I am building a 6 foot long shelf that is going to be supported at the ends
(no option of support in the middle). The shelf needs to support about 50-
70 pounds of weight (stereo equipment), so the "sag" (or deflection) in the
center is going to be a problem. I plan on building the shelf as a hollow
box, and using steel angle iron on the inside as a stiffener.

Just out of curiosity -- what commonly available wood product is best for
resisting deflection under a continuous load (i.e. shelving)? The easily
available ones at my local lumber store a laminated pine, mdf, playwood
and particle board, I am assuming that the laminated pine would be best,
since all the grain is running longitudinally. Is my assumption correct?

--
Murray Peterson