Rosselsprung 1942 actual combat

[Byron Angel]

Next topic ..... Tirpitz versus the Montana Class.
Future topic ..... Tirpitz versus Federation Starship Enterprise
Topic in preparation ..... Tirpitz versus the Red Army + Rocky Balboa.

B

[alecsandros]

[Steve Crandell]

I am wondering when you are going to present the information you received about salvo spread on navweaps. Not quite what you wanted, was it?

[alecsandros]

I am wondering when you are going to present the information you received about salvo spread on navweaps. Not quite what you wanted, was it?

Have you read Brad's and Bill's answers ? Because they pretty much confirmed my numbers, Steve...

[Steve Crandell]

I am wondering when you are going to present the information you received about salvo spread on navweaps. Not quite what you wanted, was it?

Have you read Brad's and Bill's answers ? Because they pretty much confirmed my numbers, Steve...

No, they indicated they were about the same. 3 guns/243m and 9 guns/401m at 25hm. In any case, that spread is small enough to get a good chance of hits.

[Steve Crandell]

How is Tirpitz's immune zone at 36,000 yds, where Washington is going to begin hitting her?

It's not imune...

But such long range hits would be chance hits...especialy in Arctic conditions. Washington would also be vulnerable to 38cm plunging fire at such extreme range.

It would be formidable for either ship to hit at such range... [Tirpitz 4-gun salvo pattern would be at least 400 meters wide, and Washington's 3-gun salvo about 500 meters wide. But that would not be the main problem , but evaluating the other ship's future position at the moment of shell impacts... ]

Anyway, I would estimate Tirpitz machinery IZ relatively imune out to 22-23km or so. The funny thing is Washington's IZ would start at about the same range [beyond 22-23km for machinery]

Both ship's main magazines were practically unreacheable by direct hits. I don't know about Washington's secondary magazines ? Were they below the waterline ?

Washington's deck immune zone starts at about 30,000 yds against the flat trajectory guns you have been so proud of. Iowa was able to straddle the IJN DD at over 35,000 yds. Arctic conditions aren't going to make a lot of difference with late war fire control radar. Actual ships are not going to make full rudder turns while trying to close the enemy. They are going to stay on a relatively constant course to give their own guns a good chance to hit, and to close the enemy. Nine gun straddles return hits quite frequently at those ranges. It only takes one to turn the battle around.

And

[alecsandros]

No, they indicated they were about the same. 3 guns/243m and 9 guns/401m at 25hm. In any case, that spread is small enough to get a good chance of hits.

... this would depend on the base , i.e. the average spread of a single-gun firing.

Taking 125yards (114 meters), we have:

3 guns = 276 meters and 9 guns = 455 meters, at 25000 meters.

I agree that the chance of hits existed, especialy as the deflection was quite small - 51 meters for a full 9-gun salvo.

however, we have Tirpitz with:
1 gun firing, ~ 124 meters spread at 25000 meters. The coefficient to be applied for 4-gun salvos at that range was 1.5, if I read the documents correctly.
This would lead to a spread of 186 meters. I do not have info on 8-gun salvo coefficient, but from the web it would appear that a 320 meters long salvo was expected on average at 25km.

===
I'm not saying the tightest salvo is the perfect salvo, but with very good fire control systems, hits were probable even with tighter spreads...

[Steve Crandell]

No, they indicated they were about the same. 3 guns/243m and 9 guns/401m at 25hm. In any case, that spread is small enough to get a good chance of hits.

... this would depend on the base , i.e. the average spread of a single-gun firing.

Taking 125yards (114 meters), we have:

3 guns = 276 meters and 9 guns = 455 meters, at 25000 meters.

I agree that the chance of hits existed, especialy as the deflection was quite small - 51 meters for a full 9-gun salvo.

however, we have Tirpitz with:
1 gun firing, ~ 124 meters spread at 25000 meters. The coefficient to be applied for 4-gun salvos at that range was 1.5, if I read the documents correctly.
This would lead to a spread of 186 meters. I do not have info on 8-gun salvo coefficient, but from the web it would appear that a 320 meters long salvo was expected on average at 25km.

===
I'm not saying the tightest salvo is the perfect salvo, but with very good fire control systems, hits were probable even with tighter spreads...

I don't know where you got your numbers for US ships, but mine was a direct quote from Fischer. 9 guns, 401m at 25hm.

The reason I keep quoting nine gun salvos is that was the best way to determine MPI by radar, and that was what Iowa used at Truk. It is also the best way to insure all guns are at the same temperature from one salvo to the next.

Anyway, Washington has a deck immune zone from 32k yds on down. Most hits at long range are deck hits. That doesn't guarantee devastating hits, but I just don't see your decisive advantage in favor of Tirpitz.

[alecsandros]

Well it's about 0.475% of range at 25km. In the other discussion there is a quote on a study showing 1 gun spreads between 75...175yards, at 20000y, with an average of 125y.

I noticed USN practice was to fire full salvos as much as possible. Casablanca , Guadalcanal.. So collective firing. This reduces the maximum rate of fire bit gives excellwnt ranging results.

The Germans usualy employed 2 and 4 gun salvos, from the data I have.this increased rate of fire and diminished salvo spreads.

I would:t say it would be a decisive, drastic result. But I would expect Tirpitz to hit more often, if 20-25km salvos were possible. Because as the range decreases, the advatages of tighter patterns and angle of fall almost fissapear ( tje 38cm gun had a 100 meter scatter at 20km, and 4 guns 160 meters or so )

[alecsandros]

A follow-up:

It would appear I made some incorrect assumptions earlier, and I overestimated the hit-ratio of the Tirpitz and Washington (the battle that would probably decide the outcome of this hypothetical Rosselsprung)

REvised estimates:

[1] TIRPITZ
Real rate of fire for 4+4 battery fire (all 8 guns fired in 3-4 seconds using collective fire): 2 rounds/minute/gun at 15* elevation (23km). Probable output with fully trained crew: 90%. => actual battery output = 2 rpmpg x 8 guns x 0.9 = 14.4 shells actualy fired/minute. Slowly increases to ~ 2.4 rounds/minute/gun at 15km range for a total of 2.4 x 8 x 0.9 = 17.28 shells actualy fired/minute.

[Note: the individual 2-gun turrets and even 4-gun groups were capable of higher rates of fire, probably above 3 rounds/minute/gun up to ranges of 20km. HOwever, using director fire for all 8 guns would decrease this average.]

Accuracy: excellent, coming from both optical spotting and radar. Integrated fire control (RPC) - operational since 10.Jan.1942. Main radars: 3 sets.

Average 4-gun Salvo spread / Range / terminal angle of fall

210 meters / 30.000 meters / 32*
192meters / 27.000 meters / 27*
180meters / 25.000 meters / 24*
164meters / 23.000 meters / 21*
156meters / 18.000meters / 14*
152meters / 15.000 meters / 10.5*
150meters / 10.000 meters / 6*

Size of the ship: 254 long, 36m wide
Maximum Speed at 163.000shp: 30.8kts at 75% load

[2] WASHINGTON
Real rate of fire for 9-gun battery fire (all 9 guns fired in 1-2 seconds using collective fire): 1.8 rounds/minute/gun at 20* elevation (23km). Probable output with fully trained crew: 90%. => actual battery output = 1.8 rpmpg x 9 guns x 0.9 = 14.58 shells actualy fired/minute. Slowly increases to ~ 2 rounds/minute/gun at 15km range for a total of 2 x 9 x 0.9 = 16.20 shells actualy fired/minute.

Accuracy: very good, coming from both optical spotting and radar. Integrated fire control (RPC) - not operational until late 1943. Main radars: 2 sets.

Average 3-gun Salvo spread / Range / terminal angle of fall

412 meters/30.000 meters/ 45*
320 meters / 27.000 meters / 33*
276 meters / 25.000 meters / 30*
250 meters / 23.000 meters/ 25*
243 meters / 20.000 meters / 20*
210 meters / 18.000 meters / 18*
177 meters / 15.000 meters / 15*
133 meters /10.000 meters / 10*

Size of the ship: 222 meters long, 33 meters wide
Maximum recorded speed: 27kts at 121.000 shp, about 75% load

-----------------------

With this in mind, and especialy because of the near equality of shell output/minute, I must revise my hiting estimate: I would expect an average 1.5 hits made by Tirpitz for 1 hit made by Washington at 23km, slowly decreaseing to 1.2 hits per 1 hit at 15km range.

Of course, an early critical hit by the Washington (like blowing a 38cm turret) would reverse the hit ratios...

[Steve Crandell]

I don't believe the difference in salvo spread. Note that you have the Washington spread actually smaller at close range and twice as large at long range (comparing 3 gun to 4 gun in Tirpitz). Why would the relative salvo spreads change as range increased? Spread would increase of course, but not the difference between the ships.

If a 4 gun spread was really only 210 meters at 30km (over 32,000 yds) you would miss your target most of the time. It's just too small. I think you misinterpreted the data for Tirpitz. It was pretty confusing for me trying to follow all that math over at navweaps, but I'm pretty sure delcryos never claimed salvo spreads that small.

In any case, I respect what I perceive to be your balanced attempt to compare the two ships.

Out of curiosity, did you compare loading angles and elevation rates when considering long range fire?

Tirpitz: LA 2.5 deg, ER 6 deg/sec.
Washington LA 5 deg, ER 12 deg/sec.

[Steve Crandell]

Alecsandros,

Were you using the German 50% dispersion number for salvo pattern length? They are different.

[alecsandros]

Hello,
Well Brad F.provided a rate of fire of 1.84spmg at 27000y obtained during long range battle practice by USS Alabama.
Thorsten showed that German documents mention "firing cycle" of 25 seconds at 10*, 30 seconds for Tirpitz full-gun fire at 15* and 35 seconds for 25*.
Partial salvos (2 or 4 guns) could be fired faster, at around 3 rpm, but during capital ship engagent it woild be probable they would be using 8-gun firings.

However, and this is were things get hazy, the Bismarck experience showed they werr never actualy fieing ALL guns at once but instead they used a procedure which fired them at a slight time delay, creating a "ripple" effect across turret muzzles for a distant observer. A total 8 gun salvo would probably take 3 or 4 sevonds to produce from the first gun in turret Anton to the last in turret Dora.
This is why dispersion was so low - it was practically the dispersion of asingle turret as interference from the blast of the others was minimal.
However, as you noticed this would create a serious ranging problem. Thats why I would expect the Germand to intentiomaly increase the spread. Pissibly by firing offset salvos

[alecsandros]

I did think about loading angles and speed of elevation of tje guns (12*/sec for the 16" and 6*/sec for 15"). But ultimately it's the real deal that matters, i.e.proving ground values and combat statistics. Hence tje 2 rpm figure of Tirpitz and 1.8 for Washington..

[alecsandros]

Alecsandros,

Were you using the German 50% dispersion number for salvo pattern length? They are different.

I uswd the 50% value multiplied by 1.5 which was the coefficient for 38cm turret (salvo) fire.

Also 50% value for 16" guns but multiplied by 2.43