Optimum thermalling speed display

[kirk.stant]

With all the new (and some of the older - SN10 for example) vario-computers having accelerometers and settings for ballast and polars, would it be possible to compute and display the optimum thermalling speed adjusted for wingloading and bank angle (as a function of instantaneous G-loading)?

Since we don't (yet) have AOA gauges (which would do a better job of indicating the correct speed to fly in a thermal), I'm curious if a simple "speed to fly" indication would work.

Obviously, filtering a constantly varying G-load would have to be employed, but I'm thinking of a 2-3 knot speed band display - using the same fast-slow indicator used for cruise speed control - preferably also with a deadbeat digital readout of the optimum speed to thermal for an average of the past 3 seconds or so of turn/averaged G.

Would this work? Probably only once established in a steady, smooth turn - but that would give a good starting point for the next thermal.

Kirk
66

[soartech[_2_]]

> Since we don't (yet) have AOA gauges...
> Kirk
> 66

If you want to buy one they are available. Check out www.safeflight.com
There are more listed on page 16 and 17 of the Feb 2008 issue of
Soaring.

Trying to thermal effectively while keeping your speed within a 2-3
knot range sounds
like trying to balance on a ball. I suspect the slight difference in
efficiency is not significant.

[Eric Greenwell[_4_]]

On 9/26/2012 9:49 AM, soartech wrote:
>
>> Since we don't (yet) have AOA gauges...
>> Kirk
>> 66
>
> If you want to buy one they are available. Check out www.safeflight.com
> There are more listed on page 16 and 17 of the Feb 2008 issue of
> Soaring.
>
> Trying to thermal effectively while keeping your speed within a 2-3
> knot range sounds
> like trying to balance on a ball. I suspect the slight difference in
> efficiency is not significant.

What many pilots need is a G meter that nags them to use a steeper bank
than the 20-30 degrees I often see. That would improve the their
climbing effectiveness a lot more than the optimum AOA.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

[John Cochrane[_3_]]

On Sep 25, 11:29*pm, "kirk.stant" > wrote:
> With all the new (and some of the older - SN10 for example) vario-computers having accelerometers and settings for ballast and polars, would it be possible to compute and display the optimum thermalling speed adjusted for wingloading and bank angle (as a function of instantaneous G-loading)?
>
> Since we don't (yet) have AOA gauges (which would do a better job of indicating the correct speed to fly in a thermal), I'm curious if a simple "speed to fly" indication would work.
>
> Obviously, filtering a constantly varying G-load would have to be employed, but I'm thinking of a 2-3 knot speed band display - using the same fast-slow indicator used for cruise speed control - preferably also with a deadbeat digital readout of the optimum speed to thermal for an average of the past 3 seconds or so of turn/averaged G.
>
> Would this work? Probably only once established in a steady, smooth turn - but that would give a good starting point for the next thermal.
>
> Kirk
> 66

I think it would work very nicely. Quick, if you normally thermal your
ASW27 empty at 44 knots in a 30 degree bank, what's the right speed
for 12 gals of water ballast each side? What's the right speed for 50
degrees? Accurate speed control makes a big difference. It's been on
my (rather long) punch list of requests to the clearnav team for a
while, if anyone else were asking they'd probably do it.
John Cochrane

[JS]

I have a ClearNav, love it but don't want to look at it that much.
Using "normally" and "30 degree bank" in the same sentence is a typo?
Jim

[Tim Taylor]

How about a bank angle read out on the new Butterfly vario so the guys that think they are flying a 45 degree bank can see they are really only banked 20 degrees? Not sure I need a speed to fly, usually it is as slow as the glider will fly well. Any slower it will mush or be slow on the controls, any faster and I am flying too big of circles. Too many different types of thermals for one number.

[Evan Ludeman[_4_]]

On Thursday, September 27, 2012 2:58:22 AM UTC-4, Tim Taylor wrote:
> How about a bank angle read out on the new Butterfly vario so the guys that think they are flying a 45 degree bank can see they are really only banked 20 degrees? Not sure I need a speed to fly, usually it is as slow as the glider will fly well. Any slower it will mush or be slow on the controls, any faster and I am flying too big of circles. Too many different types of thermals for one number.

Every glider in the fleet has a handy 45 degree bank angle reference. Use your instrument screws. Kilobuck solutions not required.

T8

[[email protected]]

On Thursday, September 27, 2012 6:26:50 AM UTC-5, Evan Ludeman wrote:
> On Thursday, September 27, 2012 2:58:22 AM UTC-4, Tim Taylor wrote:
>
> > How about a bank angle read out on the new Butterfly vario so the guys that think they are flying a 45 degree bank can see they are really only banked 20 degrees? Not sure I need a speed to fly, usually it is as slow as the glider will fly well. Any slower it will mush or be slow on the controls, any faster and I am flying too big of circles. Too many different types of thermals for one number.
>
>
>
> Every glider in the fleet has a handy 45 degree bank angle reference. Use your instrument screws. Kilobuck solutions not required.
>
>
>
> T8

Not sure how accurate this is, but an interesting experiment regardless...

http://www.stolaf.edu/people/hansonr/soaring/spd2fly/

[[email protected]]

On Thursday, September 27, 2012 6:26:50 AM UTC-5, Evan Ludeman wrote:
> On Thursday, September 27, 2012 2:58:22 AM UTC-4, Tim Taylor wrote:
>
> > How about a bank angle read out on the new Butterfly vario so the guys that think they are flying a 45 degree bank can see they are really only banked 20 degrees? Not sure I need a speed to fly, usually it is as slow as the glider will fly well. Any slower it will mush or be slow on the controls, any faster and I am flying too big of circles. Too many different types of thermals for one number.
>
>
>
> Every glider in the fleet has a handy 45 degree bank angle reference. Use your instrument screws. Kilobuck solutions not required.
>
>
>
> T8

Evan, I think Tim's comment was tongue in cheek...
I agree with him, why the hell do you need a thermaling speed director, what happened to good-old hand flying the glider and taking pride in the results?

[Evan Ludeman[_4_]]

On Sep 27, 1:17*pm, wrote:
> On Thursday, September 27, 2012 6:26:50 AM UTC-5, Evan Ludeman wrote:
> > On Thursday, September 27, 2012 2:58:22 AM UTC-4, Tim Taylor wrote:
>
> > > How about a bank angle read out on the new Butterfly vario so the guys that think they are flying a 45 degree bank can see they are really only banked 20 degrees? *Not sure I need a speed to fly, usually it is as slow as the glider will fly well. Any slower it will mush or be slow on the controls, any faster and I am flying too big of circles. *Too many different types of thermals for one number.
>
> > Every glider in the fleet has a handy 45 degree bank angle reference. *Use your instrument screws. *Kilobuck solutions not required.
>
> > T8
>
> Evan, I think Tim's comment was tongue in cheek...
> I agree with him, why the hell do you need a thermaling speed director, what happened to good-old hand flying the glider and taking pride in the results?

[kirk.stant]

On Thursday, September 27, 2012 12:17:38 PM UTC-5, wrote:
I agree with him, why the hell do you need a thermaling speed director, what happened to good-old hand flying the glider and taking pride in the results?

Herb, by that logic, why do you even have an airspeed indicator, or a vario? I've "hand-flown" my glider with the airspeed inop, and with the vario inop (fortunately, not at the same time), and yeah, I can do it, and even go XC if the conditions are good - but that is not the same as actually knowing what the optimum airspeed is for your weight and bank angle, so you can calibrate your "hand"!

My proposal is not for another pointer to stare at while thermalling, but as an indication of what airspeed you should be aiming for (which can vary considerably depending on wingloading and bank angle, as we all know). If your highly calibrated hand agrees, then you don't need to look at the damn thing. But if you have been flying dry for a while, then launch off at 11psf, and have to scratch up early in the day - it would be kinda nice to have that number somewhere so you can avoid scaring all your buddies...

I would still prefer a really good AOA indicator, and be done with the stupid airspeed indicator. Hey, maybe a whistle that sounds at Cl Max!

Kirk
66

[Tim Taylor]

On Sep 27, 11:30*am, "kirk.stant" > wrote:
> On Thursday, September 27, 2012 12:17:38 PM UTC-5, wrote:
>
> I agree with him, why the hell do you need a thermaling speed director, what happened to good-old hand flying the glider and taking pride in the results?
>
> Herb, by that logic, why do you even have an airspeed indicator, or a vario? I've "hand-flown" my glider with the airspeed inop, and with the vario inop (fortunately, not at the same time), and yeah, I can do it, and even go XC if the conditions are good - but that is not the same as actually knowing what the optimum airspeed is for your weight and bank angle, so you can calibrate your "hand"!
>
> My proposal is not for another pointer to stare at while thermalling, but as an indication of what airspeed you should be aiming for (which can vary considerably depending on wingloading and bank angle, as we all know). *If your highly calibrated hand agrees, then you don't need to look at the damn thing. *But if you have been flying dry for a while, then launch off at 11psf, and have to scratch up early in the day - it would be kinda nice to have that number somewhere so you can avoid scaring all your buddies...
>
> I would still prefer a really good AOA indicator, and be done with the stupid airspeed indicator. *Hey, maybe a whistle that sounds at Cl Max!
>
> Kirk
> 66

Herb, thanks! I was trying to make two points:

1. Most pilots don't/can't thermal steep enough and can't tell what
bank they are flying even when told how to look at the panel or look
outside the glider.

2. You already have an instrument to tell you optimum speed and bank
to fly, it is the variometer. There is no magic perfect speed to fly
that you can predict ahead of time. Depending on the thermal itself,
I may fly slower or faster than optimum for some equation. All those
factors come down to one number, maximum climb rate! I adjust bank
angle, speed, flap setting, slip, etc until I get the best rate of
climb for each thermal.

Tim
TT

[Peter Scholz[_3_]]

Am 27.09.2012 19:30, kirk.stant wrote:
> On Thursday, September 27, 2012 12:17:38 PM UTC-5, wrote:
> I agree with him, why the hell do you need a thermaling speed director, what happened to good-old hand flying the glider and taking pride in the results?
>
> Herb, by that logic, why do you even have an airspeed indicator, or a vario? I've "hand-flown" my glider with the airspeed inop, and with the vario inop (fortunately, not at the same time), and yeah, I can do it, and even go XC if the conditions are good - but that is not the same as actually knowing what the optimum airspeed is for your weight and bank angle, so you can calibrate your "hand"!
>
> My proposal is not for another pointer to stare at while thermalling, but as an indication of what airspeed you should be aiming for (which can vary considerably depending on wingloading and bank angle, as we all know). If your highly calibrated hand agrees, then you don't need to look at the damn thing. But if you have been flying dry for a while, then launch off at 11psf, and have to scratch up early in the day - it would be kinda nice to have that number somewhere so you can avoid scaring all your buddies...
>
> I would still prefer a really good AOA indicator, and be done with the stupid airspeed indicator. Hey, maybe a whistle that sounds at Cl Max!
>
> Kirk
> 66
>

Kirk,

look at
http://www.akaflieg-koeln.de/news/newsdetails/alles-haengt-am-seit-den-enfaden-neue-version/

It is in german, but the diagrams should give you an idea how you can
use a string on the side of your canopy as a very simple but reliable
AOA indicator.
--
Peter Scholz
ASW24 JE

[[email protected]]

On Wednesday, September 26, 2012 8:11:07 PM UTC-4, John Cochrane wrote:
> On Sep 25, 11:29*pm, "kirk.stant" > wrote: > With all the new (and some of the older - SN10 for example) vario-computers having accelerometers and settings for ballast and polars, would it be possible to compute and display the optimum thermalling speed adjusted for wingloading and bank angle (as a function of instantaneous G-loading)? > > Since we don't (yet) have AOA gauges (which would do a better job of indicating the correct speed to fly in a thermal), I'm curious if a simple "speed to fly" indication would work. > > Obviously, filtering a constantly varying G-load would have to be employed, but I'm thinking of a 2-3 knot speed band display - using the same fast-slow indicator used for cruise speed control - preferably also with a deadbeat digital readout of the optimum speed to thermal for an average of the past 3 seconds or so of turn/averaged G. > > Would this work? Probably only once established in a steady, smooth turn - but that would give a good starting point for the next thermal. > > Kirk > 66 I think it would work very nicely. Quick, if you normally thermal your ASW27 empty at 44 knots in a 30 degree bank, what's the right speed for 12 gals of water ballast each side? What's the right speed for 50 degrees? Accurate speed control makes a big difference. It's been on my (rather long) punch list of requests to the clearnav team for a while, if anyone else were asking they'd probably do it. John Cochrane

I would expect, for such a device to be effective, there would need to be quite a complex set of inputs, both from sailplane data, and sensory input.
Some examples:
1- Glider performance information for all likely flap settings used in thermalling.
2- Current mass
3- Knowledge of and the ability to quantify and input a variable for how the glider responds to horizontal and vertical gusts
4- Airspeed input, gust input- via asi , 3 axis accelerometers.
5- A harder one- what is the next gust going to be?
6- Others I'm not bright enough to think of now.

THEN- all the programmers need to do is whiz up an algorithym that takes all these into account and pops out "the number".
The vario folks are just now, 20 years after "the Dave Ellis dream", beginning to master the next level of variometry.

I'm not surprised that the ClearNav guys haven't bitten on this. It would be really hard to do in a meaningful way and maddenly difficult to try to explain to us glider jocks how to use it.
UH

[Craig Funston[_2_]]

On Thursday, September 27, 2012 3:00:02 PM UTC-7, Peter Scholz wrote:
> Am 27.09.2012 19:30, kirk.stant wrote:
>
> > On Thursday, September 27, 2012 12:17:38 PM UTC-5, wrote:
>
> > I agree with him, why the hell do you need a thermaling speed director, what happened to good-old hand flying the glider and taking pride in the results?
>
> >
>
> > Herb, by that logic, why do you even have an airspeed indicator, or a vario? I've "hand-flown" my glider with the airspeed inop, and with the vario inop (fortunately, not at the same time), and yeah, I can do it, and even go XC if the conditions are good - but that is not the same as actually knowing what the optimum airspeed is for your weight and bank angle, so you can calibrate your "hand"!
>
> >
>
> > My proposal is not for another pointer to stare at while thermalling, but as an indication of what airspeed you should be aiming for (which can vary considerably depending on wingloading and bank angle, as we all know). If your highly calibrated hand agrees, then you don't need to look at the damn thing. But if you have been flying dry for a while, then launch off at 11psf, and have to scratch up early in the day - it would be kinda nice to have that number somewhere so you can avoid scaring all your buddies...
>
> >
>
> > I would still prefer a really good AOA indicator, and be done with the stupid airspeed indicator. Hey, maybe a whistle that sounds at Cl Max!
>
> >
>
> > Kirk
>
> > 66
>
> >
>
>
>
> Kirk,
>
>
>
> look at
>
> http://www.akaflieg-koeln.de/news/newsdetails/alles-haengt-am-seit-den-enfaden-neue-version/
>
>
>
> It is in german, but the diagrams should give you an idea how you can
>
> use a string on the side of your canopy as a very simple but reliable
>
> AOA indicator.
>
> --
>
> Peter Scholz
>
> ASW24 JE

More strings on canopies = windfall for Bumper. Well done ;-)

[Uncle Fuzzy[_2_]]

I probably thermal too slowly and with too much bank. Lately it seems every time I try to open up the turn even a little I blow out the edge of the thermal.
Having an instrument to yell at me might improve my thermalling, or really **** me off!

On Tuesday, September 25, 2012 9:29:44 PM UTC-7, kirk.stant wrote:
> With all the new (and some of the older - SN10 for example) vario-computers having accelerometers and settings for ballast and polars, would it be possible to compute and display the optimum thermalling speed adjusted for wingloading and bank angle (as a function of instantaneous G-loading)? Since we don't (yet) have AOA gauges (which would do a better job of indicating the correct speed to fly in a thermal), I'm curious if a simple "speed to fly" indication would work. Obviously, filtering a constantly varying G-load would have to be employed, but I'm thinking of a 2-3 knot speed band display - using the same fast-slow indicator used for cruise speed control - preferably also with a deadbeat digital readout of the optimum speed to thermal for an average of the past 3 seconds or so of turn/averaged G. Would this work? Probably only once established in a steady, smooth turn - but that would give a good starting point for the next thermal. Kirk 66

[John Roche-Kelly]

Last year I became a syndicate partner in a lovely LS7 (without
winglets). Our panel contains an LNAV which has the optional g
meter and the climb tone changes in lift if the angle of bank is too
great and the glider approaches the stall. Best thermalling speed is
just slow enough for the tone not to change. It is even possible to
change the ballast setting on the LNAV; works for us.

I am always struck by the inability of bloggs to bank at 45 degrees.
The screws on the panel trick works and many are quite surprised
at how steep this feels. They are then even more surprised by how
much the stalling speed goes up!

Tally ho!

John

[John Roche-Kelly]

Last year I became a syndicate partner in a lovely LS7 (without
winglets). Our panel contains an LNAV which has the optional g
meter and the climb tone changes in lift if the angle of bank is too
great and the glider approaches the stall. Best thermalling speed is
just slow enough for the tone not to change. It is even possible to
change the ballast setting on the LNAV; works for us.

I am always struck by the inability of bloggs to bank at 45 degrees.
The screws on the panel trick works and many are quite surprised
at how steep this feels. They are then even more surprised by how
much the stalling speed goes up!

Tally ho!

John

[Jim White[_3_]]

Two thoughts on this:

1) There is no substitute for practice.
2) If you need a computer for everything you might as well let the computer
fly the glider. Why have the middleman?



At 10:58 28 September 2012, John Roche-Kelly wrote:
>Last year I became a syndicate partner in a lovely LS7 (without
>winglets). Our panel contains an LNAV which has the optional g
>meter and the climb tone changes in lift if the angle of bank is too
>great and the glider approaches the stall. Best thermalling speed is
>just slow enough for the tone not to change. It is even possible to
>change the ballast setting on the LNAV; works for us.
>
>I am always struck by the inability of bloggs to bank at 45 degrees.
>The screws on the panel trick works and many are quite surprised
>at how steep this feels. They are then even more surprised by how
>much the stalling speed goes up!
>
>Tally ho!
>
>John
>
>

[kirk.stant]

On Thursday, September 27, 2012 3:50:35 PM UTC-6, Tim Taylor wrote:
>
> 1. Most pilots don't/can't thermal steep enough and can't tell what
>
> bank they are flying even when told how to look at the panel or look
>
> outside the glider.
>
>
>
> 2. You already have an instrument to tell you optimum speed and bank
>
> to fly, it is the variometer. There is no magic perfect speed to fly
>
> that you can predict ahead of time. Depending on the thermal itself,
>
> I may fly slower or faster than optimum for some equation. All those
>
> factors come down to one number, maximum climb rate! I adjust bank
>
> angle, speed, flap setting, slip, etc until I get the best rate of
>
> climb for each thermal.

Tim, I totally agree about bank angle - steep is good! And I mostly agree on your second point, about varying a bunch of parameters to find what works best in any particular thermal. Where I disagree, probably due to less experience, is that there isn't room for better instumentation to tell the pilot what exactly his glider is doing. Min sink is min sink - it only happens at one angle of attack. That equates to one unique airspeed for every combination of bank angle and wing loading. Think of it as Mcready speed - a wonderful invention, gives the theoretical optimum cruise speed to fly, made cross country faster, etc.. and all our fancy computers give us a variety of indicators on how fast to fly, when to push or pull, audio tones, etc.. Of course, a lot of us just use it as a guide and adjust our speed for the conditions at hand, since the bloody black box isn't looking out the window!

I'm just thinking that the equivalent for thermalling might be useful.

Cheers,

Kirk
66

[kirk.stant]

On Friday, September 28, 2012 6:30:03 AM UTC-6, Jim White wrote:
> Two thoughts on this:
>
>
>
> 1) There is no substitute for practice.
>
> 2) If you need a computer for everything you might as well let the computer
>
> fly the glider. Why have the middleman?

I'm confused, Jim: Do you have a vario in your glider? Or a glide computer? PNA?

How does having real time information on a variable performance value (min sink speed for current conditions) equate to letting the computer fly the glider?

Kirk

[Evan Ludeman[_4_]]

On Friday, September 28, 2012 8:55:30 AM UTC-4, kirk.stant wrote:
> On Thursday, September 27, 2012 3:50:35 PM UTC-6, Tim Taylor wrote:
>
> >
>
> > 1. Most pilots don't/can't thermal steep enough and can't tell what
>
> >
>
> > bank they are flying even when told how to look at the panel or look
>
> >
>
> > outside the glider.
>
> >
>
> >
>
> >
>
> > 2. You already have an instrument to tell you optimum speed and bank
>
> >
>
> > to fly, it is the variometer. There is no magic perfect speed to fly
>
> >
>
> > that you can predict ahead of time. Depending on the thermal itself,
>
> >
>
> > I may fly slower or faster than optimum for some equation. All those
>
> >
>
> > factors come down to one number, maximum climb rate! I adjust bank
>
> >
>
> > angle, speed, flap setting, slip, etc until I get the best rate of
>
> >
>
> > climb for each thermal.
>
>
>
> Tim, I totally agree about bank angle - steep is good! And I mostly agree on your second point, about varying a bunch of parameters to find what works best in any particular thermal. Where I disagree, probably due to less experience, is that there isn't room for better instumentation to tell the pilot what exactly his glider is doing. Min sink is min sink - it only happens at one angle of attack. That equates to one unique airspeed for every combination of bank angle and wing loading. Think of it as Mcready speed - a wonderful invention, gives the theoretical optimum cruise speed to fly, made cross country faster, etc.. and all our fancy computers give us a variety of indicators on how fast to fly, when to push or pull, audio tones, etc... Of course, a lot of us just use it as a guide and adjust our speed for the conditions at hand, since the bloody black box isn't looking out the window!
>
>
>
> I'm just thinking that the equivalent for thermalling might be useful.
>
>
>
> Cheers,
>
>
>
> Kirk
>
> 66

Best climb isn't achieved at minimum sink. Usually (90%), it pays (in climb) to fly slower than (load factor corrected) minimum sink speed. The optimum is going to be very slippery -- it depends as much on the thermal characteristics, turbulence, etc. as it does on glider performance. It's this sort of abstract, complicated, multivariable, analog "computing" that humans can still do better than machines (with enough practice). Enjoy it while it lasts!

-Evan Ludeman / T8

[[email protected]]

Please explain in more detail. Not clear what you mean by "optimum is going to be very slippery." Are you saying that the benefit of slower flight and therefore tighter radius circles outweigh the losses from the higher sink rate? Not trying to be a smart alec, I seriously want to learn from you more experienced guys. thank you.

Robert

On Friday, September 28, 2012 9:25:17 AM UTC-5, Evan Ludeman wrote:
>
> Best climb isn't achieved at minimum sink. Usually (90%), it pays (in climb) to fly slower than (load factor corrected) minimum sink speed. The optimum is going to be very slippery -- it depends as much on the thermal characteristics, turbulence, etc. as it does on glider performance. It's this sort of abstract, complicated, multivariable, analog "computing" that humans can still do better than machines (with enough practice). Enjoy it while it lasts!
>
>
>
> -Evan Ludeman / T8

[Evan Ludeman[_4_]]

Ye Gods, are we top posting or bottom posting in this thread :-)?

"Slippery" in the sense of elusive, ever changing, fiendishly difficult to calculate in real time.

2nd part: Yes, exactly, smaller circle (v < min sink) yields better climb in most (classic small, round, columnar, strong at the core) thermals. Uncenterable lift or really huge thermals are typical exceptions.

-Evan Ludeman / T8

On Friday, September 28, 2012 10:39:21 AM UTC-4, (unknown) wrote:
> Please explain in more detail. Not clear what you mean by "optimum is going to be very slippery." Are you saying that the benefit of slower flight and therefore tighter radius circles outweigh the losses from the higher sink rate? Not trying to be a smart alec, I seriously want to learn from you more experienced guys. thank you.
>
>
>
> Robert
>
>
>
> On Friday, September 28, 2012 9:25:17 AM UTC-5, Evan Ludeman wrote:
>
> >
>
> > Best climb isn't achieved at minimum sink. Usually (90%), it pays (in climb) to fly slower than (load factor corrected) minimum sink speed. The optimum is going to be very slippery -- it depends as much on the thermal characteristics, turbulence, etc. as it does on glider performance. It's this sort of abstract, complicated, multivariable, analog "computing" that humans can still do better than machines (with enough practice). Enjoy it while it lasts!
>
> >
>
> >
>
> >
>
> > -Evan Ludeman / T8

[Grider Pirate[_2_]]

On Sep 28, 7:48*am, Evan Ludeman > wrote:
> Ye Gods, are we top posting or bottom posting in this thread :-)?
>
> "Slippery" in the sense of elusive, ever changing, fiendishly difficult to calculate in real time.
>
> 2nd part: Yes, exactly, smaller circle (v < min sink) yields better climb in most (classic small, round, columnar, strong at the core) thermals. *Uncenterable lift or really huge thermals are typical exceptions.
>
> -Evan Ludeman / T8
>
>
>
> On Friday, September 28, 2012 10:39:21 AM UTC-4, (unknown) wrote:
> > Please explain in *more detail. *Not clear what you mean by "optimum is going to be very slippery." *Are you saying that the benefit of slower flight and therefore tighter radius circles outweigh the losses from the higher sink rate? *Not trying to be a smart alec, I seriously want to learn from you more experienced guys. thank you.
>
> > Robert
>
> > On Friday, September 28, 2012 9:25:17 AM UTC-5, Evan Ludeman wrote:
>
> > > Best climb isn't achieved at minimum sink. *Usually (90%), it pays (in climb) to fly slower than (load factor corrected) minimum sink speed. *The optimum is going to be very slippery -- it depends as much on the thermal characteristics, turbulence, etc. as it does on glider performance. *It's this sort of abstract, complicated, multivariable, analog "computing" that humans can still do better than machines (with enough practice). *Enjoy it while it lasts!
>
> > > -Evan Ludeman / T8- Hide quoted text -
>
> - Show quoted text -

The key point Evan makes (and I totally agree!) is that the strongest
lift is closest to the the center of a thermal, so flying slower
smaller diameter spirals will increase climb rate even though the
increased bank decreases the vertical component of lift. I had
opportunity to fly with some paragliders (with JS ) and even though
the paraglider min-sink isn't good, they outclimbed us because they
can fly such a small circle, and stay in the strongest lift.

[Jim Wallis[_2_]]

So is the target bank angle always 45 degrees (with slowest safe speed for
that bank) or would you give up bank angle to slow down more i.e. focus on
speed control. Which gives you the tightest circle?

- Jim





>
>The key point Evan makes (and I totally agree!) is that the strongest
>lift is closest to the the center of a thermal, so flying slower
>smaller diameter spirals will increase climb rate even though the
>increased bank decreases the vertical component of lift. I had
>opportunity to fly with some paragliders (with JS ) and even though
>the paraglider min-sink isn't good, they outclimbed us because they
>can fly such a small circle, and stay in the strongest lift.
>

[kirk.stant]

Evan,

I wonder if there has been a study done on tradeoffs between sink rate and circle size. Of course, the problem is that thermals are not very consistent...

And just to make things clear, I also vary my speed and bank angle until I find what I think is the best climb.

But I disagree that the best speed cannot be somewhat quantified. Stall is obviously the slowest - and that speed changes based on at least two variables. How far above stall - up to CL max, or perhaps even faster in a tight, turbulent thermal at 60 degrees of bank) is optimum? Without knowing what stall speed or min sink is, you are guessing or relying on experience or glider feedback. If you are not experienced, or your glide does not give much feedback, you are left with guessing - probably on the high side because of all the "stall spin" stories you have read here on RAS.

So if it is easy to display, in real time, what stall/min sink/Cl max is at your current flight condition, that data helps calibrate your "experience" quicker.

I find it amusing that we are raving about new technology varios and debating the relative merits of PNA thermal centering displays, while the airspeed cue we display in the cockpit to use all the new info is still just a mechanical airspeed indicator. Some gliders talk a lot, so that monitoring the airspeed is not very necessary. Others, like my ls6, have very little change in feel from the stall up to ridiculously high thermalling speeds - only the nose position relative to the horizon is a givaway to how fast I'm flying, once trimmed up. So the technique of pulling till you feel the stall buffet and easing off doesn't work very well!

Anyway- interesting discussion.

Cheers - gotta go give a glider ride.

Kirk
66

[Eric Greenwell[_4_]]

On 9/29/2012 7:49 AM, kirk.stant wrote:
> So the technique of pulling till you feel the stall buffet and easing
> off doesn't work very well!

Many gliders, like my ASH 26 E, the DG 800, and others, have a "flat
spot" in the airfoil lift drag curve, and climb better in "turbulent"
thermals when flown significantly faster than just above the stall
buffet. An indicator would be especially helpful for these gliders.
Also, even the stall buffet is hard to detect above about 40 degrees
bank, at least with my CG.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

[[email protected]]

On Saturday, September 29, 2012 2:30:04 AM UTC-4, Jim Wallis wrote:
> So is the target bank angle always 45 degrees (with slowest safe speed for that bank) or would you give up bank angle to slow down more i.e. focus on speed control. Which gives you the tightest circle? - Jim > >The key point Evan makes (and I totally agree!) is that the strongest >lift is closest to the the center of a thermal, so flying slower >smaller diameter spirals will increase climb rate even though the >increased bank decreases the vertical component of lift. I had >opportunity to fly with some paragliders (with JS ) and even though >the paraglider min-sink isn't good, they outclimbed us because they >can fly such a small circle, and stay in the strongest lift. >

There is no "always". The bank angle for best climb must take into acoount sink rate of the glider as well as the gradient of thermal strength with respect to thermal size. Then throw in that many thermals are not round and require bank changes. Add to this that, as bank changes, speed should change slightly, while anticipating the next gust or slacking of lift. And, just to make it a bit more complicated, avoid the angle of attack where the lift vs angle of attack gradient is unfavorable.
Funny how flying for a week or so in concentrated manner makes this easier to do.
UH

[Evan Ludeman[_4_]]

On Saturday, September 29, 2012 10:49:36 AM UTC-4, kirk.stant wrote:
> Evan,
>
>
>
> I wonder if there has been a study done on tradeoffs between sink rate and circle size. Of course, the problem is that thermals are not very consistent...
>
>
>
> And just to make things clear, I also vary my speed and bank angle until I find what I think is the best climb.
>
>
>
> But I disagree that the best speed cannot be somewhat quantified. Stall is obviously the slowest - and that speed changes based on at least two variables. How far above stall - up to CL max, or perhaps even faster in a tight, turbulent thermal at 60 degrees of bank) is optimum? Without knowing what stall speed or min sink is, you are guessing or relying on experience or glider feedback. If you are not experienced, or your glide does not give much feedback, you are left with guessing - probably on the high side because of all the "stall spin" stories you have read here on RAS.
>
>
>
> So if it is easy to display, in real time, what stall/min sink/Cl max is at your current flight condition, that data helps calibrate your "experience" quicker.
>
>
>
> I find it amusing that we are raving about new technology varios and debating the relative merits of PNA thermal centering displays, while the airspeed cue we display in the cockpit to use all the new info is still just a mechanical airspeed indicator. Some gliders talk a lot, so that monitoring the airspeed is not very necessary. Others, like my ls6, have very little change in feel from the stall up to ridiculously high thermalling speeds - only the nose position relative to the horizon is a givaway to how fast I'm flying, once trimmed up. So the technique of pulling till you feel the stall buffet and easing off doesn't work very well!
>
>
>
> Anyway- interesting discussion.
>
>
>
> Cheers - gotta go give a glider ride.
>
>
>
> Kirk
>
> 66

The LS-6 is a much loved glider, what gives? My 20 gives plenty of feedback. Here's how I train T8's pilot: instrument covers. Climb to top of convection, cover everything but altimeter and averager, no audio. Great for back to basics.

As far as calculating the optimum way to climb, we do trade studies several times a year. We call 'em "contests" :-). I find them effective.

Seriously, given an accurate mathematical description of any given thermal, any given sailplane, you could of course, find an optimum. That's been hashed out for simple cases in Reichmann, other places. It's probably all valid, but it puts me to sleep.

As far as Nav instruments and all the rest... well, I've tried a bunch. On the ClearNav team since June (end user and part time associate, just to be clear). Like that a lot. I've tried the thermal assistants in various devices to see what they do. I found one of them useful for a while a couple of years ago (WinPilot) until I discovered my real problem was a buggy, jumpy electric vario (with smooth nmea output so the thermal assistant worked fine). With the vario problem solved I no longer have any use for that stuff.

What I like about the CN is speed of info acquisition. Glance, and done. It doesn't try to tell me how to fly, I'm not going to have to hassle with anyone about an AHRS disabled mode, it doesn't show me pictures of off field landing sites, it doesn't have the amazing in flight statistical analysis of thermals and wind that some other devices do. While I found the statistics useful (or thought I did)... the statistic I really like is that is that I fly one helluva lot better in competition on CN than I do on anything else. I don't think that was a fluke. It was simply figuring out a Nav setup that doesn't get in my way.

-Evan Ludeman / T8

PS Cheers, got to go to a birthday party (it's raining, no loss :-))

[kirk.stant]

Evan, it must be nice to have the time and opportunity to fly enough contest to stay on the peak of performance.

However, not everyone has the ability or time to do this. And a newcomer to the sport may be having enough trouble absorbing all that is going on without having to figure out how to determine in real time the optimum airspeed to thermal by trial an error!

For the 47 percent of us who are not yet retired or independently wealthy, every little bit helps - just saying "go out and buy the best nav display and practice a lot and go to a lot of contests and you will figure it out" isn't going to hack it.

There has to be a starting point for thermaling speed. Aerodynamically, that's probably best represented by min sink for the bank angle and wing loading. From then on, you are in the realm of technique and glider idiosyncrasies - where experience and flying time makes the difference. What I'm asking is is it possible to at least display the basics, to make learning the techniques easier.

I think it would be helpful. You hotshots who zen-thermal can continue to do so - having data available doesn't mean it has to be used slavishly!

And in regards to my LS6 comments - it is by far the easiest racing glider I have flown. When thermalling, you can slow down to the point you start to mush without any tendency to drop a wing or spin. But since there is so little pre-stall indications (no buffet, controls stay responsive, etc) it is not practicable (at least not for me - others are welcome to disagree) to just slow down then add a few knots. I like to have an airspeed target to shoot for - usually by setting what I know is the approximate AOA via nose position, then adjusting airspeed as necessary. All while trying to figure out where the center of the thermal went...and dodging the 2-33 blundering around in the middle.

CN looks nice. I've also found that SYM can be customized to display only the info I want, where I want it, when I want it. I like that. I agree that the tendency seems to be to generate and display a lot of data - interesting data sometimes, but mostly just eye-candy, that does nothing to make you go faster.

Keep up the good work with the CN!

Kirk
66

[Jim Wallis[_2_]]

OK. I have that. And I have reviewed my Reichmann, who basically says the
same thing which is to set the turn according to the shape of the thermal.
Interestingly relative to this thread, he goes on to say that for each
turn radius (well, "thermal gradient"), there is a single optimum airspeed
and a single optimum bank angle.

What I was musing about, however, although I didn't really express it very
well, was whether there is always a decrease in turn radius with an
increase in bank angle (assuming that one stays a constant speed above
stall), or if that curve might "invert" in certain cases.

- Jim




At 16:19 29 September 2012, wrote:
>On Saturday, September 29, 2012 2:30:04 AM UTC-4, Jim Wallis wrote:
>> So is the target bank angle always 45 degrees (with slowest safe speed
>fo=
>r that bank) or would you give up bank angle to slow down more i.e. focus
>o=
>n speed control. Which gives you the tightest circle? - Jim > >The key
>poin=
>t Evan makes (and I totally agree!) is that the strongest >lift is
closest
>=
>to the the center of a thermal, so flying slower >smaller diameter
spirals
>=
>will increase climb rate even though the >increased bank decreases the
>vert=
>ical component of lift. I had >opportunity to fly with some paragliders
>(wi=
>th JS ) and even though >the paraglider min-sink isn't good, they
>outclimbe=
>d us because they >can fly such a small circle, and stay in the strongest
>l=
>ift. >
>
>There is no "always". The bank angle for best climb must take into
acoount
>=
>sink rate of the glider as well as the gradient of thermal strength with
>re=
>spect to thermal size. Then throw in that many thermals are not round and
>r=
>equire bank changes. Add to this that, as bank changes, speed should
>change=
> slightly, while anticipating the next gust or slacking of lift. And,
just
>=
>to make it a bit more complicated, avoid the angle of attack where the
>lift=
> vs angle of attack gradient is unfavorable.
>Funny how flying for a week or so in concentrated manner makes this
easier
>=
>to do.
>UH
>

[Jim Wallis[_2_]]

I have answered my own question. I was distracted by my recollection the
axiom that flying slower reduces the radius of the turn but, of course,
that isn't relevant if you are always flying at a fixed amount above stall.
It is clarified in this quote from another forum (pprune.org):

"As the speed is increased from the straight and level stall speed, the
radius of turn can be reduced by increasing the angle of bank. However, a
radius and speed are reached where the load factor is at a maximum for the
structure. Any further increase will overstress the structure. Thus the
radius of turn will increase, as the speed is further increased at constant
angle of bank. The speed corresponding to the minimum radius turn is called
the manoeuvre speed.
At speeds below the manoeuvre speed, the maximum (or limiting) load factor
cannot be produced aerodynamically i.e. the angle of bank is limited by the
maximum lift coefficient. At speeds above the manoeuvre speed, an increase
in the angle of attack to produce maximum lift coefficient, will produce a
load factor higher than the limit load factor i.e. it will overstress the
structure."

It was useful for me to see this discussed starting from the straight and
level stall speed (i.e. the speed that doesn't permit turns at all)

So, (to try to bring my digression back in line with the thread topic!) it
does seem like the most useful information would be how much speed you are
above stall speed for any given bank angle.

- Jim




At 16:19 29 September 2012, wrote:
>On Saturday, September 29, 2012 2:30:04 AM UTC-4, Jim Wallis wrote:
>> So is the target bank angle always 45 degrees (with slowest safe speed
>fo=
>r that bank) or would you give up bank angle to slow down more i.e. focus
>o=
>n speed control. Which gives you the tightest circle? - Jim > >The key
>poin=
>t Evan makes (and I totally agree!) is that the strongest >lift is
closest
>=
>to the the center of a thermal, so flying slower >smaller diameter
spirals
>=
>will increase climb rate even though the >increased bank decreases the
>vert=
>ical component of lift. I had >opportunity to fly with some paragliders
>(wi=
>th JS ) and even though >the paraglider min-sink isn't good, they
>outclimbe=
>d us because they >can fly such a small circle, and stay in the strongest
>l=
>ift. >
>
>There is no "always". The bank angle for best climb must take into
acoount
>=
>sink rate of the glider as well as the gradient of thermal strength with
>re=
>spect to thermal size. Then throw in that many thermals are not round and
>r=
>equire bank changes. Add to this that, as bank changes, speed should
>change=
> slightly, while anticipating the next gust or slacking of lift. And,
just
>=
>to make it a bit more complicated, avoid the angle of attack where the
>lift=
> vs angle of attack gradient is unfavorable.
>Funny how flying for a week or so in concentrated manner makes this
easier
>=
>to do.
>UH
>

[Evan Ludeman[_4_]]

On Saturday, September 29, 2012 9:13:23 PM UTC-4, kirk.stant wrote:
> Evan, it must be nice to have the time and opportunity to fly enough contest to stay on the peak of performance.
>
>
>
> However, not everyone has the ability or time to do this. And a newcomer to the sport may be having enough trouble absorbing all that is going on without having to figure out how to determine in real time the optimum airspeed to thermal by trial an error!
>
>
>
> For the 47 percent of us who are not yet retired or independently wealthy, every little bit helps - just saying "go out and buy the best nav display and practice a lot and go to a lot of contests and you will figure it out" isn't going to hack it.
>
>
>
> There has to be a starting point for thermaling speed. Aerodynamically, that's probably best represented by min sink for the bank angle and wing loading. From then on, you are in the realm of technique and glider idiosyncrasies - where experience and flying time makes the difference. What I'm asking is is it possible to at least display the basics, to make learning the techniques easier.
>
>
>
> I think it would be helpful. You hotshots who zen-thermal can continue to do so - having data available doesn't mean it has to be used slavishly!
>
>
>
> And in regards to my LS6 comments - it is by far the easiest racing glider I have flown. When thermalling, you can slow down to the point you start to mush without any tendency to drop a wing or spin. But since there is so little pre-stall indications (no buffet, controls stay responsive, etc) it is not practicable (at least not for me - others are welcome to disagree) to just slow down then add a few knots. I like to have an airspeed target to shoot for - usually by setting what I know is the approximate AOA via nose position, then adjusting airspeed as necessary. All while trying to figure out where the center of the thermal went...and dodging the 2-33 blundering around in the middle.
>
>
>
> CN looks nice. I've also found that SYM can be customized to display only the info I want, where I want it, when I want it. I like that. I agree that the tendency seems to be to generate and display a lot of data - interesting data sometimes, but mostly just eye-candy, that does nothing to make you go faster.
>
>
>
> Keep up the good work with the CN!
>
>
>
> Kirk
>
> 66

Kirk,

Who are you calling hotshot? Go look at your own contest record. Kirk, you've done some pretty kick ass contest flying with that LS-6. To do that, you pretty much have to wear the glider. This just doesn't square up with your statements above, leaving me rather puzzled.

I think most of us would agree that as far as overall climb performance goes, the order of importance is 1) path selection, 2) thermal selection, 3) efficient centering, 4) leaving before lift goes soft, 5) optimization of the climb. So I guess what's going on here is that you have mastered #1 - 4 and have only #5 left to work on -- good for you!

FWIW, I think that the behavior you ascribe to the '6 -- essentially being happy to thermal at a very wide range of speeds -- is a good thing. It indicates a broad optimum in the ship's performance curves and allows the pilot to change it up as conditions or personal preference dictates. If that's true, then there probably isn't too much to be gained by trying to zero in on an exact optimum. My speculative $0.02, anyway.

Nav tools: I have learned the hard way -- you don't get to know these things until you fly 'em hard. Anything works for recreational flying. the real bargain out there is XCSoar (free) on a readable android device (I have Dell Streak 5 and it is really good). But I gave up on XCS as a contest tool earlier this year after it $%^&ed up in flight one too many times and the developers indicated that contest flying just wasn't their priority. Contest winners in USA are mostly (my unscientific survey) flying CN and SN-10. These tools are vastly more robust in the contest flying environment. As an example, you can power cycle ClearNav on task and it will recover gracefully with a valid igc log and accurate times and stats. That's the sort of industrial strength you pay the big bucks for.

-Evan Ludeman / T8

[kirk.stant]

Evan, you are making me blush..

To reign this all back to my original question - I guess I'm an AOA freak (comes from years playing around with F-4s and F-15s (real and simulated) where AOA is a constant companion and an important performance indicator.

I like AOA - airspeed in a turning environment only indicates energy, not performance. Ideally, I could do a hard pull into the core of a thermal, looking out the window for traffic in the thermal, roll into the turn, then without looking in get a cue that I'm fast/slow/close to the optimum speed for my WL and bank angle. All heads out.

Since I can't get a helmet mounted display into my cockpit (plus they are heavy and uncomfortable!), and retrofitting an AOA indicator is too complicated and expensive right now - and the ones out there are really stall preventers, not performance indicators - that leaves using some of the processing and sensors already in the cockpit.

Guess I'm enough of a control/tech freak to want another bell and/or whistle!

Would it make me fly better? Late in the season, probably not - for all the excellent reasons you (and others) have stated. But early in the season? I think so. It would be fun to find out.

SN10s rock. Tied to a carefully optimized Oudie, I'm happy.

Perhaps we should all move down under for the winter season and continue this research in the air!

These discussions (virtual post-flight bull**** sessions on the clubhouse deck, really) are fun - I'm amazed we have managed in RAS to keep civil discourse going, compared to most other aviation forums!

Cheers, today I'm off to watch NHRA drag races - about as opposite from soaring as you can get.

Cheers

Kirk
66

[[email protected]]

Hello fellow glider pilots,

There has been a study of tradeoffs between bank angle and speed.
See the video:

http://www.youtube.com/watch?v=EO9nXPRkWKk&list=PL72FAF76B0C48EECC&feature=mh_lolz

Or search for "Analysis of circling flight during thermalling".

Let me know what you tink.

On Saturday, September 29, 2012 5:13:48 PM UTC-4, Skypilot wrote:
> 'Evan Ludeman[_4_ Wrote: > ;825243']On Saturday, September 29, 2012 10:49:36 AM UTC-4, kirk.stant > wrote:[color=blue][i] > Evan,I wonder if there has been a study done on tradeoffs between sink > rate and circle size. Of course, the problem is that thermals are not > very consistent...And just to make things clear, I also vary my speed > and bank angle until I find what I think is the best climb.But I > disagree that the best speed cannot be somewhat quantified. Stall is > obviously the slowest - and that speed changes based on at least two > variables. How far above stall - up to CL max, or perhaps even faster in > a tight, turbulent thermal at 60 degrees of bank) is optimum? Without > knowing what stall speed or min sink is, you are guessing or relying on > experience or glider feedback. If you are not experienced, or your > glide does not give much feedback, you are left with guessing - probably > on the high side because of all the "stall spin" stories you have read > here on RAS. So if it is easy to display, in real time, what stall/min > sink/Cl max is at your current flight condition, that data helps > calibrate your "experience" quicker. I find it amusing that we are > raving about new technology varios and debating the relative merits of > PNA thermal centering displays, while the airspeed cue we display in the > cockpit to use all the new info is still just a mechanical airspeed > indicator. Some gliders talk a lot, so that monitoring the airspeed is > not very necessary. Others, like my ls6, have very little change in > feel from the stall up to ridiculously high thermalling speeds - only > the nose position relative to the horizon is a givaway to how fast I'm > flying, once trimmed up. So the technique of pulling till you feel the > stall buffet and easing off doesn't work very well! Anyway- interesting > discussion. > Cheers f > > Just ring up Mr Borgelt and get him to design one of these with a bar > display system to sit on top of the dash. Attach it to an autopilot > attached to a thermal assistant. Plug it all in to a remote control Uav > system and fly from the pub. How cool would that be :) +-------------------------------------------------------------------+ |Filename: AOA.jpg | |Download: http://www.aviationbanter.com/attachment.php?attachmentid=59906| +-------------------------------------------------------------------+ -- Skypilot

fellow glider pilots.

[Tony V]

On 10/2/2012 11:56 PM, wrote:
> Hello fellow glider pilots,
>
> There has been a study of tradeoffs between bank angle and speed.

The Soaring Flight Manual (sadly no longer in print) had a nice diagram
that showed these tradeoffs:

http://home.comcast.net/~verhulst/GBSC/student/images/TurnRadius.JPG

Tony "6N"


> See the video:
>
> http://www.youtube.com/watch?v=EO9nXPRkWKk&list=PL72FAF76B0C48EECC&feature=mh_lolz
>
> Or search for "Analysis of circling flight during thermalling".
>
> Let me know what you tink.
>
> On Saturday, September 29, 2012 5:13:48 PM UTC-4, Skypilot wrote:
>> 'Evan Ludeman[_4_ Wrote: > ;825243']On Saturday, September 29, 2012 10:49:36 AM UTC-4, kirk.stant > wrote:[color=blue][i] > Evan,I wonder if there has been a study done on tradeoffs between sink > rate and circle size. Of course, the problem is that thermals are not > very consistent...And just to make things clear, I also vary my speed > and bank angle until I find what I think is the best climb.But I > disagree that the best speed cannot be somewhat quantified. Stall is > obviously the slowest - and that speed changes based on at least two > variables. How far above stall - up to CL max, or perhaps even faster in > a tight, turbulent thermal at 60 degrees of bank) is optimum? Without > knowing what stall speed or min sink is, you are guessing or relying on > experience or glider feedback. If you are not experienced, or your > glide does not give much feedback, you are left with guessing - probably > on the high side because of all the "stall spin" stories you have read > here o
n RAS. So if it is easy to display, in real time, what stall/min > sink/Cl max is at your current flight condition, that data helps > calibrate your "experience" quicker. I find it amusing that we are > raving about new technology varios and debating the relative merits of > PNA thermal centering displays, while the airspeed cue we display in the > cockpit to use all the new info is still just a mechanical airspeed > indicator. Some gliders talk a lot, so that monitoring the airspeed is > not very necessary. Others, like my ls6, have very little change in > feel from the stall up to ridiculously high thermalling speeds - only > the nose position relative to the horizon is a givaway to how fast I'm > flying, once trimmed up. So the technique of pulling till you feel the > stall buffet and easing off doesn't work very well! Anyway- interesting > discussion. > Cheers f > > Just ring up Mr Borgelt and get him to design one of these with a bar > display system to sit on top of the dash. A
ttach it to an autopilot > attached to a thermal assistant. Plug it all in to a remote control Uav > system and fly from the pub. How cool would that be :) +-------------------------------------------------------------------+ |Filename: AOA.jpg | |Download: http://www.aviationbanter.com/attachment.php?attachmentid=59906| +-------------------------------------------------------------------+ -- Skypilot
>
> fellow glider pilots.
>

[[email protected]]

Check these videos and pass them around.

https://www.youtube.com/watch?v=EO9nXPRkWKk

[[email protected]]

https://www.youtube.com/watch?v=EO9nXPRkWKk

[AS]

On Monday, August 14, 2017 at 8:58:21 PM UTC-4, wrote:
> https://www.youtube.com/watch?v=EO9nXPRkWKk

Both links above are for part 1.
Part 2 is here:
https://www.youtube.com/results?search_query=Analysis+of+circling+flight+d uring+thermalling+2

Uli
'AS'

[Dan Daly[_2_]]

On Wednesday, October 3, 2012 at 3:42:53 PM UTC-4, Tony V wrote:
> On 10/2/2012 11:56 PM, wrote:
> > Hello fellow glider pilots,
> >
> > There has been a study of tradeoffs between bank angle and speed.
>
> The Soaring Flight Manual (sadly no longer in print) had a nice diagram
> that showed these tradeoffs:
>
> http://home.comcast.net/~verhulst/GBSC/student/images/TurnRadius.JPG
>
> Tony "6N"

When I try the link I get:

Sorry, we couldn't find that page.

The page you are looking for may have been moved, updated or deleted.
Suggested Actions

Please check the address (URL) you entered for proper spelling. Make sure that no capital letters or spaces are used.
You may find what you're looking for by visiting the my.xfinity.com homepage or the site map.

Still need help? Let us know.
***

I'm in Canada.

[Squeaky]

OK,

I wonder about speeds/angles to fly, so I play with calculators too, then try it out.

Here's why. As mentioned, if speed stays the same, increased bank results in decreased radius. Decreased radius results in getting to the strongest part of the thermal. Therefore it should be simple--bank it up right? Except, as you increase bank, you increase AoA, you increase stall speed, and you increase sink (and min sink speed).

Simple example, so my Glider stalls @ 36 Knots; min sink is 41kts (Level flight). So I enter a turn at 35 degrees of bank at 41 kts. And I get a 427 foot diameter turn. BUT, my stall speed is now 40, and my best min sink speed is now higher than 41. Does the increase in the thermal lift at this turn diameter/airspeed-offset the higher sink by not flying at the new min sink (which would increase the radius at the same bank?)??? Should I stay slow or speed up? Can I handle/manage the 1 knot stall margin, do I have full tail/turn authority at this speed?

Or part two. Same aircraft. now 45 knots, 40 degrees of bank. My turn diameter is now 430 (about the same as previously--huh)) but now I'm at the real new min sink value and it's a little less sink than previously. Seems better there now--less sink, same circle, more room over stall speed (now 41 knots) so It doesn't seem being behind the speed curve makes any sense.

But let's turn tighter because 45 degrees is always best right?? So I feel a surge in the thermal, at 45 knots so I roll to 45 degrees of bank and my circle shrinks to 360 feet diameter. But my stall speed is now 43 knots, and my sink has increased again... I'm almost out of turn/tail authority, so if I do not increase speed, I'll actually lose the ability to maintain 45 degrees and slow/stop turning (not really stall...). So I speed up for safety margin, and a better min sink rate to keep my 45 degree bank and I speed up to 50 knots. Now my turn is diameter is 445 feet... worst diameter yet. Maybe I only speed up to 48 knots--five over stall and still leaving some tail/turn authority, my diameter becomes 410 feet, not much different than what I had all the way through this discussion, but at a higher sink rate for the aircraft--does 20 foot diameter offset the increased sink rate at 45 degrees of bank?? Not that I've seen on the east coast.

But I'm East coast. And based on a lot of different calculations, including making the same ones that the SSA magazine went over a few months back, My best turn is 45 knots at 40 degrees of bank, and in a surge of lift, I tighten to 45 degrees of bank for a bit until I have to shallow the bank back to 40. Not much margin, but at 45 degrees of bank, if I slow that 1 knot I do not stall and fall out of the sky, the plane stops turning and I have to shallow out, or if I don't understand and unconsciously pull to keep the turn going, I watch the yaw sting point up as the nose slices.... at which point I bury the stick in my lap (I'm heavy) to keep the turn going as the speed rises and I regain flying properly...

I do wonder given a thermal strength which a computer could figure, knowing my polar, can it tell me, as Kirk suggests, what speed/bank I should be at to minimize sink and turn radius for the observed thermal performance?