Those big black ants are generally not looking for your food. They are carpenter ants. They like to eat rotting wood. Google "carpenter ant bait". there are specific baits for them. Apply to areas where they are climbing up into the trailer (cords, tires, stabilizers, etc). Also make sure there are no tree limbs touching your trailer. They will use these as a bridge to get to the trailer. And ... they will fall off of branches above your trailer. Add some bait up there for those "dropping in" for dinner.