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Old Nov 09, 2012, 08:14 PM
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Water Tornado Palm Springs (1 min 21 sec)
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Old Nov 09, 2012, 08:28 PM
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mini tornado at sports day! (1 min 52 sec)
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Old Nov 09, 2012, 08:55 PM
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http://www.youtube.com/watch?feature...&v=4zW-OB6ox6Y
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Old Nov 10, 2012, 02:48 AM
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left or right?

Quote:
Originally Posted by seanpcola View Post
Phil,

The thermals on the day that I described were turning counter-clockwise as viewed from above if that helps.
sure it does. thank you very much.

as a free flighter i was taught that thermals turn left (counterclockwise) in the north hemisphere (same as most storms), due to the rotation of the earth, therefore we should trim our models to turn left too, so they get dragged by the turning stream, so i have trimmed my models to the left (as free flighters all over the north hemisphere do) and they get into thermals very well.
but i still get input that some turn right and get into thermal as well, hence my interest.
hopefully with more data as this from you, someday i will reach a conclusion.
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Old Nov 10, 2012, 03:02 AM
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more weird things with thermals

as this thing evolves, more memories (some of them weird) resurface. i recall 1 day a plane was thermaling high in no wind when suddenly the rubber bands that held the wing to the fuselage gave up and the fuselage with its tail came down like a bomb.
but not the wing. to our amazement, it began to turn on its lateral axis and kept doing it, but didn't fall. it began to climb very slowly. with no wind, it remained on same spot, in slow motion. it lasted for about 30 minutes until we lost it over our heads, to never be seen again.
scratch 1 wing.
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Old Nov 10, 2012, 03:06 AM
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to the left

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Originally Posted by DLGjunkyard View Post
and it turns to the left.
for the records.
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Old Nov 10, 2012, 03:18 AM
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southern hemisphere

then i saw this tornado at chile (southern hemisphere) but it turns to the left too. so, could it be that they turn left anywhere, be north or south?

Tornado en Alto Jahuel - Buin ( Chile ) (2 min 0 sec)


intriguing.

i hope some aussies are watching this and bring their comments.
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Old Nov 10, 2012, 12:39 PM
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Great Thread!

Phil, thanks for starting it!

4 days ago, I had a nice clear calm morning with cool air from a cool night. The sky was very calm and had the look of an inversion so I figured since it wasn't raining and the sun was out, I'd go fly even though there "shouldn't" be any good thermals, at least I could take all the ballast out and enjoy watching my plane float around slowly.

By the time I got to the place where I fly the most(about 10+ soccer fields, 5+ on the west side,5+ on the east side of a central bike and walking path, surrounded by trees, but low trees with lots of recently fallen leaves on the south end of the field), and got my hi-start setup, plane put together, etc,a few low clouds started to form to the north side of town, a slight, slight breeze started to come from the south, passing over the low trees with lots of dead fallen leaves on the ground. I launched toward the trees into the wind.

What started out a pretty cool/cold morning turned to really warm T-shirt temps really quickly in that protected sunny set of soccer fields. You can guess what's coming next: Really NICE SMOOTH THERMALS!

They weren't very powerful, nor did they seem to go very high since it was still pretty humid from the rains recently but they were pretty abundant. As soon as each one I was in fizzled out(or I just lost the core?), more than half the flights I was able to head back into the wind over the trees to the south and find another thermal. One flight I did this 4 times. My plane never seemed to go up over 250 feet each time but it was pretty fun. Actually it was more fun than "specking" out since the plane was closer and I could see it better and it was just fun fishing for thermals at that height with a nice light unballasted glider, in this case, my 2 meter almost-completely-modified Great Planes Spirit I finished this summer.

This was really a great day for a plane like what I was using, it's probably the most aerodymically clean and sleek plane I've built yet, and the first time I got the weight(30.5oz) in the weight range stated on the box. I think the lighter weight and aero-cleanliness made this possible. I'm not sure If I could have had flying that good with my 2M Easy Eagle that's heavier and boxier.

Gotta Go- Paul
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Old Nov 10, 2012, 02:53 PM
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Quote:
Originally Posted by phil alvirez View Post
great to have experiences like that. and you will bring those memories time and again.

and here i come again: do you remember which way was it turning?
am really curious about which way thermals turn.
Well the turn was obviously dictated by the "design" of the plane - folded paper airplanes are naturally free flight. but if I remember correctly it was following a lazy counter clockwise circle as seen from the ground.

And for the record, a thermal that is only a few yards across is far too small to be affected by coroilis forces, the earth is just to large for that. Storms, the width of which are measured in miles can be, and are.
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Old Nov 10, 2012, 05:12 PM
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either way

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Originally Posted by Fly Wheel View Post
Well the turn was obviously dictated by the "design" of the plane - folded paper airplanes are naturally free flight. but if I remember correctly it was following a lazy counter clockwise circle as seen from the ground.

And for the record, a thermal that is only a few yards across is far too small to be affected by coroilis forces, the earth is just to large for that. Storms, the width of which are measured in miles can be, and are.
thank you for answering my request. what you say is right hand turn to me.

for all that i see so far in videos regarding dust devils, they all turn left, but as i said, the more data all bring, the more chances we have to learn if thermals turn, and if so, if they do it in certain direction, be it all the time, or more certain way than the other.
i am not an advocate of nothing, just trying to learn from all of you guys based on your experience, and ideally, if some can bring videos so we can see what is really going on.
regards.
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Old Nov 10, 2012, 05:24 PM
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Quote:
Originally Posted by phil alvirez View Post
thank you for answering my request. what you say is right hand turn to me.

for all that i see so far in videos regarding dust devils, they all turn left, but as i said, the more data all bring, the more chances we have to learn if thermals turn, and if so, if they do it in certain direction, be it all the time, or more certain way than the other.
i am not an advocate of nothing, just trying to learn from all of you guys based on your experience, and ideally, if some can bring videos so we can see what is really going on.
regards.
Defining the term thermal would help.

I have flown what could be called thermals where entire valleys rise giving lift.Its possible to have lift with little to no visible wind. Wonder winds as they are known in the full size soaring world
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Old Nov 10, 2012, 07:08 PM
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no wind and thermals

i remember a day that there was no wind, and i was maidening a nordik (free flight) sailplane. there were several guys around. i towed it with a short line and released it at about 15 feet (5 meters) and it began to circle around us. it lasted for about 5 minutes without landing, until it came to the reach of my hand and i grabbed it. all were fascinated with the seemingly magic plane. the soil was releasing enough warm air to keep the plane airborne. no shape, just a large area of warm air raising slowly.
but that is kind of an exception, as there is almost always some wind and most thermals have a definite diameter, and are released from earth at certain intervals that we can feel, as some wind blows and stops by cycles like say 2 minutes.
i think the definition of a thermal is: 'a mass of air that as is warmer than surroundings goes up, no matter what shape or size'.
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Old Nov 10, 2012, 07:14 PM
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I'm pretty sure a thermal could turn in either direction, it just depends on what forces are there to initiate the rotation. Maybe a thermal out in the middle of a field with no other obstacles will follow the north/south hemisphere "rule", but if it kicks up near an obstacle such as a tree line or something, with a little breeze, I could see it kicking off in either direction. If I fill my tub with water and open the drain, I can get the water to spin in either direction by giving it a little swirl with my finger. Once it's started in a direction, it'll hold that until the tub drains. Too much momentum for any other weak forces to change what's happening. Just speculation of course.
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Old Nov 10, 2012, 07:37 PM
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In Austria.. right hand turning
Tornado in Pupping (4 min 16 sec)


Yes, thermals turn both ways, and sometimes no way. They are bubbles and
ribbons, ridges and jets and they pull the wind this way and that. There are even
thermals that remain nearly stationary as the wind blows through them because
they're only feeding from the upwind side. I think the biggest thing people overlook is
how much horizontal motion is usually involved to get a thermal going
and to keep it fed and how terrain triggers and guides thermals because of
deflected horizontal movement of the air close to the ground. While warm air wants to rise if
there's cooler air above, the rising air has to be replaced by air from the sides which
may be warm, in which case it feeds and accelerates the thermal upward, while also
accelerating the horizontal winds below. We all know to watch the
flags pointing toward the thermal, but the trick is to understand how the terrain will
influence that wind so you know where to go looking for the next thermal and the next.

I wrote up quite a lengthy post description of slermals (slope + thermal) a few years back
complete with some pretty 3D diagrams I made up to represent my visualization of thermals.
Check it out.
http://www.rcgroups.com/forums/showt...64#post4966743

ian
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Old Nov 10, 2012, 07:45 PM
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do they always turn? or just some times?

Quote:
Originally Posted by GliderJim View Post
I'm pretty sure a thermal could turn in either direction, it just depends on what forces are there to initiate the rotation. Maybe a thermal out in the middle of a field with no other obstacles will follow the north/south hemisphere "rule", but if it kicks up near an obstacle such as a tree line or something, with a little breeze, I could see it kicking off in either direction. If I fill my tub with water and open the drain, I can get the water to spin in either direction by giving it a little swirl with my finger. Once it's started in a direction, it'll hold that until the tub drains. Too much momentum for any other weak forces to change what's happening. Just speculation of course.
speculation, yes, but with lots of common sense. i agree with your reasoning.
(and i have done the same as you with the water in the tub)
maybe even they not always turn,and just go up like a cylinder. have you seen a cumulus developing?
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