Jim Conlin wrote:
Depends on how rocky the river is, how much weight you can tolerate, and your
definition of inexpensive.
If you plan to bump rocks a lot, the drift boat solution of cladding the bottom
with a tough plastic such as HDPE or UHMW might be warranted. Not light and not
real cheap.
Next less extreme would be glass in epoxy. A little graphite in the epoxy will
reduce friction on rocks and toughen the epoxy a bit.

I've used a graphite/epoxy coating on a centerboard, it's a tough &
slick finish. Hard to beat IMHO. It ain't cheap though, and it takes
more than "a little."

Fresh Breezes- Doug King