3 . Ship Information

Few of the characteristics are precise and often vary from source to source. This is partly due to how some are measured, but mainly to changes during operation or the career of the vessel. For example:

Warship displacement tonnage can be as varied as load, deep load, average load, legend, normal, and that is before you get into the complexity of gross and other tonnage used to measure merchant vessels.

Launch dates are usually precise, but completion can vary depending on how it is defined. Merchant ships are usually associated with a build year.

Apart from main armament (number of barrels x internal diameter of gun barrel or weight of shell), World War 1 ships often mounted a variety of secondary armament and as the war progressed, more anti-aircraft guns. These could change, often frequently, and few records were kept. As a main role of destroyers was torpedo attack, and for aircraft and seaplane carriers, the number of aircraft that could be flown off from sea or flight-deck, the numbers of these two weapons are included.

Speed in knots is usually the maximum. Ships rarely steamed at high speed because of the disproportionate use of coal or oil fuel. Also speed often dropped over time as vessels and engines aged. Economic cruising speed would be preferred.

Crews are usually quoted, if more than one figure is given, as peacetime, wartime, and as a flagship that additionally carried an Admiral and staff, at least for big ships. These numbers only ever appear to be approximate, with actual crew sizes fluctuating.

Even fates are rarely precise. The cause of a ship sinking are usually known, but sometimes only by post-war research, but times and positions can vary wildly - if your ship is sinking in heavy seas, recording such niceties no doubt gets overlooked. Of course, if a ship disappears without trace, that is another matter. Even sold and broken up dates vary.

In short, ship information is often approximate.