  We have been studying QCD with 2 flavours of colour-sextet quarks to
distinguish whether it is QCD-like or conformal. For comparison we are now
studying QCD with 3 flavours of colour-sextet quarks, which is believed to be
conformal in the chiral limit. Here we present the results of simulations of
lattice QCD with 3 colour-sextet quarks at finite temperatures on lattices of
temporal extent $N_t=4$ and 6, with masses small enough to yield access to the
chiral limit. As for the 2-flavour case, we find well-separated deconfinement
and chiral-symmetry restoration transitions, both of which move to appreciably
weaker couplings as $N_t$ is increased from 4 to 6. If this theory is
conformal, we would expect there to be a bulk chiral transition at a fixed
coupling. For this reason we conclude that for $N_t=4$ and 6, the chiral and
hence the deconfinement transitions are in the strong-coupling domain where the
theory is essentially quenched. The similarity between the behaviours of the 2
and 3 flavour theories suggested that the $N_t=4$ and 6 transitions for the
2-flavour theory also lie in the strong-coupling domain. The phase structure of
both theories is very similar.
