Options

That makes a lot of sense to me. Avenal is really just
flat fields everywhere. And I can see how deconflicting with other
traffic is important (although Minden seems pretty lightly
used for GA).

I guess remote cylinders or remote control points are
either not available to CDs or just not popular. 1000ft
seems like a lot of altitude to sort things out, so maybe this isn't
that critical, and at a huge airport like Avenal or Minden
(with lots of runways) it seems like there are still lots of options
even at low energy.

Thanks for the response!

In article ,
Marc Ramsey wrote:
Mark James Boyd wrote:
How many CDs choose cyclinders? Of theses cyclinders, how many
are centered at the airport, and how many are remote (centered away
from) the airport?

If remote, are they 2-5km out at 1000ft minimum? What is the
cylinder radius? Is it 1/2km like the previous poster's
"control point"?

A finish cylinder doesn't have to be remote, as you pull up at the edge,
not the center. If you need to keep high speed finishers away from the
airport, you increase the radius (up to a maximum of 4 miles) and raise
the floor.

I've flown in five sanctioned contests that used GPS finishes (I also
did the finish gate dance in pre-GPS days). Of those, four used finish
cylinders and one used a finish gate.

Out of the four cylinders, all were centered on the airport (at an
identifiable point, like a wind triangle), two (Montague and Tonopah)
used the standard 1 mile radius and 500 foot floor, the other two were
at Minden where a 2 mile radius and 1000 foot floor is used, to minimize
conflicts with non-contest traffic.

The finish gate was used at Avenal, the standard 1 km wide, adjacent and
running perpendicular to the center of the west side of the runway.

Marc


--

------------+
Mark J. Boyd

I was just doing some polar math.

Let's say I'm on a Mc = 0 final glide in my ASW-27B.
I cross the finish cylinder boundary at 500' and 60
knots (best L/D dry). I'm now 1 sm from the airport
center. I fly at best L/D and reach the airfield with
about 380' of altitude. This is about the same altitude
I'd have if I'd crossed a finish gate at 100 knots
and 50 feet then pulled up.

If on the other hand I cross the cylinder at 150 knots
and 500' I will reach the airfield at 50', still at
150 knots. After my pullup I will have something more
than 900'. I know which scenario I prefer.

It's all about total energy. If you think total energy
is more about 500' of altitude than an extra 90 knots
of airspeed I suggest you do the math.

My suggestion is to keep these issues the domain of
the CD and contest organizers. They understand best
the local airport and traffic patterns and the nature
of the local conditions. Low total energy finishes
should be (and are) subject to penalty at the CD's
discretion. It's easy enough to judge off of GPS logs
now.

9B

At 00:00 12 March 2005, Eric Greenwell wrote:
wrote:
First, when do you pull in a cylinder finish?

How about when it's clear? There's no hurry, unlike
being 50 feet off
the ground.

When the
gps goes beep? How do I know mine will go beep in
sequence with yours?
What if I delay my pull?

I'm guessing you'd continue in the direction you are
headed. Since you
are 500' in the air, this shouldn't cause any heartburn.

What risk am I taking? What are the speed
differentials among the gliders in the gaggle? With
a finish line, high
and low energy aircraft separate naturally.

You'll have to explain how this happens. I've seen
high and low speed
gliders close together at finish lines, and if the
high speed glider is
lower than the others, watch out! He's eager to climb
up to pattern
height and isn't going to coast along for another 1000'
or so.

Will the pilot above and
behind me pushing to redline notice I'm in front flying
at best L/D in
an attempt to avoid missing the bottom of the cyliner?

He's safe - he'll separate from you when he pulls up,
and you aren't
going to pull up. That's a good situation. It seems
unlikely he won't
see you ahead of him as he approaches. I've seen the
same situation
finish gates, anyway.

And where is the
cylinder? Why, it's right there on my instrument panel!
Next to the
altimeter, my other sore distraction.

I think if you can keep track of the other gliders
zooming into a finish
line from various altitudes and angles, you'd be able
to manage a finish
cylinder. At least, as you approach the cylinder, the
gliders that will
enter the cylinder near you are all going the same
direction you are,
which is often not true at a finish line.

When was the last time we wanted to ban gaggles for
safety reasons?

I think most of us have wanted to elimanate *large*
gaggles, but no one
has figured out a good way to do it.

My theory is that ignorance shows more profoundly
low and fast than
high and slow.

If by ignorance, you mean 'poor judgement', I agree
with you, and I
think this is the theory behind the finish cylinders,
isn't it?



--
Change 'netto' to 'net' to email me directly

Eric Greenwell
Washington State
USA

Andy Blackburn wrote:
Let's say I'm on a Mc = 0 final glide in my ASW-27B.
I cross the finish cylinder boundary at 500' and 60
knots (best L/D dry). I'm now 1 sm from the airport
center. I fly at best L/D and reach the airfield with
about 380' of altitude. This is about the same altitude
I'd have if I'd crossed a finish gate at 100 knots
and 50 feet then pulled up.

If on the other hand I cross the cylinder at 150 knots
and 500' I will reach the airfield at 50', still at
150 knots. After my pullup I will have something more
than 900'. I know which scenario I prefer.

What, exactly, is your point? This makes no sense...

Marc

Don't argue with 9B re the logic of the math issue....trust me....he's a
very bright guy and never leaves his calculator! He is offering the
mathematical explanation of why cylinder finishes may not be any safer. Of
course it supports my point so I'm thinkin' he's a rad dude!

It's been a good discussion guys.....hope that all of you have a super
weekend of soaring whatever height you choose to finish!

Casey Lenox
KC
Phoenix

Kilo Charlie wrote:
Don't argue with 9B re the logic of the math issue....trust me....he's a
very bright guy and never leaves his calculator! He is offering the
mathematical explanation of why cylinder finishes may not be any safer. Of
course it supports my point so I'm thinkin' he's a rad dude!

Hmm, I pegged him for a lawyer or politician, the numbers may have some
basis in reality (assuming you fly in a vacuum), but the logic is, uh,
"interesting".

It's been a good discussion guys.....hope that all of you have a super
weekend of soaring whatever height you choose to finish!

Agreed...

Marc

Kilo Charlie wrote:
Don't argue with 9B re the logic of the math issue....trust me....he's a
very bright guy and never leaves his calculator! He is offering the
mathematical explanation of why cylinder finishes may not be any safer. Of
course it supports my point so I'm thinkin' he's a rad dude!

Hmm, I pegged him for a lawyer or politician, the numbers may have some
basis in reality (assuming you fly in a vacuum), but the logic is, uh,
"interesting".

It's been a good discussion guys.....hope that all of you have a super
weekend of soaring whatever height you choose to finish!

Agreed...

Marc

well... as most finishes would be at worm burner speeds even for the
cylinder, not bet L/D speed... at least you would start the "zoom" from
100knts and 500ft higher? even if 1/2 mile from the runway instead of 10 ft
over it.

flying the cylinder at best L/d would be conservative if you were going to
barely make it home.. I would think

BT

"Kilo Charlie" wrote in message
news:m6uYd.43315$FM3.18415@fed1read02...
Don't argue with 9B re the logic of the math issue....trust me....he's a
very bright guy and never leaves his calculator! He is offering the
mathematical explanation of why cylinder finishes may not be any safer.
Of course it supports my point so I'm thinkin' he's a rad dude!

It's been a good discussion guys.....hope that all of you have a super
weekend of soaring whatever height you choose to finish!

Casey Lenox
KC
Phoenix

At 05:00 12 March 2005, Marc Ramsey wrote:
Kilo Charlie wrote:
Don't argue with 9B re the logic of the math issue....trust
me....he's a
very bright guy and never leaves his calculator!
He is offering the
mathematical explanation of why cylinder finishes
may not be any safer. Of
course it supports my point so I'm thinkin' he's a
rad dude!

Hmm, I pegged him for a lawyer or politician, the numbers
may have some
basis in reality (assuming you fly in a vacuum), but
the logic is, uh,
'interesting'.

The point was pretty simple - I added the analysis
because without it I'm just a guy with an opinion (no
shortage of those here). So here's the point in simple
language: A low energy finish at 500' and 1 sm is
not significantly 'safer' than a low energy finish
at 50' over the airport. Either way you will be low
and slow in the pattern.

The numbers assume viscous, incompressible flow - gliders
can't fly in a vacuum. Bet you knew that. ;-)

9B

Andy Blackburn wrote:
The point was pretty simple - I added the analysis
because without it I'm just a guy with an opinion (no
shortage of those here). So here's the point in simple
language: A low energy finish at 500' and 1 sm is
not significantly 'safer' than a low energy finish
at 50' over the airport. Either way you will be low
and slow in the pattern.

Your analysis is flawed, because you miss one little point. Let's assume
we're comparing a finish gate adjacent to the center of the runway, and
a 1 mile radius cylinder centered on the runway. If you hold all other
factors constant, in particular the altitude at which you leave the last
thermal and the speed at which fly the final glide, if you pull up to
best glide at 1 mile you will always end up over the runway as high (if
your are already flying at best glide) or higher than if you pull up at
the gate. In other words, if you are low energy at 1 mile, you will
have as low or lower energy if you don't pull up until you reach the
gate, because you can't recover the drag you lose by flying faster than
best glide for the last mile.

Now, if you assume that you leave the last thermal when the computer
says final glide is made (or you leave with a constant offset from the
computer indication), then the 500 foot 1 mile case will require that
you climb higher, as it obviously takes less energy to get to the gate
at 50 feet (unless you are flying final glide at a speed where your L/D
is less than 10:1, which is ridiculous in modern gliders). You will
start a marginal final glide with more energy in the cylinder case, than
you will in the gate case. If your final climb is capped by the height
of the thermal, then you may have to opt for a rolling finish using a
cylinder, and still be able to make a gate finish, but you will be
making that final glide at essentially best glide, and have no energy
left to pull up after you go through the gate.

My point is also pretty simple. In no realistic case will you ever end
up with more energy for landing by delaying your pull-up until you reach
the airport. You will always end up with more energy over the airport
by making a final glide to 1 mile and 500 feet. This also means that
you have more margin for screw ups in the cylinder case.

The numbers assume viscous, incompressible flow - gliders
can't fly in a vacuum. Bet you knew that. ;-)

I do, but I'm not so sure you do. The exchange of energy implied by
your pullup from 50 feet at 150 knots that results in "something more
than 900'", either includes no losses for drag or you're doing a tail
slide at the top. If you have a trace where you actually manage to pull
up to 900 feet above your finish altitude, I'd love to see it...

Marc

With a center of airport 50' finish you still need to do a pattern including
up to three 90 degree turns after finishing (ignoring rolling finishes).
With a 500'/1 mile cylinder you can do a straight in or several possible
patterns, and you don't need to go to the center of the airport first, so
the distance is really 3/4 mile or much less to a downwind or base leg.
-Bob Korves

"Marc Ramsey" wrote in message
...
Andy Blackburn wrote:
The point was pretty simple - I added the analysis
because without it I'm just a guy with an opinion (no
shortage of those here). So here's the point in simple
language: A low energy finish at 500' and 1 sm is
not significantly 'safer' than a low energy finish
at 50' over the airport. Either way you will be low
and slow in the pattern.

Your analysis is flawed, because you miss one little point. Let's assume
we're comparing a finish gate adjacent to the center of the runway, and
a 1 mile radius cylinder centered on the runway. If you hold all other
factors constant, in particular the altitude at which you leave the last
thermal and the speed at which fly the final glide, if you pull up to
best glide at 1 mile you will always end up over the runway as high (if
your are already flying at best glide) or higher than if you pull up at
the gate. In other words, if you are low energy at 1 mile, you will
have as low or lower energy if you don't pull up until you reach the
gate, because you can't recover the drag you lose by flying faster than
best glide for the last mile.

Now, if you assume that you leave the last thermal when the computer
says final glide is made (or you leave with a constant offset from the
computer indication), then the 500 foot 1 mile case will require that
you climb higher, as it obviously takes less energy to get to the gate
at 50 feet (unless you are flying final glide at a speed where your L/D
is less than 10:1, which is ridiculous in modern gliders). You will
start a marginal final glide with more energy in the cylinder case, than
you will in the gate case. If your final climb is capped by the height
of the thermal, then you may have to opt for a rolling finish using a
cylinder, and still be able to make a gate finish, but you will be
making that final glide at essentially best glide, and have no energy
left to pull up after you go through the gate.

My point is also pretty simple. In no realistic case will you ever end
up with more energy for landing by delaying your pull-up until you reach
the airport. You will always end up with more energy over the airport
by making a final glide to 1 mile and 500 feet. This also means that
you have more margin for screw ups in the cylinder case.

The numbers assume viscous, incompressible flow - gliders
can't fly in a vacuum. Bet you knew that. ;-)

I do, but I'm not so sure you do. The exchange of energy implied by
your pullup from 50 feet at 150 knots that results in "something more
than 900'", either includes no losses for drag or you're doing a tail
slide at the top. If you have a trace where you actually manage to pull
up to 900 feet above your finish altitude, I'd love to see it...

Marc