  Monte Carlo simulations of the frustrated 2D XY model were carried out at
small commensurate values of the frustration $f$. For $f=1/30$ a single
transition was observed at which phase coherence (finite helicity modulus) and
vortex lattice orientational order vanish together. For $f=1/56$ a new phase in
which phase coherence is absent but orientational order persists was observed.
Where comparison is possible, the results are in detailed agreement with the
behavior of the lattice Coulomb gas model of vortices. It is argued that the
helicity modulus of the frustrated 2D XY model vanishes for any finite
temperature in the limit of weak frustration $f$.
