Word of advice on making use of thermals?

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TimKuijpers
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Re: Word of advice on making use of thermals?

Postby TimKuijpers » Tue Oct 26, 2010 2:46 pm

MrTumnus wrote:
OXO wrote:What I really disagree with is decreasing the bank when flying out of the best lift. This will just move your circle out of the lift.


If you fly in reality, try it next time you fly. It does work.

I don't agree, decreasing the bank when flying out of the best lift. you will never see me decrease bank when flying out of the stronger lift.
I think that what you are trying to do is combine the two methods. so when decreasing bank you are flying towards the core.
But the way you describe it, it won't work. Try to paint yourself a picture of a thermal, and draw a line that you fly, you will never hit the core again.

Why I use both methods is that with the most common method " widen out when encountering the strongest lift" you need to know when you are gonna encounter the strongest lift. And so far nobody can tell where that is, because if so we wouldn't need to discuss the centering. What we / I do is: fly a complete circle, and based on the climbrates during the circle we know where to fly to. So in fact, when I am in the strongest lift, 270 degrees later I will fly straight.

The nice thing of the "tighten-on-the-surge" theory is that you can act on what is happening, and not on what 'has been'. But you can only apply this once in a thermal, after that you need to apply or combine both methods.
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OXO
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Re: Word of advice on making use of thermals?

Postby OXO » Tue Oct 26, 2010 3:05 pm

Advice from a better pilot than most of us...
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Strider69
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Re: Word of advice on making use of thermals?

Postby Strider69 » Tue Oct 26, 2010 4:28 pm

That technique on the penultimate page is exactly what i do. Cool :D :D
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Re: Word of advice on making use of thermals?

Postby OXO » Tue Oct 26, 2010 4:34 pm

My goal is to centre the thermal perfectly on the second circle. The first circle is for finding the core.

I also don't bother to recentre if the variation round the circle is less than 25%. It's better to spend that time on lookout and deciding what to do next.
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Re: Word of advice on making use of thermals?

Postby Freebird » Tue Oct 26, 2010 6:35 pm

OXO wrote:What I really disagree with is decreasing the bank when flying out of the best lift. This will just move your circle out of the lift.

Its the bit that I think is completely wrong, I actually tried it with Condor a couple of days ago & you move your turn more into the sink. I think we need some simple diagrams to show how it is meant to work, I'm not sure its being properly explained.

From Johnsons pdf...
A similar technique is to tighten one’s turn when in the best lift, and to reduce the bank when on a heading to bring the sailplane deeper into the strongest part of the thermal.
Are we talking of something similar to this?

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Re: Word of advice on making use of thermals?

Postby MrTumnus » Wed Oct 27, 2010 6:35 pm

Freebird wrote:
OXO wrote:What I really disagree with is decreasing the bank when flying out of the best lift. This will just move your circle out of the lift.

Its the bit that I think is completely wrong, I actually tried it with Condor a couple of days ago & you move your turn more into the sink. I think we need some simple diagrams to show how it is meant to work, I'm not sure its being properly explained.

From Johnsons pdf...
A similar technique is to tighten one’s turn when in the best lift, and to reduce the bank when on a heading to bring the sailplane deeper into the strongest part of the thermal.
Are we talking of something similar to this?


Kind of Freebird. What you want to be doing is tightening the turn on the strongest lift and at the same time build a mental picture of the thermal and use that in conjunction with the tightening to center on the core.

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Strider69
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Re: Word of advice on making use of thermals?

Postby Strider69 » Fri Oct 29, 2010 1:38 pm

Basically i think you should involve Olympia in this discussion, He's been flying for a lot longer that he cares to remember and has a wealth of knowledge throughout the whole spectrum of gliding. :wink:
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Andrzej Czop
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Re: Word of advice on making use of thermals?

Postby Andrzej Czop » Sun Dec 05, 2010 2:18 pm

Many years ago (20?) I made device whose idea of logic is below at picture.
This worked well and even better than today's GPS devices :lol: 8) , because we knew which direction we should started circulate before entering to the lift. There was one problem - sensor temperature compensation. If the temperature dropped ~10 degrees or more, the device will detuning, because the temperature difference was small and limited sensory perfection ...

Now we have a much more perfect sensors, so if anyone interested, I send my device schema. Of course it will not work in Condor :lol:

edit: I thought that my idea maybe unclear, so Sl & Sr means tendency (trend) of temperature at the end of wings. Device points the way to the lift before we enter to him. It's like a thermalhelper - I'm not sure if it would be legal to use :wink: :lol:
It also allows you to avoid the areas of sinking air at gliding section.
If lift is centered, the display looks like a case of 3 (left cyrcling) or 7 (right cyrcling)

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ThaiGliderLover
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Re: Word of advice on making use of thermals?

Postby ThaiGliderLover » Tue Dec 28, 2010 2:13 pm

Don't try to go to the "core" of the thermal, use the outer rim...

And maintain a 45˚ bank while thermalling, at the same time of finding balance between banking and rudder...



To tell you the truth, thermals are my least favorite form of lift, my fav is wave. Because you can always use the terrain to tell you where the lift source is... :)
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Russell
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Re: Word of advice on making use of thermals?

Postby Russell » Mon Jan 24, 2011 9:49 pm

Hi all,
Best way for a novice to gain height in a thermal is not to think to much :wink: Just turn at 45 degrees keep speed constant at the best L/D for your glider.{DO NOT KEEP LOOKING INSIDE THE COCKPIT AT THE VARIO}look at your attitude only this will keep your speed constant,Use of trim is a MUST.When beep goes higher straighten out then go straight back into the turn.If you have lift all the way round the turn go with it dont try to muck about to much as coring will come with practise and there is a good chance you will fall out.But while turning remember to keep a good look out for other aircraft.
Simples :D

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Re: Word of advice on making use of thermals?

Postby MrTumnus » Tue Jan 25, 2011 9:45 am

Russell wrote:Hi all,
Best way for a novice to gain height in a thermal is not to think to much :wink: Just turn at 45 degrees keep speed constant at the best L/D for your glider.{DO NOT KEEP LOOKING INSIDE THE COCKPIT AT THE VARIO}look at your attitude only this will keep your speed constant,Use of trim is a MUST.When beep goes higher straighten out then go straight back into the turn.If you have lift all the way round the turn go with it dont try to muck about to much as coring will come with practise and there is a good chance you will fall out.But while turning remember to keep a good look out for other aircraft.
Simples :D


Why does everyone keep saying 45 bank? Often, if you've got a wide thermal you won't be able to center on it with that amount of bank?

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Re: Word of advice on making use of thermals?

Postby MrTumnus » Tue Jan 25, 2011 9:47 am

OXO wrote:My goal is to centre the thermal perfectly on the second circle. The first circle is for finding the core.

I also don't bother to recentre if the variation round the circle is less than 25%. It's better to spend that time on lookout and deciding what to do next.


My goal is to not have to center at all :lol: But, I will be improving my position in the thermal in every turn because in reality, your cross country speed is determined by your rate of climb.

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Re: Word of advice on making use of thermals?

Postby Russell » Tue Jan 25, 2011 7:45 pm

MrTumnus,
I agree with you but for a novice a good rule of thumb would be 45 degree bank.I think a novice once in and climbing should not try to bugger about to much as they then increase the chance of being spat out.I would suggest that a novice once in a thermal should only readjust the circle when a 1/4 of the turn is not in lift,then straighten when vario starts to peak.Keep it simple as a novice has to fly the glider as well as thinking about what to do when lift arrives,it is easy when you dont have to think about your control inputs.increasing the novices workload in small stages will not overload them into sloppy flying and sloppy flying make thermaling much much harder :wink:
I hope this helps someone
Russell

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Re: Word of advice on making use of thermals?

Postby Mr. Ike » Tue Jan 25, 2011 10:29 pm

Altering your circle EVERY turn is a bad thing to do. Center, make a few turns and observe what happens, center again and make a few turns, etc.

If you alter your circle every turn there is no way to know hot the thermal looks and where you are exactly. You NEED to make a few complete turns with constant bank and speed to know what is going on.

There is not a single pilot in the world who can keep his plane exactly centered. Very important is to keep the plane on a constant bank and a speed. staying exactly centered is only possible on exactly circular thermals of constant vertical speed and distribution around the core. (IE the none existent ideal thermal)

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Re: Word of advice on making use of thermals?

Postby MrTumnus » Wed Jan 26, 2011 9:49 am

Mr. Ike wrote:Altering your circle EVERY turn is a bad thing to do. Center, make a few turns and observe what happens, center again and make a few turns, etc.

If you alter your circle every turn there is no way to know hot the thermal looks and where you are exactly. You NEED to make a few complete turns with constant bank and speed to know what is going on.

There is not a single pilot in the world who can keep his plane exactly centered. Very important is to keep the plane on a constant bank and a speed. staying exactly centered is only possible on exactly circular thermals of constant vertical speed and distribution around the core. (IE the none existent ideal thermal)


The kind of thing I meant is if you fly into a much weaker bit of lift on the western side of the thermal on one revoloution, straighten up for a few seconds flying east and then continue the turn. I'm not sure that I agree with keeping the bank constant, as often you'll have to straighten out in one direction or tighten the turn when in stringest lift.


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