On Mon, 13 Jun 2016 22:39:24 -0400, woodchucker
wrote:

On 6/13/2016 8:35 PM, wrote:
is poplar a strong enough wood to support a large granite countertop? there would be 3 corbels ...each 8x145/32x3

That all depends on the design, and which way the grain is oriented. But
yes, vertically it will support it, horizontally, it will depend on the
thickness, frequency of support.

The difference being compression vs. shear strength. Wood is very
good in compression but quite variable in shear. Grain direction
matters a lot.

Engineering is everything in supporting mass.