getting a demast will allow you to manuever around the ship and come up from the rear where you can broadside rip them apart with grape until you are ready to board. Careful, though, grape will sink a ship too, so when battle permits I only use one ship for this job and leave the others out of firing range.

Any time i notice i have demasted a good ship i immediately move my battle from it to take it out of the fight and to keep my boys from sinking her

however, none of my demasts have been intentional and they are always done with standard balls or the fire from a nearby ship exploding. not sure if chain would increase the likelihood.