nvh-srjones,
Good question. I believe you are referring to the orientation of the annual rings, not the orientation of the grain.
The grain of wood is the direction the wood fibers are running. This direction is more or less lengthwise up the tree or down the timber. Slope of grain is a way to measure the deviation of the grain from the timber or board's long axis.
Grain is often confused with figure which is the pattern that the growth rings make on the face of a timber or board as they surface and re-submerge.
Now to the heart of your question. Does the orientation of the growth rings relative to some load affect the strength properties of the timber?
In a species that is very prone to shake (the seperation of the wood fibers along an annual ring), I think that this might be important to consider, as a bad case of the shakes might pop a lot of joists.
I don't know about Doug fir off the top of my head as we don't use it. Maybe someone familiar with the characteristics of Doug fir could give their 2 cents.
Gabel
