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The Skeleton Closet

Understanding the Measurement of Ships

I have been asked many times to expalin the meaning of ship measurement so I thought it sensible to include something about this here.

Old Measurement - om this is sometimes seen written as GRT and applies to the measurements of ships built, registered or surveyed prior to 1 January 1836, and in particular to merchant ships of the British Empire.

In om terms a ship was measured for overall length, from fore side of the stem to aftside of the sternpost, and for the beam - outer edge to outer edge across the widest part of the ship. The depth was an inside measurement of the depth of the hold for a single decked vessel, and the total of the space between decks for a multi decked vessel. In old measurement, the dimensions are given in feet and inches - eg. 108' 6" x 22' 3" x 16' 8"

New Measurement - nm this is sometimes seen written as NRT, and came into effect on 1 January 1836 when the method of recording the measurements of tonnage and other dimensions of British merchant ships was changed, giving way to the term "New Measurement".

In nm terms overall length, beam and depth of ships were all measured from the inner edges of the hull ie. inner edge to inner edge from stem to stern for length, inner edge to inner edge at the widest part of the ship for beam, and an overall depth from the top of the gunwales to base of the hold. Dimensions in new measurement terms are given in decimals of a foot, but this is often not quite correct eg. 108.2' x 23.0' x 16.4'.

Tonnage - in some records, ships are recorded giving their overall weight when empty and in others they have the words "burthen" or "burden" or "laden" appearing with the weights. In this case, it means how much the ship weighed when fully loaded. (Although the thought of completely loading a ship with passengers and cargo and plonking it on a set of scales to find it's weight is mind boggling!).

The weight of a ship is usually given in tons, but if it is a French or Norwiegen or Finnish ship, it may be written as tonnes.

Rigging of Ships I am often asked about the rigging of ships, and have included a short expalanation of the most common kinds of rigging found on ships coming to South Australia. It should he noted though, that rigging of ships often changed. A ship might have started a voyage with one sort of rigging, been caught in a strong gale and received damage to her rigging, put into a port somewhere for repairs and arrived at her destination rigged as something else. It should also be noted that port clerks and some harbor masters didn't know what type of rigging was which, and so recorded many ships as being "square rigged" simply because a ship had square sails on its rigging.

This link will show you some examples and explanations of rigging types in sailing ships. [Types of Ships]