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Please help my Radian find lift

Old 07-06-2010, 06:07 AM
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mclarkson
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Default Please help my Radian find lift

I was at the R/C park the other. It was hot with lots of puffy clouds everywhere. One guy remarked to me that it was a perfect day for thermals. I think he was right. But I canít find them. Largely, I just donít know where to look.

Iíve read lots of stuff on the internet, such as this - http://f4bscale.worldonline.co.uk/Thermals.htm - but itís just not getting me anywhere.

Many gliding guides Iíve read talk a lot about hills but in Kansas, we have no hills at all.


I fly in big open fields of wheat or pasture grass, bordered on all sides by 2-lane blacktop roads. I'm attaching a photo to show you what I'm talking about.


Am I doomed? Are thermals hiding in here? I suspect I might be able to get something off the roads, but Iíve had no actual success.

Can I figure out a place to consistently find thermals? Or do I need to follow them across the countryside, like the Blackfoot did the buffalo?

Thermal hunting guides Iíve read mention clues: the plane will slow down, or tip a wing slightly. When the wind is 8MPH gusting to 16MPH, and bouncing between SSE, S, and SSW, youíre not going to notice a subtle tipping of the wing Ė at least, Iím not. In Kansas, a calm day is anything below 20 MPH. Days with no wind are virtually non-existent. Yet I know people fly gliders successfully in this kind of wind.

Others talk about walking around the field, feeling the warm air on your face and so on. Again, 18MPH winds make noticing subtle updrafts a bit more challenging, and this doesnít help at all if one happens to be flying from my local R/C field, where you only have one small area for launching and landing. If you want to find any thermals, youíve got to find them on the wing (and theyíd better not be on the wrong side of the pit fence!)

And while weíre on the subject of the wind, whatís the best way, in general, to work it? Thereís a lot of energy there and Iíd like to use it as effectively as possible. Should I try to fly mostly into the wind? With the wind? Across the wind?

Any pointers and suggestions welcome. I want to keep my Radian up there as long as possible.
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Old 07-06-2010, 09:28 AM
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Larry3215
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The more wind you have the tougher it is to find - and stay in - the lift. Thermals move with the wind and dont stay in one spot. The stronger the wind is, the harder it is to find lift. It may be gone before you can be sure there was ever lift. At best on a windy day you will have to bail out sooner than you may want or risk being blown too far down wind.

In my experience, finding thermals is as much art as science and it takes practice to get to where you can read the plane.

I prefer to cheet when ever possible so I follow the hawks or other soaring birds when they are around. If your lucky enough to have any in your area, do what they do. They dont have any trouble finding lift if its there to be found

Fly into the wind to stay up the longest. Sometimes you will have to fly down wind or cross wind in your searching. Fly faster when doing that so you get back to the up wind flight as soon as possible.

I know Kansas is mostly flat, but if there is any kind of hill or ridge, you can use the lift from that to stay up too. Doesnt take much of a hill if the wind is strong enough. It may amaze you how hi ridge lift can take you. The lift zone will be just up-wind of the slope.

Mostly though - keep trying. It gets easier the more you do it
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Old 07-06-2010, 10:16 AM
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Thanks!

Originally Posted by Larry3215 View Post
I know Kansas is mostly flat, but if there is any kind of hill or ridge...
Clearly, you didn't click on my photo!

I rarely see hawks, etc. in the areas I fly; when I do, they are typically hovering in the wind, just downwind of the highway.

I didn't know if, say, thermals were more likely to occur in the middle of a big field, around the edges of the field, at random unrelated areas of the field, or never at all in a large field.

As to slope lift, any ideas how far upwards that effect extends?
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Old 07-06-2010, 01:23 PM
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Default Thermals

Hello Mclarkson,
Thermals are everywhere.
The first thing to remember is that they're generated by a heat differential. The sun shines down on land, and darker patches get warmer than the lighter areas.
Have you ever driven down a road on a hot day and seen the blacktop "Shimmering" or wavy lines over the road? Heat. The road is black and it absorbs the sunlight, then radiates heat back up.
Suppose you had an area of freshly-plowed dark earth, surrounded by green fields.
The plowed patch would be much hotter than the area around it. Soon the heat would be "hovering" over the field, a sort of bubble of warmer air.
Warm air rises.
The bubble would (sooner or later) become a well-defined mass with a definite shape. Some say it's doughnut-shape, others believe it's ball-shaped. What's known for sure is that as it starts to rise (like a hot air balloon) it stays connected to the ground (the original heat source) by a stem, (the "Feeder" Stem) and continues to suck more warm air into the bubble. Eventually the entire bubble becomes "Lighter" than the air around it. There are many common examples of this phenomenom in everyday life, and most are visible, unlike thermals. Soap bubbles, balloons, water bubbles rising from the bottom of a pan of boiling water.
The wind pushes against the warm air mass and it drifts downwind, still pulling any bits of warm air up into the bubble.
Eventually one of two things happen.
The entire bubble is bouyant enough to break the feeder stem and it rises. This would be a fully-formed (and usually large) thermal.
Or, it is broken free of the stem by a natural barrier, a "Trigger". A treeline, buildings, hills. This would normally occur BEFORE the bubble is fully formed and the thermal isn't as large.
Either way the bubble rises, taking birds, dust, insects and any other light objects with it. It generally has a circular rotation. The outer wall of the thermal is somewhat unstable, that's where the hot air is in contact with the surrounding cooloer air.
The center or "Core" is more stable, the temperature (differential) is protected by the wall.
An object with a light wing loading and clean aerodynamics will float along in the thermal, bouncing as it engages the wall and smoothing out in the core. Finding the center and circling smoothly is called "Coring" or "Coring Out". Best place to be for maximum rate of ascent.
It will rise until the cooler upper-level air begins to dissipate the warm air mass. Depending upon the size of the original thermal, wind speed and ambient temperature, it can rise as a formed shape several thousand feet, or only a few hundred feet.
In calmer weather the air mass will remain nearly round or ball-shaped.
In windy weather it will become enlongated, an oval longer in the direction of the wind.
The darker patch in the photo should be a good thermal generator. It you are directly downwind, on a sunny day it will generate thermals as long as the sun hits it. If the conditions are constant the thermals will occur regularly. Changes in the conditions break the cycle.
If you are on the ground directly downwind of the thermal you should feel a very slight change (warmer) in temperature. Then the windspeed will drop slightly. It will feel "Calm" for a few seconds. When the wind re-occurs it will be variable, not in the same direction, but slightly "sideways" or uncertain. That's the thermal, directly overhead.
Then the wind will pick up and it will feel cooler.
The thermal's gone. You missed it!
One inexpensive aid is a long (20') mylar strip tied to the top of a pole, directly upwind. Cassette tape will work, silver mylar is easier to see. Sit and watch it for awhile. You'll learn all you need to know.
Good Luck!
Ron
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Old 07-06-2010, 01:26 PM
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Hi MC;

I fly in conditions similar to yours and find few thermals; maybe two in a week.

Mine are always over a plowed field surrounded by fields of growing crops. The dark area will produce lift.

I also am luckier in the early morning and late afternoon when it is not cloudy and when it is least windy.

Can you get to a Walmart or High School to fly? Those big dark roofs and parking lots may hold some promise for you.

(edit) I like flying upwind because if the wind is 5'ish mph, it is sometimes possible to "stop" the Radian dead in its tracks (relative to the ground). That's fun for me.

'The Bum

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Old 07-06-2010, 01:58 PM
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Originally Posted by Larry3215 View Post
Fly into the wind to stay up the longest. Sometimes you will have to fly down wind or cross wind in your searching. Fly faster when doing that so you get back to the up wind flight as soon as possible.
That's an illusion, or the result of deliberately increasing airspeed when flying downwind thereby increasing rate of descent. If you maintain a constant airspeed (admittedly hard to judge from the ground) the glider will lose altitude at the same rate regardless of it's orientation with the wind.

Flying fast through sinking air minimizes loss of altitude by reducing time spent in the sink but wind direction alone doesn't necessitate a change in airspeed. If the plane couldn't "see" the ground it wouldn't "know" whether it's flying upwind or downwind.

.........Mike
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Old 07-06-2010, 06:25 PM
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I have caught a few thermals. I just watch the wing's and if they tip over, even for a split second I do a 360 turn as fast and flat as I can.
Where I live the thermals are generally weaker or calm days and get stronger when the wind picks up.
I find using hawks and eagles as thermal indicators a bit miss giving. They seem to find the greatest lift, fly a tight circle on days when my Radian get's nothing at all.
On days when I can get some really nice thermals their like jet fighters .
When the wind gets stronger (Say about 10-15 knots) ,Pelicans come out and put on a show using the thermals as lifts, catching the thermal, getting to the top and then gliding to the next.
I think when small puffy clouds are about is meant to be the best day for catching thermals ,there's meant to be one under every cloud just like a pot of gold is under every rainbow oh, and a leprechaun!!
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Old 07-06-2010, 07:07 PM
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Originally Posted by MS_in_NY View Post
That's an illusion, or the result of deliberately increasing airspeed when flying downwind thereby increasing rate of descent. If you maintain a constant airspeed (admittedly hard to judge from the ground) the glider will lose altitude at the same rate regardless of it's orientation with the wind.

Flying fast through sinking air minimizes loss of altitude by reducing time spent in the sink but wind direction alone doesn't necessitate a change in airspeed. If the plane couldn't "see" the ground it wouldn't "know" whether it's flying upwind or downwind.

.........Mike
True, but beginning glider pilots tend to maintain ground speed rather than air speed and tend to come down sooner unless they are oriented up-wind. Plus the next thermal - if there is one - will be coming from up-wind.
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Old 07-06-2010, 07:49 PM
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Originally Posted by Larry3215 View Post
True, but beginning glider pilots tend to maintain ground speed rather than air speed and tend to come down sooner unless they are oriented up-wind. Plus the next thermal - if there is one - will be coming from up-wind.
If you say so, but flying any model by ground speed is a recipe for disaster. The sooner noobs grasp the concept of flight in a moving mass of air the better IMO.

The only real advantage to flying upwind is it's more likely the noob (or anyone for that matter) will be able to make it back to the LZ. Thermals drift with the wind true, but they can lift off from anywhere. Searching for them downwind of the LZ is definitely risky business but they are no more likely to be upwind.

.......Mike
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Old 07-06-2010, 08:34 PM
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Mark:

Patton style, I checked out your videos for some clues on where you might find thermals. Just picking from your "Radian Flight (with ducks)" video, which I downloaded to dissect, maybe I have a couple of things to look for:

In the first two framegrabs, you can see the view upwind of your launch point. There is lots of contrast here with the light colored field to the left and darker one to the right, bisected by an even darker road. Working back and forth across this area could sniff out some thermals for you.

Now thermals start out as bubbles of warmer air sticking to the surface. They don't break free until they reach a critical mass and then a blob of warm air will rise up through the cooler air above the blister of warm. These blisters blow downwind until they hit something and then sometimes the whole blasted thing is cut loose. Look at that treeline to the right in the downwind view. I'll bet you can find thermals rising from that treeline separated from the dark field as the bubbles drift downwind into the trees. That's number one candidate in my book.

In framegrab number 4 I see a nice dark road cutting through a light colored field. Buy a vowel and check that one out!

Like everyone has said already, you have your work cut out for you in detecting the difference between thermal buffeting and plain old meaningless turbulence. If I were in Kansas right now, I'd be as frustrated as you. But if you imported Ed, I BET you'd learn something and he'd find thermals.
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Old 07-06-2010, 09:52 PM
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Originally Posted by MS_in_NY View Post
If you say so, but flying any model by ground speed is a recipe for disaster. The sooner noobs grasp the concept of flight in a moving mass of air the better IMO.

The only real advantage to flying upwind is it's more likely the noob (or anyone for that matter) will be able to make it back to the LZ. Thermals drift with the wind true, but they can lift off from anywhere. Searching for them downwind of the LZ is definitely risky business but they are no more likely to be upwind.

.......Mike
I think we are basically in agreement here.

However, if its windy, the thermals will be moving and like you say and its very risky to search down wind. In fact, generally I see no point in searching down wind unless you know there is a very strong thermal not far away.

If there are any up-wind, they will be moving toward you. Best to find them up-wind so you have more time to climb before you have to bail out too far downwind.
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Old 07-06-2010, 10:52 PM
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Hey, guys, thanks a lot! Rockin Robbins, I'll try to check out the areas you highlighted. I really appreciate that insight. I'm more than a little nervous about putting the plane up over a WalMart or something, but I'll keep an eye open for big, black parking lots with landing fields nearby.

As to ground speed vs. air speed ... flying a Radian in Kansas you are very aware of the difference. I have a short clip on Vimeo of my glider turning into the wind and then bobbing gently backwards at about 5MPH.

There's a phenomenon I've encountered many times which I call "The Wall". This generally occurs next to a road and/or treeline, and I suspect it's related to thermals or something else I could exploit if I knew how. The plane heads toward the road (or whatever) then slows, slows, slows ... stops. It's like there's a big, mushy wall in the air that I can't punch through. I posted an example here.
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Old 07-06-2010, 11:33 PM
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there are different flying days that are perplexing as to the cause and effect on our birds...i don't know why you couldn't penetrate the road barrier. seems to me the fields your flying in should have some popping thermals to suck the radian up and away. one thing to try is fly up real high where the thermals are expanding ,then the 360's will be larger and the searching should be broader to fly in.

I've flown along a mountain ridge in a hang glider that used the updraft to stay aloft,but when you fly away its down ya go......except on what was called a "wonder wind day". this was when lift could be found everywhere away from the ridge...out over the lz area and to get down was fun. you'll find lift off the road on a bright sunny day with low to no wind.

let us know when ya get caught up and soar high on a thermal.
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Old 07-10-2010, 06:58 AM
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Good advice here.

But you also might consider buying one of these: http://www.wingedshadow.com/thermalscout.html

They've been getting decent reviews.
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Old 07-10-2010, 08:48 AM
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Hey, Belem. I've given that some thought, but I wasn't sure I wanted something else tossing my plane around up there.
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Old 07-10-2010, 04:42 PM
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Cool Wag me baby!!!!

Originally Posted by Belem View Post
Good advice here.

But you also might consider buying one of these: http://www.wingedshadow.com/thermalscout.html

They've been getting decent reviews.
I'd love to read a review or two. MC has a point, you have to wonder just how much rudder wagging this device does, when it starts and when it stops.

For instance, if it does find a thermal and starts wagging the rudder just as you want to turn into the thermal, will it stop wagging or do you have to try to turn while it continues to wag?

Any links to reviews?

(edit) I read the instructions on the product website and found it requies a free channel, as it can be activated and de-activated from the transmitter. It is also programmable for two different methods of "wagging"; one applicable to faster gliders and one to slower gliders.

This product looks like it has promise and it's affordable also.

Anybody using one on their Radian?

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Old 07-10-2010, 06:59 PM
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Here are a couple threads about it over on RCGroups

http://www.rcgroups.com/forums/showt...ighlight=scout

http://www.rcgroups.com/forums/showt...ighlight=scout

http://www.rcgroups.com/forums/showt...ighlight=scout

Being able to toggle it on and off really makes it useful. Just turn it on when you're searching for life and off when you're climbing or thermaling.
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Old 07-10-2010, 07:14 PM
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Originally Posted by Belem View Post
Here are a couple threads about it over on RCGroups

http://www.rcgroups.com/forums/showt...ighlight=scout

http://www.rcgroups.com/forums/showt...ighlight=scout

http://www.rcgroups.com/forums/showt...ighlight=scout

Being able to toggle it on and off really makes it useful. Just turn it on when you're searching for life and off when you're climbing or thermaling.
Good links, Belem. I'll put one on order.

...The Bum
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Old 07-10-2010, 10:16 PM
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That does look promising. Thanks for the links.
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Old 08-09-2010, 05:04 PM
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Default just a question?

If there are no nat, ridges could a guy use the lift from large barn roofs or houses. just seems if you are looking for lift that would be a option.
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Old 08-09-2010, 05:15 PM
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Originally Posted by Belem View Post
Being able to toggle it on and off really makes it useful. Just turn it on when you're searching for life and off when you're climbing or thermaling.
You have to turn it off when launching and once you've found a thermal. It's no small wag! I haven't really had enough time with mine yet, but my first impression was I could see my Bird of Time react just as well to a thermal without it as with it. I really need to spend more time working with it, and try it in a few other gliders to really have some constructive feedback.

Originally Posted by kiddro2003 View Post
If there are no nat, ridges could a guy use the lift from large barn roofs or houses. just seems if you are looking for lift that would be a option.
Barns and houses don't influence the air up higher like large ridges, etc. You could probably find some slope lift with a 1.5M hand launch if it were light, and you were a good pilot. Any larger glider would have a heck of a time keeping in that lift, and would never get much altitude in my guestimation. You do much better catching thermals from around a barn with a dark roof, a paddock with exposed earth, etc. You just need something heating the air more from sun exposure.
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Old 08-19-2010, 08:58 AM
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SUCCESS! (sorta)
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Old 08-19-2010, 12:30 PM
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Congratulations!
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Old 08-20-2010, 08:28 PM
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Here is my Jessica 2M riding lift from house tops/ The street has about 8 homes with failrly good pitched roofs. The wind was from the E/SE. I launched up to about 300 feet with motor and then rode lift back and forth slighty on the windward side of the roofs. Of course, more wind usually produces more lift off the roof tops. I think the fact that the homes were fairly close together helps. and they are all aligned.





[media]http://www.youtube.com/watch?v=HxXMn5MU9-A[/media]
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Old 08-20-2010, 09:44 PM
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Interesting.
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