On Thu, 25 Oct 2012 18:35:08 -0500, Swingman wrote:

On 10/25/2012 5:30 PM, Dick Snyder wrote:
Thanks. The widest board will be 7" x 74 1/2". I was most worred about
length but I do have room on width as long at I place the two end pieces,
which will be at a 90 degree angle to the long boards, with screws in
oversized holes so the long pieces can move.

Every woodworker needs to keep a copy of the following in the shop:

http://www.fs.fed.us/ccrc/topics/urb...0of%20wood.pdf

As you will read, not only is the species of importance when selecting
woods based on their reaction to moisture/seasonal changes, but also the
cut off the log (quarter sawn, flat sawn, etc).

As a general rule, and for most species, if you want to reduce expansion
and contraction across your board's face, try to select quarter or rift
sawn stock for those areas/components which may be subject to
dimensional instability due to moisture/seasonal changes.

(NOTE: these tables come in extra handy when you are faced with
veneering/laminating different species of wood)

Woodworkers may find this tool handy as well:
http://woodshopwidget.com/

There are iOS and Android versions for $4 as well as a free web
version.