Bow Trivia question #34: When is it OK to use a board whose ring lines run off the back at an angle of several degrees? PS: Knowing this will reduce board prospecting from the typical 50 or so to 30 or so.
Answer: Note that ring lines on the back of a bow made from a perfectly straight-ringed board will appear to run off at an angle of several degrees, because the bow tapers in width from grip to tip.
Picture a 3" x 72" board with a ring line starting at the corner of one end, running straight to the other end's opposite corner. There are two perfect bows hiding there: Lay them out side by side, parallel with the ring lines and they'll each be as if made from a board with perfectly straight and parallel-with-the-board ring lines.
If the ring lines are straight but run off at a slightly greater angle you might get just one bow from it.
If you happen to have access to TBB-2 the principle here is illustrated on page 37.
