Bismarck vs. Iowa

Historical what if discussions, hypothetical operations, battleship vs. battleship engagements, design your own warship, etc.
Byron Angel
Senior Member
Posts: 1167
Joined: Sun Mar 06, 2011 1:06 am

Re: Bismarck vs. Iowa

Post by Byron Angel » Thu Jun 16, 2011 12:29 pm

alecsandros wrote:
lwd wrote:... Out to well over 30,000 yards Iowa is capable of penetrating the armor at the waterline of Bismarck and for the protected area there is a good chance for a proper high order detonation.
I don't think so. The normal fuze delay for 2700pdr was 0.033sec. The German ship had 2 or more armor layers facing the most likely trajectories , and a shell would be decaped and fuzed by the first layer, but it will hit the second layer before the fuze runs out, causing it to become a dud.

..... Hi Alex. I'm not sure the above is what you intended to say. It is my understanding that, apart from de-capping a striking projectile, the 50mm weather deck also served to initiate fuze action. Whereas the typical fuze delay of a typical AP projectile of the era was in the 0.025 to 0.035 second range, a projectile piercing the 50mm deck at any modest angle of fall would likely detonate before traversing the slant distance to reach the main 80mm armor deck two levels below. The 80mm lower armored deck was of sufficient thickness to stop even the largest fragments of a projectile exploding above it.

While this protection scheme was efficient weight-wise and rendered some degree of protection to middle and main deck spaces that might otherwise have been impractical, it did involve certain calculated compromises. It would not stop a dud projectile from reaching the vital spaces. Nor would it defeat a projectile with an unusually long delay; i'm referring here to a statistical outlier giving an unusually long delay (the delay action of fuzes of that era were not uniformly precise time-wise). A thicker single armored deck would have been able to deal with these "special cases" as well and extended the outer range limit at which any projectiles could be defeated.

..... not to go over old territory yet again.

B

alecsandros
Senior Member
Posts: 4349
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania

Re: Bismarck vs. Iowa

Post by alecsandros » Thu Jun 16, 2011 12:43 pm

Hello Byron,
My comment regarded the fuze delays of US 2700pd shells, the ones employed by the Iowa class.. I remember the average delay for this shell being ~ 0.033s.
At 27km, this shell fired from Iowa's guns would fall at 478mps (and at smaller distances, the speed was greater, of course). The 50mm upper-deck would reduce this speed with 30-40 mps at best, leaving ~ 440mps exit speed of the de-caped (and fuzed) shell. 440 x 0.033 = 14,52 m to be traveled before detonation.

It is difficult to find this distance inside Bismarck/Tirpitz without the shell hiting another internal armored section You can find it for certain trajectories, with larger obliquities (with the horizontal obliquity component bieng larger). HOwever, in such trajectories, the post-perforation effects on the shell would be bigger, as yaw was directly corelated to initial obliquity to the impacted plate. COnsequently, exit velocities may have been lower, but so would the probability of the fuze to function at all.

lwd
Senior Member
Posts: 3810
Joined: Sat Jun 17, 2006 2:15 am
Location: Southfield, USA

Re: Bismarck vs. Iowa

Post by lwd » Thu Jun 16, 2011 1:54 pm

alecsandros wrote:
lwd wrote:
There's quite a bit of difference between a 1600lb bomb and a 2700lb AP round. For instance from http://www.wehrmacht-history.com/luftwa ... -bombs.htm
That's not the point; the point is that a 0.033s fuze delay shell would be decaped by the first armored layer, and than shatter against the second. The fuze would not go off at all, because it was a mechanical fuze, and rapid changes in the direction of movement would make it ineffective. Even if it wouldn't shatter (which is difficult to asume, given the properties of whotan and KC n/A armor) the fuze would almost certainly be rendered blind, given to yaw effects and off-center perforation.
I addressed that point. In the case of the 14" round hitting the SoDak it was rejected by the barbet armor and still detonated high order. My point was that just because it was rejected by the armor doesn't mean that it won't explode high order or even that it will shatter. I've seen battleship projectiles that have partially penetrated armor for instance and while obviously damaged they were a long way from shattering.

Another assumption that you made was that if a shell goes high order the damage is almost completly related to the size and composition of the explosive filler. This is true for blast damage but not so much for fragmentation damage. In general finer shell fragments give you better coverage but a smaller area of damage while larger fragments can cause more damage at greater range but will hit fewer things. One would expect that if the shells were otherwise designed and produced of under similar circumstances with simmilar materials a lighter shell with a heavier charge would tend to produce more small (but higher velocity) fragments. In comparing the two shells however little of that holds true so it's not at all clear which would cause the most fragmentation damage I do suspect that there would be more very large fragments traveling at lower velocities from the US shell but that's a partially educated guess on my part. Furthermore the use of armor quality steel in the internal structure of the US BB will likely attenuate the blast and fragment damage more.

alecsandros
Senior Member
Posts: 4349
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania

Re: Bismarck vs. Iowa

Post by alecsandros » Thu Jun 16, 2011 6:21 pm

lwd wrote:
I addressed that point. In the case of the 14" round hitting the SoDak it was rejected by the barbet armor and still detonated high order. My point was that just because it was rejected by the armor doesn't mean that it won't explode high order or even that it will shatter. I've seen battleship projectiles that have partially penetrated armor for instance and while obviously damaged they were a long way from shattering.
We're not on the same page here. My words concerned the multi-layered armor scheme employed on the Bismarck, and the high probability of a shell to not explode at all due to the stresses involved in perforating 2 consecutive layers of armor before the fuze runs of.
Another assumption that you made was that if a shell goes high order the damage is almost completly related to the size and composition of the explosive filler.
Where have I made thsi asumption ?

lwd
Senior Member
Posts: 3810
Joined: Sat Jun 17, 2006 2:15 am
Location: Southfield, USA

Re: Bismarck vs. Iowa

Post by lwd » Thu Jun 16, 2011 6:48 pm

alecsandros wrote:
lwd wrote:
I addressed that point. In the case of the 14" round hitting the SoDak it was rejected by the barbet armor and still detonated high order. My point was that just because it was rejected by the armor doesn't mean that it won't explode high order or even that it will shatter. I've seen battleship projectiles that have partially penetrated armor for instance and while obviously damaged they were a long way from shattering.
We're not on the same page here. My words concerned the multi-layered armor scheme employed on the Bismarck, and the high probability of a shell to not explode at all due to the stresses involved in perforating 2 consecutive layers of armor before the fuze runs of.
The effect of penetrating a very oblique deck and striking the barbett was effectivly hitting a multi-layered armor scheme. The assumption that there is a high probility of the shell not exploding seems poorly supported.
Another assumption that you made was that if a shell goes high order the damage is almost completly related to the size and composition of the explosive filler.
Where have I made thsi asumption ?
My apologies it whas RobertsonN who stated:
Blast effects are entirely dependent on charge and the Germans considered that splinter effects were too
Which implies he supports the German position but doesn't actually say so.

alecsandros
Senior Member
Posts: 4349
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania

Re: Bismarck vs. Iowa

Post by alecsandros » Thu Jun 16, 2011 7:03 pm

lwd wrote:
The effect of penetrating a very oblique deck and striking the barbett was effectivly hitting a multi-layered armor scheme. The assumption that there is a high probility of the shell not exploding seems poorly supported.
I did not know the 14" shell also passed through a deck; and I'm not saying any shell must necessarily become a dud if it passes through 2 layers of armor (the case of Jim Bean is very good in this matter - teh US shell passed through three armored decks and still exploded). What I'm saying is that in the case of Bismarck/Tirpitz, the design and materials used were such that a shell would have big difficulties in remaining in a fit state to burst after 2 or more consecutive armor impacts.
The reasons are described in ADM1931 IIRC, (the paper which concerns yaw) and in Krupp tests that showed deformations of the shells perforating whotan decks, due to un-equal tearing forces distributed along the length of the shell. The longer the shell, the bigger the severity of the deformation. Thorsten has several nice posts about this.

One British test from 1945 presents the effects of 14, 15 and 16" British shells "attacking" the horizontal layout of Tirpitz (50 + 80mm whotan). The results impressed the engineers, as yaw effects were greater than anticipated by them and the all the shells fired were rendered inert.

Byron Angel
Senior Member
Posts: 1167
Joined: Sun Mar 06, 2011 1:06 am

Re: Bismarck vs. Iowa

Post by Byron Angel » Fri Jun 17, 2011 12:57 am

alecsandros wrote: One British test from 1945 presents the effects of 14, 15 and 16" British shells "attacking" the horizontal layout of Tirpitz (50 + 80mm whotan). The results impressed the engineers, as yaw effects were greater than anticipated by them and the all the shells fired were rendered inert.


Hi Alex,

I'd be quite interested to see this document.

B

RobertsonN
Member
Posts: 197
Joined: Wed Jan 05, 2011 9:47 am

Re: Bismarck vs. Iowa

Post by RobertsonN » Fri Jun 17, 2011 8:11 am

I had a closer look at the German curves for splinter effect versus calibre for APC and nose fused HE.

For a shell of given size the penetrative power of splinters increases with burster size (40 mm Wh (nose fused HE) v 30 mm (APC) for 15 in). However, for different shell sizes, mass is also a factor. The splinters from a 315 kg nose fused 11in HE shell with a burster of 21.8 kg could penetrate 28 mm of Wh whereas those from an 800 kg 15 in APC with a burster of 18.8 kg could penetrate 30 mm. The Germans also found that an 11 in shell bursting in an engine room would disable the machinery but it would be repairable. A 15 in burst would require a new engine.

In Suppl. 6 481 the British compared the effects of various APC and Common shell: 16 in shells around 2375 lb with 59 lb and at least 150 lb bursters, respectively. It is stated that it was assumed that the effect of different shells is directly proportional to burster size. That sounds a bit stronger than the German position.

Byron Angel
Senior Member
Posts: 1167
Joined: Sun Mar 06, 2011 1:06 am

Re: Bismarck vs. Iowa

Post by Byron Angel » Fri Jun 17, 2011 11:36 am

RobertsonN wrote:I had a closer look at the German curves for splinter effect versus calibre for APC and nose fused HE.

For a shell of given size the penetrative power of splinters increases with burster size (40 mm Wh (nose fused HE) v 30 mm (APC) for 15 in). However, for different shell sizes, mass is also a factor. The splinters from a 315 kg nose fused 11in HE shell with a burster of 21.8 kg could penetrate 28 mm of Wh whereas those from an 800 kg 15 in APC with a burster of 18.8 kg could penetrate 30 mm. The Germans also found that an 11 in shell bursting in an engine room would disable the machinery but it would be repairable. A 15 in burst would require a new engine.

In Suppl. 6 481 the British compared the effects of various APC and Common shell: 16 in shells around 2375 lb with 59 lb and at least 150 lb bursters, respectively. It is stated that it was assumed that the effect of different shells is directly proportional to burster size. That sounds a bit stronger than the German position.

..... For what it's worth, British WW1 investigation (Final Report of the President of the Projectile Commission - 1917) observed some interesting differences in effect among different projectile types -

Lyddite charged HE projectiles produced a cloud of very small fast moving fragments in all directions, which generally were able to pierce one unarmored internal bulkhead or deck, but were stopped by a second.

Black powder charged common projectiles dispersed in a forward cone axial to projectile path a limited number of heavy slow moving heavy fragments (one might call them 'slabs' perhaps) able to smash through several such unarmored internal bulkheads in succession before exhausting their energy.

So it does indeed seem that overall projectile damage effect (outside of pure blast effect) is indeed a function of both fragment velocity AND size.

B

lwd
Senior Member
Posts: 3810
Joined: Sat Jun 17, 2006 2:15 am
Location: Southfield, USA

Re: Bismarck vs. Iowa

Post by lwd » Fri Jun 17, 2011 2:27 pm

alecsandros wrote:
lwd wrote:
The effect of penetrating a very oblique deck and striking the barbett was effectivly hitting a multi-layered armor scheme. The assumption that there is a high probility of the shell not exploding seems poorly supported.
I did not know the 14" shell also passed through a deck; and I'm not saying any shell must necessarily become a dud if it passes through 2 layers of armor (the case of Jim Bean is very good in this matter - teh US shell passed through three armored decks and still exploded). What I'm saying is that in the case of Bismarck/Tirpitz, the design and materials used were such that a shell would have big difficulties in remaining in a fit state to burst after 2 or more consecutive armor impacts.
The reasons are described in ADM1931 IIRC, (the paper which concerns yaw) and in Krupp tests that showed deformations of the shells perforating whotan decks, due to un-equal tearing forces distributed along the length of the shell. The longer the shell, the bigger the severity of the deformation. Thorsten has several nice posts about this.
The problem is that requires penetrating both decks. In at least some of the cases we are discussing the inner deck would reject the shell rather than break it up during penetration. If it does penetrate then it's a signficant threat even if it does not detonate. As for the shell hitting SoDak's barbett read the damage report / analysis I linked.
One British test from 1945 presents the effects of 14, 15 and 16" British shells "attacking" the horizontal layout of Tirpitz (50 + 80mm whotan). The results impressed the engineers, as yaw effects were greater than anticipated by them and the all the shells fired were rendered inert.
But this was British shells over some fixed range of conditions was it not? What were the angles and ranges involved? How do the shells compare? From the right up in the SoDak report the Japanese shell obviously was severely stressed and still went high order.

lwd
Senior Member
Posts: 3810
Joined: Sat Jun 17, 2006 2:15 am
Location: Southfield, USA

Re: Bismarck vs. Iowa

Post by lwd » Fri Jun 17, 2011 2:34 pm

The science of how shells fragmented during WWII was obviously not very refined. A classic example would be the US "pineapple" grenade. The theory was that the grooves would cause result in fracture lines along them and give you a good pattern of more or less cubicle chunks of steel. In reality later test showed that they tended to break into only 2 or 3 large chunks of steel and some very fine fragments. This meant that the fragment pattern was not very dense and the chance of casualties due to fragments was much lower than expected even fairly close to the grenade. On the otherhand the big chunks were leathal to a considerable distance (greater than most could throw the grenade).

On another relevant factor does anyone have info on the spalling tendencies of the various armors we are discussing?

Saltheart
Member
Posts: 88
Joined: Sat Jun 18, 2011 1:46 am
Location: New Zealand

Re: Bismarck vs. Iowa

Post by Saltheart » Sat Jun 18, 2011 2:52 am

If there was a situation where the Iowa, soon after comissioning, went for a patrol with a few escorting destroyers in the North Sea in say August 1943 then a fight with Tirpitz might have happened. Lets say Tirpitz is out on it's own on a trip to improve crew training and test the guns a bit. Iowa is basically doing the same and acting as a deterrant in general to Tirpitz but without even knowing Tirpitz is actually at sea too.
An allied flying boat on patrol spots the Tirpitz and informs Scap flow which in turn immediately informs Iowa. Iowa accelerates to 32 knots and races to intercept Tirpitz which doesn't even know Iowa is on it's way. In 3 or 4 hours Iowa arrives having left it's destroyers behind as they couldn't keep up. The Captain of the Iowa can't believe his luck, it's a chance for real glory with his superior ship against a formidable but still inferior Bismarck class battleship.
The two vessels spot each other on radar at about 35,000 yards and the Iowa gets a firing solution pretty quickly. It closes range to 32,000 and fires a full salvo. The captain on Tirpitz finds his ship surrounded by huge fountains of water and immediately realises he's under fire from an American battle wagon and it's huge guns. He figures it must be a North Carolina or South Dakota class ship and decides to try and outrun it. He moves to 29 knots but instead of beginning to open the range he finds the enemy vessel easily maintains it and fires again. This time Tirpitz suffers a near miss. Tirpitz's captain realises this must be a new ship and that running won't work, he also knows he can't penetrate an American ship's thick deck armor while he knows their super heavy shells can easily penetrate his. He's in a terrible situation. Does he keep trying to run, or maybe close the range instead? But with the American being faster it will always control the range so what to do? He decides, before the third salvo is even fired at him that he will use the great range to his advantage. He'll use it to survive.
When the next great flash is seen on the horizon signifying Iowa's third salvo Tirpitz changes course and reduces speed from 29 to 20 knots. This time the shells land nowhere near. Tirpitz plots a course homeward but always waiting for the next salvo from this new opponent. Every time Iowa fires Tirpiz alters speed to between anything as low as 15 and as high as 29 knots, and always changes course too. The accuracy of Tirpitz's own fire isn't affected by this because Tirpitz isn't firing, it's just moving in the direction of Norway.
The captain of the Iowa gets frustrated, his salvo's aren't hitting and the enemy isn't replying to his fire. He's maintaing a great range for good deck punching work but the Germans aren't playing ball! He keeps on firing, salvo after salvo, but the Tirpitz always takes major evasive action. It's captain has no intention of being hit by monstrous 2700 pound shells. At last, after firing a dozen or more salvos into the sea the Iowa captain decides things have to change. He knows if he lets Tirpitz make it home without ever hitting her the allies, and particularly the US Navy itself will think he let a golden opportunity go to waste. His complaining that the Germans wouldn't keep still so he could hit them with his long range shooting simply isn't going to cut it. The Admiral's will demand to know why he didn't then close the range with his speed advantage and force the Tirpitz into battle.
The Iowa moves to 32 knots and closes on Tirpitz. The Germans realise they are about to be overhauled and prepare for battle. Knowing they are pretty much useless at deck penetration with their high velocity light weight fire they hold fire for as long as possible, always concentrating on evasive action as their most important thing. Finally at 18,000 yards with Iowa's shells landing to close for even the wildest evasive action to avoid much longer the German's begin to return fire.
Whose going to win?
I know this is a very long post but i just wanted to show that a Bismarck class battleship doesn't have to engage in a long range fight with an Iowa class one anymore than an Iowa has to have a close range duel with the Germans. There are choices and options of what to do on both sides and simply refusing a gunfight is something Tirpitz can do. In that circumstance an allied captain under great pressure to take the opportunity to dispose of Tirpitz, a ship that was a huge thorn in the allies side in Europe, might end up in a close range slugging match simply in order to be able to have a fight at all.
But again who would win? Would Iowa's stronger turret armor see it through or would Tirpitz's side protection of two walls protecting it's vitals instead of just one see it survive. Maybe a shell from Tirpitz would go through Iowa's belt?

alecsandros
Senior Member
Posts: 4349
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania

Re: Bismarck vs. Iowa

Post by alecsandros » Sat Jun 18, 2011 1:41 pm

Hello and welcome to the forum! \\

Very nice scenario you've presented above. :ok:

For my part, in the given conditions (18000y battle with no previous hit on either ship) the Tirpitz would have the advantage, as hes rate of fire was better, danger space was better and salvo gropuing was better. Practicaly all the sections of Iowa wold be directly vulnerable to 38cm shells, with the only exceptions of the main magazines (well below the waterline and very well protected) and main turrets. The other essential compartments - ploting rooms, con tower, secondary magazines, and their redundancies would be easily destroyable by the German guns. I see Tirpitz vulnerable from the panzer-deck upwards. No section above the panzer deck can withstand 1,22 ton L50 shell hits (with the posible exception of the main communications tower). However, the ploting rooms and communication tubes would be difficult to take out by Iowa, and Tirpitz had more systemic redundancy in its crucial components (for example, main fire control could be commanded from 3 points, 2 of which armored - in Iowa there were 2 such points; the main turrets were 4 - compared to Iowa's 3, etc).

As the electronic equipment was comparable, so was ship tracking, fall of shot spoting and weapons response time. Thus, the probability of an early hit was comparable. However, repeated, consistent hits would be more likely scored by Tirpitz, as hes guns could deliver over 3 shells/minute at 18000y, while Iowa's couldn't deliver more than 2,2 - 2,3. The time of flight of the German shells was smaller, and so was the time needed for aaccurate ranging. ALso, given the tight salvo patters of the 4 x 2 - 38cm gun turrets, the probability of 2 shells from the same salvo hiting the Iowa was greater than the reverse.

Thus, I would see the Tirpitz firing 4 gun salvos for the first 2-3 minutes, while Iowa would be firing 3-gun salvos for ranging. Iowa would straddle first, because it would have 3 individual brackets. However, Tirpitz would score the first hit, becase the danger space of the 38cm shells was greater than in the case of the 40,6cm shells, and the salvos were more tightly packed around the computer-plotted firing solution. After the first observed hit, Tirpitz's captain would order continous rapid fire from all 4 turrets. Iowa would also score several heavy hits, destroying or knocking -out many parts above the panzer deck; however, in 10-15 minutes of battle, at least one of the secondary magazines of Iowa would be hit by 38cm shells, and explode, causing the knocking-out of many on-board systems. Tirptiz's superior rate of fire and faster shell flight woudl slowly take its toll, and Iowa woudl be hit more times than Tirpitz. After about 20 minutes, both ships would be heavil damaged, but Iowa would get the shorter end of the stick, with all sections above the waterline being put out of action, including the command-decks. Also, severe flooding would be recorded in the bow of the ship. The top speed woudl be around 15-18kts. The main turrets woudl be on local control, firing wildly. Tirpitz would be on fire, with maybe 2 main turrets operational At least 2 hits below the armor belt would be recorded, with damage to the stearing gear and 1 turbine-room completely flooded. However, 1 command post would still be active (maybe the aft con tower ?) and accurately direct fire based on the readings of the local-turret directors and plotting of the still-operational plotting rooms (as the main directors and radars would have been previously destroyed).

At this point, both commanders would decide to retreat their badly-damaged ships. Slowly, their range would open, and Tirpitz woudl try to go for Norway.

Iowa's speed would decrease to about 10kts, and it woudl have to be towed back to port repairs would last 1-1,5 years; Tirptiz would get back on its own power and would stay 1 year for repairs. About 1000 casualties on the Iowa and 600-700 on the Tirpitz...

My opinion...

Thorsten Wahl
Senior Member
Posts: 771
Joined: Mon Apr 27, 2009 4:17 pm

Re: Bismarck vs. Iowa

Post by Thorsten Wahl » Sat Jun 18, 2011 3:55 pm

The two vessels spot each other on radar at about 35,000 yards
the american captain wasnt aware about the radar detection equipment on board as Tirpitz was receiving pulses from the US radar. Therfor combat readines was commanded several minutes before a blip was seen on the scope.

in between 35 kyard ans 22 kyard
The Germans realise they are about to be overhauled and prepare for battle. Knowing they are pretty much useless at deck penetration with their high velocity light weight fire they hold fire for as long as possible, always concentrating on evasive action as their most important thing.
according german general tactics no enemy firing on own ship was left unresponsed. The 1st AO decide to shot mixed HE shell and semi AP shell to deal with the large unprotected areas and slightly armored structural parts and waterline of the US ship.
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

Byron Angel
Senior Member
Posts: 1167
Joined: Sun Mar 06, 2011 1:06 am

Re: Bismarck vs. Iowa

Post by Byron Angel » Sat Jun 18, 2011 5:18 pm

alecsandros wrote:Hello and welcome to the forum! \\

Very nice scenario you've presented above. :ok:

For my part, in the given conditions (18000y battle with no previous hit on either ship) the Tirpitz would have the advantage, as hes rate of fire was better, danger space was better and salvo gropuing was better. Practicaly all the sections of Iowa wold be directly vulnerable to 38cm shells, with the only exceptions of the main magazines (well below the waterline and very well protected) and main turrets. The other essential compartments - ploting rooms, con tower, secondary magazines, and their redundancies would be easily destroyable by the German guns. I see Tirpitz vulnerable from the panzer-deck upwards. No section above the panzer deck can withstand 1,22 ton L50 shell hits (with the posible exception of the main communications tower). However, the ploting rooms and communication tubes would be difficult to take out by Iowa, and Tirpitz had more systemic redundancy in its crucial components (for example, main fire control could be commanded from 3 points, 2 of which armored - in Iowa there were 2 such points; the main turrets were 4 - compared to Iowa's 3, etc).

As the electronic equipment was comparable, so was ship tracking, fall of shot spoting and weapons response time. Thus, the probability of an early hit was comparable. However, repeated, consistent hits would be more likely scored by Tirpitz, as hes guns could deliver over 3 shells/minute at 18000y, while Iowa's couldn't deliver more than 2,2 - 2,3. The time of flight of the German shells was smaller, and so was the time needed for aaccurate ranging. ALso, given the tight salvo patters of the 4 x 2 - 38cm gun turrets, the probability of 2 shells from the same salvo hiting the Iowa was greater than the reverse.

Thus, I would see the Tirpitz firing 4 gun salvos for the first 2-3 minutes, while Iowa would be firing 3-gun salvos for ranging. Iowa would straddle first, because it would have 3 individual brackets. However, Tirpitz would score the first hit, becase the danger space of the 38cm shells was greater than in the case of the 40,6cm shells, and the salvos were more tightly packed around the computer-plotted firing solution. After the first observed hit, Tirpitz's captain would order continous rapid fire from all 4 turrets. Iowa would also score several heavy hits, destroying or knocking -out many parts above the panzer deck; however, in 10-15 minutes of battle, at least one of the secondary magazines of Iowa would be hit by 38cm shells, and explode, causing the knocking-out of many on-board systems. Tirptiz's superior rate of fire and faster shell flight woudl slowly take its toll, and Iowa woudl be hit more times than Tirpitz. After about 20 minutes, both ships would be heavil damaged, but Iowa would get the shorter end of the stick, with all sections above the waterline being put out of action, including the command-decks. Also, severe flooding would be recorded in the bow of the ship. The top speed woudl be around 15-18kts. The main turrets woudl be on local control, firing wildly. Tirpitz would be on fire, with maybe 2 main turrets operational At least 2 hits below the armor belt would be recorded, with damage to the stearing gear and 1 turbine-room completely flooded. However, 1 command post would still be active (maybe the aft con tower ?) and accurately direct fire based on the readings of the local-turret directors and plotting of the still-operational plotting rooms (as the main directors and radars would have been previously destroyed).

At this point, both commanders would decide to retreat their badly-damaged ships. Slowly, their range would open, and Tirpitz woudl try to go for Norway.

Iowa's speed would decrease to about 10kts, and it woudl have to be towed back to port repairs would last 1-1,5 years; Tirptiz would get back on its own power and would stay 1 year for repairs. About 1000 casualties on the Iowa and 600-700 on the Tirpitz...

My opinion...

..... Just to pipe up with my completely unsolicited opinion ;-)

IOWA will not be doing any ranging fire. In a late 1943 daylight engagement at 18,000 yards she will open with rapid fire full broadsides under radar ranging and optical train and will straddle on the first or second broadside (official doctrine at the time).

Based upon some previous notes I had taken for an exchange of fire at 22,000 yds (if the Navweap stats for the respective guns are valid), the ballistic differences in gun performance at 22,000 yds range are largely inconsequential -
> ToF difference is < 1 second.
> Striking velocity @ 22,000 yards is about 25 ft/sec greater for IOWA's 16in/L50 than for Bismarck's 38cm/L52.
> AoF/danger space advantage to Bismarck for a 30 ft tall target is about 10 ft in range. But Bismarck is 10 feet wider in beam, which makes their overall target footprints equal for all practical purposes.
> True mean dispersion for the 16in/50 ~20,000 yards is approx 165-200 yards.

- I would would expect that relationship to more or less pertain at 18,000 yards as well.

As regards Rof, the proven rate of fire of the 16in/50 under actual battle conditions was ~1.5 rpm; The stated rate of fire of the 38cm/L52 is said to have been 3 rpm, but I remain skeptical on the grounds that both the German 28cm and 30.5cm guns of WW1 were also stated to have had a rate of fire of 3 rpm, but the only actual evidence we have seen of performance in actual battle was at half that rate (von Hase - Derfflinger @ Jutland). Therefore, more evidence is required before accepting 3 rpm as a component of this combat scenario.

So ...... IMO ..... the ship that hits first andhardest will likely win such an engagement.


B

Post Reply