Was the battleship Bismarck really the best of its time?

[hans zurbriggen]

Thanks Mr. Nilsson!

hans

[Herr Nilsson]

Enjoy

TP 31.7 sm.jpg

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[hans zurbriggen]

Hello Mr. Nilsson, really impressive for Tirpitz, many thanks.

One thing I can't understand is why Hood is "limited" to 27,5 kn (even in May 1941, at operational displacement, she did 29 kn for long time so that it was difficult for PoW to keep up): I would have expected a comparison of two clean hulls, with ship machinery just (re)fitted and under similar load conditions, therefore (assuming Tirpitz reached 31.7 kn at quite light displacement) Hood curves to end at 31 if not 32 kn (even discounting her displacement increase).

If my sources are correct, Hood reached 32.07 kn at trials in 1920 (British practice was to run trials under operational load conditions AFAIK) while her range was 7,500 nm @ 14 kn (close to Tirpitz) and 5,330 @ 20 kn (not far from Tirpitz): also the fuel consumption assumed for Hood is therefore quite strange in the graph.

Do you know how Germans where drawing these graphs (based on which information) ?

hans

[dunmunro]

Hood made 28.8 knots with paravanes streamed (= ~29.5 knots 'clean') on post refit trials in March 1941.

[wadinga]

Hi All,

These power vs speed things always go the same way. In a car the engine rotates at a certain number of rpm, the clutch rotates the gearbox drive gear at the same and an exact ratio of teeth produce certain rpm leaving the gearbox and the wheels rotate, given their circumference to give a specific speed. Not including wheel spin

For ships there is no absolute- Fuel quality and forced draught may affect combustion, boiler and condenser condition affects heat transfer and hence steam generation and its delivery affects turbine efficiency. Even when the propellers spin at the same speed as on a previous occasion hull drag, wave action, wind effect on upper hull and superstructure, forward/aft trim, excessive rudder use to maintain course and many other factors affect speed through the water(STTW). In geographical terms water mass movement eg currents may add or subtract from STTW to give speed over the ground (SOTG).

A Captain may order "revolutions for 27 knots" but that does not mean the ship will necessarily travel at that speed either STTW or SOTG. That's why to maintain formation a "guide of the Fleet" is nominated, they do what they think is 27 knots and everybody else maintains bearing and distance adjusting their revolutions accordingly. Power vs speed graphs are only approximations, and only apply to the day when they were generated.

At the top end of the power range, considerable increases in power deliver ever-smaller speed increments as drag increases with the square law. Overstressing the machinery for a few fractions of a knot more speed might deliver catastrophic machinery failure.

Ship's speed logs are notoriously inaccurate devices, so claims that a ship was travelling at 32 knots or whatever are just that, unless they are on the Measured Mile and can be independently verified. It is notable that Prinz Eugen's dead reckoning chart shows a huge along course error (and quite a bit of cross course) indicating over-estimate of speed, (presumably based on revolutions and/or log) and thus distance covered to the west.

All the best

wadinga

[fsimon]

In regard of the Denmark Straits footage frame rate:

It's very unusal to stick out the tongue like Jasper?? does.
The footage was filmed on 35mm with an Arriflex 35. The standard frame rate was 24 fps, but Lagemann's camera already had the adjusting knob for 18-30 fps.

My DVD-version apparently has a frame rate of 25 fps (PAL-TV). Assuming that the original frame rate in the later part of the film was 18 fps, I slowed down the DVD to ~70%. At that frame rate Jasper doesn't dart his tongue like a snake anymore and Brinkmann's cigar smoke respectively the rate of fire are getting more realistic.

Again, Thank you very much Herr Nilsson.
That is incredible good detailed information.
Watch out, I am doing math in public: So, if I convert the 18 fps to 25 fps (i.e. divide by 0.72) on the minimum firing interval of 24 seconds, I get 33.3333seconds, equaling a maximimum rate of fire of 1.8, which is not much faster than what Washington's 16 inch guns and about the same rate as PoW's 14 inch guns achieved. That is assuming Lagemann's camera most likely was at is slowest setting.
And also thank you for explaining the limiting times of the firing / loading chain.
Best regards
Frank

[Bill Jurens]

Old North American systems used the so-called NTSC composite video frame rate of 29.97 frames per second. As many films were filmed at 24 frames per second, this made conversion difficult -- I know this from experience as I used to run a tele-cine chain, which converted film to television in what was, frankly, a bit of a strange manner, but was OK insofar as it looked pretty OK to the naked eye.

If you are seeing things on the internet, then heaven only knows what the original camera images have gone through, and -- because it's perfectly easy to do these sorts of conversions digitally, then the frame rate of the image you are seeing might basically be almost anything at all. Again, unless you have something in the image that we know runs at a given rate, x, then almost anything is possible. Old move runs 66 minutes, and you have to fit it in 61 minutes? No problem, just speed it up a bit.

The problem is that after this has been done a few times then nobody actually knows what the original frame rate actually was, so careful timing becomes impossible.

It is possible that the original films of the Denmark Strait action still exist in film-form in some archive somewhere, even though this may be a copy. If so, although the image may be degraded a bit, the frame rate will be the same. The problem there, of course, is that in many cases it's difficult to tell what the frame rate actually was, even if set on the camera -- manufacturers spent relatively little time in ensuring that 24 frames per second wasn't actually somewhere between 22 and 26 frames per second depending on how well the (often) spring loaded drives actually worked. In the movie business, this was more important, especially if one were synchronizing sound, e.g. spoken words. If the camera was set not to record sound -- as was usually the case in combat footage -- then less attention was often paid to making sure that nominal frame rates corresponded to actual frame rates. If timing was important, it was usual to superimpose an image of an actual watch on the footage, so the time intervals could be determined quite exactly. That's how we usually did it in the rocket business.

So, although it's possible to roughly estimate the salvo interval from the internet, it usually can't be considered reliable. And, although it's often more reliable to estimate the salvo interval from the actual sprocket-hole driven film, in reality, in most cases the best one can do is come up with a fairly close estimate.

Bill Jurens

[fsimon]

Thank you for the words of caution concerning the video speed, Mr Jurens. The math I did is probably inappropriate.
Similar caution is probably appropriate concerning the max speed of a ship outside of a test environment.
Best regards
Frank

[fsimon]

But it is still fun to discuss the numbers.
I am also curious, how the Germans came up with the graph for Hood in comparison to Tirpitz.

Frank

[Herr Nilsson]

Hello Mr. Nilsson, really impressive for Tirpitz, many thanks.

One thing I can't understand is why Hood is "limited" to 27,5 kn (even in May 1941, at operational displacement, she did 29 kn for long time so that it was difficult for PoW to keep up): I would have expected a comparison of two clean hulls, with ship machinery just (re)fitted and under similar load conditions, therefore (assuming Tirpitz reached 31.7 kn at quite light displacement) Hood curves to end at 31 if not 32 kn (even discounting her displacement increase).

If my sources are correct, Hood reached 32.07 kn at trials in 1920 (British practice was to run trials under operational load conditions AFAIK) while her range was 7,500 nm @ 14 kn (close to Tirpitz) and 5,330 @ 20 kn (not far from Tirpitz): also the fuel consumption assumed for Hood is therefore quite strange in the graph.

Do you know how Germans where drawing these graphs (based on which information) ?

hans

The Germans captured a copy of "The fleet tactical instructions" including various values for different speeds and cruising ranges for several ships respectively ship classes (values for home fleet are dated September 1st 1940, for mediterranian fleet are dated June 26th 1940).
The comparison between Tirpitz and Hood seems to be based on this document. According the translated document Hood achieved "at full speed: full power" a speed of 27.5 kn and a cruising range of 1640 sm.

[fsimon]

This is very interesting information. Where does one find / Where do you, Herr Nilsson, find this kind of information?
best regards
Frank

[wadinga]

fsimon,

Herr Nilsson has frequently come up over the years with stunning original source nuggets from his personal secret goldmine, located.......

But if he told you ...........he'd have to kill you.

All the best

wadinga

[Herr Nilsson]

It's just a matter of a good memory, patience, opportunity, luck and unfortunately a whole lot of money.

[fsimon]

Haha, excellent. This is a fantastic forum. Great personalities, very good information, manners and mood and great fun.
Best regards
Frank

[hans zurbriggen]

Hello Mr. Nilsson,

you write: 'The first series is unit 1-31. That should be FuMG 39G (in case of Bismarck FuMO 23). It is almost confirmed Bismarck got unit 11 and 17 (the third one remains unclear).
The first technical change was made in unit 32 and following (FuMG 40G?= FuMO 27). The whereabouts of the second series until the sinking of Bismarck is well documented. A FuMO 27 is at least debatable or even implausible'.

Which model of radar was on board of Prinz Eugen in May 1941, according to your sources ?

hans