Dolphin flying

[Jonathan St. Cloud]

Was reading an article by Mike Borgelt that when flying through a thermal you will not circle in you should just fly the STF.

I have always slowed in such thermals, sometimes slowing to thermal speed while putting the thermal flaps. I do try to accelerate before I leave the lift. My thought being try to stay in the lift as long as possible while still moving forward, sometimes even s-turning to stay in large thermal but still moving down the course line.

Would appreciate any comments, critique, thoughts...

[Alex[_6_]]

The idea of speed to fly indicators is to show you the speed to fly. That counts in sinking air as much as it does in rising air - the theory remains valid also for rising air. By principle it does not make sense to fly slower than you stf indicator tells you. The only exception is of course if the lift is higher than you MC-setting in which case you must thermal. In situations where the STF indicator tells you to thermal it can be an option to slow down in straight flight flight or s-turning instead of flying circles. I sometimes do this if I don't want to thermal even if it makes sense theoretically - for example if I am close to cloud base or under a cloud street where I can get to cloud base without circles.

On my first flights with a fully ballasted ASG29 it took some getting used to that best glide is at almost 130km/h and it makes not sense to slow down to 95km/h whenever there is a bit of lift.

[Jonathan St. Cloud]

I have actually never met anyone that put McCready value of over 3.5 on their computer. Many summer days in the west, you will have your choice of 5 to 17 knot thermals, never taking anything less than 7 knots. The pilots I have compared notes with even while flying in these conditions rarely if ever put in a McCready of over 3 perhaps 3.5.

So I am asking in practical terms. Yes, i now about McCready theory, but do not know anyone that follows it moe than a very rough guideline. So back to the original question...


On Friday, February 12, 2016 at 1:56:00 PM UTC-8, Alex wrote:
> The idea of speed to fly indicators is to show you the speed to fly. That counts in sinking air as much as it does in rising air - the theory remains valid also for rising air. By principle it does not make sense to fly slower than you stf indicator tells you. The only exception is of course if the lift is higher than you MC-setting in which case you must thermal. In situations where the STF indicator tells you to thermal it can be an option to slow down in straight flight flight or s-turning instead of flying circles.. I sometimes do this if I don't want to thermal even if it makes sense theoretically - for example if I am close to cloud base or under a cloud street where I can get to cloud base without circles.
>
> On my first flights with a fully ballasted ASG29 it took some getting used to that best glide is at almost 130km/h and it makes not sense to slow down to 95km/h whenever there is a bit of lift.

[[email protected]]

A world's class pilot has been running seminars at my club. He recommends hardly ever slowing to less than 60 knots, even flying through a good thermal, and says that at the top level pilots do not dolphin very strongly. Slowing adds drag, and runs the risk that you will still be slow when you exit the lift.

[Tim Taylor]

Johnathan,

Two things:

I always set MC to true average climb rate that I am willing to stop in. This is the average for the whole thermal, not just a few seconds.

My best calculation of speed to fly in lift if you do not need to climb is the MC speed for your current MC setting minus the lift strength. So if you are flying a MC of 5 and the thermal is 2 knots slow to the speed for a MC of 3.

Tim

[Steve Koerner]

On Friday, February 12, 2016 at 6:55:40 PM UTC-7, Tim Taylor wrote:
> Johnathan,
>
> Two things:
>
> I always set MC to true average climb rate that I am willing to stop in. This is the average for the whole thermal, not just a few seconds.
>
> My best calculation of speed to fly in lift if you do not need to climb is the MC speed for your current MC setting minus the lift strength. So if you are flying a MC of 5 and the thermal is 2 knots slow to the speed for a MC of 3.
>
> Tim

I really like Tim's second paragraph suggestion.

Both paragraphs, though, have a caveat that is left out. That is, when the ground is threatening to interrupt your plans, then the correct action is to dial down the MC setting. Most of the time when I am flying, I do feel that certain threat from the ground and the dial is set lower than optimal to accommodate that threat. The closer I get to the ground, the more the dial is turned back from the free soaring optimum setting. I'm pretty sure that Tim does the same thing.

For myself, when conditions dictate a 5 knot expectation, my setting will likely average around 3 or 3.5. That may sound way conservative, but the problem is that over the period of a 7 day contest (or just any long cross country flight) there will be lots of opportunity for gravity and the ground to conspire against you. That forces an altitude conserving bias. You never want to let the ground win. Flying a bit slower than optimal doesn't hurt overall performance very much (you're operating near the plateau of a curve). Landing out hurts performance a lot.

Tim's MC setting becomes absolutely correct on final glide when the ground no longer threatens. That's why the final glide thermal is such an important one in a contest. At that point you always get to buzz home at an optimum MC speed.

A key skill in efficient soaring is to know when to dial back and by how much. It's hard to quantify and tends to take years to learn. You may be dialing back because the expectation for the next thermal has declined or because you want to be sure not to drive your glider into the ground or some combination of the two.

[Steve Koerner]

On Friday, February 12, 2016 at 9:14:46 PM UTC-7, Steve Koerner wrote:
> On Friday, February 12, 2016 at 6:55:40 PM UTC-7, Tim Taylor wrote:
> > Johnathan,
> >
> > Two things:
> >
> > I always set MC to true average climb rate that I am willing to stop in.. This is the average for the whole thermal, not just a few seconds.
> >
> > My best calculation of speed to fly in lift if you do not need to climb is the MC speed for your current MC setting minus the lift strength. So if you are flying a MC of 5 and the thermal is 2 knots slow to the speed for a MC of 3.
> >
> > Tim
>
> I really like Tim's second paragraph suggestion.
>
> Both paragraphs, though, have a caveat that is left out. That is, when the ground is threatening to interrupt your plans, then the correct action is to dial down the MC setting. Most of the time when I am flying, I do feel that certain threat from the ground and the dial is set lower than optimal to accommodate that threat. The closer I get to the ground, the more the dial is turned back from the free soaring optimum setting. I'm pretty sure that Tim does the same thing.
>
> For myself, when conditions dictate a 5 knot expectation, my setting will likely average around 3 or 3.5. That may sound way conservative, but the problem is that over the period of a 7 day contest (or just any long cross country flight) there will be lots of opportunity for gravity and the ground to conspire against you. That forces an altitude conserving bias. You never want to let the ground win. Flying a bit slower than optimal doesn't hurt overall performance very much (you're operating near the plateau of a curve). Landing out hurts performance a lot.
>
> Tim's MC setting becomes absolutely correct on final glide when the ground no longer threatens. That's why the final glide thermal is such an important one in a contest. At that point you always get to buzz home at an optimum MC speed.
>
> A key skill in efficient soaring is to know when to dial back and by how much. It's hard to quantify and tends to take years to learn. You may be dialing back because the expectation for the next thermal has declined or because you want to be sure not to drive your glider into the ground or some combination of the two.

Besides the ground threat, there is actually more good reason to cruise somewhat slower than true MC. Flying slower allows you to do a better job of finding, sorting and tracking in good air. Flying slower also gives you a better chance of doing an accurate pull up into the next thermal. So biasing to a lower setting has those secondary benefits.

Yet another reason that a lower setting is preferred is that all thermals are not equal. You get a better overall performance when you can select for the best thermals. Cruising slower at a lower than optimal setting, presents more thermal opportunities with every glide. That means you can be more choosey and end up with a better average climb rate over the flight.

MacReady theory should best be thought of as an upper bound. Practical considerations dictate a lower setting.

[Dave Nadler]

On Friday, February 12, 2016 at 2:46:48 PM UTC-5, Jonathan St. Cloud wrote:
> Was reading an article by Mike Borgelt that when flying through a
> thermal you will not circle in you should just fly the STF.
> Would appreciate any comments, critique, thoughts...

Only if flying according to MacCready theory.
When does MacCready theory not apply?
Discuss amongst yourselves...

Hint:
http://www.onlinecontest.org/olc-2.0/gliding/flightinfo.html?flightId=185517315

See ya, Dave

[[email protected]]

On Friday, February 12, 2016 at 2:46:48 PM UTC-5, Jonathan St. Cloud wrote:
> Was reading an article by Mike Borgelt that when flying through a thermal you will not circle in you should just fly the STF.
>
> I have always slowed in such thermals, sometimes slowing to thermal speed while putting the thermal flaps. I do try to accelerate before I leave the lift. My thought being try to stay in the lift as long as possible while still moving forward, sometimes even s-turning to stay in large thermal but still moving down the course line.
>
> Would appreciate any comments, critique, thoughts...

When I'm getting toward the bottom of my height band, I slow more for longer. Toward the top, the opposite.
All adjusted for how the sky looks ahead.
When the stick hand wants to turn- slap it and say "bad hand".
FWIW
UH

[Soartech]

> Hint:
> http://www.onlinecontest.org/olc-2.0/gliding/flightinfo.html?flightId=185517315
>
> See ya, Dave

Dave, What is your point here?

[Tim Taylor]

Steve is correct that we fly slower as we get lower, but that does not mean you should fly slower than your MC setting. In my first posting I stated that the MC should be set to the thermal strength you are willing to stop for. Rather than flying slower than an unrealistic MC setting, turn the MC down to what you are willing to take.

As Uncle Hank said there is no perfect answer that fits all situations, all decisions depend on many other factors including the conditions and terrain ahead.

John Cochrane's article "Just a little faster please" is a must read on the topic:
http://faculty.chicagobooth.edu/john.Cochrane/soaring/index.htm

[SoaringXCellence]

if you download the trace, you can see a remarkably long 100 mile run northward, below 4000 feet, with a -601 L/D for the last 76 miles

MB

[Bob Pasker]

when I flew this past summer on a 4-hour and an 8-hour flight with a Very Experience Pilot (who shall remain nameless should I misstate), his technique on long legs (we had some 30 minute straight-ahead legs!) was to slow down in rising air, and initiate a turn. Once the plane caught up with the control inputs, he would decide to march on ahead if the lift was weak, s-turn (to keep the plane pointed generally in the right direction) when the lift was medium, and thermal when it was strong. YMMV. he very rarely thermalled, unless we really needed the altitude. --bob

On Friday, February 12, 2016 at 2:46:48 PM UTC-5, Jonathan St. Cloud wrote:
> Was reading an article by Mike Borgelt that when flying through a thermal you will not circle in you should just fly the STF.
>
> I have always slowed in such thermals, sometimes slowing to thermal speed while putting the thermal flaps. I do try to accelerate before I leave the lift. My thought being try to stay in the lift as long as possible while still moving forward, sometimes even s-turning to stay in large thermal but still moving down the course line.
>
> Would appreciate any comments, critique, thoughts...

[MNLou]

Gentlemen -

One thing to remember - there is contest flying and there is non-contest flying.

While I understand that the theory is exactly the same, I would expect very different tactics between a Nationals contest flight and an OLC flight.

Especially for an OLC flight where time or speed is not a critical component, I would expect a more conservative strategy would be found to be the norm.

Lou

[[email protected]]

On Saturday, February 13, 2016 at 2:18:18 PM UTC-5, MNLou wrote:
> Gentlemen -
>
> One thing to remember - there is contest flying and there is non-contest flying.
>
> While I understand that the theory is exactly the same, I would expect very different tactics between a Nationals contest flight and an OLC flight.
>
> Especially for an OLC flight where time or speed is not a critical component, I would expect a more conservative strategy would be found to be the norm.
>
> Lou

I fly almost exactly the same whether practicing or racing. It doesn't pay to change my style.
For the best OLC flight you are still trying for the best speed given the time you fly so as to maximize points.
UH

[Charlie M. (UH & 002 owner/pilot)]

On Saturday, February 13, 2016 at 2:18:18 PM UTC-5, MNLou wrote:
> Gentlemen -
>
> One thing to remember - there is contest flying and there is non-contest flying.
>
> While I understand that the theory is exactly the same, I would expect very different tactics between a Nationals contest flight and an OLC flight.
>
> Especially for an OLC flight where time or speed is not a critical component, I would expect a more conservative strategy would be found to be the norm.
>
> Lou

To sorta echo "UH's" comment...... the ONLY time I was allowed to, "Do something stupid that may break the glider..." was:
-Last day of a US Nats or worlds
followed by
-If it works, you win......."

Period.

Otherwise, "Train as you race, race as you train".

I agree that the US frowns upon "team flying" in it's contest, frankly (in disagreement to some on RAS), I think this is a TON more against the US doing well in the "world stage" than what type of tasks we tend to fly here (in the US).
A good team can have a high level of finish IF they help each other.
In the discussion of "leeching", depends on whether you are worried about US rankings or world rankings.

OK Sean F., have at it.

[back to stoking my fire, it's a "wee bit chilly" in north NJ. USA]

[Dave Nadler]

On Saturday, February 13, 2016 at 2:18:18 PM UTC-5, MNLou wrote:
> Especially for an OLC flight where time or speed is not a critical component,
> I would expect a more conservative strategy would be found to be the norm.

Absolutely wrong. OLC is a race, just like contests.
XC, you are always flying against the clock, the end-of-day, as fast as possible.
Otherwise you don't get home before sunset, end-of-lift, etc.
Time and speed is *always* critical.
IIRC explained in Reichmann ;-)

[Dave Nadler]

On Saturday, February 13, 2016 at 10:34:32 AM UTC-5, Soartech wrote:
> > Hint:
> > http://www.onlinecontest.org/olc-2.0/gliding/flightinfo.html?flightId=185517315
> >
> > See ya, Dave
>
> Dave, What is your point here?

MacCready theory is not always applicable.
Consider:
- What are MacCready theory's assumptions, and when are these not valid?
- Why do good flights often beat expected MC speeds (after accounting
for start-finish altitude differential)?

Hopefully this will be covered in the V3 talk at the convention;
Tilo tells me by analyzing OLC piles of flight logs, the actual
behavior of top pilots shows this, thus better informs how the glider
should be optimized...

Hope this helps,
Best Regards, Dave

[[email protected]]

Jonathan,

Your approach is a good one and there is not an entirely clear answer. I think it really depends on the glider you're flying and your given situation. There are a couple things at play.

1) Time in lift/sink
2) Dynamic Soaring effect (from the pull-up)
3) Tactical considerations

So for the simple speed-to-fly indicator, it is telling you the optimal mathematical speed to maximize time in rising air. It does NOT assume the drag from a rapid pull-up. It is near to impossible to chase the needle and to do so would be inefficient in its own right. However, maximizing time in lift relative to sink is certainly a good thing and it makes sense to slow down in the good air or thermal. The question is how much. If you are in a relatively big area of lift and you can gradually pull up (1.5-2g max), then following the STF could make sense.)

Now, in some gliders you can pop off the air (dynamic soaring). This particularly works well with light wing-loaded gliders and/or gliders that have low induced drag and airfoils that are not prone to separation. In these gliders, dolphin flying carries a different meaning as you are extracting energy by the very act of pulling against the gust or thermal. The STF is irrelevant in these cases.

Some examples of gliders I had flown-

1) Schweizer 1-26E-

Great dolphining machine! The stiff wings and the very light wing loading let you pop off the gusts really well. The strategy for dolphining, especially into the wind is to slow down to minimum sink, sometimes even to minimum controllable airspeed and milk out the air as much as possible. The goal is to avoid turning at all costs. There is a huge amount of energy gained from dolphining/dynamic soaring off the vertical gusts. On a convective day in the East, it is possible to consistently achieve 25-1 glides by doing this.

2) LS-4

Mediocre dolphining glider. No flaps, so lots of drag on pulls. Much better to smoothly slow down to best glide, possibly to minimum sink if the thermal is quite big.

3) Standard Cirrus-

Awful dolphining machine. Huge airflow separation when changing angle of attack. But really great performance in club class just flying straight and smooth!

4) Duckhawk-

Unbelievably awesome dolphining sailplane. Auto-flaps, so perfect AoA on pull-ups, low induced drag, low separation make it conserve most of the energy on big deviations. Makes a lot of sense to pull hard and often.

(Listen to Bill Thar's speech at convention about Auto-flaps to learn more)

The tactical consideration is relevant in that there are two types of dolphin-flying. There is dolphining to get more altitude, and for greater speed, both which have a different technique. When dolphining for more altitude, I will cruise slower, pull more aggressively and slow down to minimum sink. When dolphining for "speed", I do gentle vertical deviations, less draggy, but to spend a bit more time in the lift compared to sink.

In practice, here are two scenarios-

1) You are going upwind and you have found a thermal street. You are climbing, drifting downwind. The question is when do you leave? You can leave earlier, slowly float up in the street by wafting up, or you can leave later and then blast along cloudbase. Generally I find it more efficient to leave earlier and waft up.

2) You are on final glide low. You need to make up 1000ft. Then dolphin more aggressively and pull out every bit of altitude. Once final glide is made, then speed up and don't deviate vertically as substantially.

Hope these thoughts were of interest.

Best Regards,
Daniel

[MNLou]

Hank, Charlie, and Dave -

I should have made myself more clear -

For you "contest monsters" who focus on, fly, and win at the National level, of course you are always racing - even when you are practicing. That's what it takes to get fast. If you fly OLC, you max it out.

My contrast to a contest pilot was a pilot who flies XC but isn't trying to max out speed - just get around the course. Think a 200km triangle on a mid-summer day. Doesn't care too much about speed or how may OLC he/she gets. Just wants to have fun, go someplace, and get home.

I believe that pilot would fly more conservatively to maximize altitude and minimize the risk of landing out. A faster speed that eats up more altitude gains them nothing and potentially costs them big time.

Lou

[Charlie M. (UH & 002 owner/pilot)]

On Saturday, February 13, 2016 at 10:54:32 PM UTC-5, MNLou wrote:
> Hank, Charlie, and Dave -
>
> I should have made myself more clear -
>
> For you "contest monsters" who focus on, fly, and win at the National level, of course you are always racing - even when you are practicing. That's what it takes to get fast. If you fly OLC, you max it out.
>
> My contrast to a contest pilot was a pilot who flies XC but isn't trying to max out speed - just get around the course. Think a 200km triangle on a mid-summer day. Doesn't care too much about speed or how may OLC he/she gets. Just wants to have fun, go someplace, and get home.
>
> I believe that pilot would fly more conservatively to maximize altitude and minimize the risk of landing out. A faster speed that eats up more altitude gains them nothing and potentially costs them big time.
>
> Lou

I do that sort of flying a lot (laid back, just wafting around the area), then again, I also do longer XC's from our place. We don't always get great weather, but if you want to cover some miles, you can't really just waft along, you need to keep the pace up.
My 500K took almost 7 hours (on thermals in southern NY), when it worked, I had to keep moving, when it didn't I went slow.
Not really any different than a contest flight, just longer.

Not saying everyone needs to do long flights, or "scorch the skies" for speed, some just like to get high and take a local tour. Nothing wrong with that.

But if you want to do contests, or, longer XC flights, you have to practice it (faster/more efficient flying), you can't just decide, "Hey, I never do it, but I will today!"
Just like doing a marathon, you really can't wake up one morning, pull on sneakers and say, "Hey, lets go do a marathon today". It will be a long day and you likely won't feel too good for a week or so after.

[[email protected]]

On Saturday, February 13, 2016 at 10:54:32 PM UTC-5, MNLou wrote:
> Hank, Charlie, and Dave -
>
> I should have made myself more clear -
>
> For you "contest monsters" who focus on, fly, and win at the National level, of course you are always racing - even when you are practicing. That's what it takes to get fast. If you fly OLC, you max it out.
>
> My contrast to a contest pilot was a pilot who flies XC but isn't trying to max out speed - just get around the course. Think a 200km triangle on a mid-summer day. Doesn't care too much about speed or how may OLC he/she gets. Just wants to have fun, go someplace, and get home.
>
> I believe that pilot would fly more conservatively to maximize altitude and minimize the risk of landing out. A faster speed that eats up more altitude gains them nothing and potentially costs them big time.
>
> Lou

I doubt that I fly much faster than you do between thermals when flying cross country. What I probably do more, and possibly better, is make modest changes in speed in response to or anticipation of air mass movement, and likely a lot more deviation to optomise my path so as to spend as little time in bad air as I can.
I don't land out all that often. The last off field landing I made from my home field was probably 20 years ago. My landings in fields in contests average about 1 every two or three years and I fly about 40 tasks a year.
The impression that contest pilots go fast by taking big risks is wrong in my experience. The percentages are in keeping risk as low as possible. That doesn't mean we're floating at cloud base, but we are being pretty careful..
UH

[Dave Nadler]

On Saturday, February 13, 2016 at 10:54:32 PM UTC-5, MNLou wrote:
> I believe that ... would fly more conservatively to maximize altitude
> and minimize the risk of landing out. A faster speed that eats up
> more altitude gains them nothing and potentially costs them big time.

You are confusing flying efficiently (fast), and flying aggressively
(which periodically puts you on the ground, not fast)....

[Dave Nadler]

On Friday, February 12, 2016 at 6:33:03 PM UTC-5, Jonathan St. Cloud wrote:
> I have actually never met anyone that put McCready value of over 3.5...

Really? You should get out more!
http://www.onlinecontest.org/olc-2.0/gliding/daily.html?st=olc-league&rt=olc&df=2011-06-18&sp=2011&c=C0&sc=

Not possible with MC of 3.5!! Over 100mph!!

[Dave Nadler]

On Saturday, February 13, 2016 at 11:18:41 AM UTC-5, SoaringXCellence wrote:
> if you download the trace, you can see a remarkably long 100 mile run
> northward, below 4000 feet, with a -601 L/D for the last 76 miles

The owner was kind enough to invite me to fly while I was waiting for my own ArcusM. I don't think many flew XC this day because of low bases and perceived weak lift. First bit of the flight I circled excessively while getting used to the glider (in which I only had a few hours). After I settled down, I had the owner turn off the very badly-behaved varios (a bad vario is far worse than no vario, but this upset the owner). Managed to string together various lift lines and avoid circling most of the flight.

We had to cut the flight short because of OD and some heavy showers, but still managed 460km and 17% circling IIRC.

The point is, under these conditions MC theory does not apply.
Consequently, neither does MC-derived STF in lift.

Hope that helps,
Best Regards, Dave

[waremark]

On Monday, 15 February 2016 01:28:14 UTC, Dave Nadler wrote:
> On Friday, February 12, 2016 at 6:33:03 PM UTC-5, Jonathan St. Cloud wrote:
> > I have actually never met anyone that put McCready value of over 3.5...
>
> Really? You should get out more!
> http://www.onlinecontest.org/olc-2.0/gliding/daily.html?st=olc-league&rt=olc&df=2011-06-18&sp=2011&c=C0&sc=
>
> Not possible with MC of 3.5!! Over 100mph!!

6 out of the top 20 on that day were flying an ASH 26E! And I seem to be selling mine.

[krasw]

On Sunday, 14 February 2016 04:57:42 UTC+2, Dave Nadler wrote:
> On Saturday, February 13, 2016 at 10:34:32 AM UTC-5, Soartech wrote:
> > > Hint:
> > > http://www.onlinecontest.org/olc-2.0/gliding/flightinfo.html?flightId=185517315
> > >
> > > See ya, Dave
> >
> > Dave, What is your point here?
>
> MacCready theory is not always applicable.
> Consider:
> - What are MacCready theory's assumptions, and when are these not valid?
> - Why do good flights often beat expected MC speeds (after accounting
> for start-finish altitude differential)?
>
> Hopefully this will be covered in the V3 talk at the convention;
> Tilo tells me by analyzing OLC piles of flight logs, the actual
> behavior of top pilots shows this, thus better informs how the glider
> should be optimized...
>
> Hope this helps,
> Best Regards, Dave

Are you saying that MC theory is not valid for gliding long distances using continuous lift?

[[email protected]]

On Monday, February 15, 2016 at 1:48:59 AM UTC-5, krasw wrote:
> On Sunday, 14 February 2016 04:57:42 UTC+2, Dave Nadler wrote:
> > On Saturday, February 13, 2016 at 10:34:32 AM UTC-5, Soartech wrote:
> > > > Hint:
> > > > http://www.onlinecontest.org/olc-2.0/gliding/flightinfo.html?flightId=185517315
> > > >
> > > > See ya, Dave
> > >
> > > Dave, What is your point here?
> >
> > MacCready theory is not always applicable.
> > Consider:
> > - What are MacCready theory's assumptions, and when are these not valid?
> > - Why do good flights often beat expected MC speeds (after accounting
> > for start-finish altitude differential)?
> >
> > Hopefully this will be covered in the V3 talk at the convention;
> > Tilo tells me by analyzing OLC piles of flight logs, the actual
> > behavior of top pilots shows this, thus better informs how the glider
> > should be optimized...
> >
> > Hope this helps,
> > Best Regards, Dave
>
> Are you saying that MC theory is not valid for gliding long distances using continuous lift?

Read Brigliadori as he describes extended glide. MC is based on a a model of climb and glide that does not apply directly much of the time, especially with higher performance gliders.
UH

[ND]

On Friday, February 12, 2016 at 2:46:48 PM UTC-5, Jonathan St. Cloud wrote:
> Was reading an article by Mike Borgelt that when flying through a thermal you will not circle in you should just fly the STF.
>
> I have always slowed in such thermals, sometimes slowing to thermal speed while putting the thermal flaps. I do try to accelerate before I leave the lift. My thought being try to stay in the lift as long as possible while still moving forward, sometimes even s-turning to stay in large thermal but still moving down the course line.
>
> Would appreciate any comments, critique, thoughts...

i was always told by a very talented and well ranked pilot to never slow down below 60kts unless you are going to circle. i try to live by that, and have actually found that while one pilot pulls to thermalling speed, and i gently ease back to 60, he gets maybe 50 feet on me after he pushes back over, but i put distance on him. and i've always found that it's harder to make up horizontal distance vs. 50 or 100 vertical feet on someone (this is east coast dudes). remember that a pull is draggy, and also when you pull up and push back over, that's a "curve" in your flight path. when you only gently slow down to 60, you are flying a short path through the sky. when thinking in the "shortest distance between two points" mentality, remember to think in 3 dimensions. that's is my technique. its simple and effective i think.

[Bruce Hoult]

On Monday, February 15, 2016 at 4:45:15 PM UTC+3, wrote:
> On Monday, February 15, 2016 at 1:48:59 AM UTC-5, krasw wrote:
> > On Sunday, 14 February 2016 04:57:42 UTC+2, Dave Nadler wrote:
> > > On Saturday, February 13, 2016 at 10:34:32 AM UTC-5, Soartech wrote:
> > > > > Hint:
> > > > > http://www.onlinecontest.org/olc-2.0/gliding/flightinfo.html?flightId=185517315
> > > > >
> > > > > See ya, Dave
> > > >
> > > > Dave, What is your point here?
> > >
> > > MacCready theory is not always applicable.
> > > Consider:
> > > - What are MacCready theory's assumptions, and when are these not valid?
> > > - Why do good flights often beat expected MC speeds (after accounting
> > > for start-finish altitude differential)?
> > >
> > > Hopefully this will be covered in the V3 talk at the convention;
> > > Tilo tells me by analyzing OLC piles of flight logs, the actual
> > > behavior of top pilots shows this, thus better informs how the glider
> > > should be optimized...
> > >
> > > Hope this helps,
> > > Best Regards, Dave
> >
> > Are you saying that MC theory is not valid for gliding long distances using continuous lift?
>
> Read Brigliadori as he describes extended glide. MC is based on a a model of climb and glide that does not apply directly much of the time, especially with higher performance gliders.

It was initially derived that way, but I believe it *applies* to other situations too.

If you are running along under a cloud street, the slow thing is to fly just under the clouds speeding up in the lift so you don't get sucked into them, and slowing down when that danger is past. The fast thing is to increase your MC setting (and fly it) enough that you fly fast and drop below cloudbase sufficiently in weaker lift that you can slow down and pull up in lift without entering the clouds.

For high performance gliders the main modification to MC theory is that the conventional output is "speed to fly". The real output should be "angle of attack to fly".

At speeds around 40 - 60 knots they are quite quickly the same thing. But over 100 knots it means that you are simply pulling increased Gs in lift and decreased Gs in sink and you might well pass through the area of lift of sink with very little change in airspeed.

Intuitively, you're "bouncing off" the lift. And sink can't rob energy from you while you're in a low drag near zero lift configuration.

[krasw]

maanantai 15. helmikuuta 2016 15.45.15 UTC+2 kirjoitti:
>
> Read Brigliadori as he describes extended glide. MC is based on a a model of climb and glide that does not apply directly much of the time, especially with higher performance gliders.
> UH

I have and have read Brigliadori. It's still challenge to prove MC theory invalid, it has been attempted many times. MC theory applies under cloudstreet, there is optimum speed for current lift or sink.

BTW Brigliadori has nonsense in some parts of the book. I would take everything with at least a grain of salt.

[Mike the Strike]

MacCready theory is perfectly valid for both thermal soaring and cloud-street dolphin flying as long as the assumptions under which the theory is valid hold. Since this is almost never, flying at an appropriate MacCready setting may not be optimum under any conditions!

Out west, you run the risk of flying into the ground when thermals are widely spaced and perhaps short-lived - hence the recommendation to slow as you get lower.

Under a solid cloud street, MacCready can give you good guidance overall, but goes out of the window if you have to fly fast in lift to stay out of cloud!

Mike

[Per Carlin]

McR theory are correct in almost all conditions, could be that on the ridge with dynamic lift should other theories be used.

But with that said di I also have to say:
The master of McR theory will never outperform the master of finding good climbs and the master of finding the best route.
I spend very little time and energy in decisions on STF, I try to spend most of my time and energy to find the best route and to get the best climbs. And most important of all, avoid the bad climbs.

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On Tuesday, February 16, 2016 at 8:46:08 AM UTC-5, Per Carlin wrote:
> McR theory are correct in almost all conditions, could be that on the ridge with dynamic lift should other theories be used.
>
> But with that said di I also have to say:
> The master of McR theory will never outperform the master of finding good climbs and the master of finding the best route.
> I spend very little time and energy in decisions on STF, I try to spend most of my time and energy to find the best route and to get the best climbs. And most important of all, avoid the bad climbs.

Yep- right and left is much more important than up and down.
UH

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On Saturday, February 13, 2016 at 6:46:48 AM UTC+11, Jonathan St. Cloud wrote:
> Was reading an article by Mike Borgelt that when flying through a thermal you will not circle in you should just fly the STF.
>
> I have always slowed in such thermals, sometimes slowing to thermal speed while putting the thermal flaps. I do try to accelerate before I leave the lift. My thought being try to stay in the lift as long as possible while still moving forward, sometimes even s-turning to stay in large thermal but still moving down the course line.
>
> Would appreciate any comments, critique, thoughts...

The simple answer is to suck it and see, as it depends :)
When encountering lift, note the altimeter reading, then try any of the following: slowing down a little, a gentle pullup, a vigorous pullup and S-turn.

[Paul Villinski]

Could any of you shed some light on use of flaps while dolphin flying? I.e., in my DG-400, cruising at 70 - 75 knots with -4 degrees flaps, if I fly under a cloud and want to maximize the climb without thermalling, what is the best approach in terms of shifting gears with the flaps? I assume this is dependent on many different factors, but is there a general consensus about whether or not to down-shift to 0 degrees or positive (thermalling settings) flaps when flying straight?

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On Sunday, February 28, 2016 at 7:54:18 AM UTC-7, Paul Villinski wrote:
> Could any of you shed some light on use of flaps while dolphin flying? I.e., in my DG-400, cruising at 70 - 75 knots with -4 degrees flaps, if I fly under a cloud and want to maximize the climb without thermalling, what is the best approach in terms of shifting gears with the flaps? I assume this is dependent on many different factors, but is there a general consensus about whether or not to down-shift to 0 degrees or positive (thermalling settings) flaps when flying straight?

My answer to this flap question will not agree with the intuition of some flyers -- here is the truth on the matter according to GW:

Flap optimization is not about airspeed; it is about angle of attack. If you are going to slow down, the time to lower the flaps is when you make that decision and start pulling the stick back increasing AOA. Conversely, when you speed up, best to raise the flaps as you begin to push.

However, there is an important caveat to this. Most gliders have a structural speed limit for positive flaps. Despite what may be performance optimal, one must never overspeed the flaps.

Should someone express a counter opinion (likely), please do not misinterpret a lack of further reply on my part.

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Years ago I talked to Wil Schuemann about the system he installed in his modified ASW 12. The stick had a detent for the center position and he used it primarily for aileron control. Pitch control was almost exclusively using the flap lever except for takeoff, tow, landing, etc.

I didn't install a detent in my LS-3 but because my glider had no detents in the flap drive as it came from the factory, I started using the flaps somewhat as Wil did. As he had assured me, it was a wonderfully smooth way to fly. Pull ups were slower than I wanted in those days of dramatic zoomies so I would "help" the process along with a quick pull on the stick as I entered a thermal at cruising speed. But at the top, instead of pushing over, I'd use the flap lever to bring the nose down smoothly, than bank and snap the flaps down for thermaling. I used the stick normally to thermal because the airplane reacted faster although I wonder now if I could have benefited there, too. When I was ready to exit, I'd use the flaps to lower the nose and accelerate.

The caveat was that this worked best if the glider was set up so the stick was in the same position for slow and higher speed flight. At Wil's advice, I measured the distance between the instrument panel and the top of the stick in straight flight at min sink and again at cruising speed (defined as the lowest speed for which I would use full negative flaps) and found that with my aft CG position, it was spot on.

I'm not saying this is the best way to fly. But it might be worth experimenting with. One caution as a layman: be careful about getting too slow with the flaps in negative position. The fuselage will be rather nose high and if you were to lower the flaps quickly, the angle of attack would increase just as quickly. If you stall in that position, the wing wake could be higher than the tail, which is a nasty prescription for "deep stall." I know a pilot who apparently did just this, entered what sounded like deep stall (stable, uncontrollable, nose-high, very high rate of descent, with no ability to lower the nose) and was lucky to escape about the time he was thinking about bailing out.

Chip Bearden

[[email protected]]

Can anyone point me towards literature on this subject?
I wonder if anyone has done simulations, calculating the cost of those 6.5G pulls for example.

[[email protected]]

On Tuesday, March 1, 2016 at 3:07:03 PM UTC-5, wrote:
> Can anyone point me towards literature on this subject?
> I wonder if anyone has done simulations, calculating the cost of those 6.5G pulls for example.

Wil Schuemann wrote an article for Soaring Symposium back in the late 60s called "The Price You Pay for Flying McCready Speeds". He did a monumental amount of calculations comparing dophin technique pulling and pushing to match the STF according to McCready vs flying simply at two selected airspeeds. Over a cross country flight, choosing to fly at the two selected speeds equated to a much better flight in terms of speed achieved. I once had a discussion with a world class pilot who stated that the drag incurred by pulling and pushing the stick is much greater than most people appreciate. Read the literature in the Soaring Symposium on Competitive Flying authored by Wil Schuemann. Indirectly, that may also validate the use of flaps as being more efficient than using the stick (elevator).

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On Tuesday, March 1, 2016 at 5:50:58 PM UTC-5, wrote:
> On Tuesday, March 1, 2016 at 3:07:03 PM UTC-5, wrote:
> > Can anyone point me towards literature on this subject?
> > I wonder if anyone has done simulations, calculating the cost of those 6.5G pulls for example.
>
> Wil Schuemann wrote an article for Soaring Symposium back in the late 60s called "The Price You Pay for Flying McCready Speeds". He did a monumental amount of calculations comparing dophin technique pulling and pushing to match the STF according to McCready vs flying simply at two selected airspeeds. Over a cross country flight, choosing to fly at the two selected speeds equated to a much better flight in terms of speed achieved. I once had a discussion with a world class pilot who stated that the drag incurred by pulling and pushing the stick is much greater than most people appreciate. Read the literature in the Soaring Symposium on Competitive Flying authored by Wil Schuemann. Indirectly, that may also validate the use of flaps as being more efficient than using the stick (elevator).

The Price You Pay for McCready Speeds: http://www.betsybyars.com/guy/soaring_symposia/72price.html

[[email protected]]

Very interesting read, thanks for sharing and linking!

[Paul Villinski]

The Schuemann article is very interesting, indeed -- thanks for posting it!

[Andy Blackburn[_3_]]

On Tuesday, March 1, 2016 at 3:04:06 PM UTC-8, wrote:
>
> The Price You Pay for McCready Speeds: http://www.betsybyars.com/guy/soaring_symposia/72price.html

Oldie but goodie. Speeds tend to be a bit higher now with modern gliders having a knee in the polar that is at a bit higher speed, plus more water capacity.

There's nothing wrong with McCready theory - in theory. The considerations beyond McCready for pilots are, first, as Wil pointed out, the achieved cross-country speed penalty for cruising a bit off McCready optimal STF is not that great and options open up when you fly a bit slower in terms of search radius, ability to sense lift, less G-induced losses in getting slowed down within the diameter the thermals you encounter so you don't miss good lift, etc. There's zero benefit to flying faster than McCready so the bias ought to be slower on average to open up that option value.

Second, McCready applies in a theoretical world of consistency and certainty in terms of lift ahead versus lift behind you as well as search altitude versus inter-thermal distance, lift strength distribution, wind speed and direction versus task leg orientation (which themselves can vary with AATs). Soaring weather is stochastic and the expected probabilities ought to affect how we fly - especially as circumstances like altitude, time of day, the look of conditions ahead all affect that probability distribution.

The fundamental tradeoff in flying fast is the probability of getting stuck or landing out versus the probability of finding a good (or better) thermal ahead before that happens. Again, read the Cochrane article on flying faster that nicely covers many of these topics. There is also the issue of searching for lift (or more importantly the best lift) in areas where you have indications that there ought to be a good thermal, and how much altitude there is to gain if you strike gold with a boomer. No point in searching around close to cloudbase.

Based on the above, there a places and times when I'll S-turn (or even fly a clover-leaf) to find the good lift I expect might be there somewhere, particularly in cases where there's a marker like a cloud, a terrain feature or when I'm coming to the end of a street where prospects ahead are less certain. If lift is widely distributed and variable I more frequently attempt to expand the area searched under a cloud to see what's available. On occasions where I'm flying with another glider I typically find I pay a fraction of a mile for the option to search in an S-turn versus steam ahead - that's when it doesn't pay off. When it does pay off I'll often find that I arrive at the next thermal later but hundreds to more than a thousand feet above the pilot I'm flying with (depending on what he finds up ahead).

That's the great thing about soaring - it pays to think - most of the time.

9B

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On Friday, March 11, 2016 at 11:13:56 AM UTC-5, Andy Blackburn wrote:
< Based on the above, there a places and times when I'll S-turn (or even fly a clover-leaf) to find the good lift I expect might be there somewhere, particularly in cases where there's a marker like a cloud, a terrain feature or when I'm coming to the end of a street where prospects ahead are less certain. >

I agree, 9B. I recall a day back in the 70s (the 1970s, just in case there's any question from the younger crowd) down at the old Cordele regionals in August. Yes, it was hot, humid, gnat infested, and plagued with T-storms almost every day. But we flew almost every day.

I'd lost time starting early until, like clockwork, the day broke open and I finished in mid afternoon not long after it really got good. I managed to launch again, then had trouble working up for a start. The clouds still looked good but the day had clearly peaked and the better thermals were harder to find. Rather than plunging ahead, rejecting every soft thermal under a promising cloud and running for the next established cloud a bit farther out than before, I slowed up as I came under the cloud and did S turns and search patterns until I found the [inevitable] strong core. It seemed like a more cautious, possibly even slower way to fly than the exuberant way I'd come home an hour earlier. But I felt like I couldn't afford to drive low late in the day waiting for the good thermal. On the final leg, I was a lot more patient waiting for the "get home" thermal I needed and cruised in to find I had won the day with, IIRC, a 10-15 mph faster speed than my first trip. Hmmmm.

I've never forgotten that lesson. True, it's not always applicable. Often I slow too soon or do a little search and fall behind another pilot who is more resolute on driving straight ahead. But when it's uncertain, it can really pay off to exercise a degree of caution. It costs a lot less time to search a bit for a good thermal near the bottom of my desired working band than it costs searching for and thrash around in a survival thermal down low.

Chip Bearden

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Chip its interesting that as a lowely 1-26 driver, I have found that the Go-a-little-slower, S turn to find the better lift, and stay in the better part of the thermal band, has become standard operating procedure for me in trying the stretch out some longer and actualy faster xc flights. The schuman principle appears to apply even to the lower performance end of the spectrum.
Dan 1-26 #225