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        Discussion THERMALS: what do you know?

#1 phil alvirez Nov 03, 2012 05:00 AM

THERMALS: what do you know?
 
this is for beginners or experts alike:

if we are in this forum, what do you know about them?
their shape; how they are generated, how they evolve; if they turn;
and if so, if they turn in certain direction (left, right);
how do you get into them;
how do you detect them;
links;
your experience;
examples of how you get into them.

please bring only polite and positive comments.

#2 phil alvirez Nov 03, 2012 05:02 AM

shape of thermals
 
an example:
have you wondered what shape a thermal has? a bubble? a cylinder?

i found an article in a model airplane's magazine (american modeler-august 1961-page 42), where the author (Bill Winter) provides a link on the thermals shape and behaviour, from an article from Soaring magazine, by Clarence Cone, issues april/may/june 1961.
this is the link: http://soaringweb.org/Soaring_Index/...61_Apr_08.html page 8.
edit: somehow the link does not work anymore. will try to bring it back.

#3 Wylie Shaw Nov 03, 2012 06:27 AM

They go up!!!!!!:D:D:D;):eek:

#4 tkallev Nov 03, 2012 08:15 AM

Thermals can be shaped like bubbles, smoke rings, tornadic (dust devils) ... the only way to tell is to get into it and fly in the rising air.

#5 ciurpita Nov 03, 2012 11:30 AM

Quote:

Originally Posted by phil alvirez (Post 23170665)
if we are in this forum, what do you know about them?
their shape; how they are generated, how they evolve; if they turn;
and if so, if they turn in certain direction (left, right);
how do you get into them;
how do you detect them;

the sun heats the ground which heats the air near the ground. Darker ground cover heats more quickly.
eventually the heated air breaks from the ground and rises.
as it rises it cools, but continues to rise as long as the surrounding air is cooler than the rising air. see lapse rate and soaring weather forecast.
See Lee Murrays article in the September '99 issue of RCSD.
When thermals rise, air flows under them to fill the vacuum they form. Should you fly with or against a sudden breeze formed by a thermal?

when/if the air cools to the dew point of the surrounding air, the water condenses and forms clouds.
clouds with flat or concave bottoms are good indicators of thermals. multiple thermals may join under a single cloud.

#6 DLGjunkyard Nov 03, 2012 02:37 PM

Many thermals are in the shape of sea weed in that they sway with the wind and often feed from the ground. Its actually more likely than the bubble example often used .
Sink will often be found around the perimeter but more likely around the base.
Flying full size has taught me that there really is no consistent shape from one thermal to the other Thermals come in many shapes, sizes and textures. Some thermals are too small to circle in, while others can be so huge that you have to try to find your way out of them. Some are just strong enough to maintain your altitude, while others take you up so fast it can be disconcerting.

#7 seanpcola Nov 03, 2012 04:17 PM

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.

#8 lincoln Nov 03, 2012 04:21 PM

For small thermals, you could probably release dust, milkweed seeds, soap bubbles, etc. into them and get some idea of the shape. Or just wait for a dust devil, but they might not be typical. Thornburg recommends, among other things, making little parachutes out of dry cleaner bags and releasing those to visualize what lift is doing.

If you see a flock of small birds randomly flying around in a small area, a good distance off the ground (say, 50 feet or more), they are probably eating bugs carried upwards by a thermal. You can also find thermals by watching for larger birds circling further up (as long as they aren't flapping). I've done this many times. Also, if you find a thermal, they'll often come to you.

A quick wind shift often means the thermal is close, a slower shift means further away, or perhaps just larger. Obviously a wind shift that feels warm is better than one that feels cold. The prevailing wind affects the perceived vs. real direction of a thermal. The thermal may be a bit downwind (by the prevailing wind) of where the shift points to. Also, the top of a thermal is often downwind of the bottom of it, since the wind gets stronger aloft.

Mostly I find thermals by noticing that the glider gets lively.

I think the turning direction is fairly random, and there seems to be some advantage, sometimes, circling in one direction instead of the other, presumably against the direction the thermal is spinning, so you don't have to bank as much.

#9 War is Peace Nov 03, 2012 04:27 PM

From many years of flying I have learned the following thermal facts:

The best lift is always directly in the sun where you can't see the model.

The best thermal of the day happens shortly after you put your glider in the car.

Birds always show the location of a thermal when you are too low to get there.

The winch always breaks down when its your turn to launch into the "hat sucker" everyone is flying away in.

And..... when you finally catch the ultimate monster thermal, your transmitter will be running low on batteries and you will have to pull out and land.

I do know this: thermals are invisible, they move, and they usually evade us. But it takes only one good thermal to hook you for life.

#10 seanpcola Nov 03, 2012 04:34 PM

Quote:

Originally Posted by Scott Whitney (Post 23174226)
From many years of flying I have learned the following thermal facts:

The best lift is always directly in the sun where you can't see the model.

The best thermal of the day happens shortly after you put your glider in the car.

Birds always show the location of a thermal when you are too low to get there.

The winch always breaks down when its your turn to launch into the "hat sucker" everyone is flying away in.

And..... when you finally catch the ultimate monster thermal, your transmitter will be running low on batteries and you will have to pull out and land.

I do know this: thermals are invisible, they move, and they usually evade us. But it takes only one good thermal to hook you for life.

Enough said. Scott is 100% on every comment here. :D

#11 LVsoaring Nov 03, 2012 07:01 PM

Quote:

Originally Posted by Scott Whitney (Post 23174226)
From many years of flying I have learned the following thermal facts:

The best lift is always directly in the sun where you can't see the model.

The best thermal of the day happens shortly after you put your glider in the car.

Birds always show the location of a thermal when you are too low to get there.

The winch always breaks down when its your turn to launch into the "hat sucker" everyone is flying away in.

And..... when you finally catch the ultimate monster thermal, your transmitter will be running low on batteries and you will have to pull out and land.

I do know this: thermals are invisible, they move, and they usually evade us. But it takes only one good thermal to hook you for life.

That, my friends, is absolutely true, and is the common glue that binds us here all together. There's not a one of us here who can forget hooking that first one, and when you landed, wanted nothing more than to do it again.

#12 Tappet Nov 04, 2012 09:32 AM

Search "Joe Wurts" on YouTube and watch the first video that comes up.
Almost an hour long.

#13 DLGjunkyard Nov 04, 2012 11:01 AM

Quote:

Originally Posted by Tappet (Post 23179361)
Search "Joe Wurts" on YouTube and watch the first video that comes up.
Almost an hour long.

Joe Wurts on soaring (1 hr 22 min 27 sec)

#14 jetmaven Nov 04, 2012 05:16 PM

What I know about thermals is that they were few and far between in my part of central Florida today

#15 Soarmark Nov 04, 2012 05:30 PM

Well there were many here in Texas today! And I can say each one was different. Doughnuts, cylinders, broad fields you name it.

BTW, Jimmy Mac made his two hour for LSF today. As soon as I decided to start a two hour clock 46 minutes into a flight I fell out of the sky. :confused:

Still had a great time with temps in the 70's and multiple low level saves with my Perfect. :D I love this hobby, better than golf or fishing and probably more challenging. :eek:


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