  In this work a simple problem on 2D optimal shape for body immersed in a
viscous flow is analyzed. The body has geometrical constraints and its profile
would be found in the class of cubics which satisfy those conditions. The
optimal profile depends on the leading coefficient of these cubics and its
relation with the Reynolds number of the system is found. The solution to the
problem uses a method based on a suitable transformation rule for the cartesian
reference.
