P-Effect
08-27-2016, 11:08 AM
#76
08-27-2016, 11:40 AM
#77
The image for the left side is mirrored so we can spot the differences easier:
When the power is off, the airflow seems perfectly symmetrical:
To confuse things further, the plane in the images above always pulls to the right during pulls and pushes. The vertical lines were perfectly straight but it always needed left rudder to correct the loop segments, proportional to the amount of elevator used. The deviation is pure yaw, no rolling is involved.
I tried everything: adjusting the incidences, wingtip weights, changing the elevator servos, adjusting the elevator throws, etc. None of these worked, so in the end i used an elevator to rudder point mix. It took a few flights to set the mix points properly, but i was very happy with the result.
Last edited by Alex Voicu; 08-27-2016 at 11:57 AM.
08-27-2016, 11:59 AM
#78
Theres no question that there exist an effect from what is possibly mistakenly called the spiralling airflow. From what I remember, it's more to do with the aircraft MOVING INTO some High/low pressure combination cause by the prop tip and it effecting the vertical fin. Another words, it wasn't the airflow spiralling down the fuselage, it's the fuselage (vertical fin) flying/moving into the area that the prop tip has vacated. Does that make sense???
08-27-2016, 12:00 PM
#79
Hi Alex,
I remember you doing this.
A thought I had at the time was ;
It would be interesting to mount the tufts on little stand offs to get away from surface effects and boundary layer effects, say 50mm !!?
Then also to mount some larger stand offs so as to get the tufts out where you would really expect to see evidence of the spiral, say at 150mm !!?
Brian
I remember you doing this.
A thought I had at the time was ;
It would be interesting to mount the tufts on little stand offs to get away from surface effects and boundary layer effects, say 50mm !!?
Then also to mount some larger stand offs so as to get the tufts out where you would really expect to see evidence of the spiral, say at 150mm !!?
Brian
08-27-2016, 12:21 PM
#80
Hi Brian,
Yes it would be nice to get a more complete image of the airflow around the model. Anyway, at that time i was more focused on improving knife edge performance and less interested in the spiral slipstream debate.
Mounting stand offs for each tuft would be a lot of work though, but maybe i'll add a few someday.
Yes it would be nice to get a more complete image of the airflow around the model. Anyway, at that time i was more focused on improving knife edge performance and less interested in the spiral slipstream debate.
Mounting stand offs for each tuft would be a lot of work though, but maybe i'll add a few someday.
08-27-2016, 02:19 PM
#83
The tests i made back in 2013 show some differences between the left and right side airflow patterns in the wing area, when power is applied.
The image for the left side is mirrored so we can spot the differences easier:
When the power is off, the airflow seems perfectly symmetrical:
To confuse things further, the plane in the images above always pulls to the right during pulls and pushes. The vertical lines were perfectly straight but it always needed left rudder to correct the loop segments, proportional to the amount of elevator used. The deviation is pure yaw, no rolling is involved.
I tried everything: adjusting the incidences, wingtip weights, changing the elevator servos, adjusting the elevator throws, etc. None of these worked, so in the end i used an elevator to rudder point mix. It took a few flights to set the mix points properly, but i was very happy with the result.
The image for the left side is mirrored so we can spot the differences easier:
When the power is off, the airflow seems perfectly symmetrical:
To confuse things further, the plane in the images above always pulls to the right during pulls and pushes. The vertical lines were perfectly straight but it always needed left rudder to correct the loop segments, proportional to the amount of elevator used. The deviation is pure yaw, no rolling is involved.
I tried everything: adjusting the incidences, wingtip weights, changing the elevator servos, adjusting the elevator throws, etc. None of these worked, so in the end i used an elevator to rudder point mix. It took a few flights to set the mix points properly, but i was very happy with the result.
It's interesting that a few are having to add rudder during pulls and pushes. Might be an electric thing.
08-27-2016, 02:48 PM
#84
08-27-2016, 03:02 PM
#85
I don't believe in evolution either. Again, it's just a theory, with no "real" proof. If some want to believe they are monkey's, well that's up to them
.It's amazing what some will believe, so they can tell themselves they have solved a problem or something unexplainable.
The better question is - If evolution is true, then why have the monkeys stopped evolving?
08-27-2016, 03:35 PM
#86
Hey Brian,
I don't believe in evolution either. Again, it's just a theory, with no "real" proof. If some want to believe they are monkey's, well that's up to them.
It's amazing what some will believe, so they can tell themselves they have solved a problem or something unexplainable.
The better question is - If evolution is true, then why have the monkeys stopped evolving?
I don't believe in evolution either. Again, it's just a theory, with no "real" proof. If some want to believe they are monkey's, well that's up to them
.It's amazing what some will believe, so they can tell themselves they have solved a problem or something unexplainable.
The better question is - If evolution is true, then why have the monkeys stopped evolving?
Scott,
Just as I thought.
Brian
PS ; Sorry Jim - back to your model .
08-27-2016, 05:46 PM
#87
A tail dragger is at high angle of attack on the runway during takeoff until it rotates (tail lifts off). It is really the angle between the prop shaft and the flight path that causes P-effect. Hold a prop horizontal and look at it in what would be a top view and then rotate it to simulate a nose up. You will see the pitch of the blade on the right increases and the one on the left decreases with respect to the horizontal. This couple causes a pull to the left and requires right rudder.
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
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
The Zlin 526 series of planes had the engine rotating "opposite" of what we are used to. I remember an article talking about applying left rudder on takeoff.
Ken
08-27-2016, 09:43 PM
#88
Thread Starter
Here is one thing I remember from 50 years ago. We used to stand over our planes in front of the stab and run the engine up before each flight.
My left shoe was always covered with oil and the right wasn't.
Jim O
08-27-2016, 11:49 PM
#89
This is amazing. I was thinking along the same lines, but I was going to suggest Scott didn't believe in God.
Here is one thing I remember from 50 years ago. We used to stand over our planes in front of the stab and run the engine up before each flight.
My left shoe was always covered with oil and the right wasn't.
Jim O
Here is one thing I remember from 50 years ago. We used to stand over our planes in front of the stab and run the engine up before each flight.
My left shoe was always covered with oil and the right wasn't.
Jim O
You know what they say about memory.
Last edited by drac1; 08-28-2016 at 12:05 AM.
08-28-2016, 12:52 AM
#90
08-28-2016, 01:20 AM
#92
Scott,
Let's move on - back to the good (interesting to some anyway) discussion on how to get a model with a single prop to track well and or why it does or doesn't !!
Brian
Let's move on - back to the good (interesting to some anyway) discussion on how to get a model with a single prop to track well and or why it does or doesn't !!
Brian
