"Jay Honeck" wrote

We usually start to rotate (and that's not really what we're doing -- more
like applying mild back pressure) around 70 mph -- but that's not a hard
and
fast figure. It all depends on "feel", in my experience -- which, in
turn,
is based on weight, wind, temperature, etc.

Ground fog forms because the ground is cooling the air near it (due to
radiational cooling) faster than the air further from it. You already knew
that, though.

MY guess what happen, is that after you started to rotate, the warmer air
above started getting pushed down into the cooler air, warmed it up, (or you
got into the warmer air) gave you less lift than the cool ground air, then
you started not lifting so good. Just a guess, though.
--
Jim in NC