Mixing construction materials

In the " I wonder if this would work " department, I have a question
about mixing different materials in main airframe structures. To make
a long story short, I was wondering if some weight could be saved by
making a wing with a carbon fiber spar ( high strength, light weight )
with aluminum ribs and skins. Would the carbon and aluminum be
compatible? Of course an acceptable method would have to be devised
to attach the ribs and skins to the spar, but I don't see this as a
big problem. Since the spars are some of the heaviest part of the
wing, I thought this would be a good way to save some weight, and in a
case I have in mind, an easy way to join the spar to the fuselage,
especially if the fuselage is composite. I would want to keep the
rest of the wing aluminum mainly to save dollars, but also because of
the proven history. Would the weight savings be worth the effort?

Neal