Dolphin flying

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 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.

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.

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.

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

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.

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.

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...htId=185517315

See ya, Dave

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

Hint:
http://www.onlinecontest.org/olc-2.0...htId=185517315

See ya, Dave

Dave, What is your point here?