Water is a rather unusual liquid. It gets more dense as it cools, then
at 4 degreesC, it's as dense as it's going to get, and when cooled
further, expands a little again. That's why water in cold lakes
freezes from the surface down. When water turns to ice, it shows its
other strange characteristic - it REALLY expands. That's what does for
your outside copper pipes.

Brian Whatcott

On Tue, 15 Feb 2005 20:56:25 -0500, JR Gilbreath
wrote:

Brian
Are you sure about this. It would seem to me that the cold water
would be less dense. It expands as it freezes.
JR

Brian Whatcott wrote:
On 15 Feb 2005 14:34:42 -0800, wrote:


Brian Whatcott wrote:

After numerous ship losses, Plimsoll legislated a hull mark
in Parliament, the "Plimsoll Line" which accounts for salt and fresh,
warm n cool water, beyond which a commercial vessel must not be
loaded. Unaccounted ship losses were much reduced thereafter.

The difference between salt and freshwater displacement and waterlines
makes sense to me, since the salt increases the density of the water,
right? But why is there a difference between summer and winter?
Thanks, Brent



Warm water is less dense than cold water. Water expands more with
temperature than the metals, so a ship sits lower in hot water.
Moreover, water's rate of expansion increases as the temperature
rises. Another factor: water like oil, gets considerably less
viscous when warm, so a hull might be expected to be livelier, and
maybe the swell higher....

Brian Whatcott Altus OK

As someone has said, the WNA marking is mainly related to weather and is
applied to ships below a certain length above a specific latitude. The
basic idea being to allow some minor additional freeboard as a safety
factor.
There are a number of these draft markings, all the way to Tropical
Fresh which are mainly used when loading at a specific locale and going
to another, to give you a basis as to how deep you can load, as you
can't be below the draft requirements at the next port.
Regarding markings on the side of a barge ..... I've never seen any
denoting displacement, however, reading the draft is a quick and easy
way to know how much cargo (weight) has been loaded.

otn