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Admiral_Of_The_Fleet

French subs go faster in reverse

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After reading on this forum about submarines coming into the game, I was amazed that the Dev's have now started to go back on thier words.

when I remember them stating in a live video recording that under no circumstances will there ever be submarines in the game.

 

...Which brings me to my post in question...

French subs go faster in reverse

 

It's actually a peculiarity of hydrodynamics. Believe it or not, a tractor-type propellor gives higher propulsion efficiency per SHP than a conventional "pusher" type.

The mathematics are very involved, but it boils down to the fact that a screw can't create a (thrust-sapping) cavitation zone in its wake if there's already something solid there (i.e., the hull).

The reason U.S. and UK subs can't take full advantage of this is that their screws (patrol or speed) or pumpjets are optimized in blade shape, etc., for forward movement, plus the fact that sustained reverse RPMs cause excessive wear on their shaft drivetrains.

The turbo-electric system used by the French mandates a reversible-pitch propellor to go astern (you can run an electric motor backwards, but the prop is less aggravation), so they don't suffer the mechanical penalty of a direct-drive sysytem when going full astern.

The U.S. submarines Glenard P. Lipscomb (SSN-685) and Tullibee (SSN-597) also had TEDS (Turbo-Electric Drive System), and exhibited this unusual characteristic to a lesser degree (they had reversible motors instead of reversible-pitch screws).

USS Glenard P. Lipscomb (SSN-685) - US Navy's second submarine to use turbo-electric drive after USS Tullibee (SSN-597)

TMwTzYz.jpg

 

USS Tullibee (This photo was probably taken shortly after her commissioning in 1960. The distinctive shark-fin domes are for the PUFFS sonar system).

ISBQ0af.jpg

 

The main reason we don't use tractor-type screws on submarines is that it would cause a direct design conflict with optimum placement of the sonar arrays (i.e. in the bows). And the main reason we don't use TEDS very much is that the system is inherently more finicky than the straight steam-turbine drive, resulting in increased maintenance cycles and cost and (in some cases) decreased reliabilty. (Tullibee spent so much time in dock with engineering problems that she was known around Newport News as "Building 597".)

 

So in theory we should all go down the french line head straight towards the enemy fire some fish at them and run away backwards whilst she is reloading ready to fire at them without turning around

 

 

Edited by Admiral_Of_The_Fleet
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Unbenannt.thumb.png.bcef08cfedbe281f1f9ca2e026a379ef.png

Is this written with some sort of invisible ink where I need to hold a lighter against the screen to make it visible?

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I suppose that's one way to keep most of the torpedo tubes pointed at the enemy.

On 2/19/2020 at 12:16 PM, Admiral_Of_The_Fleet said:

 

TMwTzYz.jpg

There's just something about a submarine putting on a condom that makes it look scandalous.

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