54 pm

The German 38cm gun could penetrate 130mm of Wh deck at 30,000 meters. The Iowa's decks protection is 140mm worth of, in my opinion, a slightly inferior material. Once past 30,000 meters the angle of fall of the 800kg projectile increases at rapid rate, due to it carrying less momentum down range than if it was heavier. This means that deck penetration increases quickly with greater range. By 32,000 meters it is exceeding 150mm deck penetration and by 36,000 meters it is exceeding 200mm deck penetration, according to one source.

For the same reason of the 12000kg 16" projectile carrying more momentum down range, steeper angles of fall are delayed until greater battle ranges, causing it have virtually the same deck penetration as the West Virginia's lighter 2240 lb 16" projectile per range. The penetration does not exceed 130mm (of in my opinion a slightly inferior material) until 30,000 yards, and does not exceed 150mm until 34,000 yards.

A Bismarck could certainly challenge an Iowa at long range.
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.

User avatar
Dave Saxton
Supporter
Posts: 2906
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: Bismarck and Iowa

Postby Dave Saxton » Sat Jan 14, 2017 4:08 pm

spicmart wrote: Was that the result of German philosophy to put priority on RoF and precision/accuracy?


The German L/4.4 was lighter because Krupp testing proved that a shell of that length (4.4 calibers) was more likely to penetrate heavy armour, better, and remaining in fit state to burst, than a longer /heaver shell would.
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.

spicmart
Member
Posts: 30
Joined: Wed Jan 07, 2009 5:41 pm

Re: Bismarck and Iowa

Postby spicmart » Sat Jan 14, 2017 11:00 pm

That is very interesting. So heavier does not seem necessarily to mean better.

As far as I understood because of the Bismarck's horizontal protection being better that offsets the (slightly?) better penetration power of Iowa's guns with the turtle deck arrangement being virutally unpenetratable at close and medium ranges.
And Bismarck's horizontal protection being as good as it was, her deck protection (almost) equal to the US BB's and her shells's deck armor defeating ability at long ranges practically the same as those of the US superheavy shells one can assume that Bismarck is a foe on par with the Iowas.

But then again I wonder what it was with the US guns and shells. Was there any other specific advantage that would warrant so much more weight or was it a waste of material?

Iranon
Member
Posts: 31
Joined: Mon Sep 09, 2013 9:23 am

Re: Bismarck and Iowa

Postby Iranon » Sun Jan 15, 2017 1:42 am

Not getting into metallurgy since the question was about the design.

The Germans made few assumptions about expected combat distances. The armour scheme was an attempt to give Bismarck's embedded vitals good protection in a wide range of scenarios, which the Germans thought impossible with a single layer system on a reasonable weight budget:
Modern high-velocity guns (as the continenal European navies used) had impressive belt penetration at short ranges, an expected upper limit of 30km for effective fire was a great challenge for the horizontal armour (against their own shells which performed well at oblique angles, but also against heavier shells fired at a lower velocity). They generally considered their system to give them the largest advantage at short to medium ranges where enemy shells would have to strike deck or scarp at a very unfavourable angle after penetrating the belt in order to reach the vitals. Protection against long-range fire was still very good (or excellent if you assume likely effects of the spaced array that are hard to quantify).

There's a downside to the system though - a thicker belt with less behind it would be better at keeping battleship shells complete out of the ship. There was no particular weakness to cruiser/secondary fire.
Turret protection wasn't particularly heavy, and seems to have been based around making most of the turret safe at most ranges rather than achieving immunity in a particular range band.
All in all, I believe the scheme performed as designed and the choice of "armouring for every scenario" was sound - KM and RN (which didn't particularly stress extreme-range gunnery) scored the longest confirmed hits at 24km, IJN and USN (which did) battleships exchanged fire at ranges down to about 5km.

The 38cm main artillery was not particularly powerful compared to the modern French and Italian designs, but accuracy and rate of fire were excellent which can't be said for those other high-velocity guns.
High velocity gave it good belt penetration, the shell design gave it surprisingly good deck penetration despite its modest weight although concerns were raised over the reliability after oblique impacts. As phrased in the original post, Bismarck has a considerably more powerful secondary battery if that becomes relevant (even if we discount the 10,5cm guns since they were AAA by design. On paper they outranged the American dual purpose guns).

*

The Americans expected battle at very long ranges and built their ships that way including Iowa - heavy deck armour to safeguard against plunging fire, large-calibre guns firing heavy, blunt-nosed shells that were optimised for deck penetration at the expense of belt penetration and bursting charge. Iowa's guns with their higher muzzle velocity than their predecessors have a more balanced profile and are powerful indeed, but still excel mostly at long range.

The belt is declined to increase protection against broadside attacks, and deeper than Bismarck's (tapering) for good protection against underwater hits. This isn't without its problems though, the Americans believed it interfered with the torpedo protection system and didn't plan a repeat in (never built) future classes; despite a higher nominal rating I'd rate the TDS below Bismarck's. Also, an internal belt exposes the space outside it (nothing vital of course) even to cruiser fire and may complicate repairs... but analogous problems exist to a greater degree in Bismarck's scheme as far as battleship-calibre shells are concerned. Citadel shape is different (taller but shorter), generally more important equipment was outside the citadel with less redundancy, but layout and practices combined to give American ships a good reputation as far as damage control is concerned.
The turrets carry much heavier armour than Bismarck's; while Dave Saxton pointed out the problems that arose, the sheer amount of metal gives an advantage to Iowa here.

On the whole, Iowa has a larger main artillery but is less well protected. Under average conditions that actually took place I'd have more confidence in Bismarck. At long range (beyond the longest historical hit, but within the realm of the plausible), Iowa has some things going for it and may be favoured.

User avatar
Dave Saxton
Supporter
Posts: 2906
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: Bismarck and Iowa

Postby Dave Saxton » Sun Jan 15, 2017 4:33 am

The Americans planned for a specific type of naval combat with their battleships. This type of combat was battle fought between battle lines during daylight, in reasonably good weather, enabling very long ranges, and using aircraft spotting (at the time the doctrine more fully evolved circa the mid 1930s, radar was strictly experimental and only actually known by a very few persons at that). In such a scenario it was important that your battle line not ever be "out ranged". Hence the American designers designed with this type of scenario in mind with biases to long range. However, the realities of naval warfare changed, rendering the type of battle planned for unlikely to happen at all.

By 1942, air power meant that air battles were fought during the day, and surface action between surface combatants, including battleships, would be fought almost exclusively at night. Indeed after 1941 nine out of 10 naval surface battles would historically be fought at night. Night battles would invariably be fought at ranges of less than about 20,000 yards. Radar didn't change this. Radar can not identify with any certainty that what your shooting at is the target you want to be shooting at. Visual identification of the target is still required in just about every case.

The American battleship commander, Admiral Lee, declined chances for night battle late war, waiting instead for the type of battle his ships were better designed for,...... that would never come. After the Naval Battle of Guadalcanal, which he won, Lee still seemed shaken about what could have gone wrong:

Our battleships are neither designed nor armed for close ranged night actions with enemy light forces. A few minutes of intense fire, at short range, from secondary guns can, and did, render one of our new battleships deaf, dumb, blind, and impotent through the destruction of radar, radio, and fire control circuits.



Indeed, the American battleships had no specialized night optics, had rather poor star shells, and eyeballs invariably were blinded by their own super bright gun flashes. Weapons were optimized for long range battle during daylight, and the protection scheme was also biased to long range battle. They did have very good radars but that could not change the basic nature of night combat. American battleship sailors were not even trained for this type of combat. Lee pointed out this rather glaring oversight as one of the reasons he declined to risk a possible night battle during the Marianas battle.

For the type of battles actually fought during WWII only the Bismarck design had a protection scheme at least suited for this type of combat. Moreover, the offensive weapons with high velocity ballistics, a heavy middle artillery, and potentially high rates of fire, was also better for these types of surface combat.
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.

alecsandros
Senior Member
Posts: 3992
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania
Contact:

Re: Bismarck and Iowa

Postby alecsandros » Sun Jan 15, 2017 8:48 am

spicmart wrote:But then again I wonder what it was with the US guns and shells. Was there any other specific advantage that would warrant so much more weight or was it a waste of material?

After perforating the enemy armor, the US shell produced more damage, as it's mass (1227kg vs 800kg, minus the caps for both of them) would be transformed into flying pieces of debris, each with it's own velocity and damage potential. The explosive charges carried by the 2 projectiles were comparable.

spicmart
Member
Posts: 30
Joined: Wed Jan 07, 2009 5:41 pm

Re: Bismarck and Iowa

Postby spicmart » Sun Jan 15, 2017 3:28 pm

"despite a higher nominal rating I'd rate the TDS below Bismarck's."

What does nominal rating mean?


"Turret protection wasn't particularly heavy, and seems to have been based around making most of the turret safe at most ranges rather than achieving immunity in a particular range band."
"The turrets carry much heavier armour than Bismarck's; while Dave Saxton pointed out the problems that arose, the sheer amount of metal gives an advantage to Iowa here."

With Bismarck's turrets having really so little armor compared they must have been way more easily knocked out? That must have been a serious disadvantage if one looks at the armor of other BBs' turrets.

spicmart
Member
Posts: 30
Joined: Wed Jan 07, 2009 5:41 pm

Re: Bismarck and Iowa

Postby spicmart » Sun Jan 15, 2017 3:36 pm

"For the type of battles actually fought during WWII only the Bismarck design had a protection scheme at least suited for this type of combat. Moreover, the offensive weapons with high velocity ballistics, a heavy middle artillery, and potentially high rates of fire, was also better for these types of surface combat."

So Bismarck's protection scheme was actually not that bad after all considering how much maligned it had been in discussions past.

Iranon
Member
Posts: 31
Joined: Mon Sep 09, 2013 9:23 am

Re: Bismarck and Iowa

Postby Iranon » Sun Jan 15, 2017 5:27 pm

@spicmart: Bismarck's torpedo defense system was rated to withstand 250kg of TNT, expectation was that damage inwards of the TDS from larger explosions would be contained rather than prevented - Bismarck featured extensive subdivision. The rating seems quite conservative; German assumptions of the time were generally pessimistic.
IIRC Iowa's Torpedo Defense System was designed to withstand 700lb of TNT (317,5kg), but the system was considered (within the USN) to be flawed before the ships' commission and unlikely to be up to its design specs.

Turrets were routinely knocked out by non-penetrating hits. Different nations came to different conclusions whether it was worth the weight to give them theoretical immunity to battleship shells - they were quite likely to be hit, but this usually didn't threaten the ship and it was dubious whether armour would keep them in action.
Germany and the UK didn't think so. Given how well Bismarck's embedded vitals were protected and how she had her main artillery knocked out in her final battle (details and whether more armour would have helped unclear), some think they should have gone for it - including German naval architects after the loss of Bismarck. OTOH, the geometry of Bismarck's turrets and their armour aimed to minimise penetrable parts at any given range rather; considering they didn't want to optimise for a narrow range band total protection (which may not help in practice even if it keeps shells out) would have required excessive weight.

@ alecsandros: I'm not aware of specific American or German views on this, but the British came to the conclusion that the damage potential of a shell scales almost exclusively with the power of its bursting charge (Bismarck ahead of Iowa by 7% or so). There were also concerns that a heavy shell around a small burster may underperform (ability to ensure proper fragmentation, insufficient velocity of splinters).
Probably not too relevant since very crude and many other considerations are involved but I found the line of thought interesting: a kg of explosives displacing steel would lighten a shell by about 3.7kg.

spicmart
Member
Posts: 30
Joined: Wed Jan 07, 2009 5:41 pm

Re: Bismarck and Iowa

Postby spicmart » Sun Jan 15, 2017 6:58 pm

Bismarck's TDS rating was relatively low, also nominally inferior to Richelieu's iirc. The extensive subdivision of Bismarck to counter that is said to be as effective as the french TDS approach? I always thought that torpedo protection on german ships was outstanding.
But 250 kg TNT does not seem much. How much explosives did ww2 torpedo warheads pack?
If that was more than the torpedo bulkhead was assumed to take, did that mean that it would be breached with great certainty?

About the importance and effect of turret geometry I know nothing. Can you enlighten me?


Return to “Hypothetical Naval Scenarios”

Who is online

Users browsing this forum: No registered users and 1 guest