Bismarck Speed

Discussions about the history of the ship, technical details, etc.

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alecsandros
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Re: Sunday, May 24th anniversay

Post by alecsandros »

dunmunro wrote:
alecsandros wrote:

Bismarck's WLL was 241.5m, waterline beam 35.6m. (ratio 6.78)
AOS Bismarck states 6.71 at 45,951 tonnes and a beam of 36m.
That's the maximum beam, not the waterline beam.
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Re: Sunday, May 24th anniversay

Post by dunmunro »

alecsandros wrote:
dunmunro wrote:
alecsandros wrote:

Bismarck's WLL was 241.5m, waterline beam 35.6m. (ratio 6.78)
AOS Bismarck states 6.71 at 45,951 tonnes and a beam of 36m.
That's the maximum beam, not the waterline beam.
AOS has a body plan drawing, showing that 36m is the WL beam.
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Herr Nilsson
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Re: Sunday, May 24th anniversay

Post by Herr Nilsson »

alecsandros wrote:
dunmunro wrote:
alecsandros wrote:

Bismarck's WLL was 241.5m, waterline beam 35.6m. (ratio 6.78)
AOS Bismarck states 6.71 at 45,951 tonnes and a beam of 36m.
That's the maximum beam, not the waterline beam.
36m is waterline beam.
Regards

Marc

"Thank God we blow up and sink more easily." (unknown officer from HMS Norfolk)
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Herr Nilsson
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Re: Sunday, May 24th anniversay

Post by Herr Nilsson »

@all

Well, maybe anyone can help me. As you know my English isn't very good, but where is written in the Suffolk log that there was any radar contact between 2028 and 0246.

Thanks in advance!

edit:
@Duncan
dunmunro wrote:
Herr Nilsson wrote:

So Bismarck's flank speed is just 28 knots?
43000 tonnes, 138000 mshp = 29 knots (as per the Dockyard test)
48000 tonnes, 154000 mshp = 29 knots (adjusted for displacement)
51000 tonnes, 163700 mshp = 29 knots (adjusted for displacement) 51000 tonnes. Probable max power = 150K mshp, and it follows from this that max speed at 51K tonnes, which is about what Bismarck displaced in the DS, = 28 knots. It is significant that Bismarck's war diary doesn't record any speeds higher than 27 knots.

On which date was this dockyard test?
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Marc

"Thank God we blow up and sink more easily." (unknown officer from HMS Norfolk)
alecsandros
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Re: Sunday, May 24th anniversay

Post by alecsandros »

Herr Nilsson wrote:36m is waterline beam.
G&D Axis Battleships - Bismarck beam 118ft ~ 35.78m.

Not that it makes a difference - the key is prismatic coefficient!
See here:

http://www.navweaps.com/index_tech/tech-004.htm
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Herr Nilsson
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Re: Sunday, May 24th anniversay

Post by Herr Nilsson »

alecsandros wrote:
Herr Nilsson wrote:36m is waterline beam.
G&D Axis Battleships - Bismarck beam 118ft ~ 35.78m.

Not that it makes a difference - the key is prismatic coefficient!
See here:

http://www.navweaps.com/index_tech/tech-004.htm
118 feet = 35.9664 meters :wink:

Otherwise agreed.
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Marc

"Thank God we blow up and sink more easily." (unknown officer from HMS Norfolk)
alecsandros
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Re: Sunday, May 24th anniversay

Post by alecsandros »

Herr Nilsson wrote: 118 feet = 35.9664 meters :wink:

Otherwise agreed.
My appologies.
I was living in a parallel universe where 1ft = 0.303m :)
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Dave Saxton
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Re: Sunday, May 24th anniversay

Post by Dave Saxton »

Yamato's effective max beam below the waterline was 38.9 meters.
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.
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Re: Sunday, May 24th anniversay

Post by dunmunro »

Dave Saxton wrote:Yamato's effective max beam below the waterline was 38.9 meters.
Yes, that's correct. I had to find an underwater plan to see it, however, unlike Bismarck, Yamato's underwater profile doesn't have a constant beam (she is not slab sided like Bismarck or most other modern BBs like KGV) so the average beam is somewhere between 36.9m at the WL to 38.9m (extreme) to 37.4m (bottom).
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Dave Saxton
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Re: Sunday, May 24th anniversay

Post by Dave Saxton »

Bismarck's hull side contour is not constant. And its different from Scharnhorst's.

Yamato's L/B ratio would be about 6.55. About the same as North Carolina. That brings up another interesting comparison, not that such comparisons mean much. North Carolina attained ~27 knots with a L/B ratio of 6.5 using 121,000 shp at a displacement of 46,770 tons. SD had an even less favorable L/B ratio and a bit more displacement, but only required 7% more power to attain 27 knots. It would appear that L/B ratio, and Displacement/Power ratio as primary determinants are widely inconsistent to actual outcomes. I can't see anywhere near a proper comparison by extrapolation coming from such analysis.
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.
dunmunro
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Re: Sunday, May 24th anniversay

Post by dunmunro »

Dave Saxton wrote:Bismarck's hull side contour is not constant. And its different from Scharnhorst's.

Yamato's L/B ratio would be about 6.55. About the same as North Carolina. That brings up another interesting comparison, not that such comparisons mean much. North Carolina attained ~27 knots with a L/B ratio of 6.5 using 121,000 shp at a displacement of 46,770 tons. SD had an even less favorable L/B ratio and a bit more displacement, but only required 7% more power to attain 27 knots. It would appear that L/B ratio, and Displacement/Power ratio as primary determinants are widely inconsistent to actual outcomes. I can't see anywhere near a proper comparison by extrapolation coming from such analysis.
Actually at 46770, NC would be lucky to hit 26 knots (friedman states that the USN estimated 26.4), and Indiana required 135K to achieve 26.7 knots at ~44.8K tons.
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Re: Sunday, May 24th anniversay

Post by alecsandros »

dunmunro wrote:
Actually at 46770, NC would be lucky to hit 26 knots (friedman states that the USN estimated 26.4), and Indiana required 135K to achieve 26.7 knots at ~44.8K tons.
IIRC those were tests in relatively shallow waters, and they are not representative for oceanic performance. The margin is ~ 0.3 - 0.5kts.

Anyway, the idea is that different ships require completely different power levels to propel themselves at given speeds and displacements.

Ex:
Yamato@70.000mt@153000shp = 27.46kts
Richelieu@44.500mt@153000shp = 31kts
Vanguard@51.000mt@135.000shp = 30.3kts
North Carolina@46.000mt@132.000shp = 27kts
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Re: Sunday, May 24th anniversay

Post by lwd »

alecsandros wrote: ... Anyway, the idea is that different ships require completely different power levels to propel themselves at given speeds and displacements.
...
I think you need a conditional in there and if allowences are made for various design features even that may not be accurate.
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Re: Bismarck Speed

Post by delcyros »

I would like to direct attention to a primary contemporary source. The comparison of the BISMARCK class with the french RICHELIEU-class hasn´t been captured in this discussion altough I think it may contribute to the question of the BISMARCK´s speed. It was written in between 1940 and 1941, at one page the author notes that french documents have been captured and forwarded to finalise some data processed in the document, which postdates it to the fall of France mid 1940.
The short working essay was written with persons intimate with the details of the BSIMARCK class but -at first- not intimate with the details of the french RICHELIEU-class so I suppose that they had access to all trial data of the BISMARCK, long lost since.

Note the speed comparison.

There are three different speeds given for these two ships. One design speed for RICHELIEU and BISMARCK each and another speed, which has the designation
"erreicht" which has to be translated with
"achieved [in trials]".

There is no "erreicht" / trial speed given for RICHELIEU but the figure listed in this document for BISMARCK is 30.6 kts.

Doesn´t this substantiate the Baron´s claim for BISMARCK achieveing speeds in excess of 30kts in her trials?
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Re: Bismarck Speed

Post by Herr Nilsson »

delcyros wrote: There are three different speeds given for these two ships. One design speed for RICHELIEU and BISMARCK each and another speed, which has the designation
"erreicht" which has to be translated with
"achieved [in trials]".

There is no "erreicht" / trial speed given for RICHELIEU but the figure listed in this document for BISMARCK is 30.6 kts.

Doesn´t this substantiate the Baron´s claim for BISMARCK achieveing speeds in excess of 30kts in her trials?
The first problem is, that there is no "in trials" in that document. There is only "erreicht"-"achieved". We don't know anything about the conditions (displacement etc). This document is from March 1941 and was an ad hoc report and it was revised in May 1941 in some aspects (different weights for Bismarck) in another document, that's why I'm somewhat sceptical about its reliability. It's good to know that there is that figure and it is mentioned a severeal times in different discussions, but unfortunately it does not prove very much.
Regards

Marc

"Thank God we blow up and sink more easily." (unknown officer from HMS Norfolk)
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