Expert System - Sailing Ships by McGoo Software

Based on the responses you have made:

The vessel is probably a Ketch

Conclusion Notes:

This vessel has 2 masts with no square sails. The aft mast is shorter than the foremast with the steering position behind the aft mast.

Expert System Rule:

IF the number of masts on the vessel is 2 only
AND there are square sails on no masts
AND the taller of the 2 masts is the the fore mast
AND the aft mast is fore of the rudder
THEN the vessel is probably a Ketch.

Calculated Certainty Factor: 0.33 = probably