P-Effect
07-09-2016, 05:49 PM
#26
I just maidened my Caelus #2 today. It has a 22X12 carbon 2 blade prop. My competition plane (Caelus #1) has a 19.5X13 carbon 3 blade. Other than the props, they are identical in every way, from c/g to wing incidence. Both planes require working the rudder on up-lines. So...no difference as far as I can tell. BUT the 3 blade has a much more consistent speed envelope, both under power and off-power down-lines. Also, the 3 blade sounds much better.
07-12-2016, 08:57 AM
#27
Thread Starter
I just maidened my Caelus #2 today. It has a 22X12 carbon 2 blade prop. My competition plane (Caelus #1) has a 19.5X13 carbon 3 blade. Other than the props, they are identical in every way, from c/g to wing incidence. Both planes require working the rudder on up-lines. So...no difference as far as I can tell. BUT the 3 blade has a much more consistent speed envelope, both under power and off-power down-lines. Also, the 3 blade sounds much better.
Jim O
07-12-2016, 10:19 AM
#28
08-19-2016, 12:31 PM
#29
Thread Starter
Since I started this thread, I feel like I should add my conclusions. After putting in over 100 flights on my Nuance with a 2 bladed prop, I accept what I learned about 40 years ago and that is, when you pull (pitch) you need a little right rudder and when you push you need a little left rudder. I tried everything to trim that phenomenon out, even sealed the aileron gaps as Tony F suggested. I got so I was pretty automatic and was flying fairly well.
Humans are very adaptable. When I was about 12 years old I bent the fork on my bike and it always pulled to the left. I got used to it and when I rode someone else's bike I felt like his was pulling right. So you can do it. I remember Dave Wilson saying it is better to have a plane that always needs the same inputs than one that you need to watch to see which way it is going to veer.
The motor on the Nuance has been very noisy so I decided to take my Gaudius with its Contra out this past week. Wow, no rudder required during pushes and pulls. What a joy.
Conclusion: You can learn to fly a 2 bladed prop but it is a lot easier to perform the maneuver you picture in your mind with the Contra.
Jim O
Humans are very adaptable. When I was about 12 years old I bent the fork on my bike and it always pulled to the left. I got used to it and when I rode someone else's bike I felt like his was pulling right. So you can do it. I remember Dave Wilson saying it is better to have a plane that always needs the same inputs than one that you need to watch to see which way it is going to veer.
The motor on the Nuance has been very noisy so I decided to take my Gaudius with its Contra out this past week. Wow, no rudder required during pushes and pulls. What a joy.
Conclusion: You can learn to fly a 2 bladed prop but it is a lot easier to perform the maneuver you picture in your mind with the Contra.
Jim O
08-19-2016, 12:59 PM
#30
Since I started this thread, I feel like I should add my conclusions. After putting in over 100 flights on my Nuance with a 2 bladed prop, I accept what I learned about 40 years ago and that is, when you pull (pitch) you need a little right rudder and when you push you need a little left rudder. I tried everything to trim that phenomenon out, even sealed the aileron gaps as Tony F suggested. I got so I was pretty automatic and was flying fairly well.
Humans are very adaptable. When I was about 12 years old I bent the fork on my bike and it always pulled to the left. I got used to it and when I rode someone else's bike I felt like his was pulling right. So you can do it. I remember Dave Wilson saying it is better to have a plane that always needs the same inputs than one that you need to watch to see which way it is going to veer.
The motor on the Nuance has been very noisy so I decided to take my Gaudius with its Contra out this past week. Wow, no rudder required during pushes and pulls. What a joy.
Conclusion: You can learn to fly a 2 bladed prop but it is a lot easier to perform the maneuver you picture in your mind with the Contra.
Jim O
Humans are very adaptable. When I was about 12 years old I bent the fork on my bike and it always pulled to the left. I got used to it and when I rode someone else's bike I felt like his was pulling right. So you can do it. I remember Dave Wilson saying it is better to have a plane that always needs the same inputs than one that you need to watch to see which way it is going to veer.
The motor on the Nuance has been very noisy so I decided to take my Gaudius with its Contra out this past week. Wow, no rudder required during pushes and pulls. What a joy.
Conclusion: You can learn to fly a 2 bladed prop but it is a lot easier to perform the maneuver you picture in your mind with the Contra.
Jim O
I have only used 2 blade props and do not have to apply rudder during pulls and pushes.
08-19-2016, 04:09 PM
#31
Hi,
I think you misunderstand 'P' effect.
It is not about high angle of attack - it is about changing angle of attack - in all directions.
The faster the change in direction and the more power that is applied through a single propellar the more 'P' effect is experienced.
In pattern we are constantly changing direction in both pitch and yaw. P factor is in play.
Brian
I think you misunderstand 'P' effect.
It is not about high angle of attack - it is about changing angle of attack - in all directions.
The faster the change in direction and the more power that is applied through a single propellar the more 'P' effect is experienced.
In pattern we are constantly changing direction in both pitch and yaw. P factor is in play.
Brian
08-19-2016, 04:44 PM
#32
Hi,
I think you misunderstand 'P' effect.
It is not about high angle of attack - it is about changing angle of attack - in all directions.
The faster the change in direction and the more power that is applied through a single propellar the more 'P' effect is experienced.
In pattern we are constantly changing direction in both pitch and yaw. P factor is in play.
Brian
I think you misunderstand 'P' effect.
It is not about high angle of attack - it is about changing angle of attack - in all directions.
The faster the change in direction and the more power that is applied through a single propellar the more 'P' effect is experienced.
In pattern we are constantly changing direction in both pitch and yaw. P factor is in play.
Brian
It is about high AOA as well as changing the AOA and It's also about the AOA relative to the flight path.
P factor does have a greater affect with faster direction changes. Even though we change directions a lot in pattern, we do so gently and smoothly which will not have anywhere near the same effect as in 3D for eg. Push and pulls are performed while applying elevator and adding power smoothly, which doesn't really fit the criteria for P factor.
My opinion of course from my experience.
08-19-2016, 06:55 PM
#33
Thread Starter
I understand P factor, but my wording could have been better.
It is about high AOA as well as changing the AOA and It's also about the AOA relative to the flight path.
P factor does have a greater affect with faster direction changes. Even though we change directions a lot in pattern, we do so gently and smoothly which will not have anywhere near the same effect as in 3D for eg. Push and pulls are performed while applying elevator and adding power smoothly, which doesn't really fit the criteria for P factor.
My opinion of course from my experience.
It is about high AOA as well as changing the AOA and It's also about the AOA relative to the flight path.
P factor does have a greater affect with faster direction changes. Even though we change directions a lot in pattern, we do so gently and smoothly which will not have anywhere near the same effect as in 3D for eg. Push and pulls are performed while applying elevator and adding power smoothly, which doesn't really fit the criteria for P factor.
My opinion of course from my experience.
Jim O
08-19-2016, 07:39 PM
#35
Brian said "faster direction changes" which result in greater angle of attack because airplanes have a time constant. There is a lag between establishing an angle of attack and developing a force normal to the airplane. Cn/α in missile terminology. Pattern planes seem to have short time constants but they are still there.
Jim O
Jim O
Like I said, I don't need to apply rudder correction when pulling or pushing.
Going by what you have described, I still think it's a stab alignment issue.
08-23-2016, 06:09 PM
#36
My Feedback: (2)
I agree with Jim O. conclusion. I have done the mixing he mention for years in a single prop planes. There is not need when using the contra. I don't know how to explain the physics but for sure the plane tracks better during pulls and pushs when having the mix. The problem is that you won't know until you try it.
08-24-2016, 02:19 AM
#40
Hi Scott,
When I used YS I liked to set the right thrust so that the model came out of a radius, from horizontal s&l to vertical, in the vertical yaw wise.
Was always around 3 degrees maybe a little more back when the motors were smaller/less powerful.
With it set like that I'm sure the 'balloon was squeezed' some giving some side effects.
Of course the P schedules were mostly performed from upright and were simpler then also.
However when I went electric I found such a set up to have too many and too severe side effects so backed off some right thrust and used mixes to help.
I found the whole thing very very frustrating, as the balloon was squeezed either one way or the other.
I'm not sure why the difference, more prop and or more pitch on the E setup !!?? More gyroscopes on the YS (they oppose P effect) !!?? I gave up !!!!
So as soon as Brenner pop'd up here I made contact - went Contra and haven't looked back.
Brian
When I used YS I liked to set the right thrust so that the model came out of a radius, from horizontal s&l to vertical, in the vertical yaw wise.
Was always around 3 degrees maybe a little more back when the motors were smaller/less powerful.
With it set like that I'm sure the 'balloon was squeezed' some giving some side effects.
Of course the P schedules were mostly performed from upright and were simpler then also.
However when I went electric I found such a set up to have too many and too severe side effects so backed off some right thrust and used mixes to help.
I found the whole thing very very frustrating, as the balloon was squeezed either one way or the other.
I'm not sure why the difference, more prop and or more pitch on the E setup !!?? More gyroscopes on the YS (they oppose P effect) !!?? I gave up !!!!
So as soon as Brenner pop'd up here I made contact - went Contra and haven't looked back.
Brian
08-24-2016, 02:27 AM
#41
On my pattern planes, Osmoses, Axiomes, Accuracy and Amethyst, none of them require any rudder input in or out of an attitude change, so I agree with Scott, it is a different problem.
Jim, have you though about increasing the vertical stab area for test? I mean form the L.E. fabricate a balsa piece you can tape on the LE of the vertical stab and then fly test?
I could give you more answers between the props and the V Stab area.
Regards
Jim, have you though about increasing the vertical stab area for test? I mean form the L.E. fabricate a balsa piece you can tape on the LE of the vertical stab and then fly test?
I could give you more answers between the props and the V Stab area.
Regards
08-24-2016, 03:14 AM
#42
Hi Scott,
When I used YS I liked to set the right thrust so that the model came out of a radius, from horizontal s&l to vertical, in the vertical yaw wise.
Was always around 3 degrees maybe a little more back when the motors were smaller/less powerful.
With it set like that I'm sure the 'balloon was squeezed' some giving some side effects.
Of course the P schedules were mostly performed from upright and were simpler then also.
However when I went electric I found such a set up to have too many and too severe side effects so backed off some right thrust and used mixes to help.
I found the whole thing very very frustrating, as the balloon was squeezed either one way or the other.
I'm not sure why the difference, more prop and or more pitch on the E setup !!?? More gyroscopes on the YS (they oppose P effect) !!?? I gave up !!!!
So as soon as Brenner pop'd up here I made contact - went Contra and haven't looked back.
Brian
When I used YS I liked to set the right thrust so that the model came out of a radius, from horizontal s&l to vertical, in the vertical yaw wise.
Was always around 3 degrees maybe a little more back when the motors were smaller/less powerful.
With it set like that I'm sure the 'balloon was squeezed' some giving some side effects.
Of course the P schedules were mostly performed from upright and were simpler then also.
However when I went electric I found such a set up to have too many and too severe side effects so backed off some right thrust and used mixes to help.
I found the whole thing very very frustrating, as the balloon was squeezed either one way or the other.
I'm not sure why the difference, more prop and or more pitch on the E setup !!?? More gyroscopes on the YS (they oppose P effect) !!?? I gave up !!!!
So as soon as Brenner pop'd up here I made contact - went Contra and haven't looked back.
Brian
When I built my Valiant, I set the thrust to the nose of the model. Was running the 170cdi back then and it was very close. Going to the 175cdi and now the 185cdi, I've had to increase the right thrust, so most likely is pretty close to 3 deg. I've set my Xareltoo to 3 degrees, but hasn't flown yet.
The only time I've had problems when pulling or pushing, is when the stabs weren't set the same.
Not sure what you mean by "ballooning"?
I haven't got an electric, so can't really comment on what, if any differences there. But I think larger props and or pitch would affect it some. On the 185, I've actually reduced the pitch compared to what I used to run. Very happy with my set up now.
08-24-2016, 04:30 AM
#43
'Squeezing the balloon'
An expression - squeeze it in at one point and it will bulge out else where !!
Eg, A model with down thrust and right thrust ; When flying s&l inverted to a push to a vertical climb, it effectively has up thrust and left thrust. Btw it also has an inverted fin in that scenario !??
Brian
An expression - squeeze it in at one point and it will bulge out else where !!
Eg, A model with down thrust and right thrust ; When flying s&l inverted to a push to a vertical climb, it effectively has up thrust and left thrust. Btw it also has an inverted fin in that scenario !??
Brian
Last edited by serious power; 08-24-2016 at 04:37 AM.
08-24-2016, 01:51 PM
#44
'Squeezing the balloon'
An expression - squeeze it in at one point and it will bulge out else where !!
Eg, A model with down thrust and right thrust ; When flying s&l inverted to a push to a vertical climb, it effectively has up thrust and left thrust. Btw it also has an inverted fin in that scenario !??
Brian
An expression - squeeze it in at one point and it will bulge out else where !!
Eg, A model with down thrust and right thrust ; When flying s&l inverted to a push to a vertical climb, it effectively has up thrust and left thrust. Btw it also has an inverted fin in that scenario !??
Brian
I don't agree with the up and left thrust when inverted thing.
The top and right side of the plane, is still the top and right regardless of orientation. Thrust lines are still right and down. Inverted fin??
08-24-2016, 04:52 PM
#46
Right thrust is right thrust regardless of the planes orientation. Thrust lines are relative to the plane not the orientation.
Last edited by drac1; 08-24-2016 at 04:54 PM.
08-24-2016, 06:30 PM
#49
Think about this scenario.
If your plane is going vertical at the end of the box, with the underneath facing you and it is veering to the left as you see it, you have to reduce right thrust. You don't reduce left thrust.
Technically, by reducing right thrust, you are "increasing" left thrust.
Does that make sense?
If your plane is going vertical at the end of the box, with the underneath facing you and it is veering to the left as you see it, you have to reduce right thrust. You don't reduce left thrust.
Technically, by reducing right thrust, you are "increasing" left thrust.
Does that make sense?
08-24-2016, 11:34 PM
#50
Hi Jim,
Yes, reasonably familiar but it's been a while.
Great movie with both Newman and Kennedy being at their brilliant best.
Very funny also.
Brian
Yes, reasonably familiar but it's been a while.
Great movie with both Newman and Kennedy being at their brilliant best.
Very funny also.
Brian
Last edited by serious power; 08-25-2016 at 02:15 AM. Reason: typo