D&D 3.0: Tales from Mystara
The cog is the basic medieval-era sailing ship. It is a single-masted sailing ship with around, sturdy hull. It has a partial deck (the waist of the ship is not decked over, but the ends are) and raised bow and stern platforms that are open, as opposed to being enclosed like a true forecastle or sterncastle. It is seaworthy, but not very handy in adverse winds.
Nefs, roundships, or knorrs use these same statistics. A knorr or roundship also has an oar speed of 5 ft. in addition to the sailing speed.
Cog: Colossal vehicle; Seaworthiness + 2; Shiphandling – 2; Speed wind x 20 ft. (poor); Overall AC – 3; Hull sections 16 (sink 4 sections); Section hp 80 (hardness 5); Section AC 3; Rigging Sections 1; Rigging hp 60 (hardness 0), AC 1; Ram 4d6; Mounts 1 light and 1 heavy; Space 40 ft. by 20 ft.; Height 10 ft. (draft 10 ft.); Complement 20; Watch 4; Cargo 40 tons (Speed wind x 10 ft. if 20 tons or more); Cost 6,000 gp.