Well now that we know they are equipped with carronades they have a whole different purpose. When I played the RTI I used that carronade frigate like crazy til the British sunk it. Because of there firepower I controlled it individually while my ships in line came in and finished the job.

Because of the firepower I'm guessing none of thier cannonballs bounce off the ships making each cannon that much more useful. A carronade frigate can take a fifth rates hull down to 50 percent in 1 shot plus they tend to damage the opposite side of the hull at the same time. just watch as the carronades hit the ship and you'll see some of the cannonballs exiting the otherside.

So use the steamship and run the AI ship line and because it's steam powered run it into the wind to take it to safety while the rest of your fleet mops up.

That was the problem I had with my carronade frigate was it would go in blow wholes in ships and was sunk because of the wind direction couldn't get away from the AI ships in time