Comparison of glider classes at Uvalde...

What is the optimum G for the pullup?

Or is it more a matter of pulling to ClMax - so an AOA gauge is really needed?

Let's say a generic 15 meter flapped ship, at 8psf and 145 knots - my gut feel is about a 3 g pull while simultaneously setting some flap (0 or +5) is close to optimum. Pull to about 40 degrees nose up, ease off to 1 g, then roll off to let the nose drop to level (no bunt).

How do the rest of you do it?

Kirk
66

Not like that.
If crosscountry speed is your aim reduce the pushing and pulling.
Tom


At 00:57 26 August 2012, kirk.stant wrote:
What is the optimum G for the pullup?

Or is it more a matter of pulling to ClMax - so an AOA gauge is really
need=
ed?

Let's say a generic 15 meter flapped ship, at 8psf and 145 knots - my gut
f=
eel is about a 3 g pull while simultaneously setting some flap (0 or +5)
is=
close to optimum. Pull to about 40 degrees nose up, ease off to 1 g,
then=
roll off to let the nose drop to level (no bunt).

How do the rest of you do it?

Kirk
66

Not crosscountry gain - max height gain in a pullup; for example after a low pass.

Kirk
66

On Sunday, August 26, 2012 12:40:46 AM UTC-5, kirk.stant wrote:
Not crosscountry gain - max height gain in a pullup; for example after a low pass.



Kirk

66

I wonder; is the heigth loss the same in a push over? Would the energy exchange be the same as in a zoom?

DW

Not remembering the entire thread, and just responding to this question, a
push over followed by a pull up will always result in an altitude loss (in
still air). We're talking conservation of energy here. Engineers and
scientists will understand. This is not a perfect system and there will be
friction losses (drag). Every time you deflect your control surfaces, you
incur a drag loss. I do this all the time...


"KA6CR Driver" wrote in message
...
On Sunday, August 26, 2012 12:40:46 AM UTC-5, kirk.stant wrote:
Not crosscountry gain - max height gain in a pullup; for example after a
low pass.



Kirk

66

I wonder; is the heigth loss the same in a push over? Would the energy
exchange be the same as in a zoom?

DW

On Sep 2, 10:07*am, "Dan Marotta" wrote:
Not remembering the entire thread, and just responding to this question, a
push over followed by a pull up will always result in an altitude loss (in
still air). *We're talking conservation of energy here. *Engineers and
scientists will understand. *This is not a perfect system and there will be
friction losses (drag). *Every time you deflect your control surfaces, you
incur a drag loss. *I do this all the time... *

"KA6CR Driver" wrote in message

...







On Sunday, August 26, 2012 12:40:46 AM UTC-5, kirk.stant wrote:
Not crosscountry gain - max height gain in a pullup; for example after a
low pass.

Kirk

66

I wonder; is the heigth loss the same in a push over? Would the energy
exchange be the same as in a zoom?

DW

Some basics in my view:

The first thing to get right is not the push or pull, you're doing
this to adjust airspeed. So the most basic issue is when do you want
to speed up and slow down to follow lift and sink. That is primarly a
question of whether the lift or sink will last. There isn't much point
in a huge pull up in east coast punchy isolated thermals, because by
the time you've got the glider slowed down, you're through the thermal
and in to the sink. If the lift is lined up in to the wind, under a
cloud, streeting, clumping, or otherwise giving signs that it will
still be there when you've slowed down, then a pull up and even a
sharp pull up works

The second issue is the dynamic soaring effect. Yes, a pull and push
in still air loses height. But pulling up in lifting air and pushing
over in sinking air gains energy. This is hard to do. Really, you want
to pull when the glider still has momentum from the previous air and
is now in new air. You want to pull when the net lift+drag vector is
pointing forward relative to the path of the glider. Then, increasing
lift+drag speeds up the glider. So a sharp pull when you run in to
sharply increasing lift can gain energy.

A lot of the art of squeezing good glides comes from doing this just
right.

Two good winter projects: Work out the dynamic program of how to
optimally extract energy from a sharp-edged gust, given you don't know
when it's going to come. And create the next generation of "dynamic
soaring" varios that indicates when adding gs adds energy. Its not
that hard to do -- is the lift+drag vector pointing forward relative
to the path of the glider?

John Cochrane

Related read:
http://home.planet.nl/~kpt9/Hoogtewinst.htm

Should be pretty readable with Google Translate (from Dutch to English).

The Dutch study is fun but unrealistic - adopted time 3s means 150m lift diameter for a cruising speed.
For wider lifts and cumulus ways conclusion would be probably reverse