I'm using rough cut Eastern Cedar to build a pergola. The shape is like two dove tail joints butted together so it's wider in the middle. My layout uses a single, 4@ 2 x 10 beams spanning 13'-9" (which includes a 1'-6" cantilever overhang) attached on top of 6 x 6 posts. 2 beams on one side of structure and 2 on the other is side forming the shape.
My rafters (butted into the beam and lagged screwed) are 2 x 6's spaced 16" oc. My rafters vary in length because of the dovetail layout ranging from 14'-0 to 9'-9" in length. I'll be using 2 x 2's across the rafters 24" oc. All dimensions are true to size, 2 x 10 beam measures 10".
Question: Will my longest rafters sag? Is there a concern of beam torsion or twisting?