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Old Sep 05, 2012, 01:52 PM
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New Rochelle, NY
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Originally Posted by Logan4169 View Post
The need to hold roll through a banked turn.
No, the dihedral helps convert the yaw into roll. And that has nothing to do with the point that holding for bank is not how aileron control works.

-------------
Forces in a turn:

Why the rudder-to-turn method is not appropriate for normal turning: This cross-controlled technique is an ineffiecient use of energy and uncomfortable for everyday flying. The technique is actually used just before flare in a significant crosswind approach. For example consider a quartering headwind from the left. Then lower the left wing down as necessary to correct for drift to the right. Use opposite (right) rudder to align the longitudinal axis of the aircraft with the runway centerline. The pilot would smoothly change from a left crab angle on final to a left side-slip for crosswind correction closer to the ground.

Normal turns occur because the pilot uses aileron to raise one wing redirecting the force of lift into two vectors, one vertical and one horizontal. The horizonal component of lift actually pulls the plane around in the turn. The rudder is used to correct adverse yaw created by the induced drag happening on the rising wing. For example, in a left turn, the lowered right aileron increases wing curvature, increases lift production, and increases induced drag as a byproduct of lift. Thus, uncorrected, the nose will pull in the direction of the raised wing. Proper use of rudder will coordinate the rate of turn by balancing the hozizontal component of lift (in to the turn) with the centrifugal force (to the outside of the turn). The inclinometer or "ball" should be centered to be coordinated.

Bottom line - normal turns involve coordinated use of aileron and rudder in the desired direction of the turn.
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Old Sep 05, 2012, 02:24 PM
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Originally Posted by Logan4169 View Post
As long a you understand that there will be crashes, and are willing to pay the price in glue and parts then there is no reason that you can't. One bit of advice though, if it is headed toward something more valuable than the plane itself, then don't be afraid to put it in the dirt.
I second this. I went from owning 2 3CH planes and moved up to a 4Ch by way of a P51 Mustang. If cars or innocent bystanders are near this plane doesn't go in the air. My lack of skill along with the heart pounding flight is perfect time that I would have to do the above. It has already taken one face plant, and don't want to add another. 4 successes 1 Gorilla Glue bath.

I hear going back and forth on the 3 vs 4 channel debate as far as learning. Maybe some learn better on 3 and other may have no issues starting with 4. Both may be right depending on the person.

I am a new to the hobby and new to the forum.
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Old Sep 05, 2012, 02:28 PM
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Originally Posted by ny_hawk View Post
Ah, sorry missed it.



Right... So you must hold the stick over to maintain the turn... And on a 4 channel plane doing this will yield considerably different, and undesirable results for new pilots..

This is the key difference and a non-trivial one IMO.
It doesn't constitute much of a barrier to progression, from what I know about it.
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Old Sep 05, 2012, 02:38 PM
Arizona Fun
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Originally Posted by jasmine2501 View Post
Yeah lateral G-forces throwing your body out the windows. In a regular plane, we "center the ball" by using rudder and ailerons together, so that the passengers don't feel the rocking. If done correctly and with no visual reference point, you can do it such that the passengers don't even know you made a turn.

On my post before, it isn't that I think this is a bad question, it's that I'm confused why people post the question instead of just going and reading the answer, and I'm not the only one - I was responding to a similar query, so if you're going to jump down my throat about it, try to be equitable and spread the sh*t around instead of dumping it all on me. I'm going to continue to ask people about that behavior as long as I find it interesting, and if you don't like it, there is nothing wrong with ignoring me. Some of us are simply interested in human behavior. I don't think there's anything wrong with that.
Sorry if my input seemed at all harsh, I often wonder how much effort some posters put in before asking questions that seem fairly easy to find here or with a google search. I too am fascinated with human behavior and studied psychology for many years. With humans being social creatures, I think sometimes we just want to be part of a group and mingle even when we can sometimes find the answers ourselves.
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Old Sep 05, 2012, 02:41 PM
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ny_hawk You are aware that we are talking about RC model aircraft right? There is no comfort level to consider, and there is no inclinometer to keep centered.

The dihedral does in fact convert yaw to roll, which is what allows the rudder only banked turn that makes RET airplanes possible. On that much I hope that we can all agree. However, dihedral is also what causes the positive stability in the high wing trainers that we are talking about. The "self leveling" tendency as they call it. The dihedral causes that, and it doesn't matter if you initiated the roll with ailerons or rudder. That "self leveling" has to be countered by holding ailerons through the turn. Properly done it should include rudder also for a coordinated turn.
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Old Sep 05, 2012, 02:45 PM
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Originally Posted by Logan4169 View Post
You are aware that we are talking about RC model aircraft right? There is no comfort level to consider, and there is no inclinometer to keep centered.

The dihedral does in fact convert yaw to roll, which is what allows the rudder only banked turn that makes RET airplanes possible. On that much I hope that we can all agree. However, dihedral is also what causes the positive stability in the high wing trainers that we are talking about. The "self leveling" tendency as they call it. The dihedral causes that, and it doesn't matter if you initiated the roll with ailerons or rudder. That "self leveling" has to be countered by holding ailerons through the turn. Properly done it should include rudder also for a coordinated turn.
A proper coordinated turn is the same.

If you hold ailerons on a 4 channel plane it will roll over.. Whereas you must hold rudder through a turn on a 3 channel--why this is news is beyond me.. I trained on a 4 channel plane with dihedral and I did not have to hold ailerons through a turn.. No idea what you trained on.

There IS a difference and is why I recommend 4 ch trainers. Flying planes, esp trainers is not that hard, try flying CCPM helis...that's hard.
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Old Sep 05, 2012, 03:06 PM
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Originally Posted by ny_hawk View Post
A proper coordinated turn is the same.

If you hold ailerons on a 4 channel plane it will roll over.. Whereas you must hold rudder through a turn on a 3 channel--why this is news is beyond me.. I trained on a 4 channel plane with dihedral and I did not have to hold ailerons through a turn.. No idea what you trained on.

There IS a difference and is why I recommend 4 ch trainers. Flying planes, esp trainers is not that hard, try flying CCPM helis...that's hard.
The aircraft that you are describing here, with no roll correction, has "neutral stability." They will have little or no dihedral. Typically, they are considered a secondary sport plane, not a primary trainer.

I trained on a Raptor 30, so yes this airplane stuff is pretty easy.
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Old Sep 05, 2012, 03:45 PM
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Time for a diversion.

Here's a nice "high wing" plane...

F-14 Tomcat: Demonstration by Dale Snodgrass :: 1996 Cleveland National Air Show (7 min 36 sec)
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Old Sep 05, 2012, 04:19 PM
Which way is up?
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Chills and tingles, everytime I see something like that. Capt. Snodgrass is a bad ass mutha trucker!!!
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Old Sep 05, 2012, 04:24 PM
buyer of the farm
United States, FL, DeLand
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Originally Posted by ny_hawk View Post
No, the dihedral helps convert the yaw into roll. And that has nothing to do with the point that holding for bank is not how aileron control works.

-------------
Forces in a turn:

Why the rudder-to-turn method is not appropriate for normal turning: This cross-controlled technique is an ineffiecient use of energy and uncomfortable for everyday flying. The technique is actually used just before flare in a significant crosswind approach. For example consider a quartering headwind from the left. Then lower the left wing down as necessary to correct for drift to the right. Use opposite (right) rudder to align the longitudinal axis of the aircraft with the runway centerline. The pilot would smoothly change from a left crab angle on final to a left side-slip for crosswind correction closer to the ground.

Normal turns occur because the pilot uses aileron to raise one wing redirecting the force of lift into two vectors, one vertical and one horizontal. The horizonal component of lift actually pulls the plane around in the turn. The rudder is used to correct adverse yaw created by the induced drag happening on the rising wing. For example, in a left turn, the lowered right aileron increases wing curvature, increases lift production, and increases induced drag as a byproduct of lift. Thus, uncorrected, the nose will pull in the direction of the raised wing. Proper use of rudder will coordinate the rate of turn by balancing the hozizontal component of lift (in to the turn) with the centrifugal force (to the outside of the turn). The inclinometer or "ball" should be centered to be coordinated.

Bottom line - normal turns involve coordinated use of aileron and rudder in the desired direction of the turn.
Ya got it wrong again. Note in my last paragraph I say something important. In a 4-channel plane with enough stability to be roll stable, when you let go of the right stick, the plane resumes straight and level flight, just like a 3-channel plane, and I'm gonna be a broken record here, for exactly the same reasons.

There's no free lunch in aerodynamics. If you have dihedral you will have a self-stabilizing airplane whether it has ailerons or rudder, or a gerbil moves his weight around inside the plane to maneuver. There's nothing special about ailerons that somehow controls a plane better than a rudder. It is no more inefficient to control the plane one way than the other. It takes a given amount of torque to roll the plane and it matters not whether it comes from rudder, ailerons or something else entirely.

Actually one of the cooler planes I ever worked on was the ultralight Birdman RB1, which had neither rudder nor ailerons. It flew great using a popup spoiler just like a sailplane's but hooked up to the stick so only one was actuated at a time. Flew just as well as ailerons or rudder.

Now your illustration of crosswind landing isn't valid because those planes are not designed to bank with the rudder. Their airframes are set up so that about 90% of rudder force goes to yaw, maybe even more, and only 10% or so is roll vector. All you're doing with the rudder is yawing the fuselage parallel to the runway when the plane isn't flying that way. Then when the wheels touch you'll roll in line with the runway instead of off into the grass.

In a 3-channel plane you don't get that discreet yaw out of the rudder. Like I said, my Slow Stick would be about 50-50 yaw to roll. That means turns are automatically coordinated but I cannot do an uncoordinated turn as you can with an aileron plane. My roll and yaw are linked in a constant ratio.

The thing is that 3-channel planes and 4-channel planes respond in exactly the same way to control movements for the exact reasons, provided they are designed to be flown in the way you are flying. You can't fly a plane with no dihedral as a 3-channel plane unless you want to take the entire county to make a 360 turn. A 4-channel plane with the same dihedral as a 3-channel plane will be self stabilizing. When you release the aileron stick, the plane will straighten out exactly......you know what's coming.
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Old Sep 05, 2012, 04:35 PM
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Originally Posted by Rockin Robbins View Post
Ya got it wrong again. Note in my last paragraph I say something important. In a 4-channel plane with enough stability to be roll stable, when you let go of the right stick, the plane resumes straight and level flight, just like a 3-channel plane, and I'm gonna be a broken record here, for exactly the same reasons.

There's no free lunch in aerodynamics. If you have dihedral you will have a self-stabilizing airplane whether it has ailerons or rudder, or a gerbil moves his weight around inside the plane to maneuver. There's nothing special about ailerons that somehow controls a plane better than a rudder. It is no more inefficient to control the plane one way than the other. It takes a given amount of torque to roll the plane and it matters not whether it comes from rudder, ailerons or something else entirely.

Actually one of the cooler planes I ever worked on was the ultralight Birdman RB1, which had neither rudder nor ailerons. It flew great using a popup spoiler just like a sailplane's but hooked up to the stick so only one was actuated at a time. Flew just as well as ailerons or rudder.

Now your illustration of crosswind landing isn't valid because those planes are not designed to bank with the rudder. Their airframes are set up so that about 90% of rudder force goes to yaw, maybe even more, and only 10% or so is roll vector. All you're doing with the rudder is yawing the fuselage parallel to the runway when the plane isn't flying that way. Then when the wheels touch you'll roll in line with the runway instead of off into the grass.

In a 3-channel plane you don't get that discreet yaw out of the rudder. Like I said, my Slow Stick would be about 50-50 yaw to roll. That means turns are automatically coordinated but I cannot do an uncoordinated turn as you can with an aileron plane. My roll and yaw are linked in a constant ratio.

The thing is that 3-channel planes and 4-channel planes respond in exactly the same way to control movements for the exact reasons, provided they are designed to be flown in the way you are flying. You can't fly a plane with no dihedral as a 3-channel plane unless you want to take the entire county to make a 360 turn. A 4-channel plane with the same dihedral as a 3-channel plane will be self stabilizing. When you release the aileron stick, the plane will straighten out exactly......you know what's coming.
So you're saying that with a 4 channel trainer with dihedral you have to hold over the stick through the turn?
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Old Sep 05, 2012, 04:38 PM
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Real airplanes will require a noticable amount of aileron held into the turn until about 30 degrees of bank then at about 60 degrees it will require opposite to keep it from rolling. The greater the dihedral the more bank it can have and still try to right itself. Aileron equipt aircraft will generally require less dihedral so will have a more neutral tendency. A stable trainer even with ailerons will require some held in until about 45-60 degrees depending on the plane.
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Old Sep 05, 2012, 04:42 PM
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Originally Posted by ny_hawk View Post
So you're saying that with a 4 channel trainer with dihedral you have to hold over the stick through the turn?
YES, that sums it up nicely, thanks!
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Old Sep 05, 2012, 04:45 PM
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YES, that sums it up nicely, thanks!
I don't recall my trainer doing that.. Although it was long ago..

So if they are the same then why bother with a 3 channel?
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Old Sep 05, 2012, 04:50 PM
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Originally Posted by ny_hawk View Post
I don't recall my trainer doing that.. Although it was long ago..

So if they are the same then why bother with a 3 channel?
Because a 3ch plane will be more docile and much less likely, in the hands of an unaccompanied beginner, to end up in a very bad attitude close to the ground.
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