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Old Jun 15, 2012, 11:45 PM
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Rudder Vs. Aileron

As my first post on these forums and as a newbie into RC planes I have to ask an odd question. I have an AXN floater, stock setup and I have taught myself to fly with only aileron and elevator. I have ordered a 3 channel plane to kick around for just fun ( the HK atom mini glider) and I have to ask, for general flight, what will be the difference in flight? Will I be able to fight winds as well? how does the craft self right without ailerons? is it more difficult to maneuver?

Also, another question. With a 4 channel plane, is it possible to take sharper turns with both rudder and aileron without dropping a wing tip? In the park I fly, it's about 300 meters long and I'd like to be able to fly within sight but sometimes winds prevent me from turning immediately.

And one more question and it may be an obvious thing but how can I tell how to trim my plane? I find that it tips to the right and I trim the ailerons and the rudder to the left separately and find that it then tips to the left, even with minor adjustment. is there a good way to tell if the rudder is out of alignment or the aileron?

I thank you in advance for any help.
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Old Jun 16, 2012, 02:20 AM
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Aileron/elevator gives you a lot more control than rudder/elevator.

You can turn sharper by combing rudder and aileron in the same direction, but not when using opposite aileron to keep the plane flat--thats the slowest, least efficent way of turning.
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Old Jun 16, 2012, 02:38 AM
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Hi, you will hear from others, I've never flown rc and the only experience I've had was flying 152's, 172's, 182's, & a piper Cherokee. All real planes.
I'm just stating that they all trim the same. Level & straight.
God, I miss flying, I'm building my 1st plane & hope I can keep it in the air. I'm being very difficult because I want a 4ch/5 withflaps trainer. I'll have to build it.
You sound like you're ready to move on. If your going to buy get a 55" Cessna, but I believe that you will learn the most from building a foamey at your level. There's tons of free plans here. Pick one build/fly it! Then you will understand flying and know what you want & how to achieve it.
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Old Jun 16, 2012, 10:10 AM
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Yes, it's the same in R/C that all trims are applied for flying level and straight, as winds and throttle amounts you applied, and the locations of CG will affect the attitudes of your R/C plane in the air, while wind speeds affect high wing (with flat bottom airfoil) R/C planes way much more than real planes.

Chen
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Old Jun 16, 2012, 12:04 PM
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Originally Posted by twn Chen View Post
Yes, it's the same in R/C that all trims are applied for flying level and straight, as winds and throttle amounts you applied, and the locations of CG will affect the attitudes of your R/C plane in the air, while wind speeds affect high wing (with flat bottom airfoil) R/C planes way much more than real planes.

Chen
Wind has no affect on aerodynamics, it only affects landing take-off and navigation.
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Old Jun 16, 2012, 12:45 PM
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Originally Posted by SMackaay View Post
As my first post on these forums and as a newbie into RC planes I have to ask an odd question. I have an AXN floater, stock setup and I have taught myself to fly with only aileron and elevator. I have ordered a 3 channel plane to kick around for just fun ( the HK atom mini glider) and I have to ask, for general flight, what will be the difference in flight? Will I be able to fight winds as well? how does the craft self right without ailerons? is it more difficult to maneuver?

A rudder controlled plane, (no ailerons), will have wing dihedral, (the wings will be angled up each side slightly). Dihedral also acts as an natural stabilizer and returns the model to wings level after a turn.

Also, another question. With a 4 channel plane, is it possible to take sharper turns with both rudder and aileron without dropping a wing tip? In the park I fly, it's about 300 meters long and I'd like to be able to fly within sight but sometimes winds prevent me from turning immediately.

Sharper turns ?, not really, more level turns yes. Ailerons are more for bank and yank turns, coordinated turns using rudder aileron and elevator can look smoother.

And one more question and it may be an obvious thing but how can I tell how to trim my plane? I find that it tips to the right and I trim the ailerons and the rudder to the left separately and find that it then tips to the left, even with minor adjustment. is there a good way to tell if the rudder is out of alignment or the aileron?

In the same way that you check and adjust a plane for the CG balance, (longitudinal balance), you should check the plane for 'lateral' balance, to see if one wing is slightly heavier than the other, (the plane tips towards the heavier wing when held by the prop and tail). The model should look straight when viewed from the nose and tail, (no banana shape). The fin and rudder should be perfectly in line with the fuselage center line. The wings and horizontal stab should be warp and twist free and absolutely identical each side.

I thank you in advance for any help.
Also check for differences in flight between power on and power off, gliding. Climb high and power off then glide and trim for a straight slightly nose down glide. Then when you power up again record what trim changes are required, as the motor thrust line may need adjustment.

Speed and height is controlled by throttle, level flight at different speeds is controlled by elevator trim, (just as in full sized aircraft). The elevator stick is often the thing that causes more trouble for beginners. Flying in too much wind is usually the destroyer of models.
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Old Jun 16, 2012, 01:25 PM
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The largest effect on turning radius, whether the turn is controlled by rudder or aileron, is speed. The faster an airplane is flying, the greater its turning radius. It has something to do with inertia.

Larry
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Old Jun 16, 2012, 03:26 PM
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I'm a rank beginner myself (have been one for a number of years) please correct me if I mislead since most of my aviation experience has been from full scale aircraft.

I think that the 3 channel aileron vs. rudder control would depend on the design of the aircraft. A slow high wing with a lot of dihedral would steer nicely with rudder. The dihedral tends to make the plane bank by itself without any aileron whereas a flatter wing design would tend more to just yaw. The same slow airplane turned by ailerons alone would tend to have more adverse yaw, which is the tendency for the drag of the ailerons to yaw the nose opposite to the direction of the turn. A faster airplane needs less aileron deflection to bank, therefore less adverse yaw. With rudder alone, you can only bank a certan amount however which limits your turn radius but with a slow airplane you can turn in a pretty small area without a huge amount of bank.

Of course, while talking about control and beginners, the more control one has, the greater capacity one has to overcontrol. I found that out when I bought my first RC airplane which was a "trainer" which the previous owner had modified by removing most of the dihedral. Sure enough, the first time I flew it it did exactly what I told it to do, which was a split-s into a tree when I got totally disoriented. You will find a rudder/elevator controlled plane will not be quite as willing to go inverted. I got a Hobbyzone Champ for an early Father's Day present a few days ago and was amazed how nicely and realistically that plane flew with just elevator and rudder. I highly recommend it.

While wind speed has no effect on aerodynamics, wind speed can certainly cause wind shear and turbulence. Different airplane designs handle turbulence differently. The greater the wing loading (lbs. per square ft. of wing area) the less turbulence is felt, which is why 747's and F-16's aren't going to be thrown around near as much as Champs and Cubs. The difference in wing loading of a model vs. full scale is significant. I did the math and calculated that a full scale Champ has a wing loading of 7 lb/sq.ft. while my model has a wing loading of .18 lb/sq.ft.....Louis
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Old Jun 16, 2012, 03:55 PM
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While wind speed has no effect on aerodynamics, wind speed can certainly cause wind shear and turbulence.
Quite correct. You'll be surprised at just how many seasoned RC flyers don't understand the bit in bold.
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Old Jun 16, 2012, 05:04 PM
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Thanks for the great answers everyone! when my HK atom comes, I think it'll be a smooth flight.
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Old Jun 17, 2012, 10:07 PM
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Wind has no affect on aerodynamics, it only affects landing take-off and navigation.
Yes, the aerodynamics are the same but the wind speed does add the response rate on all control surfaces when flying into strong up winds. The control surfaces become more responsive when airspeed becomes higher. And I was trying to say up wind will give more lift on a high wing plane that is with flat bottom wing airfoil.

Chen
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Old Jun 17, 2012, 11:04 PM
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Yes, the aerodynamics are the same but the wind speed does add the response rate on all control surfaces when flying into strong up winds.
No it doesn't, unless you've increased your airspeed in an effort to keep groundspeed constant. But that has nothing to do with the wind itself.

Quote:
The control surfaces become more responsive when airspeed becomes higher.
Absolutely correct.

Quote:
And I was trying to say up wind will give more lift on a high wing plane that is with flat bottom wing airfoil.
It's not the act of flying upwind that adds lift. Lift is increased when airspeed is increased. I can fly upwind, downwind, or across the wind's path and my lift in level flight will always be proportional to my airspeed, though my groundspeed will change significantly.
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Old Jun 18, 2012, 12:03 AM
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No it doesn't, unless you've increased your airspeed in an effort to keep groundspeed constant. But that has nothing to do with the wind itself.



Absolutely correct.



It's not the act of flying upwind that adds lift. Lift is increased when airspeed is increased. I can fly upwind, downwind, or across the wind's path and my lift in level flight will always be proportional to my airspeed, though my groundspeed will change significantly.
What CH said.
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Old Jun 18, 2012, 12:49 AM
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An aircraft flying in the wind is like Einstein's frames of reference in relativity theory. The ground is one frame of reference, the moving air mass another. Ground speed != perceived airspeed by the plane.

I saw a $15,000 turbine crash today because the pilot throttled back too much on a downwind leg judging his airspeed speed by ground speed.
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Old Jun 18, 2012, 12:55 AM
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No it doesn't, unless you've increased your airspeed in an effort to keep groundspeed constant. But that has nothing to do with the wind itself.

It's not the act of flying upwind that adds lift. Lift is increased when airspeed is increased. I can fly upwind, downwind, or across the wind's path and my lift in level flight will always be proportional to my airspeed, though my groundspeed will change significantly.
Probably you'd have to fly a high wing trainer upwind, cross wind and downwind to see how wind speed affects the lift on its wing. It's always windy here during winter and fall in Taiwan, I did teach many beginners flying high wing trainers over the recent two years. Surely we all experienced this fact. And we all knew the difference between airspeed and ground speed, and how wind speed added up the airspeed when flying into upwind. I did show them how to fly in upwinds and always stayed upwinds when it was very windy.

Chen
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Old Jun 18, 2012, 02:21 AM
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Interesting discussion.

I've even seen reasonably experienced full scale pilots who weren't able to fully seperate their frame of reference from the ground to the air. I heard one pilot state that the plane he was flying had an airframe with a lot of drag so that the tailwind was "pushing harder" on it than on more streamlined aircraft.

People sometimes can't get their minds around the fact that the airplane is totally suspended in the body of air and (disregarding turbulence) is not affected in the least by what that air mass is doing relative to the ground.

The legendary dangers of the dreaded downwind turn still seem to persist. Just watch the instruments and horizon (full scale) without regard to what the ground is doing under you while turning and the plane won't do anything different whether the wind is calm or blowing 100kts.

Like mentioned above, whether in the cockpit or outside of it, if you judge your airspeed by the groundspeed while turning downwind you can get into trouble. It's trickier to monitor the airspeed when you don't have the luxury of sitting in the cockpit with the airspeed indicator in front of you.
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Old Jun 18, 2012, 03:19 AM
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Very true, I did have many tests flying Cub and Cessna 172 on Microsoft Flight Simulator 2007 by setting cross wind speed at 40kts, also it varies per 15 minutes, trying to take off in such cross wind, fly landing patterns and land on runway per its center line. What a challenge !
One of my buddies lost his FPV plane in windy weather 5 months ago, it was with the advanced OSD and auto return function but these did not help it return to the field after flying a long downwind leg.

Chen
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Old Jun 18, 2012, 06:48 AM View Post
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Old Jun 18, 2012, 08:17 AM
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...just as a noob's observation, I'd think of it like swimming in a pool on the deck of a cruise liner. The ships forward or reverse motion would not normally alter the time you took to swim a lap.. but the ship's rolling and pitching might effect your progress somewhat, if of sufficient magnitude.
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Old Jun 18, 2012, 11:52 AM
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Very true, I did have many tests flying Cub and Cessna 172 on Microsoft Flight Simulator 2007 by setting cross wind speed at 40kts, also it varies per 15 minutes, trying to take off in such cross wind, fly landing patterns and land on runway per its center line.
The above is purely the wind affecting landing, take-off and navigation, wind has zero affect on aerodynamics.

Quote:
One of my buddies lost his FPV plane in windy weather 5 months ago, it was with the advanced OSD and auto return function but these did not help it return to the field after flying a long downwind leg.
Also, nothing to do with the debate.
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Old Jun 18, 2012, 12:09 PM
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As a full scale pilot you fly the traffic pattern by the numbers, i.e. power and pitch, not the ground speed. You do increase your landing airspeed by a percentage of the headwind but that is to give a safety factor for wind shear, change of wind direction. Other than turbulence bouncing you around the plane flies the same in calm or in wind.

When I fly my RC plane I fly the pattern at a certain throttle setting and pitch attitude, not by how fast the plane looks like it is moving. A little more power over the runway in case the wind dies down suddenly.
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Old Jun 18, 2012, 01:47 PM
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Probably you'd have to fly a high wing trainer upwind, cross wind and downwind to see how wind speed affects the lift on its wing.
I've been flying for quite a few years in all sorts of wind conditions. I'm pretty well acquainted with both the theory and the practice, thanks.

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And we all knew the difference between airspeed and ground speed, and how wind speed added up the airspeed when flying into upwind.
Wind DOES NOT AFFECT AIRSPEED. It doesn't add airspeed and it doesn't take away airspeed, no matter what direction you're flying relative to the wind. It ONLY affects groundspeed, which is the relative speed between the aircraft and the ground.
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Old Jun 18, 2012, 02:00 PM
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I've been flying for quite a few years in all sorts of wind conditions. I'm pretty well acquainted with both the theory and the practice, thanks.



Wind DOES NOT AFFECT AIRSPEED. It doesn't add airspeed and it doesn't take away airspeed, no matter what direction you're flying relative to the wind. It ONLY affects groundspeed, which is the relative speed between the aircraft and the ground.
We need a sticky on this, so the heretics can have something to read while we burn them
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Old Jun 18, 2012, 02:24 PM
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Probably you'd have to fly a high wing trainer upwind, cross wind and downwind to see how wind speed affects the lift on its wing. It's always windy here during winter and fall in Taiwan, I did teach many beginners flying high wing trainers over the recent two years. Surely we all experienced this fact. And we all knew the difference between airspeed and ground speed, and how wind speed added up the airspeed when flying into upwind. I did show them how to fly in upwinds and always stayed upwinds when it was very windy.

Chen
Do it with a sailplane and the lesson is crystal clear after one circuit....
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Old Jun 18, 2012, 03:55 PM
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I've been flying for quite a few years in all sorts of wind conditions. I'm pretty well acquainted with both the theory and the practice, thanks.



Wind DOES NOT AFFECT AIRSPEED. It doesn't add airspeed and it doesn't take away airspeed, no matter what direction you're flying relative to the wind. It ONLY affects groundspeed, which is the relative speed between the aircraft and the ground.
+1 In level un-accelerated flight power controls airspeed. The airplane doesn't care what the ground is doing, the plane is a part of the air mass the same as a boat on a river.
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Old Jun 18, 2012, 06:31 PM
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the plane is a part of the air mass the same as a boat on a river.
Except the boat also has air resistance to deal with, so I think a submarine might be a better analogy.

Just messin' with ya
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Old Jun 18, 2012, 07:01 PM
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Rudder vs Aileron and aileron wins 2 1! Stay tuned for more sports.....
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Old Jun 18, 2012, 07:46 PM
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I've been flying for quite a few years in all sorts of wind conditions. I'm pretty well acquainted with both the theory and the practice, thanks.

Wind DOES NOT AFFECT AIRSPEED. It doesn't add airspeed and it doesn't take away airspeed, no matter what direction you're flying relative to the wind. It ONLY affects groundspeed, which is the relative speed between the aircraft and the ground.
you and Gerry beat this dead horse on every post. But your selective application of aerodynamics miss a major point:
Wind is dynamic, it changes much more rapidly in speed and direction than the planes inertia will allow. This is the fundamental reason pilots accept the science, but find it contradicts actual experience. False analogies like "submarines in a river" are misleading as well. FS aircraft cruising at 2-3x stall and 10x windspeed are not the same as RC flying near MCA at 1x windspeed.

The FS pilots claim that draggy airframes feel this "kick in the pants" not just reasonable, it's common. The ONLY thing that allows a plane with constant thrust to gradually match the relative wind is the drag on the airframe. It is not instantaneous.

Consider this scenario:
a plane is flying into 20 knot wind with airspeed of 20. Wind stops. 1/10 sec later, what is the planes airspeed? ZERO.

reverse scenario:
Plane is flying through still air at 20kts. Sudden tailwind gust of 20kts. Airspeed 1/10 sec later? ZERO

How can you say wind did not effect airspeed in those cases? We aren't talking theoretical wind as some steady-state vector, but the actual, variable, invisible chaotic mess that RC planes fly in.
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Old Jun 18, 2012, 08:06 PM
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Do it with a sailplane and the lesson is crystal clear after one circuit....
Thanks, I've been flying motor glider since 2000, and I did fly slope glider for more than one year. I knew how to change glider's attitude to increase or decrease its airspeed.

Chen
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Old Jun 18, 2012, 08:44 PM
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Complete and utter rubbish I'm afraid. All you have done with your 'teaching' is pass on your own flawed thinking.
I did say earlier that I agree with your theory, but I'd like to teach beginners by telling them what they would experience practically, and let them know how to deal with winds. They all knew that upwinds will raise up the nose of their high wing trainers, and they all knew how to keep level in winds. This way or my flawed thingking made their lessons simpler and easier.

Chen
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