Standard Frames (Measurement)

A "standard frame" is an arbitrary shipbuilding measurement equal to 3 meters. It is, nominally, the on-center distance between the major structural ribs of the ship.

Actual "as built" ship frames (AKA "Engineering Frames") may or may not be exactly 3 meters long, and in areas of high hull curvature, a frame may be much less than 3 meters long, for strength.

Frames, both "standard" and "engineering", are numbered from the bow to the stern.

The difference is that a crew member may direct a passenger to "Deck 4, Frame 23" (and that is prominently marked in corridors for ease of location), but a ship's engineer will go by the actual frame count -- thus when an engineer is directed to a problem at "Frame 23", he is most likely going farther forward than the nominal, standard "Frame 23".

This is confusing only to non-engineers/crew (e.g., civilian passengers) who aren't aware of the difference between a Standard Frame and an Engineering Frame.

A single-passenger stateroom is typically one Standard Frame long. Given the usual location of staterooms in a ship, staterooms are typically single-frame standard modules and are installed in one piece during shipbuilding operations. Since staterooms are provided fully-furnished, and designed as air-tight structures with independent emergency air, water, and electrical systems, this makes it simple to install them even when the ship is being built in vacuum.

Certain other standard shipboard areas, such as wardrooms, messes, etc., are similarly single- or multi-frame pre-fab modular construction.