Clockwise or anticlockwise?

[evo62]

When you are in a thermal is one direction more efficient in generating lift then the other?

Is this like the water going down the drainpipe and depends on the hemisphere you live in?


Am I just overthinking this?

Clovus

[atmosteve]

It usually works both ways for me during an ascent. It might depend on where you hook up too and at what height. Basically, nah, don't overthink spiral direction in flight, thats a recipe to stuff it up. If you are going up, you are going up! If the rising colum has a small twist either way you will still work it in the long run, though it can help to sometimes change rotation to downwind if you run out of lift somewhere, like a loose figure eight. I'm not qualified to advise, but for what its worth please don't worry over it.
Steve.

[rogerflies]

I've seen vultures and other soaring birds circling in both directions, sometimes in the same thermal. Birds are going to do what's best, so I'd say there's no significant advantage in one direction over the other.

There's no way for me to separate the variables well enough to make a call as to flying a sailplane.

There are many more important things to think about.

Roger

[Guz]

Just fly which ever way you can fly the smoothest.

I don't know why, but I can make silky smooth coordinated left turns, but a right turn, AAAaaaarrrrgggghhhh!!! Tip stalls, sliding, porpoising, stalling, you name it, right turns suck :mad: (it isn't the plane, it's me).

Someone told me that for some reason, if you are right handed, it's normal to be able to do smooth left turns, crappy right turns in R/C. Not sure I believe it, but Hey! Made me feel better :p

So, when I find lift I work it with a left hand turn, simple as that.

I am practicing right turns, after I get some altitude, no days. It's gonna take awhile, but I hope by the end of the 2009, I'll perfect it ;)

[Bob J]

When you are in a thermal is one direction more efficient in generating lift then the other?

Is this like the water going down the drainpipe and depends on the hemisphere you live in?


Am I just overthinking this?

Clovus

The direction water rotates going down a drainpipe (or the direction water rotates when the toilet is flushed) has nothing to do with the hemisphere in which you reside.

When circling in a thermal, I feel more comfortable moving the stick to the right than to the left so I normally fly a clockwise circle. Do whatever you are most comfortable with. When entering a thermal in which others are circling, I follow their lead.

Regards,
Bob J.

[fnev]

The direction water rotates going down a drainpipe (or the direction water rotates when the toilet is flushed) has noting to do with the hemisphere in which you reside.

Sorry: WRONG!!! And between the tropics goes both ways as the precession is very weak or non existant.

[schrederman]

Actually, in a toilet, the water jets in the rim of the toilet are directed one way or the other, and the direction of the water swirl has nothing to do with the Coriolis Effect. Thermals, in both hemispheres, are not effected, either. As the air rises, the lowered pressure beneath causes surrounding air to rush in. As it does, it encounters obstructions or prevailing wind. That causes one side of the inflow rush to be stronger than all others and as it meets under the thermal, it swirls in the direction of the stronger inflow from the center of the lift. I've seen 2 dust devils in the same field carrying dust and debris aloft, spinning in opposite directions. This question is as old as the down wind turn myth. Don't over think it. The effect you're thinking of works for large weather systems and some ocean currents, but generally is too weak to effect anything else.

Jack Womack

[WimH]

Just fly which ever way you can fly the smoothest.

I don't know why, but I can make silky smooth coordinated left turns, but a right turn, AAAaaaarrrrgggghhhh!!! Tip stalls, sliding, porpoising, stalling, you name it, right turns suck :mad: (it isn't the plane, it's me).

Someone told me that for some reason, if you are right handed, it's normal to be able to do smooth left turns, crappy right turns in R/C. Not sure I believe it, but Hey! Made me feel better :p

So, when I find lift I work it with a left hand turn, simple as that.

I am practicing right turns, after I get some altitude, no days. It's gonna take awhile, but I hope by the end of the 2009, I'll perfect it ;)

Same here, but for some reason I get the impression my plane goes up faster in a thermal when I do right turns :confused:

[Guz]

Same here, but for some reason I get the impression my plane goes up faster in a thermal when I do right turns :confused:
That's all it is, impression :p

A fellow flier at my field can do silky smooth right turns, sometimes we hit the same thermal. I do left turns, he does right turns (dangerous blender I know, but we are used to it), we both go up at roughly the same rate.

Sometimes, we will both do either right or left turns, it's the person that can keep it smooth that win's out :D

[evo62]

All the above makes sense. I am just coming to grips with thermals - new to gliders and was just wondering as one direction seemed worse then the other.... more then likely it is pilot error... I guess... At least I'm not alone !!

Cheers
Clovus

[IBWALT]

Actually, in a toilet, the water jets in the rim of the toilet are directed one way or the other, and the direction of the water swirl has nothing to do with the Coureolis Effect(sp.). Thermals, in both hemispheres, are not effected, either. As the air rises, the lowered pressure beneath causes surrounding air to rush in. As it does, it encounters obstructions or prevailing wind. That causes one side of the inflow rush to be stronger than all others and as it meets under the thermal, it swirls in the direction of the stronger inflow from the center of the lift. I've seen 2 dust devils in the same field carrying dust and debris aloft, spinning in opposite directions. This question is as old as the down wind turn myth. Don't over think it. The effect you're thinking of works for large weather systems and some ocean currents, but generally is too weak to effect anything else.

Jack Womack

Thanks Jack, for letting the cat out of the bag. :mad: This will cost me a bundle in bets that I would have made and fun I could have had.

Now with that said I will say that I do most of my turns to the left but if a thermal does not seem to be taking off or I'm not having much luck I will try turning in the opposite direction and sometimes it works out.

Walt

[schrederman]

Quote>This will cost me a bundle in bets<Quote

I seem to remember taking lots of dollar bills from you when you'd say... "Betcha a buck you can't thermal out in 3 throws." Sorry Walt, I ain't buyin' it! :p :D

Jack

[Batmanwpg]

The direction water rotates going down a drainpipe (or the direction water rotates when the toilet is flushed) has noting to do with the hemisphere in which you reside.

Sorry: WRONG!!! And between the tropics goes both ways as the precession is very weak or non existant.


You need to watch Discovery Channel! :rolleyes:

[Tappet]

I generally like to turn in a straight line.

[Batmanwpg]

I generally like to turn in a straight line.


Another member of the "Flat Earth Society"??? :D

[Phil Barnes]

http://www.rcgroups.com/forums/showthread.php?p=4363037&highlight=coriolis#post4363037

For more just search the word "coriolis" in the Sailplane or thermal forums.

[schrederman]

Thanks for the spelling correction... to be honest, this one's been around the block so many times I almost didn't care enough to go back and correct it... sorry.

Jack

[lincoln]

I often get the impression that one direction or the other is favored in a particular thermal. One's airspeed is similar, but if you're going against the spin, then you go around the circle slower and you don't need as much bank. Going the other way you're going around the circle much faster and you will need a bit more bank, and probably a tad more airspeed because of the bank. I haven't done careful studies of this, but it makes sense. Often I can't decide which is best and in that case maybe it's not spinning very much.

[evo62]

I guess you're always going to get noobies asking it...

[rogerflies]

"...but if you're going against the spin, then you go around the circle slower and you don't need as much bank."

No. Bank angle depends on airspeed, and you'd (hopefully) have the same airspeed either way.

Roger

[fnev]

Well, here we go:
http://www.ems.psu.edu/~fraser/Bad/BadFAQ/BadCoriolisFAQ.html

Roger you are 100% right. This is back to the same "down wind turn BS"!!!

Now, just to add fuel to the fire... If I am on a steep bank angle, is the air velocity of the (rotating) thermal the same at the "down" wing tip and at the "up" wing tip??? IF not, it could have an influence on tip stall... :D :D :D

[schrederman]

No. If you're banked at 90 degrees, the down wing and the up wing have the same airspeed. Otherwise, the down wing will be flying slower. the shallower the bank angle for the same turn radius, the more pronounced the difference will be.

Chew on that one for a while...:D

Jack

[fnev]

OK, sorry, I was not careful enough in my wording. But I am sure you understand what I am getting at… The air speed of the rotating flow is not constant across the thermal from core to outside and bottom to top. Now because your wing tips in a (balanced) turn do not travel at the same speed… ;)

[Libelle201B]

"the shallower the bank angle for the same turn radius, the more pronounced the difference will be".

Chew on that one for a while...:D

Jack Jack, maybe I am misreading your statement, but one cannot change bank angles while trying to maintain a particular radius. Your bank angle and the speed required to maintain that bank angle will determine the turn radius. :)

[Skycruiser]

The swirl of water leaving a tub or the swirl of rising air in a thermal is caused by conservation of angular momentum. Just as a spinning dancer spins faster if she pulls her arms in, if the air rushing in to a thermal has any angular movement at all, that angular movement will accelerate as the mass of air moves towards the center of the thermal. So it's purely random as to whether a thermal turns CW or CCW. As Schederman says, Coriolis effect and precession are too weak to have much effect on as small a body as a thermal.

Personally I just turn in the direction I was going when i turned into the lift.

Nick

[lincoln]

"...but if you're going against the spin, then you go around the circle slower and you don't need as much bank."

No. Bank angle depends on airspeed, and you'd (hopefully) have the same airspeed either way.

Roger
I'm sorry, but that's incorrect. Airspeed in this case gives you a rotating frame of reference, and that's a big can of worms. Your answer would hold if the air wasn't rotating, but it is. Bank angle depends on acceleration of the glider, not of the air. Remember that in some of our troublesome previous discussions, we all assumed the air had a constant velocity. That's not true in this example.

Think carefully about this. To get rid of that topic which should never be named, let's assume that the thermal is not drifting relative to the ground. If you need to maintain 25 fps for a 30 degree bank, your turning radius would be 39 feet and you're accelerating 1/2 g (16fps^2) toward the center. It would take you 10 seconds to make a turn. Just to keep things simple, let's assume you can keep the 25 fps airspeed for any of these turns. In real life, it's more complicated. Anyway, let's assume that you're perfectly centered in the thermal and that at a 39 foot radius, the air's tangential velocity is 5 fps. If we're flying upwind, speed made good around a circle is now 20 fps. So, that means it takes 12.25 seconds. If you fly a 39 foot radius circle in 12.25 seconds, acceleration toward the center is 0.32G (10.3fps^2). You only need a 19 degree bank to do that. If you're going downwind (i.e. turning in same direction as rotation of the thermal), then your making 30fps. Acceleration toward the center is now .72g and you need a 46 degree bank.

Of course, if you maintain the same margin above stall, you can fly a lot slower with the shallower bank, which means you have even less acceleration toward the middle and can fly even a bit slower because of less bank. And vice versa.

If you're in a sealed box, you can't tell if you're steadily accelerating or in a gravity field, but you can tell if you're rotating.

I'm not sure I'm getting my point across very well, but I'm pretty sure of the physics. If we could rent that spinning room in the Space Needle, we could demonstrate this pretty well. If you could find an empty, but moving, merry go round, it would also work.

Here's another way to think about it. If an object moves through the same path as another object, it doesn't matter what's making it do the path (except gravity, I suppose), the acceleration is a function of the path and speed. If you are on the back of a motorcycle that is directly under the glider at all times (let's assume you're on the salt flats and the ground is flat), then you're going around the circle 50% faster when you're going the downwind way. If you go around a circle 50% faster on a motorbike, you have to lean in more. In fact, the lean angle will be about the same as a cleanly flown turn by our glider. (It would be exactly the same if it weren't for the finite width of the motorcycle's tires, which require a bit more bank because the point of contact moves inward.)

[schrederman]

Libelle, I agree, but a 1-26 will circle tighter for the same bank angle than an ASW-20... And my Yardbird will circle tighter that most moldies for the same bank angle.

That's what I was referring to...

Jack

[lincoln]

Jack, maybe I am misreading your statement, but one cannot change bank angles while trying to maintain a particular radius. Your bank angle and the speed required to maintain that bank angle will determine the turn radius. :)
Sure you can. Just go faster or slower and change the elevator setting slightly. Unless you are trying to hold the minimum airspeed possible with that bank angle, which means that you are already flying the tightest possible radius. If you're flying a Cessna, it's possible to fly a 10 degree bank turn at, say 70 knots. You don't have to slow down to do it. Otherwise, in the limiting case, you couldn't fly above stall speed when level.

[schrederman]

Well, I'll tell you one thing... I've flown into dust devils... yes intentionally... but I always wanted to be turning against the spin direction and carrying more than a touch of extra airspeed. I have gotten away when I should have been turning final on a farmer's cotton field... :o ... rather turbulent and heart-pounding... :eek: ... but WHAT A :censored: RUSH! :eek: :D :eek: :D

Since coming to New Mexico, twice I have had models in dust devils and had NO control. They were literally being blown skyward like leaves. I was finally able to get out with full spoilers and half down elevator. Of course, carbon spars are nice in that situation. :D

Jack

[lincoln]

http://imgs.xkcd.com/comics/centrifugal_force.png

[glidermang]

I learned this in full-scale soaring: circle the same way as the others - avoiding collisions is really what it's all about. Seemed like common courtesy to me.

In rc soaring, I do the same thing, even when circling with birds. Still seems like courtesy to me. Of course, my flying is not too good, so if there's a benefit to circling one way versus the other, I'd never see it.

I'm a flight test engineer, and here's the story on turn rate, airspeed and bank angle: Any two decide the third. Here's the story on bank angle and load factor (G-force): they are two expressions of the same thing. Sorry guys, I've done the math, and analyzed the data and it was just like in the text books. By the way, a 60-degree bank in a steady turn is 2 G's, regardless of airspeed, or size of airplane.

I, too, flew a 1-26 in the same thermals as ASW's and Nimbus's and the others, and I, too, had a smaller turn radius - flying at a slower airspeed. My 1-26 thermalled best at 47-50 mph. Most of the glass slippers flew at around 60-70.

Yours, Greg

[Libelle201B]

Sure you can. Just go faster or slower and change the elevator setting slightly. Unless you are trying to hold the minimum airspeed possible with that bank angle, which means that you are already flying the tightest possible radius. If you're flying a Cessna, it's possible to fly a 10 degree bank turn at, say 70 knots. You don't have to slow down to do it. Otherwise, in the limiting case, you couldn't fly above stall speed when level. And if you change the bank angle to 40 degrees at 70 kts in your Cessna the radius will no longer be the same. I think that is the point I was trying to make. :)

[lincoln]

You've done the math, but I think you are forgetting the little asterisk that goes to a note specifying that the flow is irrotational. I think sometimes even the textbooks omit this, but I had a prof who never did. He'd always start a discussion about stuff like this with maybe 6 or 8 qualifiers. At that level, which wasn't so advanced, these might include inviscid, irrotational, steady, incompressible yada yada yada....

Of course in steady level flight a bank of 60 degrees means 2 gees.

If the turn rate and radius are the same, then the bank needs to be as well. But if the thermal is rotating, the air speed could be different. And if the air speed is the same, then the turn rate will be different depending on whether you are going with or against the thermal. And if the turn rate is different, but the radius is the same, the bank angle will be different.


If you know the flight path and speed, as measured from a Newtonian frame of reference*, then you can calculate the acceleration without reference to the airspeed. If the data are fictional, there's no guarantee that you CAN fly it that way, but if you fly it that way, you will get the calculated acceleration.

*No rotation or acceleration. The Earth is NOT a Newtonian frame of reference, although it's usually close enough for us.
I learned this in full-scale soaring: circle the same way as the others - avoiding collisions is really what it's all about. Seemed like common courtesy to me.

In rc soaring, I do the same thing, even when circling with birds. Still seems like courtesy to me. Of course, my flying is not too good, so if there's a benefit to circling one way versus the other, I'd never see it.

I'm a flight test engineer, and here's the story on turn rate, airspeed and bank angle: Any two decide the third. Here's the story on bank angle and load factor (G-force): they are two expressions of the same thing. Sorry guys, I've done the math, and analyzed the data and it was just like in the text books. By the way, a 60-degree bank in a steady turn is 2 G's, regardless of airspeed, or size of airplane.

I, too, flew a 1-26 in the same thermals as ASW's and Nimbus's and the others, and I, too, had a smaller turn radius - flying at a slower airspeed. My 1-26 thermalled best at 47-50 mph. Most of the glass slippers flew at around 60-70.

Yours, Greg

[jp.electrik]

Wow, who knew I would get such quality education. Found it very interesting, thanks to the intelligentsia.

In regards to the original question: I did some reading and found I had some misinformation... The Coriolis force is definitely a reality, but only one in many factors involved in determining which way a body of air may spin. The Coriolis force pushes to the right in the North and the left in he Southern Hemispheres respectively. Sounds like an answer. :) Turns out it's not that easy. :(
Tropical Cyclones, more commonly called Hurricanes or Typhoons depending on their location, spin in opposite directions to the Coriolis force. This is due to the atmospheric pressures involved which are greater than the relatively weak effect of Coriolis. Furthermore, water going down the drain does not always turn the same way in any hemisphere. Forces described earlier in this thread, "conservation of angular momentum".
This was news to me. I, like so many had heard that water, air and soaring birds, rotated in the opposite direction south of the equator! :o
This backs up the practical experience discussed by you experienced thermophiles. ie:Thermals spinning in both directions at the same location on the same day!

Then there's the whole other can of worms; which is better, to fly with the rotation or against? :rolleyes:

I would think better lift would be obtained against or into the rotation, as it would be into the wind... But than I thought I knew something about the Coriolis Effect. Turns out I didn't even have the name right, it's Force not Effect!
I'll shutup now :confused:

[rogerflies]

"I would think better lift would be obtained against or into the rotation, as it would be into the wind."

"Into the wind" only matters with respect to the ground. It's that old downwind turn thing again. :D

Roger

[Jurgen]

From a respectfully glider pilot David Hobby:
If you seem to get irregular or difficult handling while circle thermalling , change direction, you might get it smoother.
This one simple sentence skips all of the rotating dabahabba hokuspokus, and boils down to what you can practically apply and benefit from rotating thermals.
Cheers, Jurgen.

[Bob J]

Cumulus clouds typically form when warm air rises and reaches a level of comparatively cool air, where the moisture in the air condenses. Having never observed a cumulus cloud that displayed rotational (clockwise or counterclockwise) motion, I conclude that the thermal that eventually led to the formation of the cloud does not rotate.

Regards,
Bob J.

[schrederman]

Bob J.

Pray you never do see a cu-nim that's rotating... they're called mezo-cyclones, or... tornadoes... :eek:

However, having been up in the frog hair at cloud base, I can tell you that there is a lot of localized rotation and other turbulence associated with normal, fair-weather cumulus clouds.

Jack

[rogerflies]

Ditto on that point. I used to fly my very stable 42% Spacewalker into low cumulus clouds. Flying hands-off, it would often come out several seconds later in an unusual attitude, sometimes even inverted. It was completely unpredictable.

Roger

[lincoln]

"I would think better lift would be obtained against or into the rotation, as it would be into the wind."

"Into the wind" only matters with respect to the ground. It's that old (deleted name of discussion which must never be named) thing again. :D

Roger
No, it's not. As I said, if you're in Einstein's (or even Newton's) elevator, you may not be able to tell how fast you're going, or in what direction, but you sure can tell if you're turning. If you go with the rotation of the thermal, you will complete your turns much faster than if you go the other way. This is reflected in the bank angle necessary, etc. If I understand what you're saying, you're correct about the discussion which must never be named, but this is different.

When looking at the unnameable, the air is a decent frame of reference because it's not accelerating or rotating. However, in a thermal, it IS rotating, which means acceleration. That makes it a lousy frame of reference.

I despair of explaining this matter. Not even the XKCD cartoon worked. Perhaps someone else can do it. Perhaps we can get one of the luminaries who are believed without question to chime in, although to tell the truth I can only really think of one in this context. Maybe instead I should contact a medium to get the spirit of Prandtl to speak.

[upstart]

There's an apocryphal story that Dick Schreder paid a guy one summer to determine the rotation of every thermal that blithered through his airport (or was it in Puerto Rico... ) I don't recall whether he did this by pitching flour or wheat chaff into the thermal, but he did it.

To Schreder's dissappointment about half went clockwise, the other half went the other way.

Centerpunching a dust devil in a lightly loaded sailplane is a memorable experience. It's as if a giant terrier has grabbed the airplane and is playing tug-of-sock with it, while you on the inside are left wondering what the stick is supposed to do, because clearly it has no effect on the flight controls.

[edit: the more I think about it, it seems he paid a man who worked in a sugar cane plantation to note the direction of each "dust devil" - noted by bits of cane deritrus]

[jp.electrik]

Now that so many of you are on topic. I was wondering.
Is turning faster in a thermal necessarily a good thing? Yes you complete your turn faster but does the steeper bank result in less lift? Which brings up my other question: Do you thermal types ever use more rudder/ less aileron to keep the wing more perpendicular to the direction of the thermal resulting in more lift? :confused: I'm aware this would result in yaw but...?
If this question is to rudimentary I'm sure you will refer me to the appropriate source (with little admonition hopefully). :o

[rogerflies]

So, a change in centrifugal/centripetal forces because of the change in rotation speed with respect to the ground will dictate a change in bank angle and airspeed to maintain the turn radius.

Yeah, I can see that, but it's making my head hurt to think about it.

Roger

[jp.electrik]

So, a change in centrifugal/centripetal forces because of the change in rotation speed with respect to the ground will dictate a change in bank angle and airspeed to maintain the turn radius.

Yeah, I can see that, but it's making my head hurt to think about it.

Roger

Ya, but does steeper bank angle result in reduced lift?

[upstart]

Ya, but does steeper bank angle result in reduced lift?
I think you'll find it results in an increased sink rate.

However, not all thermals need to be dealt with the same way, and they do change characteristics with altitude as well.

A pilot from out west will get used to turning 2g in a thermal because to be in any less of a circle won't keep you in the core. The good stuff can be awfully rough and tight. But it goes up with authority. You hang on and hope nothing breaks as you ride it up (ok, a little over the top). A little extra speed isn't bad, because the stall recovery is more immediate, plus roll authority is a little better. When it's rough, these are useful allies.

His eastern cousin, OTOH, gets used to noodling around at 1kt over stall - you can do this because it isn't so awfully rough - 20-30 degrees of bank and just burbling around a big fluffy thing going up at 250 fpm. Rack it up to 45 or 50 degrees and fall out through the middle of it.

They're different, and that's part of the fun, isn't it?

But don't anthropomorphize them - they hate that!

[edit: with a round tailed 1-26 you could sometimes, if you wore thin soled shoes and kept a very light touch on the rudder pedals, get a sense of which way the thing was going to rotate. Whether this sense was accurate or not I have no idea. Guys who fly full scale contests used to default to thermalling to the left, because that's what you had to do within 3 miles of a turnpoint or the airport. Guys who didn't would turn right more often, because that's the direction you peel off when you let go of the towplane. ]

[lincoln]

So, a change in centrifugal/centripetal forces because of the change in rotation speed with respect to the ground will dictate a change in bank angle and airspeed to maintain the turn radius.

Yeah, I can see that, but it's making my head hurt to think about it.

Roger
Well, actually, at least in the Newtonian world, the rotation is an absolute thing, it doesn't matter if the ground is there or not. The same principles would apply if you were flying in Jupiter's Great Red Spot (I seem to recall there isn't any ground to refer to on Jupiter, although I could be wrong. Maybe there's metallic hydrogen at the core or something? I'm weak on planetary science.) However, I think you've got it.

[jp.electrik]

Do you thermal types ever use more rudder/ less aileron to keep the wing more perpendicular to the direction of the thermal resulting in more lift? :confused: I'm aware this would result in yaw but...?
If this question is to rudimentary I'm sure you will refer me to the appropriate source (with little admonition hopefully). :o

I am new to soaring, my flying experiance is with 3 channel ellivon setup. I find myself inclined not o use the rudder unless I force myself. I see a fair ammount of gliders with RET controls so the abouve question occured to me. If the answer is yes I need to start intigrating my turns by utilizing rudder?

[rogerflies]

From what I've seen, most power plane pilots use the rudder only for steering on the ground.

On the other hand, I've never seen a full-scale pilot fly a model plane without using the rudder. Using it makes the turns smoother and more graceful. Being able to cross-control the aileron and rudder makes landing in crosswinds easier and more realistic. The same skill works for one-wheel-on-the-ground fly-bys, and forward slips are handy for getting rid of altitude without gaining excessive airspeed.

Understanding and using the rudder adds a lot to the fun of flying.

Roger

[Phil Barnes]

The most efficient turns are coordinated turns. A coordinated turn coordinates the use of aielron and rudder controls such that the nose of the model is always pointed in the direction that the model is traveling through the air. Flying with coordinated turns will produce the slowest sink rate through the air air mass. See this link:

http://www.polecataero.com/handlaunchu/using-the-rudder-in-thermal-flying

I'm not sure I understand your original question about keeping the wings perpendicular to the thermal. My best guess is that you are talking about doing what some guys refer to as "flat turns" where they try to keep the wings more parallel to the ground and attempt to make the model turn with rudder control while holding the bank angle lower with opposite aileron control. That is a very bad technique since it produces uncoordinated turns.

http://www.rcgroups.com/forums/showthread.php?p=7897589&highlight=flat+turns#post7897589

http://www.rcgroups.com/forums/showthread.php?p=10253592&highlight=flat+turns#post10253592

[evo62]

Phil,

My (feeble -noobie) understanding based on observation was when I bank the plane over more then 20-30 degrees perhaps, it loses altitude. Does that mean the lift from the thermal is greater then the loss of altitude from banking the model over?

I guess this is something you become better able to judge as you get more experience?

Clovus

[Phil Barnes]

The steeper the bank angle, the faster the glider will sink through the air mass while turning. If the air mass is rising faster than the glider's sink rate then the glider will still climb relative to the ground. I think you already knew all of that. I've just re-stated it in a different way.

Some thermals are very small but the lift is strong enough to make up for the faster sink rate that comes along with the tight turn needed to stay in the thermal.

[Libelle201B]

Phil,

My (feeble -noobie) understanding based on observation was when I bank the plane over more then 20-30 degrees perhaps, it loses altitude. Does that mean the lift from the thermal is greater then the loss of altitude from banking the model over?

I guess this is something you become better able to judge as you get more experience?

Clovus Yes, it will take time but you will learn as you go along, as all of us have. Maybe that 20-30 degree bank was not enough bank to stay in the thermal, or maybe depending on your altitude it was, you just wern't in the core of the thermal. Maybe a simple rule to follow is that if you arn't climbing after several turns, you arn't in lift. At that point you will have to enter a search mode to relocate the thermal, generaly down wind. Once re-connected with the thermal use any bank angle it takes to climb, shallow or steep, and this will vary through out the climb. If at some point you are not climbing at all no matter what, you have missed the thermal and must go in search for another :)

[upstart]

In full scale (and I'm sorry to throw that back into this), they talk about theory too, but in the end it comes down to this: "you do what you need to do, and fly the way you need to fly to make the most of the lift you have." They do have the advantage of flying with other airplanes in a thermal, so you can gauge how well you're doing comparatively, but in the end it's the result that matters.
IMO that comes with practice.

[evo62]

It's a good thing the practice is fun!

[recep]

Hi I have done a search for the rotation and possible effects on soaring on google lately. Here are links that helped me to figure out something.
http://www.soartech-aero.com/Thermals.htm

in the link below there is a comparision between strategies of a falcon and human soaring. Mostly it is about the MacCready's "speed to fly" theory.

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2393768

this article is interesting to read but too much science for me but then I watched the test subject's videos. A falcon with a gps unit that records falcon's flight and reanimation of that flight showing the vertical change in red to blue colors. These videos helped me to understand thermals and you will also see lots of clockwise and counter clockwise turns.

http://www.pnas.org/content/105/11/4139/suppl/DC1
the 3 movie links inthe middle of the page.