Bismarck Speed

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Karl Heidenreich
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Re: Bismarck Speed

Post by Karl Heidenreich »

José M. Rico wrote:
dunmunro,
Bismarck was faster than KGV. Get over it
Correct! :ok:
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alecsandros
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Re: Bismarck Speed

Post by alecsandros »

Dear Marc,
Can you tell us what was Tirpitz's speed at 100% load and maximum power ?
Thanks,
Alex
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Herr Nilsson
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Re: Bismarck Speed

Post by Herr Nilsson »

@delcyros

Bismarck’s speed/power-curve ends at 156,000 SHP. OTOH Tirpitz’s speed/power-curve ends at 166,000 SHP. There was a trial run of Tirpitz with 163,000 SHP and 30.8 kts. 30.6 kts would have been about 158.000 SHP. The curves for TP and BS are identical up to ~55,000 SHP. Then BS is faster than TP up to 110,000 SHP. Then TP is faster as BS up to maximum power. It seems to me that BS’s power curve is made by connecting the data of the single trial runs and that there is a very slight double bend. In case of TP they tried to find one curve that fits best between the trial run data.
Regarding the water depth: I personally know of 3 trial runs made at 25 m. The fastest run of them was not more than 30,000 SHP. According to the “Schiffsbuch II” of TP the recommended top speed for 25 m was 21 kts, for 34 m it was 27 kts. Exceeding these speeds would cause severe vibrations and deterioration of steerageway.
All other trial runs I know were made at least at 60 m.

@Duncan

While checking the water depths of the trial runs I found, that some of the runs obviously were made at a little lesser payload. I don’t want to conceal that. But the lowermost payload still was 68%.

@alecsandros

No, I’m sorry. There was no trial run with these parameters.
Regards

Marc

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alecsandros
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Re: Bismarck Speed

Post by alecsandros »

Thank you very much nevertheless, Marc! Great info!

Can you please tell me if Tirpitz's 30.8kts was achieved also at 75% load ?
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Herr Nilsson
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Re: Bismarck Speed

Post by Herr Nilsson »

alecsandros wrote:Thank you very much nevertheless, Marc! Great info!

Can you please tell me if Tirpitz's 30.8kts was achieved also at 75% load ?
According to the document, yes.
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Marc

"Thank God we blow up and sink more easily." (unknown officer from HMS Norfolk)
dunmunro
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Re: Bismarck Speed

Post by dunmunro »

Herr Nilsson wrote:
dunmunro wrote: These loading weights are not well defined, and IMHO do not correspond to actual displacements, but are a percentage of design full load, which was considerably less than their actual full load values.
I'm sorry Duncan, but the loading weights are well defined:


The values for Bismarck according the weight list from April 30th 1940 are:
Displacement without payload: 43356 mt
Displacement with 100% payload: 51395 mt
P.20 of Bismarck's inclining test:

21-July-1940
ship in inclining setup: 42670t
Fluids present: 3059t
M1 and MII fillups: 323
welding transformer: 48
inclining weights: 400
-------------------------
ship empty weight: 38840t
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Herr Nilsson
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Re: Bismarck Speed

Post by Herr Nilsson »

Duncan,

what you're referring to is an inclining test. One needs the exact weight of the ship during this kind of test. Any other weight would be useless for determining the correct metacentric height.

For a speed trial or a fuel consumption trial one needs the weight of the ship in a certain standardized condition. Other weights would be useless for comparison. For the German navy the standardized trial weight was a fully equipped ship with 75% payload for fuel consumption trials and in case of speed trials a fully equipped ship with at least two thirds of payload.
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Marc

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Re: Bismarck Speed

Post by dunmunro »

Herr Nilsson wrote:Duncan,

what you're referring to is an inclining test. One needs the exact weight of the ship during this kind of test. Any other weight would be useless for determining the correct metacentric height.

For a speed trial or a fuel consumption trial one needs the weight of the ship in a certain standardized condition. Other weights would be useless for comparison. For the German navy the standardized trial weight was a fully equipped ship with 75% payload for fuel consumption trials and in case of speed trials a fully equipped ship with at least two thirds of payload.
The inclining test gives us a snapshot of Bismarck's displacement on July 21 1940, and it is pretty obviously nowhere close to:

The values for Bismarck according the weight list from April 30th 1940 are:
Displacement without payload: 43356 mt


being about 4500 tons less, 3 months later, and yet Bismarck doesn't appear much more complete around the time of her high speed trials. I await, with anticipation, publication of the entire speed curves but I am still very puzzled by the displacement figures and I have grave doubts that the trials were run at 43356mt and 66 or 75% of a 8369mt load.
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José M. Rico
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Re: Bismarck Speed

Post by José M. Rico »

dunmunro wrote: I await, with anticipation, publication of the entire speed curves but I am still very puzzled by the displacement figures and I have grave doubts that the trials were run at 43356mt and 66 or 75% of a 8369mt load.
Well, I think you will understand if people don't feel the need to share original material with a person that only reads what he wants to read in order to fit his agenda. I do have some additional data but I won't be publishing that here since I'm not interested at all in solving your grave doubts! :wink:
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Herr Nilsson
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Re: Bismarck Speed

Post by Herr Nilsson »

Hello Duncan,

Here you have the definition of "Zuladung":
Zuladung.jpg
Zuladung.jpg (34.74 KiB) Viewed 3413 times
Important is the word "entspricht".

Here you have the passage from Tirpitz's manual "Schiffskunde" about ballast water.
Ballast.jpg
Ballast.jpg (64.18 KiB) Viewed 3413 times
I see no reason why they shouldn't have used ballast water.
Regards

Marc

"Thank God we blow up and sink more easily." (unknown officer from HMS Norfolk)
dunmunro
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Re: Bismarck Speed

Post by dunmunro »

José M. Rico wrote:
dunmunro wrote: I await, with anticipation, publication of the entire speed curves but I am still very puzzled by the displacement figures and I have grave doubts that the trials were run at 43356mt and 66 or 75% of a 8369mt load.
Well, I think you will understand if people don't feel the need to share original material with a person that only reads what he wants to read in order to fit his agenda. I do have some additional data but I won't be publishing that here since I'm not interested at all in solving your grave doubts! :wink:
No, I don't understand at all. I am not the first person to express concerns about the discrepancy between published shipyard trials data at 43000mt and speed claims for Bismarck and Tirpitz. However, I have taken the time to do a comparative study of speed trials for high speed battleships, and to run Bismarck's data through a ship simulator and then to post my results here. Yes, I am sceptical but scepticism and comparative analysis is always required when evaluating historical material.
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Re: Bismarck Speed

Post by paul.mercer »

Karl Heidenreich wrote:
José M. Rico wrote:
dunmunro,
Bismarck was faster than KGV. Get over it
Correct! :ok:
Gentlemen,
I don't think there is any argument in the fact that an undamaged Bismarck had at least a two knot advantage over the KGv class. However, after the battle with Hood and PoW it seems that Bismarck had to reduce her speed in order to get collision mats over the hole in her bows, even if her speed was reduced to 28 knots it would mean that she had little chance of catching PoW and a long stern chase would not have been advisable bearing in mind that Lutjens could not know what other British forces were awaiting him.
I am not entirely convinced that the fact that one ship has a small speed advantage over another actually has much bearing in an all out battle, pehaps with cruisers and destroyers it would be useful, but if two ships are to slug it out to the end then surely the faster ship would have to regulate its speed to that of the slower one? I would have thought that the ship that was the most manouverable and able to chase shell splashes more quickly would be a better bet even if it was slightly slower.
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RNfanDan
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Re: Bismarck Speed

Post by RNfanDan »

paul.mercer wrote: I am not entirely convinced that the fact that one ship has a small speed advantage over another actually has much bearing in an all out battle..".
Agreed in principle.
I would have thought that the ship that was the most manouverable and able to chase shell splashes more quickly would be a better bet even if it was slightly slower.
Quick manouvring can thwart enemy ranging and perhaps line, but it also plays havoc with a ship's own gunnery, as well as having the undesired effect of slowing the manouvring vessel's progress--not good for either offensive or defensive purposes. A ship with only one or two knots' advantage in speed over its opponent, can lose that advantage with frequent shifts in course. Even if these shifts don't bleed-off much forward speed, the deviations will eventually cause the ship to travel a longer path over a given time, than if the same ship had mainted a straight course, all other things being equal.

I believe that, at reduced ranges, the advantage of sheer speed needs to be significantly greater than a knot or two for the faster ship to get out of trouble (defensively) and is of little added value (offensively).
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delcyros
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Re: Bismarck Speed

Post by delcyros »

The importance of speed has been overblown. A tactically useful edge in speed by ww1 period was 4 kts and everything less was to narrow to qualify a maneuvering speed advantage. This was for speeds in the low and mid 20kts´s and for ranges of 10,000 to 20,000 yard.
In ww2 we have speeds of the high 20´s and low 30´s kts region with distances in between 15,000 and 30,000 yard. SCHARNHORST, IOWA and RICHELIEU have maybe a useful speed edge over SOUTH DAKOTA but all other post 1930´s BB´s are still in the same ballpark to each other speedwise.

Comparisons of top end speeds are fun to make as the figure implies a precision which in practice often bears less relationship with the edge in an enlarged tactical envelope because the precision of the figure does not match precision of the tactical envelope.

French BB´s were fast in calm Seas but notoriously poor in rough weather, so what are You going to weight in more?
dunmunro
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Re: Bismarck Speed

Post by dunmunro »

paul.mercer wrote:
Gentlemen,
I don't think there is any argument in the fact that an undamaged Bismarck had at least a two knot advantage over the KGv class.
We still don't have access to Bismarck's speed/power curve at a specified displacement, and until we do this question remains open. I have posted excerpts from PoW's log proving a speed and corresponding shaft RPM greater then 29 knots just prior to the DS engagement, so a two knot advantage is unlikely regardless.

This isn't just a comparative Bismarck-KGV issue, but represents a huge gap in our knowledge and understanding of the Bismarck class and its true capabilities. I applaud the diligent research which has brought this new information to light, but until it is made public, the question remains unresolved.

Also, I just noticed some new info regarding the Iowa class maximum speed that has been posted on the navweaps site, so the issue of Iowa's maximum speed seems to have finally been clarified.
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