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From: terryr@ogicse.ogi.edu (Terry Rooker)
Newsgroups: sci.military
Subject: Re: Battleship Armor
Message-ID: <1990Jun4.194407.4533@cbnews.att.com>
Date: 4 Jun 90 19:44:07 GMT
References: <16041@cbnews.ATT.COM>
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From: terryr@ogicse.ogi.edu (Terry Rooker)
In article <16041@cbnews.ATT.COM> ames!ames!claris!portal!cup.portal.com!mmm@uunet.UU.NET writes:
>
>    However, I have set the fact out plainly here.  The "match-box" test
>[accompanying picture shows hand holding matchbox between thumb and forefinger
>in its smallest dimension] gives opportunity to visualise clearly the thinness
>of the skin on the intactness of which the battleship depends for her ability
>to remain afloat.
>    Is it so much amiss to liken the hull to a huge bubble?"
>
>or the New Jersey, is like?  Do recent warships have thin hulls like those
>described in this book?
>
Modern ships still have hull plates that are this thick.  If you think
about it it isn't that surprising.  The hull is built on a frame that
is built from the keel.  It is this frame that actually resists the 
pressure of the water and maintains the shape of the hull.  The skin
of the ship only needs to be thick enough to span the distance between
stringers.  On most ships the frames are on the order of 2 feet apart.
The metal skin is only unsupported for that distance.  If you wanted a
monocoque(sp?) type of hull, then it would have to be much thicker, which
is part of the reason that style is not used on ships.

A double bottom is not only expensive, but it takes up a lot of
volume.  In a warship the latter is almost as important as the cost.
Even if there is not a double bottom, tanks and voids on warships tend
to be outboard near the water line to provide some of the advantages
of a double bottom without the expense.  For what it is worth, Soviet
submarines tend to have double hulls, although in this case, the space
is used for ballast tanks.  It is one of the supposed advantages of
Soviet sub design.  There is great fear in the West that the
separation from the actual pressure hull (upto 6 feet!) may render
Western ASW weapons ineffective.

Older ships may not even have 5/8ths of an inch in hull plate.  There
are numerous sea stories about screwdrivers slipping and punching
holes in hulls.  I believe there are cases where the hull was measured
at near, or less than 1/4 of an inch!  Kinda makes the thought of 30
foot swells in a quartering sea kinda scary :-)

-- 
Terry Rooker
terryr@cse.ogi.edu