"Charlie Morgan" wrote in message news:
Displacement weight, and displacement volume are two diferent things,
Thom.

The "displacement" used for documenting a vessel has to do with freight
carrying
ability, and is determined by computations based on the measured
dimensions of
the vessel, not the displacement weight of the vessel. Some apendages may
not be
counted in the measurements, but in my case, because of the way my boat is
constructed, the entire keel is legally counted as part of one depth
measurement, although it skews the result rather fantastically. The
measurements
are supposed to represent the load carrying capacity of the vessel. The
regulations were created for commercial vessels, and don't do a very good
job of
taking pleasure sailboats into account, so most fin keeled sailboats over
about
25 feet in length qualify under the rules for minimum displacement. I
think they
have to measure to at least 5 tons, or they cannot be documented.

My boat, as an example, weighs about 4500 pounds (2.25 tons), but the
documentation lists it as 6 gross tons, and 6 net tons displacement.

CWM

I don't know if in the sailboat world the term "displacement" has been
"*******ized", but in the commercial vessel world, "displacement" is a
weight and has nothing to do with volume.

Light ship: weight of vessel minus stores, cargo, ballast, fuel, water.
Deadweight tonnage: weight of cargo, stores, ballast, fuel, water vessel is
or can carry.
Displacement tonnage: Add Lightship and deadweight tonnage together to get
actual weight of vessel at any given time.

Gross and net tonnage are volume tonnages and have nothing to do with
weights.

otn