Right. That clarifies what you meant. By 'turnpoint',
the way I used it in the question, I meant the point
that you actually have to round physically, whether
it be the near edge of a cylinder or the centre or
whatever.

Good - you don't generally think about the turnpoint
as a fixed point in a racing task where you get credit
for distance within the cylinder - at least I don't.
You would think about it as a fixed point for record
flying.


Yes, all this is clear. This could perhaps be summed
up
by saying that to fly beyond the TP would only be worth
it if you find significantly stronger lift there than
you will along the task after the turn.

Yup. The trick is having a sense for how much stronger
the expected lift needs to be given the distance and
sink rate and whether you're getting credit for the
extra distance flown. I went 0.5 mi and 1.5 mi past
the far side of turn cylinders in contest tasks this
summer (with no sink involved). In the first case I
expect I broke even overall, in the second case it
was a losing proposition.

9B