The vast bulk of the Santisima Trinidad is alluded to with its special rules in Black Seas - she is only ever able to make a single change of direction during her activation. She also requires a successful skill test to be able to travel at full sails.
The trade-off for this deficiency is an arsenal that dwarfs any other ship in the game. Any vessel unfortunate enough to be caught in the broadside is sure to be shredded. You'll want to capitalize on this as best you can, unleashing your initial broadside (which conveys additional bonuses) at the optimal moment.