ransley errs again, spectacularly :-)

JJ wrote:

I would like to construct a very simple footbridge over our creek. The
distance is around 12-14 feet from bank to bank. =A0I figured on using
two 16' pieces of lumber as the support (about 18-20 inches apart),
with 1x6 decking boards along the top. About 2.5' to 3' wide.

My question is what should I use for the support beams.

I was conteplating either using 4x6 lumber or 2x8 lumber...

a 4x4 will hold a truck, a 4x4 will hold a house...

A 4x4 with S = bd^2/6 = 7.15 in^4 and M = fs = 7146 in-lb will support
a W = 8M/L = 340 pound distributed load (including the decking boards)
over an L = 14x12" span.

Nick