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Thanks you guys. I think our two industries may have different terms for the grain so let me try to get on the same page with ya. In aircraft lumber terms, we define:
1. "run-out" as angle of the face-grain with relation to the edges of the board along its length. I cut areas of run-out off a long board; ie the grain runs perfectly parellel to the edges along the entire length of the finished spar.
2. "slope of grain" as the general direction of the longitudinal fibers of the wood. I'm gathering that this term is the "runout" to luthiers. Cause: the twist of the tree as it grew. We are limited to 1:15 on the slope. I grade out any wood in excess of this 1:15 and prefer no slope down the entire length of the board.
3. "vertical grain" as the angle of the annular rings from the face of the board when viewed from the end grain. We consider anything from 45 degrees to 90 degrees to the face to be vertical. My cants are quarter sawn so I get a lot of 90 to 80 degree which is my personal favorite. On the cants that are 60, 50, 45, I run the cant through the mill on an angle to get back to at least 70. I don't know what your limits on vertical are.
do you mill from a split face to minimize runout?
This would be what is normally looked for in soundboard wood.
1. We also look for VG. Close as possible.
2. Generally I think a limit closer to 1:28 or less would be our target(if you are maintaining 1:15 along 18', I am sure it is likely better than 1:28 along most of the board) .
3. Within 5 degrees of 90 is what we look for, and within 2 degrees or dead on 90 would suit highest grades.
Yes, we mill from split wood(wedges split from 24-30" long rounds). It is much easier when you are looking to meet these requirements in a 24" long piece(not 18' boards). Color variation is another thing that is generally important. It would also be important to consider flaws that may be disregarded in aircraft lumber, as even small(solid) pin knots or pitch pockets are issues on soundboards. Grain spacing (even spacing) is desired. Hope that helps a bit.
Rich