When a ship is not under command (no one sailing it) it suffers from drift as it goes off course and suffers the whims of the sea.
What would happen would be once a day a random amount is added or subtracted to the heading and the speed (up to a minimum or maximum of course).
The we could have a project on a ship (perhaps as a machine which you work on an indefinate project) which stops this occuring. So sailors actually have to sail their ship now by being on a sailing project.
These "crewed items", like wheels, rigging, oars etc, would need to be crewed by a character to stop the ship from going astray.
Bigger ships would have more crew points to man.
Where there is more crew points, each unmanned crew point would subject the ship to a random deviation (so a ship with three points unmanned would suffer 3 random deviations) It would be possible to sail with a small crew, but harder as constant adjustments would be required.
(perhaps also, course adjustments can only be made on the ships wheel, as a short project {1 hour})
and ships should come with more than one area (or deck), because it seems like a good idea to me and I'm too tired to think of a better reason
