Nathan Young wrote:
I have a Cherokee 180, with the short hershey bar wing. While I love
the plane, I always wish it could go a bit faster, or use a bit less
fuel to get to my destination.

As a former PA28-180 owner, I can certainly agree with that.

I have followed the composite homebuilding movement for many years,
and am amazed at the sleekness of a composite wing. The wings on most
composites tend to be the complete opposite of a Hersey bar wing:
high aspect ratio, low thickness, no rivets, no screws for fuel
tanks,smooth curves faired into airframe, and streamlined landing gear
structure.

I'm no aerodynamicist, but I have a usenet-opinion. I think at Cherokee
airspeeds the effect of the screw and rivet heads is probably unmeasurable.

I'm not sure whether you're using 'composite' to mean the material from
which the wing is constructed, or the blending of different airfoil shapes.

I don't think the construction material has any effect on the
aerodynamics, but 'composite' materials may make it more economic to
manufacture complex shapes, and may reduce the weight of the resulting
structure.

If you are referring to blended airfoil shapes, look at the difference
between the fat-wing Pipers and the Archer II, Arrow II, etc.

So my question: How much drag does a wing on a Hersey Bar Cherokee
generate, and and hypothetically speaking, how much faster could the
plane go if it was retooled with a sleek, composite wing?

I'm not volunteering to do the research, but I think with a little (or a
lot) of googling you can find the NACO airfoil on which the
constant-chord fat-wing Piper wing is based, and the NACO report has a
lot of detail about the characteristics of that airfoil. I've looked it
up before, but I've lost the reference.

Not news to you I'm sure, but there is more to wing airfoil choice than
minimizing drag.