Piper Cub aerodynamics question
02-08-2010 | 12:39 PM
#1
Thread Starter
Senior Member
Joined: Oct 2006
Posts: 714
Likes: 0
Received 0 Likes
on
0 Posts
From: Amadora, PORTUGAL
Piper Cub aerodynamics question
I'm a bit of a novice flying airplanes, mainly due to little time to practice.
This saturday, I went to the field for a flight and took my Kyosho Cub 50 so my instructor would maiden it. All went smooth.
When he handed me the tranny, he mentioned I shouldn't aileron bank in turns past a certain amount or the wing would slip the airplane into the turn with no correction possible to save it from crashing.
Could you someone explain this to me?
Thank you [8D]
This saturday, I went to the field for a flight and took my Kyosho Cub 50 so my instructor would maiden it. All went smooth.
When he handed me the tranny, he mentioned I shouldn't aileron bank in turns past a certain amount or the wing would slip the airplane into the turn with no correction possible to save it from crashing.
Could you someone explain this to me?
Thank you [8D]
02-08-2010 | 01:03 PM
#2
RE: Piper Cub aerodynamics question
Well I think you need to find an instructor who knows how to add rudder in his turn. He knows that a full scale cub will have adverse yaw caused by the flat bottom wing and large ailerons, but a model may have differantial aileron which automatically corrects for that. But even if it isn't then it's OK to add rudder in the turn to prevent this.
02-08-2010 | 11:00 PM
#3
RE: Piper Cub aerodynamics question
Patxipt,
When you say that “he mentioned I shouldn't aileron bank in turns past a certain amount”, I understand that you should input aileron only for enough time to bank the wings and then return the stick to the neutral point.
Once the wings are banked, the model will start turning because part of the lift force produced by the wings will point to the center of the horizontal circle that the model will follow.
The bigger the bank of the wings, the smaller that circle described by the turn will be.
The problem is that the lift force produced by the wings is now divided between the vertical component that keeps the model floating and the force that is mentioned above.
For that reason, the model that starts a turn will start descending at the same time.
In order to avoid that, and to keep the turn at the same level, elevator up needs to be input.
If the natural loss of altitude created by the bank of the wing is not compensated by the elevator, and the aileron input is kept for too long (“past a certain amount”), the model will roll and descend continuously, steeper, tighter and faster into a spiral dive.
With sufficient altitude, the model can be saved, stopping the roll and fall with the proper controls.
The slip that your instructor mentioned is a sideways movement of the model relative to the airflow (it does not follow the circle of the turn), in which the nose of the model points towards the centre of the turn.
A proper level turn requires the use of ailerons, elevator and rudder, each in the proper amount.
Such turn is known as coordinated turn, which is better explained in this link:
http://en.wikipedia.org/wiki/Coordinated_flight
Regards
When you say that “he mentioned I shouldn't aileron bank in turns past a certain amount”, I understand that you should input aileron only for enough time to bank the wings and then return the stick to the neutral point.
Once the wings are banked, the model will start turning because part of the lift force produced by the wings will point to the center of the horizontal circle that the model will follow.
The bigger the bank of the wings, the smaller that circle described by the turn will be.
The problem is that the lift force produced by the wings is now divided between the vertical component that keeps the model floating and the force that is mentioned above.
For that reason, the model that starts a turn will start descending at the same time.
In order to avoid that, and to keep the turn at the same level, elevator up needs to be input.
If the natural loss of altitude created by the bank of the wing is not compensated by the elevator, and the aileron input is kept for too long (“past a certain amount”), the model will roll and descend continuously, steeper, tighter and faster into a spiral dive.
With sufficient altitude, the model can be saved, stopping the roll and fall with the proper controls.
The slip that your instructor mentioned is a sideways movement of the model relative to the airflow (it does not follow the circle of the turn), in which the nose of the model points towards the centre of the turn.
A proper level turn requires the use of ailerons, elevator and rudder, each in the proper amount.
Such turn is known as coordinated turn, which is better explained in this link:
http://en.wikipedia.org/wiki/Coordinated_flight
Regards
02-08-2010 | 11:44 PM
#4
Senior Member
RE: Piper Cub aerodynamics question
A proper Cub will show lots of adverse yaw when turning, which is usually handled by adding rudder to push the nose around.
Insufficient dihedral is the cause.
If your Kyosho Cub has this, then yes, it will need rudder with the turn.
It's a "feature" (in the Microsoft vein) that adds to the enjoyment of flying.. in the full-scale, the pilot needs to push on the rudder too!
Most models are set up better, so that the ailerons do the turning, and the rudder (or, as it is never used, it's just the vertical surface) is just there to keep the pointy end at the front.
I expect your instructor doesn't have that much experience with that many different configurations.
Insufficient dihedral is the cause.
If your Kyosho Cub has this, then yes, it will need rudder with the turn.
It's a "feature" (in the Microsoft vein) that adds to the enjoyment of flying.. in the full-scale, the pilot needs to push on the rudder too!
Most models are set up better, so that the ailerons do the turning, and the rudder (or, as it is never used, it's just the vertical surface) is just there to keep the pointy end at the front.
I expect your instructor doesn't have that much experience with that many different configurations.
02-09-2010 | 04:54 AM
#5
Thread Starter
Senior Member
Joined: Oct 2006
Posts: 714
Likes: 0
Received 0 Likes
on
0 Posts
From: Amadora, PORTUGAL
RE: Piper Cub aerodynamics question
ORIGINAL: LNEWQBAN
Patxipt,
When you say that “he mentioned I shouldn't aileron bank in turns past a certain amount”, I understand that you should input aileron only for enough time to bank the wings and then return the stick to the neutral point.
Once the wings are banked, the model will start turning because part of the lift force produced by the wings will point to the center of the horizontal circle that the model will follow.
The bigger the bank of the wings, the smaller that circle described by the turn will be.
The problem is that the lift force produced by the wings is now divided between the vertical component that keeps the model floating and the force that is mentioned above.
For that reason, the model that starts a turn will start descending at the same time.
In order to avoid that, and to keep the turn at the same level, elevator up needs to be input.
If the natural loss of altitude created by the bank of the wing is not compensated by the elevator, and the aileron input is kept for too long (“past a certain amount”), the model will roll and descend continuously, steeper, tighter and faster into a spiral dive.
With sufficient altitude, the model can be saved, stopping the roll and fall with the proper controls.
The slip that your instructor mentioned is a sideways movement of the model relative to the airflow (it does not follow the circle of the turn), in which the nose of the model points towards the centre of the turn.
A proper level turn requires the use of ailerons, elevator and rudder, each in the proper amount.
Such turn is known as coordinated turn, which is better explained in this link:
http://en.wikipedia.org/wiki/Coordinated_flight
Regards
Patxipt,
When you say that “he mentioned I shouldn't aileron bank in turns past a certain amount”, I understand that you should input aileron only for enough time to bank the wings and then return the stick to the neutral point.
Once the wings are banked, the model will start turning because part of the lift force produced by the wings will point to the center of the horizontal circle that the model will follow.
The bigger the bank of the wings, the smaller that circle described by the turn will be.
The problem is that the lift force produced by the wings is now divided between the vertical component that keeps the model floating and the force that is mentioned above.
For that reason, the model that starts a turn will start descending at the same time.
In order to avoid that, and to keep the turn at the same level, elevator up needs to be input.
If the natural loss of altitude created by the bank of the wing is not compensated by the elevator, and the aileron input is kept for too long (“past a certain amount”), the model will roll and descend continuously, steeper, tighter and faster into a spiral dive.
With sufficient altitude, the model can be saved, stopping the roll and fall with the proper controls.
The slip that your instructor mentioned is a sideways movement of the model relative to the airflow (it does not follow the circle of the turn), in which the nose of the model points towards the centre of the turn.
A proper level turn requires the use of ailerons, elevator and rudder, each in the proper amount.
Such turn is known as coordinated turn, which is better explained in this link:
http://en.wikipedia.org/wiki/Coordinated_flight
Regards
Yes I am aware of the need to use elevator to stop the airplane from descending. I didn't notice any signs of adverse yaw, it tracked like a trainer, but perhaps that's what he mentioned.
From what I remember, even using rudder during the turn he told me not to pass, what I could guess from the plane's attittude, around 40Âş of banking and holding it no more than that during a turn.
Now I'm tempeted to get it really high and try it out...
ORIGINAL: Tall Paul
A proper Cub will show lots of adverse yaw when turning, which is usually handled by adding rudder to push the nose around.
Insufficient dihedral is the cause.
If your Kyosho Cub has this, then yes, it will need rudder with the turn.
It's a "feature" (in the Microsoft vein) that adds to the enjoyment of flying.. in the full-scale, the pilot needs to push on the rudder too!
Most models are set up better, so that the ailerons do the turning, and the rudder (or, as it is never used, it's just the vertical surface) is just there to keep the pointy end at the front.
I expect your instructor doesn't have that much experience with that many different configurations.
A proper Cub will show lots of adverse yaw when turning, which is usually handled by adding rudder to push the nose around.
Insufficient dihedral is the cause.
If your Kyosho Cub has this, then yes, it will need rudder with the turn.
It's a "feature" (in the Microsoft vein) that adds to the enjoyment of flying.. in the full-scale, the pilot needs to push on the rudder too!
Most models are set up better, so that the ailerons do the turning, and the rudder (or, as it is never used, it's just the vertical surface) is just there to keep the pointy end at the front.
I expect your instructor doesn't have that much experience with that many different configurations.
Actually my instructor is one of the best around, with many many years of experience.[&:]
I'm just trying to make sense of what he had mentioned with the several types of airplane characteristics (wing drop, adverse yaw, spin, etc).
Thanks
02-09-2010 | 06:20 AM
#6
Senior Member
RE: Piper Cub aerodynamics question
If he is a very experienced pilot, he might have been simply describing what he saw your turns needed. And that usually depends on how your model is trimmed and what warps it might have and how well the engine was running and what the wind was doing to the model's path as seen from a fixed point on the ground and the inclination of the solar system.................
If you'd really like to make some sense of his advice, then check it out by watching him fly that plane of yours through a couple of turns. Very often very experienced pilots forget what they're actually doing with the sticks. OK, in fact they aren't forgetting, they don't think about it at all. So watch how he moves the sticks a couple of times. Upwind and downwind turns.
Did what he told you to do work?
Also, start using the rudder NOW. Get used to using it while you're learning because it's easier to learn now than later, when you've learned to do everything without it.
If you'd really like to make some sense of his advice, then check it out by watching him fly that plane of yours through a couple of turns. Very often very experienced pilots forget what they're actually doing with the sticks. OK, in fact they aren't forgetting, they don't think about it at all. So watch how he moves the sticks a couple of times. Upwind and downwind turns.
Did what he told you to do work?
Also, start using the rudder NOW. Get used to using it while you're learning because it's easier to learn now than later, when you've learned to do everything without it.
02-09-2010 | 09:30 AM
#7
Thread Starter
Senior Member
Joined: Oct 2006
Posts: 714
Likes: 0
Received 0 Likes
on
0 Posts
From: Amadora, PORTUGAL
RE: Piper Cub aerodynamics question
If he is a very experienced pilot, he might have been simply describing what he saw your turns needed. And that usually depends on how your model is trimmed and what warps it might have and how well the engine was running and what the wind was doing to the model's path as seen from a fixed point on the ground and the inclination of the solar system.................
If you'd really like to make some sense of his advice, then check it out by watching him fly that plane of yours through a couple of turns. Very often very experienced pilots forget what they're actually doing with the sticks. OK, in fact they aren't forgetting, they don't think about it at all. So watch how he moves the sticks a couple of times. Upwind and downwind turns.
Did what he told you to do work?
Also, start using the rudder NOW. Get used to using it while you're learning because it's easier to learn now than later, when you've learned to do everything without it.
If you'd really like to make some sense of his advice, then check it out by watching him fly that plane of yours through a couple of turns. Very often very experienced pilots forget what they're actually doing with the sticks. OK, in fact they aren't forgetting, they don't think about it at all. So watch how he moves the sticks a couple of times. Upwind and downwind turns.
Did what he told you to do work?
Also, start using the rudder NOW. Get used to using it while you're learning because it's easier to learn now than later, when you've learned to do everything without it.
The Cub turned better with coordinated controls, so maybe he was really mentioning adverse yaw.
Thank you all for your help.
02-09-2010 | 09:07 PM
#8
RE: Piper Cub aerodynamics question
What you felt with the Cub model isn't always what the real one flies like. In fact I'd say that it's seldom what the real one flies like. Our models react differently from the real ones due to a number of factors. Designers often alter things on the model and we tend to run with different balance points, our models have less weight to move around so they don't model the inertial parameters of the real ones faithfully at all and finally the air is constant but our models are smaller so it treats the models differently from the big ones.
So when he suggests you do something "because it will......." it is only that model that will do that. Other models will react differently. Even another Cub of the same size but with different mods or other factors will react differently.
So when he suggests you do something "because it will......." it is only that model that will do that. Other models will react differently. Even another Cub of the same size but with different mods or other factors will react differently.
