Bismarck and European battleships vs.US battleships - hull shape and seakeeping qualities.

[TTTT]

Thanks. very interesting!

"This vessel is extremely wet. Even on a calm day with very little wind the weather decks are wet with spray. On this particular day no automatic weapons on the main deck could have been manned and only those on the lee side of the superstructure could have been manned. In fact, it would have been impossible to fight the ship to windward with anything except perhaps turret 2 and upper 5" mounts."

"

[chuckfan3@gmail.com]

Bismarck is also rather wet forwards, leading to the range finder in A turret being unusable. Bismarck’s hull shape as well as overall design probably made it inevitable:

1. She is very wide mid-ships to give her very high initial stability.

2. To propel such a wide hull at 30 knots with a reasonable amount of power require the hull to taper very quickly both to the front and back. Thus while buoyancy midship is high, bounyancy for and aft is likely low. So when the ship pitches, the righting moment provided by incremental buoyancy is small.

3. The desire for better fire distribution led to 4 twin turrets, which takes up more length. The desire to use a low turtle armored deck to improve defence against short to medium range shell fire meant the citadel had to be long anyway to keep the vital bits below the low armored deck. The combination of 4 twin turrets and low armored deck pushed the heavy turrets closer to the ends of the ship. This means the moment of inertia about the pitch axis is large, or it takes more incremental righting moment to stop it pitching.

These combined suggest bismarck would tend to bury her bow rather than ride over waves.

[Herr Nilsson]

Bismarck is also rather wet forwards, leading to the range finder in A turret being unusable.

That's not quite right. Bismarck's range A-turret finder was never installed and the real reason for not installing it later on was the low height above the waterline, which made it rather useless.

Regarding the seakeaping qualities the usual opinion was "“excellent indifferent seagoing vessels with calm, flat pitching and low rolling movements”.

[hans zurbriggen]

Hello Mr. Nilsson,
while I fully agree with you re. Bismarck seagoing qualities, I would just ask why you say that A turret rangefinder was never installed: in all photos, I see its hood in place on A turret (like in all other turrets) until winter 1940. Rangefinder hood was removed from A turret in Hamburg during refit executed between 1940 and 1941.

BS 1940.jpg (29.15 KiB) Viewed 52145 times

BS 1941.jpg (42.17 KiB) Viewed 52145 times

hans

[Herr Nilsson]

The AVKS-report states: "The subsequent installation of a rangefinder in turret A, which was still pending for the time being, can now be definitively omitted."

[hans zurbriggen]

Thank you Mr. Nilsson!
hans

[wadinga]

Hi All,

There are two significant phrases here:

HMS Vanguard proved to be a much better seaboat for rough North Atlantic conditions

excellent [indifferent? ] seagoing vessels with calm, flat pitching and low rolling movements

Herr Nilsson can you clarify whether the contradiction in the latter sentence is the result of translation failure? It must be rated excellent or indifferent, surely? Or does it mean the the ship's performance was "indifferent" to sea state, ie not unduly affected?

Secondly, no sensible evaluation of Bismarck's hull for ocean-going, eg Atlantic, purposes can be garnered from performance in the Baltic Trials which were perforce performed in what is not much more than a land locked lake with very limited wave fetch compared with an ocean.

There is little doubt that the Iowas secured their phenomenal top speed through a radical hull design (which generated some shortcomings) without the need for increasing the power required even further to an excessive degree, to secure those few extra additional knots of speed.

Vanguard benefitted from using comparatively light, secondhand, main armament mounts on a displacement concept for the very heavy quadruple mounts and heavy armour of a KGV.

Byron, quoting Sowell is, of course, 100% correct. Design demands compromise.

All the Best

wadinga

[Herr Nilsson]

@wadinga
Read:
"excellent indifferent [to sea state] seagoing vessels with calm, flat pitching and low rolling movements".

In regard of the Baltic:

Yes, the Baltic is not the Atlantic, but OTOH I don't know any reports stating that Bismarck and Tirpitz had bad seakeeping qualities.

[wadinga]

Hi All,

This is an interesting thread with enlightening contributions from all.

It is of course true that pretty much all major German warships (including Bismarck) had their prows rebuilt with the so-called Atlantic Clipper bow to minimise spray and waves over the foredeck to address the shortcomings of the original design. I would question the observation made earlier:

Bismarck's range A-turret finder was never installed and the real reason for not installing it later on was the low height above the waterline, which made it rather useless.

The designers would have known the planned height above sea surface and evidently considered it adequate and therefore built a housing for a rangefinder, and in any case it is clear the Dora turret was at much the same height and did ship a rangefinder. However the spray factor is IMHO unchallengeable for the forward turret and so a pragmatic removal of most of the housing projection on turret Anton took place during the winter refit 1940-41, leaving a small projecting stump. The same was true for Tirpitz.

Breyer and Skiwiot note that the Scharnhorst's bow was rebuilt twice as the first clipper bow iteration was ineffectual and additional overhang and sheer were required with the anchors moving to the deck edge like Bismarck.

The Iowas, lacking the flat forward deck, permitting unnecessary low elevation forward fire of the KGVs, had a rise in deck level from the forward turret to the prow of nearly 20ft, in order to minimise waves and spray coming inboard, with limited success noted above. The December '44 Typhoon Cobra pitching and slamming wave effects aggravated wear in one of Iowa's prop shafts leading to a need for drydocking. Her sister Wisconsin lost float planes had damaged AA mounts and lost boats. Malcolm Muir (The Iowa Class Battleships) says waves smashed aboard into her No 2 turret.

Vanguard's designers had leant from the shortcomings of the KGV's flat foredeck and put in a deck sheer to give additional freeboard at the prow.

All the best

wadinga

[chuckfan3@gmail.com]

different navies may emphasize different elements of a ship’s behavior at sea in evaluating a ship’s sea keeping attributes. Bismarck’s broad beam gave her very high initial stability, which would decrease the depth of her rolling motion at the expense of increasing the frequency of her roll. German navy appears to have preferred this trade off since before the first world war. But the royal navy commented negatively on high rolling frequency of germany ships, and regarded that to be a sea keeping short coming.

[Bill Jurens]

As a start, I'd begin by examining the curve of sectional areas of each design, plus the movement of the longitudinal center of buoyancy with changes in displacement, plus the initial values, and changes in the longitudinal moment of inertia of the waterplane area.

This is stuff that is perfectly routine to naval architects, but rarely considered by those which haven't studied naval architecture in detail.

It's also worth noting that in many cases when international exercises are undertaken, the OTC tends to select courses and speeds which make his own ships ride the easiest. It's not that one design is essentially 'more seaworthy' than another, but more along the lines that in any give situation of wind and sea, different designs will tend to behave somewhat differently.

Bill Jurens

[dunmunro]

Hi All,

This is an interesting thread with enlightening contributions from all.

It is of course true that pretty much all major German warships (including Bismarck) had their prows rebuilt with the so-called Atlantic Clipper bow to minimise spray and waves over the foredeck to address the shortcomings of the original design. I would question the observation made earlier:

Bismarck's range A-turret finder was never installed and the real reason for not installing it later on was the low height above the waterline, which made it rather useless.

The designers would have known the planned height above sea surface and evidently considered it adequate and therefore built a housing for a rangefinder, and in any case it is clear the Dora turret was at much the same height and did ship a rangefinder. However the spray factor is IMHO unchallengeable for the forward turret and so a pragmatic removal of most of the housing projection on turret Anton took place during the winter refit 1940-41, leaving a small projecting stump. The same was true for Tirpitz.

Breyer and Skiwiot note that the Scharnhorst's bow was rebuilt twice as the first clipper bow iteration was ineffectual and additional overhang and sheer were required with the anchors moving to the deck edge like Bismarck.

The Iowas, lacking the flat forward deck, permitting unnecessary low elevation forward fire of the KGVs, had a rise in deck level from the forward turret to the prow of nearly 20ft, in order to minimise waves and spray coming inboard, with limited success noted above. The December '44 Typhoon Cobra pitching and slamming wave effects aggravated wear in one of Iowa's prop shafts leading to a need for drydocking. Her sister Wisconsin lost float planes had damaged AA mounts and lost boats. Malcolm Muir (The Iowa Class Battleships) says waves smashed aboard into her No 2 turret.

Vanguard's designers had leant from the shortcomings of the KGV's flat foredeck and put in a deck sheer to give additional freeboard at the prow.

All the best

wadinga

KGV's limited freeboard at the bow was due to a naval staff requirement that 'A' turret be able to fire at low elevation directly ahead. Vanguard's bow design was changed when that staff requirement was dropped. To be fair to the Staff requirement, the RN fought at least 3 engagements where battleships were required to fire at very close ranges; Narvik, Bismarck and Matapan.

[wadinga]

Hi Duncan et al,

Indeed the KGV design did conform to the requirement for low elevation dead ahead fire. The action examples you raise are interesting cases but based on WWI experience are IMHO unusual. As a result of its aggressive tradition the RN expected to be chasing a fleeing enemy, but the whole vessel layout meant action would be desired with A arcs open for maximum output and if ranges were short for low elevation it would be possible to manoeuvre to arrange this. Long range ahead fire surely did not require A turret to be able to directly see the enemy since the DCT was doing all the optical work. Interestingly, with the original (WWI) system of sighting hoods on turret roofs, direct ahead (or astern) fire was to be discouraged because of the debilitating blast effect on operators in the lower turret. If KGV had used her A turret at low elevation it would surely have ripped up the deck planking and the light AA, shipped behind the breakwater later in the war, would have been turned to scrap.

The Renown vs Scharnhorst and Gneisenau action in 1940 is an excellent example of a high speed chase where both sides were swinging aside from a desired course in order to fire with both forward and aft armament. On both sides, overdriving the ships hard into heavy seas resulted in flooding of the forward turrets but obviously tactical requirements outweigh sensible seamanship when "push comes to shove".

Seaworthiness for warships is somewhat different than for commercial vessels in that "exigencies of the Service" mean that slowing to reduce pitching or damage in heavy seas may not be an option. Heavily, perhaps over-gunned, German destroyers might overwhelm their British contemporaries in calm seas, but when conditions were boisterous the less top and bow-heavy British vessels, ie more seaworthy, could best their rivals. Admiral Bey sent his powerful Narviks home because of bad weather at North Cape, but British vessels of smaller displacement than their class opponents managed to chase and launch torpedoes successfully.

In matters of naval architecture, our esteemed moderator is of course the supreme arbiter, and I love his suggestion that chosen courses during peace time exercises are selected with regard to friendly rivalry between allies in order to make one's own vessels "look good".

Chuckfan3s observation echoes what many have said here that "Design Demands Compromise" and that different teams emphasise different characteristics. It is interesting that Essex class after rebuild, and later, US carriers emerged with "hurricane bows" rather than the old open deck arrangement.

All the best

wadinga

[Herr Nilsson]

...
The designers would have known the planned height above sea surface and evidently considered it adequate and therefore built a housing for a rangefinder, and in any case it is clear the Dora turret was at much the same height and did ship a rangefinder. However the spray factor is IMHO unchallengeable for the forward turret and so a pragmatic removal of most of the housing projection on turret Anton took place during the winter refit 1940-41, leaving a small projecting stump. The same was true for Tirpitz.
....

The AVKS-report states:

The limited usability of the 10m RU rangefinders in the lower 38cm turrets due to their low line of sight has been demonstrated once again. In principle, for new constructions, the rangefinder equipment in the low turrets can be dispensed with.

[wadinga]

Hi Marc,

In principle gunnery officers would surely like to have as many long baseline rangefinders as possible. The theoreticians at AVKS may say the low mounts have limitations, but Dora in both Bismarck and Tirpitz actually retained theirs and, as we know there was no new construction completed after the latter to apply the AVKS principle to. It appears Bismarck's designers did not listen to what AVKS had to say prompting their "told you so"

has been demonstrated once again

Pragmatically, Dora in both ships probably retained theirs because battle damage concerns promote redundancy. Anton rangefinders in both Bismarck and Tirpitz were suppressed and the projecting housings minimised. From what I can see Scharnhorst and Gneisenau retained rangefinders in both Anton and Dora, despite their low POV, and the flooding out of the former on several occasions in bad weather. AVKS theoreticians might have their opinions but the men who have to go sea and fight their ships (risking their lives) might not always agree. Their practical experience would suggest Anton would be spray covered at battle speeds in anything but the calmest conditions, and might be deleted, but Dora at the same height might be able to contribute something.

And on a practical note, Bismarck killed Hood at not much more than 18,000yds, when even Dora must have been getting a nice stereo view.

All the best

wadinga