Bismarck firing procedures at DS

[Steve Crandell]

Actually the figures I quoted were from Bill Juren's paper on US Fast Battleship gunnery in W.I. Issue 42 #2 and he references the US Bureau of Ordinance Instruction 2-45 pg 41 which has a table listing NPG Dahlgren testing of the Mark 8 Mod 3 FC radar.

[Bill Jurens]

Bismarck turning rates:

This is a re-written (and somewhat shorter) re-post of a memo I wrote about an hour ago, which appears not to have gone through. If any duplication has occurred, please forgive.

At least some of the turning circle information on the Bismarck has survived. There is a fair amount of scatter in the raw data, so the following figures are 'smoothed' approximations. If I have deciphered the original documentation correctly -- German is not my first language -- it would appear that the mean turning rate over the first 90 degrees of a turn was about 3 degrees per second at 7 knots, 1.5 degrees per second at 15 knots, 1 degree per second at 20 knots, and -- via extrapolation -- 0.5 degrees per second at 30 knots.

Bill Jurens

[Herr Nilsson]

For what it's worth:

[Alberto Virtuani]

Hi Marc,
thanks for posting these data. I don't speak German (if you could give us a translation of the row headers, it would be great..... ).
If I "guess-translate" correctly, (hard rudder to starboard) turning time is only available for max 20,5 knots speed and it gives (for 90° turn) 1 min and 24 secs. The turning time looks to be decreasing with speed as obvious. Am I right ?

Thanks in advance for your clarification.

Bye, Alberto

[Alberto Virtuani]

Wadinga wrote: "it is perfectly feasible that the tall white columns, merely the same height as PoW, which we see on the film, are the same ones Jasper identified as his 8" HE. "

Hi Sean,
Jasper said it was very easy to recognize his small water columnss from BS large ones. However, Jasper was even able to spot the fall of the 6" shells from Bismarck with his available powerful instruments from 15000 yards and he did.
The 8mm camera of the PG film, handled manually by the operator, gives us clearly visible splashed much higher than 35 meters (in the frames I have posted), at least 45 meters. No way such large columns can be from 8".
If 8" columns were so high (more than 45 meters and exceeding the ship height), then Norfolk could easily open fire and spot the fall of shells from max distance (30000 yards) as they would have been clearly visible with the APG telescope...... while his GO stated it was impossible.

If you don't want to believe to me, to Steve or to Mr.Jurens data, please try to think and understand why 8" fall of shells cannot be spotted from 30000 yards even through powerful instruments......

Bye, Alberto

[Herr Nilsson]

Hi Marc,
thanks for posting these data. I don't speak German (if you could give us a translation of the row headers, it would be great..... ).
If I guess correctly, (hard rudder) turn angle per seconds is only available for max 20,5 knots speed and it gives a turning time for 90° turn of 1 min and 24 secs. Am I right ?

Thanks in advance for your clarification.

Bye, Alberto

You're right.

Schlachtschiff Bismarck Ergebnisse der Drehkreisfahrten am 4.11 vor Kahlberg Wind 5-6 (280°) Seegang 5 Wassertiefe 65m=
Battelship Bismarck results of the turnig circle runs on November 4th off Kahlberg wind 5-6 (direction 280°) sea state 5 water depth 65m

Nr. des Kreises= No. of [turning] circle

Anlaufgeschwindigkeit=speed of attempt
Anlaufkurs=course of attempt
Ruderlage=rudder angle (Bb=port, Stb=starbord, Hart=hard rudder)
Zeit bis Schiff dreht=time until ship starts to turn
Drehkreisdurchmesser=turning circle diameter

Nach 90°/360° Drehung= after 90°/360°turn
erforderliche Zeit=time required
Mittl. Umlaufgeschwindigkeit=average speed
Fahrtverlust=loss of speed

Größte Krängung=max. heeling

[Alberto Virtuani]

Hi Marc,
many thanks for confirming my "guess-translation" !

Based on the table you posted above and:
1) extrapolating (risky business extrapolation, I know) the data for a full speed turn (around 30 knots) at full rudder....
2) assuming port and starboard turns are the same (I know it's not the case due to the three screws of BS)....
3) assuming the same reduction in turning time that we see from 10 to 20 knots will go on from 20 to 30 knots.....

I would say that the 90° turning time at 30 knots can be something around 1 minute, that is almost perfectly fitting with the 30 secs for a 50° turn to starboard at full rudder as estimated in Antonio's 2005 battle-map (and also matching the data I have for Littorio class battleships, with the same reduction of turning times when speed increases)

Bye, Alberto

[Herr Nilsson]

Alberto,

it's a bit more complex. Bismarck made just 28 knots during the battle and hart rudder wasn't really feasible at higher speed (more than 25 knots I guess) due to torque issues of the machinery. OTOH I think we have to subtract the time between putting the helm and the ship starts to turn.

[alecsandros]

@Herr Nilson
Considering the situation , and some eye-witness reports, it wouldn't be implausible for Bismarck to have gone beyond 30kts at 5:55 in the morning.
Why do you consider her speed at 28kts ? [i.e. have other info surfaced about it ?]

[Alberto Virtuani]

Hi Marc,
I see your points. I know you don't believe BS was capable of more than 28 knots.....I personally think she could.
I was not aware that Bismarck could not put hard rudder at max speed, that is quite strange (Littorio class data are stating the main rudder could be put hard when at max speed, while the auxiliaries must not be touched, in order to get the fastest possible turn).

However, 28 knots and 25° rudder will not change much my "extrapolation", based on your table. If not 30 secs, 40 secs for sure are enough for Bismarck to turn 50° when at full speed.

I do agree with you that the "reaction" time has to be added (15 to 20 secs, always extrapolating.....)

Bye, Alberto

[Herr Nilsson]

@ alecsandros

Because Brinkmann said so (it's admitedly ambiguos phrased) and 28 knots makes a lot more sense. There is no need for 30 knots to catch up with Prinz Eugen.

@ Alberto

No, I own the speed/HP curve of Tirpitz and Bismarck. The original one from 1941 made by the EKK. She could do 30.1 knots. She just could not accelerate fast enough and after her first turn she would have lost a lot of speed as well.

The EKK criticised the limitation of the rudder angle at higher speed as "....military critical...".

[alecsandros]

@Herr Nilson
at the same time, a faster Bismarck would take the lead faster, while also complicating the enemy gunnery solution.

I don't know when Bismarck started to accelerate. If , presumably, the order was given for 30kts or more, and her speed at the time of the giving of the order was 27kts , how much time would be required to attain 30kts ?

[Alberto Virtuani]

Hi Marc,
I have to agree with EKK.... and thanks for letting me know about this limitation.

Re. Bismarck speed I think we have a dedicated thread for that and I agree with you that after the turn BS should have lost some speed, as well as PG.
However, at the beginning of the battle (depending on when Lutjens gave the order) she could have been at a speed around or exceeding 30 knots also due to the very cold water in the DS that would have enhanced the condenser performances. We know PoW did 29 knots during the chase before the battle and this would hardly have been possible for her. The photos taken at the first (or second ) salvo and the confrontation with the PG film distances would suggest Bismarck was catching up with a delta speed of 3 to 4 knot minimum versus PG......

Bye, Alberto

[Alberto Virtuani]

Alberto Virtuani wrote: "Littorio class battleships showed a 360° turn happening at full speed in 3 minutes 50 secs..... "

Hi All,
I have to correct a wrong statement of mine, while I mentioned by memory these figures, I was confusing with the smaller battleships.....

The 360° turning time for Littorio class, at 29,5 knots and full (hart) main rudder only, was 4 minutes and 40 seconds, with a turning lateral deviation of 935 meters.

At 20 knots (to be able to compare with Bismarck data), the time for the same 360° turn was 6 minutes and 35 seconds with a deviation of 885 meters, therefore worse than Bismarck. However also the 20 knots turn was done using the main rudder only. Littorio ship in 1942 established that better turning performances at lower speeds (I don't know if already at 20 knots....) could be achieved by using both the main and the internal lateral rudder, decreasing both the time and the radius of the turn.

(Source: Erminio Bagnasco, "Littorio class battleships 1937-1948").

Bye, Alberto

[Byron Angel]

While not defining the turn performance of Bismarck with 100pct precision, the general nature of capital ship turning behavior approximates the following characteristics: under hard rudder(30-35deg), approximately 1/3 of the original entry speed into a turn is lost by the time 90deg change of heading has been achieved, with speed through the balance of the turn beyond 90deg reducing to and remaining at 1/2 speed.

B