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From: budden@manta.nosc.mil (Rex A. Buddenberg)
Newsgroups: sci.military
Subject: twin screws
Message-ID: <6343@cbnews.ATT.COM>
Date: 8 May 89 01:48:58 GMT
Sender: military@cbnews.ATT.COM
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From: budden@manta.nosc.mil (Rex A. Buddenberg)
Keyword: Re: Iowa Maneuverability


Twin screws do not have shafts locked together.  The primary
reason for twin screws (or 3 like icebreakers or 4 like BBs)
is survivability through redundancy.  Using a single reduction
gear would introduce a single point of failure.

Backing down on the inside shaft(s) in a turn certainly cuts the
turning radius -- all the way to 0 if you want to.  Trouble is that
you kill your way when you do and in WWII, tactical speed under
fire still meant a lot.  So if you see a BB turning inside a DD
radius, the DD is probably using 5 degrees rudder.

BBs were often used in the Pacific as ainti-air batteries close
to the carriers.  So both would be inside the escort screen, but
the main battery would not be in action at all; there's enough
real estate on deck to put lots of 3 and 5" guns to pop away
at aircraft.  Picture the BB conning officer sticking a few hundred yards
away from a CV in a hot fight with both at 30 knots.

Rex Buddenberg

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