Patrick McWilliams wrote:?? So KGV is suddenly almost as fast as Bismarck, i.e. capable of 29.5 knots instead of 28 knots?
>"I think you should spent a little more time researching prior to posting".
Indeed. People in glasshouses need to be careful..... :)
Patrick
It depends on which references one uses. Simple as that. No speed figure is constant nor absolute. At least one RN capital ship was capable of exceeding "stated" speeds by employing overpressure from its boilers, and did so for some time in pursuing its objective.
This does not account for sea-state, water temperature, boiler efficiency (when were they last cleaned?), and a whole host of other niggling conditions that can vary the "official" figures.
Patrick McWilliams wrote:?? So KGV is suddenly almost as fast as Bismarck, i.e. capable of 29.5 knots instead of 28 knots?
>"I think you should spent a little more time researching prior to posting".
Indeed. People in glasshouses need to be careful..... :)
Patrick
It depends on which references one uses. Simple as that. No speed figure is constant nor absolute. At least one RN capital ship was capable of exceeding "stated" speeds by employing overpressure from its boilers, and did so for some time in pursuing its objective.
This does not account for sea-state, water temperature, boiler efficiency (when were they last cleaned?), and a whole host of other niggling conditions that can vary the "official" figures.
During the approach on the morning of the 24th, Prince of Wales log indicated shaft rpm corresponding to a speed of 29kts+
Perhaps the effect of the Arctic waters on a ships speed ?
Patrick McWilliams wrote:?? So KGV is suddenly almost as fast as Bismarck, i.e. capable of 29.5 knots instead of 28 knots?
>"I think you should spent a little more time researching prior to posting".
Indeed. People in glasshouses need to be careful..... :)
Patrick
It depends on which references one uses. Simple as that. No speed figure is constant nor absolute. At least one RN capital ship was capable of exceeding "stated" speeds by employing overpressure from its boilers, and did so for some time in pursuing its objective.
This does not account for sea-state, water temperature, boiler efficiency (when were they last cleaned?), and a whole host of other niggling conditions that can vary the "official" figures.
PoW's log states that she averaged 28.95 knots during the two hours prior to intercepting Bismarck:
"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"
"0700 listing is 28 miles and 4 tenths at 231.8 rpm
Prince of Wales' "...main machinery steamed at overload powers of 128,000 to 134,000 shaft horsepower with no difficulties..."
G&D, Allied Battleships of WW2, p206
Nominal full power for a KGV class was ~110,000 shp at 230 rpm.
It has been explained several times that your graph is not correct, for a number of reasons:
- freeboard and armored freeboard at that displacement would be minimal and the ship incapable of fighting
- Both Scharnhorst AND Gneisenau obtained 32kts+ speeds during various missions.
PoW's log states that she averaged 28.95 knots during the two hours prior to intercepting Bismarck:
... And KGV obtained maximum 27kts in tropical waters.
The influence of water temperature and salinity on max speed is quite significant...
It has been explained several times that your graph is not correct, for a number of reasons:
- freeboard and armored freeboard at that displacement would be minimal and the ship incapable of fighting
- Both Scharnhorst AND Gneisenau obtained 32kts+ speeds during various missions.
It's not my graph as it was the Kriegsmarine that authored it and I did careful research into Scharnhorst's deep displacement and it was well over 40,000 tons.
PoW's log states that she averaged 28.95 knots during the two hours prior to intercepting Bismarck:
... And KGV obtained maximum 27kts in tropical waters.
The influence of water temperature and salinity on max speed is quite significant...
I guess if the KM ran Scharnhorst's trials in tropical waters that would matter, but they didn't and PoW's trials were also run in the North Atlantic and difference between UK water temps and the DS is not enough to matter.
It's not my graph as it was the Kriegsmarine that authored it and I did careful research into Scharnhorst's deep displacement and it was well over 40,000 tons.
It's a theoretical maximum possible displacement in late 1943 and it has nothing to do with actual mission displacement.
What was Duke of York's maximum speed at 45.500 tons ? Or Iowa's speed at 59000 tons ?
I guess if the KM ran Scharnhorst's trials in tropical waters that would matter, but they didn't and PoW's trials were also run in the North Atlantic and difference between UK water temps and the DS is not enough to matter.
Of course, every ship would be influenced. Friedman says the Iowa's could go past 30.7kts in tropical waters.
It's not my graph as it was the Kriegsmarine that authored it and I did careful research into Scharnhorst's deep displacement and it was well over 40,000 tons.
It's a theoretical maximum possible displacement in late 1943 and it has nothing to do with actual mission displacement.
What was Duke of York's maximum speed at 45.500 tons ? Or Iowa's speed at 59000 tons ?
Why would the KM create a speed-power curve for a displacement that had nothing to do with Scharnhorst's actual displacement?
Of course, every ship would be influenced. Friedman says the Iowa's could go past 30.7kts in tropical waters.
In tropical waters Scharnhorst would also slow down, especially since Germany had no tropical territories and did not engineer their steam plants for tropical service. In any climate the ships would retain their relative speeds and a KGV might even gain a relative advantage.
I own an original trial run curve of Scharnhorst with speeds between 11.5 kn and 24 kn. It seems to match the corresponding value range of the curve from the Koop/Schmolke book. The displacement of the trial run was 37,017 mt.
Regards
Marc
"Thank God we blow up and sink more easily." (unknown officer from HMS Norfolk)
Herr Nilsson wrote:I own an original trial run curve of Scharnhorst with speeds between 11.5 kn and 24 kn. It seems to match the corresponding value range of the curve from the Koop/Schmolke book. The displacement of the trial run was 37,017 mt.
That is not the issue,
The issue is: what speed would Scharnhorst attain at 163000shp and 37017mt ? [which is a realistic load, IMHO]
Vic Dale wrote:
The whole point here is that Scharnhorst was a battleship, perhaps not the hardest or hardest hitting, but she was good. She was also a very survivable vessel and despite her beauty, could take a lot of punishment. Her speed meant that she should be able to choose her battles and dominate the battle through tactics. Any advantage the KGVs had over this class could be quickly reduced in unfavourable conditions and the fact still remains that battles are won and lost in 20 minutes. If a KGV was subjected to a 20 minute period of sustained 28cm fire, where she could not adequately reply, she would have to withdraw, or be destroyed. Such unfavourable conditions were often encountered in battle, see Scharnhorst and Bismarck themsleves.
The experiences of both Marschall and Lutjens in war time command of both vessels of this class suggests they didn't entirely share this opinion. True they were operating under very restrictive orders not to engage their enemy for its own sake but the fact remains that for most of their war time careers these ships were the hunted rather than hunters. The main reason for that was inadequate firepower against capital ships. In truth as I have already said they were battlecruisers whose true role in the commerce war was the destruction of cruiser escorted convoys. Battleships they were not. They were not allowed to attack battleship escorts.
In another thread the design of the proposed Dutch Navy battlecruisers by the KM (Design 1047) was by consensus of opinion superior to the Scharnhorst class. Even the Germans called this design battlecruisers, they were less heavily armoured, faster and had an updated version of the 28 cm gun. On the analysis seemingly presented on this thread it seems that the conclusion would be that they would make mincemeat of a KGV; yet not even the Dutch, their eventual owners (had they been built and handed over) didn't expect them to engage their expected enemy capital ships in the IJN.
''Give me a Ping and one Ping only'' - Sean Connery.
Herr Nilsson wrote:I own an original trial run curve of Scharnhorst with speeds between 11.5 kn and 24 kn. It seems to match the corresponding value range of the curve from the Koop/Schmolke book. The displacement of the trial run was 37,017 mt.
That is not the issue,
The issue is: what speed would Scharnhorst attain at 163000shp and 37017mt ? [which is a realistic load, IMHO]
Well, but the curve is possibly not totally wrong except of the displacement.
Regards
Marc
"Thank God we blow up and sink more easily." (unknown officer from HMS Norfolk)
The speed of a steam driven vessel can increase by as much as 2 knots when operating in very could water. So PoW making 29.5 knots on the morning of the 24th of May '41, may have been achieved without greatly over driving the ship.
The KGv's were designed to work at 27.5 knots at standard displacement on normal power and 29.5 knots in the power over load condition. 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. Warm and cold sea water would have the same effect on their respective speeds. So we seem to have a 3.5 knot disparity in the speed of the KGVs and the Scharnhorsts which cannot be eliminated, except by wear and tear, a dirty bottom or battle damage.
Sea trials are carried out with the ship in the condition she happens to be in at the time, light or fully loaded and all variations between. Intricate calculations are carried out to compensate for variations in displacement, so that the speed and power figures are brought down to standard. Almost never does a ship make her trial speeds in the perfect condition.
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.
When leaving harbour one day, Warspite passed too close to a sand bank and silted up her condensers. This reduced her speed considerably until the silt had been removed. With no cold water passing around the condenser pipes, they could not create the required vacuum. I not sure at this time whether this required a trip to the dockyard or whether it cleared over time.
The vacuum in the steam turbine should never be underestimated. Many a junior seaman on Middle Watch would be sent below to heat the watch's soup on a steam drain in the engine room. Heaven help him if he failed to identify the correct end of the turbine as he would quickly find himself transfixed by the sight of the greedy thing guzzling his soup. An aging Petty Officer once told me of the time, when serving as a junior seaman on a Minesweeper, he had put the bucket of soup under the wrong drain. He lost all of the watch's soup and had to be prized out from between the sweep reels with an oar, so that he could be suitably beaten up. Hell hath no fury like a middle watchman robbed of the soup he has been looking forward to. I have at present no information on the effects of soup getting into the feed circulating system of an Admiralty Turbine.
