Bismarck Returns to Norway

[dunmunro]

If the Scharnhorsts were capable of 31 knots at standard displacement, under normal power, they too would be capable of the same percentage increase in the power overload condition.

There's a limit to the amount of steam that can be generated and the power curve for Scharnhorst already reflects that limit.

[Vic Dale]

If the Scharnhorsts were capable of 31 knots at standard displacement, under normal power, they too would be capable of the same percentage increase in the power overload condition.

There's a limit to the amount of steam that can be generated and the power curve for Scharnhorst already reflects that limit.

There is a limit to the amount steam a boiler can safely create and that is set at 30% of it's bursting pressure, which is regularly tested hydraulically.

The working pressure is set at 66% of this pressure so there is plenty in reserve for the over load condition. I once discussed this very question with a naval engineer asking what would be the first failure if the safety valves were screwed shut and the engine was permitted to run with no governors. He said the shafts would probably distort.

[Herr Nilsson]

The power developed in a steam driven vessel is provided by steam pressure developed by the boilers, which working at maximum temperature will produce a particular volume of steam. This pressure applied to the inlet nozzles will drive the turbine. However in order for the turbine to generate power efficiently, condensers are provided which not only recirculate feed water, they cool and condense the steam, causing a vacuum at the after end of the turbine. It is the difference between the pressure and the vacuum ends of the turbine which causes it to run as efficiently as possible, developing maximum power. A turbine without a condenser will run very slowly and will not be very efficient.

In very cold water, the condenser works much more efficiently, cooling the steam faster and creating much more of a vacuum, so there is a greater differential between the pressure and the vacuum ends of the turbine, than when working in warmer water.

My question was how you come to the conclusion of 2 knots speed increase.

[Vic Dale]

The actual two knots figure between temperate and very cold water was presented in a detailed account I saw some years ago about Warspite. This may have been in relation to her silting her condensers when she passed to close to a sand bank. I have looked but cannot find the actual reference. This ship was said to suffer badly from "condenseritis" which if they were not working efficiently would reduce the vacuum and slow her considerably.

[alecsandros]

My question was how you come to the conclusion of 2 knots speed increase.

Incidently, the KGV class showed the same 2kts difference in maximum speed: 29kts+ recorded in the North Atlantic, and 27kts+ recorded in tropical waters.
[of course other factors may have been involved, but I find the situation interesting...]

[northcape]

a bit off topic, but i think it is written in roberts' "British battleships 1919-1945" that by the end of the war, the fully laden KGV was not able to steam beyond 26 kts (in the far east). this is not a great testimony to the parsons machinery.

[dunmunro]

a bit off topic, but i think it is written in roberts' "British battleships 1919-1945" that by the end of the war, the fully laden KGV was not able to steam beyond 26 kts (in the far east). this is not a great testimony to the parsons machinery.

Here's trials speed data for HMS Howe:

http://www.sfu.ca/~dmunro/Howe_trial_data.jpg

note that the last set of figures is for Howe only 8 degs north of the equator, at at a displacement of 44,850 tons and she was nearly 9 months out of dock at that time with a foul bottom, yet she still made 27 knots and from her fuel consumption figures it is probable that she had about another ~7 % of reserve power.

[Vic Dale]

If the boilers can produce steam at the right pressure and temperature, and the engines can develop the horse power, there is no reason why a vessel should not make her best speed throughout her life. The only provisos would be if the engines had suffered undue wear, the engineers might, with agreement of the ship's command, place a limit on the maximum revolutions, or if the shafts were thought to be out of alignment or had faulty bearings.

Some of the older vessels will have had armour or equipment added to the original fit and that would increase draught, so reducing speed. Warspite was able to develop her maximum speed of 25 knots, despite her age, during WWII until bomb damage which could not be adequately repaired forced a general reduction in speed.

[alecsandros]

a bit off topic, but i think it is written in roberts' "British battleships 1919-1945" that by the end of the war, the fully laden KGV was not able to steam beyond 26 kts (in the far east). this is not a great testimony to the parsons machinery.

Here's trials speed data for HMS Howe:

http://www.sfu.ca/~dmunro/Howe_trial_data.jpg

note that the last set of figures is for Howe only 8 degs north of the equator, at at a displacement of 44,850 tons and she was nearly 9 months out of dock at that time with a foul bottom, yet she still made 27 knots and from her fuel consumption figures it is probable that she had about another ~7 % of reserve power.

Duncan, that's not the maximum load for late war KGV class. IIRC, the maximum load in late 1944 was ~ 46000 tons.

[dunmunro]

a bit off topic, but i think it is written in roberts' "British battleships 1919-1945" that by the end of the war, the fully laden KGV was not able to steam beyond 26 kts (in the far east). this is not a great testimony to the parsons machinery.

Here's trials speed data for HMS Howe:

http://www.sfu.ca/~dmunro/Howe_trial_data.jpg

note that the last set of figures is for Howe only 8 degs north of the equator, at at a displacement of 44,850 tons and she was nearly 9 months out of dock at that time with a foul bottom, yet she still made 27 knots and from her fuel consumption figures it is probable that she had about another ~7 % of reserve power.

Duncan, that's not the maximum load for late war KGV class. IIRC, the maximum load in late 1944 was ~ 46000 tons.

You're confusing MT (tonnes) with long tons:

(data from G&D):KGV:
(1940) 38,031 tons (38,641 mt) Standard (R&R state 36727 tons)
(1940) 41 ,630 tons (42,298 mt) Trials
(1940) 42,237 tons (42,905 mt) Full Load
(1944) 44,460 tons (45,173 mt) Full Load
Prince of Wales:
(1941) 42,100 tons (42,775 mtl Trials
(1941) 43,786 tons (44,469 mt) Full Load
Duke of York:
(1941) 42,550 tons (43,232 mtl Trials
(1944) 44,790 tons (45,509 mt) Full Load
Howe:
(1942)42,530 tons (43,212 mt) Trials
(1942)43,337 tons (44,032 mt) Full Load
(1944)44,512 tons (45,226 mt) Full Load
(1945)45,226 tons (45,952 mt) Full Load
Anson:
(1942)42,600 tons (43,296 mt) Trials
(1945)45,360 tons (46,088 mt) Full Load

so 44850 tons was only 376 tons less than Howe's 1945 full load.

[alecsandros]

(data from G&D):KGV:
(1940) 38,031 tons (38,641 mt) Standard (R&R state 36727 tons)
(1940) 41 ,630 tons (42,298 mt) Trials
(1940) 42,237 tons (42,905 mt) Full Load
(1944) 44,460 tons (45,173 mt) Full Load
Prince of Wales:
(1941) 42,100 tons (42,775 mtl Trials
(1941) 43,786 tons (44,469 mt) Full Load
Duke of York:
(1941) 42,550 tons (43,232 mtl Trials
(1944) 44,790 tons (45,509 mt) Full Load
Howe:
(1942)42,530 tons (43,212 mt) Trials
(1942)43,337 tons (44,032 mt) Full Load
(1944)44,512 tons (45,226 mt) Full Load
(1945)45,226 tons (45,952 mt) Full Load
Anson:
(1942)42,600 tons (43,296 mt) Trials
(1945)45,360 tons (46,088 mt) Full Load

so 44850 tons was only 376 tons less than Howe's 1945 full load.

I thought you considered G&D an unreliable source regarding KGV class :)

[dunmunro]

I thought you considered G&D an unreliable source regarding KGV class :)

They still have some useful info.

R&R give these weights:

Ship = Deep displacement in 1945

KGV = 44,460 tons

DoY = 44,794 tons

Anson = 45,360 tons

[alecsandros]

Anson = 45,360 tons

I once found a site dedicated to them, and I remember something like 45800 or 45900 for Howe and Anson late war. I'll try to find it.

[Stefan7litre]

Attempting to go back through the Strait would have been bad idea I believe. Engaging in battle with British Ships was a mistake (damage and fuel leak). If I were Admiral Johann Günther Lütjens, I would have played hide and seek a little longer, maintaining radio silence. Then, made my run towards French coast to ensure aerial support of the Luftwaffe. The Bismarck would out run anything the British had at the time.

[alecsandros]

Attempting to go back through the Strait would have been bad idea I believe. Engaging in battle with British Ships was a mistake (damage and fuel leak). If I were Admiral Johann Günther Lütjens, I would have played hide and seek a little longer, maintaining radio silence. Then, made my run towards French coast to ensure aerial support of the Luftwaffe. The Bismarck would out run anything the British had at the time.

Lutjens never wanted to do battle with the British warships. He delayed it for as long as he could.
At the strait, he was confronted by Hood and PoW which were engaging him from the south-east. he could not go west, as he was already near the ice sheet of Greenland, and did not want to go north back in the strait.
As it was on the morning of 24 of May, Bismarck was kept under radar surveillance by HMS Suffolk and it was little she could do to escape the radar lock.