Originally Posted by
Scott T Smith
Clay, thanks for the photo's; they indeed do tell the story of what is happening and why. If you look at the view of the end grain, you can see where the board was pretty much perfectly quartersawn - at least in terms of the view from the end. If you look at the top of the board you can see where the grain on the right resawn side shows curvature, which also tells you that this was the pith side of the board.
Looking at the photo on the right that shows the bow in between the resawn boards, if you zoom in on the photo you can see where the cathedral edge grain is centered on the edge of the board where it is closest to the end of the board, but as you move up the board to where the bow is the worst the cathedral grain works its way to the right side of the board.
What this tells you is one of two things. First, the log may have had an off centered pith in one location, which would cause the edge grain to move relative to the face of the board. This will result in inconsistent stresses being present in the board. The other likely option is that the sawyer did not center the pith both way on the log when he/she made their opening cuts, which resulted in the board not having perfectly centered quartersawn grain on both ends.
Additionally, it is hard to see in the photo but it almost appears that there is a defect (knot) on the edge of the board adjacent to where you have your pencil marks on the edge in the center, or something that caused the grain to change directions. It also appears that there may be some edge checks due to the presence of pithwood along the edge of the board.
I would hazard a guess that if you study the medullary ray fleck on the board, it is much more pronounced on the end closest to where you took the photo of the end grain, and that it is much less pronounced on the opposite end of the board due to the lack of pith center in both dimensions.