First, realize that it's not specifically the orientation or the absolute
radius of the rings that count in cupping, but the difference between the
smallest and the largest arc in the same piece. The science of shrinkage
says the earlywood shrinks more than latewood. Where there is
proportionally more latewood - near the heart, it shrinks hardly at all.

Look at a log left to dry on its own, and you'll see that it cracks radially
to relieve this induced stress. Split the log green, and notice that it
dries with no radial checks, but with a crowned center. Note also that the
crown you see most often - on softwood, is the result of a large change in
moisture content, beginning at the fiber saturation point, a condition the
boards should never experience again.

The answer, to me, is to get rid of that center, something rarely a problem
when hardwood lumber is sawn for grade. Only when it is sawn
through-and-through as softwood commonly is, does it become a real problem.
That's where and why I'd rip - the center of the tight arc to relieve
stress, and then I'd probably find the best match not by reassembly of cut
faces, but by mating sapwood sides.

As usual, Hoadley has a good section on this, as does the late Tage Frid.

"Lenny" wrote in message
...
On Sun, 1 Aug 2004 13:07:05 -0500, "RonB" wrote:


A couple of years ago I was building a 8/4 Oak table top for a coffee
table
and was unsure of the best rip widths for the glue-up assembly with this
heavy material. I posted to forums of a couple of woodworking magazines
and
was surprised at a response. A magazine editor said that with heavy
stock,
with fairly large radius growth rings, it was ok to rip at 4" to 5" and
glue
them back together in their original position. He claimed the glue
joints
did an adequate job of relieving the stress and I could retain the
original
appearance of the slab.

The post came slowly -- after I had ripped and glued in the conventional
(alternating) manner. The top looked fine but I still
wonder.............????

ANY INPUT?


There are certain factors to take into account :
Will the slab be held in place (such as a tabletop or a countertop)
which would help keep it from "cupping" , as opposed to.... say a lid
for a blanket chest or such. Is the wood quartersawn, in which case
the tendency to move or cup is greatly reduced. In our shop we
generally go for "the best face", matching color and grain . If it IS
for a tabletop, be sure to allow for movement by enlarging the holes
for the screws that hold it down. (or by other methods)