How to cut curves that are parallel?

I have ripped a board on a bandsaw, making an elongated S curve along the length of the board, and now want to make an identical cut 25 mm offset from the original, so that I end up with a snakelike flat piece of board 25 mm wide.



Can anybody please advise on the most accurate way of doing this, in a manner that is consistent and reproducible without much sanding?