physics question about pull ups

On Jun 5, 3:07*pm, Gary Osoba wrote:
On Jun 5, 2:41*pm, Nine Bravo Ground wrote:





On Jun 5, 2:30*pm, Gary Osoba wrote:

On Apr 25, 8:21*am, Andy wrote:

As an aside - the strong G-effect on induced drag is the main reason
why you should try to avoid hardpullupsinto thermals - you give away
a bunch of altitude.

9B

Yes, if you both accelerated and are now pulling up in a constant
velocity of transportation field. But by mentioning the thermal, this
is not likely. With discontinuous fluid fields, coupled pullups and
pushovers which are properly timed within a shifting frame of
reference have the potential to gain much more energy than is ever
lost to induced and friction drag- dry or fully loaded. The fully
loaded case has more potential in typical soaring environments because
more time is available to apply the technique and the events can be
further apart.

For most gliders, the optimized multiplier is so substantial that you
run out of positive g maneuvering envelope (based on JAR standards)
with a mere 2-3 knots of lift.

Best Regards,

Gary Osoba

If you mean dynamic soaring then the airmass velocity gradient needs
to be horizontal, not vertical as is the case with thermals - plus the
magnitude of the gradient in a thermal is way too low to be useful,
even if it were in the correct orientation.

If you aren't referring to dynamic soaring then all I can say is
"huh"?

9B

9B:

The physics apply in all directions, but the potential is greatest
with positive vertical velocity gradient since that vector directly
opposes gravity- *and that's our job if we're going to stay up. The
reason the horizontal gradients are more readily recognized is that
they are often sustainable in a cycle, witness the Albatross. However,
I'm not wanting to argue about it. I know the physics and the math and
have been using them effectively for about 15 years now.

Best Regards,
Gary Osoba

Got it - sounds a bit uncomfortable since moving the velocity vector
around in the vertical axis takes a lot more aggressiveness then
horizontally. I assume it also helps to know where the boundaries of
the gradients are before you reach them. If you miss you just mush and
lose altitude fro all the induced drag.

It's the exact opposite technique from what I see and hear from most
top racing pilots who advise flying slower than McCready theory and
maintaining laminar flow over the wing with only modest maneuvering.
How do you decide when to use which technique when you are cruising
along at 15,000 feet and 85 knots and run into a 6 knot thermal?

9B