"Battle of the Chesapeake" is a mission in Sequence 11. This mission is made much easier by fully upgrading the Aquila beforehand.
Optional Objectives
Destroy 3 ships with a single broadside
Destroy 2 frigates by firing on their powder stores
Counter Kill 5 Enemies
Objectives
Destroy the Loyalist Reinforcements
Follow your ally to the next encounter
Ram the Man-of-War to board it
Assassinate the ship's captain
Walkthrough
Head on over to the harbor Master in Davenport Homestead. From there talk with him to head off to sea and start the mission.