The new Marine National Facility research vessel Investigator seems really big, but how much does it weigh?

Turns out it’s a lot!!

There are a couple of key weights we need to measure:

Lightship Displacement – 4343 tonnes
This is the amount of sea water the ship displaces without anything on board, like  fuel, water, stores, people, non-permanent scientific equipment. In simple terms, this is what the empty ship would weigh if you put it on a set of scales.

Deadweight – 1550 tonnes 
This is the total amount weight that can be carried on the ship, including fuel, water, stores, people, non-permanent scientific equipment etc.

Maximum Displacement – 5893 tonnes (the sum of the two weights above)
This is the maximum weight the ship is allowed to be, for stability and safety reasons.

The other common weight you may see is Gross Tonnage (GT ) –  6082 tonnes.  This is a volumetric measurement in cubic metres of all internal  spaces within the ship and is used for registration and revenue purposes, in particular port related charges.  This was known as Gross Registered Tonnage (GRT).

At lightship displacement the ship’s draft is 5.1 metres and at maximum displacement the draft is 6.2 metres. The draft is measured from the deepest part of the keel (bottom) of the ship and the gondola sits 1.2 metres below the keel.