When are thermals not circular and do thermal helpers assume thatthey are?

You guys who find the WP thermal assistant so much better than others - are you running them on the same hardware with the same inputs? I hope you are not basing any comments on an Oudie using its internal GPS because it is known that the info from the internal GPS is not good enough for a thermal assistant.

On Monday, July 29, 2013 11:00:11 AM UTC-5, son_of_flubber wrote:
I'm starting to think that the textbook circular thermal is primarily a flatland phenomena.

SYM user hint.

In thermal display,tap the screen once to exit it.

On Monday, July 29, 2013 12:00:11 PM UTC-4, son_of_flubber wrote:
I'm starting to think that the textbook circular thermal is primarily a flatland phenomena.

(Am I crazy or)does a stream of wind coming through a mountain pass often interact with a series of ground generated thermals to produce a long line of lift (bordered by a parallel line of sink.) Circling just divides my time between the line of lift and the line of sink. What about flying a rectangle so that the downwind leg is not in sink? Tight turns to reverse direction at either end of the line of lift? Other strategies?

One of the pundits in our club has a simple saying. It's "God's Air", so lift is where you find it. Bubbles, pulses, streams, multiple cores, lines... you name it. Like TT mentioned above, there are some days when you find yourself screaming out loud in the cockpit wondering where the *#$%! 10kt core just went or the dreaded 6kts up and 7kts down "thermal". The circle is as good a model as any to start, but the re-centering strategy and the need constantly be executing that strategy is the real key.

FWIW, my LS4 was a glider that let you get away with "dynamically thermalling." You could haul back on the stick, slam the rudder, and sort of pirouette into a core without degrading climb performance. My LS8 is a little less forgiving of large airspeed/pitch excursions; my friends tell me the ASW-24 is even less forgiving. A lot depends upon what your particular glider can/can't do. I make it a habit to fly one of the club's 1-26s a couple of times each year, just to remember how much fun it can be to flail around in broken lift with a low wingloading glider. I think the "model" you use has to take into account flying styles and the glider as well.

P3

On Tuesday, July 30, 2013 9:34:16 AM UTC-4, son_of_flubber wrote:
On Monday, July 29, 2013 12:00:11 PM UTC-4, son_of_flubber wrote:

I'm starting to think that the textbook circular thermal is primarily a flatland phenomena.

(Am I crazy or)does a stream of wind coming through a mountain pass often interact with a series of ground generated thermals to produce a long line of lift (bordered by a parallel line of sink.) Circling just divides my time between the line of lift and the line of sink. What about flying a rectangle so that the downwind leg is not in sink? Tight turns to reverse direction at either end of the line of lift?

On 07/30/2013 9:34 AM, son_of_flubber wrote:
Other strategies?

There is only one right answer; fly in the lift, avoid the sink. Do
whatever is necessary to keep it that way BUT avoid loss due to
unnecessary control movements /attitude changes. Avoiding erratic
changes also minimizes risk of a mid-air if you are flying with other
aircraft in the same thermal.

Luke

On Tuesday, July 30, 2013 12:51:44 AM UTC-7, waremark wrote:
You guys who find the WP thermal assistant so much better than others - are you running them on the same hardware with the same inputs? I hope you are not basing any comments on an Oudie using its internal GPS because it is known that the info from the internal GPS is not good enough for a thermal assistant.

You are absolutely correct. WP Pro is only available and only work with a compatible flight computer( true airspeed and vario info added I think) and not with a stand alone gps source.
SYM, XCSoar will offer their version of the thermal assist with a stand alone gps where they should not; AS IT DOES NOT WORK without a flight computer!
But to be honest when it comes to their type of thermal assist SYM and XCSoar don't work very well with a flight computer either.
I'm sure this is all about the algorithms which they won't openly share (as in guarded secrets).
Like Tim I have used all three (and still have them installed on my Avier/Vertica2)
None measure up to WPPro when it comes to this feature. Agree; they have a lot of new and nice features I wish WP would take notes of.
(One would argue; why we need the thermal assits? Answer; why do we need flight computers, compensated varios, audio varios, or a variometer for that matter??.)
6PK

I think you've hit it jfitch. I didn't consider the polar graph.


"jfitch" wrote in message
...
On Monday, July 29, 2013 5:14:01 PM UTC-7, Tim Taylor wrote:
On Monday, July 29, 2013 10:00:11 AM UTC-6, son_of_flubber wrote:

I'm starting to think that the textbook circular thermal is primarily a
flatland phenomena.



Most of the "Thermal Assistants" will assume circular but give a
reasonable idea of the varied strength all the way around. WinPilot is the
best I have used, SeeYou Mobile is about the worst. You can choose to
adjust position from the values but in general seat feel will tell you
more most of the time. I have not seen a nice circular and even strength
thermal all the way around in months. Last Friday every thermal had
multiple cores and strong centers about 50 feet across. They would also
increase right until they dropped off a cliff. Level out into the
stronger lift and it would increase through about 10 knots and then drop
to sink instantly. I felt like a needed to go back to basic flight
training again.

+1 on Winpilot's thermal assistant being markedly better than the others.
SYM useless, XCSoar marginal on its best days.

Thermals may not be circular, but your glider flies in a pretty good
approximation of a circle. So the cylindrical graph depicted in Winpilot is
all the information you can really use. XCSoar's polar graph might fool you
into thinking that is the shape of the lift - but it is a polar graph of
strength around a fixed radius circle, not a map of the thermal. Oh yeah
they are different!

Tim were you flying the Tahoe/Minden/Truckee area? Last weekend the thermals
were diabolical.

I'll jump in here before Max does. XCSoar is open source. You can download
all of the source code and study the algorithms yourself.

I also have to ask: Do you really *need* a thermal assistant? I can fly
with the pitot tube plugged (ask me how I know), can you? Same with plugged
statics.


"6PK" wrote in message
...
On Tuesday, July 30, 2013 12:51:44 AM UTC-7, waremark wrote:
You guys who find the WP thermal assistant so much better than others -
are you running them on the same hardware with the same inputs? I hope you
are not basing any comments on an Oudie using its internal GPS because it
is known that the info from the internal GPS is not good enough for a
thermal assistant.

You are absolutely correct. WP Pro is only available and only work with a
compatible flight computer( true airspeed and vario info added I think) and
not with a stand alone gps source.
SYM, XCSoar will offer their version of the thermal assist with a stand
alone gps where they should not; AS IT DOES NOT WORK without a flight
computer!
But to be honest when it comes to their type of thermal assist SYM and
XCSoar don't work very well with a flight computer either.
I'm sure this is all about the algorithms which they won't openly share (as
in guarded secrets).
Like Tim I have used all three (and still have them installed on my
Avier/Vertica2)
None measure up to WPPro when it comes to this feature. Agree; they have a
lot of new and nice features I wish WP would take notes of.
(One would argue; why we need the thermal assits? Answer; why do we need
flight computers, compensated varios, audio varios, or a variometer for that
matter??.)
6PK

Sure I can and have many times flying simple club gliders ,it is good exercise.
But this is not the point;
We all invest in better quality equipnent why?;
In order to go farther, higher and faster.
This is just another tool one could adapt or not.
6PK

On Tuesday, July 30, 2013 7:42:18 AM UTC+2, jfitch wrote:

Pretty much what he said. I would add that the depiction of all Flarm contacts, with associated information on the Thermal Assistant page is at the very least entertaining and very good for situational awareness.

The trouble with all these graphic displays is that they require a certain amount of time to look at and analyze the data presented prior to using it to center the thermal. We use audio varios to get away from looking at a needle, and now we have pretty pictures!

I use SYM but not the climb page - instead I have a Themi that consistently reminds me to move towards the stronger part of the circle (wind corrected). Usually I've already decided to move my circle when the Themi lights up, but sometimes it does a better job of remembering where the surge is.

SYM has a provision for an aural cue to suggest when to roll out to move the circle, but haven't tried it.

Considering the age of Themi, and the fact that it uses (as far as I know) only GPS to track the thermal, I'm surprised there hasn't been a second generation Themi2 that would use better sensors to map the thermal, but still keep the simple visual cues (LEDs on the glareshield).

Kirk
66