Calculate the amount of the bow and saw some kerfs to match. Make the kerf from the side you wish to close up and only saw thru to the opposite side. This will allow the beam to close up the kerf. Make the necessary cuts where you wish to bend the beam. Have it supported so it will not break and close the gap of the kerf to test for straitness. Glue joint and close to finish.

I would expect the kerf to be made at the start of the bend in each location.