Spiraling Slipstream OR Coriolis Force? You decide. . .
#4
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Surely you've seen Alex Voicu's thread: http://www.rcuniverse.com/forum/rc-p...alisation.html
Nope.
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#6
The OP video, I only watched the first one, part way at that, illustrates why the old time tufting visualization used short pieces of string as a more effective way to examine airflow. The tufts were cut short enough so that they didn't flutter. The long threads in the OP videos are in turbulence and so it is difficult to see exactly what is going on.
#7
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Keith,
Thanks for posting links to your videos.
I'm favorably impressed with their quality, would you please post a description of the equipment used, camera make & model, resolution and how its mounted.
J e r
Thanks for posting links to your videos.
I'm favorably impressed with their quality, would you please post a description of the equipment used, camera make & model, resolution and how its mounted.
J e r
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The OP video, I only watched the first one, part way at that, illustrates why the old time tufting visualization used short pieces of string as a more effective way to examine airflow. The tufts were cut short enough so that they didn't flutter. The long threads in the OP videos are in turbulence and so it is difficult to see exactly what is going on.
#10
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I used a RunCam2 mounted on top of the vertical stab with a small piece of sheet metal between the top and the rudder. I'll post a picture later of the actual installation.
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What surprised me, and now that I've had a few days to think about it - it shouldn't have, is the massive amount of turbulence caused by the canopy.
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The worst effect of all that turbulence is simply wasted energy. Energy that comes from your batteries or glow fuel. That's why modern airliners don't have canopies sticking up into the airstream . . . perhaps Boeing and Airbus possibly know something that our pattern plane designers don't?
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The second negative effect of all that turbulence is what it does to the control surfaces. All that turbulent (and thus randomized) air is hitting the vertical and horizontal stab, and is also affecting the rudder and elevator. Kinda like trying to steer a canoe down a whitewater rapids. However, you can see that the nose of the airplane doesn't hunt around at all, so I imagine that the top part of the vertical stab / rudder are still in smooth air and able to steer the airplane.
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So . . . . like wheel pants, what purpose does the canopy on a pattern airplane serve other than "It will look weird and you won't get good scores without it"?
#11
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I used a RunCam2 mounted on top of the vertical stab with a small piece of sheet metal between the top and the rudder. I'll post a picture later of the actual installation.
.
What surprised me, and now that I've had a few days to think about it - it shouldn't have, is the massive amount of turbulence caused by the canopy.
.
The worst effect of all that turbulence is simply wasted energy. Energy that comes from your batteries or glow fuel. That's why modern airliners don't have canopies sticking up into the airstream . . . perhaps Boeing and Airbus possibly know something that our pattern plane designers don't?
.
The second negative effect of all that turbulence is what it does to the control surfaces. All that turbulent (and thus randomized) air is hitting the vertical and horizontal stab, and is also affecting the rudder and elevator. Kinda like trying to steer a canoe down a whitewater rapids. However, you can see that the nose of the airplane doesn't hunt around at all, so I imagine that the top part of the vertical stab / rudder are still in smooth air and able to steer the airplane.
.
.
.
So . . . . like wheel pants, what purpose does the canopy on a pattern airplane serve other than "It will look weird and you won't get good scores without it"?
I used a RunCam2 mounted on top of the vertical stab with a small piece of sheet metal between the top and the rudder. I'll post a picture later of the actual installation.
.
What surprised me, and now that I've had a few days to think about it - it shouldn't have, is the massive amount of turbulence caused by the canopy.
.
The worst effect of all that turbulence is simply wasted energy. Energy that comes from your batteries or glow fuel. That's why modern airliners don't have canopies sticking up into the airstream . . . perhaps Boeing and Airbus possibly know something that our pattern plane designers don't?
.
The second negative effect of all that turbulence is what it does to the control surfaces. All that turbulent (and thus randomized) air is hitting the vertical and horizontal stab, and is also affecting the rudder and elevator. Kinda like trying to steer a canoe down a whitewater rapids. However, you can see that the nose of the airplane doesn't hunt around at all, so I imagine that the top part of the vertical stab / rudder are still in smooth air and able to steer the airplane.
.
.
.
So . . . . like wheel pants, what purpose does the canopy on a pattern airplane serve other than "It will look weird and you won't get good scores without it"?
#12
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Still, it doesn't make sense to basically have a drag chute attached to your plane 100% of the time just for knife edge.
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You could do the same thing more effectively with a vertical canard located over the CG.
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#13
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Keith,
I remember seeing pictures of a guy I think from Finland or Norway that flew a plane like that 2 or 3 years ago. If I find it I'll post a link.
Thanks for the RunCam2 info. Xavier Mouraux from Canada does something similar, https://www.youtube.com/watch?v=MUce24921kI
J e r
#17
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What surprised me, and now that I've had a few days to think about it - it shouldn't have, is the massive amount of turbulence caused by the canopy.
.
The worst effect of all that turbulence is simply wasted energy. Energy that comes from your batteries or glow fuel. That's why modern airliners don't have canopies sticking up into the airstream . . . perhaps Boeing and Airbus possibly know something that our pattern plane designers don't?
.
The second negative effect of all that turbulence is what it does to the control surfaces. All that turbulent (and thus randomized) air is hitting the vertical and horizontal stab, and is also affecting the rudder and elevator. Kinda like trying to steer a canoe down a whitewater rapids. However, you can see that the nose of the airplane doesn't hunt around at all, so I imagine that the top part of the vertical stab / rudder are still in smooth air and able to steer the airplane.
.
.
.
So . . . . like wheel pants, what purpose does the canopy on a pattern airplane serve other than "It will look weird and you won't get good scores without it"?
What surprised me, and now that I've had a few days to think about it - it shouldn't have, is the massive amount of turbulence caused by the canopy.
.
The worst effect of all that turbulence is simply wasted energy. Energy that comes from your batteries or glow fuel. That's why modern airliners don't have canopies sticking up into the airstream . . . perhaps Boeing and Airbus possibly know something that our pattern plane designers don't?
.
The second negative effect of all that turbulence is what it does to the control surfaces. All that turbulent (and thus randomized) air is hitting the vertical and horizontal stab, and is also affecting the rudder and elevator. Kinda like trying to steer a canoe down a whitewater rapids. However, you can see that the nose of the airplane doesn't hunt around at all, so I imagine that the top part of the vertical stab / rudder are still in smooth air and able to steer the airplane.
.
.
.
So . . . . like wheel pants, what purpose does the canopy on a pattern airplane serve other than "It will look weird and you won't get good scores without it"?
There's no massive turbulence caused by the canopy, unless the canopy is very poorly designed which is not the case for the Allure. I've seen jets designed to fly at Mach 2 with less streamlined canopies than those used on our pattern planes. If there's any turbulent flow, it's mostly caused by the spinning propeller and not by the canopy.
I think the tufts in the videos are way too long and may give you the wrong impression about the amount of turbulent airflow around the plane.
You can try moving the tufts elsewhere on the airframe and if you keep the same length i'm pretty sure you will get the same results. It doesn't mean the canopy or other parts are causing turbulence.
If the tufts are short, they will align themselves with the local airflow without shaking too much:
If there's any turbulent airflow, the tufts will show it even if they are cut short :
#18
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Even if the airflow is perfect, the canopy still presents unneeded frontal area that does nothing but increase induced drag.
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I've never seen anything functional installed in anyone's canopy . . . . ever.
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In a fighter jet, the pilot's head is installed inside the canopy, but our pattern planes . . . .
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I've never seen anything functional installed in anyone's canopy . . . . ever.
.
In a fighter jet, the pilot's head is installed inside the canopy, but our pattern planes . . . .
.
#19
Even if the airflow is perfect, the canopy still presents unneeded frontal area that does nothing but increase induced drag.
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I've never seen anything functional installed in anyone's canopy . . . . ever.
.
In a fighter jet, the pilot's head is installed inside the canopy, but our pattern planes . . . .
.
.
I've never seen anything functional installed in anyone's canopy . . . . ever.
.
In a fighter jet, the pilot's head is installed inside the canopy, but our pattern planes . . . .
.
I'm thinking we ADD drag in an attempt to slow them down. We have gone from thin ballistic Curares to slow flying Contra Allures with huge frontal area.
#20
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Also, note that the strings are frayed as well. That will amplify some of the disturbance. Another factor is the diameter of the yarn. You wind up measuring airflow too far away from the fuselage. That said, very impressed with the work. For the next round, I would suggest using flourescent fishing filament taped to the fuselage every 3-4 inches. That will give you a better indication of airflow. Though I have to say, I didn't see anything wrong with the airflow.... taking into account the fray and large length and diameter of the yearn. Very nice. Thanks for posting. I love the videos.. Nice flying too!!
Ken
Ken
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Good point. One thing I can think of as someone who has been attracted to models and miniatures of all kinds since a young age, is that the canopy adds that satisfying (and illusional) hint that if one were really small, one could crawl in that little airplane and ride around in it. It's for this reason (the wish for realism) that I find myself wishing for a pattern plane I could buy that has wing & stabilizer root fairings.
Even if the airflow is perfect, the canopy still presents unneeded frontal area that does nothing but increase induced drag.
.
I've never seen anything functional installed in anyone's canopy . . . . ever.
.
In a fighter jet, the pilot's head is installed inside the canopy, but our pattern planes . . . .
.
.
I've never seen anything functional installed in anyone's canopy . . . . ever.
.
In a fighter jet, the pilot's head is installed inside the canopy, but our pattern planes . . . .
.
#25
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Not bothered at all.
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I didn't really invest a lot of time or effort into this endeavor - some blue painter's tape and yarn. I was looking for what happens in general to the airflow around the fuse of my pattern plane. But mainly I was checking if I had the rudder trim set properly. Anyone who has flown a Cessna will recognize where I got the yarn idea from.
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After watching the videos, I noticed at low to medium airspeeds that the left string always curled up towards the top of the plane. However, it doesn't seem to have any effect on the tracking of the nose of the airplane. My guess is that the "spiraling slipstream" is there, but it only has a negligible effect on the airplane.
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As for jetmech . . . I know where to find him . . .
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