Dehydration

On 3/27/05 7:34 PM, in article
,
" wrote:

Pull-up is not necessary at the finish cylinder, so why do it?

OK, I've lurked long enough. I'll probably be sorry, but....
Why not? Aren't we trying to puncture the edge of the cylinder very near its
bottom at maximum speed? Now, an instant later, we find ourselves 499' AGL
at redline less than a mile from the airport. Seems to me we sort of have to
pull up even a teensie bit to get slowed down and sorted out and into the
pattern.

Some math in prior posts points out that the length of the arc of the
cylinder we are trying to reach (on an AST at least) is even shorter than
the 1km long finish line. For me at least, all the cylinder does in this
case is move the bottom of the high speed pass up 450'. Maybe that's better
or safer, I'm not sure; it's certainly not obvious to me.

Additionally, the rules state that the 4 mile radio call for a finish is 4
miles from the finish point, the cylinder center. So with a 2mi radius
finish cylinder, radio calls come about a minute before the finish. With a
finish line, the 4 mile radio call gives 2 minutes of warning. I'd kinda
like as much warning as possible about who's nearby.

--
Bob
bobgreenblattATmsnDOTcom --fix this before responding

Bob Greenblatt wrote:
Aren't we trying to puncture the edge of the cylinder very near its
bottom at maximum speed?

Got to thinking about your question, Bob and actually we shouldn't try
to hit the edge of the cylinder at red-line. Why? Because our
sailplanes are very inafficient at red-line, in fact they start coming
down like a stone at anything over 90 knots. We should climb the last
thermal to 500 over home + a smidgen and then fly the indicated M/C to
the edge of the cylinder. You should get there between 60 and 90 knots,
depending on conditions on the glide. If you get there at red-line,
that means you climbed too high in the last thermal and it cost you
(time).

The finish line, on the other hand, requires a finish at red-line, so
that we can exchange our excess speed for pattern altitude. I'm even
tempted to say the cylinder is the most efficient way to fly the final
glide, but if I did, OC would just fly off in another snit, and I would
be forced to look up all those big words, again...............
:) JJ

Optimum is the same for either finish. Most of us just don't have the
guts to cut it that close with a line finish.

With a high cylinder finish, you can cut it close. You're risking points
if you end up a bit lower than you hoped. But your margin for momma and
the kids is built in to the optimum answer. Its then more a contest of
skill than nerve, at least for the final glide.

Since most pilots will try to fly efficiently, the range of speeds at
the cylinder is reduced, and lowered compared to the gate. Makes for a
nice orderly follow the leader to land, with a tad more time after the
race is over to sort it out.

That can degenerate when everyone finishes way too high and hot or just
squeaking in a rolling finish, but it does the same thing with a gate.

With a line everyone shoots for the sweet end of the line. There always
is one. With a cylinder, finishers will naturally be much more spread
out. Maneuvering will be less predictable, but also more uniformly
gentle. Given the blind spots in all our gliders, and the tendency to
fixate on the targets you see and know about, we really count on the big
sky theory more than we like to admit. A little more natural spacing
makes the sky bigger.

But the cylinder is an instrument approach since it is completely
invisible, which has to pull some of your attention into the cockpit.
Cutting the edge of the gate is, too, since its really defined by GPS
coordinates, not a ground feature. Not very comforting for either finish
in traffic.

If you think either one is really safe, you're nuts. Both can be
executed successfully, but the margins flying that close to so many
other gliders and the ground are just not that big. I think the cylinder
is a bit less risky, but a lot less fun.

A perfect final glide to the edge of the cylinder at 75 kts is so
anti-climactic after an epic adventure out on course. Nothing compares
to the good old assigned task and no minimum height gate.

But I can change... If I have to... I guess.

-Dave Leonard
ZL




wrote:
Bob Greenblatt wrote:
Aren't we trying to puncture the edge of the cylinder very near its

bottom at maximum speed?


Got to thinking about your question, Bob and actually we shouldn't try
to hit the edge of the cylinder at red-line. Why? Because our
sailplanes are very inafficient at red-line, in fact they start coming
down like a stone at anything over 90 knots. We should climb the last
thermal to 500 over home + a smidgen and then fly the indicated M/C to
the edge of the cylinder. You should get there between 60 and 90 knots,
depending on conditions on the glide. If you get there at red-line,
that means you climbed too high in the last thermal and it cost you
(time).

The finish line, on the other hand, requires a finish at red-line, so
that we can exchange our excess speed for pattern altitude. I'm even
tempted to say the cylinder is the most efficient way to fly the final
glide, but if I did, OC would just fly off in another snit, and I would
be forced to look up all those big words, again...............
:) JJ