Bismarck speed during last battle

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dunmunro
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Re: BS speed - last battle

Post by dunmunro »

Bgile wrote:
These numbers just don't always make sense. Iowa and New Jersey were capable of only 31.5 kts during the Truk run, on 212,000 shp. Yet dunmunro gives Vanguard the same speed on much less power. Odd.
What was their displacement? IIRC, it was greater than 55000 tons at the time. The USN BBs struggled to achieve their design speeds for several reasons, but mainly because they were always severely overweight, a problem that plagued Bismarck as well.
Vanguard's speed figures are from her post war trials and are reported in British BBs (R&R)and again in Allied BBs,(G&D) and I have no doubt that they are extremely accurate.
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Re: BS speed - last battle

Post by dunmunro »

Vic Dale wrote:

The speeds recorded in PoW's log (can you give me a useful URL to this document?) will have been recorded by Pitometer log and as I said earlier, the very cold waters in the Denmark Strait will have given an increase in speed through faster shaft revolutions, though with steam pressure still within the absolute maximum, due to the condensers working more efficiently than they would on the Arran mile.

Vic
PoW's log is unpublished, but Frank Allan of the HMS Hood website was kind enough to provide this data:

"0500- Log: 295.2; Distance Run through the Water: 28 miles and 8 tenths;

True Course: 240; Mean Revolutions per minute: 235.8

0600- Log: No readings taken following action; Distance Run through the

Water: 29 miles and 1 tenth; True Course: Var (various); Mean Revolutions

per Minute: 239" I was given this also "0700 listing is 28 miles and 4 tenths at 231.8

revolutions. " which probably should read in the same format as above.

For reference HMS Howe, on a two hour trial near the Orkneys, in May 1943, made 27.1 knots with 110500shp at 43,500tons @ 227.9 rpm with a foul bottom (9 months out of dock) using land fixes. In Aug 1942 during her 4 hour builders trials she made 27.7 knots with 113457 shp at 42530 tons @ 231.9 rpm with a clean bottom, but using only her log. I would guess that PoW displaced about 42000 tons at 0400 on May 24 1941, and was about 3 months out of dock.
PoW would have run her trials in the winter of 1940/41, so I doubt the water temp was much different, than in the DS.
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Re: BS speed - last battle

Post by Vic Dale »

Firstly, a bulbous bow may help at different speeds and in different ways, but it sets up certain characteristics of it's own. I think it may have helped with endurance at lower speeds largely by reducing pitching in a swell and also by reducing the bow wave. However the bulbous bow was I believe in the experimental stage and such a large bulb on Scharnhorst may have knocked off her maximum speed slightly.

Bismarck carried a bulbous bow, but on a much smaller scale, her hull form may have produced more longitudinal stability than that of Scharnhorst.

SHP does not transmit in water the same way HP does in a car. The interface between the shaft and the sea, is the screw and possibly the choice of screw and the hull form was better in Bismarck than Scharnhorst. You can jack up the engine revolutions but if all you produce is cavitation you will get nowhere fast.

Scharnhorst was built for speed, whilst Bismarck was built for endurance and this is why she carried a slightly reduced power plant, however it seems that the larger hull and differences in hull form favoured the larger ship closing the gap on their speeds.

I think there is a very great difference between the sea temperature off the Isle of Arran and the Denmark Strait. All year round, the British Isles benefits from the Warm Gulf Stream, whereby currents carry warm water across the Atlantic from the Gulf of Mexico. This is one reason why Germany for example can freeze solid as happened in 1940 whilst all ports in the British Isles remained open. The differential could be as much as 25 degrees between Arran and the Denmark Strait, where currents are carried down from the Arctic.

Incidentally PG's war diary says the German squadron went onto 30 knots at 0008 on the 24th and reduced to 27 knots at 0028, so they managed 30 knots for 20 minutes. How close they got to that speed in such a short time, is anybody's guess, but it is certain that it was considered possible.

That figure for Howe using land-fixes may well be suspect. It is one thing to take a bearing, but quite another to gauge distance accurately especially over a 2 hour period. During such a trail the ship will have steamed in one direction only and will not have retraced her track so as to rule out benefit from wind and current. Until the advent of GPS, a bouyed mile was about the only accurate way of gauging a ship's speed.

Figures produced on different trials and even on operations have the possibilty of throwing up al sorts of figures. Scharnhorst is recorded as having made 35 knots at one time! It is possible over ground with a strong current running.

Vic
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Re: BS speed - last battle

Post by dunmunro »

Bismarck's War Diary:

At
May 13
1340 27 knots
May 24
0008 30 knots
0021 27 knots

So, we are both incorrect, and 30 knots was requested for a total of 13mins. Other than that,
the highest speed recorded for Bismarck was 27 knots, in the entire war diary, starting in Aug 1940.

PE's War Diary:
0008 / 0008 hours­
auf 30 sm gegangen.
went to 30 knots.
0013 / 0013 hours­
Schneetreiben, Sichtverschlechterung
Blowing snow, deterioration of visibility
0021 / 0021 hours­
auf 27 sm gegangen.
went to 27 knots.

I would speculate that this speed increase was requested by Brinkman, specific to PE, or was a request by Lutjens specific to PE.
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Re: BS speed - last battle

Post by Vic Dale »

There is no reference to such an order from Fleet.

The fleet battle orders stated two speeds for battle cruising; 24 knots for state 2 and 27 knots for state 1. If you get to look at my consumption chart which I hope to post when I have it in a presentable form, you will clearly see that these are the speeds which favour Bismarck's consumption figures for state 1 and both ships for state 2. The operation was about endurance not speed.

Significantly Lutjens reported to Group West that due to action with PoW the ship's maximum speed had been reduced to 28 knots, so that in itself bespeaks of a much higher speed. Had the reduction been in the order of 1 knot or less it would hardly have been an issue worth reporting.

I think the shortfall in good information about ship's speeds and shp etc for the Km, is due to the loss of documents at the collapse of the reich, rather than failure of the ships to acheive designed and higher speeds.

The Baron agrees with 30.8 knots and though I don't consider him to be an authority on the ship, that figure would probably have stayed with him. Sailors look forward to sea trials because it gives an idea of what the ship is really capable of, excess of 30 knots would stick in the mind as would the failure to acheive it. I am sure also that Junack the engineering Lt would have had a very good idea too - he of all people should know.

Vic
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Re: BS speed - last battle

Post by Bgile »

dunmunro wrote:
Bgile wrote:
These numbers just don't always make sense. Iowa and New Jersey were capable of only 31.5 kts during the Truk run, on 212,000 shp. Yet dunmunro gives Vanguard the same speed on much less power. Odd.
What was their displacement? IIRC, it was greater than 55000 tons at the time. The USN BBs struggled to achieve their design speeds for several reasons, but mainly because they were always severely overweight, a problem that plagued Bismarck as well.
Vanguard's speed figures are from her post war trials and are reported in British BBs (R&R)and again in Allied BBs,(G&D) and I have no doubt that they are extremely accurate.
That is true, but this was true of all battleships during the war, was it not? In the case of the US battleships it was primarily due to the increased AA battery and increased allowance of ammunition for it. I believe other countries did the same thing, although maybe there was greater need in the case of the US ships.
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Re: BS speed - last battle

Post by Lutscha »

Vic Dale wrote:
The Baron agrees with 30.8 knots and though I don't consider him to be an authority on the ship, that figure would probably have stayed with him. Sailors look forward to sea trials because it gives an idea of what the ship is really capable of, excess of 30 knots would stick in the mind as would the failure to acheive it. I am sure also that Junack the engineering Lt would have had a very good idea too - he of all people should know.
So the absence of primary documentation is the proof for 30.8kn?

Once again, the figures of 30.1kn for BS and 30.8kn for TP were extrapolated, her speed trials clearly indicate that it was highly unlikely to achieve a speed over 30kn at full load or at high load.
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Re: BS speed - last battle

Post by dunmunro »

This is a snippet of Tirpitz's war diary from Sportzpalace:

Rohrreißer Überhitzer Kessel Bb 1, weil Material verzundert [verzundern = Eisenoxidbildung by
500 Grad]. Kraftwerk Bb. damit 27 sm/h Höchst=Schiffsgeschwindigkeit; 29 sm/h
Höchstgeschwindigkeit. Instandsetzung dauert voraussichtlich 6 Stunden.
Pipe burst due to overheating in boiler portside 1 because pipe is `burned out' [severe iron oxide
deterioration in the material due to 500ºC + temperature]. Portside powerplant clear for only 27
knots maximum ship speed; 29 knots at flank speed. Estimate repair to take 6 hours.


Note how the port shaft is cleared for 27 knots, but the max speed is 29 knots. Clearly, they are using knots to refer to shaft RPM, when discussing the port shaft, and I suspect that this is true for all the speeds recorded.
BTW, the maximum recorded speed in the Tirpitz War Diary was 29 knots, and that was for a total of 31 minutes.
Here's another snippet:

Kesselgebläse Bb.2.2. ohne Werfthilfe innerhalb 48 Stunden wieder klar. Vorzügliche Leistung
des Kesselpersonals. Schiff wieder klar für Höchstgeschwindigkeit 30,8 sm.
Boiler blower bellows portside 2.2 again on line within 48 hours without assistance from
shipyard. An excellent accomplishment by the boiler personnel. Ship again clear to sail at flank
speed of 30.8 knots.




Yet this cannot be true at any given displacement, sea state, wind state, boiler state, bottom state, etc etc. It can only be regarded as a theoretical maximum power output and shaft RPM and/or boiler pressure and steam volume. During the run to intercept Bismarck Leach signaled to Holland that PoW was capable of 29 knots, but no more was possible without "taking risks" . I would imagine, that Leach had discussed with his chief engineer, PoW's maximum possible speeds under a variety of scenarios, and got an answer along these lines:Given our current bottom state, sea temperature, and boiler state, I can guarantee you 29 knots for about 8 hours, but to go beyond that, I will have to increase the steam pressures beyond the builder's guaranteed safety margin. Based upon trials data, we may be able to produce X RPM to provide X knots for a few hours. In other words, PoW, (and all ships) did not have a fixed maximum speed. It was a continuously changing variable, which is effected by a wide variety of inputs.
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Re: BS speed - last battle

Post by iankw »

At the risk of making myself (a science teacher) look stupid, there is something that has been gnawing away at me for a few days. It is this:

Water is more dense than oil, that's why oil floats on water! So, if the oil in the tanks is burned off and replaced by water the ship's displacement will increase as the fuel level drops. The water replacing the oil has more mass than the oil it replaced, yes? Am I missing something obvious here?

regards

Ian
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Re: BS speed - last battle

Post by Bgile »

iankw wrote:At the risk of making myself (a science teacher) look stupid, there is something that has been gnawing away at me for a few days. It is this:

Water is more dense than oil, that's why oil floats on water! So, if the oil in the tanks is burned off and replaced by water the ship's displacement will increase as the fuel level drops. The water replacing the oil has more mass than the oil it replaced, yes? Am I missing something obvious here?

regards

Ian
Makes sense to me. Not all tanks would be reballasted with water, though. Those that were might not be filled with water on an equal volume.
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Re: BS speed - last battle

Post by tommy303 »

Ian,

The reserve tanks forward would likely not have been ballasted with water as the oil was used up, nor would the bunkers in the double bottom, as the Germans did not like using seawater ballast in fuel oil tanks. Those in the outer compartments which made up the inner boundary of the side defence system, on the other hand, could have been ballasted as fuel was used up, as the inner liquid layer was an essential part of the torpedo defence system. On the whole, however, these were frequently treated as reserve bunkers and the bow and double bottom tanks were normally emptied first before those in the wing compartments.

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Re: BS speed - last battle

Post by lwd »

This may or may not be of interest but using the formula for hulls speed found on wiki and editing dunmunro's chart to accomidate it we get:
Ship length Hull speed
Bismark 792 37.7
KGV 740 36.5
Victorious 710 35.7
Vanguard 799 37.9
Richelieu 794 37.8
VV 770 37.2
Scharnhorst 754 36.8

In regards to Baltic trials no one has mentioned the effects of the Baltic being fairly shallow. I seam to recall reading that sea depth can have a signficant effect on speed (I think ships can go faster in shallow seas but may have got this backward).
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Re: BS speed - last battle

Post by Vic Dale »

Hi LWD.

In shallow water, there is interaction between the ship's hull and the bottom causing the hull to be dargged deep per than usual. This can be seen on U-Tube where Scharnhorst's entire bow is submerged as she surges ahaed.

I also have photo somewhere of Seydlitz with her stern conmpletely submerged as she speeds through the waters around Dogger Bank.

I believe the lack of details of speed trials for Bismarck is down to lack of documentation available to Koop and Schmolke and owes nothing to Bismarck's failure to mearue up to her sister.

A quick look at the full-speed/displacement figures for the KGV class shows relative parity between the ships of identical hull form. So if that works for the KGVs I don't see why we can't accept the same for the Bismarck's.

Vic
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Re: BS speed - last battle

Post by RNfanDan »

German ships running speed trials in the Baltic may suffer from that body of water's comparitive lack of salinity with that of most of the world's oceans.

Briefly, the Baltic is a brackish body of saltwater covered with water from runoffs and the many rivers feeding into it. Most of its high-salinity water is trapped below the lighter, less dense freshwater mix.

Fresh water does not offer the same "buoyancy" as salt water. A ship drawing X number of feet displacement in the Baltic, which varies a bit from its northerly to southerly reaches, will usually draw less draught on a major ocean. Thermal effects notwithstanding, the German ships were likely to be affected in their maximum speeds (slower) in the Baltic than they were in the Atlantic.

In the Great Lakes region of the US, ships outbound on the St. Lawrence will gradually gain freeboard as they approach the Atlantic, while "upbound" vessels will behave in just the opposite fashion--riding deeper as they traverse further into the freshwater lakes. Generally speaking, the deeper a ship rides, the greater its contact surface area against water, and hence its resistance.

Keep in mind, these are generalities and do not account for all variables of course, but I believe the effect of salinity has its place in determining a ship's maximum measured speed, all other things equal. The effects are not by any means drastic, but they have the effect of "making" Bismarck's top speed a bit higher as she steamed through the Atlantic, perhaps as much as a knot or more faster than her Baltic runs allowed.

This has little to do with her speed the morning of May 27, but almost certainly bears on the ship's pre-damage performance and speed through the Denmark Strait, as well as her fuel consumption figures at a given speed.
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Re: BS speed - last battle

Post by Guchi »

dougieo wrote:Hes trying to say that if the Bismarck steamed as fast as she could, eratic course and all she would have survived longer than she did steaming a steady course at 7 knots as she would be a harder target.
Err... I think not. Bismarck's rudders were stuck in a turning position. If she increased speed, all it would do is to send her into a circle.

What the captain was trying to do with a lower speed was to allow the wind and waves to (somewhat) counter the effect of the rudder. Any faster and she would simply respond to the position of the rudders and return to a circle.

Now if you think that a ship turning round and round in a circle has a better chance than what Bismarck historically achieved - that can be debated
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