A 39 inch board (assuming you only need edge jointing) is a piece of
cake really. Tack or double-side tape a straight board to your stock
(piece of plywood with a factory edge works well). Run that straight
edge against your table saw fence, with the fence set so that the
blade cuts a straight edge on the workpiece. Remove the straight-edge
guide board, flip the workpiece, and rip a straight edge on the other
side. If you have a good quality blade like a Forrest, you may be able
to glue up as-is; If not, a few passes with your #7 (or #6 or even a
jack plane will work fine on a 40" board) and it'll be ready to glue.
Save the router for routing is my advice!
Now, if you don't have a table saw, you can still do it, use a
straight edge guide with a circular saw to cut the straightest edge
you can, then finish up with the hand plane.
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