P-Effect
#51
Hi Scott,
You didn't get the point I was trying to make - it was a thought experiment - my bad !
A new thought experiment ;
Let us build a new model.
- A standard fuz crutch with decks added top and bottom.
- Wing and tail mounted but with the wing set a little -ve in incidence.
- Let's put the vertical stabiliser on the bottom (like a predator - but a single one)
What motor thrust set up do you think will be req'd so that will pull from s&l horizontal to vertical and track straight ??
Why ??
Brian
You didn't get the point I was trying to make - it was a thought experiment - my bad !
A new thought experiment ;
Let us build a new model.
- A standard fuz crutch with decks added top and bottom.
- Wing and tail mounted but with the wing set a little -ve in incidence.
- Let's put the vertical stabiliser on the bottom (like a predator - but a single one)
What motor thrust set up do you think will be req'd so that will pull from s&l horizontal to vertical and track straight ??
Why ??
Brian
Last edited by serious power; 08-25-2016 at 09:40 AM. Reason: typo
#52
Hi,
Scott, I think Jim's comment was sent my way.
Jim, when I read this my mind went to the 'nothing' scene where Luke wins with nothing and Kennedy said about the fight ' he kept coming at me with a whole lot of nothing '.
However you are most likely referring to the line ' what we have here is a failure to communicate '.
If so you were correct - as said already 'my bad'
' I'm shaken it Boss, I'm shaken it '
It also put me off hard boiled eggs for a long tome
Brian
Scott, I think Jim's comment was sent my way.
Jim, when I read this my mind went to the 'nothing' scene where Luke wins with nothing and Kennedy said about the fight ' he kept coming at me with a whole lot of nothing '.
However you are most likely referring to the line ' what we have here is a failure to communicate '.
If so you were correct - as said already 'my bad'
' I'm shaken it Boss, I'm shaken it '
It also put me off hard boiled eggs for a long tome
Brian
#53
Thread Starter
Hi,
Scott, I think Jim's comment was sent my way.
Jim, when I read this my mind went to the 'nothing' scene where Luke wins with nothing and Kennedy said about the fight ' he kept coming at me with a whole lot of nothing '.
However you are most likely referring to the line ' what we have here is a failure to communicate '.
If so you were correct - as said already 'my bad'
' I'm shaken it Boss, I'm shaken it '
It also put me off hard boiled eggs for a long tome
Brian
Scott, I think Jim's comment was sent my way.
Jim, when I read this my mind went to the 'nothing' scene where Luke wins with nothing and Kennedy said about the fight ' he kept coming at me with a whole lot of nothing '.
However you are most likely referring to the line ' what we have here is a failure to communicate '.
If so you were correct - as said already 'my bad'
' I'm shaken it Boss, I'm shaken it '
It also put me off hard boiled eggs for a long tome
Brian
Scott, If there is such a thing as P-factor and it causes the plane to veer to the left (the airplanes left) when you pull to vertical, and it veers to the left (the airplanes right) when you push from inverted to vertical what do you do to trim it so it goes straight in both cases, and if you can't achieve that, what rudder input will you use to correct it?
I'm sure some planes are worse than others and maybe it can't be detected on some. Gyroscopic precession and perhaps the thrust line settings could magically cancel out the P-effect but it would seem to me to be a case of luck.
Jim O
Last edited by OhD; 08-25-2016 at 01:57 PM.
#55
My Feedback: (4)
Yes, it was the line ' what we have here is a failure to communicate '.
Scott, If there is such a thing as P-factor and it causes the plane to veer to the left (the airplanes left) when you pull to vertical, and it veers to the left (the airplanes right) when you push from inverted to vertical what do you do to trim it so it goes straight in both cases, and if you can't achieve that, what rudder input will you use to correct it?
I'm sure some planes are worse than others and maybe it can't be detected on some. Gyroscopic precession and perhaps the thrust line settings could magically cancel out the P-effect but it would seem to me to be a case of luck.
Jim O
Scott, If there is such a thing as P-factor and it causes the plane to veer to the left (the airplanes left) when you pull to vertical, and it veers to the left (the airplanes right) when you push from inverted to vertical what do you do to trim it so it goes straight in both cases, and if you can't achieve that, what rudder input will you use to correct it?
I'm sure some planes are worse than others and maybe it can't be detected on some. Gyroscopic precession and perhaps the thrust line settings could magically cancel out the P-effect but it would seem to me to be a case of luck.
Jim O
P-factor, also known as asymmetric blade effect and asymmetric disc effect, is an aerodynamic phenomenon experienced by a moving propeller, that is responsible for the asymmetrical relocation of the propeller's center of thrust when an aircraft is at a high angle of attack.
P-factor - Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/P-factor
If the plane is veering the same direction, (relative to you), whether inverted or upright, then the wings aren't level to start with. It sounds like you may be flying with the inside wing down.
I'm sure some planes are worse than others and maybe it can't be detected on some. Gyroscopic precession and perhaps the thrust line settings could magically cancel out the P-effect but it would seem to me to be a case of luck.
No magic or luck involved. It's called trimming and flying with the wings level.
Last edited by drac1; 08-25-2016 at 02:47 PM.
#56
My Feedback: (4)
Hi Scott,
You didn't get the point I was trying to make - it was a thought experiment - my bad !
A new thought experiment ;
Let us build a new model.
- A standard fuz crutch with decks added top and bottom.
- Wing and tail mounted but with the wing set a little -ve in incidence.
- Let's put the vertical stabiliser on the bottom (like a predator - but a single one)
What motor thrust set up do you think will be req'd so that will pull from s&l horizontal to vertical and track straight ??
Why ??
Brian
You didn't get the point I was trying to make - it was a thought experiment - my bad !
A new thought experiment ;
Let us build a new model.
- A standard fuz crutch with decks added top and bottom.
- Wing and tail mounted but with the wing set a little -ve in incidence.
- Let's put the vertical stabiliser on the bottom (like a predator - but a single one)
What motor thrust set up do you think will be req'd so that will pull from s&l horizontal to vertical and track straight ??
Why ??
Brian
#57
My Feedback: (4)
P-factor, also known as asymmetric blade effect and asymmetric disc effect, is an aerodynamic phenomenon experienced by a moving propeller, that is responsible for the asymmetrical relocation of the propeller's center of thrust when an aircraft is at a high angle of attack.
[h=3]P-factor - Wikipedia, the free encyclopedia[/h]https://en.wikipedia.org/wiki/P-factor
#60
My Feedback: (29)
I'm leaning towards torque myself. We can trim the airplane for a certain spot along the torque curve but once we load the airplane and increase the power required to maintain speed the trim changes. On takeoff when we are climbing up the torque curve it is noticeable, when we power up and pull to vertical the load is increased and the trim changes. Granted the more we spread out this load the less pronounced the change is. Running a pylon airplane that weighs 6.5 lbs and has a YS 115 14x14 power combo requires a ton of right rudder and slow throttle application to keep straight on takeoff. Once up to full speed and constant torque loading it tracks straight through the course and through turns.
#61
Thread Starter
Test: What if the engine/motor rotated in the opposite direction? I seem to remember some old British engines did rotate opposite. Anyone confirm this?
Jim O
#62
Hi Jim,
I'm giving up on the theory and hypothetical here as it seems a little pointless.
On the more practical side I suggest you try adding some sub-fin for a test or two. With more sub-fin less right thrust should also be req'd. If you do let us know the outcome and if it works we can discuss why. The three S's come to mind
Also/alternately, though it is a single prop set up, try a flare on the rudder TE.
I believe the fin design on the Nuance is inadequate to begin with !!!!!!!
Brian
I'm giving up on the theory and hypothetical here as it seems a little pointless.
On the more practical side I suggest you try adding some sub-fin for a test or two. With more sub-fin less right thrust should also be req'd. If you do let us know the outcome and if it works we can discuss why. The three S's come to mind
Also/alternately, though it is a single prop set up, try a flare on the rudder TE.
I believe the fin design on the Nuance is inadequate to begin with !!!!!!!
Brian
#63
My Feedback: (29)
Jim, I understand how P effect is supposed to work, I just don't see how it applies to our models. Most pattern airplanes sit at rest maybe 15 degrees but the tail rises pretty darned quick. After the tail rises there is still rudder input required to the right. During flight our light models react to inputs very quickly and are flying quite fast for their size. As a result I tend to beleive that for the most part the airflow hitting the prop is almost always at 90 degrees to the prop disk. The only time I see this changing is during final approach to touch down. Even then unless there is a cross wind I don't hold rudder to the right during flare to counteract the P effect created from flying 10-15 degrees nose up from flight path. Granted at that point we are at very low power setting. Have a look at the first part of this video. You can clearly see rudder input on the take off roll. You can also see it being tapered off as the torque curve flattens out as speed builds
https://www.youtube.com/watch?v=GQTLS6l28fo
https://www.youtube.com/watch?v=GQTLS6l28fo
#64
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Slipstream swirl is a corkscrewing airflow that travels around the fuselage.
This airflow strikes the vertical stabilizer, increasing its AOA. The increase in AOA of the vertical stabilizer pulls the tail to the right and yaws the nose to the left.
This situation is more prevalent at high power settings and low airspeeds.
To compensate, right rudder is required.
#65
My Feedback: (4)
Slipstream swirl is a corkscrewing airflow that travels around the fuselage.
This airflow strikes the vertical stabilizer, increasing its AOA. The increase in AOA of the vertical stabilizer pulls the tail to the right and yaws the nose to the left.
This situation is more prevalent at high power settings and low airspeeds.
To compensate, right rudder is required.
As far as I am aware, it's never been proven to actually exist, just a theory. If you have evidence, feel free to share.
#66
Thread Starter
Slipstream swirl is a corkscrewing airflow that travels around the fuselage.
This airflow strikes the vertical stabilizer, increasing its AOA. The increase in AOA of the vertical stabilizer pulls the tail to the right and yaws the nose to the left.
This situation is more prevalent at high power settings and low airspeeds.
To compensate, right rudder is required.
Jim O
#67
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#69
My Feedback: (4)
You are probably right, the spiral slipstream has more influence than the P-effect during takeoff, but don't let Bryan Hebert hear you say that. He and his devotee's say it doesn't exist. I think what they really mean to say is that it doesn't affect our models. I believe it is the reason we add right thrust.
Jim O
Jim O
#71
I think the size of a pattern plane, spiral is too small of a force. Precession force is 90 deg after the input. Pull up with normal motor rotation and the precession force is to the right wing until stable again. Whole point to need nose rings on soft mounts.
#72
Join Date: Apr 2010
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I don't know if this is proof, but it looks to me like evidence. I corresponded with the pilot. The photo is from Joe Nall a few years ago. The prop did not touch the water, but the wheels did. What do you think made the spiral pattern in the spray aft of the tail?
Bill
#73
My Feedback: (4)
If you put streamers down the sides of the fuse, I bet they would blow straight back.
Also how could it spiral around the fuse when there is a big fence called a wing and the stab which would prevent it from spiraling anyway.
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#75
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Correct, not proof. If it was that easy to prove, the SSS advocates would be all over it in a flash.
If you put streamers down the sides of the fuse, I bet they would blow straight back.
Also how could it spiral around the fuse when there is a big fence called a wing and the stab which would prevent it from spiraling anyway.
If you put streamers down the sides of the fuse, I bet they would blow straight back.
Also how could it spiral around the fuse when there is a big fence called a wing and the stab which would prevent it from spiraling anyway.