Re WHY COAT ENDS WHEN DRYING LUMBER?

I'm no expert but the reason is pretty simple- you are trying to slow down
the differential drying of the outer wood from the inner.  Strain that
develops quickly results in the lumber cracking to relieve it.
  Slowing down the process allows the strains to work down slowly as the
drying evens out so that the layers hold together.   Most of the faults
occur around the very center of the tree (ie the pith) which is dryer.
Most of the strain is located around there.  That's why you try to cut that
part out of your lumber before drying it fully.  The wettest wood is
adjacent to the bark.  Most of the shrinkage occurs tangential to the
growth rings, then radially from the center with the outer 》》inner for both
kinds (which is why you see cupping of boards that are flatsawn).  There is
almost no change in length. Think of tree as a large bundle of straws, with
the outer ring of straws being larger than the inner rings, because the
outer ones contain more water.  They will eventually become almost the same
size as the moisture is released.
Sometimes there will be hidden faults (shakes) that you may not easily see
in the dry wood- often these are due to heavy winds while the tree is still
up (aka wind shakes), but more commonly it's from not taking the tree down
properly. These typically occur along the length of the growth rings.
Claudio in Waterloo