RustyBattleship

Understood but had an emergency to attend to earlier. I only have time to respond to one at a time -- I hope.

The thought of four props vs. three is a valid arguement. But 3 propellers were almost traditional on large German warships to keep their length down to look like they were within Treaty limitations. Going to a fourth propeller would have needed an extra boiler room and an extra engine room. That would lengthen the ship considerably or would eliminate one of the aft turrets.

Let's compare with the three fast Battleship classes of the U.S. We had higher Treaty allowances than most other countries and all Battleships were designed for four propellers. However, the South Dakota class had a serious length restriction but they solved that by stacking the boilers OVER the engine rooms rather than in line.

The North Carolina class had twin keels supporting the shafts of outboard propellers 1 and 4. If I recall, they were 4-blades with the inboards only 3-blades (have to check her last dry dock photos to confirm distracted memory cells).

But on the Iowa class we outdid ourselves, almost unknowingly. We placed the inboard number 2 and 3 shafts in twin keels making a very narrow tunnel to force water through. Those were 5-bladed props with the outboard 1 and 4 shafts supporting 4-bladed props (but slightly larger in diameter to equalize weight and shaft torque).

On top of that, in a hard turn one of the rudders (placed just aft of number 2 and 3 props) would be turned into that force of water coming through the tunnel of the twin keels and really slam that fantail on over. On New Jersey's sea trial she was loaded light but when she did her hard turns at full speed (30+ knots) you had to hang on to something because she heeled pretty fast and pretty far.

On Wisconsin, back in the 50's, they experimented with "Close the Barn Door" stops where both rudders were turned over to local control (in the rudder machinery rooms themselves so they could be operated independently). The the ship would order a full "Crash Back" and a "Close the Barn Doors" which reversed all four props and closed BOTH rudders over the tunnel.

Talk about a panic stop. 57,000 tonnes of Battleship stopping in only 600 feet (less than her length). A normal "Crash Back" of just reversing props takes a mile to come to a stop.

Drawback: Barn Door stops eventually loosened the rudders up and back in the 80's I was ordered to deliver an entire set of rudder plans to Philadelphia while Wisky was in dry dock.

Obviously, our BB's had much more manueverability than the Bismarck class. If an Iowa's rudders were jammed, she had TWO powerful props on each side to try to stay on a straight course. Bismarck only had ONE on each side.

Obviously this fatally affected ship manueverability when the British fleet caught up to him.

Hey! As long as we are imagineering (a term coined by Walt Disney) let's go back a few hours and picture the Bismarck with an Iowa arrangement and number of props. It's added manueverability may have been enough to avoid ANY torpedo from hitting it.

"For want of a nail, a shoe was lost; For want of a shoe, a horse was lost; For want of a horse, a rider was lost; for want of a rider, a message was lost; For want of a message, a Battle was lost; For want of a Battle, the War was lost."

In other words, any change whatsoever in design or strategy would have a quantum effect on the final outcome as so many other things down the line would also be affected.

Just as I pointed out in my theory, having Prinz Eugen split forces from Bismarck reduced anti-aircraft protection. However minor the additional guns of Prinz Eugen delivered, it may have just been the "Lost Nail" to make it too hard for the British planes to make such a lucky torpedo hit.

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smilingassassin

In reguards to Bismarcks triple screw arrangement, I read somewhere (wish I could recall of the source) that her triple screw setup was a liability. During trials it was noted that turning with props only and rudders turned made steering difficult.

As RB stated it did reduce the volume of machinery spaces and it certainly made for a slender hull, Ideal for a fast ship but given Bismarcks twin rudder setup the triple screw feature was still IMO a poor choice.

The twin rudders tended to "funnel" the screws wash, which was good for turning with the rudders but when the rudders where jammed or incapacitated this complicated turning with screws only, particularily if the rudders where turned.

The center screw IIRC would have to be taken offline given the "funneling" of its wash while the outer screws did all the steering. The problem was the two remaining screws where insufficient to turn the ship at a reasonable rate due again to the rudder setup.

Add in the weaker stern construction outside the armored citadel and you have a heavily warped and buckled stern with rudders turned with 3 screws attempting to turn a 50,000 ton ship, already with several holes in her side.

A single rudder triple screw setup or a twin rudder 4 screw setup would have worked better but I think overall given the Bismarcks need for speed a slender hull wouldn't allow for a single large rudder and the larger turning gear it needed.

Dreadnought

Thanks guys was just some ideas I was thinking could have changed the outcome.

I know the Iowas 4 prop shafts counter one another. I was wondering how the German designers justified to offset two rotating props countered by only one in the three shaft arrangement.

Interesting discussion.

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