Cog

Cogs are simple ships with one fixed square sail, flat shallow draft and high sides. Cog can use oars but most of them relay on stern-mounted hanging central rudder to control ships directions. Cog is simple and cheap seafaring vessel which makes it good vessel for trade and transportation but its cheap simplicity comes with many disadvantages and comebacks.
Main advantage of a cog is its cheapness and simple production which makes them favored by poorer or greedier merchants. Capacity can vary but the biggest cogs can carry up to 200 tons which allows bigger cargo. Cogs carrying capacity is not is only advantage its high sides makes boarding hard making it easier protecting itself against pirates and makes them into decent warship by placing towers at for and aft of the ship and manning it with archers. Cogs flat draft also allowed them to settle flat in harbour, making them easier to load and unload.
One of main disadvantages of a cog is its fixed square mast, it makes cogs highly immobile and very dependent on wind. This immobility makes them easy pray for more mobile ships, this makes cog a risky ship to trade with and also limits its uses to war to transporting troops or being a immobile tower ship. Ships thin draft also makes it easily sinkable in stormy weathers, this combined with fixed square mast makes this ships completely useless in open seas and areas with strong wind. This limitations forces cogs to sail by coasts or in inner seas. Ships simple hull and lack of mobility also makes it very vulnerable to ramming.

Speed

3-5 knots (depending on wind)