  The potentials between static sources in various representaions in SU(3) are
calculated based on the fat-center-vortices model of Faber, Greensite and
Olejnik. At intermediate distances, most distributions of the flux within
vortices lead to potentials that are qualitatively in agreement with ``Casimir
scaling,'' which says that the string tension is proportional to the quadratic
operator of the representation. However, at the quantitative level, violations
of Casimir scaling are generally much larger than those seen in numerical
simulations, indicating that additional physical input to the
fat-center-vortices model is required. At large distances, screening occurs for
zero-triality representations; for the representations with non-zero triality
the string tension equals that of the fundamental representation. Some rather
``unphysical,'' flux distributions can lead to violations of Casimir scaling at
intermediate distances and violations of the expected ordering of
representations at large distances.
