Bismarck construction flaws

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RNfanDan
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Re: Bismarck construction flaws

Post by RNfanDan »

Dave Saxton wrote:The first Magnetrons were invented in Japan in 1927 by Kinjiro Okabe.
Okabe's work was preceded by Albert Wallace Hull, an American, in 1921. Neither he nor his employer patented it.
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Re: Bismarck construction flaws

Post by Dave Saxton »

Klystrons-

The klystron was not used in German WWII radars contrary to some internet wisdom. The Telefunken centimetric radars used low noise magnetrons for local osscilators instead of Kylstrons. This has lead to some heated debates in radar circles as to why. Didn't the Germans understand Klystrons or didn't they know about them? Some papers published by Hans Hollman in 1943 prove conclusively that the Klystron was known and understood in Germany. Why Telefunken engineers choose to use magnetrons instead for LO's is not known.

The klystron was invented at Stanford University in the USA during 1937, by the research team of the Varian brothers, and Prof Hansen. Unlike a magnetron, the klystron was frequency stable, but it could only produce a fraction of the power of the strapped cavity magnetron. It could, however, make an excellant local osscilator in the receiver, rather than be used to produce high power centimetric waves in a transmitter. Cavity magnetrons make poor LO's because they are so noisey. Sutton in England designed a special klystron to be used as the LO in the receivers of the British centmetric radars. Sutton's Reflex klystron or Sutton Tube was just as important to the development of operation centimetric radar as the strapped cavity magnetron.

The Japanese did not use Klystrons for their 10cm receivers LO's. They used a small magnetron instead.
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Re: Bismarck construction flaws

Post by Dave Saxton »

RNfanDan wrote:
Dave Saxton wrote:The first Magnetrons were invented in Japan in 1927 by Kinjiro Okabe.
Okabe's work was preceded by Albert Wallace Hull, an American, in 1921. Neither he nor his employer patented it.
As I understand it, Hull proposed the idea of using a magnetic field as replacement of the control grid in a standard vacuum tube design. His company (GE) did use these types of vacuum tubes, but not in the same way, or for the same purposes, as radio magnetrons. Strictly speaking this not the same thing as a "magnetron" being used to produce microwave radio emissions. Hull's basic concept did get the attention of Barkhausen at the time when Okabe was one of his graduate students, eventually leading to Okabe's invention.
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Re: Bismarck construction flaws

Post by Dave Saxton »

Dave Saxton wrote: ....... Some papers published by Hans Hollman in 1943 prove conclusively that the Klystron was known and understood in Germany. Why Telefunken engineers choose to use magnetrons instead for LO's is not known.

...........
I now know why the klystron was not used for the LO by Telefunken in their centimetric designs. It was because of Wismar, or the requirement that German radars be frequency agile over a fairly wide range. The klystron is so stable in frequency that it is difficult to change the operating frequency of the reciever. A (relatively) low noise magnetron of low power can be re-tuned more easily.
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Re: Bismarck construction flaws

Post by JtD »

I think a simple solution to the rudder problem would have been to place them further away from the screws. Or give them a different shape. Just to allow for 360° clearance plus a small margin. It's more of a design flaw.
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Re: Bismarck construction flaws

Post by Vic Dale »

JtD wrote:I think a simple solution to the rudder problem would have been to place them further away from the screws. Or give them a different shape. Just to allow for 360° clearance plus a small margin. It's more of a design flaw.
That would be a poor trade off.

The closer the rudders are sited in relation to the screws the better the reaction when the rudder is turned, add distance between screws and rudders, and the rudder loses it's ability to direct thrust to port or starboard.

Turning a ship requires the stern to be moved laterally. The effect of the rudder passing through water at ship's speed is only a small fraction of the effect acheived by redirecting the thrust from the screws, to port or starboard.

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Re: Bismarck construction flaws

Post by RF »

The question of Bismarck's rudder and the situation on late 26th/early 27th May 1941 has been debated very extensively in other threads. The conclusion I am left with from this discussion is that there is no answer to the problem of the rudder jamming in rough seas. Arguably not so much a design problem as a lack of immediate supporting forces.
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Re: Bismarck construction flaws

Post by JtD »

Vic Dale wrote:That would be a poor trade off.

The closer the rudders are sited in relation to the screws the better the reaction when the rudder is turned, add distance between screws and rudders, and the rudder loses it's ability to direct thrust to port or starboard.
So how many % off for moving the rudder away by say, about a meter? How many for two meters?

And what if I was to position them behind the screws, not somewhere in between the screws and at the same time extend them vertically so they cover not only the upper half of the screw?
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Re: Bismarck construction flaws

Post by VeenenbergR »

One solution to the vulnerability of the rudders is to protect them from side hits with steel plates mounted on the hull like stabilizers OR to double the hull plates to protect the shafts.
It reminds me of the German "side skirts" on all their more vulnerable armored AFV's: the PzKw IV's and Stug's.
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Re: Bismarck construction flaws

Post by tommy303 »

I believe that would tend to make the ship even less manouverable and responsive to rudder.

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Re: Bismarck construction flaws

Post by Vic Dale »

I think the only way to fully ensure the integrity of a warship's steering, would be to install stern and bow thrusters, with auxilliary back up in the event of damage and do away with rudders altogether.

A jammed rudder locks the ship's steering, whereas in the event of complete destruction of the thrusters, they could be isolated and steering effected by shafts alone. Internal thrusters would afford maximum protection to the ship's steering system and the outlet grids could be armoured just as funnel uptakes have armoured grids across them.

In the event that external pods were chosen to provide maximum thrust and perhaps rely on them soley for propulsion (in smaller warships)as well as steering, a damaged pod would only add drag and the loss of it's thrust, as opposed to a disasterous rudder-set which ultimately doomed Bismarck.

Armoured skirts could be employed to protect the ship's screws and provide a thrust-tunnel to aid propulsion. whilst the thrusters headed the ship.

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Re: Bismarck construction flaws

Post by hammy »

South Dakota class had a four propeller system . The outer shafts were not hung on the usual shaft brackets , but the gap between the hull and the shaft was filled by a plated fairing from the point where the prop shaft came through the hull bottom as far aft as the thrust bearings immediately forward from the screws . As the inner two props were located forward of the two outer ones this meant they were protected somewhat , either from torpedos coming in from either beam , or possibly grounding damage or damage from running over an awash obstruction .
The rudder in that class seems a little small , given that the hull shape is a bit on the plump side ( the designers were trying to get a shorter hull length than the preceeding North Carolina class , to thicken the armour scheme a bit ) , so these fins MAY have been there to provide a bit of longtitudinal steering improvement ( following tank testing ? ) . More importantly , you have to remember that every extra foot of hull surface area in the water is creating drag and slowing the ship , a vital thing to avoid when you are straining for every fraction of a knot .
Bismark's rudders do look rather bigger than seems to be strictly neccesary .
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Re: Bismarck construction flaws

Post by tommy303 »

I believe you are talking about the shaft skegs. These will improve directional stability, but at the cost of increased drag and probably some maneuverability. If the rudder has been lost completely, the skeg will probably be helpful in maintaining a heading compared to a ship without much deadwood. In the latter case, such as Bismarck, complete loss of the two rudders would likely have rendered her even more uncontrollable, much like an airplane which has lost the entire vertical stabilizer.

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Re: Bismarck construction flaws

Post by hammy »

After Prinz Eugen had her stern blown off , there is a well known picture of her quarterdeck area showing jury-rigged steering being worked from a good old fashioned hand worked capstan .
I've got an old Merchant seamans manual at home , Nicholls seamanship and nautical Knowledge , which shows you how to do it .
Basically , you take a big spar ( one of the big boat booms , is ideal ) and attach one end to something strong at the remains of the stern .
You then lash something big and flat to the outer end ( the merchant service suggest spare water-tight doors ).
You support the spar (to prevent the outer end dropping down vertically) by a guy line running from the outer spar end back and up to the ship , across the top of a sheer-legs which you have set up as vertical as you can get it , and as close to the point above which the inner end of the spar is fixed as you can get it .
the new " Steering Oar " can now pivot from side to side . You then put three turns of the middle of a cable around the capstan before running the two ends out to fairleads or blocks rigged on the quarters . From there the cable ends go out to the ends of the spar and are made fast .
By winding the capstan in either direction the " steering oar " is steadily moved from side to side , and in a controlled way . Of course you cant run a big warship flat out like this , because at speed you would get a fluttering effect which would soon wreck the whole lash-up , but the pic of P E shows her moving at well over a crawl .

In the Bismarks case the stern was still there , so I am a bit surprised that they didnt try to rig out spars from either quarter and simply drag cables with something big on the end ( ships rowboats or just a spars and tarpaulin sea-anchor would do ) . Again , by winding in on one side and out on the other you would vary the drag . It isnt as if materials or man power or expertise or big handling gear wasnt available . The merchant ship , pared down to the bare minimums is far worse off .

I think Captain Lindemanns response " do what you like ; I dont care " is the key , and we are looking at a failure of command and fatalism paralysing positive action by those further down the command chain . Very strange , unless it was black humour and misinterpreted .
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Re: Bismarck construction flaws

Post by Bgile »

That comment was made after many, many hours of trying to control the ship by various methods and failure to do so.
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