Coring thermals: clockwise or counterclockwise

[RCPC]

i am a tenderfoot when it comes to thermals but i was wondering whether it is better to core thermals in a clockwise (CW) or counterclockwise (CCW) direction as viewed from the top. lets simplify it and consider the northern hemisphere ONLY.

i think it might be an antiquated way to look at thermals but dont some of them have a circular motion? dont some of them rotate in the counterclockwise direction in the northern hemisphere and clockwise in the souther hemisphere as viewed from the top due to the coriolis effect? i know some thermals form into a "bubble" and break loose from the ground but some maintain connection with the ground and form a "trunk" leading up to the top of the thermal. the trunk would then have some rotational component due to the coriolis effect.

i was thinking that the plane wouldnt care the rotational direction of the thermal because all it sees is the airspeed even though the ground speed is theoretically different when flying in the CW or CCW direction.

but perhaps there would be an advantage to flying in one direction over the other since if you fall out of the thermal the momentary airspeed will change. i would think that coring CCW would be the best because if you fall out of the thermal the airspeed actually increases in the sense of the glider since the wind begins to move more slowly from behind you, in essence the wind speeds up with respect to the forward motion of the glider. this might make it less visible if you fall out the thermal but you wouldnt be punished as much because you would actually increase your airspeed and hence lift. this might make determining the core more difficult but also less detrimental if you fall out of the core.

this might be total BS so i would love to hear what you think. i have have minimal thermal experience and am such a poor pilot that flying CW and CCW in a thermal has not appreciable difference on lift from what i have seen. should i just do what is most comfortable? thank in advance for the advice.
-paul

[rdeis]

Yes, there is a rotational component, and how much the component matters seems to be an ongoing debate.

Making a smooth coodrinated turn is most impotant, so learn to do that first. And regardless of whether the rotation matters much it's wise to get comfortable with thermal turns in either direction-- when you're sharing air you need to enter the thermal with the same direction of turn as the guys that got in to it ahead of you.

[F3X]

You may get a lot of conflicting technical theory about this one but what counts is that you are actually IN the thermal. Also do YOU like to thermal to the left ior right? One way is probably better for you to fly more efficient.
So fly the direction you fly the best and stay in the thermal and you can't go wrong.

[winchdoc]

There is a purely theoretical answer to this, but I believe that difference is more easily offset by making fewer mistakes in a thermal turn.

I circle the SAME DIRECTION as the first guy in the bubble. More of an etiquitte thing than theoretical aerodynamical thing.
I've had soaring birds LEAVE the thermal just because I was circling the other direction in the same stack.

WinchDoc
Who still flies in thermals from time to time...

[O.L. Adcock]

I don't think it makes a hill of beans either way. Good advice above. Some of us turn one direction better then the other, for me it's left, but making fewer mistakes probably more then makes up for any efficiency difference due to direction....O.L.

[David Forbes]

This might answer your question, look down near the bottom of the page under Thermal Myths. http://cires.colorado.edu/~angevine/thermals_2006.htm
Dave, who's glad to hear he's not the only one that has a circle left default mode

[Batmanwpg]

I don't think it makes a hill of beans either way. Good advice above. Some of us turn one direction better then the other, for me it's left, but making fewer mistakes probably more then makes up for any efficiency difference due to direction....O.L.


Good advice.
RCPC- do a search about this in these forums and you'll find plenty of goop on this subject.

Me who turns left and right to get him higher.

[Guz]

It's fifty-fifty. Some thermals I get better lift with CW rotation, some with CCW rotation.

About the only thing I do consistently is when trying a thermal with birds or other modelers, is to do the same rotation.

Birds KNOW which way to turn. They only thing I haven't done (kicking myself now I think about it) is to make notes on which way birds go in thermals. Do they consistently fly CW or CCW in thermals?

As for flying with other modelers, who ever is in the thermal first, they dictate the rotation. I have learned the hard way that if you fly opposite rotation, you tend to have heavy damage mid air collisions. :(

[hogfarmer]

The only time I notice thermals really rotate is in very strong dust devils, and I think the direction is unpredictable, probably based on things like local wind and terrain features more then the Coriolis effect. Besides in my experience its nearly impossible to thermal in the small bullet dusties.

In larger thermals there is very little rotation if at all, sometimes you even notice eddies form on the edge of the thermal, also rotating in either direction. The Coriolis effect is too small to effect thermals, been discussed before. Just look at thunder storms, the tops of the largest thermals, and they show no predictable rotation.

[hogfarmer]

BTW that website referenced about thermals is much like other papers I've read about thermals. A lot of really good facts and information, but mixed in with a lot of opinion, over simplifications, and assumptions. Some of the assumptions have been shown to not be accurate in other thermal models; for example the way trigger points work (or don't), the notion that there is some surface tension with the thermal, thermal 'bubbles', I'm sure there are more too.

I've never read a good paper on how thermals work that can all be proven and is without dispute. Some parts of Denis Pagen's book "Understanding the Sky" and almost every other noteworthy publications on the subject have been disproven by modern, creditable sources, also.

[spinolio]

It is something to consider, I never really thought about it. I usually enter using a left turn (counter clockwise), unless someones already there. It just feels better to me. I will be watching in the future that's for sure.

[Tim Wolff]

Left.

[Forest Flyer]

We had a good long (and often interesting) discussion of thermal rotation not too long ago. See the link below.

http://www.rcgroups.com/forums/showthread.php?t=657211

[Phoebusflyer]

Like O.L. said, " Don't make a hill of beans", as long as you are IN the thermal. Just go out and have fun and learn what works best and causes the most FUN for YOU!!!!!! Clockwise, counterclockwise, who cares? HAVE FUN!!!!

[David Forbes]

Thanks, it's worth reading again, that's where I found the link in post #6
Dave

[chan1pro]

Here is a link on YouTube where you can study them for yourselves or just type in “Dust Devils” in the search field.

Dust Devils Miniature Tornados

http://www.youtube.com/watch?v=8Xia9Fk6k_k

Julian
Grapevine, TX

[John Gallagher]

I have observed birds in my area. Turkey vultures fly in opposite directions in the same thermal. I've seen it a number of times. Maybe the Jersey Vultures are anti-social and don't trust each other to fly in the same direction.

[chan1pro]

Here is a giant one. YouTube has a bunch of Videos.

http://www.youtube.com/watch?v=VDcRe1_bHjY&feature=related

and a small one.

http://www.youtube.com/watch?v=AwKc7H5gIWo&feature=related

[lincoln]

Important to be able to circle comfortably in either direction. Otherwise you will waste energy when the thermal is on the other side. Or you'll have a problem if your landing pattern has to come in on the other side.

Seems to me that sometimes the direction of rotation does make some difference, but I think if you don't stay consistently centered, the direction may change. And reversing direction costs energy.

[Hossfly72]

I've discovered the ULTIMATE answer for this ever-present debate. Came from the "Old Buzzard" hisself... (seems like all of our tips and hints have come from him doesn't it?)

Try to develop skill at circling in each direction. That being said, or written, I prefer circling to the right while flying R/C gliders, but if you put me in a full scale Cessna and I HATE, HATE, HATE right hand traffic patterns! My wife says I have issues. I don't know if she's really talking about airplanes though...LOL

Edit: Lincoln posted the same idea while I was sortin out my English... I can't type for diddly!!! But at least I'm not out there alone being weird again!!!

[lincoln]

Note that we see two different directions in the last two videos (both Northern Hemisphere). However, I have no idea why they sound so musical. ;-p

[Hossfly72]

Those are obviously EVP (Electronic Voice Phenomenon) enhanced. Thermal music is usually VERY quiet and I can never quite make out the words. LOL

[RCPC]

sorry for posting a redundant thread. i searched this morning for info but was searching for "thermal coring direction" and got squat in terms of an answer. i then searched for "thermal rotation" and JACKPOT! i have all the info i need for now. i have been digesting it for some time now (a couple hours) and will likely have more questions but will post them in the other thread.

sorry for the redundancy, folks. go ahead, put me on your ignore list :o sorry.

i am going to close this thread since i think it will only repeat all the work that has gone into the other thread and clutter the forum. again, very sorry.

[Paul Naton]

The best thermal and micro lift instructional DVD:
Required classwork for all soaring pilots.

http://radiocarbonart.com/Pages/asecthermalmain.html

http://www.youtube.com/watch?v=ucYXSedRHH0

Answers about a hundred of your guys repeated questions.

Paul Naton
The DVD guy and LZ sponsor

[RCPC]

oh, by the way, thank you all for the info so far. i learned a lot about "thermal etiquette" when flying with others. again, very sorry for the redundant thread.