Naval History Forums

I don't understand what Iowa's speed related in any way with Bismarck's one. Bismarck was a battleship, Iowa was an aircraft carrier escort that needs to be fast.

dunmunro wrote: I am not the first person to express concerns about the discrepancy between published shipyard trials data at 43000mt and speed claims for Bismarck and Tirpitz.

I quote myself:

Much more interesting is that Breyer/Koop are citing Groener. There we can find the same table like the "Results of Dockyard Tests for Bismarck at a Displacement of 43,000 tonnes". http://bismarck-class.dk/technicallayou ... inery.html
But the title in Breyer/Koop is a misquotation. Groener writes "Berechnung der Gesamtleistung der Dreiwellenturbinenanlage mit 12 Kesseln auf Grund eines Probefahrtdeplacement von 43000t":
"Calculation of the total power of the three shaft turbine plant based on trial run displacement of 43,000 t".

dunmunro wrote:
........... Also, I just noticed some new info regarding the Iowa class maximum speed that has been posted on the navweaps site, so the issue of Iowa's maximum speed seems to have finally been clarified.

I can't get too worked up about the exact speed of any ship at one particular time - in operations it really depends on the dispacement and hull and machinery conditions as to what could actually be acheived (also if more than one ship was in company it is likely that on most occassions not total top speed would be used, first such that the slower ship could keep up and also to allow a "bit extra" for relative manoevres.

However, back to what you said, I did read the article (thanks) - it didn't mention whether any adjustment was (or should have been) made to correct for depth at the trial course.

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Karl Heidenreich wrote:I don't understand what Iowa's speed related in any way with Bismarck's one. Bismarck was a battleship, Iowa was an aircraft carrier escort that needs to be fast.

The only relationship is that of an unsolved historical problem, but it also provides another point of comparison:

Iowa: 29.31knots at 183.2rpm with 163,400shp @ 56500LT.
and New Jersey:
29.7kn at 186.1rpm with 170,960shp
31.0kn at 203.0rpm with 221,030shp

and 1985 trials:

IOWA was capable of 31kn at 198.2 RPM
and 186,400 shp, @ 56,858 t (55,960 long tons) . (they had different props, for these runs IIRC)

which is interesting.

paul.mercer wrote: I don't think there is any argument in the fact that an undamaged Bismarck had at least a two knot advantage over the KGv class. However, after the battle with Hood and PoW it seems that Bismarck had to reduce her speed in order to get collision mats over the hole in her bows, even if her speed was reduced to 28 knots it would mean that she had little chance of catching PoW

PoW also had its speed reduced to 26kts after the battle, because of the flooding and underwater damage.

PoW's log proves that she was making shaft RPM greater than her nominal full power and logging speeds greater than 28 knots, from 0600 to 0700 May 24, 1941. However, this is OT for this thread topic.

dunmunro wrote:PoW's log proves that she was making shaft RPM greater than her nominal full power and logging speeds greater than 28 knots, from 0600 to 0700 May 24, 1941. However, this is OT for this thread topic.

http://www.hmshood.com/history/denmarks ... amage1.htm

Estimated best speed 27 knots

Again this is OT to this thread, but PoW's log states:

"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

S0 PoW was making much better than 27 knots from 06000 to 0700. I would surmise that Leach was reporting PoW's maximum indefinitely sustained speed in his radio messages to the Admiralty. However, we have discussed this before and it has no bearing on Bismarck's speed trials.

dunmunro wrote:

"0700 listing is 28 miles and 4 tenths at 231.8 rpm

Shaft rpm is not a measure of speed, but only a hint onto which speed the ship was traveling.

For example, a 40.000t ship doing 230rpm will move at "X" speed, while the same ship at 45.000t will have "Y" speed at 230rpm, and Y < X. The main reason is greater water resistance in the second case, because the ship will be "deeper" in water.

That's why indicators such as prismatic and block coefficients exist...

alecsandros wrote:

dunmunro wrote:

"0700 listing is 28 miles and 4 tenths at 231.8 rpm

Shaft rpm is not a measure of speed, but only a hint onto which speed the ship was traveling.

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Yes, and we have two metrics, shaft RPM (231.8)and pitometer log speed (28.4 knots), and they both agree.

Prince of Wales (1941) 28.0 knots at 111,600 shp 1113,148 mhp) at displacement of
42,100 tons (42,776 mt). Full load = 43,786 tons, subtract fuel burned and PoW displaced about 42000 tons at DS.

KGV Class nominal full power = 110,000shp at 230 rpm

Again this is OT.

dunmunro wrote:
Yes, and we have two metrics, shaft RPM (231.8)and pitometer log speed (28.4 knots), and they both agree.

Is there an online source for pitometer the log ?

Richelieu speed:

31.9kts @ 43500t @ 157000shp

Prismatic coefficient Richelieu at 43000tons: 0.58
Bismarck prismatic coefficient at 45.000tons: 0.56
Bismarck prismatic coefficient at 50.000tons: 0.59

alecsandros wrote:
Is there an online source for pitometer the log ?

No, Paul Allen of the HMS Hood website sent me the log entries and I made them public by posting them on several websites, such as here.

The log of PoW is available via the UK archives.

... Sorry to unearth such an old post, but I have been reading increasingly more websites that mention Bismarck's top speed as 30.8kts.

Is this supported by documentation [other than von Mullencheim's book], or is it a simple copy or a reference to Tirpitz ?

30.8 kn
Value is according "Fahrtabellen Schlachtschiff Tirpitz"
the Fahrtabellen data ends at 30,8 kn

30.6 kn
K Amt memorandum report
"Vergleich zwischen Richelieu und Bismarck K-K III ANr. 231-41 G.Kdos., K-K III A Nr. 587-41 G.Kdos. und K-K III A Nr 650-41 G.Kdos"
http://www.kbismarck.com/bismarck-riche ... leich.html

30,1 kn
Speed of Bismarck in speed trials August 1940
also mentioned in the official KM-Drawing "Schlachtschiff F" nur gültig für Panzerstärken
https://photos.google.com/photo/AF1QipO ... fVroHc01_D