  We report the results of new SPH calculations of parabolic collisions between
main-sequence (MS) stars. The stars are assumed to be close to the MS turn-off
point in a globular cluster and are therefore modeled as $n=3$, $\Gamma=5/3$
polytropes. We find that the high degree of central mass concentration in these
stars has a profound effect on the hydrodynamics. In particular, very little
hydrodynamic mixing occurs between the dense, helium-rich inner cores and the
outer envelopes. As a result, and in contrast to what has been assumed in
previous studies, blue stragglers formed by direct stellar collisions are not
necessarily expected to have anomalously high helium abundances in their
envelopes or to have their cores replenished with fresh hydrogen fuel.
