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Old Nov 05, 2012, 09:10 AM
Out of helis, sanity returning
Tallahassee, FL
Joined Feb 2009
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Thermals are where you find them

Or did someone already say that?

Rick
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Old Nov 06, 2012, 06:05 AM
Registered User
Windsor, Canada, near Detroit
Joined Jul 2007
4,878 Posts
on shape of thermals

i found this, providing data regarding the shape of thermals:

http://www.xcmag.com/2007/07/thermal...rt-1-thermals/

which looks very much the way cumulus nimbus behave
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Old Nov 06, 2012, 12:41 PM
LSF IV
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USA, TX, Corinth
Joined Jan 2009
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Quote:
Originally Posted by DLGjunkyard View Post
Anyone know what kind of glider Joe is using in this video?

JimmyMac in Dallas
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Old Nov 09, 2012, 06:31 AM
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Windsor, Canada, near Detroit
Joined Jul 2007
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thermals and computer science

anything goes?
could it be that there is already technology to find out the shape of thermals, just as there is to track down storms in 3 dimensions? like by detecting small variations in temp or wind flow. just to learn for sure how they look.
sometimes comps do things that are beyond our wildest dreams, but others they don't some that look easy for us.
the other day i watched a documentary where a scientist in japan deviced a way to track down the shape of volcanos deep underground by using some sort of space radiation. so, why not?
for instance, i got a telemetry system that sends data from my plane about the voltage in the battery, that weighs 16 grams, and costs $50. i could not dream about anything like it.

the future is here, and we live beyond science-fiction.
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Old Nov 09, 2012, 06:35 AM
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Windsor, Canada, near Detroit
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shape?

Quote:
Originally Posted by seanpcola View Post
If only I was up-to-date with my cell phone I could have made some awesome videos of thermals a couple of weeks ago. Had to drive over to a farming community. They're in a serious drought and the ground is extremely dry and dusty. You could watch them start small, build, move down wind, etc., even break loose and climb. Would have been a great tutorial.
ok, so we count on your description of them: could you see their shape? how it evolved? how they started? anything!
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Old Nov 09, 2012, 06:51 AM
ein flugel schplinterizer
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USA, FL, Pensacola
Joined Sep 2004
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Oh yeah. Watching the ones in the plowed fields was simple and clearly defined.

First there was a small area of "disturbance", sort of a dust cloud maybe 5' high. As it fed you could see the dust being sucked into it and a circular pattern develop. .All the time it's moving downwind, gathering more warm air and the rotational speed picked up slowly Very defined tornado shape, IOWs as it gained height the upper part spread making the funnel. It looked like the circular speed was slower the higher it went but that was probably more a function of the larger diameter since the dust was actually moving a greater distance. As the funnel encountered a tree line it would break loose and continue to climb. On this particular day the thermals hit a certain altitude and obtain equilibrium. When that happened the rotation slowed or maybe stopped while the dust cloud continued downwind until either the air finally lost energy or went out of my line of sight.

Nothing unexpected just awesome to see in person.
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Old Nov 09, 2012, 07:20 AM
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Joined Jan 2003
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Unusual thermal

A rather unusual event involving thermals several years ago. A friend, Al Clark was flying a S Tee equipped with a drop mechnism at the Redstone Arsenal. He had rigged a small plastic Rhino with a simple parachute to drop. When he dropped it from the plane it was caught in a thermal taking it upward and moving towards the SE. We watched in total amazement for quite a while as it moved off. It later reappeared coming back in a North Westerly direction and finally landing on the field some 20 minutes later.

We later went to the Glider field about a mile away where the pilots were complaining about the lack of thermal. You figure that one!

If I had not witnessed this myself I would have doubts, but it is absolutely true.

Sworn to by:
Ron

Al told me I was off on the time and that it was actually 32 minutes. I will allow that his memory is better than mine.
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Old Nov 09, 2012, 08:03 AM
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What I know about thermals could hardly fill a bottle cap.

What I have observed is this: thermals can be:

Either wide or narrow
Either "soft" (ill-defined, mushy) or "hard" (definite boundaries)
Either singular or multiple (several feeders to a larger, higher thermal)
Either low-starting or high starting (you have to be high to find the lift)
Either topping out low or topping out high
Either stationary or moving
Either stable or transitory

In my experience, a thermal that appears to be non-circular is usually part of a family of small, feeder thermals pushing a bigger one (usually higher - keep working to get into it).

On any given day, at any given field, my first flights are to gage the thermals (wide/soft/low/etc.) All subsequent flights are input for re-evaluation of what's going on (they seem to be getting higher, that sort of thing).

In all my RC soaring so far, I estimate that about 0.01% has been in conditions of flat thermal activity, without perceptible convection. Even if there is not lift to climb in, there are usually bumps and bubbles that can prolong flight.

I am always amazed at how tenascious many folks are at circling in sink. What I hear them say as they do so is usually something like "there was lift here yesterday! I remember! I just need to work it better!" Sorry, guys, but if your airplane is not climbing, you should leave the area.

Another post earlier hit about right: the best thermals come when your batteries are low, your airplane is in the car, the winch is broke, and you'd have to circle directly in the sun anyway.

Good luck!

Yours, Greg
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Old Nov 09, 2012, 08:39 AM
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Windsor, Canada, near Detroit
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thermals: the making

Quote:
Originally Posted by seanpcola View Post
Oh yeah. Watching the ones in the plowed fields was simple and clearly defined.

First there was a small area of "disturbance", sort of a dust cloud maybe 5' high. As it fed you could see the dust being sucked into it and a circular pattern develop. .All the time it's moving downwind, gathering more warm air and the rotational speed picked up slowly Very defined tornado shape, IOWs as it gained height the upper part spread making the funnel. It looked like the circular speed was slower the higher it went but that was probably more a function of the larger diameter since the dust was actually moving a greater distance. As the funnel encountered a tree line it would break loose and continue to climb. On this particular day the thermals hit a certain altitude and obtain equilibrium. When that happened the rotation slowed or maybe stopped while the dust cloud continued downwind until either the air finally lost energy or went out of my line of sight.
Nothing unexpected just awesome to see in person.
terrific. thank you very much. this 1st hand input is a milestone and contributes largely to our learning on thermals. i wish i could watch it!
1 last question? do you remember which way was it turning? left or right?
regards
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Old Nov 09, 2012, 04:50 PM
Ochroma Lagopus Tekton
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Blackstock, South Carolina
Joined Sep 2007
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My first thermal was when I was in Jr High (A.K.A. "middle") school. Not RC but paper airplanes (budget free flight? ). Anyway, our little club was in the "girl's field", which is a large asphalt area. I waited until the air was calm then threw my plane straight up for altitude. I knew nothing about the characteristics of thermals back then other than they were rising masses of warm air., But as soon as I saw that the slowly circling plane was not coming down, but going up I knew what I had. I had thrown it right into the core. With no imput from me (obviously) it just kept circling upwards, and slowly drifting southeast with the "bubble" until it was lost from sight.

I was on cloud nine the rest of the day.
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Old Nov 09, 2012, 06:36 PM
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Windsor, Canada, near Detroit
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treasures...

Quote:
Originally Posted by Fly Wheel View Post
My first thermal was when I was in Jr High (A.K.A. "middle") school. Not RC but paper airplanes (budget free flight? ). Anyway, our little club was in the "girl's field", which is a large asphalt area. I waited until the air was calm then threw my plane straight up for altitude. I knew nothing about the characteristics of thermals back then other than they were rising masses of warm air., But as soon as I saw that the slowly circling plane was not coming down, but going up I knew what I had. I had thrown it right into the core. With no imput from me (obviously) it just kept circling upwards, and slowly drifting southeast with the "bubble" until it was lost from sight.

I was on cloud nine the rest of the day.
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.
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Old Nov 09, 2012, 07:27 PM
AKA - The "Flywheel"
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SOAR Chicago!!!
Joined Jan 2005
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A couple of years back, I was driving to work, it was early fall, and the farmers were harvesting corn. I saw a thermal start, as a dust devil, sucking up corn leaves, and soon, it grew to over a half mile wide, and the corn leaves were very high, easily a thousand feet or more. During this episode, a half dozen or so vultures ventured into the area, and they climbed out like they had rockets attached to them. It was the most awesome visual display I have ever seen, of a thermal, and its power.

Steve
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Old Nov 09, 2012, 08:00 PM
ein flugel schplinterizer
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USA, FL, Pensacola
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Phil,

The thermals on the day that I described were turning counter-clockwise as viewed from above if that helps.
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Old Nov 09, 2012, 08:11 PM
Now fortified with carbon
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A Whirlwind Hay Devil For Kids (2 min 39 sec)
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Old Nov 09, 2012, 08:12 PM
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Tornado (Giant Dust Devil) Forming In The Middle Of Soccer Field (1 min 11 sec)
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