  To confront the predictions of the most recent line-driven disk wind models
with observational evidence, we have obtained HST STIS (1180--1700A) echelle
spectra of the nova-like variables IX Vel and V3885 Sgr at three epochs. The
targets were observed in timetag mode for ~2000sec on each occasion, allowing
us to study the spectral time evolution on timescales down to ~10sec. The mean
UV spectra are characterised by the wind signature of broad blueshifted
absorption in Lya, NV1240, SiIV1398, CIV1549 and HeII1640. There is very little
redshifted emission other than in CIV. Narrow blueshifted absorption dips,
superposed on the broad absorption at around -900km/s, accompany periods of
well-developed wind activity. The continuum level and mean line profiles vary
markedly from observation to observation -- with the wind signatures almost
disappearing in one epoch of observation of IX Vel. The strong positive
correlation between UV brightness and wind activity predicted by line-driven
disk wind models is disobeyed by both binaries. The wind signatures in IX Vel's
UV spectrum are revealed to be remarkably steady on timescales ranging from ~10
to ~1000sec. More variability is seen in V3885 Sgr, the binary with the lower
opacity outflow. But there is only one epoch in which the line profile changes
significantly in ~100sec or less. Narrow absorption dips, when present, show
only smooth, small changes in velocity.
