  We apply an {\it ab-initio} approach to the nuclear structure of odd-mass
nuclei straddling $^{48}Ca$. Starting with the NN interaction, that fits
two-body scattering and bound state data we evaluate the nuclear properties of
$A = 47$ and $A = 49$ nuclei in a no-core approach. Due to model space
limitations and the absence of 3-body interactions, we incorporate
phenomenological terms determined by fits to $A = 48$ nuclei in a previous
effort. Our modified Hamiltonian produces reasonable spectra for these odd mass
nuclei. In addition to the differences in single-particle basis states, the
absence of a single-particle Hamiltonian in our no-core approach obscures
direct comparisons with valence effective NN interactions. Nevertheless, we
compare the fp-shell matrix elements of our initial and modified Hamiltonians
in the harmonic oscillator basis with a recent model fp-shell interaction, the
GXPF1 interaction of Honma, Otsuka, Brown and Mizusaki. Notable differences
emerge from these comparisons. In particular, our diagonal two-body $T = 0$
matrix elements are, on average, about 800-900keV more attractive. Furthermore,
while our initial and modified NN Hamiltonian fp-shell matrix elements are
strongly correlated, there is much less correlation with the GXPF1 matrix
elements.
