Dehydration

At 01:30 29 March 2005, wrote:
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.

I did an analysis of this and it would appear that
the minumum time solution is to dial in a finish altitude
equal to 500' minus the altitude you can gain in a
pullup from your McCready speed to minimum sink speed.
Just before the cylinder edge you pull up and hit the
bottom outside edge of the cylinder. Depending on your
McCready setting you will approach the edge of the
cylinder at somewhere between 0 feet (Mc = 6 or higher,
full ballast) and 350' (Mc = 2, dry). It's easy to
calculate that you save about 45 seconds over flying
the McCready speed to the cylinder at 500'.

Why is this? Because there is excess kinetic energy
that can be turned into altitude at all cruise speeds
(the higher the speed, the more excess energy - and
altitude). To optimize, you should not carry excess
energy through the cylinder but instead come in below
the cylinder floor and use the energy to make the minimum
altitude, in this case 500'.

Most of us carry some extra margin just in case of
unexpected sink. In this case you can wait until you're,
say, two miles from the edge of the cylinder, then
dive off even more excess energy in the last two miles.
Because you are flying off more excess energy in a
short distance, you pretty quickly get up to speeds
where you can be right on the deck and pull up to well
over 500'. In this case you are flying less efficiently,
so the time savings go down a bit, to 20-30 seconds
versus flying McCready speed to 500'.

I would add that I am not advocating that anyone do
this, since I don't want to be held responsible for
the consequences of this finishing technique. It's
only worth a handful of points per day, but then again
so is finishing at 50' versus 200-300' in a gate.

9B

Morning Andy,
On the last day of the 18 meter nats at Montague, a few years back, the
fire base was activated and the County required us to arrive at or
above 1000 feet. Several pilots came to me and said, "If you don't
raise the finish cylinder to 1000 feet, some guys will drive hard and
then call a rolling finish, we need a big penalty for that". So, I
raised the 1 mile cylinder to 1000 feet and announced a 10 minute
penalty for making a rolling finish. Two top pilots did exactly what
wou described and BOTH missed the cylinder! They got their rolling
finish time + 10 minutes. There was ****ing & moaning & nashing of
teeth the like of which the world has seldom seen, complete with
threats of taking their protest to a higher power.

I don't recommend the procedure you described for several reasons, but
the big one I see is; It brings back the pull-up. I would be in favor
of a rule prohibiting hard pull-ups in the cylinder. Easy to enforce,
we have your GPS trace.
JJ

I did an analysis of this and it would appear that
the minumum time solution is to dial in a finish altitude
equal to 500' minus the altitude you can gain in a
pullup from your McCready speed to minimum sink speed.
Just before the cylinder edge you pull up and hit the
bottom outside edge of the cylinder. Depending on your
McCready setting you will approach the edge of the
cylinder at somewhere between 0 feet (Mc = 6 or higher,
full ballast) and 350' (Mc = 2, dry). It's easy to
calculate that you save about 45 seconds over flying
the McCready speed to the cylinder at 500'.

I don't recommend the procedure you described for several reasons,
but
the big one I see is; It brings back the pull-up. I would be in favor
of a rule prohibiting hard pull-ups in the cylinder. Easy to enforce,
we have your GPS trace.
JJ

But the rules DO recommend the procedure. It's the fastest way to
finish !

For any rule prohibiting hard pull-ups, how will the pilot know in
the cockpit, how hard can he pull up without violating the rule ?
Will g-meters be required equipment ?

I personnally have no fears of hard pullups, as long as I don't have to
do
them below 1000 ft AGL.

Todd Smith
3S

Hi Todd,
The rule could say something like, no sudden increase in altitude at or
near the finish cylinder, not to exceed, say 300 feet. I'm sure our
clever scoring programmer could measure time vs. altitude in the
pull-up and flag the trace for penalty consideration.

But the rules DO recommend the procedure. It's the fastest way to
finish !

For any rule prohibiting hard pull-ups, how will the pilot know in
the cockpit, how hard can he pull up without violating the rule ?
Will g-meters be required equipment ?

I personnally have no fears of hard pullups, as long as I don't have
to
do
them below 1000 ft AGL.

Yes, but this is where the near mid-air occurred at this years Seniors.
Several posters have pointed out the same potential exists in the
cylinder as in the line, hence my recommendation to basically prohibit
the pull-up in or near rhe cylinder. It's the guy in your blind spot
that gets you (or you get him)
JJ

Todd Smith
3S

Here's the solution to the problem that someone might be tempted to
dive for the base of the finish cylinder and do a radical pull-up, as
well as the problem that someone might try to thermal at 300' to get up
to 500' and save himself the rolling-finish penalty:

There is a donut of airspace, from 1 mile radius to (say) 4 miles
radius, with top at 500 feet (or finish cylinder base, if higher). This
is forbidden airspace, marked in the sua file as such. One fix in that
airspace, and you've landed out. (Or, if you feel that's too much, it
gets you a 100 point penalty, plus any rolling finish penalty or time
addition.) Essentially, we create an airport located in a 1 mile radius
valley, surrounded by a plateu at 500 feet.

Now the optimum thing to do for a pilot who cares even zero about his
own safety is to fly about 90 kts (regular glide speed) to about the 2
mile radius and 501 feet, then let speed bleed off to the average speed
for the flight at the 1 mile mark. Of course, sensible people will
just fly 90 kts to the 550' 1 mile point, with trivial loss of points.

(It's not efficient to end up as slow as possible at the 1 mile mark.
To see why, imagine you could fly at 0 airspeed. Taking 10 minutes to
go the last 100 feet would not make sense. If you flew 60 mph average
for the flight, flying level at 59 mph slows you down, while flying
level at 61 mph increases your average speed. Thus, you want to cross
the line at the average speed for the flight, 60 mph in this case. 5-10
kts extra cost hundredths of a point.)

There is no incentive for low-altitude thermaling just outside the
cylinder. Once you're below 500 feet (or 1000, or whatever the top of
the donut) you landed out so you might as well glide home. (If it's 100
points plus the rolling finish penalty, you just got the rolling finish
penalty, so again you might as well stop screwing around and go land.)
If you're 5 miles out and you can't make it over the donut (about 1200
feet is the decision height here), you have every incentive to stop;
either thermal at a decent altitude or find a decent landing place.
It's just like not being able to cross the final ridge into the
airport.

There is no need for a rules change to do this. CDs may now designate
any airspace they want to as off limits. Just put the donut in the sua
file. Any CD or contest manager who wants to ensure really safe
finishes can put this into place now.

The donut can also be used with a conventional finish line. This will
ensure that pilots arrive at the airport with plenty of energy, or
already committed to rolling.

John Cochrane
BB

Or how about this for a solution. The start cylinder has a top, right?
It actually extends well beyond the boundary of the cylinder. If you
go above this top, you must come back below it and remain below it for
two minutes before you can get a start without incurring a penalty. We
all know the rule.

How about a similar, but inverted plane and system at the base of the
finish cylinder? One data point below the base of the finish cylinder,
and you cannot get a finish until you have been above it for two
minutes. Or, maybe make it five. Might as well go take your rolling
finish if you dip below it on final glide. It is much easier to apply
the same rule two different places than to try and come up with
something else, IMHO. Will certainly stop ballistic trajectories, but
not the level decel.

Don't get me wrong, John. I like donuts, but in the morning before the
Pilot's Meetings!

Steve Leonard
ZS